Experimental Investigation of Consolidated Undrained Shear Behavior on Peaty Soil in Dian-Chi, China
Round 1
Reviewer 1 Report
In this study, a series of strain-controlled, consolidation undrained triaxial tests were conducted to investigate the undrained shear strength, strain behavior, excess pore pressure development and strength properties of undisturbed Dian-Chi peaty soils in Yunnan, China. This article can be accepted with major revisions.
1. References to Studies under Isotropic Consolidation should be added to the manuscript.
2. The map in Figure 1 should have latitude and longitude added.
3. Why is Shear rate set to 0.05%/min?
4. How does the author judge that the sample is saturated? The author can refer to the following literature:
Chen Xiang, Shen Jian-Hua, Wang Xing, Yao Ting, Xu Dong-Sheng. Effect of saturation on shear behavior and particle breakage of coral sand. Journal of Marine Science and Engineering. 2022, 10(9): 1280. DOI: 10.3390/jmse10091280.
Shen Jian-Hua, Hu Ming-Jian*, Wang Xing*, Zhang Chen-Yang, Xu Dong-Sheng. SWCC of calcareous silty sand under different fines contents and dry densities. Frontiers in Environmental Science. 2021, 9: 682907. DOI:10.3389/fenvs.2021.682907.
5. There is an inflection point in the end curve of deviatory-axial strain in FIG. 11(a). Is this stress sensor out of range?
Author Response
1). References to Studies under Isotropic Consolidation should be added to the manuscript.
Reply: Reference No. 16 is added in the revised manuscript.
2). The map in Figure 1 should have latitude and longitude added.
Reply: The coordinate of the location is added in the revised manuscript.
3). Why is Shear rate set to 0.05%/min?
Reply: The shear process specified in BS 6.3.6 shall not be less than 2h, and the shear rate shall not be greater than 0.125%/min-0.167%/min according to the strain range of 15% - 20%. In addition, the shear rate of 0.05%/min is used in the research of Yamaguchi (1985) on the triaxial test of peat soil, so this paper selects this shear rate.
4). How does the author judge that the sampleis saturated? The author can refer to the following literature
Chen Xiang, Shen Jian-Hua, WangXingYao TingXu Dong-Sheng. Effect of saturation on shear behavior and particle breakage of coral sand. Journal of Marine Science and Engineering.2022,10(9): 1280.DOI:10.3390/imse10091280.
Shen Jian-Hua, Hu Ming-Jian，Wang Xing, Zhang Chen Yang, Xu Dong-Sheng. SWCC of calcareous silty sand under different fines contents and dry densities. Frontiers in Environmental Science20219:682907 DOl:10.3389/fenvs.2021.682907
Reply: Thanks for the references provided by the review experts, the standard for judging whether the sample is saturated depends on the B value, that in B-check is greater than 0.98.
5)There is an inflection point in the end curve of deviatory axial strain in FIG.11(a).Is this stress sensor out of range?
Reply: Not out of range, the inflection point is the start of strain-softening.
Reviewer 2 Report
Comments for author File: 
Comments.pdf
Author Response
1) The authors should summarize the main contributions of this paper in abstract. Some details need to be clarified, i.e. ‘A correlation was proposed by curve fitting of the … their nonlinear relationship’ – Could ‘their’ be clarified?
Reply: This problem has been clarified in the revised version.
2) The authors should be formatted consistently for all figures.
Reply: All the figures has been formatted.
3) In Section 2.2, the authors mentioned that “the main physical property index and three standards”. However, the differences between the three standards for physical property testing of peaty soils are not stated, please complete it.
Reply: The main physical property index test was based on the ASTM (2014), the problem was clarified in the revised version.
4) In Section 3.1 Fig.4, the initial B value varies greatly, and no explanation is given in the text.
Reply: The test shows that the saturation degree of peat soil specimens with the same organic content is different, so the B value is also different.
5) In Section 3.2, the introduction of the parameters in the specification (BS) should be briefly explained, and each parameter should be explained when it first appears, and there is no need to repeat it later to avoid excessive space.
Reply: This problem has been modified in the revised version.
6) The parameter l in formula 2, since the size of the sample is fixed, the specific constant value should be given directly in the text.
Reply: Yes, l is a constant, this problem has been modified in the revised version.
