富水粉细砂层盾尾同步注浆滤饼生长速率研究

Study on the growth rate of filter cake of shield tail synchronous grouting in water rich fine sand layer

受富水粉细砂层渗滤效应影响,盾尾同步注浆过程中浆液会在盾尾处生成滤饼从而阻碍地下水对浆液的冲蚀。为探究富水粉细砂层盾尾同步注浆滤饼生长速率与水灰比及注浆压力之间的关系,基于圆管束理论、动量守恒定律、质量守恒定律,考虑地层渗滤效应及浆液黏度时效性影响,建立滤饼生长速率理论方程,并定义滤饼生长平均加速度ar衡量滤饼生长速率变化快慢,自主研发一维渗透柱试验装置,比较不同水灰比及注浆压力下滤饼生长速率试验值与理论值,以验证理论方程的合理性。结果表明:随着注浆时间持续进行,滤饼生长速率曲线呈先加速增长再缓慢增长趋势。水灰比一定时,注浆压力越大,滤饼生长速率及厚度越大,滤饼生长持续时间越短。注浆压力一定时,水灰比越小,滤饼生长速率及厚度越大,滤饼生长持续时间越短。工程实际中应适当增大注浆压力并减小浆液水灰比,以确保滤饼在迅速生成的同时并具有一定的厚度。通过比较滤饼生长平均加速度试验值及理论值可以推断出,以0.4 MPa的注浆压力在孔隙率为0.36的富水粉细砂层中进行盾尾同步注浆时,水灰比控制在0.8~0.85范围内可确保滤饼能够迅速生成,从而使浆液能够充分填充盾尾间隙,减小地表沉降。研究成果对富水粉细砂层盾尾注浆施工具有一定的工程意义。

Affected by the infiltration effect of the water-rich fine sand layer,the slurry generates a filter cake at the tail of the shield during the synchronous grouting process of the shield tail,thereby hindering the erosion of the slurry by groundwater.In order to explore the relationship between the growth rate of filter cake and watercement ratio and grouting pressure in shield tail synchronous grouting in water-rich fine sand layer,based on the theory of circular tube bundle,the law of conservation of momentum and the law of conservation of mass,the theoretical equation of filter cake growth rate was established by considering the effect of formation percolation and the timeliness of slurry viscosity,and the average acceleration ar of filter cake growth was defined to measure the change rate of filter cake growth rate.A one-dimensional permeation column test device was developed independently.The rationality of the theoretical equation was verified by comparing the experimental value of filter cake growth rate with the theoretical value under different water-cement ratio and grouting pressure.The results show that as the grouting time continues,the filter cake growth rate curve first accelerates and then slowly increases.When the water-cement ratio is constant,the greater the grouting pressure,the greater the growth rate and thickness of the filter cake,the shorter the growth duration of the filter cake;when the grouting pressure is constant,the smaller the water-cement ratio,the greater the growth rate and thickness of the filter cake,and the shorter the growth duration of the filter cake;in engineering practice,the grouting pressure should be appropriately increased and the slurry water-cement ratio should be reduced to ensure that the filter cake is rapidly generated and has a certain thickness.By comparing the test value and theoretical value of the average acceleration of the growth of the filter cake,it can be inferred that when the grouting pressure of 0.4 MPa is used for synchronous grouting of the shield tail in the water-rich fine sand layer with a porosity of 0.36,the watercement ratio is controlled in the range of 0.8~0.85 to ensure that the filter cake can be quickly generated,so that the slurry can fully fill the shield tail gap and reduce the surface settlement.Research results on water-rich powder.The research results have some engineering significance for shield tail synchronous grouting in waterrich fine sand layer.