| The instability and failure of rock relate to the safety and stability of slope,foundation and underground cavern,et al.It is of great significance to study the failure process and mechanism of rock for the design,construction and stability evaluation of geotechnical and underground engineering.In this paper,the real-time observation and study on the whole process of rock fracture with holes have been earried out;the rock characteristics under uniaxial compression conditions and the points load strength characteristics have been studied;the conventional triaxial loading and unloading confining pressure tests of several kinds of rocks,such as marble,schist and sandstone;the stress path,temperature,and so on have been analyzed.The influence of water and other factors on the mechanical properties of rock were coMPared and analyzed.The main contents are as follows:(1)The whole process of crack initiation,propagation and instability failure of marble and sandstone with prefabricated circular holes under uniaxial compression 1s obtained.The micro-fracture modes of rocks under different conditions and their effects on the strength of specimens have been analyzed.(2)The uniaxial compressive tests of different rocks were carried out,and the fracture characteristics under uniaxial compression are analyzed.The effects of water-bearing state and bedding characteristics on the fracture characteristics are analyzed.(3)Through the point load test of sandstone and limestone,various calculation methods of point load test are introduced in detail.The point load test characteristics of different lithology rocks and the linear conversion coefficient between point load strength IS(50)and uniaxial compressive strength UCS are coMPared.(4)Conventional triaxial compression and unloading confining pressure tests of marble,schist and sandstone were carried out.The fracture characteristics of rocks with different lithology and structure under unloading conditions are coMPared,the relationship between rock fracture form and strength is analyzed,and the mechanism of rock unloading failure is discussed.(5)Uniaxial and conventional triaxial tests and unloading confining pressure tests of marble after temperature action were carried out.The fracture forms and strength characteristics of marble after temperature action were investigated emphatically,and the influence mechanism of temperature on rock fracture characteristics was preliminarily discussed.(6)Conventional triaxial loading and unloading tests of sandstone under dry and saturated conditions were carried out to analyze the effects of water on the loading and unloading strength and fracture characteristics of two different sandstones.(7)The Mohr-Coulomb strength criterion and Mogi-Coulomb strength criterion are coMPared and analyzed.Based on the experimental results,the Mogi-Coulomb strength criterion is used to analyze the compressive strength of marble and saturated sandstone under conventional triaxial loading and unloading.The results show that the Mogi-Coulomb criterion is superior to the Mohr-Coulomb criterion. |
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