Law of coal caving behind the flexible shield support in pseudo-inclined working face

Complex boundary conditions are the major influencing factors of coal caving law in the pseudo-inclined working face. The main purpose of this study is to analyze coal caving law of flexible shield support and then to establish the internal relations among coal caving parameters under complex boundary conditions. Firstly, the law of coal caving in different falling modes is simulated physically. Secondly, the coal caving shape, displacement field, and contact force field is simulated. Then, coal caving law and process parameters is analyzed theoretically. Finally, the test was performed in Bai-Ji Mine. The research shows that ellipsoidal ore drawing theory has universal applicability in coal drawing law analysis and parameter optimization. After the Isolated Extraction Zone and Isolated Movement Zone reach the roof, the expansion speed is marked by a short delay, and then, while expanding to the floor, two butted incomplete ellipsoids are formed. There is a time-space difference in coal caving after the support, and some coal will be mined in the next round of coal caving. There are obvious differences in the coal loosening range, displacement field, and contact force field on both sides of the long axis. When the support falls along with the bottom plate, it is more conducive to the release of coal. The test shows that the research is of great significance for optimizing the caving parameters of flexible shield support in the pseudo-inclined working face of the steep seam.

Failure Characteristics and Control Technology of Surrounding Rock in Deep Coal Seam Roadway with Large Dip Angle under the Influence of Weak Structural Plane

In view of the unsymmetrical large deformation and failure phenomenon that often occurs after the excavation and support of the roadway in steep seam with weak structural plane, the numerical simulation analysis and engineering application research on the deformation and failure characteristics of its surrounding rock are carried out. The results show that the key position of asymmetric deformation is near the weak structural plane and the intersection of the roadway section and the inclined direction of the rock. On this basis, the “unsymmetrical high prestress pressure relief coupling control technology” is put forward, and the industrial test is carried out. The practice shows that the unsymmetrical coupling support technology can not only effectively solve the differential deformation of the surrounding rock but also ensure the coordinated deformation of the support structure and the surrounding rock, thus improving the overall stability of the roadway, greatly reducing the repair rate of the roadway, and saving the support cost.

Characteristics of the Roof Behaviors and Mine Pressure Manifestations During the Mining of Steep Coal Seam

A steep seam similar simulation system was developed based on the geological conditions of a steep coal seam in the Xintie Coal Mine. Basing on similar simulation, together with theoretical analysis and field measurement, an in-depth study was conducted to characterize the fracture and stability of the roof of steep working face and calculate the width of the region backfilled with gangue in the goaf. The results showed that, as mining progressed, the immediate roof of the steep face fell upon the goaf and backfilled its lower part due to gravity. As a result, the roof in the lower part had higher stability than the roof in the upper part of the working face. The deformation and fracture of main roof mainly occurred in the upper part of the working face; the fractured main roof then formed a “voussoir beam” structure in the strata’s dip direction, which was subjected to the slip- and deformation-induced instability. The stability analysis indicated that, when the dip angle increased, the rock masses had greater capacity to withstand slip-induced instability but smaller capacity to withstand deformation-induced instability. Finally, the field measurement of the forces exerted on the hydraulic supports proved the characteristics of the roof’s behaviors during the mining of a steep seam.

Distribution of Underground Pressure Law and Fracture Zone Prediction Research of Overburden in Steep and Multiple Coal Seams Mining

Use Taiping coal mines second horizontal (+1100m~+900 m level ) 1#, 3# and 5# coal seam in Panzhihua Baoding as the research object, apply the problem solving nonlinear large deformation finite difference method (FLAC), to research the steep multi-seam mining of pressure distribution and characteristics of fracture zone. The results show that: (1)During the course of three coal mining extraction, the stress of goaf surrounding rocks will be changed. (2)When the nearby coal is mining, the coal pillar come into being stress concentration near the area. when the mining work continues, the goaf will have an effect on the protection pillar, which is similar to the "liberate". the effect of coal pillar and stress concentration nearby will be eased; (3)After the coal mining, plastic failure has occurred over the protection pillar, forming a water guide channel. Research results can be as a reference for similar steep seam mining.

Numerical Modeling of Subsidence-Induced Stress on the Pipeline in Steep Seam Mining

In China, surface subsidence caused by steep coal seam mining has affected the safe operation of pipelines in recent years. The study site is one coal mine, where the gas pipeline from Shanshan to Urumqi is across. FLAC3D was adopted to study subsidence-induced stress on the pipeline, and the numerical model was calibrated with the measurement data. Visualization of alarm levels on the pipeline was obtained by integrating the usage of Fish function embedded in FLAC3D and Tecplot. The simulations reveal that the stress on the pipeline is closely related to the excavation depth. The stress on the pipeline increases with the excavation depth increasing when mining the 1st, 2nd, and 3rd levels, whereas the stress on the pipeline decreases slightly with the excavation depth increasing when mining the fourth, fifth, and sixth levels. The maximum stress on the pipeline occurs after mining the 3rd level. The possible damage to the pipe is at the upper-right side. Therefore, the results are helpful to prevent and reduce the impact of subsidence on the pipeline.

The Parameter Identification of the Steep Seam Goafs Structural Characteristics of the Coal and Rock Based on GPR

Identifying the rock mass structure is crucial for disaster control and safe mining.In the south tunneling lane of the original +600 level, using detection method of GPR (Ground Penetrating Radar ) to implement the sophisticated detection of failure characteristics, groundwater and rock structure of the upper goaf. It determines the goaf structure parameters and water conditions through the comparative analysis of the information image. The result shows: there is no large goaf, the coal seam is broken seriously in part section and water is rich in the detection range (200m) from 2650 to 2850. The coal is hypostatic and whole in the section above 20m. It has a great significance to the safety of deep mining design and the prevention for disasters of the steep thick coal seam.

Prediction of Top Coal Caving Ability Based on Support Vector Machine

This paper selected the factors as the coal mining depth, coal seam thickness, the dips, partings, main roof of the top coal caving as indicators, used the categorical data of the steep seam from domestic mining area as training samples for training. Based on one to one classification of SVM, the top coal caving ability prediction model was established. The example results show that the model prediction method is feasible, the prediction results have very high accuracy and reliability, and has certain promotional value.

The Stability Control Technology of Crosscut while Mining without Coal Pillar in Steep Seam

In order to improve the mining benefit of coal resources, Chang Gouyu Coal Mine carried out the technology of mining without coal pillar in steep seam. The key of the technology was to ensure a long-term stability of the cross-entry roadway across the seam. Through the analysis of the nature of steep seam roof and floor rock, and based on the stability analysis and loose circle measured of surrounding rock of crosscut roadway, we brought forward adopting shotcrete rockbolt mesh and U-shaped steel complex support structure system. This complex support system could flex lengthways and compress in radial direction. The entirety integrated with the surrounding rock, and they formed into a whole. Application of the complex support system could effectively control the deformation of the surrounding rock collapse, and maintain the stability of the crosscut.