Numerical Simulation of Bed Separation Development and Grout Injecting into Separations

Abstract

In this paper, the Cosserat theory that has been incorporated into a three dimensional finite element code COSFLOW, is applied to analyze the development of bed separations in the layered overburden and grout injection into the bed separations. The mechanism of bed separation development during the longwall mining is investigated. A parametric study is carried out to investigate the effect of major factors including hard rock grade, panel height and panel weight on bed separation development. Based on the modeling, a conceptual model to describe the development process of bed separation is proposed. The effect of grout injecting into the bed separations on subsidence reduction is also studied and the conclusion agrees well with the common realization.

A Comprehensive Study on Subsidence Control Using COSFLOW

“…From previous experiences, it is realised that using a smaller model with refined mesh and mining advance would be more effective than using a big model including all the panels in the model. Based on the modelling by Chen and Guo (2008), it is found that having panels with 1000 m long in the computational model is adequate to reach the supercritical status and the maximum subsidence and the bed separation does not occur notably and grouting has no effect before the mining face passed the section. Therefore, a computation model symmetric about x-axis as shown in Fig.…”

“…In this study, potential major bed separation likely occurs at the five interfaces with levels of 180, 260, 310, 360 and 410 m, respectively, below the ground surface. The bed separation is a very complicated process that develops with mining advance (Chen and Guo 2008). The separation at each interface is distributed mainly in the elements immediately below and above the interface.…”

“…Chen and Guo (2008) employed a three-dimensional finite element code COSFLOW to investigate the development of bed separations in the layered overburden and grout injection into the bed separations to achieve subsidence reduction for a hypothetic longwall operation. It was found from their study that COSFLOW is capable of simulating the bed separation in layered overburden and subsequent rock layer bending due to longwall mining.…”

“…COSFLOW incorporates the layered Cosserat continuum formulation, which provides major benefits over conventional continuum numerical models of sedimentary rock in that the code is able to efficiently simulate rock breakage and slip as well as separation along bedding planes (Cosserat and Cosserat 1909;Adhikary et al 1999Adhikary et al , 2001. In addition, COSFLOW couples fluid flow with strata deformation and stress, and can be used to simulate the effects of mining on ground water systems and predict gas emission during longwall mining (Chen 2006).…”

Research on preventive technologies for bed-separation water hazard in China coal mines

“…Since the 1980s, grouting has been the main preventive measure against bed-separation water hazard. It was first tested successfully in more than a dozen coal mines, such as Fushun Laohutai Coalmine of Liaoning Province and Datun Xuzhuang Coalmine of Jiangsu Province (Chen and Guo 2008;Yan et al 2016), and then promulgated nationally. Later on, new techniques were introduced to treat bed-separation water, such as diversion and interception.…”