盾构切刀顺次破岩机制的数值模拟研究

Research on numerical simulation of sequential fragmentation mechanism of shield machine cutters

在对盾构切刀顺次破岩实际工况提出合理简化的基础上,从岩土细观角度出发,采用颗粒离散元法建立了切刀破岩的二维数值模型,研究了两把盾构切刀顺次作用下的破岩机制和影响因素,并通过试验对切刀破岩过程中切屑堆积现象及破岩力学特性进行了验证。研究表明,刀具尖端的破坏作用最为明显;切削岩石时切削力随着切削行程不断波动,水平切削力大于垂直切削力;不同于单刀切削,切刀顺次作用时前刀刮过的岩面留下了大量残余裂纹,使得后刀所受的切削力减小;从切削性能来看,随着切削深度的增加,岩石破碎块度不断增大,切削力和裂纹数迅速增加,说明切深与切削力密切相关;切削试验观测到了切屑在前刀面堆积和切削力的波动现象,与数值模拟具有较好的一致性。

From the perspective of microstructure of rocks, based on reasonably simplifying the actual tunneling condition, and by employing particle flow code （PFC2D）, two-dimensional numerical simulation of rock fragmentation of shield machine cutters is put forward. The mechanism of rock fragmentation under the situation of sequential cutting by two shield cutters is studied; its influential factors and corresponding experiments are carried out to verify the mechanical properties of rock fragmentation. Studies show that： first, it is the cutter＇s tip that is of the most destructive effect; second, the force of cutters fluctuates constantly along with the cutting process; and the horizontal cutting force is greater than the vertical cutting force; third, it is different between the single-pole cutting and sequential cutting since in the process of sequential cutting, the former cutter leaves many residual cracks, which decrease the cutting force of the following cutter; forth, from the aspect of cutting performance, rock cracks become bigger and cutting force become greater as cutters go deeper; so we can conclude that the cutting depth and the cutting force are closely related; last, the experimental situation of the accumulation of cracks and chips at the front of cutters and the wave phenomenon of cutting force in the experiment show great agreement with the results of numerical simulation.