加轴压卸围压条件下岩石的力学特性与能量特征

Mechanical and energy characteristics of granites under unloading test

利用MTS815型压力试验机进行加轴压卸围压路径下花岗岩常规三轴卸载试验,研究加轴压卸围压路径下岩石的应力-应变全过程曲线、力学性质及能量特征。采用剪胀角描述岩石的扩容特性。研究结果表明:在卸围压过程中,侧向应变与围压先呈线性关系后呈非线性关系,且其增长速率明显大于轴向应变增长速率,表现出明显的侧向扩容;变形模量随围压卸载而逐渐减小,且随着初始围压的增大而逐渐增大;泊松比随围压卸载而不断增大,同一时刻点的轴向应变增量变化量度略大于侧向应变增量变化量;剪胀角随着初始围压增大而减小;基于能量原理获得岩石应变能随着围压的卸载呈逐渐增大的规律。

Through carrying out unloading experiments by increasing axial pressure while decreasing confining pressure on granites in tri-axial unloading test, the complete stress-strain curves, deformation characteristics and energy characteristics were obtained. The dilatancy angle was used to describe the dilatancy characteristics of rock.The results show that the relationship between lateral strain and confining pressure is firstly linear, and then nonlinear in the total stage of unloading confining pressure. Development of lateral plastic deformation is more rapid than that of the axial direction, which shows obvious lateral dilatancy. Deformation modulus decreases with the increase of the unloading confining pressure, and with the increase of the initial confining pressure, deformation modulus increases. The Poisson＇s ratio increases continually with the decrease of the confining pressure.The variation of axial increment strain in the same time is slightly greater than that of the lateral increment. The dilatancy angle decreases with the increase of the initial confining pressures.