Experimental Investigation on Shear Strength Parameters of Lime Stabilized Loess

Round 1

Reviewer 1 Report

Dear Authors, the following aspects need your attention:

Title

The title does not include a reference to the power function equation developed to characterize the lime treated loess soil. Change or complete the title to better represent the work developed (as this aspect is an advantage – reduction of cost and time associated with performing triaxial tests).

Abstract

It is recommended to add at the end of the abstract: a) that the results obtained in the triaxial tests as well as those obtained by applying the proposed equation were compared; b) the main conclusions that can be drawn from this comparison. 47 triaxial speciments? (28?) Clarify.

Keywords

The keyword “Loess soil” should be included to clearly identify the scope of the study. I also recommend removing the last keyword (Mohr-Coulomb), which is repeated, and organizing the keywords according to the structure of the article.

 

Introduction It is strongly recommended to include in the introduction previous studies carried out in loess soils using triaxial tests, clarifying whether or not the approach presented has already been partially addressed/or not addressed by other authors. This is a very important aspect to consider.

Page 2, lines 61-70:

“To evaluate the influence of the lime content and porosity on the tensile and compressive strength numerous researches STUDIES were performed by Consoli et al. [34-36] on lime stabilized soil, and the results indicated that an increase in lime content caused a linear growth in the tensile and the compressive strength, while the porosity showed the opposite trend. In addition, the void/lime ratio adjusted by a power coefficient had been demonstrated to be an accurate parameter to assess the tensile and compressive strength of the lime stabilized soil. However, there are no existing failure criteria to explain them explicitly (CLARIFY IN THE TEXT WHAT THE AUTHORS MEAN BY THIS). So far, the Coulomb criterion is generally used to establish a failure envelope for the stabilized soil with a specific amount of stabilization agent and porosity. However, this process needs of triaxial compression tests to be carried out, and many other complicated and time-consuming tests [37-39].” INCLUDE WHAT OTHER TYPES OF TESTS ARE REQUIRED.

Page 2, line 76:

“…also established, as shown in the following equation: c=0.225qc+50 (in kPa).” INCLUDE QUOTE.

Page 2, lines 81-82:

“…However, their ratio is independent of the above factors and tends to a constant value, and the ratio value is linked to the friction angle of the treated soil.” CLARIFY IN THE TEXT WHAT RATIO ARE YOU REFERRING TO.

Page 2, lines 87-91- objectives of the research:

Improve presentation of the study objectives. Suggestions: It should be clearly stated that the results of the triaxial tests are also intended to be used to develop a power function equation that allows to obtain the lime treated loess soil cohesion as a function of parameters that can be obtained through simpler, less costly and time consuming tests. Clearly state the innovation of the study.

 

Materials and experimental

Section 2.2 and 2.4:

Consider moving the content from section 2.2 to section 2.4 (it makes more sense) and include information on the amount of water, soil and lime considered in the prepared specimens, the total number of specimens and the cure temperature.

Section 2.3:

Page 4, line 122-123:

“Standard compaction test is generally performed to determine the maximum dry density, the optimum moisture content, and to achieve the target in-situ degree of compaction [48].” THIS SENTENCE NEEDS NO QUOTATION AS IT IS A GENERAL KNOWLEDGE FINDING FOR THOSE WORKING IN THIS AREA OF KNOWLEDGE.

Page 5, Table 3:

Consider adding a column with porosity values in table 3.

Other comments:

Clarify in the text that the compaction tests allowed to obtain the dry density and water content to be considered in the specimens tested in the triaxial test. Why were not included in the text typical values of loess soil for dry density, water content (and also angle of internal friction and cohesion) or a non-lime treated control specimen to allow comparison with the values obtained in the study? It is important to include this aspect. Clarify in the text why the molding point D was chosen specifically to investigate the effect of lime content on the strength behaviour (with a dry density of 1.48g/cm³ and different lime percentages)?

Was this procedure and the one used to investigate the effect of porosity based on studies/approaches performed by other researchers?

Section 2.4:

Clarify in the text the type of triaxial test performed (consolidated-drained).

 

Results and Discussion

Section 3.1:

Following the interpretation of results presented in lines 179- 186 (pages 6 and 7), also comment the maximum values of q versus ε_a (%). It is recommended to present the mean, mode, median and standard deviation of the results obtained for the angle of internal friction, since they allow a better support for the interpretation of results (table 4), conclusion and adoption of a value to consider when applying the developed power function equation (in section 3.2).

Page 8, line 200:

Do you mean Table 5 instead of Figure 4?

Page 8, Figure 4:

Adopt the same order of tested specimens presentation used in Figure 3 (improves comparison of results).

Page 9, lines 211-213:

“After curing for 180 days, the most of specimens have been pressured into piece when they were taken out of the rubber film, and thus the angle between the between the shear failure plane and the major principal plane could not be measured.” THIS INFORMATION IS REPEATED IN THE TEXT SO IT CAN BE DELETED IN ONE OF THE PLACES WHERE IT IS DISPLAYED.

Page 8-9, Table 5:

Try to put the entire table on the same page. It is also recommended to include a small statistical analysis (as recommended for the values obtained for the angle of internal friction). This basic statistical analysis can help explain why the 45°+ φ/2 calculation for the values obtained is closer to 63° than 68° (angle of shear plane).

Section 3.2:

Page 9, Figure 5:

Do not start the section with Figure 5. Place the figure after the first paragraph of this section. Check and comment on R² value obtained for 7 days of curing (0.221). In the figure 5 caption is missing the letter "D": “Effect of lime content and curing time on the c of SPECIMENS at molding point D”.

Page 10, lines 242-244:

“…Therefore, it was possible to establish a relation between the cohesion of lime stabilized loess and the ratio of voids volume to lime volume (V_V/V_Li). A similar improvement by adding a power (ς) was also considered.” IT IS NECESSARY TO INCLUDE IN THE TEXT AN EXPLANATION OF HOW THESE POWERS CAN BE OBTAINED. THIS ASPECT IS NOT CLEARLY ADDRESSED IN THE TEXT, SO IT IS NOT POSSIBLE TO UNDERSTAND HOW THE POWERS PRESENTED IN FIGURE 7 WERE OBTAINED (0.11, 0.17, 0.35 AND 1.15). This is an important aspect of this study and must be properly presented and justified.

Page 12, lines 281-284:

“Therefore, the use of voids of compacted mixture divided by the volumetric lime content, adjusted by a power (the variation of this power is mainly controlled by the curing time) to assess the cohesion c in the lime OF THE LOESS SOIL TREATED WITH LIME?, further in view of loess studied is herein sufficiently accurate for all considered curing times.” IMPROVE SENTENCE.

Page 12, line 289:

Include the reason for having adopted an angle of internal friction of 37.5º and not another value from the range 36.5º to 38º.

Pages 13-14, Figure 10:

Try to put the entire table on the same page. Please comment on the angle of internal friction and cohesion values (percentage difference) obtained from the Mohr-Coulomb failure envelopes obtained from triaxial test results and equation (9) (including the adopted angle of internal friction = 37.5º).

The cohesion values obtained applying equation (9) are different from the ones obtained from the triaxial test results. For the cases shown in Figure 10, this variation ranges from approximately -19% to +3%, and therefore needs interpretation. This is an important aspect that should be commented and include in the manuscript. Suggestion for future work: to statistically validate the similarity of values obtained based on triaxial test and equation (9).

 

Conclusion

Page 14, lines 309-311:

Also refer in this sentence to curing time and porosity.

Page 14, lines 321-323:

Consider including the type of regression adopted.

Page 14, lines 327-328:

“(6) The Mohr-Coulomb failure envelopes OBTAINED WITH EQUATION (9) provided a good representation of the tangent to the Mohr semicircles drawn based on triaxial test of studied lime stabilized loess.” WHAT ARE THE AUTHORS BASED ON TO STATE THAT IT IS “A GOOD REPRESENTATION OF THE TANGENT TO THE MOHR SEMICIRCLES DRAWN BASED ON TRIAXIAL TEST OF STUDIED LIME STABILIZED LOESS”. SEE COMMENT IN SECTION 3.2.

