Study On Penetration,Reinforcement And Deterioration Mechanism Of Grouting In Sand Layer Under Seawater Erosion-Seepage And Its Application

China's marine underground engineering has entered a period of large-scale construction.The construction and operation of underground projects under the marine environment such as subsea tunnels and offshore subways have flourished.Bad geology is one of the important threats to engineering construction and operation.The water-rich sand layer is a common stratum of marine underground engineering.Due to its low cementation strength and poor self-stability,it has become one of the important geological disasters affecting the safety of the subsea tunnel construction.Grouting is the most common method to solve geological disasters in water-rich sand layers.However,the marine environment and the terrestrial environment are quite different.The seawater ion erosion and seepage will lead to a significant decrease in grouting and solids,and reduce the physical and mechanical properties of grouting and solids.The maintenance of grouted body performance is the guarantee to the safe operation of the tunnel long-life cycle in the marine environment.In this paper,the most common osmotic grouted body model in the water-rich sand layer has been quantitatively described through theoretical analysis,numerical simulation,laboratory test,simulation test,and field test to realize the long-term effect of sand grouting diffusion process and reinforcement.The mechanism of sand layer grouting reinforcement was studied.The deterioration mechanism induced by seawater ion erosion,seepage and the synergistic effect was studied.Finally,the long-life cycle mechanical properties-time relationship of grouting plus solids under seawater conditions time relationship was obtained.The basis for grouting design of water-rich sand layer under seawater conditions was formed,and engineering application was carried out.The main work and innovations of this paper are as follows:(1)Consider the grouting diffusion law of the sand layer infiltrated by the slurry curve.The fractal theory was used to study the relationship between the actual path length of the slurry-sanded sand particles and the straight line,and the sand layer slurry diffusion model considering the slurry penetration path was established.The sand penetrating grouting diffusion test was designed to study the variation law of the slurry diffusion pressure field under different sand layers and different grouting rates.The influence of grouting parameters on the diffusion distance was obtained,and the difference was compared with the theoretical value.(2)Grouting reinforcement test of sand layer in fresh water environment and seawater environment.The effects of slurry ratio,sand particle size,grouting pressure and other factors on the strength and permeability coefficient of grouting and solidification and permeability coefficient were studied.The main controlling factors of sand osmosis grouting and the long-term performance of grouting and solidification were obtained.The effect of the lower grouting factor on the grouting effect revealed the strengthening mechanism of the seawater environment for grouting reinforcement.(3)Grouting and solidification deterioration mechanism in seawater erosion environment.Analyzing the migration law of small particles due to deterioration of cementation,the mechanism of grouting and solidification deterioration under seawater erosion was revealed.The model of grouting and solid damage under seawater erosion environment was established,and seawater erosion grouting and solids test was designed.Different slurry water under the condition of ash ratio and seawater erosion time was studied.Grouting and solidification,permeability coefficient and porosity evolution law were obtained,and the corresponding relationship between seawater erosion time and grouting plus solid strength was obtained.(4)Deterioration of grouting and solidification under seawater erosion and seepage.The basic mechanical body was used to describe the mechanical properties of grouting and solidification under the action of seepage erosion.The mechanical model of grouting and solid damage under the action of seepage was established.The grouting and solidification deterioration test under the seepage flow was designed to study the effect of permeate water pressure on grouting.The mechanism of solid permeability is obtained,and the change law of grouting and solid damage variable with osmotic water pressure was obtained.Based on the double action of seawater erosion and seepage,the mechanism of grouting and solidification deterioration was established,and the model of grouting and solidification degradation under seawater erosion and seepage was established.The large-scale simulation test was developed to obtain the variation of seepage field and stress field in the grouting reinforcement ring,and the difference was compared with the theoretical value.(5)Sand layer grouting design method in seawater environment.Based on the research results,the design method of grouting reinforcement for water-rich sand layer to ensure the long life cycle safety of tunnel was proposed.The grouting design of water-rich sand layer was optimized based on the practice of Qingdao Metro Line 13.