AE Experiment Study on Damage and Failure Processes of Rock with Hole
|Keywords||Rock damage acoustic emission (AE) numerical simulation|
With the development of national economic and defense construction, people gradually recognize that the uses of underground space play an important role on the improvement of ground environment. Some scholars point out that making full use of underground spaces have gradually become the new trend of international energy saving. The mechanical properties of rock are complex and discrete for the reason that rock is a kind of heterogeneous material. The study on damage and failure process of materials has always been the hotspot and difficulty in mechanic research. The failure of rock-like solid materials is a kind of cumulative damage process. This paper combines starting fund project of education Ministry for scholars returned from abroad, which called "Disaster Mechanism and its Control Induced by Rock Engineering", with experiment study and theoretical analysis to study the damage and failure process of granite, gneiss and marble. And the research results are listed as following:Firstly, uniaxial compression tests are conducted on intact rock, and at the same time acoustic emission parameters of rock specimen, including acoustic emission (AE) experiment of rock with different lithology, different size and saturated marble, are recorded by acoustic emission experiment instrument. The experiment tests the damage and failure process with different rock specimen and it is shown that there are three obvious stages between rock stress and change rate of acoustic emission, including no significant change stage(0-50% peak strength), significant change stage(50%-90% peak strength) and before failure stage(90%-100% peak strength). To the corresponding, there are also three stages between event number of acoustic emission and loading time, including slow growth stage of acoustic emission events, steady growth stage of acoustic emission events and rapid growth stage of acoustic emission events. The effect of rock with different size on failure mode is not obvious in acoustic emission experiment with different rock size. The time of rock specimen with smaller size into significant change stage of AE events is earlier than rock with large-size. In AE experiment of saturated marble, the test results show that saturated marble entering into significant change stage and steady growth stage of AE events is earlier than unsaturated marble and there are no obvious differences of failure mode between saturated and unsaturated rock specimen.Based on the above-mentioned experiment, this paper mainly carries out AE experiment of rock with hole including rock with semi-section deep hole and rock with total cross section deep hole. The test show that there are obvious differences of failure mode between rock with hole and intact rock, rock with hole into significant change stage is earlier than intact rock. Significant change stage of rock with whole is 40%-90% peak load. Rock with hole meet the four-stage of rock brittle failure that is fracture closure stage, linear elastic deformation stage, fracture stable propagation stage and fracture unstable propagation stage. When peak strength exceeds 50%, the horizontal direction of rock with semi-section deep hole will generate obvious acoustic emission phenomena. However, when peak strength exceeds 70%, the horizontal direction of rock with total cross section deep hole will generate obvious acoustic emission phenomena.Making intensive comparative analysis on the above-mentioned test results and based on test data, this paper presents improved damage constitutive relationship model based on AE event numbers, discusses and defines the relative parameters of the model and gives stress-strain curve of intact rock specimen and rock with hole by applying this model. The curves match well with the test data.As verification and supplement of the experiment, this paper carries out numerical simulation aiming at different rock specimen by applying RFPA software, simulates the experiment process of rock with different size and rock with total cross section deep hole. The failure modes got by simulation are match with the test results.