The conclusions can be explained in a more detailed and understandable manner. The manuscript lacks a clear explanation of how the results can be used for base and sub-base road pavement design and solution decision making.

 

References

Consider diversifying bibliographic references and include studies related to triaxial testing in loess soils. 10 references to the same author (Consoli, N. C.) out of 51 references is too much. Consider change this aspect.

Author Response

Response to Reviewer 1 Comments

Point 1: Title

The title does not include a reference to the power function equation developed to characterize the lime treated loess soil. Change or complete the title to better represent the work developed (as this aspect is an advantage – reduction of cost and time associated with performing triaxial tests).

Response 1: The authors appreciate the reviewer’s comment. According to the reviewer’s suggestion, the title has been changed to “Experimental investigation on shear strength parameters of lime stabilized loess”.

 

Point 2: Abstract

It is recommended to add at the end of the abstract: a) that the results obtained in the triaxial tests as well as those obtained by applying the proposed equation were compared; b) the main conclusions that can be drawn from this comparison. 47 triaxial speciments? (28?) Clarify. 

Response 2: According to the reviewer’s suggestion, the sentences “that the results obtained in the triaxial tests as well as those obtained by applying the proposed equation were compared” and “the main conclusions that can be drawn from this comparison” have been added at the end of the abstract.

The specimens that drawn the Mohr-Coulomb failure envelopes have different dry density and lime content and are therefore more representative, including specimens of molding points B for 7 days of curing, molding points B for 28 days of curing, molding points B for 90 days of curing, molding points B for 180 days of curing, molding points A for 90 days of curing and molding points C for 90 days of curing. Among them, seven confining pressures were applied to the specimens 7 days of curing, and eight confining pressures were applied to the others.

 

Point 3: Keywords

The keyword “Loess soil” should be included to clearly identify the scope of the study. I also recommend removing the last keyword (Mohr-Coulomb), which is repeated, and organizing the keywords according to the structure of the article.

 Response 3: According to the reviewer’s suggestion, the last keyword “Mohr-Coulomb” has been removed, and “Loess soil” has been added as the second keyword.

 

Point 4: Introduction

 It is strongly recommended to include in the introduction previous studies carried out in loess soils using triaxial tests, clarifying whether or not the approach presented has already been partially addressed/or not addressed by other authors. This is a very important aspect to consider.

 Response 4: Thanks for the comments. A comprehensive review of the literature indicates that an extensive amount of triaxial tests related to the loess have been carried out worldwide for the past several decades, and the researches mainly focused on the mechanical behavior and failure characteristics of loess. The approach presented has not yet been addressed by other authors.  

 

Point 5: Page 2, lines 61-70:

“To evaluate the influence of the lime content and porosity on the tensile and compressive strength numerous researches STUDIES were performed by Consoli et al. [34-36] on lime stabilized soil, and the results indicated that an increase in lime content caused a linear growth in the tensile and the compressive strength, while the porosity showed the opposite trend. In addition, the void/lime ratio adjusted by a power coefficient had been demonstrated to be an accurate parameter to assess the tensile and compressive strength of the lime stabilized soil. However, there are no existing failure criteria to explain them explicitly (CLARIFY IN THE TEXT WHAT THE AUTHORS MEAN BY THIS). So far, the Coulomb criterion is generally used to establish a failure envelope for the stabilized soil with a specific amount of stabilization agent and porosity. However, this process needs of triaxial compression tests to be carried out, and many other complicated and time-consuming tests [37-39].” INCLUDE WHAT OTHER TYPES OF TESTS ARE REQUIRED.

Response 5: According to the reviewer’s suggestion, “researches” has been changed to “studies”.

Thanks for the comments. The authors have re-read the relevant literatures and removed the sentence “However, there are no existing failure criteria to explain them explicitly” and revised the sentences “However, this process needs of triaxial compression tests to be carried out, and many other complicated and time-consuming tests” as follows: However, determination of Mohr-Coulomb failure envelope parameters of stabilized soils requires carrying out triaxial test or Direct shear test, which are complex and time-consuming.

 

Point 6: Page 2, line 76:

“…also established, as shown in the following equation: c=0.225q_c+50 (in kPa).” INCLUDE QUOTE.

 Response 6: According to the reviewer’s suggestion, the referenced literature has been added, as follow: “36.Mitchell, J. K. Soil improvement-state-of-the-art report. In Proc. 10th Int. Conf. on Soil Mechanics and Foundation Engineering, International Society of Soil Mechanics and Foundation Engineering, Stockholm, Sweden, 1981; pp 509-565.”

 

Point 7: Page 2, lines 81-82:

“…However, their ratio is independent of the above factors and tends to a constant value, and the ratio value is linked to the friction angle of the treated soil.”  IN THE TEXT WHAT RATIO ARE YOU REFERRING TO.

Response 7: Thanks for the comments, “their ratio” means “the ratio of unconfined compressive strength to splitting tensile strength”. The authors have clarified in the text.

 

Point 8: Page 2, lines 87-91- objectives of the research:

Improve presentation of the study objectives. Suggestions: It should be clearly stated that the results of the triaxial tests are also intended to be used to develop a power function equation that allows to obtain the lime treated loess soil cohesion as a function of parameters that can be obtained through simpler, less costly and time consuming tests. Clearly state the innovation of the study.

Response 8: The authors appreciate the reviewer’s comment. According to the reviewer’s suggestion, the study objectives has been improved, as follow: “The present research aimed to establish the functional relationship between the Mohr–Coulomb failure envelope parameters (e.g. c and φ) obtained by conducting a series of triaxial tests, and the content of lime, the porosity and the curing age of lime stabilized loess. Based on the functional relationship, the Mohr–Coulomb failure envelope parameters of lime stabilized loess were obtained by conducting simpler, less costly and time-consuming tests (such as density test and specific gravity test) and calculation process, without the need for complicated time-consuming triaxial tests, thus making it more cost and time efficient.”

 

Point 9: Materials and experimental

Section 2.2 and 2.4:

Consider moving the content from section 2.2 to section 2.4 (it makes more sense) and include information on the amount of water, soil and lime considered in the prepared specimens, the total number of specimens and the cure temperature.

Response 9: Thanks for the comments. According to the reviewer’s suggestion, the content section 2.2 has been moved to section 2.4. The information on the amount of water, soil and lime considered in the prepared specimens is listed in Table 3. 

Point 10: Section 2.3:

Page 4, line 122-123:

“Standard compaction test is generally performed to determine the maximum dry density, the optimum moisture content, and to achieve the target in-situ degree of compaction [48].” THIS SENTENCE NEEDS NO QUOTATION AS IT IS A GENERAL KNOWLEDGE FINDING FOR THOSE WORKING IN THIS AREA OF KNOWLEDGE.

Response 10: Thanks for the comments. The quoted reference has been removed.

 

Point 11: Page 5, Table 3:

Consider adding a column with porosity values in Table 3.

Response 11: According to the reviewer’s suggestion, the porosity values have been added in Table 3.

 

Point 12: Clarify in the text that the compaction tests allowed to obtain the dry density and water content to be considered in the specimens tested in the triaxial test. Why were not included in the text typical values of loess soil for dry density, water content (and also angle of internal friction and cohesion) or a non-lime treated control specimen to allow comparison with the values obtained in the study? It is important to include this aspect. Clarify in the text why the molding point D was chosen specifically to investigate the effect of lime content on the strength behaviour (with a dry density of 1.48g/cm³and different lime percentages)?

Was this procedure and the one used to investigate the effect of porosity based on studies/approaches performed by other researchers?

