球齿滚刀作用下岩石裂纹的数值模拟与试验观测

 在对实际掘进条件做出合理简化的基础上，主要从仿真与试验2个方面对齿刀破岩机制进行研究。首先将Hertz弹性接触理论引入仿真，从而考虑刀具的初始应力分布对裂纹扩展的影响；然后利用基于2D离散法的UDEC软件建立TBM双刃球齿滚刀侵入砂岩的模型，并进行仿真分析；最后在原有线切割试验台的基础上设计观测试验。首次利用高速摄像仪捕捉到岩石崩裂及破碎的现象，并巧妙地使用普通数码相机不连续记录球齿下密实核的产生过程。该模型成功地模拟裂纹的生成与扩展，由仿真结果可知：随着侵深的增加，球齿底部承受压应力过大逐步出现密实核；球齿之间的侧向裂纹由于拉应力失效迅速扩展并趋于交汇，最终裂纹贯穿导致岩体破碎；破碎前刃侧出现的小块岩石崩裂现象是由拉应力失效引起的。仿真结果与实验室观测结果表明，研究成果和施工现场数据存有良好的一致性，可适用于浅地层TBM掘进机破岩机制的研究。

NUMERICAL SIMULATION AND EXPERIMENTAL OBSERVATION OF ROCK CRACKS UNDER ACTION OF SPHERICAL TOOTH HOB CUTTER

On the basis of reasonably simplifying the practical tunnelling conditions,the mechanism is mainly studied with simulation and experiment. First,in view of the effects of initial stress distribution of the cutters on crack propagation,Hertz elastic contact theory is introduced into the simulation. A model indenting into sandstone by TBM double-edged spherical tooth hob is established by using 2D discrete finite element simulation software UDEC. Based on the original linear cutting test-bed,an observational experiment is designed,in which the phenomena of rock crushing and bursting are captured by the high speed camera;and the producing process of compacting rock core is discontinuously recorded by the general digital camera skillfully. Crack production and propagation are successfully simulated. Results show that along with the increasing penetration,the compacting rock core is formed in the bottom of teeth for large compress stress. Side cracks between the teeth gradually propagate and tend to merge because of the tensile stress. The rock fragmentation is formed when the cracks are completely intersected. The phenomenon of bursting crack of small rock mass is caused by the tensile failure. The simulation results,which are suitable for studying the rock breaking mechanism of TBM in shallow-buried strata,have a good consistency with the experimental results and in-situ data.