| Geothermal energy is a kind of clean,low-carbon,widely distributed,resource rich,safe and high-quality renewable energy.Dry hot rock geothermal energy is an important field in the future development of geothermal energy.The study of dry hot rock is helpful for us to understand the evolution law of artificial heat storage and further develop the geothermal energy of dry hot rock.Granite is a common type of dry hot rock.Based on the natural characteristics of granite,this paper takes the magmatic hydrothermal filling granite as the research object.Through experiments,different structural forms of magmatic hydrothermal filling granite samples(parent rock,filling body,boundary parent rock,boundary filling body,upper and lower structure,left and right structure granite)are obtained after hydrothermal shock at room temperature and at different temperatures)The parameters include density,porosity,wave velocity,compressive strength,modulus of elasticity,tensile strength and permeability.The physico mechanical and permeability properties of granite filled with magmatic hydrothermal solution at room temperature are compared and analyzed,and the laws of physico mechanical and permeability properties of granite filled with magmatic hydrothermal solution after hydrothermal shock at0?at different temperatures are summarized.Based on experiments and data analysis,the following conclusions are obtained:1.A comparative analysis of the physical mechanics and permeability properties of various types of granite at room temperature was made,and the conclusions are as follows:(1)?is the mean value of granite density,then?(parent rock)>?(upper and lower structures,left and right structures)>?(filling body);w is the mean value of granite water absorption,then w(filling body)>w(parent rock)>w(upper and lower structures,left and right structures);n is the average porosity of granite openings,then n(filling body)>n(parent rock)>n(upper and lower structures,left and right structures);v_pis the granite longitudinal wave velocity,then v_p(upper and lower)Structure,left and right structure)>v_p(parent rock)>v_p(filling body).The smaller the porosity of the four types of granites,the greater the wave velocity.(2)The relationship between the peak strength and the modulus of elasticity of the four types of granite under 10 MPa confining pressure has a good consistency.The relationship between the peak strength?_cof the four types of granite is:?_c(upper and lower structures)>?_c(left and right structures)>?_c(fill Volume)>?_c(mother rock).The magnitude?t of the five types of granite tensile strength is?_t(parent rock)>?_t(boundary parent rock)>?_t(left and right structure)>?_t(boundary filling body)>?_t(filling body).(3)At normal temperature,the permeability of the five types of granite gradually decreases with the increase of confining pressure.Under the same confining pressure,the permeability relationship of the five types of granite k is k(filling body)>k(parent rock)>k(boundary filling body)>k(left-right structural granite)>k(boundary parent rock).Among the five types of granites,the filling body has the largest porosity and the largest permeability.(4)Fine-grained rocks are stronger than coarse-grained rocks,and uniform-grained rocks are stronger than non-iso-grained rocks.Classified according to the absolute size of the mineral particles,the granite parent rock has a coarse-grained or pegmatite structure,and the filling body has a medium-grained or fine-grained structure;Classified according to the relative size of the mineral particles,the granite parent rock has a plaque-like and plaque-like structure,and the filling body has a uniform-grain structure.Therefore,the peak intensity of the filling body is higher than that of the parent rock at room temperature.(5)During the filling process,the"adhesion"and"healing"of the magma hydrothermal fluid near the cemented surface of the filling body and the parent rock caused the density,wave velocity,and compressive strength of the upper and lower(left and right)structural granites to be higher than those of the parent rock and the filling body and upper and lower(left and right)The porosity and permeability of structural granite are lower than those of backfill and parent rock.2.This paper compares and analyzes the physical mechanics and permeability properties of various types of granite after thermal shock at different temperatures.The results are as follows:(1)The wave velocity of granite decreases with the increase of the number of thermal shock and decreases the most after the first thermal shock.The wave velocity of granite cooled by 0?water and that cooled by 0?water decreased with the increase of temperature.Under the same thermal shock mode and the same temperature,the wave velocity drop of the upper and lower(left and right)structural granite is larger than that of the parent rock and the filling body.(2)The thermal shock temperature of granite parent rock and backfill is lower than 300?,and the peak strength and elastic modulus increase with the increase of thermal shock temperature.When the thermal shock temperature exceeds 300°C,the peak strength and elastic modulus of the parent rock and the filling body decrease with increasing thermal shock temperature.The mechanical properties of the upper and lower(left and right)structural granite vary with the thermal shock temperature not only by its thermal damage but also by its own structure and deformation coordination.(3)The mechanical properties of granite depend on the strengthening of bearing capacity caused by thermal expansion,deformation and compaction,and the weakening of bearing capacity caused by thermal expansion and thermal shock.Which effect is dominant is related to the stress state,failure form,mineral particle composition structure and pore fissure development of the sample itself.The tensile strength of parent rock,fillings and left and right structural granites varies with the temperature of thermal shock due to the size and distribution of mineral particles.(4)There is a temperature threshold for the permeability of five kinds of granite with the change of thermal shock temperature.When the thermal shock temperature is lower than the critical value,the permeability of granite increases slowly.When the thermal shock temperature is higher than the critical value,the permeability will increase significantly.The threshold temperature of permeability change of five kinds of granite is 300?.(5)Due to the large size and uneven distribution of minerals in granite parent rock,its thermal fracture is more severe than that of filling body,and the permeability increase of parent rock,boundary parent rock,left and right structure granite is greater than that of filling body and boundary filling body.When the temperature of the thermal shock is 600?,the permeability of the left and right structural granite is higher than that of the boundary parent rock and the boundary filling body,and is basically the same as that of the parent rock. |
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