Study on uniaxial strength and crack propagation law of cracked similar rock after creep

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.