After Hemushan iron ore mine Hemushan diorite occurs in the contact zone with the limestone and the limestone near the contact strip, the thickness of the ore body 8 ~ 102m, the general inclination of the plates is 40 ° ~ 50 °, steeper portion 60 ° ~ 70 °. The ore is mainly loose and powdery, with poor stability. The sub-column sublevel caving method is used for mining. The extra-vehicle roadway above the middle section of -200m is arranged in the direction of the ore body of the ore body. The approach is arranged perpendicular to the direction of the ore body and is retracted from the upper plate to the lower disk. During the actual mining process, the ground pressure activities are frequent. In the middle stage of -100, -150, -200m, the roadway is seriously damaged by the ground pressure during the mining process, and the roadway roof and side gangs have different degrees of collapse, resulting in multiple mining tunnels. The project could not be constructed, resulting in a low ore recovery rate. As the mine is deep-exploited, the sloping area formed by the sublevel caving method [1-2] and the ground-rock activity caused by the soft and broken rock properties of the post-and the Lushan ore section will continue to intensify, and the mining roadway will continue to be intensified. Cracks, misalignment, roof fall and other conditions will be further aggravated, which has affected the safe production of mines. In order to recover the ore safely and efficiently, and to improve the recovery rate of the Houhe and Lushan ore sections, it is necessary to conduct detailed analysis of the post-production and mining sequence, support mode and ground pressure activities of the Houshan and Minshan mine sections.
1 lane deformation analysis
A comprehensive analysis of the monitoring data of the -200m section of the post-Hebei mining section and the exploration results of the surface subsidence area (Fig. 1) shows that the most severe stress response to the ground pressure is the ore body and the lower part. Part of the powdery ore body in the middle of the ore body. The original support method adopts anchor net spray support structure, and adopts ordinary resin anchor rod, the specification is 20mm×1800mm, the anchor hole diameter is 28mm, and the anchor is strengthened by a roll of fast 2350 resin coil. The length of the bolt is not less than 400mm. The anchoring force is not less than 80kN. The pallet adopts flat high-strength pallet, the specification is 100mm×100mm×4mm (length×width×height), the spacing between the rows is 900mm×900mm, the steel mesh is welded with 6.5mm steel bar, and the mesh size is 100mm. ×100mm. Shotcrete strength grade C20, mix ratio 1:2:2, blended with 3% to 5% accelerator, 100mm thick. For the deformation roadway, a steel arch frame made of 200 mm × 75 mm × 9 mm (length × width × height) is used for secondary support. When the roadway is compressed and deformed, the depth of the loose rock of the soft rock roadway with a span of 3.5m is 1.5~2.0m. The long bolt of 1.8m can not guarantee the stability of the roadway, the whole roadway sinks, and the tray is easy. Shedding, secondary support steel arches are easily deformed after being pressed, and cannot be repaired and strengthened.
2 Surrounding rock stability and roadway support
2.1 Roadway deformation and anchor force monitoring
The monitoring of the bolts of the -200m horizontal recovery roadway (Fig. 2), the -212.5m lower disk outer lane and the 9#~11# approach shows that the post-Heshan-200,-212.5m section horizontal roadway In the extremely soft rock stratum, its main features are extremely weak, loose and broken, and the softening and ore body pulverization phenomenon is significant, which makes the mechanical properties of the surrounding rock significantly reduced and accompanied by the expansion and expansion deformation, and it is impossible to implement effective active support. Protection, so that it can not form a stable and reliable active support, which aggravates the deformation and damage in the late stage of the roadway. Due to the stress adjustment of the surrounding rock and the sag of the rock mass, there is a certain hysteresis, which leads to the failure of the anchorage of the construction bolting network. . The interaction of these factors causes the surrounding rock and the support body to be completely destroyed, losing the structural and bearing capacity, and it is easy to cause some of the bolts in the bolting and shotcreting support of the roadway to be squeezed out and fail, and a complete branch cannot be formed. The structure is protected, which causes the surrounding rock of the roadway to be unstable and degenerate.
