Study On The Deep Fractured Surrounding Rock Rheological Mechanical Properties And Viscoelastic Plastic Damage Constitutive Model

The deformation of deep underground roadway is not completed immediately after excavation,which has obvious time-effect characteristics.The surrounding rock of the roadway is already in a state of damage and fracture under the complex geological conditions and high ground stress.Under the action of mining disturbance such as roadway excavation and mineral recovery,the degree of damage and fracture is aggravated.The mechanical properties of deep fractured surrounding rock and intact rock are quite different,and have unique bearing and deformation characteristics.Therefore,it is necessary to study the time-dependent deformation characteristics of rock with initial damage.In this thesis,the damage and fracture rock sample is taken as the research object.Based on the results of mercury intrusion test,the quantitative evaluation index of damage and fracture degree of its microscopic characteristics is established.The creep and stress relaxation characteristics of damaged and fractured rock samples were studied.Based on the above damage and fracture degree evaluation index and rheological mechanical properties,a rheological constitutive model considering the initial damage of rock is established.FLAC^3D was used to carry out the secondary development of the new model,and the numerical verification was carried out.Based on the new constitutive model,the long-term stability of deep fractured surrounding rock roadway was studied.The main results are as follows:（1）The deep damaged rock samples were prepared by synchronous unloading of axial pressure and confining pressure,and the triaxial compression test of damaged rock samples was carried out to obtain the strength and deformation parameters.The mercury intrusion test of damaged and fractured rock samples was carried out,the evolution law of internal pore structure with unloading point was analyzed,and the quantitative evaluation index of rock damage based on porosity evolution was established.（2）Based on the reloading characteristics of damaged rock samples,the stress level and stress series,strain level and strain series in the graded loading rheological test are set.The creep and stress relaxation tests of damaged rock samples with different degrees of damage were carried out,and the rheological mechanical properties of damaged rock samples were analyzed.（3）Based on the rheological mechanical properties of damaged rock samples and the established quantitative evaluation index of damage,the viscoelastic-plastic damage constitutive equation considering the initial damage of rock is established,and the model parameter identification is carried out.The secondary development and numerical simulation verification of the new constitutive model were completed by FLAC^3D.The long-term stability of deep fractured surrounding rock roadway was studied,and the influence of initial damage on the time-dependent deformation characteristics of roadway surrounding rock was analyzed.This thesis has 53 figures,28 tables and 140 references.