复合岩层变形及强度特性卸围压试验研究

Experimental study of the deformation and strength behavior of composite rock specimens in unloading confining pressure test

探索了复合岩层类岩石试样的制作方法,对不同倾角复合岩层试样进行了常规三轴加载和卸围压试验.基于卸围压试验结果,研究了卸载速率对复合岩层试样的极限承载强度和实时围压的影响规律,分析了层理面倾角与复合岩层试样强度变形参数之间的关系,揭示了复合岩层试样在加轴压卸围压过程中的变形破坏机理,讨论了不同卸载速率下复合岩层试样的破坏模式.得出初始围压为15MPa且在同一卸载速率下,θ=0°～90°试样的极限承载强度随层理面倾角的增加出现先降低后升高,最小值均发生在θ=60°试样.θ=0°试样在卸载速率逐渐增加时,破坏模式从与弱面交叉的剪切破坏逐渐转变成与弱面交叉的拉伸破坏;θ=15°～30°试样均为与弱面交叉的拉伸破坏;θ=45°～75°试样均为沿节理面滑移破坏;θ=90°试样均为与弱面交叉的剪切破坏.

The preparation method of composite rock which made from two different rock-like materials was explored in this paper.The conventional triaxial loading test and unloading confining pressure test had been carried out for a lot of composite rock specimens with different dip angles.Based on the results of unloading confining pressure tests,the effect of unloading rate of confining pressure on the ultimate bearing strength of composite rock samples and the realtime confining pressure were studied.The influence of bedding inclination on the deformation and strength properties of the composite rock specimens were analyzed.Then,deformation failure mechanism of composite rock was revealed in the process of increasing axial compression and decreasing confining pressure.Finally,we discussed the impact of unloading confining pressure rate on the failure mode of rock specimens with different angles.It is concluded that,for the initial confining pressure of 15 MPa and the same unloading rate,the ultimate bearing strength ofθ=0°-90°specimens firstly decreased and then increased with the increasing of bedding inclination.The minimum value occurred atθ=60°sample.As the unloading rategradually increased,the failure mode ofθ=0°specimens gradually transformed from shear failure across the bedding plane into tensile failure across the bedding plane.Forθ=15°-30°specimens,the failure mode are all tensile failure across the bedding plane;Forθ=45°-75°specimens,the failure mode are all sliding failure along the bedding plane;Forθ=90°specimens,the failure mode are all shear failure across the bedding plane.