Numerical Simulation Research On Location Method Of Acoustic Emission Source Of Rock Fracture

With the booming development of high-speed rail technology in China, the design application of deep burying long tunnel increases day by day. These tunnels sometimes need to be built in areas where there are unfavorable geology, rock mass damage and instable lithology. During their construction, exogenous process such as digging and explosion will cause destabilization, leading to reassignment of rock mass stress which is originally of balanced stress. In this reassignment process, the stress will be released through elastic waves which is also called acoustic emission phenomenon. The signal caused by acoustic emission source includes information related with damage degree of rock mass like breakdown point of the rock mass, size and scale of released energy.Thus, the evolution law of rock mass damage can be studied through analyzing acoustic emission signal. The location where the rock mass is disturbed or where there is acoustic emission source is what is cared most. The target of estimating the stability of the whole rock mass can be achieved by determining the location of acoustic emission source.This paper introduces theoretical basis of acoustic emission technique, location methods that are frequently used and major application areas, summarizes acoustic emission characteristics and analyzes major factors that influence positional accuracy of acoustic emission and puts forward the method that uses S-wave to locate two consecutive acoustic emission sources by taking advantage of variable coefficient in probability statistics since current locating software is of shortcoming that only uses P-wave to locate. The major contents include:1. Intuitively reveal wave field propagation characteristics of two consecutive acoustic emission sources through making use of finite element numerical simulation method to simulate the wave field of the two sources;2. Rock acoustic emission wave field is a complex wave field that includes interference wave caused by P-wave, S-wave and side wave from different interfaces of the rock stratum. The result of numerical simulation indicates that various kinds of wave modes caused by P-wave and S-wave reflecting and refracting on interface will have greater influence on the P-wave than S-wave from the second acoustic emission source. Therefore, based on the relation between energy and amplitude, this paper proposes that the two consecutive acoustic emission sources should be located through utilizing transverse wave with strong energy and amplitude.3. The wave fields of two consecutive acoustic emission sources will lead to larger amplitude of the wave mode originally with smaller amplitude through mutual interference. If S-wave with greater amplitude is used to locate, this will cause in accurate location. To solve such inaccuracy, locating point with greater positioning deviation can be eliminated by introducing variable coefficient in probability statistics to determine the result from each source.The research of this paper provides theoretical basis for locating two consecutive acoustic emission sources by taking advantage of first arrival of S-wave. This method effectively solves the location issue under the mutual interference situation caused by wave fields of the two consecutive acoustic emission sources. As for the issue of large-scale acoustic mission from rock mass, it has practical significance of predicting the damage area and evolution law of rock mass.