Experimental Study On Reinforcement Method For Rock Mass Structural Plane Based On Microbially Induced Mineralization

Rock mass is a complex geologic body composed of structural plane and rock block.The existence of the structural plane not only greatly weakens the integrity of the rock mass,but also changes the mechanical properties and induces geological disasters.The data show that geological disasters caused by deformation and failure of the rock mass structural plane are widely distributed in the world,such as structural plane slip,rock mass collapse and landslides.Although conventional grouting reinforcement methods based on chemicals such as cement or lime are common,the high energy consumption in cement or lime production will release CO2,which aggravates the greenhouse effect.The material of chemical grouting represented by epoxy resin or phenolic resin is toxic,due to the uncertainty and inhomogeneity of the inside structural plane development,it is easy to cause secondary damage of the structural plane during grouting and pressurization,which wastes materials and causes damage to the ecological environment.Among many new emerging geotechnical reinforcement methods for rock and soil,microbial induced calcite precipitation(MICP)technology is considered to be a very potential one,which is simple mechanism,strong sustainability,and no pollution to the environment.Applying this technology to the field of structural plane reinforcement is of great significance for establishing a new method of energy conservation,emission reduction,economic efficiency and environmental protection.Aiming at the hard and the weak structural plane,the paper proposed different rock mass structure plane reinforcement method based on MICP technology.Bacterial activation culture experiment,hard structural plane bacterial smear method,weak interlayer and weak structural plane geotextiles wrapped and cementation media immersion method were utilized,and XRD identification,EDS analysis,SEM observation and mechanical properties testing method were conducted,the paper research on key issues such as bacterial growth law,physicochemical properties,structural plane MICP reinforcement mechanism,influencing factors,and the law of mechanical properties after reinforcement.The specific research contents are as follows:(1)The experiment of activating culture of Sporosarcina pasteurii was carried out in laboratory to investigate the individual growth characteristics of Sporosarcina pasteurii,to establish the standard curve for the relationship between bacterial concentration and optical density,to determine bacterial growth curve and urease activity curve,and to analyze the effect of temperature and pH on bacterial growth and reproduction,which provided test basis on structural plane MICP and reinforcement.(2)The MICP reinforcement experimental study was carried out by applying a high concentration bacteria solution on the hard structural plane made of granite.Additionally,microscopic methods,including XRD,EDS,and SEM were conducted to analyze the induced products on structural planes.Investigating the influencing factors of reinforcement effect,the functional relationship between the shear strength parameters and the influencing factors were established,the optimum parameters of hard structural plane reinforcement experiment were obtained.Analyzing MICP reinforcement mechanism of the hard structural plane from the microscopic level,the causes of changes in shear strength parameters were explicated.(3)A weak interlayer specimen was made from the shear belt mudding interlayer of the Baihetan,and the MICP reinforcement experiment of the weak interlayer was carried out through geotextile mould and cementation solution immersion.The precipitation products for geotextile surface were analyzed by XRD.To investigate the influencing factors of reinforcement effect,the functional relationship of compressive strength and shear strength parameters with the influencing factors was established.The optimum parameters of the weak interlayer reinforcement experiment were obtained.Combining the results of the CaCO3 content test,the relationship between mechanical parameters of weak interlayer and CaCO3 content was studied.The particle cementation in the specimen was observed by EDS and SEM,analyzing MICP reinforcement mechanism of weak interlayer from the microscopic level,the causes of changes in mechanical parameters were explicated,which provided an experimental basis on weak structural plane MICP reinforcement.(4)Taking the engineering practice of the weak structural plane of Baihetan,considering the contact relationship between the weak interlayer and the rock mass,producing "Tuff-Weak interlayer-Tuff" multiplex specimens,through geotextiles wrapping and cementation media immersion method,then the weak structural plane MICP reinforcement experimental study was carried out.Furthermore,the precipitation products for geotextile surface were analyzed by XRD.Investigating the influencing factors of weak structural plane MICP reinforcement effect,the functional relationship of compressive strength and shear strength parameters with the influencing factors were established,and the optimum parameters of weak structural plane reinforcement experiment were obtained.The particle cementation in the multiplex specimen contact surface was observed by EDS and SEM,and MICP reinforcement mechanism of the weak structural plane was analyzed from the microscopic level,which explicated the causes of changes in mechanical parameters.In summary,the structural plane reinforcement technology based on MICP can enhance the integrity of the hard structural plane,weak interlayer,and the weak structural plane,improve mechanical parameters,at the same time with the advantages of simple mechanism,low energy consumption and environmental protection,which has important practical significance and broad application prospects in the field of rock mass structural plane reinforcement.