It is the intention of this report to give a basic overview of the contribution that the investigations in China recently have been conducted to the strain rockburst laboratory test and the understanding of strain rockburst during the decades. Our emphasis has been paid to the results obtained recently in China University of Mining and Technology in Beijing. The basic performance of strain rockburst conducted under the true triaxial rockburst test system includes the characteristics of acoustic emission time-frequency transform and strain rockburst fragments fractal dimension to compare the rockburst test results to uniaxial and true triaxial compressive test. Test results verify rockburst complex failure process and low energy dissipation fracture mode.
The research work of strain rockburst in China began in 1980. The rockburst problems are challenging frequently during the construction of transport, tunnel, and mines. (Yang 2008; Zhang et al. 2007; Li et al. 2008).
The first attempt to explain strain rockburst with laboratory test was performed by Denkhaus in 1958 (Simon 1999), who pointed out that the rebound of a soft loading system during a uniaxial compression test is proportional to the violence at failure. Cook is the first man who attempted to analysis rockburst with the energy balance theory in 1963 (Simon 1999) and explained the excess of potential energy in a mining system which is the main cause of rockburst. The most of indices for evaluation of strain rockburst potential is closely related to the mechanical behavior of rock under uniaxial compression, such as Bursting Liability Index or Wet Index, Brittleness Index Modified and Index of Released Energy (Simon 1999).
In China, various rock tests have also been carried out to study the failure mechanism of rockburst in laboratory. The experimental investigations have been mainly concentrated on several aspects such as uniaxial compressive, biaxial rockburst, triaxial rockburst, and static-dynamic triaxial test (Feng et al. 1998; Zhang et al. 2002; Tan 1989; Wang et al. 1999; Xu 2003; Zuo et al. 2007; Wang et al. 2001; Xu et al. 2000; Zhang 2004; Huang et al. 1999; Wang et al. 2000).
Most of estimations on strain rockburst based on experimental results is still based upon uniaxial compression test results.
There are few reports on rockburst test of true triaxial unloading (Hou 1994), analysis of strain rockburst classification and description of strain rockburst evolution process (Gu et al. 2002). It is also scarce to find fractal analysis of fragments and AE time-frequency characteristics according to laboratory results. Fractal and fracture topography analysis upon in-situ rockburst fragments was recently carried out by SEM image method (Feng et al. 1999).
We have developed a new experimental system (He 2006), which we call the true triaxial experimental system of strain rockburst. The advantage of this special testing facility is that loading path and stress condition can be considered in rockburst test to sufficiently simulate both the multi-triaxial stress state and the opening boundary due to an underground excavation.