The large-scale development and utilization of mineral resources has caused many mines to face the danger of depletion of resources [1-2]. Due to the influence of ore deposit form, geological exploration degree, mining method, investment recovery period and other factors, in the process of ore mining, there are often phenomena such as mining and abandoning poverty, mining and abandoning difficulties, resulting in a large number of residual ore bodies in the underground. And high grade, very
With recycling value. Therefore, the safe and efficient recovery of residual mineral resources has become a major problem in the mining industry [3-4].
Geological overview of 1 residual ore body mining
Metro gold deposits Yi Mu fracture zone is located east of Shandong raised northwest, north wing Qixia anticline, Huangxian - Nancy YeXian arcuate end fault, i.e. a fault coke home, and fractured geologic structure more developed. The fault zone runs 40° northeast, tends to northwest, and has a dip angle of 26°-30°. The 1# ore body, which is close to the surface, is the main ore body, which has been basically mined. Only the upper residual ore and a small amount of ore below -470m level have not been mined. The whole rock is relatively stable, and most of the roadway does not need support, but the surrounding rock is broken and the crack is relatively developed [5-6].
Ore body plate rocks mainly phyllic, phyllic granitic rock fragmentation, sericite silicide lower plate of porphyritic granodiorite. The ore body is found in the igneous or silicified and sericitized granodiorite fragmentation rocks of the Yellow Iron . The strength of the surrounding rock and part of the ore body of the ore body is relatively high, and the Platts coefficient is 8-10. The hydrogeological conditions of the mine are simple [7-8].
2 ore rock physical and mechanical test
In order to reflect the rock mechanics parameters of the surrounding rock and ore body, the electronic balance, vernier caliper, WEP-600 microcomputer control screen display universal testing machine, 100t pressure sensor, Kaitian 4600 computer and corresponding plotter (Fig. 1) are used for mining. Rock physics and mechanics test. Sampling the downhole-120m ore body and processing it into rock specimens, as shown in the figure
2, the physical and mechanical parameters of the obtained ore are shown in Table 1.
3 ground pressure test
Surrounding rock stress and deformation are the result of comprehensive influences of geological and mining factors, and are the key factors for evaluating the safety of on-site excavation work. They are also important indicators for judging whether the stope needs to adopt support measures, support methods, and inspection support effects. . The layout of the 1407 stope is shown in Figure 3 [9-10]. The four sections of the 1407#, 1408#, and 1409# stope are effectively measured, as shown in Figures 4-6.
(1) During the process of road mining, with the advancement of mining, the pressure and displacement of each section in the inlet roof have different degrees of change. The horizontal pressure of the section 1# is the largest, 14.5 MPa, which is more than three times the vertical pressure change; the horizontal displacement and the vertical displacement are relatively large, and the other sections are slightly smaller than the 1# section, but the overall change law is similar.
(2) The change of pressure and displacement of the measured section is related to the advancement distance of the approaching direction. The initial stage changes sharply and grows rapidly. After the 5~6m of mining is promoted, the change value tends to be stable.
4 Determination of the width of the mining approach
4.1 Mechanical model establishment
After the approach is adopted, after the ore is produced, the direct top is a layered ore body or an artificial false top, and the tail sand is filled above the false top. Therefore, the direct top of the width of the mining approach is divided into two cases of layered ore body and artificial false roof bearing [11]. According to the characteristics of the roadway mining, the ultimate stability theory of the beam structure is used to analyze the width of the ore body or the artificial false roof, and the mechanical calculation model of the beam structure is established, as shown in Fig. 7. Let the horizontal and vertical stresses be p, q, respectively.
4.2 Determination of maximum deflection
(1) Maximum deflection calculation.
It can be known from equation (1) that the deflection is linear with the vertical load and nonlinear with the horizontal load. As the horizontal force changes, the maximum deformation will occur in the middle of the beam, ie x=l/2. Maximum deflection [12] is
(2) Maximum allowable deflection calculation. Allow the tensile stress of the beam to be
The deformation of the approach is proportional to the fourth power of the width of the approach, that is, the width is doubled, the amount of deformation is increased by 16 times, that is, the width of the approach is doubled, and the horizontal critical load is reduced by 4 times. For mines with large horizontal stresses, large-width access mining may cause domes due to horizontal forces. Therefore, in the mining of the Xincheng gold mine, it is advisable not to increase the width of the approach as much as possible, and the width of the approach tunnel is 4-6 m and the length of the approach is 30 m.
5 Conclusion
(1) For the recovery of the top and bottom column residual ore, the surrounding rock of the test section has low shear strength, and the surrounding rock of the lower plate has greater shear strength than the surrounding rock.
The fracture surface of the Jiaojia main part of the upper part of the ore block has a fault mud of 10-20 cm thick, which is easily softened when exposed to water.
(2) Sampling was carried out on the upper plate, ore body and lower plate of the -120m remnant mining section, and density test, uniaxial compressive strength test, tensile strength test and shear test were carried out respectively.
(3) Through the field test, the original rock stress field of the residual mining area and the relationship between the pressure and displacement of the inlet roof during the road mining process are obtained.
(4) When the vertical principal stress of the approach is applied, the stress and stability of the approach are the worst; when the approach is parallel to the principal stress, the force and stability of the approach are the best. Applying limit analysis method and thin plate theory, according to 1407# stope
In actual conditions, the approach width of the stope is calculated to be 4 to 6 m and the length of the approach is 30 m.
references
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Article source: "Modern Mining"; 2016.11;
Author: Yan Bing ultra-; Shandong Mining Group Co., Ltd;
Copyright:
Waist Fan,Waist Fan Usb,Summer Waist Clip Fan,Multifunctional Waist Clip Fan
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