# Experimental Research on Resilient Modulus of Silty Clay Modified by Oil Shale Ash and Fly Ash after Freeze-Thaw Cycles

^{1}

^{2}

^{*}

## Abstract

**:**

## 1. Introduction

_{u1%}, which represents the stress at the axial strain of 1% in unconfined compression tests. Their studies demonstrated that the performance reduction effect exhibited after the first F-T cycle is about 50% when S

_{u1%}is greater than 103 kPa. The obvious reduction effect was also verified by Simonsen et al. based on measuring properties of several road materials after F-T cycles [25]. Existing experimental studies about the influence of F-T cycles on soil property have provided valuable results. The physical and mechanical property of soils modified by multiple additives such as FA and OSA are unknown and worth studying. To evaluate the performance of a modified material as subgrade filling in seasonally frozen regions, it is necessary and crucial to master the variation characteristics of its dynamic resilient modulus after multiple F-T cycles.

## 2. Materials and Methods

#### 2.1. Materials

#### 2.1.1. Raw Materials

#### 2.1.2. Mixed Materials

#### 2.2. Methods

#### 2.2.1. Preparing of Test Samples

#### 2.2.2. Test Procedures

#### 2.2.3. Process of Freeze-Thaw (F-T) Cycles

#### 2.2.4. Damage Ratio of Resilient Modulus

#### 2.2.5. Image Processing Technology for SEM Testing

_{3}= 50 kPa, σ

_{d}= 25 kPa) were adopted to conduct the SEM tests after F-T cycles. After the resilient modulus test, the soil samples were naturally dried. Small rectangular samples with a size of 10 mm × 5 mm × 5 mm (height × length × width) were cut from the specimens. They were glued on trays and gilded for scanning. To observe the microstructure of cohesive soils, the magnification of 500× to 1000× is suitable. In this manuscript, the test samples were captured at the magnification of 500× and 600×. Three evenly distributed points in each test sample were selected and scanned by electron microscopy. Images with no delta points (points containing specific information, such as cracks) and clearly reflecting the typical structure of soils were obtained as the representative images for further imaging analysis. The scanned images are processed as follows:

## 3. Results and Discussion

#### 3.1. Effect of Stress State on Resilient Modulus

_{1}+ σ

_{2}+ σ

_{3}) are shown in Figure 4 and Figure 5, respectively.

_{c}= 50 kPa) is higher than that in low confining pressure (σ

_{c}= 40 kPa). From Figure 5, the resilient modulus increases with the increase of bulk stress. The variation trends of resilient modulus versus deviator stress and bulk stress are still significant after F-T cycles. In Figure 5, It should be noted that the shape of each data curve in Figure 5 is a break-line of horizontal “Λ”. The starting point and end point of the “Λ” curve are the resilient moduli of loading sequences 40-1 and 40-3, respectively. When the horizontal “Λ” curve is close to an “I” shape, it means that the resilient modulus values of 40-1 and 40-3 are exactly equal. This phenomenon is in accordance with the coincident curves of 40-1 and 40-3 in Figure 4, which illustrates that the influence of loading path on resilient modulus is insignificant under the same stress state. In consideration of the close resilient modulus values of 40-1 and 40-3, the data of process 40-3 is not analyzed in the following parts.

#### 3.2. Effect of F-T Cycles on Resilient Modulus

_{c}= 40 kPa) are close to those under the same deviator stress (σ

_{d}) in high confining pressure (σ

_{c}= 50 kPa). As for the modified SC, the damage ratios in high confining pressure (σ

_{c}= 50 kPa) are slightly less than those in low confining pressure (σ

_{c}= 40 kPa). Furthermore, the damage ratios of both materials under the deviator stress of 25 kPa (σ

_{d}= 25 kPa) are higher than those under the deviator stresses of 15 and 5 kPa (σ

_{d}= 15 kPa and σ

_{d}= 5 kPa). It revealed that for both materials, deviator stress is the main factor affecting the damage ratio of the resilient modulus after F-T cycles.

