基于体裂隙强度的岩体代表性单元体尺度确定方法

The Method of Representative Elementary Volume of Fractured Rock Mass Based on Volume Fracture Degree

岩体由于各种结构面表现出不连续性、非均质性、各向异性等复杂特性,使得岩体尺寸效应成为岩体力学研究的重点和难点,尺寸效应研究关键在于确定岩体代表性单元体尺度。根据3GSM现场测量和室内试验,建立了9组不同尺度裂隙三维网络模型,计算体裂隙强度,发现体裂隙强度随尺寸变化出现波动,根据波动大小分为离散区(1~4 m)、过渡区(4~8 m)和均质区(8~20 m)。基于三维块体离散元软件3DEC,依据裂隙网络模型建立9组裂隙岩体模型,进行常规三轴压缩数值模拟研究。结果表明:裂隙岩体表现出明显尺寸效应,即随着岩体尺寸增大,各力学参数先减小后稳定,代表性单元体(REV)尺度为8 m。最后,引入体裂隙强度反映裂隙对尺寸效应的影响,并与REV尺度对比,发现通过体裂隙强度表征裂隙岩体尺寸效应规律是可行的。

Because of the discontinuity,heterogeneity,anisotropy and other complex characteristics of various discontinuities in rock mass,the size effect of rock mass has become the focus and difficulty of rock mass mechanics research,The key to the size effect research is to determine the representative elementary volume.Based on 3GSM and laboratory test,nine groups of random fracture three-dimensional network models with different sizes are established,and the volume fracture degree is calculated.It is showed that the volume fracture degree changes with the size.According to the fluctuation,it is divided into discrete area(1~4 m),transition area(4~8 m)and homogeneous area(8~20 m).Based on 3D block discrete element software 3DEC,nine groups of fractured rock mass models are established according to the fracture network model,and the conventional triaxial compression numerical simulation research is carried out.The results show that the fractured rock mass shows obvious size effect,that is,with the increase of rock mass size,the mechanical parameters of rock mass first decrease and then gradually stabilize,and the characterization unit volume(REV)size is 8 m.Finally,the volume fracture degree is introduced to reflect the influence of fracture on size effect,and compared with REV,it is found that it is feasible to characterize the size effect law of fractured rock mass by volume fracture degree.