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为了揭示泥页岩在不同应变速率下的力学特征,为页岩气的开采提供科学指导,分别在5×10-4/s、1×10-4/s、1×10-5/s、1×10-6/s四种不同应变速率下对页岩开展单轴压缩力学试验。研究表明,应变速率对页岩的弹性模量、峰值强度、破裂形态等具有显著影响,应变速率从高到低,弹性模量和峰值强度都呈逐渐降低趋势,但下降速度逐渐放缓,两者与应变速率负对数大致呈幂函数关系,而采用平均值拟合时则相关性较高,相对而言,弹性模量的应变率效应更显著;应变速率对破裂形态的影响极为明显,在高应变速率下页岩迅速劈裂为较少的大块,整体构架丧失,随着应变速率降低,破裂过渡为劈裂为主,伴随局部剪切破坏,达到最低应变速率时主要呈劈裂破坏,但同时形成较多横向分布裂纹,即低应变速率下破坏均匀且形成纵横切割试样的网状裂纹,页岩的应变速率在整体上对破裂方式影响最为显著,主要表现为低应变速率下的破坏更均匀、更易形成裂纹网。因此,该特性对于确立页岩力学参数及设计压裂方案具有重要启发作用。
In order to reveal the mechanical characteristics of shale under different strain rates, the paper provides scientific guidance for the exploitation of shale gas at 5 × 10-4 / s, 1 × 10-4 / s, 1 × 10-5 / s, 1 × 10-6 / s four different strain rate uniaxial compressive mechanical tests on shale. The results show that the strain rate has a significant effect on the elastic modulus, peak strength and rupture morphology of shale. The strain rates decrease gradually from high to low while the elastic modulus and peak intensity decrease gradually. However, And the negative logarithm of strain rate is approximately a power function relationship, while the average value fitting is more relevant, the strain rate effect of elastic modulus is more significant; the impact of strain rate on the rupture morphology is very obvious, At high strain rate, the shale rapidly splits into smaller chunks, losing the overall framework. As the strain rate decreases, the rupture transition is mainly cleavage accompanied by local shear failure. When the minimum strain rate is reached, the cleavage is mainly split However, at the same time, more transverse distribution cracks were formed, ie, the mesh cracks which were destroyed uniformly and formed longitudinal and transverse cuttings at low strain rate, the strain rate of shale had the most significant impact on the rupture mode as a whole, mainly manifested as low strain rate More destruction under the more likely to form a crack network. Therefore, this characteristic has important enlightenment for setting shale mechanical parameters and designing fracturing scheme.