Study On Deformation And Stability Of Surrounding Rock In Coal Mine Roadway Based On Fiber Bundle Model

Our country has much smaller number of deaths in recent ten years, but weare still far away from the goal. Among all the coal mine accidents, roof cavingand side falling account for a large proportion, which are the results ofdeformation and degradation of surrounding rocks in roadway. Deformation ofroadway is a threat to the safety of workers and has serious impact on normalproduction.On the basic of analyzing existing theories and methods of studyingsurrounding rock deformation，we found some shortcomings of them andpropose a fiber bundle model applying to the study of deformation ofsurrounding rock. The existing theories have make a great contribution to coalmine safety production, while they are come from engineering practice andexperiment in the laboratory, such as strata bumping, displacement and supportdeformation, and from which researchers get data to come up with all kinds oftheories and methods to interpret the phenomena. However theories have a fewlimitations, since they cannot get the details of interior microscopic deformationand the process of fracture, thus they are no very clear about the micro-levelmechanism. When under stress, rocks will generate inherent micro-leveldamages and fissures transiently, and the pre-existing fractures enlarge theirscale. The macroscopic failure evolution processes are the results of enlargementand mergence of micro-level mechanism. Then we know that macroscopicfailure begins from one or a few points which develop into a face. Even a small face in the beginning can be regarded as a point. For these reasons, we study andsimulate a fiber bundle model to learn the process of rock deformation andbreaking.For the modeling of fiber bundle, we analyze the classifications ofsurrounding rock of roadway which include single-index and multi-indexclassifications. Then we assess those classifications from the perspective oftheory supports, levels of detail and practicability for the scientificity ofclassification. Linear creep model of rocks are introduced, summarizing itsapplication, and we make some theoretical analyses of linear viscoelastic creepof rock and parameters are modified to set the foundation of a single fibermodel.Compared to the whole fiber model, a single fiber model is microcosmic.Using the computers, we give every single fiber different parameters and makesimulation analysis of the whole fiber bundle model. One important advantageof this model is that it is easy to understand and be analyzed by computers, sowe are able to learn almost every detail. Therefore, we can better understandrock properties, such as the law of form quantitative change to qualitativechange and energy release during the process of rock breaking. This advantagedoes not exist in previous methods.Basing on the parameters of rock like tensile and compressive strengths,creep, and Poisson’s ratio to introduce two kinds of fiber models, continuumdamage fiber bundle model and multi-linear fiber bundle model. The maindifference between them is the constitutive curve of single fiber. We have apreliminary theoretical analysis to the former and a much close computersimulation to the latter. In this work, we interpret the concepts of biggestreduction times, reduction coefficient of Young’s modulus for this study. Bycomputer simulation, the relationships of those concepts and the constitutivecurve, the avalanche size of the fiber bundle model are analyzed. Then weillustrate how those works will help in the study of surrounding rock deformation and stability.The relationship between constitutive curve of fiber bundle and rockdeformation and the relationship between avalanche size and acoustic emission,deterioration of surrounding rock are established. We find that deterioration havea negative correlation with Kmax and a positive correlation with a. Avalanchesize has a power law, which is more sensitive to a. All those works will help theanalysis and monitor deformation of rock in the coal mine.