Response 12: Thanks for the comments. It is a pity that I have not done values measurement of loess soil for dry density, water content (and also angle of internal friction and cohesion) or a non-lime treated control specimen, but I will make further improvement in the follow-up research.

In this paper, the effect of lime content and porosity on cohesion of stabilized loess is studied by orthogonal method. The specimens at point C, D, E have the same lime content (23%) but different dry density (the difference vaule in dry density is 0.1g/cm³). The specimens at point D have the dry density but different lime content (10%, 16%, 23%), which can eliminate the interference of the dry density on the results in investigating the effect of lime content on the cohesion. Specimens at points C and D can also be fabricated with the above three different lime contents to investigate the effect of lime content on cohesion. In order to reduce the unnecessary workload, the D point is selected.

This procedure and the one used to investigate the effect of porosity were based on the approaches performed by Consoli et al. (Reference cited: 34. Consoli, N. C.; Lopes, L. d. S., Jr.; Heineck, K. S., Key Parameters for the Strength Control of Lime Stabilized Soils. Journal of Materials in Civil Engineering 2009, 21, (5), 210-216.)

 

Point 13: Section 2.4:

Clarify in the text the type of triaxial test performed (consolidated-drained).

Response 13: The type of triaxial test performed has been clarified in the text, as follow: The static consolidated drained triaxial tests were conducted to obtain the failure envelope parameters of lime stabilized loess samples in accordance with ASTM D7181.

 

Point 14: Results and Discussion

Section 3.1:

Following the interpretation of results presented in lines 179- 186 (pages 6 and 7), also comment the maximum values of q versus εa (%). It is recommended to present the mean, mode, median and standard deviation of the results obtained for the angle of internal friction, since they allow a better support for the interpretation of results (table 4), conclusion and adoption of a value to consider when applying the developed power function equation (in section 3.2).

Response 14: Thanks for the comments. The authors have commented the maximum values of q versus εa, as follow: the critical value of the transition from the plastic phase to the failure phase when the specimen is under pressure.
According to the reviewer’s suggestion, the mean, median and standard deviation of the results obtained for the angle of internal friction have been presented in the text, which were 37.25, 37.25 and 0.37, respectively. In addition, the authors added Figure 4 in the text, which shows Effect of lime content and dry density on angle of internal friction of speicmens at all molding points with all curing time, as follow,
Figure 4. Effect of lime content and dry density on angle of internal friction of speicmens at all molding points with all curing time
“Figure 4 shows the angle of internal friction of specimens with 10 to 23% lime contents and 1.38 to 1.71g/cm3dry density and cured for 7 days, 28days, 90days and 180days, respectively, it can be readily seen that no correlation can be observed between the angle of internal friction and lime content or dry density of lime stabilize loess specimens for all curing time.”

 

Point 15: Page 8, line 200:

Do you mean Table 5 instead of Figure 4?

Response 15: Thanks for the comments. The meaning of this sentence is not clearly expressed, The author has revised this sentence, as follows: In order to further verify the reliability of the above test results, the shear failure angle between the shear failure plane and the major principal plane was determined for each specimen, and the shear failure plane was marked with a red lines, as shown in Figure 5.

 

Point 16: Page 8, Figure 4:

Adopt the same order of tested specimens presentation used in Figure 3 (improves comparison of results).

 Response 16: Thanks for the comments. The authors have adjusted the order of tested specimens presentation used in original Figure 4. The details of the revision are shown in Figure 5.

 

Point 17: Page 9, lines 211-213:

“After curing for 180 days, the most of specimens have been pressured into piece when they were taken out of the rubber film, and thus the angle between the between the shear failure plane and the major principal plane could not be measured.” THIS INFORMATION IS REPEATED IN THE TEXT SO IT CAN BE DELETED IN ONE OF THE PLACES WHERE IT IS DISPLAYED.

Response 17: According to the reviewer’s suggestion, the sentence “the specimens of 180 days of curing had been crushed to pieces during the test due to high brittleness”has been deleted.

 

Point 18: Page 8-9, Table 5:

Try to put the entire table on the same page. It is also recommended to include a small statistical analysis (as recommended for the values obtained for the angle of internal friction). This basic statistical analysis can help explain why the 45°+ φ/2 calculation for the values obtained is closer to 63° than 68° (angle of shear plane).

Response 18: Thanks for the comments. The location of the table will be adjusted during the “final proof-reading” period.

According to the reviewer’s suggestion, the authors made a statistical analysis of the values in Table 5, as follows: “Combining with the measured shear failure angles, the estimated values of φ varied from 36° to 46°, the mean and median of which were 41.5° and 42°,respectively, and the percentage difference of mean and median of the angle of internal friction obtained by this two approaches were 11.4% and 12.8%, respectively. It can be seen that the φ calculated from the shear failure angle is quite close to the measured values from the triaxial compression test.”

 

Point 19: Section 3.2:

Page 9, Figure 5:

Do not start the section with Figure 5. Place the figure after the first paragraph of this section. Check and comment on R² value obtained for 7 days of curing (0.221). In the figure 5 caption is missing the letter "D": “Effect of lime content and curing time on the c of SPECIMENS at molding point D”.

Response 19: Thanks for the comments. According to the reviewer’s suggestion, the authors have adjusted the location of original Figure 5.

The strength growth of lime stabilized loess is a relatively long process. In the early stage of curing, the effect of lime content on the cohesion is not very obvious. The increase in lime content did not cause a linearly increase on the cohesion, as explained in the text: “For 7 days of curing regime, the cohesion c of lime stabilized loess increased up to a lime content of 16%, but then showed a slightly decreasing trend when the lime content was 23%”, which led to a lower R² value (0.221). With the increase of curing age, the effect of lime content on cohesion is more obvious, and strength increases approximately linearly with the increase in the lime content.

The letter "D" has been added in caption of the original Figure 5.

 

Point 20: Page 10, lines 242-244:

“…Therefore, it was possible to establish a relation between the cohesion of lime stabilized loess and the ratio of voids volume to lime volume (VV/VLi). A similar improvement by adding a power (ς) was also considered.” IT IS NECESSARY TO INCLUDE IN THE TEXT AN EXPLANATION OF HOW THESE POWERS CAN BE OBTAINED. THIS ASPECT IS NOT CLEARLY ADDRESSED IN THE TEXT, SO IT IS NOT POSSIBLE TO UNDERSTAND HOW THE POWERS PRESENTED IN FIGURE 7 WERE OBTAINED (0.11, 0.17, 0.35 AND 1.15). This is an important aspect of this study and must be properly presented and justified.

 Response 20: Thank you very much for your advice. The approach of the power has been explained in the text, as follow: “The Solving process of the power is very tedious. During the process, amounts of different values were used as the power (ς), and then regression fitting is performed by “original” software to obtain different correlation coefficients (R²). The value corresponding to the maximum correlation coefficient is selected as the power.”

 

Point 21: Page 12, lines 281-284:

“Therefore, the use of voids of compacted mixture divided by the volumetric lime content, adjusted by a power (the variation of this power is mainly controlled by the curing time) to assess the cohesion c in the lime OF THE LOESS SOIL TREATED WITH LIME?, further in view of loess studied is herein sufficiently accurate for all considered curing times.” IMPROVE SENTENCE.

Response 21: Thanks for the comments. The authors have improved the sentence, as follow: “Therefore, the use of voids of compacted mixture divided by the volumetric lime content, adjusted by a power (the variation of this power is mainly controlled by the curing time) to assess the cohesion c in the lime stabilized loess studied is herein sufficiently accurate for all considered curing times.”

 

Point 22: Page 12, line 289:

Include the reason for having adopted an angle of internal friction of 37.5º and not another value from the range 36.5º to 38º.

Response 22: Thank you very much for your advice. The authors have changed the angle of internal friction of 37.5ºto the value from the range 36.5º to 38º. The details of revision are shown in Figure 11.

