Experimental Study On Mechanical Properties Of Coal Based Solid Waste Paste Filling Material

Under the goal of "reaching the peak of carbon and neutralizing carbon",higher requirements are put forward for green coal mining and resource utilization of coal based solid wastes.Paste filling with multi-source coal based solid wastes is one of the important green mining methods,which can absorb coal based solid wastes such as coal gangue,fly ash and gasification slag on a large scale,and can effectively prevent the occurrence of mine disasters.The mixture ratio of multi-source coal based solid waste paste filling materials is various,and the flow and consolidation characteristics are different,which makes it difficult to reveal the mechanism of its subsidence in the overlying strata supporting the goaf.Based on this,this paper uses three typical coal based solid waste materials,such as coal gangue,fly ash and gasification slag,to determine the optimal proportion scheme of multi-source coal based solid waste paste material by theoretical analysis,indoor experiment and numerical simulation,constructs the paste material damage change model,reveals the collaborative bearing mechanism of backfill,surrounding rock and support,and analyzes the influence of cement content on the paste material filling effect.The research results provide a theoretical basis for underground paste filling in Ningdong coal power base.The main achievements are as follows:(1)The optimum proportion scheme of multi-source coal based solid waste paste material was determined.Gangue: fly ash: gasified slag: cement=1:4.1: 4.1: 0.8,mass fraction is 77%,initial and final setting time are 5.65 h and 11.73 h respectively,compressive and tensile strength are 2.32 MPa and 0.13 MPa respectively.(2)The damage evolution model of paste material was established.With the increase of curing age,the damage value of paste under the optimal proportion at the peak stress also increased,reaching 0.41 at 28 days.At the same curing age,the damage value of paste material at the peak stress increases with the increase of cement proportion,and the paste is mainly destroyed by splitting.0.13MPa。(3)The collaborative bearing mechanism of filling body,surrounding rock and support is revealed,the interaction mechanism between roof and filling body is understood,the process of bearing and control of filling body and support on overlying strata is clarified,and the factors affecting filling effect are clarified.(4)The influence of cement content on paste material filling effect has been mastered.Before paste filling,the maximum concentrated stress of surrounding rock is32.85 MPa,and the maximum displacement reaches 0.187 m.After paste filling,the maximum concentrated stress decreases by 15.42 MPa and the maximum displacement decreases by 0.02 m.Figure [53] Table [18] Reference [89]...