我国贵州省天然斜坡上广泛分布着汞矿渣堆积体,危险性及危害性大,急需对其抗剪强度特性及机理进行深入研究.汞矿渣具有结构疏松、分选性差、粒径相差大且有弱胶结性等特点,选取贵州省丹寨县典型场地,开展汞矿渣颗粒分析试验及现场大型直剪试验.基于颗粒离散元PFC2D程序,进行了与现场直剪试验相应的数值试验,研究了抗剪切过程中的细观机理.现场与数值试验获得的曲线形态和抗剪强度参数接近,证实了数值试验的可靠性和高仿真性.试验结果表明:接近剪切应力峰值时,剪切带区域出现了明显的拉张接触力,而较远区域拉张接触力较不明显;随着剪切的进行,主动剪切盘的颗粒整体向右运动,而固定盘中与剪切带较近区域的颗粒也有向右运动的趋势;靠近剪切带区域出现了数个应力集中区,越靠近剪切墙应力越大;大颗粒对应力分布影响较大;固定盘中的应力集中区靠近剪切带,主动剪切盘应力集中区分布更广、受剪切作用影响更大.%Mercury slag accumulation are widely distributed on natural slopes in Guizhou province of China,which are of great danger and harmfulness,so it is in urgent need to study its shear strength characteristics and mechanism.Mercury slag has the characteristics of loose structure,poor sorting,different particle size and weak cementation.A typical site of Danzhai coun-ty,Guizhou province was selected to carry out the mercury slag particle analysis test and the field large-scale direct shear test. Based on the particle discrete element PFC2Dprogram,the numerical tests corresponding to the field direct shear test were car-ried out,and the meso mechanism of shear resistance was studied.The curves and shear strength parameters obtained by field test and numerical test are close to each other,which proves the reliability and high fidelity of the numerical test.Test results show that:When the shear stress is near the peak,the obvious tensile force appears near the shear zone,but the tensile force is not obvious in the far zone.As the shear proceeds,the particles of the active shear plate move to the right as a whole;while the particles of the fixed plate near the shear plate and the shear band also move towards the right.There are several stress concen-tration zones near the shear zone,and the stress is larger as it closes to the shear wall.Large particles have great influences on stress distribution.The stress concentration zone in the fixed plate is close to the shear band,and the stress concentration zone of the active shear plate is more widely distributed and more greatly affected by the shear action.
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