Numerical Modeling Of SH Wave Modes And Characteristics of Wave Propagation And Reflection In a Coal Seam

Zhen, Yang (Shool of Mines, China University Of Mining And Technology) | Chencheng, Huang (Shool of Mines, China University Of Mining And Technology) | Wang, Shugang (Department of Energy and Mineral Engineering, Penn State University)

OnePetro 

Since several mine inundation on disasters happen in china andU.S. in the past, researchers have paid more and more attention to the In Seam Seismic (ISS) method which can be applied in detecting the uncertain boundaries in a coal seam. The uncertain boundaries are mapped by the reflected channel waves. Wave propagation has been studied for several decades, but is still remains very difficult to identify the reflected channel waves effectively in a coal seam due to the rock-coal-rock structure. SH wave plays an important role in the rock-coal-rock structure, so this paper focuses on modeling SH wave propagationin a rock-coal-rock structure with a Gaussian pulse as an explosion source. Our results show that the SH wave will be excited in different modes in a coal seam due to different positions of a seismic source and different angles of truncation, which is the key to map the uncertain boundaries to avoid disasters such as Quecreek and Wangjialing coal mine accidents. Finally, the rock-coal-rock is a natural filter for SH waves in a coal seam in practice, so it is still important to select the right filter before mapping uncertain boundaries based on the ISS technique.

1. INTRODUCTION

Uncertain abandoned voids, old workings gobs, and faults are potential threats to live of coal miners and can also increase the cost of underground mining. Nine miners were trapped over 3 days in a mining accident after the continuous mining section cut into an abandoned mine accidently at the Quecreek Mine, Pennsylvania, in the United States, on July 24, 2002 [1]. In china, 152 miners were trapped in the underground due to the water flooded into working area accidently, and 38 miners lost their lives in this mining accident on March 28, 2010 [2]. If gas and water accumulations can be detected ahead of mining, the risk of mining can be reduced. Many different techniques have been developed to address such problems, but most havelimited usefulness or high cost. Drilling is the main exploratory method used ahead of working faces. It directly detects prospective coal area, but the information provided by sampling drilling may be incomplete or inaccurate. The technique of indentifying the differences of velocity and attenuation of seismic wave between the coal and the surrounding rocks has been used for coal exploration [3].Another method is to use transmitted waves between boreholes to determine void and discontinuities [4]. Surface reflection is not a cost-effective and accurate method for detecting voids [5]. Thus, the most effective method to locate the void in a coal seam may be the Seam Seismic Method.Wave propagation in a coal seam has been an interesting problem since last decade, because it is very difficult to identify the reflected channel waves [6]. Since several mine inundated disasters happen in U.S. and China, researchers have paid more and more attention to ISS to explore how to detect the uncertain boundary in coal seam. The key of ISS is that the uncertain boundary is mapped by the reflected channels waves.