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岩体在卸荷作用下力学参数会发生劣化,导致承载力大幅减小。基于卸荷岩体力学理论,预制不同节理的砂岩岩样,在不同围压和卸荷量的条件下,对岩体的波速、应力应变特征、弹性模量、泊松比等参数进行试验测定。结果表明,节理岩体的波速与卸荷量关系呈阶段性变化。随着卸荷量的增加,波速衰减率明显增大;卸荷量越大,节理岩体的压密过程就越长;在卸荷量为0%和60%时,一定节理倾角的岩体,围压为5 MPa和10 MPa的弹性模量变化规律极为相似,并且弹性模量差值在10%以内,而围压为0 MPa和5 MPa的弹性模量相差在30%以上;在卸荷量和围压(都不为0)一定时,岩体的弹性模量与节理倾角呈类似正弦函数的变化规律;节理岩体的泊松比与卸荷量之间满足y=a+b(xc-1)关系。
The mechanical parameters of rock mass under unloading will deteriorate, resulting in a significant decrease of bearing capacity. Based on the mechanical theory of unloading rock mass, prefabricated sandstone samples with different joints were tested on the parameters of wave velocity, stress and strain, elastic modulus and Poisson’s ratio of rock mass under different confining pressures and unloading loads . The results show that the relationship between wave velocity and unloading amount of jointed rock mass changes in a stepwise manner. With the increase of unloading amount, the decay rate of wave velocity obviously increases. The larger the unloading amount is, the longer the compaction process of jointed rock mass is. When the unloading amount is 0% and 60% , The elastic modulus changes of confining pressure of 5 MPa and 10 MPa are very similar, and the difference of elastic modulus is within 10%, while the elastic modulus of confining pressure of 0 MPa and 5 MPa is more than 30% When the load and confining pressure are both 0 (zero), the elastic modulus and joint inclination of rock mass show a sinusoidal function. The Poisson’s ratio and unloading quantity of jointed rock mass satisfy y = a + b (xc-1) relationship.