Evaluation Of The Stability Of Building Foundations Above Old Goaf

The rapid development of urban construction leads to the shortage ofconstruction lands, and the land resources above old goaf is developed and usedwhich will be an effective way to ease the situation. However, it may also be facedwith the problem of the stability of building foundations to construct buildings abovethe old goaf. Thus, it is particularly important to carry out the research about thestability of building foundations.This artical comprehensively analysises the present research status at home andabroad, describes the progress of the surface movement theory and the stability ofbuilding foundations above old goaf. Based on the mining area data which arecollected and analysised, the article confirms the research content, and makestechnical route. According to the surface deformation monitoring data, it analysisesthe stability of building foundations by using the method of probability integral andfinite element numerical simulation, then it obtains some conclusions.1、In mining area, the surface of ground is flat, the strata is simple, and regionalstability is better. During the period of mining coal, the movement and deformationon the ground lead the building cracking, surface water accumulating. Monitoringpoints are arranged in mining area after mine closure, and the monitoring data showthat goaf surface movement period has ended.2、Due to the reconstruction of San-dao Coal mine township, the building loadswill break the original equilibrium state, which results the cracks in Overlying Strataof the goaf to further close, then the residual deformation will appear on the ground.Before constructing buildings on the ground, the relevant program is written and thesurface residual deformation is estimated based on the principle of the probabilityintegration method. And according to the results, the building damage degree can bedetermined, and so as the area suitable for the construction of building.3、 According to the distribution characteristics of the surface residualdeformation values, what is obtained that3#、4#and5#mined-out areas have the biggersurface residual deformation values, and the maximum damage level for brick structure building is grade Ⅳ, so these areas are not suitable for laying the building.6#and7#mined-out area having small surface residual deformation values are suitablefor laying the building.4、After the construction of buildings above old goaf, the loads of the buildingwill cause the goaf secondary deformation, which lead to the building foundationinstability if the goaf depth is less than the critical mining depth. The calculationshows that the water flowing fractured zone of3#mined-out area has reached tosurface, and the building foundation will be in an unstable state once imposing thebuilding loads on the ground; In the case of the construction of6-storey buildingabove the6#、7#mined-out area，there is great distance between the interference depthof building foundation and water flowing fractured zone, so that the buildingfoundation is in a stable state.5、Through the above analysis, geological sections within the area that is notsuitable for layout a building is selected to analysis the vertical deformation values onthe surface（which can be seen as a part of the residual sinking value）, internaldestruction of overlying strata、the stability of the building foundation the impactionof the construction load stresses and displacements produced at different locations andconstruction loads. The results show that the stress concentration appears around thegoaf area, and its distribution has certain regularity. The effect of building load onstresses and displacements of the shallow goaf is great, resulting in that the shallowmined overlying strata and surface has more obvious vertical displacement. As thevertical displacement value becomes larger with the increase of the building floor,continuous failure face are produced on the ground by building load at of3#、4#and5#mined-out area, so it has poor stability for the foundations of buildings.