Numerical implementation of a bounding surface model for unsaturated expansive clays
LI Jian1，ZHAO Chenggang1，LIU Yan1，FU Haiqing2
(1. Key Laboratory of Urban Underground Engineering of Ministry of Education，Beijing Jiaotong University，Beijing 100044，China；2. Earthquake Administration of Shandong Province，Jinan，Shandong 250014，China)
Abstract：An integration scheme based on the fully implicit Euler algorithm of backward integration has been proposed for a bounding surface model of unsaturated expansive clay. Two plastic deformation mechanisms in the modeling are defined，i.e. the loading-collapse mechanism and the microstructure mechanism. The coupling of stress-strain behavior to the hydraulic hysteresis is taken into account. Various situations are defined in a stress integral process according to the current stress state and the number of irreversible mechanisms active for mechanical modeling and hydraulic modeling. The trial solution is obtained by the Euler backward integration algorithm for each situation，and the true one is determined according to defined criterions. The performance of the model and the integration scheme were verified through the simulation of a series of published tests，including the cyclic suction tests and the triaxial tests. The stability and accuracy of the integration scheme are demonstrated through the comparisons of the calculated results of strain controlled tests for unsaturated expansive soils with different step sizes.
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2017, Vol. 36 
