复合地层盘形双滚刀的破岩过程分析

Analysis of Rock Fragmentation Process with Double Circle Cutters in Mixed Ground

复杂环境中的隧道施工常遇到软硬不均或岩性变化大的复合地层,TBM的掘进施工优势凸显.但工程应用显示两类地层的岩土力学、地质特征等显著差异,复合地层的TBM隧道掘进与均质地层的破岩过程不同.为了提高复合地层TBM盘形滚刀的破岩效率,建立考虑裂隙网络扩展过程的双滚刀破岩三维离散元模型,模拟软硬不均复合地层中不同节理间距、节理倾角以及围压下的滚刀破岩过程,探讨对应的最优滚刀间距.其结果表明：节理对复合地层滚刀破岩是有利的,节理间距越小,岩体越破碎,破岩荷载越小,功耗也越小,破岩效率高;且节理倾向于软岩时,由于节理面的阻隔作用导致破碎区沿着节理界面延伸而无法贯通到临近岩层,软岩更易充分破坏;围压越大,则破岩荷载越大,功耗越大,则破岩效率相对较低.可见,复合地层的破岩过程中地层岩性及赋存环境的主导作用相对明显,进一步反映了复合地层不同于均质地层的滚刀破岩特征,这对深入研究复合地层TBM双滚刀破坏机理、滚刀优化设计及提高破岩效率具有重要的工程价值.

The mixed ground with soft-hard rocks or significant different property in rocks should often be encountered in tunneling construction process in complex environment,and TBM is superior to other machines in tunneling construction. However,there are obvious differences between the soft and hard rocks as for the rock physical properties and geological characteristics,so the rock fragmentation process is different in mixed ground and the homogeneous ground. For improving the rock fragmentation efficiency,a 3 D discrete element model considering crack propagation has been proposed to simulate the fragmentation process using the double cutters considering different joints spacing,joints dip angle and confined pressure and discussed the optimized cutter spacing. The results have indicated that joints are benefit for the TBM fragmentation process,and smaller joints spacing representing more broken rocks will result in smaller peak failure loads and specify energy,and the joints are inclined to the soft rocks,the soft rocks are more easily fragmented because of the joints preventing the crack propagation,and in addition greater confined pressure will result in greater peak failure loads and specify energy with lower rock fragmentation efficiency. Therefore,the ground properties and surrounding environment are the most important factors influencing on the rock fragmentation process to describe the difference of the fragmented mechanism in mixed ground and in uniform ground. These achievements are significant for deeply researching on the fragmented mechanism,cutter optimization design and improving rock fragmentation efficiency.