卸荷损伤节理岩体加载条件下力学试验研究

Experimental Research on Mechanical Properties of Unloading Damage Joint Rock under Loading Condition

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 at unloading condition will be deteriorated,resulting in a significant reduction of the bearing capacity.Based on the theory of rock mass mechanics,different joint sandstone samples were prefabricated and the wave velocity,the rock stress strain characteristics,elastic modulus,Poisson ratio and other parameters were measured under different confined pressure and unloading.The results show that the relationship between the wave velocity and unloading capacity of joint rock appears a periodical change.With the increase of unloading,the rate of velocity attenuation increases;the greater the amount of unloading,the longer joint rock compaction process is;for the rock mass with a certain joint,when the amount of unloading is 0%and 60%,the elastic modulus variation rule under the confined pressure of 5 MPa is very similar to the one under the confined pressure of 10 MPa,and the difference value is less than 10%;but the difference value of the elastic modulus is greater than 30% when the confined pressure is in the range of 0 MPa and 5 MPa;for a certain amount of unloading and confined pressure,the relationship between elastic modulus and dip angle of joint rock mass appears a trend similar to the sine function,and the relationship between Poisson ratio and unloading capacity of joint rock mass meet the equation y=a＋b（xc-1）.