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本文以须家河中粒砂岩、须家河细粒砂岩和嘉陵江微晶质石灰岩三种不同致密程度的岩石为研究对象,利用一套三个主应力大小均可独立改变的岩石真三轴加压设备,对岩石在多轴应力状态下的强度特性及断裂破坏形态进行了深入地研究,并着重讨论了中间主应力σ_2对岩石强度及断裂破坏形态的影响。结果发现,对于不同最小主应力σ_3下的(σ_1/σ_c)～(σ_2/σ_c)强度曲线可以十分近似地用某一抛物线来表示,而对于不同Lode参数λ下的(R/σ_2)～(Q/σ_c)强度曲线则可以十分近似地用某一直线来表示。同时还发现,岩石的断裂破坏将随着应力状态的不同而有可能出现剪切破坏,拉剪混合破坏或拉裂破坏。
In this paper, three kinds of rocks with different densities, ie, Xujiahe granular sandstone, Xujiahe fine-grained sandstone and Jialingjiang microcrystalline limestone, are used as the research object, and a set of three true stress triaxial compressions with independent changes in the three principal stresses can be used. The equipment studied the strength characteristics and fracture failure modes of rock under multi-axial stress conditions, and focused on the influence of intermediate principal stress σ_2 on rock strength and fracture failure morphology. It was found that the (σ_1/σ_c) to (σ_2/σ_c) intensity curves for different minimum principal stresses σ_3 can be represented very closely by a certain parabola, and for different Lode parameters λ (R/σ_2) ～ ( The Q/σ_c) intensity curve can be expressed quite closely with a straight line. At the same time, it has also been found that the fracture and failure of rock will be subject to shear failure with different stress states.