基于驱替效应的盾构壁后注浆微观模型分析

Microscopic Model Analysis of Shield Tunnel Backfill Grouting Based on Displacement Effect

当盾构隧道位于水位线以下时,为了分析壁后注浆浆液驱动地下水体过程,基于毛细管组渗透理论,将浆液的渗流路径概化为毛细管,考虑牛顿流体浆液驱动地下水(牛顿流体)进行扩散,推导了半球形及柱形模型浆液渗流扩散半径计算式,并讨论了注浆压力、浆液水灰比、地层渗透系数的影响.研究结果表明:浆液扩散半径主要与注浆压力、渗透率、注浆时间、孔隙率、浆液和地下水黏度等因素有关,浆液水灰比对于浆液扩散半径影响最为显著,浆液的黏度由0.0047 Pa•s降至0.0019 Pa•s时,浆液扩散半径在注浆时间为1 h时降低幅度为46.7%,相同注浆条件下可增大水灰比来增大浆液扩散半径;浆液扩散半径随渗透系数的增大而增大,地层的渗透系数大小一定程度上反映了浆液扩散的难易程度;在计算出浆液扩散半径(浆液加固范围)的基础上提出了注浆压力下限值计算方法,用以指导盾构隧道壁后注浆工程施工.

When a shield tunnel under construction is below the water level,the shield backfill grouting slurry will drive the groundwater.In order to analyze this driving process,the seepage path of slurry in the soil is generalized to a capillary by capillary group penetration theory,the grout diffusion radius of hemispherical and cylindrical models are deduced considering the diffusion by Newtonian fluid slurry-driven water(Newtonian fluid),and the effects of grouting pressure,water-cement ratio,and formation permeability coefficient are discussed.Results show that the grout diffusion radius is mainly related to the grouting pressure,permeability,grouting time,porosity,and grout and groundwater viscosity.Especially,the grout water-cement ratio has the most significant effect on the grout diffusion radius.When the viscosity of the grout decreases from 0.0047 to 0.0019 Pa•s,the spreading radius of grout decreases by 46.7%at 1 h after grouting,indicating that the spreading radius of grout can be increased by adopting a higher water-cement ratio under the same grouting condition.Besides,the grout diffusion radius increases with an increase in the permeability coefficient,and the formation permeability coefficient reflects the difficulty of grout diffusion to a certain extent.Based on the calculation of grout diffusion radius(grout reinforcement range),a calculation method for the lower limit of the grouting pressure is proposed to guide the construction of backfill grouting of shield tunnel.