Study On Mechanism Of Penetration And Diffusion Of Synchronous Grouting For Shield Tunnel In Sandy Stratum

Shield method with its speed of construction, environmental interference, construction safety advantages and widely used in the construction of urban subway tunnels and municipal pipelines(drainage, electricity, communications, etc.). Backfill grouting- as one of the three shield method, especially synchronous grouting, to control the ground settlement, prevention of tunnel leakage plays a decisive role.Backfill grouting is mainly by penetration diffusion in the sandy formations. With the rapid construction of urban subway, he research on the penetration and diffusion theory of synchronous grouting in shield tunnel is lagging behind the engineering practice. Therefore, it is necessary to systematically study the penetration and diffusion theory of the synchronous grouting slurry in the shield tunnel.In this paper, based on previous research, combined with the construction characteristics of synchronous grouting of shield tunnel, the paper adopts the method of literature investigation and theoretical research, to study the mechanism of grouting slurry diffusion mechanism:In view of different grouting material(single-slurry and double-slurry) and different slurry rheology(Bingham fluid, Newtonian fluid, power-law fluid), basing on the generalized Darcy’s law(capillary group theory), and consider the position of synchronous grouting, were established the Penetration and diffusion model of Shield Tunnel grouting, and combineing with model calculations formula, and analyzed the application scope and determination methods for the parameters of the formulas.According to the existing literature of grouting parameters, and based on a specific calculation case, the influence of grouting parameters(grouting pressure, grouting time and injection rate) and slurry properties(rheological index, water-cement ratio, grout time-varying characteristics and slurry self gravity stress) and the ground conditions(groundwater and formation permeability), upon the grouts diffusion radius and the total pressure on segments were discussed, and verifys it combined with the existing test results.Assumed slurry as suspension, summarizes the inject theory of single-slurry, and based on the theory of particle deposition, analysis the penetration-diffusion process model of shield tunnel grouting from the microscopic mechanism,and establishes the kinetics equation, continuous equation and particle deposition equation of the slurry penetration and diffusion considering the deposition of particles(i.e. the so-called "filtering effect").