复合地层中双护盾TBM与围岩相互作用机制三维数值模拟研究

Three-dimensional numerical simulation on interaction between double-shield TBM and surrounding rock mass in composite ground

为研究复合地层中双护盾TBM与围岩之间的相互作用机制,采用FLAC3D建立完整的TBM模型,研究复合地层中以下几种情况对TBM掘进时围岩变形及护盾所受接触力和摩擦阻力的影响:地层(1)为断面内上软下硬、上硬下软;地层(2)为沿洞线方向具有不同软岩长度;地层(3)为沿洞线方向具有不同软硬交替厚度。同时,将不均匀间隙作为函数引入护盾压力计算式中。得出地层(1)条件下受不均匀间隙的影响,围岩纵轴向剖面位移(LDP)曲线自下而上先后与护盾接触,接触部位主要位于隧道腰部及以下区域,接触压力主要集中在前、后盾中后方,且前盾尾部压力值最大;地层(2)条件下,护盾所受摩阻力随软岩长度的增加逐渐增大并最终趋于稳定;地层(3)条件下TBM前后护盾所受摩阻力呈周期性波动,其变化规律与围岩位移曲线变化频率基本对应。而且不论地层(2)或地层(3)中,围岩LDP曲线形态都不同于均匀地层。这些认识对于进一步研究复合地层中TBM与围岩的相互作用及预测卡机有重要意义。

3D numerical simulation with FLAC3 D,was carried out to investigate the interaction between double shield TBM and composite ground. The real TBM geometry and the non-uniform annulus gap between ground and TBM shield were considered. The characteristics of surrounding rock deformation,the contact force and the frictional resistance acted on the shield of TBM in composite ground were studied at the following conditions：（1） weak rock layer occurs along the ground depth;（2） soft rock occurs along the axial direction of tunnel;and（3） different lengths of soft and hard rock alternating in the longitudinal direction. Meanwhile,the non-uniform annulus gap was introduced to the calculation of contact force acting on the shield as a function. In case（1）,the curve of longitudinal displacement profile of surrounding rock came into contact with the TBM shield successively from bottom to top,which affected by the non-uniform annulus gap. The contact zone was mainly situated on the sidewall and below and the contact force was largely concentrated on the middle and tail end of both front shield and rear shield. The maximum magnitude of contact force occurred in the end of front shield. In case（2）,the frictional resistance acting on the shield was increased and finally kept in steady state with the increasing length of soft rock. In case（3）,the magnitude of the contact force acting on the shield was in periodic fluctuation and was basically in accordance with the variation of displacement. Moreover,the shapes of longitudinal displacement profile（LDP） curve in composite ground in cases（2） and（3） were absolutely different from that in homogeneous rock mass.