_{0}represents the damage ratio of materials after sufficient numbers of F-T cycles. It can be called a stable damage ratio after F-T cycles. The fitting results indicate that the stable damage ratios of the modified soil are better than those of unmodified soil. Therefore, the modified SC will have better application potential than unmodified SC in seasonally frozen regions.

#### 3.3. Significance Analysis of Influencing Factors on Resilient Modulus

#### 3.4. Effect of F-T Cycles on Microstructure for Soil Samples

_{d}= 25 kPa, σ

_{c}= 50 kPa) and pore parameters versus F-T cycles are drawn in Figure 9 and Figure 10.

## 4. Conclusions

- (1)
- The resilient moduli of both two materials are significantly influenced by their stress states. The resilient modulus always increases with the increase of confining pressure, and is inverse to the deviator stress, which is in accord with other research. F-T cycles are also an important factor affecting the resilient modulus of test soils. With increasing F-T cycles, the resilient modulus of unmodified SC decreases continually, while the resilient modulus of the modified SC decreases sharply after the first F-T cycle and then tends to be stable.
- (2)
- Damage ratio can be effectively adopted to describe the resilient modulus reduction after F-T cycles. For unmodified SC and the modified SC, their damage ratio variation trends after F-T cycles can be effectively fitted in the form of exponential decay equations.
- (3)
- The significance analysis demonstrates that the significance of confining pressure, deviator stress, and F-T cycles on resilient moduli for the two materials are great. For unmodified SC, the variance significance of confining pressure is the greatest, followed by F-T cycles and deviator stress. For the modified SC, the significance of confining pressure is also the greatest, then followed by deviator stress and F-T cycles.
- (4)
- From the SEM testing, the microstructure of unmodified SC is a whole platy structure with layered structures, while the microstructure of modified SC consists of a lot of fine particles and agglomerates, which possess greater stability after F-T cycles than unmodified SC. With increasing F-T cycles, the initial structure of soils is destroyed and the porosity also increases. The correlation analysis shows that the porosity and mean diameter of pores are strongly negatively correlated with the resilient modulus. The SEM testing also reflects the variation characteristics of pores for compacted soils after F-T cycles: the small pores gradually develop into medium and large pores.

