Research on Micro-Seismic Source Location During Linear Excavation Process of Deep Tunnel

Abstract

The micro-seismic monitoring work during linear excavation process of deep tunnel has the following characteristics: many working faces are constructed simultaneously; the sensor arrays are located in the rear of the working face; the vertical direction coordinate gap of all sensors is small. Due to the above characteristics, traditional Geiger’s location method cannot work out stable solution. With the micro-seismic monitoring work of Jinping II hydropower station, this article forms Newton second order method and Newton downhill method to improve former method. The rock-burst location results with three methods are proposed and their calculation abilities are compared. The results show that computational accuracy of the second method is influenced by initial value and the third method has the global convergence; At last, the last two methods together are adopted for source location of five rock-bursts. The conclusion indicates that that improves the accuracy and stability of algorithm convergence.

1 Introduction

With deep exploitation of mineral resources and development of underground space, there are more and more underground engineering with increasing rock-burst accidents caused by high geostress^[1] . Therefore effective monitoring and prediction for rock-burst is one of the most important approaches to guarantee the safety of deep geotechnical engineering and micro-seismic monitoring technology plays a pivotal role in it for it can effectively monitor the position of rock fracture ^[2] and begin to be used in some fields like mine safety monitoring and hydropower underground engineering.

3D position of micro-seismic source is an important parameter in the monitoring research, and how to locate the seismic source accuracy and efficiency has always been an important content. Most of the location methods are extended from earthquake location, such as classic Geiger method, relative positioning method, double residual method, Bayesian method ^[3] . These methods have greatly promoted the progress of the study on micro-seismic source location.

In the field of mine micro-seismic monitoring, Chen ^[4] applies particle swarm algorithm to improve the positioning accuracy; Lin ^[5] utilizes linear positioning algorithm to determine the iterative initial value and employs Geiger method for accurate position, which receives the desired effect; Dong ^[6] combines epicenter coordinates with wave velocity as unknown, which effectively avoids the influence of inaccurate velocity. The studies above is all belong to mine micro-seismic monitoring field, however, little research is known on source location during linear tunnel excavation process.