Study on Characteristics of Overburden Strata Structure above Abandoned Gob of Shallow Seams—A Case Study

Abstract

To understand the change in overburden structure after coal seam group mining, we investigated the overburden characteristics and bearing capacity of abandoned coal mines in a coal seam group. We provide a theoretical basis for the construction and utilization of a coal mining subsidence area under a complex geological environment. This paper takes the construction project of Zhongtie Huizhi Square in Zhangqiu District, Jinan City, Shandong Province as the engineering background. According to the occurrence conditions of the study area, theoretical analysis, similar simulation, numerical simulation, and engineering practice verification are used. The overburden structure characteristics of abandoned mines in a shallow-buried coal seam group were studied. The results show that the development height of the water-carrying fractured zone after the mining of the 3#, 4#, and 9# coal seams is 17 m, 19.5 m, and 27.1 m, respectively, which shows that the height of water flow in the fractured zone is proportional to the buried depth of the coal seam after coal seam mining. After the model is set aside for three months, the degree of development of the residual fracture in the goaf is analyzed, and the distribution law of residual porosity in the longwall old goaf of a shallow-buried multiple coal seam is obtained. The development rate of residual fissures on both sides of the goaf is between 20.31% and 42.31%. The residual fracture development rate in the middle is relatively small, being between 8.21% and 18.53%. We comprehensively analyzed the characteristics of overlying strata in the abandoned mine under actual stratum conditions, and compared the empirical calculation results, theoretical research, similar simulation, and numerical simulation results in the specification with the engineering practice to prove the reliability of the research.

Study on Aeolian Sand-Box Backfill Geomechanical Characteristics and Overlying Strata Control Effects

“…To assess the suitability of aeolian sand-box-type backfill for filling mining under different coal seam conditions, this section examines the control effect of various As shown in Figure 15, during coal seam mining using the caving method, the displacement of the overlying rock layers above the coal seam primarily exhibits a trapezoidal distribution, which is in line with the typical pattern of overlying strata displacement. This observation aligns with the findings of other researchers [33][34][35]. The collapse of the overlying strata above the coal seam intensifies with the progression of the working face.…”

A Field Study Implementing New Monitoring Technology for Roof Caving and Systematic Monitoring for Gob-Side Entry Retaining via Roof Cutting in Underground Coal Mining

“…Meanwhile, the microseismic data cannot reflect the compaction process of the gangue in the goaf. Therefore, the effect of the roof cutting operation can only be evaluated, resulting in the roof cutting design completely relying on engineering experience [ 26 , 27 ].…”

Limitations of Upper Protective Layers as Pressure Relief Measures for Extra-Thick Coal Seam Mining: Insights from a Case Study

“…Surface subsidence observations also verified this point, which will be analysed in Section 5.1. Therefore, the high-position overlying rocks will exhibit an "arch" structure [38][39][40], which is the main reason why the static stress on the gob side of the coal seam in the longwall panel 6124-1 remains high after the extraction of the UPL.…”