## Author Contributions

## Funding

## Conflicts of Interest

## References

- Gobinath, V.; Stalin, V.K. Performance of geogrid reinforced rubber waste as subgrade material. In Indian Geotechnical Conference 2009; Guntur, India, 2009; pp. 178–182. Available online: https://www.tib.eu/en/search/id/TIBKAT%3A643919082/Indian-Geotechnical-Conference-IGC-2009-held-in/.
- Kua, T.A.; Arulrajah, A.; Horpibulsuk, S.; Du, Y.J.; Suksiripattanapong, C. Engineering and environmental evaluation of spent coffee grounds stabilized with industrial by-products as a road subgrade material. Clean Technol. Environ. Policy
**2017**, 19, 63–75. [Google Scholar] [CrossRef] - Arro, H.; Prikk, A.; Pihu, T.; Öpik, I. Utilization of semi-coke of Estonian shale oil industry. Oil Shale
**2002**, 19, 117–125. [Google Scholar] - Trikkela, A.; Kuusika, R.; Martinsb, A.; Stenceld, P.J.M. Utilization of Estonian oil shale semicoke. Fuel Process. Technol.
**2008**, 89, 756–763. [Google Scholar] [CrossRef] - Yarbaşı, N.; Kalkan, E.; Akbulut, S. Modification of the geotechnical properties, as influenced by freeze–thaw, of granular soils with waste additives. Cold Reg. Sci. Technol.
**2007**, 48, 44–54. [Google Scholar] [CrossRef] - Ghazavi, M.; Roustaie, M. The influence of freeze-thaw cycles on the unconfined compressive strength of fiber-reinforced clay. Cold Reg. Sci. Technol.
**2010**, 61, 125–131. [Google Scholar] [CrossRef] - Olufowobi, J.; Ogundoju, A.; Michael, B.; Aderinlewo, O. Clay soil stabilization using powdered glass. J. Eng. Sci. Technol.
**2014**, 9, 541–558. [Google Scholar] - Parsons, R.; Milburn, J. Engineering Behavior of Stabilized Soils. Transp. Res. Rec.: J. Transp. Res. Board
**2003**, 1837, 20–29. [Google Scholar] [CrossRef] - Prabakar, J.; Dendorkar, N.; Morchhale, R.K. Influence of fly ash on strength behavior of typical soils. Constr. Build. Mater.
**2004**, 18, 263–267. [Google Scholar] [CrossRef] - Turner, J.P. Soil stabilization using oil Shale solid wastes: Laboratory evaluation of engineering properties. J. Geotech. Eng.
**1994**, 120, 646–660. [Google Scholar] [CrossRef] - Mymrin, V.A.; Ponte, H.A. Oil-shale fly ash utilization as independent binder of natural clayey soils for road and airfield base construction. Part. Sci. Technol.
**2005**, 23, 99–107. [Google Scholar] [CrossRef] - Reinik, J.; Irha, N.; Koroljova, A.; Meriste, T. Use of oil shale ash in road construction: Results of follow-up environmental monitoring. Environ. Monit. Assess.
**2018**, 190, 59. [Google Scholar] [CrossRef] [PubMed] - Kaljuvee, T.; Štubňa, I.; Somelar, P.; Mikli, V.; Kuusik, R. Thermal behavior of some Estonian clays and their mixtures with oil shale ash additives. J. Therm. Anal. Calorim.
**2014**, 118, 891–899. [Google Scholar] [CrossRef] - Balo, F.; Yucel, H.L.; Ucar, A. Determination of the thermal and mechanical properties for materials containing epoxidised palm oil, clay and fly ash. Int. J. Sustain. Eng.
**2010**, 3, 47–57. [Google Scholar] [CrossRef] - Jafer, H.; Atherton, W.; Sadique, M.; Ruddock, F.; Loffill, E. Stabilisation of soft soil using binary blending of high calcium fly ash and palm oil fuel ash. Appl. Clay Sci.
**2018**, 152, 323–332. [Google Scholar] [CrossRef] - Uzan, J. Characterization of granular material. Transp. Res. Rec.
**1985**, 1022, 52–59. [Google Scholar] - Ni, B.; Hopkins, T.C.; Sun, L.; Bechham, T.L. Modeling the resilient modulus of soils. In Proceedings of the 6th International Conference of the Bearing Capacity of Roads and Airfields, Lisbon, Portugal, 24–26 June 2002; pp. 1131–1142. [Google Scholar]
- American Association of State Highway and Transportation Officials (AASHTO). Resilient Modulus as Function of Soil. Guide for Mechanistic-Empirical Design of New and Rehabilitated Pavement Structures; American Association of State Highway and Transportation Officials: Washington, DC, USA, 2000; pp. 56–66. [Google Scholar]
