Underground roadway excavation, for large ground stress and broken rock conditions, the current practice is to select the supporting form according to the purpose and service life of the roadway, that is, to stabilize the rock mass by means of support, so as to ensure that the roadway is not deformed, but the actual production It is found that only by means of support, not only the consumption of supporting materials is large, but also it is often difficult to maintain the original contour of the roadway. It is difficult to repair the roadway after deformation and the safety risk is high. Therefore, for the high-stress fractured rock mass, the maximum principal stress direction should be determined first. Secondly, the reasonable roadway contour surface should be selected according to the stress distribution. Finally, the support material and grade should be determined, so that the ground stress can be effectively utilized and the support material can be reduced. The force can make the roadway more stable.
1 High stress broken rock mass support
1.1 Steel arch combined with anchor net spray support method The Jianchaling Nickel industry rock is mainly composed of slippery magnesia . It is easily muddy when exposed to water, and the phenomenon of exposed weathering in the air is serious. Therefore, in this type of rock excavation, The anchor net spray is carried out in time to close the exposed surface of the rock mass and prevent the rock from weathering the flakes in the humid air under the well. For the roadway with long service time, due to the fracture of the top rock mass, only the anchor network spray is used to close the rock face, and the stability of the roadway cannot be maintained. In order to avoid the deformation of the roadway, the steel arch frame and the anchor net spray support are often used, as shown in Figure 1. Show.
The field application shows that although the support method can maintain the stability of the roadway for a period of time, the time is relatively short. The Jianchaling nickel mine can stabilize the roadway for 8 months or so. The introversion occurs first, and the deformation increases with time, as shown in Figure 2. It can be seen from Fig. 2 that after the two sides of the wall are converged and deformed, the steel arch frame is bent and deformed, the original anchor net support breaks with the deformation of the roadway, and the anchoring effect is lost. At the same time, the steel arch frame is in the horizontal direction without restraint deformation. Binding force, so the loss of resistance horizontal stress F1, with the horizontal stress, its introversion deformation is increasing, and by the force of the bottom rock mass on the steel arch F3, it still has a certain resistance to vertical stress F2.
For high-stress fractured rock masses, after inward deformation on both sides of the roadway, the bottom corners of the steel arches begin to produce lateral internal pressure on the floor of the roadway, causing the bottom rock to move inward. Due to rock fragmentation, water accumulates in the floor of the roadway. Under the action, the rock undergoes expansion and deformation, and is affected by lateral internal stress. The floor of the roadway slowly bulges out and changes with time, and it bulges continuously. Pedestrian transportation is inconvenient. If the tunnel is used for transportation, the floor is convex and deformed. The track is undulating and must be repaired, which increases the cost of repair.
1.2 Back cover combined steel arch anchor net spray support Jianchaling nickel mine for the statistical analysis of the fractured rock mass for many years, the high stress fractured rock steel arch frame combined with anchor net spray support deformation mechanism: steel arch anchor bracket joint supporting techniques the production found in practice that the roadway and the bottom case slate rock crushing of cement, the bottom plate and therefore decrease the stress level of two steel arch foot, at the level of stress, the first steel arch The inner side moves at the foot, and the inner side moves to pull off the anchor support, which causes the steel arch to lose the horizontal stress binding force, thereby promoting the horizontal rock deformation, and the horizontal inner side movement produces lateral pressure on the bottom plate, so that The bottom plate moves upwards, and finally the deformation of the bottom plate intensifies the horizontal movement. Therefore, it can be said that the deformation of the floor of the roadway and the horizontal deformation are complementary, the horizontal deformation causes the bottom plate to protrude, and the bottom plate protrudes to further aggravate the horizontal deformation.
According to the deformation mechanism of the Jiankeling nickel ore support, it can be found that the integrity of the rock in the roadway floor plays a decisive role in the stability of the roadway. If the rock integrity of the floor is poor and no support measures are taken, the support force of the floor rock will inevitably decrease. This is also the initial stage of soft rock deformation. In order to change this phenomenon, it is necessary to take corresponding measures against the bottom rock so that the supporting force will not be reduced under external conditions or the original integrity can be maintained for a long time. To this end, the Jianchaling Nickel Mine proposed a concrete sealing process. By laying a layer of concrete on the floor of the roadway, it effectively blocked the influence of external factors on the damage of the rock to ensure the integrity of the rock and maintain its own compressive strength. The roadway does not deform and damage. The process technology also has certain drawbacks, that is, the thickness of the back cover is difficult to control, and the thickness control is unreasonable, and the crack occurs in the weak portion of the bottom plate.
