不同结构顶板垮落带及采空区孔隙率分布规律研究

Study on Porosity Distribution Law of Roof Caving Zone and Goaf with Different Structures

【目的】垮落带直覆下采煤破碎顶板注浆改造工程与采空区垮落带密切相关,故准确掌握煤层开采垮落带形成特征以及其孔隙率分布规律对于合理确定注浆量及注浆范围具有重要意义。【方法】基于FLAC3D软件通过建立模型以及选取合适的边界条件与参数对单、双煤层垮落带和孔隙率分布规律进行研究。【结果】四种情况下的垮落带发育形状均呈“圆拱形”,四周低且向中部平缓过渡;采空区各类型岩层顶板下沉量分布呈“碗形”,四周下沉量较小,中部下沉量达到最大;四种情况下的采空区垮落带孔隙率分布均呈“平底锅形”,采空区四壁孔隙率值较大,中部孔隙率值较小,且从四壁向中变化较快;在四种顶板结构下,孔隙率最大值均在采空区四壁。【结论】研究成果为运用FLAC3D软件在模拟不同覆岩结构下的垮落带形成特征及孔隙率的分布规律提供了参考。

[Purposes]The grouting reconstruction project of broken roof in coal mining under direct over⁃burden of caving zone is closely related to the goaf caving zone.Therefore,it is of great significance to ac⁃curately grasp the formation characteristics of caving zone and its porosity distribution law for reasonably determining the grouting amount and grouting range.[Methods]Based on FLAC3D software,this paper studies the distribution law of caving zone and porosity of single and double coal seams by establishing models and selecting appropriate boundary conditions and parameters.[Findings]The development shape of the caving zone in the four cases is"arched",low around and gentle transition to the middle;the dis⁃tribution of roof subsidence of various types of rock strata in the goaf is"bowl-shaped";the subsidence around is small,and the subsidence in the middle reaches the maximum;in the four cases,the porosity distribution of the caving zone in the goaf is"flat pan".The porosity value of the four walls of the goaf is larger,the porosity value of the middle part is smaller,and the change from the four walls to the middle is faster.Under the four roof structures,the maximum porosity is in the four walls of the goaf.[Conclu⁃sions]This study provides a reference for using FLAC3D software to simulate the formation characteristics of caving zones and the distribution of porosity under different overburden structures.