- Lee, J.; Kim, J.; Kang, B. Normalized resilient modulus model for subbase and subgrade based on stress-dependent modulus degradation. ASCE Transp. Eng. J.
**2009**, 135, 600–610. [Google Scholar] [CrossRef] - Li, Z.Y.; Dong, C.; Zou, J.R.; Zou, W.L. Research on experiment and prediction model of dynamic resilient modulus of laterite soil in Southern Hunan. Rock Soil Mech.
**2015**, 36, 1840–1846. [Google Scholar] - Zhu, J.G.; Wang, Y.L.; Jia, H.; Zhang, B. Experimental study on resilience behaviour of coarse grained soils. Chin. J. Geotech. Eng.
**2011**, 33, 950–954. [Google Scholar] - Qi, J.; Vermeer, P.A.; Cheng, G. A review of the influence of freeze-thaw cycles on soil geotechnical properties. Permafr. Periglac. Processes
**2010**, 17, 245–252. [Google Scholar] [CrossRef] - Qi, J.; Wei, M.; Song, C. Influence of freeze–thaw on engineering properties of a silty soil. Cold Reg. Sci. Technol.
**2008**, 53, 397–404. [Google Scholar] [CrossRef] - Lee, W.; Bohra, N.C.; Altschaeffl, A.G.; White, T.D. Resilient modulus of cohesive soils and the effect of freeze–thaw. Can. Geotech. J.
**1995**, 32, 559–568. [Google Scholar] [CrossRef] - Simonsen, E.; Janoo, V.C.; Isacsson, U. Resilient properties of unbound road materials during seasonal frost conditions. J. Cold Reg. Eng.
**2002**, 16, 28–50. [Google Scholar] [CrossRef] - Ministry of Transport of the People’s Republic of China. Specifications for Design of Highway Subgrades (JTG D30-2015); China Communications Press: Beijing, China, 2015; p. 7. (In Chinese) [Google Scholar]
- Sun, P.; Liu, Z.; Gratzer, R.; Xu, Y.; Liu, R.; Li, B.; Meng, Q.; Xu, J. Oil yield and bulk geochemical parameters of oil shales from the Songliao and Huadian Basins, China: A grade classification approach. Oil Shale
**2013**, 30, 402–418. [Google Scholar] [CrossRef] - Taciuk, W. Does oil shale have a significant future? Oil Shale
**2013**, 30, 1–5. [Google Scholar] [CrossRef] - Ministry of Housing Urban-Rural Development of Republic of China. Technical Code for Application of Fly Ash Concrete (GB/T 50146-2014); China Planning Press: Beijing, China, 2014; pp. 4–5. (In Chinese) [Google Scholar]
- Cui, J.H. Research on Stability of Subgrade Soil Modified by Oil Shale Waste Residue and Fly Ash. Master’s Thesis, Jilin University, Changchun, China, May 2018. [Google Scholar]
- Wei, H.B.; Zhang, Y.P.; Cui, J.H.; Han, L.L.; Li, Z.Q. Engineering and environmental evaluation of silty clay modified by waste fly ash and oil shale ash as a road subgrade material. Constr. Build. Mater.
**2018**. under review. [Google Scholar] - Ministry of Transport of the People’s Republic of China. Test. Methods of Soils for Highway Engineering (JTG E40-2007); China Communications Press: Beijing, China, 2007; pp. 7, 223–226. (In Chinese) [Google Scholar]
- Chen, S.K.; Ling, J.M.; Zhang, S.Z. Fixing loading sequence for resilient modulus test of subgrade soil. Highway
**2006**, 11, 153–157. [Google Scholar] - Othman, M.A.; Benson, C.H. Effect of freeze-thaw on the hydraulic conductivity of three compacted clays from Wisconsin. Transp. Res. Rec.
**1992**, 1369, 118–125. [Google Scholar] - Salour, F.; Erlingsson, S. Resilient modulus modelling of unsaturated subgrade soils: Laboratory investigation of silty sand subgrade. Road Mater. Pavement Des.
**2015**, 16, 553–568. [Google Scholar] [CrossRef]

