Study On Mechanical Tests And Strength Criterion Of Rock Under The Condition Of High Ground Stress

As deep rock mass is hosted in the environment of high ground stress, the deformation and strength characteristics are very different from shallow rock, so there are also significant differences in the mechanism of engineering disaster, engineering stability control and design theory.While with the development of mining, hydropower exploitation and road and rail transport projects,deep rock mass engineerings become more common. To provide basis for the design and construction of deep rock engineerings,the researches on the rock engineering properties under high stress conditions are put on the agenda, many scholars have made extensive studies on deep rock mass from different aspects such as laboratory test, field test, and theoretical studies.Aiming at the problems of mechanical properties and strength criterion of rock mass under the condition of high ground stress, this thesis chooses the marble and limestone of diversion tunnel of Jinping II Hydropower station and the granite of Laxiwa station as research objects, and carries out systematic test researches.Based on the uniaxial tests,conventional triaxial tests under high stress conditions and triaxial tests of complex loading and unloading stress paths, the strength and deformation characteristics of hard rock are abtained. Connecting with theoretical analysis,the problems of rock burst and strength criteria are researched.The main purpose of all work is to play an impelling action on the researches on the engineering properties of rock mass. Main works in this thesis are included as in the following.(1)Based on the uniaxial tests,conventional triaxial tests under high stress conditions and triaxial tests of complex loading and unloading stress paths, the strength and deformation characteristics of hard rock under high stress conditions are studied,the variation law of rock mechanical parameters with confining pressure is abtained. Connecting with theoretical analysis, the reasonable of the classâ…¡curve is analysed.(2)Based on the deep analysis of classâ…¡curve,a new rockburst proneness index is proposed. The mechanical tests of the rock from Jingping powerstation auxiliary tunnel show that the new index is verified to be able to show fairly well the rockburst proneness of rock.(3) Mohr-Coulomb strength criterion,Griffith criterion,double-shear theory and Hoek - Brown criterion which have greater impact on rock mechnics do not apply for the hard rock under high groud stress. Based on the analysis of the method that the existing strength criterions have been set up, Connecting with the strength characteristics of hard rock abtained by high stress testing,a new power function rock strength criterion which can consider non-linear mechanical properties of deep rock is proposed.Some individual opinions about strength criterion of deep rock mass are also given.