Research On Permeation Grouting Reinforcement Effect Of Water-rich Sand Based On Bleeding Effect Of Cement Grout

With the development of China's subway entering large-scale construction period,controlling of disaster due to bad geological condition has become an important research topic.Subway tunnel often pass through the grade ? water-rich sand layer,which is one of the major sources of geological hazards affecting the safety of the subway construction.Thus tunnel collapse,inrush of water and sand,and other engineering disasters could be caused by construction disturbance and groundwater pressure.Permeation grouting is the most common method to control the geological disasters of the water-rich sand layer.In order to study the influence of bleeding effect of cement slurry on the effect of grouting reinforcement,this article comprehensively uses the research method of laboratory test,numerical simulation and field experiment to study the heterogeneous of the spatial distribution of grouted body properties caused by bleeding effect.The influence of factors such as water-cement ratio on the stability of tunnel after grouting is revealed,and the parameter control standard of grouting that matches water-rich sand layer is formed.The main work and innovation results are as follows:(1)A set of penetration grouting reinforcement effect test device considering the bleeding effect was designed.This device can measure the performance of grouted body in different spatial positions after the bleeding of cement slurry is finished.This device has the advantage of conducting multiple tests at the same time.(2)Uniaxial compressive strength and deformation modulus are used as performance indicators to evaluate the effect of grouting reinforcement,and three factors of cement slurry water-cement ratio,curing time and sand size are selected as the influencing factors of the performance of penetration grouted body.Carried out the test of the influence of cement slurry bleeding effect on grouting reinforcement effect.And the influence of water-cement ratio on the spatial distribution of strength of grouted body is revealed.(3)Based on the fluid-solid coupling calculation principle,a finite element calculation model that can analyze the stability of tunnel excavation after grouting reinforcement of the tunnel crossing the water-rich sand layer is established.From the distribution of plastic zone,seepage state after grouting reinforcement is revealed(4)Taking the vault settlement and tunnel water inflow of tunel as the evaluation indexes of tunnel stability,the necessity of considering the spatial inhomogeneity of sand grouting solid body's performance is verified.The influence of different water cement ratio of cement slurry and the thickness of grouting reinforced region on tunnel stability is studied,and the determination principle of water cement ratio and thickness of grouting reinforced region suitable for sand layer seepage grouting is proposed.(5)A grouting reinforcement project for a buried tunnel of Qingdao Metro Line 4 passing through a water-rich sand layer was selected as the supporting project.Field tests were carried out to study the grouting materials,grouting techniques,the thickness of grouting reinforced region,grouting amount and grouting end standard.An optimal control standard compatible with the grouting reinforcement water-plugging of water-rich sand layer is formed.