**Figure 3.**Procedure of image processing for SEM testing: (

**a**) original image; (

**b**) binarization processing; and (

**c**) removing points and small pores.

**Figure 4.**Variation curve of resilient modulus versus deviator stress for test soils after (

**a**) 0, (

**b**) 1, and (

**c**) 7 F-T cycles.

**Figure 5.**Variation curve of resilient modulus versus bulk stress for test soils after (

**a**) 0, (

**b**) 1, and (

**c**) 7 F-T cycles.

**Figure 6.**Variation curves of resilient modulus for test soils after F-T cycles of loading process (

**a**) 40-1 and (

**b**) 50-2.

**Figure 9.**Variation curves of resilient modulus and porosity versus F-T cycles for (

**a**) unmodified SC and (

**b**) the modified SC.

**Figure 10.**Variation curves of resilient modulus and mean diameter versus F-T cycles for (

**a**) unmodified SC and (

**b**) the modified SC.

Samples | Plastic Limit (%) | Liquid Limit (%) | Plasticity (%) | Optimum Moisture (%) | Maximum Density (g/cm^{3}) | |||||
---|---|---|---|---|---|---|---|---|---|---|

Mean | SD | Mean | SD | Mean | SD | Mean | SD | Mean | SD | |

Unmodified SC | 22.4 | 0.408 | 34.0 | 0.374 | 11.6 | 0.294 | 12.2 | 0.294 | 1.93 | 0.008 |

The modified SC | 20.2 | 0.283 | 32.6 | 0.294 | 12.4 | 0.327 | 15.0 | 0.283 | 1.52 | 0.014 |

Sequence | Confining Pressure σ_{c} (kPa) | Cyclic Deviator Stress σ_{d} (kPa) | Axial Stress σ_{1} (kPa) | Loading Cycles |
---|---|---|---|---|

0-Preloading | 30 | 36 | 66 | 1000 |

1 | 40 | 25 | 65 | 100 |

40 | 15 | 55 | 100 | |

40 | 5 | 45 | 100 | |

2 | 50 | 5 | 55 | 100 |

50 | 15 | 65 | 100 | |

50 | 25 | 75 | 100 | |

3 | 40 | 25 | 65 | 100 |

40 | 15 | 55 | 100 | |

40 | 5 | 45 | 100 |

Process | Deviator Stress (kPa) | Resilient Modulus after Several Freeze-Thaw (F-T) Cycles (MPa) | |||||||||
---|---|---|---|---|---|---|---|---|---|---|---|

0 | 1 | 3 | 5 | 7 | |||||||

Mean | SD | Mean | SD | Mean | SD | Mean | SD | Mean | SD | ||

40-1 | 25 | 123.69 | 2.09 | 99.56 | 1.98 | 78.92 | 1.60 | 68.55 | 0.68 | 62.96 | 1.05 |

15 | 142.31 | 1.63 | 116.77 | 1.23 | 96.03 | 1.13 | 86.63 | 1.23 | 79.15 | 1.34 | |

5 | 161.56 | 1.06 | 137.65 | 1.45 | 114.38 | 1.56 | 103.47 | 1.03 | 98.66 | 1.04 | |

50-2 | 25 | 169.33 | 1.84 | 139.72 | 1.67 | 105.65 | 1.03 | 90.3 | 1.56 | 83.89 | 0.76 |

15 | 190.51 | 1.53 | 159.65 | 1.09 | 121.23 | 0.96 | 106.32 | 0.96 | 102.39 | 1.35 | |

5 | 209.77 | 2.21 | 181.75 | 1.45 | 149.57 | 0.86 | 134.05 | 0.93 | 129.58 | 1.26 | |

40-3 | 25 | 127.24 | 1.89 | 103.58 | 1.23 | 80.35 | 1.18 | 74.8 | 0.76 | 64.17 | 0.78 |

15 | 149.45 | 1.65 | 120.71 | 1.68 | 95.98 | 1.63 | 85.65 | 1.36 | 81.42 | 0.95 | |

5 | 159.38 | 1.86 | 138.31 | 1.40 | 117.28 | 0.85 | 102.63 | 1.56 | 97.69 | 1.35 |

Process | Deviator Stress (kPa) | Resilient Modulus after Several F-T Cycles (MPa) | |||||||||
---|---|---|---|---|---|---|---|---|---|---|---|

0 | 1 | 3 | 5 | 7 | |||||||

Mean | SD | Mean | SD | Mean | SD | Mean | SD | Mean | SD | ||

40-1 | 25 | 126.28 | 1.56 | 81.12 | 0.98 | 80.68 | 0.76 | 78.98 | 0.86 | 80.01 | 1.24 |

15 | 139.09 | 1.43 | 94.82 | 0.76 | 93.58 | 0.86 | 96.54 | 0.69 | 96.18 | 0.98 | |

5 | 159.55 | 1.67 | 118.17 | 1.03 | 119.56 | 0.74 | 121.58 | 0.89 | 117.69 | 0.65 | |

