Cyclic Impact Damage and Water Saturation Effects on Mechanical Properties and Kaiser Effect of Red Sandstone Under Uniaxial Cyclic Loading and Unloading Compression

In this study, the influence of cyclic impact loading damage and water saturation on mechanical behavior and Kaiser effect of rock samples was investigated through a series of uniaxial cyclic loading and unloading compression tests. The test results showed that the cyclic loading and unloading strength of rock samples in dry condition gradually decreased with the increase of previous damage, while the cyclic loading and unloading strength of rock samples in saturated condition showed a decrease in cyclic loading strength of 10.95% (3 times), - 5.40% (6 times), and 0.87% (9 times) compared to those not subjected to cyclic impact loading. We have elucidated the mechanism underlying this phenomenon from the perspective of water-rock interaction. Statistical analysis of the Felicity ratio values further revealed that the valid response stress interval of rock acoustic emission (AE) Kaiser effect is negatively affected by previous damage and water saturation. Moreover, the relationship among AE signal energy decay rate and previous damage and water saturation was discussed, negatively impacting the valid response stress interval of rock AE Kaiser effect. The results suggest that drilling of cores from stress-disturbed areas should be avoided as much as possible during the measurement of in situ stress using the rock AE Kaiser effect. The tests should also be conducted with dry rock samples to have a larger response stress interval for the AE Kaiser effect. The wave velocity change rate and porosity were used to characterize the previous damage of rock.The influence of previous damage and water saturation on rock failure mode was evaluated.The strengthening mechanism of water-rock strength was discussed.The influence of previous damage and water saturation on Kaiser effect was studied.

Automated summary

This study investigates the mechanical behavior and Kaiser effect of rock samples under cyclic impact loading damage and water saturation through a series of tests. The results show that the cyclic loading and unloading strength of rock samples in saturated condition decreases compared to those not subjected to cyclic impact loading. The water-rock interaction plays a crucial role in this phenomenon. The study suggests that drilling of cores from stress-disturbed areas should be avoided during in situ stress measurement.