粗粒含量对散体岩土颗粒破碎及强度特性试验研究

Experimental research on particle breakage and strength characteristics of rock and soil materials with different coarse-grain contents

明显的粒径分级和深部土的颗粒破碎是超高排土场的两个主要特征。基于改装后的大型两用直剪仪对不同粗粒含量的颗粒破碎和抗剪强度进行试验研究。颗粒破碎试验结果表明:垂直压力小于400kPa的情况下破碎率极小,在垂直压力大于400kPa时,随垂直压力的增大破碎率增加明显;粗粒含量小于46.0%时,相对破碎率较小,粗粒含量大于46%时,颗粒破碎率随粗粒含量的增加而明显增大;相对破碎率与垂直压力可用双曲线关系表示;长期浸泡于水中的土样颗粒破碎相当明显。剪切强度试验结果表明:在粗粒含量等于24%时,低垂直压力下的剪应力-应变曲线呈微软化或微硬化型,较高垂直压力下呈轻微软化型;在粗粒含量等于78%时,低垂直压力下其剪应力-应变曲线呈软化型,较高垂直压力下表现为轻微硬化型。较高垂直压力下的抗剪强度包线呈明显的非线性。当颗粒破碎率较小时,分别在垂直压力小于400kPa和大于400kPa时拟合的内摩擦角值变化不大;当颗粒破碎率明显增大时,垂直压力大于400kPa时的内摩擦角值明显低于垂直压力小于400kPa时拟合的内摩擦角值。

The significant particle size grading and particle breakage of deep soils are two major characteristics of super-high dumping sites. The particle breakage and shear strength of different coarse-grain contents were studied based on the refitted large-scale direct shear apparatus. The experimental results of particle breakage indicated that particle breakage index was very small when upright stress was lower than 400 kPa and increased obviously with the increase of upright stress that was higher than 400 kPa. The particle breakage index was very little at coarse-grain contents less than 46.0% and increased significantly according to the increasing of coarse-grained contents which was more than 46.0%. The relationship between particle breakage index and upright stress could be expressed by hyperbolic curve. The particle breakage of soil sample ,which was soaked for a long time in water, was remarkbale. The experiments studied on shear strength showed that the shear stress-strain curves were micro-softening model or micro-hardening model under low upright stress and were slight-softening model at higher upright stress when the coarse-grain contents was equal to 24.0%. At coarse-grain contents equal 78.0%, the shear stress-strain curves were softening model under low upright stress and slight-hardening model at higher upright stress. The shear strength envelope expressed nonlinear under higher upright stress. When the particle breakage index was small, the internal friction angles which were respectively fitted in the upright stress lower than and higher than 400 kPa changed little. With the obvious increment of particle breakage index, the internal friction angle of upright stress higher than 400 kPa was much smaller than that of upright stress lower than 400 kPa.