Study On Diffusion Mechanism And Model Of Grouting Slurry In Weak Surrounding Rock Of Metro Tunnel

The density of population is becoming more and more larger with the rapid development of economy,leading the traffic becomes more crowded than before,and there is no doubt the subway is the most effective way in solving the traffic jam.However,there are many complicated questions about geology and surrounding environment inevitably when constructing the subway.The underground water have adverse influences in constructing subway interval tunnel when the subway go through the soil layer filled with plentiful of water,and even cause sand,gushing water than may lead the subway collapse.The above problems have huge adverse influence in civil and economy.It is one of the most effective way to strengthen the weak soil layer with plentiful of water by grouting in solving this problem.However,reinforcing the weak soil layer by grouting is a complicated concealed project.The study about process and diffusion mode of seepage are not scarce at present,which leads the grouting is not effective.Based on the theory and method of grouting,this paper investigates the mechanism and model of grouting diffusion by using theoretical analysis,numerical simulation and engineering,and acquires the parameters of grouting.The main contents and conclusions include:(1)Summary the rock characteristics and geological survey data of the weak rock layer in constructing the subway and acquire mechanical properties of the rock layer by laboratory tests.Analyze the seepage and diffusion of the slurry by using the physical interface of the two-phase Darcy law and summaring the influencing factors of the seepage diffusion distribution in the surrounding rock.Build diffusion model of grouting seepage under the circumstances of static water,moving water and different kinds of grouting.Compare the numerical results with engineers and apply the results in engineers,and acquire the reasonable parameters of grouting.(2)The stratum of Qingdao is a complicated stratum of soil – rock.A series of soil test results show that there are a lot of clay particles in sand layer,and its engineering properties are better than predicted.Based on the analysis of the seepage and diffusion of groundwater,the slurry is regarded as a viscousness water.On the basis of Darcy's law,the basic equations of the seepage and diffusion of the slurry in the formation are summarized,including the equations of motion,continuous Equation,equation of state,and further theoretical mathematic model of slurry diffusion.(3)According to the conclusion of soil tests and survey report,combined with the theoretical model of slurry seepage diffusion established,the numerical model of slurry seepage diffusion under different working conditions is established.And considering the different conditions,the multi-physics coupling software COMSOL Multiphysics is used to simulate the grouting reinforcement project,and the rule of slurry diffusion in different cases is obtained respectively.(4)Through the numerical simulation,the distribution law of seepage flow in the slurry is obtained under the action of single factor.And the seepage and diffusion law of the slurry in the water-rich formation is simulated.Under the condition of moving water,the area near the grouting hole is equal to zero,and the slurry is injected into the slurry.The distance of diffusion is about 1.5 m;the proportion of the injected slurry should be controlled about 1.30-1.32,the content of cement slurry is 30% of the solid content.(5)The parameters of grouting obtained by numerical simulation are combined with the relevant geological survey report to grouting,and the effect test and evaluation method of the grouting reinforcement project in the study area is analyzed,and the combination of drilling and geophysical Method to evaluate the accuracy of grouting reinforcement effect.This paper studied the slurry seepage and diffusion law of the grouting in the weak surrounding rock with plentiful of water in Qingdao subway tunnel,which considered the influence of the groundwater seepage on the slurry diffusion.At the last given the parameters of grouting which are available for the weak surrounding rock in Qingdao subway.