Study On Static And Dynamic Characteristics Of Basalt After Hydrothermal Damag

In the process of deep resource exploitation,rock is not only in the complex environment of high ground stress,high ground temperature and high ground water pressure field,but also under the action of static load and dynamic load such as rock burst,mechanical vibration and blasting,resulting in changes in its static and dynamic characteristics,thus posing a serious threat to the safety of underground engineering.Therefore,it is important to study the static and dynamic characteristics of basalt after hydrothermal damage for the construction and safety protection of deep underground engineering.In this paper,the basic physical properties test,static mechanical test,microscopic observation test,dynamic mechanical test,SHPB numerical simulation and constitutive model theory research of basalt samples after hydrothermal damage are carried out by integrating the three factors of temperature,water and external load.The influence of hydrothermal damage on the static and dynamic characteristics of basalt is analyzed.The main research content and achievements are as follows:(1)Through the test of basic physical properties,it is found that the hydrothermal damage has a significant impact on the apparent morphology,quality and P-wave velocity of basalt.With the increase of temperature or the number of cycles,the apparent color of basalt gradually turns red,and the number of cracks increases.(2)Using HUT106 A electro-hydraulic servo testing machine,static mechanical tests were conducted on basalt subjected to hydrothermal coupling.It is found that there are significant temperature and cyclic effects in the static mechanical properties of basalt,which deteriorate with the increase of temperature or the number of cycles,and the degree of degradation gradually increases;With the increase of temperature or the number of cycles,the plastic failure of the sample increases,while the brittle failure decreases;Under the coupled action of high temperature water cooling and load,the total damage variable evolution curve of basalt exhibits a nonlinear evolution characteristic.(3)To study the effects of strain rate and temperature on the dynamic uniaxial mechanical properties of basalt,uniaxial dynamic impact tests were conducted on basalt after hydrothermal damage at different impact pressures.The research results indicate that under the identical shock pressure,the dynamic compressive strength,tensile strength,and elastic modulus of the sample gradually decrease with the increase of temperature,and the degree of fragmentation increases.At a constant temperature,the dynamic compressive strength,tensile strength,and elastic modulus of the sample increase with the increase of impact pressure,and the degree of fragmentation gradually increases;The simulation results obtained by ANSYS/LS-DYNA software are consistent with the laboratory test results,and the method of modifying the HJC model parameters can effectively describe the dynamic mechanical parameters of basalt after hydrothermal damage.(4)In order to study the dynamic characteristics of deep rock under the "three high and one disturbance" conditions,dynamic compression tests were conducted on basalt samples under different confining pressure levels using a SHPB device with confining pressure,and corresponding constitutive models were constructed.The research results indicate that under different confining pressure levels,there is a temperature degradation effect on the dynamic mechanical properties of basalt,and the higher the confining pressure,the more significant the brittle plastic transition characteristics and temperature degradation effect of the sample are;The dynamic mechanical properties of basalt after hydrothermal damage have confining pressure strengthening effects;Different confining pressures and temperatures have certain differences in the failure modes of the specimens;The constitutive model based on Weibull distribution established in this paper is in good agreement with the experimental curves,and can be used to predict the dynamic mechanical behavior of deep basalt under the coupling action of high-temperature water cooling and active confining pressure.(5)In order to study the effect of hydrothermal damage on the microscopic characteristics of basalt,X-ray diffraction and electron microscope scanning microscopic tests were conducted on basalt samples after hydrothermal damage treatment,and the microscopic damage mechanism of the samples after hydrothermal damage was analyzed.The results show that the main mineral components of the basalt in this paper are biotite,diopside,anorthite,amphibole,and a small amount of pyrrhotite and chlorite.After hydrothermal load coupling,the main micro fracture forms of basalt samples are intergranular failure,transgranular failure,dimple failure,and slip separation failure,and the larger the temperature gradient or the more the number of cycles,the more micro defects within the sample,and the more severe the microstructure damage.