Study On The Properties And Reinforcement Effect Of Grouting Treatment In The Water Rich Fracture Zone Of Long Fracture

In recent years,with the rapid development of economic construction,the construction of transportation infrastructure in China’s major cities is becoming more and more perfect.For cities with high concentration of people,the construction of underground engineering occupies an increasingly important position.As the lifeline of urban traffic backbone,subway often passes through a variety of complex geological structure units.With the construction and extension of subway foundation pit and tunnel in complex geological environment,the complex geological structure conditions have a very obvious impact on the preliminary design,safety control,construction difficulty,construction period guarantee and investment cost of the project.When underground projects such as subway tunnels and stations are built in unfavorable geological areas such as fault fracture zone,karst development area and granite boulder group,geological disasters such as water inrush and piping,mud inrush and uplift,collapse and large deformation often occur.In this paper,based on the background of the subway station foundation pit grouting treatment project located in the water rich fracture zone,aiming at the problems of slurry leakage and insufficient retention rate of the existing conventional cement grouting materials in the grouting process of the long and large fracture zone,the research on the new cement composite grouting material formed by mixing fly ash and graphene oxide in the conventional cement-based grouting material is carried out In this paper,the influence of the content of graphene and fly ash on the performance of cement-based materials is studied by orthogonal test or single factor analysis.In the laboratory test,the influences of different factors on the fluidity,stability,setting time and rheological properties of the slurry are analyzed firstly,and then the influences of different factors on the flexural strength,compressive strength and micro mechanism of the slurry stone are analyzed,and the optimal mix proportion of the grouting material is determined after comprehensive analysis.After completing the indoor research and development of the new composite grouting material,this paper applies the material to the grouting treatment project of the subway station foundation pit affected by the fracture structure.Through the project site water stop reinforcement effect and core pulling test,it reflects the reliability,practicability and shortcomings of the new grouting material.The laboratory test results show that under the same water binder ratio,graphene oxide can reduce the fluidity of the slurry,reduce the setting time of the slurry,enhance the stability of the slurry and enhance the strength of the stone body.The addition of fly ash can effectively increase the fluidity of the slurry,enhance the stability of the slurry,reduce the strength of the stone body and increase the setting time of the slurry;finally,through comprehensive analysis,it is determined that 0.05% graphene oxide and 20% fly ash are the best mix proportion.Through the analysis of micro mechanism of stone(XRD,SEM),graphene oxide can promote the hydration products and strengthen the traditional cement matrix to form a stable framework.Fly ash particles can fully fill the pores between the cement particles,and the two coordinate with each other,so that the microstructure of the new grouting material has been improved to a certain extent,and the macro performance of the grouting material has been improved strength.After completing the indoor research and development of the performance of the new composite grouting material,the material was applied to the actual project,and the grouting and water stop reinforcement treatment was carried out for the subway station foundation pit with water leakage and gushing,which achieved good results,and the water gushing amount was effectively controlled.