 

Point 23: Pages 13-14, Figure 10:

Try to put the entire table on the same page. Please comment on the angle of internal friction and cohesion values (percentage difference) obtained from the Mohr-Coulomb failure envelopes obtained from triaxial test results and equation (9) (including the adopted angle of internal friction = 37.5º).

The cohesion values obtained applying equation (9) are different from the ones obtained from the triaxial test results. For the cases shown in Figure 10, this variation ranges from approximately -19% to +3%, and therefore needs interpretation. This is an important aspect that should be commented and include in the manuscript. Suggestion for future work: to statistically validate the similarity of values obtained based on triaxial test and equation (9).

 Response 23: Thanks for the comments. The location of the table will be adjusted during the “final proof-reading” period.

The authors have statistically validated the similarity of values obtained based on triaxial test and equation (9) in the text, as follow: “The comparative analysis was conducted to the cohesion values obtained by applying equation (9) and the ones obtained from the triaxial test results for 28 groups of specimens studied. The results indicated that the percentage difference between the cohesion values obtained by the above two approaches ranged from -19% to 19.7% for 25 groups of specimens, and percentage difference was greater than 20% for other 3 groups of specimens, which were -22.9%, 34.9% and 35.9%.”

 

Point 24: Conclusion

Page 14, lines 309-311:

Also refer in this sentence to and porosity.

Response 24: Thanks for the comments. “Curing time” and “porosity” have been added in the sentence, as follow: “Loess collected from Lanzhou city in northwest China was stabilized with different lime content, porosity and curing time, and its Mohr-Coulomb failure envelope parameters were investigated based on triaxial compression test. The study offered following conclusions:”

 

Point 25:  Page 14, lines 321-323:

Consider including the type of regression adopted.

Response 25:  The authors appreciate the reviewer’s comment. The type of regression adopted has added in the conclusion, as follow, “The relationship between lime content, void ratio, curing time and cohesion was established using the power function fitting regression of experimental data.”

Point 26: Page 14, lines 327-328:

“(6) The Mohr-Coulomb failure envelopes OBTAINED WITH EQUATION (9) provided a good representation of the tangent to the Mohr semicircles drawn based on triaxial test of studied lime stabilized loess.” WHAT ARE THE AUTHORS BASED ON TO STATE THAT IT IS “A GOODREPRESENTATION OF THE TANGENT TO THE MOHR SEMICIRCLES DRAWN BASED ON TRIAXIAL TEST OF STUDIED LIME STABILIZED LOESS”. SEE COMMENT IN SECTION 3.2.

Response 26: Thank you very much for your advice. According to the reviewer’s suggestion, the authors adjusted the value of φ, which ranges from 36.5° to 38°, as shown in Figure 11. Moreover, the similarity of cohesion values obtained based on triaxial test and Equation (9) have been statistically validated in the text. Therefore, with the increase of confining pressure, the Mohr-Coulomb failure envelopes obtained from the triaxial test results will finally change within a region, which is bounded by two envelops obtained by applying equation (9) and φ ranged from 36.5° to 38°.

 

Point 27: The conclusions can be explained in a more detailed and understandable manner. The manuscript lacks a clear explanation of how the results can be used for base and sub-base road pavement design and solution decision making. 

Response 27: Thank you very much for your advice. The explanation of how the results can be used for base and sub-base road pavement design and solution decision making has been presented in the text, as follow: “In base and sub-base road pavement design， the engineer can choose the lime content, the compaction effort and curing time appropriate to provide a mixture that meets the strength required by the project at the optimum cost. Moreover, once a poor compaction has been identified, it can be readily taken into account in the design, through the methodology proposed in this study, and adopting corrective measures accordingly such as the reinforcement of the treated layer by increasing the amount of lime or extending the curing time.”

 

Point 28: Consider diversifying bibliographic references and include studies related to triaxial testing in loess soils. 10 references to the same author (Consoli, N. C.) out of 51 references is too much. Consider change this aspect.

Response 28: According to the reviewer’s suggestion, the author has adjusted the cited literatures of Consoli, N. C. and deleted the following references:

35.Consoli, N. C.; da Silva Lopes Jr, L.; Heineck, K. S. Variables controlling stiffness and strength of lime-stabilized soils. Journal of Geotechnical and Geoenvironmental Engineering 2010, 137, (6), 628-632.

36. Consoli, N. C.; Dalla Rosa Johann, A.; Gauer, E. A.; Dos Santos, V. R.; Moretto, R. L.; Corte, M. B. Key parameters for tensile and compressive strength of silt-lime mixtures. Geotechnique Letters 2012, 2, 81-85.

38.Consoli, N. C.; da Silva Lopes Jr, L.; Consoli, B. S.; Festugato, L. Mohr-Coulomb failure envelopes of lime-treated soils. Geotechnique 2014, 64, (2), 165-170.

39. Wang, Y.; Guo, P.; Li, X.; Lin, H.; Liu, Y.; Yuan, H. Behavior of Fiber-Reinforced and Lime-Stabilized Clayey Soil in Triaxial Tests. Applied Sciences 2019, 9, (5), 900.

43.Consoli, N. C.; da Rocha, C. G.; Silvani, C. Devising dosages for soil-fly ash-lime blends based on tensile strength controlling equations. Construction and Building Materials 2014, 55, 238-245.

 

Author Response File: Author Response.pdf

Reviewer 2 Report

Dear Authors,

I have carefully read your manuscript. If the Editor decides otherwise, the article should be corrected.

I suggest to improve the following point:

There are some missing spaces in the text. Authors are suggested to look at the text once again .

The discussion of the results should be improved. In this version, the authors only describe the obtained results without trying to explain them based on literature data.

Improve the conclusions. The conclusions should be a summary of the obtained results. They should not be a repetition of what is in the results section.

Author Response

Response to Reviewer 2 Comments

Point 1: There are some missing spaces in the text. Authors are suggested to look at the text once again .

Response 1:Thanks for the comments. This issue will be adjusted during the “final proof-reading” period. 

 

Point 2: The discussion of the results should be improved. In this version, the authors only describe the obtained results without trying to explain them based on literature data.

Improve the conclusions. The conclusions should be a summary of the obtained results. They should not be a repetition of what is in the results section.

Response 2:The authors appreciate the reviewer’s comment on this. The authors have explained the obtained results based on literature data, as follow:

“In section 3.1:

 According to Mohr-Coulomb theory, the shear failure angle has a good relation with the angle of internal friction φ, which is known as (45°+ φ/2). Combining with the measured shear failure angles, the estimated values of φ varied from 36° to 46°, the mean and median of which were 41.5° and 42°,respectively, and the percentage difference of mean and median of the angle of internal friction obtained by this two approaches were 11.4% and 12.8%, respectively. It can be seen that the φ calculated from the shear failure angle is quite close to the measured values from the triaxial compression test.

In section 3.2:

The comparative analysis was conducted to the cohesion values obtained by applying equation (9) and the ones obtained from the triaxial test results for 28 groups of specimens studied. The results indicated that the percentage difference between the cohesion values obtained by the above two approaches ranged from -19% to 19.7% for 25 groups of specimens, and percentage difference was greater than 20% for other 3 groups of specimens, which were -22.9%, 34.9% and 35.9%.”

The authors have improved the conclusions, as follow:

“(1) the change in the amount of lime, porosity and curing time not present an obvious effect on the angle of internal friction for a given lime stabilized loess.

(2) The effect of lime content on cohesion is discussed based on experimental data. Furthermore, a linear relationship was observed between the cohesion and lime content for lime stabilized loess with different curing age.”

 

Author Response File: Author Response.pdf

Reviewer 3 Report

Reviewer likes the findings of this paper and its presentation. The following corrections/comments must be addressed to improve the quality of the paper.

Comment 1: It is recommended to use the same scale on x/y axis for Figure 3.

Comment 2: Page 9 of 17, line 212: Please remove “between the”.

