蠕变作用后裂隙类岩石单轴强度和裂纹扩展规律研究
Study on uniaxial strength and crack propagation law of cracked similar rock after creep
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摘要: 岩体在工程中受到外部载荷的长期作用，时间效应突出，且本身含有的不规则裂隙和孔隙，使得岩体强度和流变性更为复杂。为了研究裂隙类岩石蠕变作用对试件强度、破坏形式和裂纹扩展规律的影响，笔者预制单裂隙类岩石试件，第1组保证在同一应力水平和时间下，先进行单轴蠕变试验，再进行单轴压缩试验，第2组直接进行单轴压缩试验。研究发现：对单裂隙类岩石作用低应力蠕变，裂隙角度减小，蠕变效应对单轴压缩强度的影响变小。裂隙角度由 90°变至75°过程中，蠕变效应强化作用减弱；45°时，蠕变效应起劣化作用；30°变至0°，劣化效应不明显。蠕变预处理试件与直接单轴压缩试件相比缺少明显的压密阶段，裂隙角度较小时，峰值应力区域变大。蠕变作用后试件弹性模量比直接压缩试件大，但随裂隙角度增大，弹性模量变小。蠕变作用对单轴压缩裂纹破坏机制和扩展规律的影响与裂隙角度有关，角度小时区别明显。先蠕变后压缩次生裂纹从原生裂纹尖端周围发起，裂纹短密集，而直接压缩次生裂纹稀疏向两端延伸扩展。Abstract: The rock mass is subjected to the long-term action of external load in the engineering,the time effect is prominent,and it contains iregular cracks and po res,which make the strength and rheological property of the rock mass more complex. In order to study the effect of creep behavior of cracked similar rock on rock stren gth,failure mode and crack propagation law,the specimens of prefabricated crack similar rock were pretreated and divided into two groups. One group first was carried o ut uniaxial creep test to ensure the same stress and time,and the uniaxial compression test was then carried out.The second group was directly subjected to the uniaxia I compression test.The experimental results show that: low stress creep acts on a single cracked similar rock. The effect of creep on uniaxial compression strength decr eases with the decrease of fracture angle.During the process of fractune angle from 90°to 75° ,the strengthening effect of creep is weaken. At 45° ,creep effect deteriorat es. The degradation effect is not significant when it varies from 30° to 0°. Comparing with direct uniaxial compression test,the uniaxial compression test after creep lac ks obvious compaction stage,but there are bigger areas of peek stress at small fracture angle. The modulus of uniaxial compression after creep is obviously larger than the direct uniaxial compression, but the elastic modulus decreases as the crack angle increases. The effect of creep behavior on crack failure mechanism and crack pro pagation law under uniaxial compression is related to crack angle,when the angle is small,the difference is obvious. The secondary cracks begin around the tip of the pr imary crack after creep and then compression. The cracks are short and dense,while the secondary cracks under direct compression extend sparsely to both ends.
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