Research On The Dissipation Mechanism Of Grout Pressure During The Simultaneous Grouting Of Shield Tunnel Based On Time-dependent Behavior Of Viscosity

The most valuable advantage of shield construction technology is to minimize the disturbance of shield construction to surrounding rock and to reduce ground settlement.During construction,synchronized grouting technology can fill the gap of shield tail in time and actively control the stress release and deformation of surrounding rock in order to control the surface subsidence.The synchronous grouting-soil consolidation at shield tail is taken as the research object.The grouting pressure is taken as the main control index to do the following work:(1)The mechanism of pressure dissipation of synchronous grouting is studied:Based on Hooke's law and Darcy's law,the deformation law of grout-soil consolidation in short time during the diffusion of grout in the shield tail gap is studied.The consolidation and pressure dissipation formulas of slurry under single grouting hole condition are analyzed from two aspects of formation parameters(shear modulus and Poisson's ratio)and basic characteristics of slurry(slurry viscosity 0.011-031Pa·s).The consolidation and pressure dissipation formulas of slurry under the condition of single grouting hole are analyzed.On the basis of the above research results of single grouting hole,considering the different spatial distribution of grouting hole,the grouting filling and dissipation process is divided into two aspects:the circumferential direction and the longitudinal direction of the unit segment.The variation of grouting-soil consolidation thickness and its influence on the dissipation of grouting pressure under the condition of multiple grouting holes are studied.The influence of formation parameters and basic characteristics of slurry on circumferential pressure dissipation and longitudinal pressure dissipation under single-ring distance of shield tunneling is investigated.The results show that the dissipation law of synchronous grouting pressure of shield tunneling is a power-decreasing function considering the change of the thickness of grouting-soil consolidation.(2)Deformation law test of single grouting pore-soil consolidation under multivariate factors:According to the characteristics of shield tail grouting,such as bleeding rate,consistency,setting time and early strength,five main factors affecting the basic characteristics of grouting,i.e.water-cement ratio,binder-sand ratio,swelling ratio,fly ash ratio and content of early strength agent,were tested by uniform design method.According to the reasonable ratio of grouting material(water cement ratio is 0.8,0.9,1.0),different soil conditions(sand and clay)and grouting pressure(0.1 MPa,0.15MPa,0.2MPa),grouting volume deformation and formation pore water pressure change law are explored.Consolidation and pressure dissipation are investigated.The results show that the pressure dissipation law under test conditions is consistent with that under single grouting hole effect.(3)An engineering case study on the dissipation mechanism of grouting pressure in clay strata:Comparing with a metro project,different pressure dissipation time(23h,10h),different grouting pressure 0.075MPa(0.5 times),0.15MPa(1 times),0.225MPa(1.5 times),0.25MPa(1.7 times),different grouting volume(2.32m3(0.5 times),4.64m3(1 times),6.97m3(1.5 times)and 9.29m3(2 times)are explored.The influence of different early strength of grout(elastic modulus 2MPa(1 times),4MPa(2 times),6MPa)on consolidation and pressure dissipation of grout under multi-grouting holes is studied.Grouting pressure control index under clay layer is given by comparing ground subsidence with measured value.