干湿循环下炭质泥岩软弱夹层剪切强度及渗透性演化规律研究

Study on the evolution law of shear strength and permeability of soft and weak interlayers of carbonaceous mudstone under dry and wet cycles

针对云南某露天矿边坡中的炭质泥岩软弱夹层,开展了室内干湿循环加速模拟试验、直接剪切试验和变水头渗透试验,研究了干湿循环作用下炭质泥岩软弱夹层抗剪强度和渗透性的演化规律,分析了循环次数对抗剪强度和渗透系数的影响,结果表明:干湿循环对炭质泥岩软弱夹层的抗剪强度影响显著,不同竖向荷载下,抗剪强度劣化趋势基本相同;随着干湿循环次数的增加,其内摩擦角基本不变,但黏聚力显著减小,且在干湿循环1次时黏聚力减幅最大,2~7次时黏聚力劣化速率较快,在干湿循环超过7次时,炭质泥岩软弱夹层的黏聚力变化速率趋于平缓,最终拟合得出黏聚力与干湿循环次数之间的指数函数关系模型;炭质泥岩软弱夹层的渗透系数和干湿循环次数呈正相关,循环次数在0~4次时渗透系数变化较为平缓,4次之后渗透系数显著增大,在7次循环时达到最大值,之后渗透系数基本不变。研究结果可为类似矿山边坡软弱夹层的强度和渗透系数预测提供参考。

Aiming at the soft interlayers of carbonized mudstone in the slope of an open-pit mine in Yunnan province,accelerated simulation test under dry-wet cycle indoor,test of direct shear and test of variable head permeability were carried out to study the evolution law of shear strength and permeability of the soft interlayers of carbonized mudstone under the action of dry-wet cycle,and the influence of cycle times on shear strength and permeability coefficient was analyzed.The results show that the dry-wet cycle has a significant effect on the shear strength of weak interlayers of carboniferous mudstone,and the deterioration trend of shear strength is basically the same under different vertical loads.With the increase of the number of dry-wet cycles,the internal friction angle is basically unchanged,but the cohesion decreases significantly,and the cohesion decreases the most when the dry-wet cycle is 1,and the cohesion deterioration rate is faster when the dry-wet cycle is 2~7.When the dry-wet cycle is more than 7,the cohesion change rate of the weak interlayer of carbonaceous mudstone tends to be flat.Finally,the exponential function model between the cohesion and the number of dry and wet cycles was fitted.Permeability coefficient of weak layers in carbonaceous mudstone is positively correlated with dry-wet cycling times.Permeability coefficient changes gently when cycling times are 0~4,increases significantly after 4 cycles,reaches maximum value when cycling times are 7,and then permeability coefficient basically remains unchanged.The results of the study can provide reference for the prediction of the strength and permeability coefficient of the weak interlayer in similar mine slopes.