循环载荷对岩石节理宏细观剪切特性影响的模拟研究
Numerical investigation on the effect of cyclic loading on macro⁃meso shear characteristics of rock joints
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摘要: 岩石节理在循环载荷作用下会不断的滑移和闭合,导致其承载性能不断劣化,进而影响岩 体工程的稳定性。 为探明循环载荷作用下节理的剪切特性,首先开展了节理剪切试验以标定模拟 中的物理力学参数和确定循环载荷的特征参数,然后采用基于 FISH 语言二次开发的循环剪切加 载实现方法,进行了不同加载幅值(1.5、1.7、1.9、2.1 和 2.3 MPa)、不同加载频率(0.1、0.5、1.0、1.5 和 2.0 Hz) 等循环剪切载荷作用下的粗糙节理剪切数值模拟,研究了岩石节理的宏细观剪切特性以 及循环载荷特征参数对节理剪切特性的影响。 结果表明:随着剪切载荷的循环加卸,节理表面损伤 会导致节理剪切应力-剪切位移曲线出现滞回效应。 循环剪切初期滞回环较小且分布密集,后期 滞回环较大且分布疏松。 剪切过程中节理的裂纹分布和接触力分布与节理表面的粗糙体相关,剪 切初期裂纹和高接触力大都集中在二阶凸起上,随着二阶凸起破坏逐渐作用到一阶凸起上,一阶凸 起破坏后节理发生失稳破坏。 节理剪切位移的增长趋势与累计裂纹数量的增长趋势总体一致。 剪 切初期仅有少量裂纹在应力峰值附近产生,而后期裂纹产生时对应的应力范围和裂纹数量都显著 增加。 加载幅值越大,每个循环内产生的节理损伤越多,节理剪切位移也越大,达到相同目标位移 所需的循环次数与加载幅值呈反比。 加载频率越大,每个循环内节理产生的损伤越少,节理剪切位 移也越小,达到目标剪切位移所经历的循环次数与加载频率呈正比。 加载频率越低,加速阶段越 短,节理发生失稳破坏越突然。Abstract: Rock joints will continuously slip and close under cyclic loading,leading to continuous deterioration of their bearing properties,which in turn affects the stability of the rock engineerings.In order to investigate the shear characteristics of rock joints under cyclic loading,firstly,joint shear tests were carried out to calibrate the physical and me⁃ chanical parameters in the simulation and to determine the characteristic parameters of cyclic loading.Then,a cyclic shear loading implementation method based on FISH language was used to simulate the shear of rough joints under cy⁃ clic shear loading with different loading amplitudes ( 1.5,1.7,1.9,2.1 and 2.3 MPa ) and loading frequencies ( 0.1, 0.5,1.0,1.5 and 2.0 Hz ).The macro⁃meso shear characteristics of rock joints and the effect of cyclic loading charac⁃ teristic parameters on the shear properties of joints were investigated.The results show that with the cyclic shear loading and unloading,damage to the surface of the joints can lead to the hysteresis effect in the shear stress⁃shear displace⁃ ment curve of the joints.The hysteresis loops are small and densely distributed at the early stage of shear and large and loosely distributed at the late stage.The crack distribution and contact force distribution of the joints during shearing are related to the surface roughness of the joints.In the early stage of shear,the cracks and high contact force are most⁃ ly concentrated on the second⁃order bulge,and with the destruction of the second⁃order bulge,the shear force gradually acts on the first⁃order bulge, and after the destruction of the first⁃order bulge, the joints are destabilized. The growth trend of the nodal shear displacement is generally consistent with the growth trend of the accumulated crack number.Only a small number of cracks were generated near the peak stress at the early stage of shear,while the stress range and the number of cracks corresponding to the later stage of crack generation increased significantly.The larger the loading amplitude,the more joint damage is generated within each cycle,and the greater the joint shear dis⁃ placement.The number of cycles required to achieve the same target displacement is inversely proportional to the load⁃ ing amplitude.The greater the loading frequency,the less damage produced by the joint in each cycle,and the smal⁃ ler the joint shear displacement.The number of cycles experienced to reach the target shear displacement is proportion⁃ al to the loading frequency. The lower the loading frequency, the shorter the acceleration phase, and the more abrupt the destabilization of the joint.