Experimental Study On Creep And Its Disturbed Effect Of Rocks

Soft rock wall of tunnels in deep mining will have large creep deformation when the stress in rock is near its ultimate strength. Most of the creep deformation is caused by disturbing loads. Hence, studying of the creep property of rock under disturbing force and developing an appropriate theory for it are of great importance for support of soft rock in deep mining. This dissertation is framed into the NSTC project in title of "Experimental study on rock disturbing creep within the strength limit adjacent domain". This dissertation is focused on the study of rock creep and its disturbed effect .In this paper, the disturbed effect of rock creep when the load is approaching its ultimate strength is studied. Tests of creep under uniaxial compression, tensile creep and its disturbed effect in bending of rock beam are carried out by a new creep instrument with ordinary triaxial and disturbing loading devices. The peak strength adjacent domain of rock creep deformation under the tensile condition and its relation to disturbing load are studied significantly.During the rock creep test of unaxial compression , gravitation loading creep instrument and paper-based electric resistance strain gage methods are used; the tests of rock creep characteristics are made under the stepwise loading condition .This studies are focused on strain modulus under the creep condition ,and on strain effects and time effects of Possion' s ratio. The thresholds of lateral even creep is about 60-80 percent those of axial even creep. Lateral creep have a obvious accelerated phase, it is earlier than accelerated creep phase. As strain level increases strain modulus, so Poisson's ratio increases remarkably. Furthermore, the tests are made by use of MTS: redstone instantaneous loading -unloading test, short-term loading -unloading test and mudstone long-term tests are made by use of gravitation loading creep instrument, to validate the time effect of rock mechanics parameters further.The new rock creep model is established by introducing damage variable and hardening variable, and on the basis of component compound model (used extensively in the project practice).This model showed that there occur two competitive mechanisms; that is, damage and hardening, in the rock creep process. The hardening mechanism is dominant in the...