Author Response

Response to Reviewer 3 Comments

Point 1: Comment 1: It is recommended to use the same scale on x/y axis for Figure 3.

Response 1: Thanks for the comments. Using the same scale on x/y axis for Figure 3 will make the picture look uncoordinated and unesthetic.

 

Point 2: Comment 2: Page 9 of 17, line 212: Please remove “between the”.

Response 2: Thanks for the comments. “Between the” has been removed in revision Page 10, line 252.

Author Response File: Author Response.pdf

Round 2

Reviewer 1 Report

Please see the comments 2nd revision.

Response to Reviewer 1 Comments

Point 1: Title

The title does not include a reference to the power function equation developed to characterize the lime treated loess soil. Change or complete the title to better represent the work developed (as this aspect is an advantage – reduction of cost and time associated with performing triaxial tests).

Response 1: The authors appreciate the reviewer’s comment. According to the reviewer’s suggestion, the title has been changed to “Experimental investigation on shear strength parameters of lime stabilized loess”.

 

Point 2: Abstract

It is recommended to add at the end of the abstract: a) that the results obtained in the triaxial tests as well as those obtained by applying the proposed equation were compared; b) the main conclusions that can be drawn from this comparison. 47 triaxial speciments? (28?) Clarify. 

Response 2: According to the reviewer’s suggestion, the sentences “that the results obtained in the triaxial tests as well as those obtained by applying the proposed equation were compared” and “the main conclusions that can be drawn from this comparison” have been added at the end of the abstract.

The specimens that drawn the Mohr-Coulomb failure envelopes have different dry density and lime content and are therefore more representative, including specimens of molding points B for 7 days of curing, molding points B for 28 days of curing, molding points B for 90 days of curing, molding points B for 180 days of curing, molding points A for 90 days of curing and molding points C for 90 days of curing. Among them, seven confining pressures were applied to the specimens 7 days of curing, and eight confining pressures were applied to the others.

2^nd revision:

Improve sentence “Finally, the Mohr-Coulomb failure envelopes were drawn for 47 triaxial specimens considering 7, 28, 90, and 180 days curing time and confining pressures varying from 50 to 500 kPa that the results obtained in the triaxial tests as well as those obtained by applying the proposed equation were compared, and the main conclusions can be drawn from this comparison.”

 

Point 3: Keywords

The keyword “Loess soil” should be included to clearly identify the scope of the study. I also recommend removing the last keyword (Mohr-Coulomb), which is repeated, and organizing the keywords according to the structure of the article.

 Response 3: According to the reviewer’s suggestion, the last keyword “Mohr-Coulomb” has been removed, and “Loess soil” has been added as the second keyword.

 

Point 4: Introduction

 It is strongly recommended to include in the introduction previous studies carried out in loess soils using triaxial tests, clarifying whether or not the approach presented has already been partially addressed/or not addressed by other authors. This is a very important aspect to consider.

 Response 4: Thanks for the comments. A comprehensive review of the literature indicates that an extensive amount of triaxial tests related to the loess have been carried out worldwide for the past several decades, and the researches mainly focused on the mechanical behavior and failure characteristics of loess. The approach presented has not yet been addressed by other authors.  

 2nd revision:

Is this finding clearly stated in the introduction?

 

Point 5: Page 2, lines 61-70:

“To evaluate the influence of the lime content and porosity on the tensile and compressive strength numerous researches STUDIES were performed by Consoli et al. [34-36] on lime stabilized soil, and the results indicated that an increase in lime content caused a linear growth in the tensile and the compressive strength, while the porosity showed the opposite trend. In addition, the void/lime ratio adjusted by a power coefficient had been demonstrated to be an accurate parameter to assess the tensile and compressive strength of the lime stabilized soil. However, there are no existing failure criteria to explain them explicitly (CLARIFY IN THE TEXT WHAT THE AUTHORS MEAN BY THIS). So far, the Coulomb criterion is generally used to establish a failure envelope for the stabilized soil with a specific amount of stabilization agent and porosity. However, this process needs of triaxial compression tests to be carried out, and many other complicated and time-consuming tests [37-39].” INCLUDE WHAT OTHER TYPES OF TESTS ARE REQUIRED.

Response 5: According to the reviewer’s suggestion, “researches” has been changed to “studies”.

Thanks for the comments. The authors have re-read the relevant literatures and removed the sentence “However, there are no existing failure criteria to explain them explicitly” and revised the sentences “However, this process needs of triaxial compression tests to be carried out, and many other complicated and time-consuming tests” as follows: However, determination of Mohr-Coulomb failure envelope parameters of stabilized soils requires carrying out triaxial test or Direct shear test, which are complex and time-consuming.

 

Point 6: Page 2, line 76:

“…also established, as shown in the following equation: c=0.225q_c+50 (in kPa).” INCLUDE QUOTE.

 Response 6: According to the reviewer’s suggestion, the referenced literature has been added, as follow: “36.Mitchell, J. K. Soil improvement-state-of-the-art report. In Proc. 10th Int. Conf. on Soil Mechanics and Foundation Engineering, International Society of Soil Mechanics and Foundation Engineering, Stockholm, Sweden, 1981; pp 509-565.”

 

Point 7: Page 2, lines 81-82:

“…However, their ratio is independent of the above factors and tends to a constant value, and the ratio value is linked to the friction angle of the treated soil.”  IN THE TEXT WHAT RATIO ARE YOU REFERRING TO.

Response 7: Thanks for the comments, “their ratio” means “the ratio of unconfined compressive strength to splitting tensile strength”. The authors have clarified in the text.

 

Point 8: Page 2, lines 87-91- objectives of the research:

Improve presentation of the study objectives. Suggestions: It should be clearly stated that the results of the triaxial tests are also intended to be used to develop a power function equation that allows to obtain the lime treated loess soil cohesion as a function of parameters that can be obtained through simpler, less costly and time consuming tests. Clearly state the innovation of the study.

Response 8: The authors appreciate the reviewer’s comment. According to the reviewer’s suggestion, the study objectives has been improved, as follow: “The present research aimed to establish the functional relationship between the Mohr–Coulomb failure envelope parameters (e.g. c and φ) obtained by conducting a series of triaxial tests, and the content of lime, the porosity and the curing age of lime stabilized loess. Based on the functional relationship, the Mohr–Coulomb failure envelope parameters of lime stabilized loess were obtained by conducting simpler, less costly and time-consuming tests (such as density test and specific gravity test) and calculation process, without the need for complicated time-consuming triaxial tests, thus making it more cost and time efficient.”

2nd revision:

“The present research aimed to establish the functional relationship between the Mohr–Coulomb failure envelope parameters (e.g. c and φ) obtained by conducting a series of triaxial tests, and the content of lime, the porosity and the curing age of lime stabilized loess. Based on the functional relationship, the Mohr–Coulomb failure envelope parameters of lime stabilized loess were obtained by conducting simpler, less costly and time-consuming tests (such as density test and specific gravity test) and calculation process, without the need for complicated time-consuming triaxial tests, thus making it more cost and time efficient.”

The changes introduced made the sentence long and confusing. Improve this aspect for better understanding.

 

Point 9: Materials and experimental

Section 2.2 and 2.4:

Consider moving the content from section 2.2 to section 2.4 (it makes more sense) and include information on the amount of water, soil and lime considered in the prepared specimens, the total number of specimens and the cure temperature.

Response 9: Thanks for the comments. According to the reviewer’s suggestion, the content section 2.2 has been moved to section 2.4. The information on the amount of water, soil and lime considered in the prepared specimens is listed in Table 3. 

2nd revision:

Total number of specimens and the cure temperature still missing in the Materials and Experimental section.

 

Point 10: Section 2.3:

Page 4, line 122-123:

“Standard compaction test is generally performed to determine the maximum dry density, the optimum moisture content, and to achieve the target in-situ degree of compaction [48].” THIS SENTENCE NEEDS NO QUOTATION AS IT IS A GENERAL KNOWLEDGE FINDING FOR THOSE WORKING IN THIS AREA OF KNOWLEDGE.

