Study On The Stability Of The Cave Dwelling Above Mined-Out Area

With the rapid development of economy,the phenomenon of underground coal mining in our country is has been intensified,it caused a large-scale gob collapse area in some old energy base.Its presence will inevitably affect the surface and surrounding buildings,a little carelessness will cause a series of problems,such as instability,tilt and cracking of the building,to bring serious losses to the country and the people.A series of environmental geotechnical problems caused by underground coal mining have attracted more and more attention,it is very important to study the influence of the mined out area on the surface and its structure.Cave is one of the most traditional living buildings in the world,it has the advantages of cool,cool,green,non-polluting and low energy consumption.With the rise of sustainable development and green building concept,cave has been recognized and valued by the community,therefore,it is of practical significance to study the special arch structure.Based on the failure mechanism of goaf on the ground and its buildings,Follows are the main works in this paper.(1)The failure modes of the cave are briefly introduced and in the case of only by the weight of the stress analysis and theoretical calculations,result indicates that when the cave only by the weight,the compressive strength of soil is far less than this requirement,and the vertical displacement of the arch foot,causing the cave cracks or collapse.The other side of the soil above the arch should be kept enough thickness,otherwise it will cause the horizontal displacement of the arch foot,resulting in cracks of cave.(2)By FLAC3 D finite element analysis software for the mining depth,mining thickness,mining width,different relative position of each structural state simulation,the displacement field,stress field and plastic zone of the cave are analyzed in detail.Rusult show that.(1)Cave affected by the mined-out area,the maximum vertical displacement occurs at the arch crown,the maximum horizontal displacement occurs at the junction of the arch and the kiln leg,the maximum vertical stress occurs at the bottom of the kiln leg,the plastic zone is concentrated at the entrance of the vault and the bottom.(2)The settlement of the cave above the center of the old goaf is the largest,and the displacement area of the foundation is symmetrical.The settlement of the cave above the boundary of the old goaf is the second,the displacement curve of the foundation is out of symmetry,and the uneven settlement is the most obvious,it should be avoided in the area.The settlement of the cave at the outer edge of the old goaf is the least.(3)With the increase of mining width and mining thickness,the displacement and stress values of cave are increasing.With the increase of mining depth,the displacement and stress values of cave dwellings are decreasing.Under the condition of the simulation,the critical depth ratio is 16,in this case,there is no significant influence on the settlement of the cave.When more than this deep,the existence of mined out area has no obvious influence on cave dwelling.Therefore,in practical engineering,reasonable mining size should be chosen to ensure the settlement of the surface and its buildings in a safe state.(3)By orthogonal test,the relative position of the impact of the most significant,as the main factors,followed by mining width and mining depth,mining thickness of the smaller,is not an important factor.When the mining depth of 60 m,mining thickness of 7m,mining width of 50 m,cave is located in the center of the mined-out area,the maximum settlement of the arch,about 94.22 mm,then the cave in the most unstable state.(4)The timely filling of coal mining can improve the stability of the cave,so that the settlement was significantly reduced,that is,the settlement of cave dome from 94.22 mm quickly reduced to 28.47 mm,a decrease of 69.78%.The higher the filling material strength,the more obvious filling effect,the smaller the settlement of the cave,the filling method can effectively solve the problem of surface settlement.