基于改进喷涌模型的土压/泥水双模盾构合理转换点研究

Study on Rational Switchover Point of EPB/Slurry Dual-mode Shield Based on the Improved Spewing Model

在高、低水位交替地层中掘进时,为兼顾水下盾构隧道施工的安全性与经济性而采用土压/泥水双模盾构机。但在实际工程中,两种模式的切换普遍过于盲目和主观,以致双模盾构机的效用无法充分发挥。以资阳地铁轨道交通工程宝台大道—苌弘广场盾构隧道工程为依托,先通过理论分析确定泥水/土压两种模式切换的原则及依据,后改进喷涌计算模型并结合采用COMSOL Multiphysics进行三维有限元模拟,得到可量化的土压模式盾构机喷涌风险计算和判别的方法以及螺旋输送机相关参数的影响规律。结果表明:经过现场验证,喷涌可以考虑为合理转换点的寻找原则,且改进喷涌模型计算的双模合理转换点明显优于以往的算法,能够更准确地划分出土压模式的风险区间,安全、经济和科学地指导双模盾构机进行模式切换;改进理论公式与三维模拟计算结果的差异均不超过30%且变化规律相似,螺旋输送机孔隙水流量与螺旋输送机筒体直径和螺旋节距呈线性正相关,与螺旋杆轴直径和螺旋输送机长度负相关。

For tunnelling in a stratum that contains both high and low water levels,the EPB/slurry dual-mode shield machine is used,in order to ensure both safety and economic efficiency of underwater shield tunnel construction.In practical works,however,switchover between the two modes can be often irrational and subjective,so the dualmode shield machine cannot be used to its full efficiency.In this paper,the shield tunnel from Baotai Avenue to Changhong Square,a rail transit project of Ziyang Metro,is used as the example.First,the principle and basis for switchover between the slurry and EPB modes is determined through theoretical analysis.Then the blowout calcula⁃tion model is improved,and three-dimensional finite element modeling is conducted by using COMSOL Multiphysics,so as to obtain the methods that are used to quantitatively calculate and identify the blowout risk of EPB shield ma⁃chine and the effects that are generated by the relevant parameters of the screw conveyor.As the results indicate:Ac⁃cording to field verification,blowout can be viewed as the principle for identifying the rational switchover point.The improved blowout model is clearly superior to the previous models in terms of the rational switchover point of the two modes,for it can be used to more accurately identify the risk range of the EPB mode and to guide mode switchover of dual-mode shield machine in a safe,economically efficient and rational manner.The difference between the result of the improved theoretical formula and that of the three-dimensional simulation calculation is no more than 30%and both results exhibit similar variation pattern.The pore water flow rate of screw conveyor is in positive correlation with the cylinder diameter and screw pitch of the screw conveyor and in negative correlation with the diameter of screw shaft and length of screw conveyor.