Experimental Study On Compressive Properties And Constitutive Model Of Prefabricated Fractured Rock

Rock is a typical heterogeneous material.There are a large number of different scales of joint cracks in the rock.These joint cracks affect the mechanical properties of the rock,so that the inherent compressive,tensile and shear bearing capacity of the rock itself decreases,resulting in the failure of rock engineering stability,which leads to engineering accidents and irreparable loss of life and property.In addition,groundwater reacts with surrounding medium to produce H +,which reduces the p H of groundwater and changes the environment of rock mass.The mechanical properties of rocks will also change in this acidic environment for a long time.In this paper,red sandstone as the research object,through artificial prefabricated single fracture and double fracture,fracture dip angle of 0 °,30 °,45 °,60 ° four kinds of fracture dip angle,the rock under natural conditions and acid conditions to carry out conventional uniaxial,uniaxial cyclic loading and unloading,conventional triaxial compression test,study the mechanical properties and establish the constitutive relationship.The main contents and results of the study are as follows :(1)Red sandstone is used as the bedrock,and prefabricated cracks are carried out on the cut cylindrical rock samples,with the inclination angles of 0°,30°,45° and 60°.The fractured rock samples were cured under natural conditions and placed in glassware for chemical corrosion,and the corrosion period was 20 days.(2)The single and double cracks with the same length and width are selected as the research objects.The uniaxial compression,uniaxial cyclic loading and unloading and triaxial compression tests are carried out to explore the mechanical properties and failure characteristics of the crack specimens.The influence of crack inclination,crack number and confining pressure on the experimental results is analyzed.It is found that the increase of confining pressure can obviously improve the compressive strength of rock,and the increase of fracture number can reduce the compressive strength of rock.(3)The uniaxial,cyclic loading and unloading and triaxial compression tests of fractured rock under acidic conditions were carried out.The differences of mechanical properties between natural curing conditions and acidic corrosion environment were compared.The test results show that the compressive strength of the specimen under acidic corrosion is significantly lower than that of the rock under natural curing conditions.(4)Based on Weibull probability distribution model,continuous damage mechanics theory and statistical damage theory are used to define rock damage variables with initial defects,and the initial damage coefficient K＿d is defined to establish the constitutive model of fractured rock.This model is a further optimization of the traditional model.The data collected from the triaxial test were verified and analyzed,and the test curve was fitted with the model curve.The results showed that the model curve was consistent with the test curve,which proved the scientificity and rationality of the model.