50-2 | 25 | 159.22 | 1.13 | 106.53 | 0.62 | 104.56 | 0.89 | 103.87 | 1.26 | 107.55 | 0.86 |

15 | 182.24 | 0.85 | 131.97 | 0.89 | 132.98 | 1.32 | 130.75 | 0.65 | 134.39 | 0.74 | |

5 | 202.79 | 1.67 | 167.51 | 1.35 | 165.88 | 0.78 | 164.99 | 0.68 | 166.16 | 0.87 | |

40-3 | 25 | 126.82 | 1.48 | 83.54 | 0.69 | 84.12 | 1.13 | 82.95 | 0.74 | 84.56 | 0.69 |

15 | 140.69 | 2.03 | 96.42 | 0.59 | 97.01 | 0.69 | 95.58 | 0.95 | 96.87 | 0.93 | |

5 | 158.78 | 1.67 | 120.03 | 1.36 | 122.45 | 0.83 | 118.84 | 0.92 | 121.36 | 0.84 |

Process | Deviator Stress (kPa) | F-T Cycles | Fitting Equations | |||
---|---|---|---|---|---|---|

1 | 3 | 5 | 7 | |||

40-1 | 25 | 19.49% | 36.18% | 44.57% | 49.09% | y = 0.5077 − 0.5024e^(−n/2.3014), R^{2} = 0.99 |

15 | 17.95% | 32.52% | 39.13% | 44.38% | y = 0.4524 − 0.4461e^(−n/2.2711), R^{2} = 0.99 | |

5 | 14.80% | 29.20% | 35.96% | 38.93% | y = 0.4074 − 0.4056e^(−n/2.3252), R^{2} = 0.99 | |

50-2 | 25 | 17.49% | 37.61% | 46.67% | 50.46% | y = 0.5393 − 0.5400e^(−n/2.5156), R^{2} = 0.99 |

15 | 16.20% | 36.37% | 44.19% | 46.25% | y = 0.4928 − 0.4967e^(−n/2.3014), R^{2} = 0.99 | |

5 | 13.36% | 28.70% | 36.10% | 38.23% | y = 0.4103 − 0.4113e^(−n/2.4765), R^{2} = 0.99 |

Process | Deviator Stress (kPa) | F-T cycles | Fitting Equations | |||
---|---|---|---|---|---|---|

1 | 3 | 5 | 7 | |||

40-1 | 25 | 35.76% | 36.11% | 37.46 | 36.64% | y = 0.3674 − 0.3674e^(−n/0.2756), R^{2} = 0.99 |

15 | 31.38% | 32.72% | 30.59% | 30.85% | y = 0.3056 − 0.3010e^(−n/0.0224), R^{2} = 0.98 | |

5 | 25.94% | 25.06% | 23.80% | 26.24% | y = 0.2506 − 0.2503e^(−n/0.0080), R^{2} = 0.98 | |

50-2 | 25 | 33.09% | 34.33% | 34.76% | 32.45% | y = 0.3385 − 0.3385e^(−n/0.2630), R^{2} = 0.99 |

15 | 27.58% | 27.03% | 28.25% | 26.26% | y = 0.2718 − 0.2718e^(−n/0.0253), R^{2} = 0.99 | |

5 | 17.40% | 18.20% | 18.64% | 18.06% | y = 0.1830 − 0.1830e^(−n/0.3327), R^{2} = 0.99 |

Soil Types | Group | Fixed Factors | Sum of Squares | Variance | Mean Square | F Value | p Value |
---|---|---|---|---|---|---|---|

Unmodified SC | 40-1 and 50-2 | Confining pressure | 8447.723 | 1 | 8447.723 | 235.677 | <0.05(Significant) |

Deviator stress | 7943.085 | 2 | 3971.542 | 110.799 | <0.05(Significant) | ||

F-T cycles | 22731.808 | 4 | 5682.952 | 158.545 | <0.05(Significant) | ||

The modified SC | 40-1 and 50-2 | Confining pressure | 10362.438 | 1 | 10362.438 | 348.872 | <0.05(Significant) |

