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Abstract Testing system MTS 815 is used to carry out uniaxial and triaxial compression tests for Qianjiaying rock，coal and coal-rock combined body，and their mechanical behaviors and failure modes under different stresses conditions are obtained correspondingly. The similarities and differences between them are analyzed in detail. The shear failure，splitting failure and mixed failure are the main failure modes for Qianjiaying sandstone under uniaxial condition. In addition，the peak strength and modulus of sandstone are similar proportional relationship with wave velocity. Under a certain conditions，such as the circumferential displacement control loading，high strength and low non-homogeneity of rock，type II failure curve of rock can be obtained. However，type II failure can not take place in coal or coal-rock combined body. Under uniaxial compression condition，splitting failure is the main failure mechanism for coal sample. However，the relationship between the peak strength，elastic modulus and wave velocity is not obvious. Under different confining pressures，the failure of coal-rock combined body mainly occurs in coal body. Under uniaxial condition，the failure mechanism of coal-rock combined body is mainly splitting failure. In addition，the high velocity crack propagation in coal body can induce the damage of rock；and the cracks in coal can extend to the rock. All of these can lead to the failure and loss of bearing capacity of coal-rock combined body. However，under triaxial compression condition，the failure mechanism of combined body is mainly shear failure；and the combined body after failure have residual strength. With the increase in confining pressure，the elastic modulus of Qianjiaying combined body increases slowly at the beginning and then increases quickly when the confining pressure is larger than 15 MPa. The peak strength of combined body is approximately linear with the confining pressure.
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Received: 19 July 2010
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2011, Vol. 30 
