含有双组平行节理岩块裂纹扩展的DDARF分析

为了研究岩块中含有的双组平行节理在岩块受力过程中的开裂、扩展情况,以及扩展过程中对于岩块内应力的影响,使用DDARF模拟了含有双组平行节理的试块的单轴压缩试验,得出了双组平行节理角度为30°时试块最不容易发生破坏,节理角度为60°时试块最容易发生破坏的结论。     

Rock failure and its jointed surrounding rocks: A multi-scale grid meshing method for DDARF

DDARF (Discontinuous Deformation Analysis for Rock Failure) is an improved method of DDA (Discontinuous Deformation Analysis method), while there are only uniform grids in the original DDARF, and multi-scale grid meshing method cannot be realized. A multi-scale grid meshing method for DDARF is proposed to rock failure analysis, which balances off between the calculation accuracy and computation time. Simulations with multi-scale grid model and uniform grid model are established respectively, and compared with the laboratory tests; this multi-scale grid meshing method is applied to progressive failure process for jointed surrounding rock, and influence on crack propagation by the different lateral pressure coefficients K₀ of in situ stress is analyzed. It is concluded that this multi-scale grid meshing method for DDARF is feasible and the calculation accuracy can be improved with the same grid number. The proposed method is able to increase the computation efficiency by reducing the computation time when simulating underground cavern excavations, at the same time maintain the calculation accuracy. With increase of the lateral pressure coefficient K₀ of in situ stress, the main cracks propagating zones are moved gradually from both sidewalls of the cavern to the arch crown and floor. This method improves the DDARF to large projects, and it can analyze the progressive failure process of rock more effectively.     

DDARF中锚杆失效及收敛判据的研究

DDARF成功实现了模拟岩体裂纹萌生、扩展、贯通、破碎的全过程，但缺乏有效的锚杆失效判据和程序计算收敛判据。针对锚杆体的拉断破坏，采用最大拉应力准则，并在VC++平台下程序实现；针对锚杆体的滑脱失效，采用莫尔-库仑准则对灌浆体强度进行判断，并程序实现；针对程序计算的收敛判据，采用前后两步位移差与当前步位移比值小于某个极小值的方法，并程序实现，同时考虑了松弛因子对收敛的影响。将DDARF中锚杆的失效判据及程序计算收敛判据与室内试验进行对比，并应用到工程算例中。结果表明，DDARF中锚杆的失效判据和程序计算的收敛判据是有效的，能提高计算的效率和精度，为工程中特殊部位的支护提供参考；合理的松弛因子有助于程序计算的收敛，作者建议DDARF中松弛因子取值1.4～1.8较为合理。     

裂隙岩体表征单元体的确定及工程应用

以某水电站为工程背景,介绍了两种确定裂隙岩体REV的新方法:数字图像处理法和非连续变形DDARF法。依据水电站岩性差异、风化及卸荷程度,将围岩划分为若干工程地质区段并建立随机裂隙网络模型,研究尺寸效应对岩体力学参数的影响规律,获得了REV表征尺寸和等效力学参数;得到岩体的非线性强度准则,嵌入FLAC^3D对水电站开挖进行模拟,并监测关键点位移。结果表明:水电站围岩的抗压强度与围压成正相关;洞室开挖对厂房上下游中部和拐角处影响较大,应加强对这些部位的支护;关键点的位移数值结果与现场监测值基本吻合,误差小于5%。数字图像处理法和DDARF法为裂隙岩体REV的确定开拓了新思路,对复杂条件下地下洞室围岩的稳定性分析有广泛的应用前景。     

岩质边坡倾倒破坏的非连续变形分析

岩质边坡倾倒破坏存在块体的滑移、转动,及块体本身的折断。常规的离散元、非连续变形分析方法(DDA)虽然擅长处理块体的滑移和转动,但不能模拟连续体本身的破坏。然而通过在DDA方法中引入虚拟节理和真实节理的概念(即DDARF方法),用真实节理表征岩体中已经存在的天然节理、层面等,用起粘结作用的虚拟节理表征连续体。该方法可模拟连续体的变形及连续体的破坏。为此,首先对DDARF方法中的虚拟节理模型进行了着重的介绍。然后利用DDARF方法对龙滩边坡倾倒破坏的离心模型试验进行研究。研究结果表明,反倾块体的下部几乎没有明显的位移,而位于破坏面以上的部分产生明显的倾倒位移,导致在反倾块体的中部发生弯折破坏,形成贯通整个坡体的破坏面。数值模拟结果与离心模拟试验结果吻合得很好,验证了DDARF方法的有效性。