Experimental Study On Mechanical Properties Of Granite Under Chemical-Temperature Coupling Condition

Rock is a kind of heterogeneous body composed of a variety of complex minerals.A lot of underground engineering,including underground surrounding rock,high emission nuclear waste disposal reservoir,underground tunnel,geothermal energy mining and so on,all involve the stability and safety of underground engineering.In the process of dry and hot rock mining,the high-temperature rock mass will undergo rapid quenching in the circulating water system environment.Moreover,the groundwater in the underground environment contains a large number of chemical ions,which changes the p H value of the groundwater and causes a series of chemical reactions with the rock.In addition,there will be in-situ stress in the overall underground environment.As a result,the whole underground environment is in a multi-scale and multi-field coupling environment,and the interaction of multiple fields will inevitably lead to the change of macroscopic physical properties and mechanical properties of rocks,thus further affecting the safety and stability of underground engineering.Therefore,the mechanical properties of granite under the coupling condition of chemical-temperature were studied in this paper.In this paper,the granite was taken as the research object.Firstly,the density,porosity and cooling rate of the granite after quenching at different temperatures were quantitatively analyzed.Then,dilute hydrochloric acid solutions with different p H values were selected to soak the heat-treated granite samples for different time(60 and90 days)by radial chemical erosion from the inside to the outside.The changes of p H value of dilute hydrochloric acid solution with time in the erosion process were recorded,and the changes of appearance of granite samples before and after chemical erosion were observed.Finally,conventional triaxial compression tests were carried out on the granite samples after high-temperature quenching to analyze the macroscopic mechanical parameters such as peak strength,elastic modulus and Poisson's ratio.On this basis,micron indentation tests were carried out to obtain the average elastic modulus and Vickers hardness of granite samples under the condition of chemical erosion after quenching at high temperature,and the variation law of mechanical properties of granite samples under the condition of chemical-temperature coupling was studied.Research shows that: In the temperature range of 25? to 400?,the peak strength of granite increases.When the temperature exceeds 400?,the thermal hardening effect of high temperature quenching on granite is weaker than the thermal crack effect caused by the temperature rise,which leads to the decrease of the peak strength of granite.This phenomenon weakens with the increase of confining pressure.The development trend of elastic modulus and peak strength is similar.The Poisson's ratio did not change significantly with the increase of temperature.With the increase of heat treatment temperature,the granite gradually changes from brittle failure to ductile failure.As a whole,the volumetric strain increases with the increase of temperature.The degree of chemical erosion of granite samples gradually decreases with the increase of erosion distance,and the residual deformation obtained by micron indentation test increases with the increase of erosion days.The variation law of the mean elastic modulus and Vickers hardness of granite is roughly the same,and it increases first and then decreases with the increase of temperature.