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研究水-岩耦合作用下岩石力学特性及细观结构,对减少由地下水造成的深部岩体工程病害具有重要意义。采用直径为100 mm的分离式霍普金森压杆(SHPB)装置与电液伺服压力试验机,进行不同含水率下砂岩试件的动静态劈裂抗拉试验,而后对试件破坏断口进行电镜扫描观察,分析断口形貌特征,依靠SEM图像数字处理技术,进一步得出红砂岩拉伸破坏规律。试验结果表明:红砂岩的劈拉强度随含水率的增加而降低,有明显的遇水软化现象;相比于静态抗拉强度,动态抗拉强度大幅提升,且有显著的应变率强化效应;随着含水率的提高,砂岩试件拉伸破坏时,碎块数量逐渐增多,尺度逐渐减小;饱水岩样的动态劈裂拉伸破坏相比于干燥岩样表现出一定的塑性特征。对断口微裂隙的面积等信息进行定量化处理,分析动态劈拉破坏中的水-应变率效应,得出水在不同应变率下砂岩试样的动态劈拉破坏裂纹扩展中具有均衡作用;微裂隙数量与面积随应变率的提高有增加趋势,破坏断口细观形貌特征存在应变率相关性。
Studying the rock mechanical properties and mesostructure under water-rock coupling is of great significance to reduce the deep rock engineering diseases caused by groundwater. A split Hopkinson pressure bar (SHPB) with a diameter of 100 mm and an electro-hydraulic servo pressure testing machine were used to test the dynamic and static splitting tensile tests of sandstone specimens with different moisture contents. Then, Scanning observation and analysis of fracture topography features rely on SEM image digital processing technology to further draw the red sandstone tensile failure rules. The experimental results show that the splitting tensile strength of red sandstone decreases with the increase of water content, and the softening phenomenon is obvious. Compared with the static tensile strength, the dynamic tensile strength of the red sandstone increases sharply and the strain rate strengthening effect is obvious. With the increase of moisture content, the number of fragments increased gradually and the scale decreased gradually when sandstone specimens were tensile and destructed. The dynamic splitting and tensile failure of saturated rock samples showed some plastic characteristics compared with those of dry rock samples. The area information of fractured micro-cracks was quantified and the water-strain rate effect in dynamic splitting and pulling failure was analyzed. It was found that water had an equilibrium effect in the dynamic splitting crack propagation of sandstone samples at different strain rates. The number and area increase with the increase of strain rate, strain rate dependence of fracture morphology.