基于驱替效应的砂卵石地层盾构壁后注浆渗透扩散机理研究

In the shield tunnel backfill grouting in high permeation sand gravel stratum, permeation and diffusion are the main movement forms of the grout. The sand gravel stratum usually contains plenty of underground water, and the grout can drive away the free water in pore and replace it under the grouting pressure, which is the “displacement effect”, so the movement of grout in this kind of stratum can’t be simply regarded as the seepage of the single liquid. However, most researches on the shield backfill permeation grouting at present are based on the ideal hypothesis of single liquid, and because of the complexity of the internal structure, the diversity of the grout and other issues, the research of backfill permeation grouting has obtained slow progress. Based on the applicants’ pre-study of backfill grouting, by means of theoretical analysis and similarity model test, assisted by numerical simulation and field test, an in-depth research will be conducted on the following topics considering the displacement effect of grout on underground water: diffusion mechanism of grout with different flow types, formation mechanism and calculation method of grout pressure of backfill grouting and buoyancy load, dissipation mechanism of grout permeation pressure after grouting and coaction mechanism of grouting body and segment structure. The research results can provide theoretical guidance for the design and construction control of the backfill grouting of shield tunnel, and the design of the segment structure.

盾构隧道壁后注浆浆液在高渗透砂卵石地层中的运动形式主要以渗透扩散为主，由于该地层中常赋存大量地下水，因此浆液在其中的运动并不能简单归结为单一液体的渗流，而是在注浆压力的驱动下驱赶地层孔隙中的自由水并取而代之，即所谓“驱替效应”。然而，目前针对盾构隧道壁后渗透注浆的研究大多建立在单一流体的理想假设下，且由于砂卵石地层内部构造的复杂性、浆液的多样性等问题，壁后渗透注浆研究进展一直较为缓慢。本研究拟在申请者前期壁后注浆的研究基础上，采用理论分析、相似模型试验，并辅以数值模拟、现场测试等手段，基于浆液对地下水的驱替效应，对不同流型浆液的扩散机理、壁后注浆浆液压力及浮力荷载产生机理与计算方法、注浆结束后浆液渗透压力消散机理，及注浆体与管片衬砌结构的共同作用机理等议题开展深入研究。研究成果可为盾构隧道壁后注浆设计与施工控制，及管片衬砌结构的设计提供理论指导。

本基金项目通过实例调研、理论分析、模型试验以及数值分析，研究了高渗透砂卵石地层盾构壁后注浆浆液扩散机理，分析了浆液驱替效应、地层滤过效应对浆液扩散过程的影响，提出了适用于不同类型地层的壁后注浆浆液配合比及评价方法。对全国范围内盾构隧道同步注浆浆液材料参数进行调研，得到各类地层浆液配比选用范围参考表，通过浆液配比正交试验探究了各浆液配比因素对浆液性能的显著性影响，并设计了盾构隧道壁后注浆一维扩散试验，分析了浆液在地层中扩散特征，该方法可用于评估浆液与地层的适配性；基于盾构隧道壁后注浆浆液对地下水的驱替效应，针对不同流变性能浆液的球面扩散和柱面扩散模型，利用渗流力学相关理论，推导了高渗透砂卵石地层盾构壁后注浆浆液扩散规律表达式，讨论了模型中渗透相关参数对浆液扩散距离及管片压力的影响，基于分形理论建立了各流型浆液的渗透和压密扩散模型，提出了注浆压力上、下限值的计算方法，分析了非均匀孔隙及浆液渗滤效应对浆液扩散过程的影响；依托实际工程对黄土地层盾构隧道二次注浆的临界注浆压力进行分析，基于SPH理论模拟分析了同步注浆压力对管片衬砌结构变形的影响，基于统一强度准则提出了黄土地层盾构隧道二次注浆的临界压力计算公式。