Experimental Study and Application of Lateral Swelling Stress of Expansive Soil

ZHANG Rui;ZHAO Xu;ZHENG Jian-long;LIU Zheng-nan

China Journal of Highway and Transport,2020,Vol 33,No. 09

Lateral swelling stress is the key parameter for the design and stability analysis of retaining structures. To obtain and characterize the variation of lateral swelling stress affected by swelling deformation, we developed a two-dimensional dilatometer for measuring lateral swelling stress and proposed a test method. A series of tests on compacted specimens of Baise expansive soil were conducted to investigate the change in lateral swelling stress under vertical and lateral swelling deformations, and thus the corresponding expressions were established. The test results show that the ratio of lateral swelling stress to vertical swelling stress is 0.42 under constant-volume immersion. Lateral swelling stress decreases due to increase in vertical swelling stress under complete lateral confinement. Vertical stress affects the lateral swelling stress indirectly by influencing the vertical swelling. The variation of reduction coefficient of lateral swelling stress D f due to vertical swelling with vertical stress ratio (the ratio of vertical stress to vertical swelling stress) can be characterized by a power function. When the vertical swelling remains unchanged, the lateral swelling stress decreases with the increase in lateral strain (lateral swelling ratio). Under this condition, the variation of reduction coefficient of lateral swelling stress R due to lateral swelling deformation with the lateral strain ratio (the ratio of lateral strain to final lateral strain) can also be characterized by a power function. A greater lateral swelling stress leads to a higher final lateral strain. For application, a case study on retaining wall in expansive soil under soaking was selected. By using current laboratory test results, the lateral swelling stress distribution along the depth of the retaining wall was calculated at rest and active conditions, respectively. The measured results verified the rationality of the calculation results. The proposed laboratory test method and the proposed expressions are simple and practical, which would provide accurate key parameters for the design and stability analysis of retaining structures in expansive soil.