挤压地层双护盾TBM与围岩相互作用影响因素分析

Analysis of influencing factors of interaction between double-shield TBM and surrounding rock in squeezing ground

为了研究LDP位移释放率、扩挖量、护盾锥度、护盾长度和侧压力系数等因素对双护盾TBM与围岩相互作用的影响,采用FLAC3D建立了三维TBM模型,在考虑护盾与围岩不均匀间隙的条件下研究了TBM作用下上述因素对围岩变形、接触挤压力大小及分布和护盾所受摩阻力的影响。同时定义了LDP曲线的位移释放率,得出应力释放率超过特定值时对LDP曲线释放率和TBM护盾阻力的影响显著,而且针对特定工程地质条件应做其敏感度的预分析;不均匀间隙自下而上逐渐闭合导致围岩与护盾逐渐发生接触,前后盾尾受力最为显著;前后护盾摩阻力及总摩阻力均与扩挖量呈线性递增关系,适当增加扩挖量可以有效减小护盾阻力;护盾摩擦力与护盾长度呈线性递增关系;当增加护盾锥度时,刀盘及前盾摩阻力缓慢增加,后盾摩擦力减小较为明显,护盾总摩擦力也减小;侧压力系数超过1.2时对刀盘、前盾及后盾上的摩擦阻力影响显著。以上研究成果对于进一步认识和研究TBM与围岩相互作用及后续预测卡机有着重要参考意义。

In order to study the interaction between double shield TBM and the surrounding rock affected by the LDP relax ratios, overcut, conicity of the shield, length of shield and lateral pressure coefficient, a completely three-dimensional TBM model using FLAC3 D has been adopted to investigate the features of the surrounding rock deformation, the contact force and the frictional resistance act on the shield based on the above influence factors considering the non-uniform gap between shield and surrounding rock. Moreover, the LDP curve relax ratios has also been defined in this paper. The simulation result has indicated that the LDP curve release rate and the resistance act on the shield of TBM have been affected significantly when the stress release rate exceeds a specific value, therefore a sensitivity analysis should be conducted under the specific engineering geological conditions. The nonuniform gaps between the shield and ground will gradually close from invert to crown and subsequently contact the shield surface and the most significant contact areas occur at the end of the front shield and rear shield. Both the friction force acting on the front shield and rear shield and the total friction force will increase linearly with the increasing overcut and appropriate increasing of overcut can effectively reduce the shield resistance; the total friction force acting on the shield will increase linearly with the increasing of the length of shield as well; with the increasing shield conicity, the friction force acting on cutterhead and front shield and the total friction force will increase slowly while the force acting on rear shield will decrease obviously. The frictional resistance acting on the front and rear shield is remarkable when the lateral pressure coefficient is more than 1.2. The above achievements have important reference significance for further understanding the interaction between TBM and surrounding rock and for forecasting TBM entrapment subsequently.