| In deep hot dry rock drilling,the drilling wall is affected by high temperature and alkaline drilling fluid,and the physical and mechanical properties of drilling wall rock change,which induces drilling wall instability and brings great challenges to deep hot dry rock drilling.Therefore,it has important research value and guiding role to study the physical and mechanical properties of rock after high temperature and alkaline solution.In this paper,the common rock mass granite in hot dry rock is taken as the research object.The physical and mechanical tests of granite after high temperature,alkaline solution and the combined action of both are carried out respectively.The effects of high temperature,cooling conditions and alkaline solution on the physical and mechanical properties of granite are studied.Combined with rock slice observation and scanning electron microscope(SEM)test,the change characteristics of granite microstructure after high temperature and alkaline solution are studied,the reasons for the change of macro physical and mechanical properties of granite are explained from the micro point of view.The main conclusions are as follows:(1)With the increase of heat treatment temperature,the decay rate of various test parameters such as longitudinal wave velocity,compressive strength,elastic modulus and tensile strength of granite is larger and larger,and the decay rate of the above parameters of the samples is further aggravated in the way of water cooling.(2)At room temperature,the compressive strength and elastic modulus of granite under the action of neutral solution and p H=10solution decreased slightly compared with the control group,and the mechanical properties deteriorated.After the action of p H=13 solution,the physical and mechanical parameters changed little.(3)High temperature granite shows different reaction phenomena under the cold shock of different p H chemical solutions,and the physical and mechanical properties of granite after reaction are also different.When the heat treatment temperature is 25-200 ℃,the physical and mechanical parameters of granite after the action of p H = 10 solution and neutral solution are almost the same,while the longitudinal wave velocity,compressive strength and elastic modulus of granite after the action of p H= 13 solution are greater.When the heat treatment temperature is greater than 200 ℃,the longitudinal wave velocity,compressive strength and elastic modulus of granite treated with two alkaline solutions are greater than those treated with neutral solutions,and the mechanical properties are stronger.(4)The higher the temperature,the more serious the crystal damage of granite minerals,and the greater the crack density and width;At the same temperature,compared with natural cooling,the damage of granite mineral crystals after water-cooling impact is more serious,and the crack density and crack width are larger;Alkaline environment can repair the damage of granite caused by temperature. |