Response 10: Thanks for the comments. The quoted reference has been removed.

 

Point 11: Page 5, Table 3:

Consider adding a column with porosity values in Table 3.

Response 11: According to the reviewer’s suggestion, the porosity values have been added in Table 3.

 

Point 12: Clarify in the text that the compaction tests allowed to obtain the dry density and water content to be considered in the specimens tested in the triaxial test. Why were not included in the text typical values of loess soil for dry density, water content (and also angle of internal friction and cohesion) or a non-lime treated control specimen to allow comparison with the values obtained in the study? It is important to include this aspect. Clarify in the text why the molding point D was chosen specifically to investigate the effect of lime content on the strength behaviour (with a dry density of 1.48g/cm³and different lime percentages)?

Was this procedure and the one used to investigate the effect of porosity based on studies/approaches performed by other researchers?

Response 12: Thanks for the comments. It is a pity that I have not done values measurement of loess soil for dry density, water content (and also angle of internal friction and cohesion) or a non-lime treated control specimen, but I will make further improvement in the follow-up research.

2^nd revision:

The authors can include typical values of these parameters or values obtained by other authors for this loess soil (Lanzhou), which allows to easily understand the improvements introduced by lime stabilization.

In this paper, the effect of lime content and porosity on cohesion of stabilized loess is studied by orthogonal method. The specimens at point C, D, E have the same lime content (23%) but different dry density (the difference vaule in dry density is 0.1g/cm³). The specimens at point D have the dry density but different lime content (10%, 16%, 23%), which can eliminate the interference of the dry density on the results in investigating the effect of lime content on the cohesion. Specimens at points C and D can also be fabricated with the above three different lime contents to investigate the effect of lime content on cohesion. In order to reduce the unnecessary workload, the D point is selected.

2^nd revision:

No particular reason? I still don't understand why point D was chosen and not C. For point C, dry density was determined in the standard compaction test (1.58g / cm3).

This procedure and the one used to investigate the effect of porosity were based on the approaches performed by Consoli et al. (Reference cited: 34. Consoli, N. C.; Lopes, L. d. S., Jr.; Heineck, K. S., Key Parameters for the Strength Control of Lime Stabilized Soils. Journal of Materials in Civil Engineering 2009, 21, (5), 210-216.)

 2nd revision: Is this clearly stated in the manuscript?

 

Point 13: Section 2.4:

Clarify in the text the type of triaxial test performed (consolidated-drained).

Response 13: The type of triaxial test performed has been clarified in the text, as follow: The static consolidated drained triaxial tests were conducted to obtain the failure envelope parameters of lime stabilized loess samples in accordance with ASTM D7181.

 

Point 14: Results and Discussion

Section 3.1:

Following the interpretation of results presented in lines 179- 186 (pages 6 and 7), also comment the maximum values of q versus εa (%). It is recommended to present the mean, mode, median and standard deviation of the results obtained for the angle of internal friction, since they allow a better support for the interpretation of results (table 4), conclusion and adoption of a value to consider when applying the developed power function equation (in section 3.2).

Response 14: Thanks for the comments. The authors have commented the maximum values of q versus εa, as follow: the critical value of the transition from the plastic phase to the failure phase when the specimen is under pressure.
According to the reviewer’s suggestion, the mean, median and standard deviation of the results obtained for the angle of internal friction have been presented in the text, which were 37.25, 37.25 and 0.37, respectively. In addition, the authors added Figure 4 in the text, which shows Effect of lime content and dry density on angle of internal friction of speicmens at all molding points with all curing time, as follow,
Figure 4. Effect of lime content and dry density on angle of internal friction of speicmens at all molding points with all curing time
“Figure 4 shows the angle of internal friction of specimens with 10 to 23% lime contents and 1.38 to 1.71g/cm3dry density and cured for 7 days, 28days, 90days and 180days, respectively, it can be readily seen that no correlation can be observed between the angle of internal friction and lime content or dry density of lime stabilize loess specimens for all curing time.” 

 2nd revision:

I did not find the sentence "the critical value of the transition from the plastic phase to the failure phase when the specimen is under pressure" in the revised manuscript.

 

Point 15: Page 8, line 200:

Do you mean Table 5 instead of Figure 4?

Response 15: Thanks for the comments. The meaning of this sentence is not clearly expressed, The author has revised this sentence, as follows: In order to further verify the reliability of the above test results, the shear failure angle between the shear failure plane and the major principal plane was determined for each specimen, and the shear failure plane was marked with a red lines, as shown in Figure 5.

 

Point 16: Page 8, Figure 4:

Adopt the same order of tested specimens presentation used in Figure 3 (improves comparison of results).

 Response 16: Thanks for the comments. The authors have adjusted the order of tested specimens presentation used in original Figure 4. The details of the revision are shown in Figure 5.

 

Point 17: Page 9, lines 211-213:

“After curing for 180 days, the most of specimens have been pressured into piece when they were taken out of the rubber film, and thus the angle between the between the shear failure plane and the major principal plane could not be measured.” THIS INFORMATION IS REPEATED IN THE TEXT SO IT CAN BE DELETED IN ONE OF THE PLACES WHERE IT IS DISPLAYED.

Response 17: According to the reviewer’s suggestion, the sentence “the specimens of 180 days of curing had been crushed to pieces during the test due to high brittleness”has been deleted.

 

Point 18: Page 8-9, Table 5:

Try to put the entire table on the same page. It is also recommended to include a small statistical analysis (as recommended for the values obtained for the angle of internal friction). This basic statistical analysis can help explain why the 45°+ φ/2 calculation for the values obtained is closer to 63° than 68° (angle of shear plane).

Response 18: Thanks for the comments. The location of the table will be adjusted during the “final proof-reading” period.

According to the reviewer’s suggestion, the authors made a statistical analysis of the values in Table 5, as follows: “Combining with the measured shear failure angles, the estimated values of φ varied from 36° to 46°, the mean and median of which were 41.5° and 42°,respectively, and the percentage difference of mean and median of the angle of internal friction obtained by this two approaches were 11.4% and 12.8%, respectively. It can be seen that the φ calculated from the shear failure angle is quite close to the measured values from the triaxial compression test.”

 2^nd revision:

The authors presented a way of interpreting the data. What I wanted to convey with my comment was that using the average (37.25), 45 + 37.25 / 2 = 63.6%, the value obtained is closer to 63% (the lower limit of the 63-68º range).

 

Point 19: Section 3.2:

Page 9, Figure 5:

Do not start the section with Figure 5. Place the figure after the first paragraph of this section. Check and comment on R² value obtained for 7 days of curing (0.221). In the figure 5 caption is missing the letter "D": “Effect of lime content and curing time on the c of SPECIMENS at molding point D”.

Response 19: Thanks for the comments. According to the reviewer’s suggestion, the authors have adjusted the location of original Figure 5.

The strength growth of lime stabilized loess is a relatively long process. In the early stage of curing, the effect of lime content on the cohesion is not very obvious. The increase in lime content did not cause a linearly increase on the cohesion, as explained in the text: “For 7 days of curing regime, the cohesion c of lime stabilized loess increased up to a lime content of 16%, but then showed a slightly decreasing trend when the lime content was 23%”, which led to a lower R² value (0.221). With the increase of curing age, the effect of lime content on cohesion is more obvious, and strength increases approximately linearly with the increase in the lime content.

2^nd revision:

“For 7 days of curing regime, the cohesion c of lime stabilized loess increased up to a lime content of 16%, but then showed a slightly decreasing trend when the lime content was 23%”, which led to a lower R2 value (0.221).” Consider to include this explanation in the manuscript.

The letter "D" has been added in caption of the original Figure 5.

