胶结砂土力学特性的三维离散元简化分析

Simplified analysis of the mechanical behavior of cemented sand by three dimensional discrete element method

离散单元法(DEM)是一种基于非连续介质力学的数值模拟方法,能够有效地分析胶结颗粒材料的宏微观力学响应。本文通过三维离散元商业软件PFC3D,采用其自带微观胶结接触模型BPM,对不同胶结含量和不同围压下的胶结砂土进行常规三轴压缩试验模拟,以分析理想胶结砂土的宏微观力学特性。简化模拟结果表明:与同一初始孔隙比的无胶结试样相比,胶结试样具有更高的剪切强度,试验得到的应力应变曲线表现出明显的应变软化,体变曲线表现为剪胀性;随着胶结含量的增大,胶结砂土试样的峰值强度增大且软化、剪胀程度提高;而随着围压的增大,胶结砂土试样峰值强度增大、剪胀程度减小但软化程度不变。此外,试样的内摩擦角和黏聚力也受到胶结含量和围压的影响。

The discrete element method（DEM） is a numerical simulation method based on non -continu- ous medium mechanics, which can effectively analyze the macro and micro mechanical behavior responses of cemented granular materials. By using the three - dimensional discrete element commercial software PFC3D, a series of conventional triaxial compression tests for cemented sands with different cement contents and different confining pressures were simulated based on the microscopic cement contact model BPM to study the macro and micro mechanical behaviors of cemented sands. The results of simplified simulation showed that, compared with the pure sand specimen of the same initial void ratio, shear strength of the cemented sands was higher, the tested stress strain curve showed obvious strain softening, volumetric curve showed the dilatancy. The peak strength increased and the softening and dilatancy enhanced with the increases of cement content. With the increase of confining pressure, the peak strength increased and the dilatancy reduced; but the softening kept unchanged. In addition, the internal friction angle and the cohesion of the specimen were affected by the cement content and the confining pressure.