2.2 support plan selection
Combine the experience of -200m segmental ore recovery and fully consider the factors such as safety, ore recovery cost and ease of construction. -212.5m section ore body under the roadway and mining access road with a specification of 3800mm × 3200mm three-core arch section. The support schemes for some roadways with -200m level and -212.5m segment are: 1 Use smooth blasting technology to reduce the damage to surrounding rock, and reserve 150mm deformation on each side to release the deformation energy of surrounding rock. 2 The first anchor net spray support, to prevent the roadway from roofing, to ensure the basic stability of the surrounding rock of the roadway, to close the surrounding rock in time, to prevent the weathering of the surrounding rock and reduce the strength, and to flatten the unevenness of the surrounding rock section to ensure the formation of the roadway Good and uniform force; 3 pairs of roadway deformation parts, secondary support after pressure release, secondary support using pre-stress to make pressure anchors and steel joist anchors. For the first anchor net spray support, the appropriate deformation amount is reserved, the bolt parameter is 20mm×2400mm (Fig. 3); the second prestress is used to support the anchor bolt, and the bolt parameter is mm20mm×2400mm (Fig. 4).
-212.5m segmentation 9#, 10#, 11# approach deformation monitoring results (Figure 5) shows: 1 the deformation of the roadway within 3 months is less than 120mm; 2 the tray does not fall off; 3 roadway does not occur The overall sinking and collapse phenomenon. It can be seen that the support method proposed in this study can meet the safety requirements of roadway.
3-212.5m sectional mining engineering layout and optimization of mining sequence
3.1 mining engineering layout
(1) Lower scheme. The advantage lies in the fact that it has been consistent with the existing wells and slopes, which is conducive to the recovery of ore in the lower plate; the outer roadway is easy to be deformed, the secondary support is large, and the section mining is severely deformed to the middle and late stages, resulting in the ore being unable to be fully recovered. The ore body is long and easy to deform.
(2) On-board plan. The advantage is that the outer roadway is stable and the recovery time is sufficient; the disadvantage is that it is not suitable for the full recovery of the lower ore, and the middle powder ore body is long and easy to deform.
(3) Upper and lower joint plans. The advantage is that the external roadway is stable and the recovery time is sufficient, which is conducive to the recovery of ore in the lower plate, and there are many mined surfaces, which are easy to fall off the ore; but it is relatively easy to increase the amount of engineering. In this study, the mining layout of the upper and lower combined mining is taken from the middle to the sides.
3.2 Recovery sequence optimization
The main mining sequence of the sublevel caving method without pillars: 1 sequential mining, from the upper layer to the lower layer, from the left side of the ore body to the right side of the ore body; 2 from the two ends to the middle, from the upper layer to the upper layer The lower layer starts from the two ends of the ore body and gradually recovers from the middle part of the ore body; 3 from the middle to the two ends, from the upper layer to the lower layer, starting from the middle of the ore body, and gradually recovering from both ends of the ore body. Vertical displacement analysis shows that the recovery from the middle to the two ends has the least impact on the stability of the approach. Therefore, the 212.5m section adopts the combination scheme of the upper and lower discs for the mining arrangement, and the mining sequence from the middle to the two ends. The structural parameters of the stope are 12m×12.5m (input spacing 12m, stratification height 12.5m).
4 test analysis
In this study, the support system with the first anchor net spray and the second pre-stress to make the pressure anchor as the core is selected. The upper and lower disc joint scheme is adopted for the mining arrangement and the recovery sequence from the middle to the two ends. The recovery rate of the sublevel caving method without column is about 80%. At present, the test has been carried out on the section of #212.5m section 9#～11#, and the local recovery rate has reached 95% (Table 1), indicating that this study proposes The recovery plan has achieved remarkable results.
5 Conclusion
For the post- and Lushan ore bodies with poor stability, the roadway support method was analyzed and the recovery sequence was optimized. The test shows that the recovery of the -212.5m segmental ore is ideal, for ensuring the Heshan iron ore mine. The high yield and stability of production have certain reference value.
references
[1] Wei Jianhai, Huang Xingyi, Ge Chao, et al. PFC2D-based numerical simulation of no-bottom sublevel caving method [J]. Modern Mining, 2015 (12): 30-31.
[2] Sun Wenyong, Chen Xingming, Wang Wei, et al. Study on reasonable mining technology of residual ore body in the lower inclined medium-thickness ore body without sub-column sublevel caving method [J]. Metal mines, 2014 (2): 12-17.
Article source: "Modern Mining"; 2016.10;
Author: Lee on behalf of the forest; Magang Group Gushan mining companies;
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