The spontaneous combustion of residual coal in compound goaf formed by shallow and close coal seam mining is one of the difficulties in mine fire prevention and control. In order to explore the mechanism of spontaneous combustion of residual coal in 22304 working face of Huojitu minefield in Daliuta coal mine, the causes of spontaneous combustion of residual coal in 22304 working face are studied by comprehensively applying the methods of experiment, numerical calculation, and field measurement, the limit parameters of spontaneous combustion of 22304 working face are obtained, and the risk of spontaneous combustion in 22304 working faces is divided. The results show that the critical oxygen concentration of coal in 22304 face is 8%, and the width of inlet airside and return airside of oxidation temperature rise zone in composite goaf is 245 m and 170 m. When the advancing speed of 22304 working face is greater than 7.42 m/d, it can effectively avoid spontaneous combustion in goaf. Finally, the fire prevention and extinguishing measures of composite goaf after temporary shutdown when the working face passes through faults and other geological structures are discussed. The findings have certain reference significance for the division of goaf spontaneous combustion risk areas and the formulation of fire prevention and extinguishing schemes under similar conditions.

The damage and degradation are the main influence factors of the instability of rock mass engineering. In this paper, the damage and deformation characteristics of the rock‐like samples are investigated under the uniaxial compression test, and the advanced digital image correlation (DIC) device is devoted to full‐field deformation data acquisition on the sample surface. Based on the full‐field deformation data, a new damage variable is proposed by the principal strain standard deviation to characterize the uniaxial compression damage process of the rock‐like samples. The results show that the newly presented damage variable can be utilized for the quantitative characterization of the sample damage. According to the characteristics of the damage variable, the damage evolution process of the rock‐like specimens under uniaxial compression can be divided into four stages: initial damage closure stage, linear elastic damage stage, elastic‐plastic damage stage, and plastic damage stage. From the stress‐strain curve, the cut‐off point from elastic to plastic deformation of the rock‐like specimen is also the turning point from micro to macro damage; after the point, the apparent initial damage starts to occur on the sample surface; furthermore, the damage of the specimen is accelerated in the plastic damage stage. When the overall damage variable reaches 0.5 or the damage variable of strain localization zone reaches 0.8, the macro crack forms, and the bearing capacity of the rock‐like specimen decreases rapidly. The findings are of great significance to the prediction of the damage process of rock mass engineering by digital image correlation.

The evolution of overburden deformation is crucial for safety and environmental efficiency and its monitoring is becoming a key scientific issue. The use of an optical fiber sensor (OFS) for mining engineering is now receiving praise by virtue of its distinct abilities of distribution, high accuracy, and anti-interference measurement. Nevertheless, the dynamic response of OFS monitoring on overburden deformation still needs to be characterized in detail. This paper analyzed the characterization pattern of overburden deformation based on distributed optical fiber sensing (DOFS) by means of an analogue model test. Then, we discuss the influence of rules of optical fiber embedding on a model test in a numerical simulation. The results show that the DOFS monitoring demonstrates the time-space evolution of overburden deformation and the development of three horizontal areas and three vertical zones. A standardization DOFS characterization model is proposed to expound the characterization mechanism of the overburden structure zoning process; the influence of optical fiber embedding on rock displacement in the model test is revealed, and it is found that the displacement error will increase sharply when the fiber diameter is larger than 2 mm. These findings could provide an effective solution for a monitoring method in intelligent mining from the perspective of a theoretical basis and technological system.

In order to study the migration characteristics and strata behavior law of mining-induced rocks in fully mechanized caving face of coal mine, taking the actual geological mining of Longwanggou Coal Mine as the background, using computer software (KSPB) to identify the location of key strata. The physical similar material simulation test was used to monitor the movement characteristics of mining-induced rocks by using the internal displacement sensor (IDS) and distributed optical fiber sensor (DOFS). A three-dimensional physical model of was built; the internal displacement of rock was measured by IDS. BOTDA distributed optical fiber was used to monitor the dynamic movement and deformation law of coated rock. Finally, the two monitoring results were compared and analyzed. The results show that: (1) the displacement curve of the fractured rock mass in the key strata shows a “stepped” increase; (2) based on the analysis of displacement continuous monitoring results, the strata behavior law of working face is obtained. The first weighting interval of 61601 working face is 90 cm, and the periodic weighting steps are 105 cm, 115 cm, 135 cm, 150 cm, 165 cm, 180 cm, 215 cm, and 240 cm; (3) the average strain of fiber is proposed. The first weighting and periodic weighting laws of the working face are represented by the average strain, which are consistent with the experimental phenomena. The first weighting in the average strain curve shows the first mutation peak, and the periodic weighting shows the periodic mutation peak change of the average strain curve.

In order to study the regularity of overburden deformation and mining pressure changes in the stope. Take the geological conditions of Hanglaiwan coal mine in Yushen mining area as the background, a 3000mm×1340mm×200mm physical similar material model was established in laboratory. Eight fiber Bragg grating sensors were embedded in the model, used to monitor the movement and deformation of the overburden key stratum and the change of mining abutment pressure in real time and then to determine the influencing factors and strain transfer coefficients of the fiber grating through theoretical analysis and calibration experiments. The results show the following. (1) The changes in value, position, and shape of the strain can reflect the dynamic evolution process of bending deformation, breaking, and rotation of the key strata. When the key layer breaks for the first time, the strain curve shows a peak shape; when the key layer breaks periodically, the strain curve of the fiber grating sensor showed a plateau shape for a period of time. (2) The strain curve has a good corresponding relationship with the change in supporting pressure. When the strain curve of the fiber Bragg grating sensor was at the trough stage, the abutment pressure was at the peak stage, with the increase of sensor buried height, and the supporting pressure and the strain value had a linear relationship within the range of the advanced abutment pressure. The conclusion shows that the fiber Bragg grating sensor monitoring technology has good effect on the internal strain and key supporting pressure monitoring of the overburden in the model test; it provides new monitoring methods and means for the model tests.

The reserved thickness of top coal has an important influence on the stability of a large section open-off cut under gob in the thick seams slicing mining. The destabilization extremum conditions of the open-off cut top coal were derived from by elastic–plastic theory, and the optical fibre sensing technology was utilized to monitor the top coal deformation law with different thicknesses (3, 3.5, and 4 m) in the physical similar simulation experiment in the paper. The results show that the top coal thickness is greater than 3.4 m without tension cracks. In the vertical direction, the top coal of the large open-off cut is divided into mining and excavation disturbance zones under the influence of the upper slice coal mining and the excavation disturbance. In the direction of the span of the top coal can be divided into the roof fall risk zone and the warning zone. The deformation changes from exponential to linear to logarithmic in the roof fall risk zone, and it changes from linear to logarithmic in the roof fall warning zone as the number of excavations increases. The sinking amount in the two zones is smaller as the thickness of the top coal becomes larger. It is comprehensively determined that the thickness of the top coal of open-off cut is set as 3.5 m, the stability is moderate, and the field application shows that the integrity of the top coal is good after support, and the maximum off-layer value is 6 mm, which can satisfy the production requirements.