Strength Prediction Of The Lamination Backfill Body Under The Exploitation Of The Residual Ores With Widespread Mined-out Area And Its Application

In mining void control,it is often to encounter a situation where the backfill capacity is small while the mining voids to be filled are large,which will lead to the fact that the backfill body is formed layer by layer through pouring and formed the lamination backfill body.The strength of the lamination backfill body is one of the key factors to the mining void control.However,traditional researches regarded the strength forming process after the slurry was transferred into the mining stope as a black box,and primarily focused on the 28-day strength under standard curing,yet failing to consider the effect of the technology of lamination multiple time filling and multiple stope maintenance.This leads to the huge difference between the results of lamination backfill body experiment and in-situ strength.To improve the predictability of the strength for the lamination backfill body experiment,this dissertation conducted theory and experiment studies chose the underground mining void control in Xiang Lu Shan tungsten mine as the research target,and conducted researches on the following four aspects:the conditions of lamination backfill and multiple curing condition,the flow characters of backfill laminar effect,and the strength prediction model and backfill strength design method under the multi-factor curing.The main research work and conclusions are as follows:(1)The current mining progress and the mining voids of the Xiang Lu Shan tungsten mine were investigated.Field studies on the complex mining voids were conducted,and the distribution characters of the complex mining voids and pillars in the Xiang Lu Shan tungsten mine were investigated.The mining voids and pillars were classified based on the height-width ratio.The recover process for the complex mining void in the mine was analyzed.The current backfill technological status of complex mining in the mine was identified and the main problems for the complex mining void control and residual ore recover were revealed.(2)Bulk character test of lamination backfill body flow was conducted.Through slope experiment,yield stress had been introduced in the to traditional McPhail energy dissipation theory and a new backfill slurry flow slope angle prediction model was established,and the model effectiveness was verified.In addition,a laser particle size meter was used to reveal the slurry particle distribution pattern on the flow direction and vertical direction,which laid the foundation for finding the effect of stratification on backfill strength.(3)Mechanical property experiments on the lamination backfill body had been conducted and the law of how the lamination effect would affect the backfill body strength,deformation and failure characters was investigated.A numerical model for backfill based on discrete variable simulation was established,and the failure characters of the backfill body were analyzed under the lamination effect,which revealed the mechanical properties of lamination effects on the dynamic properties of the backfill body.(4)The evolution experiments and mechanism studies on the backfill body strength were conducted under in-situ curing condition.With the aid of the devises,including scanning electron microscopy,thermogravimetric differential thermal analysis,mercury injection apparatus,and so on,the microstructure,hydration products and dewatering characteristics under in-situ curing condition were obtained.The strength evolution of the backfill body in-situ curing conditions was identified,and the evolution law was revealed.Based on the orthogonal tests,the effects on lamination in situ strength of factors including the curing pressure,lamination numbers,mass concentration and drainage conditions were studied,and a strength prediction model was established based on these factors.(5)The backfill body target strength design method for complex mining void control and residual ore recover was studied.Based on the concept of height-width ratio,the complex mining voids were classified,and the traditional Mitchell model was improved by introducing the shape factors and arching effects.The self-supporting strength was considered by analyzing the room shape factor.The requirements of backfill body strength were further analyzed by factors including the properties of the surrounding rock,the potential as a working platform,and blasting.Finally,the target strength calculation methods for the backfill body was raised under the condition of complex mining voids delegation and residual ore re-mining coordination mechanism.(6)Since there were unknown laws of strength evolution of the backfill body in the complex mining voids,research results of this dissertation had been applied to the complex mining void control in the Xiang Lu Shan tungsten mine,and a classification and grading backfill treatment scheme was proposed.The material ratio of the backfill materials was improved and engineering measurements to reduce lamination effects were taken.The effects of the application were analyzed and the results shows that the mining void control and residual mine recovery had reached the expected target.