| Rock is a collection of various minerals.Due to crustal movement and weathering,a large number of joint fissures of different scales are generated inside the rock.In actual engineering,these cracks have a great impact on the mechanical properties of the rock,leading to many problems in the construction process.In addition,in underground construction such as mining,nuclear waste disposal,and roadway,the groundwater will have a hydrolysis reaction with the surrounding rock mass,and the groundwater contains many chemical ions,which cause the pH of the groundwater to change.The chemical interaction between the groundwater and the geotechnical medium causes the mineral composition of the rock to undergo a chemical reaction,and the microscopic structure changes,thereby affecting the pore size and macroscopic physical and mechanical properties of the rock.At the same time,under the action of ground mechanical,a complex multi-field coupling environment will be formed,which will affect the mechanical properties of the surrounding rock and the stability of the roadway.Therefore,the study of the mechanical characteristics of prefabricated fractured rock with three-dimensional fractured rock in water chemical solution environment and the physical and mechanical characteristics of rock during mechanical chemical coupling process have long-term stability evaluation of underground engineering and identification and reinforcement of damage in engineering.Important practical engineering implications.In this thesis,granite is the research object.Firstly,the qualitative analysis and quantitative test of the microscopic structure,mineral composition,porosity and specific surface area of granite during the chemical solution erosion process are carried out.Then the triaxial compression test of single fracture granite before and after chemical corrosion was carried out,and the influence of prefabricated fracture and chemical solution on the mechanical properties of granite was analyzed.The main research contents and results of the thesis are as follows:(1)Through the chemical attack test of single-fractured granite under water chemical environment,it is found that the pH value of the solution gradually becomes neutral with the increase of soaking time,and the mass and elastic longitudinal wave velocity of granite samples decrease to different degrees.Significant changes in the content of major mineral components;(2)The results of optical microscopy and scanning electron microscopy showed that there were uneven shallow pits and small cracks on the surface of the single-fractured granite after soaking,and the structure became loose,and many small holes appeared on the crystal surface,which were honeycomb-shaped.The structure,the cemented surface disappears,and the large crystal particles are transformed into a large number of small crumb-like particles,and secondary pores are increased;(3)The failure process of single-fractured granite samples experienced four stages: internal micro-crack compression,elastic deformation,crack unsteady expansion and crack penetration failure.Among them,the internal micro-crack compaction stage of the 45° crack sample has a short time compared to 0° and 30°,and quickly enters the elastic deformation stage.When the mechanical reaches 70% to 90% of the peak intensity,the main mechanical drop occurs in the 30° and 45° crack samples.At the same time,the peak strength,elastic modulus and cohesion of the granite samples with 30° and 45° fractures decreased compared with the granite samples with 0° angle cracks;(4)After the erosion of acidic chemical solution,the peak strength,elastic modulus and cohesion of granite samples decreased,the internal friction angle increased,and the longer the soaking time,the greater the influence of different fracture angles on chemistry.The effect of the degree of damage is not obvious. |
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