土石混合体边坡稳定性的三维颗粒离散元分析

Stability analysis of soil-rock mixture slope based on 3-D DEM

摘要:

为探究土石混合体边坡的稳定性和破坏机理,基于土工离心模型试验基本原理,结合已开发的不规则块石和土石混合体三维离散元建模方法建立土石混合体边坡细观结构的三维离散元模型.引入颗粒流强度折减法并提出基于能量演化的方法来判别边坡失稳破坏.利用提出的土石混合体边坡三维离散元建模方法和稳定性分析方法,分析不同块石含量、块石形状、空间结构、空间形态等因素对土石混合体边坡稳定性和破坏模式的影响,并揭示这些因素影响的细观机理.结果表明:随含石量增加,土石混合体边坡的安全系数逐渐增大；土石混合体边坡中呈现出多滑动面现象,且滑面较为曲折,具有明显的绕石特征,坡脚部位的部分大块石使得剪出口的位置发生明显的改变；随块石形状由球体、卵石到碎石,土石混合体边坡的安全系数逐渐增大；上覆堆积体相对较厚且坡度不是很大的二元结构边坡或一元结构边坡的破坏模式主要是堆积体内部发生的弧形滑动破坏,上覆堆积体厚度不大且基岩面相对平整的二元结构边坡的破坏模式主要是沿基-覆界面的整体平移滑动破坏；随土石混合体边坡空间形态由条带型、敞口型到锁口型,其安全系数逐渐提高,其中锁口型边坡具有显著的支撑拱效应,且含石量越大这种效应越明显.

Abstract:

To investigate the stability and failure mechanism of soil-rock mixture (SRM) slope, three-dimensional discrete element modeling method (3-D DEM) models for meso-structure of SRM slopes were constructed based on the basic principle of geotechnical centrifugal model test and the developed 3-D DEM for irregularly shaped rock blocks and SRM. Then, particle flow code strength reduction for slope stability analysis was introduced and a novel identification method for slope failure based on the energy evolution was developed. Finally, effects of rock block proportion, rock block shape, spatial structure, and spatial configuration on the stability and failure model of SRM slope were analyzed. Results show that the safety factor is increased with increasing rock block proportion. Multiple zigzag sliding surfaces by passing the rock blocks occurred in the SRM slope model, and some big rock blocks located in the slope toe caused an obvious shift of the shear outlet. The safety factor of the SRM slope is gradually increased when the rock blocks changed from spheres and pebbles to gravels. The failure mode of dual structural slope model with a thick overburden SRM and a low gradient or single SRM slope is mainly the cambered sliding that occurred within SRM, whereas the dual structural slope model with a thin overburden SRM and flat bedrock generally have wholly sliding along the bedrock surface. With the spatial configuration of SRM slope from strip type and outlet-open type to outlet-locked type, the safety factor is gradually increased, and the outlet-locked slope have significant arch-supporting effect, which is more obvious when the rock block proportion is larger.