锦屏二级水电站大理岩复杂加卸载应力路径力学特性研究

地下洞室开挖围岩经历典型径向卸载、环向加载应力路径，由此引起的岩体强度、变形特征和破坏机制也不尽相同。针对锦屏二级水电站高地应力赋存环境，对施工排水洞大理岩开展常规单轴全应变、三轴压缩、卸围压、卸围压-加载轴压等4种不同应力路径力学试验，得到应力-应变全过程曲线、变形破坏特征和极限储能变化规律。试验研究结果表明， （1）锦屏二级水电站大理岩破坏时轴向应变一般较小，为硬脆性材料，卸荷应力路径下该脆性特征更为明显；（2）卸围压同时加载轴压试验峰值强度对应轴向应变、环向应变及体积应变值一般高于单纯的卸围压值，而对应峰值强度则一般低于卸围压值；（3）卸荷速率较大时，变形模量越大，大理岩峰值强度越低。加载速率越大，变形模量越小，峰值强度越高。初始围压越高，变形模量值越低，峰值强度越高；（4）无侧限作用时试件主要为张拉破坏，低侧限作用时为剪切破坏为主，局部存在张拉破坏，较高侧限时，剪切面为典型X或Y型；（5）岩石试件具有极限储能值，该值受多种因素的影响。一般情况下试件破坏对应围压越高，极限储能值越高，卸载速率越大，极限储能值越小。研究结果对于岩爆孕育发生机制解释以及工程实际问题的解决均有参考价值。

Experiment study of marble mechanical properties of Jinping II hydropower station under complex loading and unloading conditions

Rock mass surrounding the excavation also under the complex radial unloading and ring direction loading stress path due to the excavation, for which results in difference from that of rock mass strength，deformation property and failure mechanism. Aiming to the high in-situ stress characteristics of Jinping II hydropower station, four different stress paths are chosen as test schemes corresponding as the uniaxial compressive test, triaxial compressive test, unloading triaxial test and unloading confining – loading axial pressure full test under high stress conditions are carried out on the marble specimens from the drainage tunnel. The complete stress-strain curve，deformation properties，failure characteristics and limited energy storage are obtained under respective stress path. Some instructive conclusions are drawn from tests as follows: (1) The failure axial strain is generally small. Jinping marble is hard and brittle which more apparent under unloading conditions. (2) The axial strain, circumferential strain and volumetric strain value unloading confining – loading axial pressure full tests are generally higher in the unloading tests, peak strength conversely. (3) The deformation modulus is large and the peak strength is lower with larger unloading rate, the deformation modulus is lower and the peak strength is large with larger loading rate, the deformation modulus is lower and the peak strength is large with larger initial confining pressure. (4) The principally failure model is tension without confining pressure; shear failure and locally tensile failure with lower confining pressure; while shear failure shape is X or Y with higher confining pressure. (5) The rock specimens have the limited value of energy storage, which can be effected by various factors. Limited energy storage is large with high confining pressure and is lower with higher unloading stress rate. The results can offer valuable references in explaining the mechanism of rockbutst and solving underground rock engineering problems.