2 Mine roadway layout and support method confirmation
According to the geological and topographic conditions of the mine, the ground stress of the mine is detected, the ground stress distribution of the mine area is understood, the maximum principal stress direction is understood, and the underground mining project is rationally arranged according to the direction of the maximum principal stress, and the maximum principal stress direction can be utilized in the design. The roadway and the stope are paralleled, and the maximum principal stress is directly avoided to directly act on the roadway. Otherwise, the roadway construction process is difficult and the support level is high, and the maintenance of the roadway is difficult and the maintenance cost is high.
The Jiankeling nickel ore is broken and the water is easily muddy. The three-heart arch profile is used in the design of the roadway. Due to the maximum principal stress in the horizontal direction, the floor of the roadway is easy to move up, causing inward deformation at the bottom of the wall and ultimately affecting the roadway. use. Through the investigation and analysis of production practice, the roadway deformation is fast and the repair rate is high. The main reason is that the Jianchaling nickel mine is unreasonable for the contour design of the broken rock roadway. The three-core arch section is suitable for the area with large pressure, but for the horizontal pressure. The area should not be used.
In the later repair, the Jianchaling Nickel Mine changed the original design method. The artificially lowered bottom measures were used to weld the arch beams at the bottom of the steel arches on both sides of the wall, and then buried on the bottom plate after the bottoming to make the roadway section The contour changes to a horseshoe shape to better withstand horizontal stresses. After changing the profile of the roadway section, the repairing roadway of the Jianchaling Nickel Mine can basically maintain stability and reduce the maintenance cost of the roadway.
In addition, the Jianchaling nickel ore support deformation, the new support materials are used to replace the deformed materials in the repair construction, but it is found that after replacing the new support materials, the roadway is quickly deformed again, and the analysis results show that the support deformation It is not the influence of single side force, but various factors are related to each other. Therefore, when selecting the support method, the physical and mechanical properties of rock should be analyzed first, and the reasonable support method should be determined by combining physical and mechanical properties and stress distribution.
3 Conclusions (1) The broken rock mass must be sealed. For the broken rock mass, especially the easy muddy rock mass, the control of the bottom plate is of great significance in the support. If only the top pressure and the side pressure are supported, the entire support will be ineffective due to the damage of the bottom plate, so according to the actual rock The bottom plate is reinforced with different backing measures to achieve overall stability.
(2) Reasonably select the section according to the stress situation. Under normal circumstances, the magnitude and direction of the ground pressure acting on the roadway play a major role in selecting the shape of the roadway section. When the top pressure and the side pressure are not large, a rectangular or trapezoidal section may be selected; when the top pressure is large and the side pressure is small, a straight wall arch section (semi-circular arch, arc arch or three-heart arch) shall be selected; When the top pressure and the side pressure are large and the bottom drum is severe, a closed section such as a horseshoe, an ellipse or a circle must be selected.
references:
[1] Xiong Jianping. Research on ground stress and fracture [J]. Petrochemical applications, 2011,30 (4): 14-16.
[2] Zhang Xiao. Research on ground stress field based on ground stress measurement [J]. Coal mining, 2012,17 (2): 23-25.
[3] Run Wenyu, Nie Dexin, Shang Yuequan, et al. Study on engineering characteristics of weak layer under ground stress [J]. Chinese Journal of Geotechnical Engineering, 2002, 24(5): 584-587.
[4] Xue Yu. Discussion on roadway support in soft and broken coal rock mass [J]. Shandong Coal Science and Technology, 2014, (9): 29-30.
Article source: Mining Technology; 2017.17(2)
Author: Lu Yang Hai, Zhou Xu; Shaanxi Jianchaling Nickel Industry Co., Ltd., Shaanxi Lueyang 724 300
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