大面积胶结充填体诱导冒落机理及其发展过程研究

Study on Induced Caving Mechanism and Development Process of Large Area Cemented Backfill

在龙首矿西二采区无底柱分段崩落法采场形成覆盖层的过程中,掌握顶板胶结充填体的冒落机理及其发展过程,对于覆盖层的顺利形成及采矿安全具有重要意义。研究提出了人工诱导顶板大面积胶结充填体冒落形成覆盖层的技术方案,并在该方案实施过程中采用微震监测技术对胶结充填体的冒落过程进行了监测。研究结果表明:胶结充填体的破裂事件主要发生在1610~1630 m水平之间,其破坏机理主要划分为3种模式:一是崩落法采动压力集中在采空区后方20~45 m范围内造成的充填体压裂破坏;二是采空区边缘处剪应力集中造成的充填体岩梁剪切破坏;三是采空区顶板中央位置发生的充填体下沉弯曲拉伸破坏。理论计算结果表明:顶板胶结充填体以散体形式发生冒落的高度约为14 m。现场出矿跟踪过程中观察到冒落的胶结充填体块度在0.6~2.0 m之间。综合各项研究结果可知:在首采分段回采过程中实现了顶板胶结充填体的安全诱导冒落,形成了由预留矿石层和冒落胶结充填体构成的总厚度约为30 m的散体覆盖层,满足无底柱分段崩落法安全生产的需求。

When the mining method in the West No.2 mining area of Longshou mine was changed from down layered cemented filling mining method to sublevel caving mining method,it is necessary to form a loose overburden by caving or blasting the large area cemented filling.Using the traditional drilling and blasting method to form the loose overburden has a series of disadvantages,such as long period,large input and less output,which can not meet the production needs of the mine.A induced caving technical scheme of forming loose overburden by reserving ore bulk as safety cushion and uniformly expanding goaf was proposed,which combined the formation of overburden with the dual demand of stope productivity.Microseismic monitoring technology was used to monitor the caving process of cemented backfill.The monitoring results show that the caving mechanism of cemented backfill in West No.2 mining area can be divided into three types.The first type is the failure event of cemented backfill caused by the mining stress concentration within 20~45 m behind the goaf,which mainly occurs in the early to middle stage of drifts mining.The second type is that with the expansion of the goaf,the shear stress at the fulcrum of the suspended cemented backfill beam is also increasing,when the shear stress exceeds the shear strength of the cemented backfill,the beam will shear failure at the fulcrum at the rear edge of the goaf,this kind of failure event mainly occurs in the middle to end stage of drifts mining.The third is that when the exposed length of the cemented backfill beam increases to a certain extent,the cemented backfill beam bends and sinks under the ground pressure and its own gravity,resulting in tensile stress in the middle of the rock beam of the filling body,resulting in bending and tensile failure in the middle of the cemented backfill beam,this kind of failure event mainly occurs in the middle to end stage of drifts mining.Based on the comprehensive analysis of the results of microseismic monitoring,theoretical calculation and in-site ore drawing tracking,it can be seen that during 1595 m sublevel mining,the caving of cemented backfill mainly occurs at the level of 1610~1630 m.Therefore,a loose overburden composed of residual ore and caving cemented backfill with a total thickness of about 30 m is formed on the floor of the first mining sublevel.This loose overburden thickness meets the safety requirements of mining and the requirements of relevant safety regulations,which shows that the preset goal of forming loose overburden safely,efficiently and at low cost has been successfully achieved by using induced caving technology in the West No.2 mining area.