Study On Damage Mechanism Of Physical And Mechanical Properties Of Limestone Under Hydrochemical Erosion

The Three Gorges Project,the storage of high radioactive nuclear waste,the geological storage of carbon dioxide and the excavation of underground chambers face serious challenges in the construction of complex environments.As the most active factor in the natural environment,the destruction of hydrochemical solution are closely related to the instability of rock mass projects.As the same time,the protection of stone cultural relics is also plagued by the erosion of hydrochemical solution.In view of the stability of geotechnical engineering and the protection of grotto cultural relics,this paper systematically studies the physical and mechanical properties of limestone under hydrochemical Erosion,and considers the fracture and damage mechanism of limestone before and after hydrochemical erosion from the perspectives of mineral composition content,crystal characteristics and dissolution characteristics.Experiment,theory and simulation mutually confirm each other,which provides a theoretical basis for related geotechnical problems.The main research contents and conclusions are as follows:(1)The physical and mechanical tests of limestone with different proportions mineral compositions were carried out and research.Mineral composition analysis,physical and mechanical tests of the limestone with different mineral composition content and calcite were carried out.Analysis of the test results shows that the main mineral composition of limestone is calcite and dolomite.The compressive strength,elastic modulus of limestone and calcite content show a logarithmic function decreasing relationship,mechanical strength of limestone decrease with the increase of calcite content due to the weaker mechanical properties of calcite crystal structure than dolomite crystal.The uniaxial compression failure modes of limestone are split failure while calcite are single-incline shear failure respectively due to the lower tensile strength of limestone and the lower Shear strength of calcite respectively,as a result of the different proportions of mineral composition of the specimen.(2)The physical and mechanical properties of limestone with different proportions mineral components eroded by water chemical solution was studied.The physical properties,chemical properties,mechanical properties and microstructure properties of limestone and calcite specimens eroded by chemical solution at different time were tested.Analysis of the test results shows that the acid rock reaction rate of limestone specimen is lower than that of calcite specimen while the hydrolysis reaction rate is higher than that of calcite specimen in the erosion process of acidic aqueous chemical solution,and finally the limestone dissolution damage degree is greater than that of calcite specimen.The final mass loss rate,longitudinal wave velocity damage rate and strength damage degree of limestone specimens were higher than those of calcite specimens.The mechanical damage law of limestone and calcite specimens eroded by acidic chemical solution showed a good correlation with their dissolution kinetics behavior.The strength damage degree of limestone is lower than that of calcitein the acid rock reaction stage while the strength damage degree of limestone is higher than that of calcite in the hydrolysis reaction stage.(3)The uniaxial compression process of limestone and calcite samples under natural state and after acid water chemical solution erosion was simulated by CASRock software.Analysis of the test results shows that mineral composition content in different proportions affect the fracture process of rock affected by their mechanical properties.Different from the crack propagation phenomenon at the moment of fracture of limestone and calcite specimens under natural conditions,the failure process of limestone and calcite specimens eroded by acidic aqueous chemical solution presents a process of synchronous failure of regional cells.