DEM Analysis of Dynamic Evolutions of Lateral Soil Arching in Sandy Soil

Abstract

For landslide mitigation, stabilizing piles are widely adopted in geotechnical engineering practice. The formation of soil arching between stabilizing piles can greatly mitigate the lateral spreading of sandy soil, and complementarily, evidence demonstrates that the sandy soil properties have a significant influence on the soil arching process. Thus, this paper focuses on investigating the lateral arching evolution behaviors in both dense and loose sands. A discrete element method (DEM) involving the servo-mechanism that plays a role in quantitatively controlling the translational velocity of selected walls when a desired force is to be applied or maintained was carried out to simulate the dynamic evolutions of the lateral soil arching process. The double-arch model is proposed to illustrate the end-bearing arch and frictional arch to analyze soil arching effects separately. Results indicate that the macrobehaviors and microbehaviors of lateral soil arching in dense and loose sands are initially distinct but ultimately similar. The arching mechanism is also illustrated by fabric analysis and coordination numbers. In general, the lateral arching evolutions in both dense and loose sands can be divided into three evolutionary stages as the loading displacement increases, which are similar to the strain-hardening and strain-softening phenomenon, respectively. Similarly, a unique arching process of forming-breaking-forming is identified by the use of particle trace. Moreover, multiple two-dimensional DEM models at different depths are superimposed vertically to study the three-dimensional soil arching. Based on the parametric studies, the loading velocity and pile spacing ratio have a preponderant influence on the development of soil arching, whereas the influence of the depth and confining stress is almost negligible. Additionally, the distribution of horizontal thrust has been determined by monitoring the stabilizing pile-based arching foot at different locations and the distribution of shear resistance is found to be approximately triangular. To mitigate the lateral spreading of sandy soil slopes, the stabilizing piles have been widely adopted in geotechnical engineering practice. The lateral spreading forces of soils behind the stabilizing piles will create various forms of soil arching effect, which is a favorable phenomenon for conducting cost-effective engineering design. In this study, we employed the two-dimensional discrete element modeling method to study the dynamic evolution of the lateral soil arching effect. The influence of the soil-structure relative movement, stabilizing pile spacing ratio, and confining stress for both dense and loose sands on the arching evolution and performance has been systematically studied. We found that the frictional arching was always negligible compared with the end-bearing arching accounting for the dominant role of double-arch model. The development of the lateral soil arching for both sands discloses three evolutionary stages, which conforms to the generic rule of strain softening for dense sand and strain hardening for loose sand. It is anticipated that the results of this study will eventually provide a certain reference value for the design of pile-reinforced earth slopes.