 

Point 20: Page 10, lines 242-244:

“…Therefore, it was possible to establish a relation between the cohesion of lime stabilized loess and the ratio of voids volume to lime volume (VV/VLi). A similar improvement by adding a power (ς) was also considered.” IT IS NECESSARY TO INCLUDE IN THE TEXT AN EXPLANATION OF HOW THESE POWERS CAN BE OBTAINED. THIS ASPECT IS NOT CLEARLY ADDRESSED IN THE TEXT, SO IT IS NOT POSSIBLE TO UNDERSTAND HOW THE POWERS PRESENTED IN FIGURE 7 WERE OBTAINED (0.11, 0.17, 0.35 AND 1.15). This is an important aspect of this study and must be properly presented and justified.

 Response 20: Thank you very much for your advice. The approach of the power has been explained in the text, as follow: “The Solving process of the power is very tedious. During the process, amounts of different values were used as the power (ς), and then regression fitting is performed by “original” software to obtain different correlation coefficients (R²). The value corresponding to the maximum correlation coefficient is selected as the power.”

 

Point 21: Page 12, lines 281-284:

“Therefore, the use of voids of compacted mixture divided by the volumetric lime content, adjusted by a power (the variation of this power is mainly controlled by the curing time) to assess the cohesion c in the lime OF THE LOESS SOIL TREATED WITH LIME?, further in view of loess studied is herein sufficiently accurate for all considered curing times.” IMPROVE SENTENCE.

Response 21: Thanks for the comments. The authors have improved the sentence, as follow: “Therefore, the use of voids of compacted mixture divided by the volumetric lime content, adjusted by a power (the variation of this power is mainly controlled by the curing time) to assess the cohesion c in the lime stabilized loess studied is herein sufficiently accurate for all considered curing times.”

 

Point 22: Page 12, line 289:

Include the reason for having adopted an angle of internal friction of 37.5º and not another value from the range 36.5º to 38º.

Response 22: Thank you very much for your advice. The authors have changed the angle of internal friction of 37.5ºto the value from the range 36.5º to 38º. The details of revision are shown in Figure 11.

 

Point 23: Pages 13-14, Figure 10:

Try to put the entire table on the same page. Please comment on the angle of internal friction and cohesion values (percentage difference) obtained from the Mohr-Coulomb failure envelopes obtained from triaxial test results and equation (9) (including the adopted angle of internal friction = 37.5º).

The cohesion values obtained applying equation (9) are different from the ones obtained from the triaxial test results. For the cases shown in Figure 10, this variation ranges from approximately -19% to +3%, and therefore needs interpretation. This is an important aspect that should be commented and include in the manuscript. Suggestion for future work: to statistically validate the similarity of values obtained based on triaxial test and equation (9).

 Response 23: Thanks for the comments. The location of the table will be adjusted during the “final proof-reading” period.

The authors have statistically validated the similarity of values obtained based on triaxial test and equation (9) in the text, as follow: “The comparative analysis was conducted to the cohesion values obtained by applying equation (9) and the ones obtained from the triaxial test results for 28 groups of specimens studied. The results indicated that the percentage difference between the cohesion values obtained by the above two approaches ranged from -19% to 19.7% for 25 groups of specimens, and percentage difference was greater than 20% for other 3 groups of specimens, which were -22.9%, 34.9% and 35.9%.”

2^nd revision:

There are specific statistical methods to validate similarity between groups of values. This analysis can be done in future work. The way the authors hold the results does not support 2"Therefore, the use of voids of compacted mixture divided by the volumetric lime content, adjusted by a power (the variation of this power is mainly controlled by the curing time) to assess the cohesion c in the lime stabilized loess studied is herein sufficiently accurate for all considered curing times". Variations from -19 to 19% can be considered significant. Refer in the text to the number of specimen groups with smaller percentage difference to better support the findings.

 

Point 24: Conclusion

Page 14, lines 309-311:

Also refer in this sentence to and porosity.

Response 24: Thanks for the comments. “Curing time” and “porosity” have been added in the sentence, as follow: “Loess collected from Lanzhou city in northwest China was stabilized with different lime content, porosity and curing time, and its Mohr-Coulomb failure envelope parameters were investigated based on triaxial compression test. The study offered following conclusions:”

 

Point 25:  Page 14, lines 321-323:

Consider including the type of regression adopted.

Response 25:  The authors appreciate the reviewer’s comment. The type of regression adopted has added in the conclusion, as follow, “The relationship between lime content, void ratio, curing time and cohesion was established using the power function fitting regression of experimental data.”

 

Point 26: Page 14, lines 327-328:

“(6) The Mohr-Coulomb failure envelopes OBTAINED WITH EQUATION (9) provided a good representation of the tangent to the Mohr semicircles drawn based on triaxial test of studied lime stabilized loess.” WHAT ARE THE AUTHORS BASED ON TO STATE THAT IT IS “A GOODREPRESENTATION OF THE TANGENT TO THE MOHR SEMICIRCLES DRAWN BASED ON TRIAXIAL TEST OF STUDIED LIME STABILIZED LOESS”. SEE COMMENT IN SECTION 3.2.

Response 26: Thank you very much for your advice. According to the reviewer’s suggestion, the authors adjusted the value of φ, which ranges from 36.5° to 38°, as shown in Figure 11. Moreover, the similarity of cohesion values obtained based on triaxial test and Equation (9) have been statistically validated in the text. Therefore, with the increase of confining pressure, the Mohr-Coulomb failure envelopes obtained from the triaxial test results will finally change within a region, which is bounded by two envelops obtained by applying equation (9) and φ ranged from 36.5° to 38°.

 

Point 27: The conclusions can be explained in a more detailed and understandable manner. The manuscript lacks a clear explanation of how the results can be used for base and sub-base road pavement design and solution decision making. 

Response 27: Thank you very much for your advice. The explanation of how the results can be used for base and sub-base road pavement design and solution decision making has been presented in the text, as follow: “In base and sub-base road pavement design， the engineer can choose the lime content, the compaction effort and curing time appropriate to provide a mixture that meets the strength required by the project at the optimum cost. Moreover, once a poor compaction has been identified, it can be readily taken into account in the design, through the methodology proposed in this study, and adopting corrective measures accordingly such as the reinforcement of the treated layer by increasing the amount of lime or extending the curing time.”

 2^nd revision:

This sentence “In base and sub-base road pavement design， the engineer can choose the lime content, the compaction effort and curing time appropriate to provide a mixture that meets the strength required by the project at the optimum cost. Moreover, once a poor compaction has been identified, it can be readily taken into account in the design, through the methodology proposed in this study, and adopting corrective measures accordingly such as the reinforcement of the treated layer by increasing the amount of lime or extending the curing time.” is best suited for the conclusions section.

 

Point 28: Consider diversifying bibliographic references and include studies related to triaxial testing in loess soils. 10 references to the same author (Consoli, N. C.) out of 51 references is too much. Consider change this aspect.

Response 28: According to the reviewer’s suggestion, the author has adjusted the cited literatures of Consoli, N. C. and deleted the following references:

35.Consoli, N. C.; da Silva Lopes Jr, L.; Heineck, K. S. Variables controlling stiffness and strength of lime-stabilized soils. Journal of Geotechnical and Geoenvironmental Engineering 2010, 137, (6), 628-632.

Consoli, N. C.; Dalla Rosa Johann, A.; Gauer, E. A.; Dos Santos, V. R.; Moretto, R. L.; Corte, M. B. Key parameters for tensile and compressive strength of silt-lime mixtures. Geotechnique Letters 2012, 2, 81-85.

38.Consoli, N. C.; da Silva Lopes Jr, L.; Consoli, B. S.; Festugato, L. Mohr-Coulomb failure envelopes of lime-treated soils. Geotechnique 2014, 64, (2), 165-170.

