Application Of Grouting Technology In Subway Tunnel In Saturated Sand Stratum

Quaternary soft stratum is common in urban underground space, among which fine silt, specially saturated fine silt, is normally unconsolidated, without cohesion, and relatively weak stability. To build urban subway tunnels by shallow tunnel construction in fine silt stratum being rich in underground water will easily cause construction accidents, such as water gushing, sand boiling and ground subsidence, etc. To ensure the stability of tunnelling working face and control land subsidence, and the successful progress of the construction, it's an indispensable important part to grout for water-blocking and consolidation in fine silt stratum rich in underground water in construction process.With the combination of shallow depth excavation grouting construction for Yizhuang training station rear line of Beijing subway Yizhuang line, this thesis has analyzed and researched saturated sand grouting mechanism and effect by theoretical analysis, field test, and laboratory test, etc., and a conclusion is reached as follows:(1) Retreating grouting process in sections for horizontal sleeve valve tubes applies internal stop-grouting plug to stop grout in sections. The stop-grouting effect is good, with repeated fine grouting with fixed area, pressure, and amount. The application of horizontal sleeve valve tubes by retreating grouting in sections on saturated sand stratum for pre-grouting water blocking and reinforcement will achieve good water-plug and reinforcement purpose and effect.(2) For water plugging and reinforcement on saturated fine silt stratum, modified water glass mix and TGRM microfine cement slurry can be applied with repeated grouting method. To grout under constant flow and set grouting period, Bingham fluid permeability and diffusion format could be applied to calculate extent radius of grout and theoretical grouting volume for single pore of modified water glass mix and TGRM microfine cement slurry with the water cement ratio as less than 1. In accordance with grouting construction record, actual grouting volume for single pore relatively conforms to theoretical values.(3) After grouting in saturated fine silt stratum, the stability and strength of find silt are both enhanced. After reinforcement, find silt stratum is with obvious netted grout veins. The whole grouting, water blocking and reinforcement process is the effect of complex grouting with the combination of filling infiltration, compaction and hydrofracture.The conclusion reached in this thesis by theoretical analysis, field test, and laboratory test, etc. is with definite practical guidance to similar constructions.