Elastoplastic damage seepage-consolidation coupled model of unsaturated undisturbed loess and its application

摘要

The structural characteristic of unsaturated undisturbed loess has a significant impact on its mechanical properties. In this paper, based on the Barcelona basic model of unsaturated soil, an elastoplastic damage model (EDM) of unsaturated undisturbed loess has been developed, which considers the mesostructure evolutions in the loading and collapsing processes. By embedding the new EDM to the seepage-consolidation theory of unsaturated soil and combining it with the water-air migration laws of unsaturated loess, an elastoplastic damage seepage-consolidation coupled model (EDSCM) for the collapsible loess has been developed, which includes the effect of loess structure. Based on the new EDSCM, a new finite element program termed as unsaturated loess elastoplastic damage seepage-consolidation (ULEDSC) has been compiled. The developed program reflects the unique mechanical response of collapsible deformation of loess foundation during the water infiltrating process. Using the ULEDSC, the large-scale field-soaking test has been simulated for two periods, i.e., a 151-day period of wetting and a 251-day period of drying. The numerical results show that the propagation of wetting front is identical to a pumpkin-shaped zone. Due to the self-weight of collapsible loess and water, slow water filtration resulted in loess collapses and vertical displacement. The vertical displacement during the subsequent drying stage is mainly caused by the loess collapse and consolidation settlements of the shallow soil layer below the bottom of the test pit. The numerically simulated results from ULEDSC are in accordance with the field monitoring data, which also show the multi-field coupling response in the self-weight collapsible loess foundation during the initial wetting and subsequent drying periods. The new models and the finite element program could provide some scientific references for solving the engineering problems of self-weight collapsible loess in Midwestern China.