不同卸围压速率下三轴压缩细粒花岗岩力学特性

为了得到不同卸荷速率对于细粒花岗岩的卸荷力学性能的影响规律。采用恒轴压卸围压的试验方式进行室内三轴卸荷试验研究。试验设定卸荷速率分别为0.01 MPa*s^-1、0.02 MPa*s^-1、0.03 MPa*s^-1、0.04 MPa*s^-1、0.06 MPa*s^-1。最终试验结果表明：(1)卸荷速率对岩样环向变形比轴向变形影响大,当卸荷速率达到0.04 MPa*s^-1后,岩样的环向变形更加明显且呈现一定的应变软化特征。(2)应变—卸围压柔量随着卸荷速率的增加而增大,表明卸荷速率的增加对岩样的变形具有促进作用。当卸荷量达到30 MPa时,岩样的环向变形及体积应变—卸围压柔量明显增大,且卸荷速率越快增加越明显。(3)岩样的卸荷破坏形式以剪切破坏为主,随着卸荷速率的增加,岩样破坏的主裂缝与水平线的夹角有所减少,岩样的鼓胀现象明显,表明在卸荷速率较快的情况下,会使岩样产生较为明显的侧向变形。

Study on mechanical properties of fine grained granite under different unloading rates

In order to obtain the effect of different unloading rate on the unloading mechanical properties of fine granites. The three-axis unloading test was carried out by using the method of constant axial pressure unloading confining pressure. The unloading rate was selected as 0.01 MPa*s^-1, 0.02 MPa*s^-1, 0.03 MPa*s^-1, 0.04 MPa*s^-1 and 0.06 MPa*s^-1. Finally the experimental results showed that: (1) the unloading rate of sample affect the circular deformation than the axial deformation, when after unloading rate at 0.04 MPa*s^-1, toroidal deformation is more obvious and sample has certain strain softening characteristics. (2) strain - unloading pressure increases with the increase of unloading rate, indicating that the increase of unloading rate has a catalytic effect on rock deformation. When the unloading quantity reached 30 MPa, the ring direction and volume strain of the rock sample were significantly increased, and the faster the unloading rate increased, the more obvious it was. (3) The destruction of rock sample is mainly shear failure, with the increase of unloading rate, sample main fracture with the horizontal Angle decreased, the phenomenon of sample"s ballooning, under rapid unloading rate, sample produce evident lateral deformation.