Wang, Y.; Guo, P.; Li, X.; Lin, H.; Liu, Y.; Yuan, H. Behavior of Fiber-Reinforced and Lime-Stabilized Clayey Soil in Triaxial Tests. Applied Sciences 2019, 9, (5), 900.

43.Consoli, N. C.; da Rocha, C. G.; Silvani, C. Devising dosages for soil-fly ash-lime blends based on tensile strength controlling equations. Construction and Building Materials 2014, 55, 238-245.

 

Author Response

Response to Reviewer 1 Comments

Point 1: Improve sentence “Finally, the Mohr-Coulomb failure envelopes were drawn for 47 triaxial specimens considering 7, 28, 90, and 180 days curing time and confining pressures varying from 50 to 500 kPa that the results obtained in the triaxial tests as well as those obtained by applying the proposed equation were compared, and the main conclusions can be drawn from this comparison.”

 Response 1: Thanks for the comments. The authors have improved the sentence, as follow, “Finally, the Mohr-Coulomb failure envelopes were drawn based on triaxial test for 47 specimens with various curing time and confining pressure, and the shear strength parameters obtained by the proposed equation were also compared with the experimental results.”

 

Point 2: Is this finding clearly stated in the introduction?

Response 2: According to the reviewer’s suggestion, the sentences “An extensive amount of triaxial tests related to the loess have been carried out worldwide for the past several decades, and the researches mainly focused on the mechanical behavior and failure characteristics of loess. The relationship between the Mohr–Coulomb failure envelope parameters and the factors mentioned above (lime content, porosity and curing time) has not yet been well addressed.” have been added in the introduction, which can be found in Page 3, lines 94-98. 

 

Point 3: The changes introduced made the sentence long and confusing. Improve this aspect for better understanding.

Response 3: Thanks for the comments. The authors have improved the sentence, as follow, “In this paper, a functional relationship to evaluate shear strength parameters is established by conducting a series of triaxial tests. The functional relationship was also successfully testedvalidated for stabilized loess with different lime content and porosity, considering 7, 28, 90 and 180 days of curing, based on which, shear strength parameters were obtained only by conducting simpler, less costly and time-consuming tests, such as density test and specific gravity test.”

 

Point 4: Total number of specimens and the cure temperature still missing in the Materials and Experimental section.

Response 4: Thanks for the comments. The total number of specimens and the cure temperature have been presented in the text, as shown on page 5, lines 169-171: “After preparation of all 240 specimens, in which, there are 23 spare specimens, they were cured in a humid room at a controlled humidity of above 95% and temperature of 20 ± 2 °C for different time points of 7 days, 28 days, 90 days and 180 days.”

 

Point 5: The authors can include typical values of these parameters or values obtained by other authors for this loess soil (Lanzhou), which allows to easily understand the improvements introduced by lime stabilization.

Response 5: Thanks for the comments. The authors have added the values of loess soil (Lanzhou) for dry density, water content, angle of internal friction and cohesion in Table 1. The values of loess soil (Lanzhou) for dry density, water content, angle of internal friction and cohesion was obtained by referring the literature related to Lanzhou loess, and the cited literature as follow:

43 Lv, Q.; Wang, S.; Wang, D.; & Wu, Z. (2014). Water stability mechanism of silicification grouted loess. Bulletin of Engineering Geology and the Environment 2014, 73, (4), 1025-1035.

 

Point 6: No particular reason? I still don't understand why point D was chosen and not C. For point C, dry density was determined in the standard compaction test (1.58g / cm³).

Response 6: The authors appreciate the reviewer’s comment. Specimens at points C and D can also be fabricated with the above three different lime contents to investigate the effect of lime content on cohesion. However, in the actual construction of pavement base and subgrade, the degree of compaction is generally above 90%, and less than 100%, so choosing point C is more in line with the actual project.

 

Point 7: This procedure and the one used to investigate the effect of porosity were based on the approaches performed by Consoli et al. (Reference cited: 34. Consoli, N. C.; Lopes, L. d. S., Jr.; Heineck, K. S., Key Parameters for the Strength Control of Lime Stabilized Soils. Journal of Materials in Civil Engineering 2009, 21, (5), 210-216.)

 2nd revision: Is this clearly stated in the manuscript?

Response 7: According to the reviewer’s suggestion, the sentence “Combining with the experiment procedure of Consoli et al. [34] and the results of Standard compaction test, 5 molding points (A, B, C, D and E) were set in this study” has been added in the section 2.2.

 

Point 8: I did not find the sentence "the critical value of the transition from the plastic phase to the failure phase when the specimen is under pressure" in the revised manuscript.

Response 8: Thanks for the comments. The sentence "the critical value of the transition from the plastic phase to the failure phase when the specimen is under pressure" has been added on page 7, lines 203-204.

 

Point 9: The authors presented a way of interpreting the data. What I wanted to convey with my comment was that using the average (37.25), 45 + 37.25 / 2 = 63.6%, the value obtained is closer to 63% (the lower limit of the 63-68º range).

Response 9: Thanks for the comments. The reviewer’ comment has been presented in the text, as shown on page 10, lines 253-254, as follow: “Also, using the average (37.25°) of the measured friction angles, 45 + 37.25° / 2 = 63.6°, the value obtained is closer to 63% (the lower limit of the 63-68° range).”

 

Point 10: “For 7 days of curing regime, the cohesion c of lime stabilized loess increased up to a lime content of 16%, but then showed a slightly decreasing trend when the lime content was 23%, “which led to a lower R² value (0.221).” Consider to include this explanation in the manuscript.

Response 10: Thanks for the comments. The sentence “which led to a lower R² value (0.221).” has been added in the manuscript, as shown on page 10, line 260.

 

Point 11: There are specific statistical methods to validate similarity between groups of values. This analysis can be done in future work. The way the authors hold the results does not support 2"Therefore, the use of voids of compacted mixture divided by the volumetric lime content, adjusted by a power (the variation of this power is mainly controlled by the curing time) to assess the cohesion c in the lime stabilized loess studied is herein sufficiently accurate for all considered curing times". Variations from -19 to 19% can be considered significant. Refer in the text to the number of specimen groups with smaller percentage difference to better support the findings.

Response 11: Thanks for the comments. The authors appreciate the reviewer’s comment. According to the reviewer’s suggestion, the authors have changed the text, as shown on pages 13-14, lines 323-329, as follow: “There are specific statistical methods to validate similarity between groups of values. This analysis can be done in future work. and percentage difference was greater than 20% for other 3 groups of specimens, which were -22.9%, 34.9% and 35.9%, respectively.

Therefore, the use of voids of compacted mixture divided by the volumetric lime content, adjusted by a power (the variation of this power is mainly controlled by the curing time) to assess the cohesion c in the lime stabilized loess studied is herein sufficiently relatively accurate for all considered curing times.”

 

Point 12: This sentence “In base and sub-base road pavement design, the engineer can choose the lime content, the compaction effort and curing time appropriate to provide a mixture that meets the strength required by the project at the optimum cost. Moreover, once a poor compaction has been identified, it can be readily taken into account in the design, through the methodology proposed in this study, and adopting corrective measures accordingly such as the reinforcement of the treated layer by increasing the amount of lime or extending the curing time.” is best suited for the conclusions section.

Response 12: Thanks for the comments. According to the reviewer’s suggestion, the sentence “In base and sub-base road pavement design, the engineer can choose the lime content, the compaction effort and curing time appropriate to provide a mixture that meets the strength required by the project at the optimum cost. Moreover, once a poor compaction has been identified, it can be readily taken into account in the design, through the methodology proposed in this study, and adopting corrective measures accordingly such as the reinforcement of the treated layer by increasing the amount of lime or extending the curing time.” has been changed and moved to the conclusions section, as follow: “In pavement design, the engineers need to choose the appropriate lime content, the compaction effort and curing time to provide an optimum mixture. Therefore, the proposed formulas in this study provide a useful reference for a quick and reliable design.”

 

Author Response File: Author Response.pdf