Research on a Space-Time Continuous Sensing System for Overburden Deformation and Failure during Coal Mining

Abstract

Underground coal mining can cause the deformation, failure, and collapse of the overlying rock mass of a coal seam. If the mining design, monitoring, early warning, or emergency disposal are improper, in that case, it can often lead to mining disasters such as roof falls, water inrush, surface collapse, and ground fissures, seriously threatening the safety of mine engineering and the geological environment protection in mining areas. To ensure the intrinsic security of the entire coal mining process, aspace-time continuous sensing system of overburden deformation and failure was developed, which breaks through the limitations of traditional monitoring methods that characterize the evolution process of overlying rock deformation and ground subsidence. This paper summarizes the classification of typical overburden deformation and failure modes. It researches the space-time continuous sensing of rock-soil mass above the coal seam based on Distributed Fiber Optic Sensing (DFOS). A multi-range strain optical fiber sensing neural series from micron to meter was developed to achieve synchronous sensing of overburden separation, internal micro-cracks, and large rock mass deformation. The sensing cable-rock mass coupling test verified the reliability of the optical fiber monitoring data. The sensing neural network of overburden deformation was constructed using integrated optical fiber layout technology on the ground and underground. Different sensing nerves' performance and application effects in overburden deformation and failure monitoring were compared and analyzed with field monitoring examples. A physical model was used to carry out the experimental study on the overburden subsidence prediction during coal mining. The results showed that the optical fiber monitoring data were reliable and could be used to predict overburden subsidence. The reliability of the calculation model for overlying rock subsidence based on space-time continuous optical fiber sensing data was verified in the application of mining subsidence evaluation. A systematic review of the shortcomings of current overburden deformation observation technology during coal mining was conducted, and a space-time continuous sensing system for overburden deformation and failure was proposed. This system integrated sensing, transmission, processing, early warning, decision-making, and emergency response. Based on the fusion of multi-parameter sensing, multi-method transmission, multi-algorithm processing, and multi-threshold early warning, the system realized the real-time acquisition of space-time continuous information for the overburden above coal seams. This system utilizes long-term historical monitoring data from the research area for data mining and modeling, realizing the prediction and evaluation of the evolution process of overburden deformation as well as the potential for mining subsidence. This work provides a theoretical reference for the prevention and control of mining disasters and the environmental carrying capacity evaluation of coal development.

Keywords: early warning; multi-algorithm processing; overburden deformation and failure; space–time continuous sensing.

Figure 1

Distribution of coal production: (a) The proportion of global coal production in 2022; (b) China’s coal production from 2013 to 2022.

Figure 2

Mine disasters induced by coal mining.

Figure 3

The development of the stope structure model.

Figure 4

Typical types of overburden deformation and failure modes.

Figure 5

Principle of fiber optic sensing technology [30].

Figure 6

A series of multi-range strain sensing neural cables.

Figure 7

Fiber optic sensors for mine engineering monitoring.

Figure 8

Simplified criterion of sensing cable monitoring accuracy.

Figure 9

Coupling test device for cable–rock mass under controllable confining pressure.

Figure 10

Distributed neural sensing system for rock–soil mass.

Figure 11

Cable layout and data results for ground monitoring system [38].

Figure 12

Cable layout and data results for underground monitoring systems [39].

Figure 13

Optical fiber layout in the model test of predicting the subsidence.

Figure 14

Development trend of overburden deformation and movement observation technology.

Figure 15

Intelligent processing and algorithm optimization of massive data [52]. (a) Process for determining overburden displacement and its influencing factors; (b) Model prediction accuracy verification; (c) Process for random forest model training.

Figure 16

Integrated system for overburden deformation sensing.