0 Preface
Montenegro # 1 iron ore mine tunnel is open to Underground mining engineering sluice channel open pit, play an important role in the open pit drainage in the rainy season, and the opening of the tunnel in the role of the non-rainy season and into action, because the surrounding rock tunnel The fissures develop, the weathering of the rocks is serious, the strength of the rock mass is low, and it is close to the surface. During the process of tunneling to the surface, a large area of ​​the east exit of the tunnel will fall and affect the tunnel. The problem of the fall of the tunnel needs to be solved. Based on the rock fall problem of Heishan Iron Mine 1# tunnel, based on the field investigation and calculation analysis, the numerical simulation software ANSYS was used to analyze the numerical simulation stability of the unstable 1# tunnel of Heishan Iron Mine. Based on the simulation results, a plan for the management of the roof area was formulated.
1ANSYS model establishment
This simulation uses ANSYS numerical simulation software. According to the actual situation of the site, a 1/2 three-dimensional model is built. As shown in Figure 1, the model is 60m high and 82m wide. The upper step is 8m wide, the lower step is 20m wide, and the middle is 1/2 tunnel model. The tunnel height is 5.5m. The width is 5m and the tunnel simulation length is 45m. The rock mass mechanical parameters used in the simulation are shown in Table 1.
2 simulation results and analysis
2.1 Displacement analysis
The displacement cloud diagram of the model in the x, y, and z directions is shown in Figure 2.
It can be seen from Fig. 2 that the region where the displacement in the x direction is large is mainly at the top platform and the exit of the tunnel, and the region where the y direction is greatly deformed is mainly the position of the top of the tunnel and the top of the slope above it, and the region where the displacement in the z direction is large is mainly the tunnel. The slope above the exit. According to the comprehensive analysis, the upper step is too steep, resulting in a large displacement at the exit of the tunnel. The maximum displacement in the vertical direction is 79 mm, which has exceeded the maximum allowable displacement of 50 mm, which may cause the tunnel exit to collapse. In addition, the deep displacement deformation of the tunnel is relatively large, which adversely affects the stability of the deep roadway.
2.2 Stress analysis
The stress cloud diagram of the model x, y, and z directions and the shear stress cloud diagram of the xy plane are shown in Fig. 3. It can be seen from the stress cloud diagrams in the x, y, and z directions that the stress at the foot of the tunnel exit and the top and bottom of the deep tunnel are both large.
It can be seen from the shear stress cloud diagram in the xy direction that the upper edge of the tunnel exits the shear stress concentration phenomenon, and the deep shear stress of the tunnel is large. According to the comprehensive analysis, the stress at the upper edge of the tunnel exit and the lower edge of the tunnel is relatively large, especially the shear stress concentration at the upper edge of the tunnel. The maximum shear stress has reached 0.625 MPa, exceeding the maximum of the rock layer. The shear strength is 0.28 MPa, which may cause shear failure at the exit of the tunnel. In addition, from the exit to the deep part of the tunnel, the stress on the top and bottom of the tunnel is gradually increased, and tensile stress is present. The maximum tensile stress reaches 0.72 MPa, which causes instability of the top and bottom of the tunnel.
2.3 strain analysis
The x, y, and z direction strain clouds and the xy direction shear strain cloud are shown in Fig. 4. It can be seen from the strain cloud diagrams in the x, y, and z directions that the strain at the foot of the tunnel exit and the top and bottom of the tunnel are relatively large. It can be seen from the shear strain cloud diagram in the xy direction that shear strain concentration occurs at the upper edge of the tunnel exit, and The deep shear strain in the tunnel is large. According to the comprehensive analysis, the strain at the upper edge of the tunnel exit and the lower edge of the tunnel is relatively large, especially the shear strain concentration at the upper edge of the tunnel, which may cause shear failure at the exit of the tunnel. In addition, from the exit to the deep part of the tunnel, the strain on the top and bottom of the tunnel is gradually increased, resulting in instability of the top and bottom of the tunnel.
3 caving area treatment plan
The treatment of the landing zone should follow the following principles: safe and reliable construction, small amount of treatment, low cost, simple and easy construction, short construction period, and provide experience for subsequent similar projects. According to this governance principle, on the basis of on-site investigation, combined with the actual situation of the mine, a scheme for pouring cement mortar is proposed.
(1) First close the landing zone in the tunnel. The concrete is sprayed in the landing zone of the tunnel to close the landing zone.
(2) The second step is to infuse the mortar. After the shotcrete was cured for 2 days, the caving area was grouted on the outer slope. The loose body is filled and reinforced by the consolidation grouting method. Grouting uses natural height differences and relies on gravity to provide pressure. The piping arrangement of the grouting equipment is shown in Figure 5. The purpose of consolidation grouting is to fill the voids of the loose body, cement it and enhance the integrity of the rock mass.
(3) Implement advanced support. After the filling of the grouting for one week, it created a good environment for the second hole in the tunnel. Take the lead bolt eye in the tunnel and install the lead bolt.
(4) Secondary excavation. Under the support of the advanced anchor, the secondary blasting construction is carried out. The construction adopts a multi-hole, less charge, short-drilling construction method, and excavation and side support.
4 Conclusion
(1) For the problem of tunnel rock caving, the ANSYS numerical simulation software is used to study the tunnel displacement, stress and strain. The analysis shows that the stability of the rock mass at the exit of the tunnel is the worst, and the maximum displacement in the vertical direction is 79mm. The maximum allowable displacement is 50mm, followed by the deep bottom plate of the tunnel. The maximum shear stress of the rock layer has reached 0.625MPa, exceeding its maximum shear strength of 0.28MPa, and the maximum tensile stress is 0.72MPa, and the rock formation is unstable. The development of an unstable tunnel management program provides some theoretical guidance.
(2) According to the numerical simulation results, it is determined that the reinforcement treatment scheme of the tunnel landing zone is cement mortar. The scheme is simple in process, low in cost, good in construction safety and small in overall engineering quantity. The mine practice shows that the scheme controls the settlement displacement of the rock mass above the tunnel to within 50mm, and reduces the shear stress of the tunnel rock layer, and the maximum shear stress is controlled within the range of 0.28MPa, which enhances the stability of the tunnel. Sex.
references:
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[3] He Manchao, Li Guofeng, Ren Aiwu, et al. Stability analysis of three-dimensional intersecting chamber group in deep soft rock roadway [J]. Journal of China University of Mining and Technology, 2008 (02): 167-170.
[4] Zhang Huawei, Peng Wenqing. Study on stability of surrounding rock of large section coal bunker chamber with bolt grouting combined support[J]. Journal of Hunan University of Science and Technology (Natural Science Edition), 2008 (03): 14-17.
[5] Wang Wei, Wang Hao, Guo Zhiwei, et al. Stability control strategy for chamber group of deep well high stress and strong expansion soft rock pump house [J]. Journal of Mining and Safety Engineering, 2015(01):78-83.
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Source: Mining Technology: 2016, 16(4);
Copyright:
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