1、 翻译部分 Research on support bearing and top coal stability of fully mechanized caving face in deep mine ABSTRACT: On the basis of geological and production conditions of 34223 fully mechanized caving face in Quantaicoal mine, the distribution of displacement field of top coal deformation is analyzed b
2、y means of UDEC3.0 numerical calculating method, which indicates that the top coal deformation shows a characteristic offront-to-back dynamic unstable areas. And the impact of support rigidity and rotation angle of main roof on support bearing and on top coal deformation is investigated. Last, the f
3、easibility of light-duty support used in fully mechanized caving face is also analyzed. introduction Along with the wide application of top coal caving technology in fully mechanized mining face, the powered support for the top coal caving shows a variety of development. And compared with the high-r
4、esistance powered support for top coal caving, the light-duty support for top coal caving is in common use due to such advantages as the lower working resistance, lower cost, light weight, and the convenient operation. With the increase of mining depth, the face condition of “isolated island” formed
5、 by the mining sequence and the high stress caused by deep mining results in a superimposition of rock stress in working face, which has a great impact on the rock and coal control and on the safetyin production. Under this condition, whether the light-duty support for top coal caving can be used su
6、ccessfully or not to realize a safe mining of a thick coal seam has become a hot topic. In this paper, on the basis of geological and production conditions of fully mechanized caving face with deep high stress in Quantai colliery, UDEC3.0 numerical calculating method is used to analyze and discuss t
7、he relations of the main roof movement and top coal deformation with the support bearing in order to provide some references for rational lectotype of the powered support in fully mechanized caving face in deep mining of thick coal seam. SIMULATED GEOLOGICAL AND PRODUCTIVE CONDITIONS No.3 coal seam
8、is now exploited by 34223 working face of Quantai mine, the thickness of coal seam is 4.5 m, the dip angle is 2 14, averaged by 7. Its Protodyakonov coefficient f is 1.0, being soft in hardness and simple in structure, with a buried depth of 800 m. The inclined length of the working face is 140 m an
9、d the strike length is 708 m. Since the upper and low adjacent coal seams of this working face have already been mined out, during the face mining, the working face will become an “isolated island” form, being pendent in three sides. The immediate roof consists of sandy mudstone with a thickness of
10、3.4 m, and the main roof consists of sandstone with a thickness of 4.6 m. The immediate floor is composed of sandy mudstone with a thickness of 1.7 m. The geological structure of the working face is quite simple. And ZFZ2600-16/24 powered support for lower top coal caving is used as the face support
11、. The setting load of the support is 1950 kN, with a working resistance of 2600 kN and a supporting strength of 0.45 MPa. ESTABLISHMENT OF NUMERICAL CALCULATING MODEL The stability of top coal is influenced by both the support rigidity and the movement of main roof, but it can impact on the support
12、bearing as well. In order to analyze the impact of the support rigidity and main roof movement on the stability of top coal and the impact of the stability of top coal on the working resistance of support, the numerical calculation model is established according to the geological condition of 34223
13、working face (Fig. 1). The model is 150min length and 30min height, with asimulating mining depth of800m. The gravity stress of the upper strata is exerted on the upper boundary of the model. The immediate roof and the top coal in the range of the roof-controlled area of the working face are conside
14、red as an emphasis to be studied. In the calculation model, the excavation of the coal seam starts from the left boundary to make the rotation of main roof form a certain rotation angle. But the rotation angle of the main roof is relevant to the backfilling degree of the goaf, and in the simulation,
15、 the rotation angles of the main roof are determined to be 4.98, 5.81, and 8.16, respectively. The simulated support is replaced by the rod element with certain rigidities, such as 40 kN/mm, 85 kN/mm, and 120 kN/mm, respectively. The mechanical parameters of various strata in the calculating model a
16、re listed in Table 1 and Table 2. Table 1 Simulating mechanical parameters of strata Table 2 Mechanical parameters of joint surface in simulating strata Strata property Normal rigidity jkn/GPa Tangential rigidity jks/GPa Adhesive force jc/MPa Friction angle jf / o Tensile strength jt / MPa Sandstone
17、 20 15 0 40 0 Sandy mudstone 13 8 0 35 0 Coal 3 0.2 0 30 0 Mudstone 6 1 0 30 0 ANALYSIS AND NUMERICAL CALCULATING RESULT Deformation characteristic of top coal If the support rigidity is 80 kN/mm and the rotation angle of the main roof is 5.81, Strata property Density d /g cm-3 Volume modulus K/GPa
18、Shear modulus G /GPa Internal friction angle f/o Cohesion C /MPa Tensile strength t /MPa Sandstone 2.7 26.8 16 45 30 20 Sandy mudstone 2.6 10.8 6 40 27 20 Coal 1.4 4.2 2 20 1 1 Mudstone 2.5 8.8 4.3 32 30 10 the displacement vector distribution of the top coal is shown in Figure 2. From Figure 2, it
19、can be seen that the deformation of the top coal has mainly two areas. The first is the deformation nearby the goaf-side which causes the support to move toward the goaf direction, resulting in the transverse instability of support. And the softer the top coal is, the larger this area will be. The s
20、econd is the deformation at the end face nearby the rib, which results in a serious deformation of the top coal at the end face and an enlargement of fall area.Therefore, according to the deformation characteristics of the top coal in roof-controlled area, the top coal can be divided into two dynami
21、c unstable areas: the front one and the back one. And the joint of both areas will further cause the instability of therockaround the support system. Figure 2 Distribution of displacement vector of top coal Impact of rotation of main roof on top coal stability The rotation of the main roof is an imp
22、ortant factor influencing on the rock deformation, and its rotation angle is relevant to the backfilling degree of the rock fall in the goaf. It can be seen that the vertical and horizontal displacements of the top coal increase with the increase of the rotation angle. But if the rotation angle of m
23、ain roof is small, the displacement is not obvious. The obvious impact of main roof rotation on the top coal deformation is shown in the vertical displacement of upper top coal and the horizontal displacement of lower top coal Impact of support rigidity on stability of top coal The support rigidity
24、is an important parameter to reflect the supporting performance of the support. Usually, to increase the support rigidity is favorable for controlling the roof. But as for the top coal caving, the impact degree of the support rigidity on top coal deformation is different under the influence of the mechanical characteristics of the top coal. . It can be seen that the increase of support rigidity can reduce the vertical displacement of top coal, and finally the vertical displacements of both upper and lower top coals tend to be the same. Meanwhile, the horizontal displacement would
