Abstract
Due to the acceleration of urbanization in China, the land use and new building construction in mining subsidence areas are increasing. However, a large high-rise building (100 m × 80 m × 100 m) was planned to be built above gob areas in the Xiangcheng Mine subsidence area. According to the analysis of the borehole exploration data, borehole TV observations, and theoretical calculations, there were broken bedrock and developmental fractures in the fracture and caved zones above the gob areas. In addition, the depth affected by the building load is less than 9 m from the top of the fracture zone; thus, the stabilities of the gobs are low. Then, through the theoretical analysis of the space stress, compression settlement of foundation soil, and residual settlement of the gob and coal pillar under loads, combining the similar simulation study on settlement characteristics of foundation soil and gobs, the total settlement of the foundation can be regarded as the vector superposition of the compression settlement and residual settlement; then, the maximum settlement is calculated as 555 mm and the maximum tilt is 14.9 mm/m under the building load, which are greater than the permissible values of 200 mm and 2 mm/m, indicating that the foundation’s stability is inadequate. Therefore, the treatment measures of the deep pile group foundations in the soil layer and grouting reinforcement in the gobs were simultaneously put forward to effectively improve the stability of the building foundations.
Highlights
An increasing number of mining subsidence areas are created due to the high intensity and large-scale mining of coal resources
According to the statistics from 2017, there has been more than 20,000 km2 of subsidence areas in China, involving the construction of 5000 km2 of urban and rural land, which seriously impacts the sustainable development of mining areas after resource depletion
Destruction to the new buildings or structures constructed above gob areas has occurred, such as settling, tilting, cracking, or collapse [3]
Summary
An increasing number of mining subsidence areas are created due to the high intensity and large-scale mining of coal resources. References [18, 19] pointed out that when these fractures and cavities and residual pillars in the gob are influenced by the building load (shown in Figure 1); they would accelerate the movement of the unstable bedrock and the settlement of unstable coal pillars, thereby causing the destruction of the new building foundation. In this paper, according to the field exploration, mechanical analysis, similarity simulation, and the establishment of settlement models, the effects of different settlement and deformation of the building foundation due to gob areas and coal pillars under the large building load are analyzed, a prediction formula for the settlement and deformation of the large building foundation is developed, and the stabilities of the gobs and foundation are studied. Different from the previous research on the grouting reinforcement of large foundation by the author himself [13], this paper enhances the theoretical research on the stability of large building foundations, improves the evaluation method of gob areas, and provides a good case for the similar constructions in mining subsidence areas
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