Abstract
The deformation and failure forms of inclined coal seam roadway under the joint action of dip angle and various geological conditions are complex, and there is a lack of targeted support measures, which brings great problems to the stability control of roadway surrounding rock. In order to safely and economically mine inclined coal seams, taking the engineering geology of Shitanjing No. 2 mining area as the background, and the physical similarity model of right-angle trapezoidal roadway in inclined coal seam, in which the non-contact digital image correlation (DIC) technology and the stress sensor is employed to provide full-field displacement and stress measurements. The deformation control technology of the roadway surrounding rock was proposed, verified by numerical simulation and applied to engineering practice. The research results show that the stress and deformation failure of surrounding rock in low sidewall of roadway are greater than those in high sidewall, showing asymmetric characteristics, and the maximum stress concentration coefficients of roadway sidewall, roof and floor are 4.1, 3.4 and 2.8, respectively. A concept of roadway "cyclic failure" mechanism is proposed that is, the cyclic interaction of the two sidewalls, the sharp angles and roof aggravated the failure of roadway, resulting in the overall instability of roadway. The roadway sidewall is serious rib spalling, the roof is asymmetric "Beret" type caving arch failure, and the floor is slightly bulging. On this basis, the principle of roadway deformation control is revealed and asymmetric support design is adopted, and the deformation of roadway is controlled, which support scheme is effective.
Highlights
At present, many scholars have studied the deformation control of roadway surrounding rock in inclined coal seam by using the physical model test, theoretical analysis and numerical simulation
Shuai Zhang et al analyzed the stress distribution and deformation characteristics of coal pillar and roadway support gob-side entry in deep inclined coal seam through theoretical analysis and numerical simulation, and concluded that 5 m wide coal pillar can ensure that the coal pillar is at a low stress level, the deformation of roadway surrounding rock is within a reasonable range, and the roadway support is in good condition[13]
Hai Wu established a mechanical model according to the mechanics of materials, analyzed the stress distribution and deformation failure characteristics of vertical wall arch roadway in the deep inclined coal seam, and put forward the control technology asymmetric deformation of the r oadway[16]
Summary
Obtained from the field drilling measurement in Shitanjing No 2 mining area. The roadway section is designed as a right-angle trapezoid with a width of 4.5 m and the low sidewall height of 3 m. Simplifications adopted in the model tests are given as follows: (1) The cross-section of right angle trapezoidal roadway in the inclined coal seam with the dip angle of 23° in Shitanjing No.[2] Mining Area is used; (2) No support system is considered, in order to reveal the source of roadway deformation and failure; (3) The influence of roadway excavation process is not considered. (1) Stress monitoring of roadway surrounding rock According to the deformation and failure characteristics of inclined coal seam roadway in the actual project, and throughout the backfilling process, a total of 19 stress force sensors are embedded in the rock mass around the roadway (the roof, two sidewalls, floor and four sharp corners of the roadway) as schematically presented in Fig. 4 to measure the variation of rock stress during the roadway excavation and the surcharge loading process. It can realize the high precision test of large range and detail parts of rock strata simultaneously, complete the continuous dynamic monitoring of similar material models,
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