Study On Physical And Mechanical Properties Of Altered Diorite Porphyrite And Influence On Surrounding Rock Stability Of Underground Caverns

In the construction of underground engineering,especially in the construction of underground powerhouse of water conservancy project,problems such as rock mass alteration are often encountered.The physical and mechanical properties of altered rock will change.Under the action of alteration,the rock often has rich fissures and weak integrity.Moreover,the stability of surrounding rock of underground powerhouse of hydropower station will be further weakened under the action of groundwater.Therefore,it is particularly important to carry out physical and mechanical tests on diorite porphyrite after different treatment methods.Based on Jurong pumped storage power station project,this paper takes diorite porphyrite with different alteration degrees as the research object,adopts the research method of combining laboratory test and numerical simulation,and carries out the following research work.(1)By means of whole rock mineral analysis,scanning electron microscope and three-dimensional microscope observation,the differences of mineral composition and microstructure of diorite porphyrite are obtained,and the alteration degrees of diorite porphyrite are classified according to the changes of mineral composition and microscopic analysis results.Furthermore,the development law of micro cracks in diorite porphyrite with different alteration degrees is analyzed,and the influence of alteration on the expansion property of diorite porphyrite is explored.(2)The diorite porphyrite with different degrees of alteration was treated in different ways(natural state,water saturation,dry and wet cycle).Through uniaxial compression test,conventional triaxial compression test and Brazilian split test,the mechanical properties and failure modes of diorite porphyrite under different treatment methods and alteration degrees were obtained.The influence mechanism of confining pressure,alteration and water action on mechanical properties and failure mode of diorite porphyrite is revealed.(3)According to the test results,the engineering model of Underground Powerhouse Caverns is established by using 3DEC simulation software.The excavation results of underground powerhouse under general conditions,severe alteration and water action are simulated by selecting the meso parameters in line with the engineering conditions.The distribution of stress-strain field and plastic zone of caverns under various conditions are analyzed.The influence of alteration and water action on the deformation of surrounding rock of main powerhouse is discussed.This thesis includes 92 pictures,18 tables and 101 references.