7) In Section 3.3, the parameter ef needs to indicate whether it is the failure strain or the corresponding strain when the contraction phenomenon occurs.
Reply: ef is the failure strain; this problem has been clarified in the revised version.
8) In Fig.12, why only two cases of pressure 100kPa and 105kPa are given in the normalized analysis, and how to explain the normalized properties under different confining pressures.
Reply: In order to directly study the influence of organic matter content.
9) The authors should summarize the conclusions of this paper.
Reply: The problem has been modified in the revised version.
10) There are some grammar mistakes, please check the manuscript carefully. i.e. Introduction - second paragraph: …conducted by our research team on the typical peat soil …
Reply: The problems have been modified in the revised version.
11) To change ‘Oedometer’ to ‘Oedometer’
Reply: The problem has been modified in the revised version.
Reviewer 3 Report
There are very few studies on the evaluation of the engineering behavior of peat soils. In this study, a CU test was performed on undisturbed peat soils, evaluated together with the results of the previous consolidation test, and relations were proposed for the effective strength parameters depending on the peat ratio.
Some suggestions were made to make the study more understandable;
-Since the N symbol is used for the first time in the last paragraph of the introduction (page 4), the N symbol should be explained.
It is recommended to change the symbols used in the undrained strength ratio definition. The symbol defined as the confining pressure is known as the pre-consolidation pressure in the general literature.
-Is the legend content of Figure 4 correct?
-What is the strain level at which the failure is defined in the stress-strain curves? Especially in behaviors that do not have a peak value.
-In Figure 12, the failure line is not shown. In addition, the stress paths are not in agreement with the stress-strain curves. This situation should be made clear.
-Item 2 expressed in the conclusions section should be reviewed.
-The effect of the over-consolidation rate on the effective strength of peat soils is significant. Therefore, it should also be mentioned in the conclusions section whether the sample is over-consolidated or normally consolidated.
Author Response
1) Since the N symbol is used for the first time in the last paragraph of the introduction (page 4),the N symbol should be explained.
Reply: N is the organic matter content, which is added in the revised manuscript.
2) It is recommended to change the symbols used in the undrained strength ratio definition. The symbol defined as the confining pressure is known as the pre-consolidation pressure in the general literature.
Reply: Thanks for your valuable comments. There is the special explanation for the definition of undrained strength ratio in the manuscript, and there are many concerns about the ambiguity caused by modification. But we will pay attention to the differences in future.
These symbols have been changed in the revised manuscript.
3) ls the legend content of Figure 4 correct?
Reply: Yes, Figure 4 is correct. The test shows that the saturation degree of peat soil specimens with the same organic content is different, so the B value is also different.
4) What is the strain level at which the failure is defined in the stress-strain curves? Especially in behaviors that do not have a peak value.
Reply: The peak point serves as the failure point in this text, for the sample that do not have a peak value and not out of range, the failure point is taken as 15% of the strain, for the out of range refer to the study of Hendry (2012) that a reference in our text.
5) In Figure 12 the failure line is not shown. In addition, the stress paths are not in agreement with the stress-strain curves. This situation should be made clear.
Reply: There is no obvious peak point in the stress-strain curve of the specimen with N=75% and 85% in Fig. 12 (a) under the effective pressure of 100kPa, but it is found that there is an obvious inflection point in combination with the stress path curve of the specimen in 12 (c). The inflection point is the peak point by referring to other curves with obvious stress and strain peaks, and the specimen is also sheared during the test. For peat soil with high organic matter content, the phenomenon of no peak test and no shear failure does occur in the triaxial test due to the limited strain range in the shear process. For this phenomenon, refer to the research of Henry (2012), but the peat soil sample studied in this paper is definitely sheared. With reference to this opinion, we will further clarify it in the text.
6) ltem 2 expressed in the conclusions section should be reviewed.
Reply: ltem conclusion 2 is reviewed in the revised manuscript.
7) The effect of the over-consolidation rate on the effective strength of peat soils is significant. Therefore, it should also be mentioned in the conclusions section whether the sample is over-consolidated or normally consolidated.
Reply: Samples under 25kPa is over-consolidated state, the other stress state is normally consolidated, has been highlighted in the revised manuscript.
