Abstract
With the increase of mining height, the problem of coal wall spalling in the working face gradually worsens. Hydraulic support and its face guard structure are the key pieces of equipment to restrain the coal wall spalling. However, at present, the hydraulic jack is mostly considered as rigid in the analysis of protection mechanism. This simplification cannot effectively reflect the true bearing state of the face guard. In order to improve the accuracy of analysis, this study considers the face guard jack as a flexible spring and establishes a rigid-flexible coupling analysis model of the face guard mechanism. First, based upon the multibody dynamics software ADAMS®, the multibody numerical model of the face guard of the hydraulic support was established. The influence of the two kinds of structures on the coal wall disturbance was analyzed and compared. Then, the rigid model was meshed. The hydraulic jacks were equivalent to the spring system, and the rigid-flexible coupling model was established. Based upon the application load on different positions of the rigid-flexible model, the load-bearing characteristics and hinge point force transfer characteristics of the two face guards were analyzed. The results show that the support efficiency of the integral type was higher than that of the split type. In the vertical support attitude, the dynamic disturbance of the coal wall, produced by the two kinds of face guards, was small. The four-bar linkage effectively improved the ultimate bearing capacity of the integral face guard. The results provide theoretical support for the design and optimization of the face guard.
Highlights
In recent years, coal mining and coal consumption have gradually decreased with the increase in support towards reducing carbonization, the total global coal production has still increased by 1.5% in 2019 compared with that in the previous year
It can be seen that the error between the numerical and theoretical results is less than 2.3%, which indicates good consistency. e results of theoretical calculation and numerical simulation are compared and analyzed
(1) When the face guard moves closer to the coal wall, it will form a dynamic disturbance to the coal wall due to the dynamic support effect of the face guard jack. e results show that the dynamic disturbance caused by the two kinds of face guards reaches the minimum when the face guard is nearly vertical
Summary
In recent years, coal mining and coal consumption have gradually decreased with the increase in support towards reducing carbonization, the total global coal production has still increased by 1.5% in 2019 compared with that in the previous year. Based on the “wedge” stability theory, some previous works [15, 16] studied the mechanism of coal wall spalling in fully mechanized mining face with large mining height. They pointed out that the physical properties of coal body, the face guard protection force of hydraulic support, and the protection efficiency affected the stability of coal wall. By establishing the interaction model of hydraulic support and surrounding rock under different roof structures, a previous study [19] analyzed the influencing factors of hydraulic support stability in fully mechanized mining face.
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