高压力下层间错动带残余强度特性和颗粒破碎试验研究

Residual shear behaviour and particle crushing of an infilled joint soil under high stress

针对某水电站层间错动带的原状样与重塑样,模拟现场地应力条件,在试验法向应力高达10 MPa条件下开展了反复直剪试验。试验结果表明:原状样峰值强度高于重塑样,但强度下降较快,二者残余强度趋于一致;此外,试样发生了大规模的颗粒破碎,采用颗粒相对破碎势Br量化重塑样剪切面附近区域与非剪切面附近区域颗粒破碎程度,对比发现,前者颗粒破碎程度高于后者,且破碎机制不同;剪切面颗粒破碎是高压力下残余强度包线非线性的根本原因:剪切强度的下降(残余强度与峰值强度的比值)与Br和S2(试验前后小于粒径<2μm颗粒含量的比值)呈线性关系,颗粒破碎导致的能量释放和不断产生的黏粒(<2μm)降低了剪切强度。

Multi-reversal direct shear test is conducted on the undisturbed and remolded infilled joint soils under in-situ stress where normal stress is as far as 10 MPa for test from a hydropower station.It is revealed that the peak shear strength is higher but decreases more rapidly for the undisturbed samples compared with the remolded ones;however,it seems the residual shear strengths tend to be the same.In addition,a large amount of particle crushing occurs,Br（relative particle crushing potential） is adopted to quantify the degree of particle crushing in the shear zone and the non-shear zone.The results show that the amount of particle crushing in the shear zone is larger than that in the non-shear zone;and the mechanisms of particle crushing are different for the two zones.Furthermore,particle crushing is considered as the main reason for the nonlinear relationship of the residual shear strength under high pressure;the decrease of shear strength（ratio of the residual shear strength to the peak shear strength） is linear with Br and S2（the ratio of clay fraction before test to the one after test for the shear zone）.It is indicated that the energy liberation and continuously generated clay fraction caused by particle crushing decrease the shear strength.