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利用高压三轴渗透试验系统,对某矿区深部的粗砂和细砂进行了高围压条件下的渗透试验。研究了同一水力梯度下渗透系数与围压的关系;同一围压下渗透系数与渗透水力梯度的关系;同一水力梯度下,围压逐级加载的渗透系数与一次加载的渗透系数之间的差别。结果表明,粗砂和细砂在同一水力梯度下渗透系数均随围压的增大而逐渐减小,在同一围压下,渗透系数会随渗透水力梯度的增大而逐渐增大;同一水力梯度下,围压逐级加载下的渗透系数明显小于一次加载条件下的渗透系数。根据围压与渗透系数的关系拟合出了两种砂样渗透系数与围压关系的数学表达式。为探究高围压下渗透系数变化的原因,研究了砂样试验过程中的体积变化和试验前后的粒度成分变化。结果表明,围压的施加过程伴随着试样的体积减小,相应的孔隙度减小,渗透系数降低;高围压条件下,砂土颗粒被挤碎成细颗粒,使得砂土的细粒含量增多,孔隙度减小,导致了砂土渗透系数的降低。
Using the high-pressure triaxial penetration test system, the deep grit and fine sand in a mining area were infiltrated under high confining pressure. The relationship between permeability coefficient and confining pressure under the same hydraulic gradient was studied. The relationship between permeability coefficient and infiltration hydraulic gradient under the same confining pressure was analyzed. The difference between the permeability coefficient of one stage loading and the permeability coefficient of one stage loading under the same hydraulic gradient . The results show that the permeability coefficient of coarse sand and fine sand decreases with the increase of confining pressure under the same hydraulic gradient. Under the same confining pressure, the permeability coefficient increases with the increase of hydraulic gradient. Gradient, the confining pressure of the gradual loading of the permeability coefficient was significantly less than the one time the loading conditions of the permeability coefficient. According to the relationship between confining pressure and permeability coefficient, mathematical expressions of the relationship between permeability coefficient and confining pressure of two sand samples are fitted. In order to explore the reasons for the change of permeability coefficient under high confining pressure, the change of volume during sand test and the change of particle size before and after the test were studied. The results show that the application of confining pressure is accompanied by the decrease of the volume of the sample, the decrease of the corresponding porosity and the decrease of the permeability coefficient. Under high confining pressure, the sand particles are crushed into fine particles, The content increases and the porosity decreases, resulting in the decrease of sand permeability coefficient.