卸荷路径下花岗岩变形与破坏特征试验研究

为深入研究花岗岩在卸荷路径作用下各变形阶段的应力特征值、变形参数和破裂前兆信息,选取甘肃北山花岗岩为研究对象,在不同初始围压下进行三轴卸荷试验。试验结果表明:(1) 随初始围压的增大,岩石特征应力值逐渐增大,受力模式由横向张拉作用转为张剪联合作用;(2) 弹性模量受初始围压大小的影响不大,泊松比随围压卸载而增大,弹性模量随围压的卸载而降低,均不是连续介质意义上的变形特征参数;(3) 在路径1作用下,因岩石侧向扩容剧烈,从而粘聚力较小;而路径2作用下岩石受张性破裂影响,导致破裂面粗糙,因此内摩擦角较高;(4)能量累计数随时间由缓慢增长转为加速增长的时间转折点可作为岩石在卸荷作用下出现宏观裂隙、导致完全破坏的监测参量。

Experimental Study on the Deformation and Failure Characteristics of Granite under Unloading Paths

In order to make deeper study on the stress eigenvalue,deformation parameters and rupture precursors of granite during various deformation stages under unloading paths,the Gansu Beishan granite,was selected as the research object.Under the different initial confining pressure,the three-axis unloading test was carried out.The test results show that with the increase of initial confining pressure,the characteristic stress value of rock gradually increases,and the stress mode changes from transverse tension to tension shear interaction.The deformation modulus is not affected by the initial confining pressure and the Poisson's ratio increases with the unloading of confining pressure,while the elastic modulus decreases with the unloading of confining pressure,these are not the deformation parameters in the sense of the continuous medium.Under the condition of the path 1,the cohesion is small because of the lateral dilatancy of rock.While under the path 2,the rock is affected by tensile fracture,resulting in the roughness of the fracture surface,so the internal friction angle is higher.The turning point of the cumulative number of energy accumulations from slow growth to accelerated growth over time can be used as a monitoring parameter for macroscopic fractures and complete destruction of rocks under unloading conditions.