位移释放率对双护盾TBM护盾压力的影响研究

Impact of longitudinal displacement profile relaxation on contract force acted on double shield TBM in squeezing ground

为了研究隧洞纵向位移(LDP)释放率对双护盾隧洞掘进机(TBM)围岩变形及护盾压力的影响,在FLAC3D中采用应力释放法对LDP曲线实现了较好的控制,并指出采用计算时间步控制的缺陷,在考虑护盾与围岩之间不均匀间隙情况下,详细分析了应力释放率对TBM掘进中围岩LDP曲线变化规律、护盾所受挤压力及围岩塑性区的影响。得出了以下结论:(1)不同岩体力学参数下,LDP曲线受应力释放率的敏感程度不同;(2)随着应力释放率的逐渐增加,围岩LDP曲线特征及与TBM护盾相互接触的部位有所不同,TBM护盾接触挤压力和所受摩擦阻力逐渐增大;(3)护盾外围塑性区的形状与应力释放率和护盾与围岩之间的不均匀间隙有关,当在较大的应力释放率下,塑性区呈现自上而下逐渐减小的特征。

A complete 3D numerical simulation, by using FLAC^3D, is developed to investigate the influence of longitudinal displacement profile （LDP） relaxation on ground deformation and contact force acted on the shield in squeezing ground excavated by a double shield tunneling boring machine （TBM）. The shapes of LDP curves using the stress relaxation are well controlled and the defect of control method by time step is represented in comparison with the stress method. The model is based on the real geometry and considers the nonuniform gap between the shield and ground. The characteristics of the LDP curves, the contact force and the plastic zone on the cross-section of tunnel are studied. Some useful conclusions are drawn as follows： 1） The sensitivity of LDP curves to the stress relaxation is not uniform for various rock mass parameters. 2） The contact pressure and frictional resistance acted on the shield increase gradually with the increasing stress release rate, and the corresponding behavior of LDP curve of ground and the contact area on the shield are also different. 3） The shape of plastic zone outside the shield is closely related to the stress release rate and the non-uniform gap between shield and ground. The plastic zone will gradually reduce from top to bottom when the stress release rate reaches a relatively large value.