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为研究不同程度水损伤作用对泥岩断裂力学特性的影响,对水中浸泡不同时间条件下的泥岩半圆盘试件进行三点弯曲试验,同时利用PCI–2型声发射系统对泥岩试件的断裂全过程进行实时监测。结果表明:天然泥岩的断裂力学行为受水–岩作用影响显著,随着浸泡时间的增加,其峰值载荷不断下降,浸泡200 min后,该泥岩纯I型至纯II型断裂韧度分别降低至未损伤条件下的53%,56.5%,61%,64%,64.7%和67.6%,且泥岩的断裂破坏形式由脆性逐渐转变为延性。通过声发射定位确定了不同损伤程度下泥岩半圆盘试件中断裂过程区长度,随着损伤程度加深,断裂过程区长度逐渐减小,声发射事件累计总数不断增加;同时,将试验得到的等效断裂韧度与纯I型断裂韧度的比值与引入T应力后改进的最大周向应力理论比值进行比较,表明在未浸泡及短时间浸泡条件下试验结果符合该理论结果;但随着损伤程度的加深该试验结果拟合曲线逐渐偏离理论曲线,浸泡时间达到200 min时,该偏离情况较为明显。
In order to study the effect of different degrees of water damage on fracture mechanics characteristics of mudstone, three-point bending test was carried out on mudstone semi-disc specimens immersed in water for different time. At the same time, the fracture of mudstone specimen was analyzed by PCI-2 acoustic emission system The whole process of real-time monitoring. The results show that the fracture mechanics behavior of natural mudstone is significantly affected by water-rock interaction. With the increase of immersion time, the peak load decreases continuously. After 200 min of immersion, the fracture toughness of pure mudstone type I to pure type II decreases to 53%, 56.5%, 61%, 64%, 64.7% and 67.6% under undamaged conditions, respectively, and the fracture failure mode of mudstone gradually changed from brittleness to ductility. The length of the fault zone in the mudstone semi-disc specimen with different damage degree is determined by acoustic emission location. As the damage degree deepens, the length of the fault zone decreases and the cumulative total number of acoustic emission events increases. At the same time, The comparison of the ratio of equivalent fracture toughness to pure type I fracture toughness to the theoretical maximum circumferential stress ratio improved after the introduction of T stress shows that the experimental results are in agreement with the theoretical results without soaking and for a short period of immersion; The deepening of the degree of injury The test results curve gradually deviate from the theoretical curve, immersion time reaches 200 min, the deviation is more obvious.