Effect of Axial Pressure on Lime-Treated Expansive Soil Subjected to Wetting and Drying Cycles

Chuxuan Tang,Zheng Lu,Hailin Yao

doi:10.1155/2019/3052932

Abstract

The impact of seasonal moisture variation on subgrade soil, including lime-treated expansive soil, has been investigated in many studies. However, when performing wetting and drying cycles, the effect of stress, which decides the behavior and mechanical properties of soil, is usually ignored. In this paper, the effect of axial surcharge pressure on the deformation and resilient modulus of lime-treated expansive soil subjected to wetting and drying cycles was investigated. A self-made apparatus was chosen to apply axial surcharge pressure and precisely control the variation of moisture content. The lime-treated specimens were placed in the self-made apparatus and then subjected to wetting and drying cycles under three different surcharge pressures. The results show that the axial surcharge pressure has a significant influence on the development of axial strain and resilient modulus. In particular, larger surcharge pressure induces accumulate irreversible shrinkage, whereas lower surcharge pressure tends to lead to irreversible swelling. On the contrary, the larger surcharge pressure leads to higher resilient modulus of the tested specimen after wetting and drying cycles.

Highlights

When subjected to variations of natural environment, pressure induced by upper road structure and soil has a significant effect on the behavior of subgrade soil [15, 16]
To simulate the realistic variation of moisture content, we chose 16.5% as the equilibrium moisture content (EMC) and conducted wetting and drying cycles in the range of moisture content comprised between 14.5% and 18.5%. e applying of wetting and dying cycles can be described as follows: (1) Use the wetting method to increase moisture content to 18.5% and wait for two days; (2) apply the drying method to decrease moisture content to 14.5% and wait for one day; and (3) use the wetting method to increase moisture content to 16.5% and wait for two days
Total axial strain of specimens after every step of wetting and drying process under different surcharge pressures is shown in Figure 4. e first wetting conducted to a significant swelling level, and the total axial strain decreased in the second wetting for all surcharge pressures. e total axial strain of specimens under 27 and 55 kPa progressively deduced in the following wetting stages, resulting in irreversible shrinkage

Summary

Natural soil

Plugged and placed in the closet for one day at 20°C to achieve uniform distribution of moisture in the specimen. One of the possible sources of error in this method could be the instability of axial pressure since the tension of the spring was related to the height of the apparatus which was changing with the variation of moisture content. Where S0 and T0, respectively, present the length and tension of the spring at natural state and S1 and T1, respectively, present the length and tension of the spring at working state For each stage, the last five cycles were chosen to determine the resilient modulus

Results and Discussion

Number of cycles

Conclusions