Deviator stress | 11361.213 | 2 | 5680.606 | 191.249 | <0.05(Significant) | ||

F-T cycles | 9734.423 | 4 | 2433.606 | 81.932 | <0.05(Significant) |

Soil Types | Factors | Porosity | Resilient Modulus | |
---|---|---|---|---|

Unmodified SC | Porosity | Pearson correlation coefficient | 1 | −0.979 |

Significance (2-tailed) | 0.021 | |||

N | 4 | 4 | ||

Resilient Modulus | Pearson correlation coefficient | −0.979 | 1 | |

Significance (2-tailed) | 0.021 | |||

N | 4 | 4 | ||

The modified SC | Porosity | Pearson correlation coefficient | 1 | −0.993 |

Significance (2-tailed) | 0.007 | |||

N | 4 | 4 | ||

Resilient Modulus | Pearson correlation coefficient | −0.993 | 1 | |

Significance (2-tailed) | 0.007 | |||

N | 4 | 4 |

Soil types | Factors | Mean Diameter | Resilient Modulus | |
---|---|---|---|---|

Unmodified SC | Mean diameter | Pearson correlation coefficient | 1 | −0.990 |

Significance (2-tailed) | 0.010 | |||

N | 4 | 4 | ||

Resilient Modulus | Pearson correlation coefficient | −0.990 | 1 | |

Significance (2-tailed) | 0.010 | |||

N | 4 | 4 | ||

The modified SC | Mean diameter | Pearson correlation coefficient | 1 | −0.951 |

Significance (2-tailed) | 0.049 | |||

N | 4 | 4 | ||

Resilient Modulus | Pearson correlation coefficient | −0.951 | 1 | |

Significance (2-tailed) | 0.049 | |||

N | 4 | 4 |

Soil Types | F-T Cycles | Porosity (%) | Mean Diameter (mm) | Small Pore Proportion d < 2 µm | Medium Pore Proportion 2 µm < d < 5 µm | Large Pore Proportion d > 5 µm |
---|---|---|---|---|---|---|

Unmodified SC | 0 | 0.94 | 2.04 | 83.51% | 16.49% | 0 |

1 | 4.35 | 2.28 | 73.24% | 25.91% | 0.85% | |

3 | 5.84 | 2.49 | 72.40% | 23.04% | 4.56% | |

5 | 7.11 | 2.71 | 66.59% | 25.70% | 7.71% | |

The modified SC | 0 | 2.67 | 2.76 | 74.30% | 23.77% | 1.93% |

1 | 7.66 | 3.18 | 68.66% | 28.28% | 2.46% | |

3 | 7.59 | 3.36 | 67.58% | 29.62% | 2.80% | |

5 | 8.39 | 3.42 | 64.29% | 32.67% | 3.04% |

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## Share and Cite

**MDPI and ACS Style**

Wei, H.; Zhang, Y.; Wang, F.; Che, G.; Li, Q.
Experimental Research on Resilient Modulus of Silty Clay Modified by Oil Shale Ash and Fly Ash after Freeze-Thaw Cycles. *Appl. Sci.* **2018**, *8*, 1298.
https://doi.org/10.3390/app8081298

**AMA Style**

Wei H, Zhang Y, Wang F, Che G, Li Q.
Experimental Research on Resilient Modulus of Silty Clay Modified by Oil Shale Ash and Fly Ash after Freeze-Thaw Cycles. *Applied Sciences*. 2018; 8(8):1298.
https://doi.org/10.3390/app8081298

**Chicago/Turabian Style**

Wei, Haibin, Yangpeng Zhang, Fuyu Wang, Gaofeng Che, and Qinglin Li.
2018. "Experimental Research on Resilient Modulus of Silty Clay Modified by Oil Shale Ash and Fly Ash after Freeze-Thaw Cycles" *Applied Sciences* 8, no. 8: 1298.
https://doi.org/10.3390/app8081298