盾构隧道壁后注浆试验与浆液扩散机理研究进展

盾构隧道壁后注浆具有控制地层变形、确保管片受力均匀等作用,但壁后注浆施工中也常出现隧道上浮、管片破损、螺栓剪断等现象,壁后注浆效果与注浆施工参数的控制密切相关。为达到预期注浆效果,深入研究壁后注浆过程中浆液的扩散机理,提出合理的壁后注浆施工控制策略具有重要现实意义。基于目前国内外学者在盾构隧道壁后注浆浆液扩散机理方面所开展的工作,从现场实测、模型试验、理论分析3个方面进行梳理总结,分析现有研究的进展和不足。在现场实测方面,目前常用的监测手段是探地雷达无损检测法和埋设仪器法;室内模型试验包括整体模型试验和局部模型试验,整体模型试验主要用于模拟盾构掘进过程中的同步注浆施工,局部模型试验主要用于分析浆液固结变形以及压力消散过程;在理论分析方面,当前主要从盾尾间隙特征、浆液流体特性以及浆液-土体相互作用机理研究浆液扩散过程,浆液扩散过程可概括为充填、渗透、压密和劈裂4个阶段,充填注浆浆液的扩散模型主要是环形充填扩散和扇形充填扩散,渗透注浆浆液的扩散模型有球面渗透扩散和柱面渗透扩散,压密注浆浆液的扩散模型有球形压密扩散和柱形压密扩散,劈裂注浆过程很少考虑;在数值计算方面主要侧重于研究盾构壁后注浆对管片受力和地表沉降的影响。最后,分别从盾构隧道断面形式、理论模型的地层适应性、统一扩散理论模型、浆液扩散微观机理等方面展望了盾构隧道壁后注浆浆液扩散机理研究的发展趋势。

Review of Shield Tunnel Backfill Grouting Tests and Its Diffusion Mechanism

Backfill grouting in shield tunnels has the effect of controlling stratum deformation and ensuring uniform pressure on the segments. However, phenomena such as tunnel floating, segment damage, and broken bolt subject to shear force often occur during backfill grouting. The control of the slurry construction parameters is closely related to the effect of grouting. To achieve the expected grouting effect, it is of great practical significance to study the diffusion mechanism of the slurry during the backfill grouting process and propose a reasonable construction control strategy for backfill grouting. Based on the work carried out by scholars at home and abroad on the diffusion mechanism of grouting slurry, this paper summarizes three aspects, i.e., field measurement, model tests, and theoretical analyses, and analyzes the progress and deficiencies of existing research. In terms of field measurements, the current commonly used monitoring methods are ground penetrating radar (GPR) nondestructive methods and buried instrument methods. Indoor model tests include overall model tests and local model tests, while the overall model tests is mainly used to simulate the synchronous backfill grouting construction in the shield tunneling process, and the local model tests is mainly used to analyze the slurry consolidation deformation and pressure dissipation. In regard to theoretical analyses, researchers primarily study the slurry diffusion process from the aspects of the characteristics of shield tail gap, slurry fluid characteristics and the slurry-soil interaction mechanism. The slurry diffusion process can be summarized as four stages:filling diffusion, penetration diffusion, compaction diffusion and splitting diffusion. Theoretical models of filling diffusion are mainly ring-shaped filling diffusion and fan-shaped filling diffusion. Theoretical models of penetration diffusion include spherical penetration diffusion and cylindrical penetration diffusion. Theoretical models of compaction diffusion include spherical compaction diffusion and columnar compaction diffusion. The splitting diffusion process is rarely considered. Numerical simulation studies focus on the influence of pressure of grout acting on segment and ground settlement caused by shield tunnel grouting injection. Finally, this paper provides an outline of the developing trend of the diffusion mechanism of shield tunnel backfill grouting from aspects of cross-section form of shield tunnel, stratum adaptability of the theoretical model, unified diffusion model, and microscopic mechanism of slurry diffusion.