Analysis of adverse engineering geological factors and control scheme for PD molybdenum ore section

I. Work area geological overview

The mining area is located on the north edge of the northwestern uplift belt of the northwestern part of China, the west side of the Pucheng-Yongtaiyukou north-north fault zone and the Pucheng-Ningde northwest fault zone. Due to the long-term tectonic movement, the north-south direction, the northwest direction and the north-east direction are three groups. The fault structure develops and is distributed in the belt; the magmatic activity is frequent, especially in the late Yanshanian, and the magmatic rocks formed are widely distributed.

Mine strata exposed early Proterozoic units Mayuan group Jin dynasty rock group leptite, Nanshan rock group leptite folder schist, Late Jurassic sandstones in South Park Chang-Lin set the second paragraph of crystal tuff. The intrusive rocks in the ore section are distributed in a near-south-north direction, mainly in the Late Jurassic medium-fine-fine grain granite , medium-fine grain K-feldspar granite, and Heiyun monzonitic granite. Among them, the Late Jurassic medium fine-grained K-feldspar granite is the ore-forming parent rock and ore-bearing surrounding rock of molybdenum ore. The rock in the ore section is fragmented and altered by the influence of structure and hydrothermal fluid. The range of alteration is wide and strong. The rock mass is fragmented to intact from top to bottom, and the relationship between weak and hard is gradually changed. The rock layer is crushed and crushed strongly.

The fault structure of this area is developed, with the north-south and north-west fault structures as the main faults, and the NE-trending fault structure as the second-order, flattened, jointed joints and fissures with jointed joints, and the uneven height of the cracks.

The north-south fault tectonic belt: is the main ore-conducting and ore-bearing structure in the ore section. The fracture zone appears in groups, mostly normal faults, with the characteristics of multi-stage activities after pressure and post-tension. By the broken silicide, yellow iron mineralization alteration veins, fault breccia etc., to expose the tunnel when such breakage, see intermittent dripping, watering local phenomenon, a large amount of water during the rainy season.

The NW-trending fault tectonic belt: developed in the area of ​​the Upper Xikeng in the northern and southern parts of the mining area, with tectonic breccia, altered tectonic or fractured rocks. The fault zone has the characteristics of multiple tension after twisting and twisting. The torsional crack surface is relatively straight and the width is not large. See the scratches. Most of them are filled with yellow iron ore and molybdenite mineralized rocks, and shallow weathered. The effect is affected, the filling is loose, mainly filled with semi-filling, dripping water is seen intermittently in the tunnel, local watering phenomenon, and the water volume in the rainy season is large.

Folded structure: The fold structure in the area is mainly found in the Dajinshan Formation and the Nanshan Formation. The axial direction is mainly north-north and westward. It is formed in the Caledonian period, and the axis is soothing and wavy. Pleat, the structure is an extremely weak water conducting layer.

The crack height of the fissure zone is generally 500-1000 m. The fissures are mostly filled with calcium, siliceous, muddy and other materials. The rock layer has poor water permeability and is extremely weak in water. The fractured rock mass is broken and the engineering geological conditions are poor. The hydrogeological conditions in the mining area are simple.

Second, bad engineering geological factors

In the process of mining metal mines, there are widespread problems in engineering geology. The main discussion here is the impact of potential adverse engineering geological factors on deposit mining.

1. Roofing belt

The PD molybdenum ore area has large topographic cuts and gullies. The Quaternary covering layer is mainly composed of sub- clay and black cloud sloping granulite and crystallized tuff lava, granite residual slope; its distribution area is wide, the thickness is different, and the maximum thickness of the hole can reach tens of meters. . In the molybdenum mining project, the calculation of the roof collapse zone and the stability of the mining slope is very important. The theoretical and practical research results show that there are two kinds of motion forms, namely, bending and tensile failure and shear failure, after the overburden strata are developed and destroyed. The development process of the bending and pulling failure is: as the mining field advances, the overburden rock is bent under the action of gravity; after the bending settlement develops to a certain limit, the crack is formed at the end of the rock wall—the central crack forms a pseudoplastic rock beam. When the settlement value exceeds the allowable settlement value of the "pseudo-plastic rock beam", the suspended rock layer will fall by itself.

2, surface cracking, landslide

The structure is developed in the area, the rock is broken, the gravity erosion is active, and small landslides and small mudslides develop. After the development of the deposit, the state of the water environment in the mining area has been changed, and the re-infiltration of the surface or groundwater into the joint fissure surface in the area will inevitably lead to new engineering geological problems such as surface cracking or landslide.

3. Bad rock mass and rolling stone

The structure of the mining area is developed, the mountain is steep, the rock is bare, and the weathering is severe. In the PD section of the mining area, due to structural cutting, rock cracking, local rock collapse and collapse often occur. Especially after mining in the mining area, the artificial slopes and steep ridges are easy to form cracks and rolling stones after the rain; at the same time, the large ore and slag accumulated on the side of the working platform also have the possibility of loose rolling.

4, tailings, waste rock yard stability

The flash floods caused by seasonal climate change will cause a threat to the tailings and waste rock dumps, which will easily lead to artificial mudslides. The pit effluent should be properly treated during the mining of the deposit. It will pollute the surface water and groundwater after leaching by rainwater, and it will also induce secondary geological disasters.

3. Prevention measures and techniques for the harm of bad engineering geological factors

1. Prevention and control of the roof fall zone

Before mining, the hydrogeology, engineering geology and environmental geological survey of the mining area should be strengthened, relevant geological data should be collected, and shallow drilling projects such as engineering survey drills should be combined to maximize the understanding of the thickness of the sub-clay and residual slope in the area. The analysis of the physical and mechanical properties of the soil of the system provides a basis for the prevention and control of the roof caving zone.

2. Prevent landslides and mudslides

The mining area is a geological disaster-prone area, and environmental protection, tree planting, and water and soil conservation should be strengthened. When mining deposits, solid waste such as slag and waste rock in the area should be rationally planned to prevent unreasonable mining in the mining area and reduce human-induced geological disasters.

3, landslide and rolling stone prevention and management

Through surface survey and on-site investigation, according to the characteristics of the terrain and the distribution of engineering operations, the areas where landslides may occur are delineated, and the barriers, interception, prevention and pretreatment measures are adopted to eliminate hidden dangers. It is necessary to fully understand the possibility of mountain cliff cracking during large blasting or storms, and strengthen prevention and management. For extra large ore piled on the edge of the work platform, it is advisable to clean and strictly guard the pipe in time to prevent it from rolling.

4. Strengthen the management of tailings and waste rock dumps

For solid waste generated by mining activities, special sites should be used for stacking, and effective measures should be taken to prevent secondary environmental pollution and induce secondary geological disasters. According to the nature of mining solid waste and the engineering geological conditions of storage sites, comprehensive anti-seepage and drainage measures should be adopted to prevent leaching water from polluting surface water and groundwater. Covering measures such as planting plants or turf should be adopted for the dam surface and dam slope of the tailings reservoir to prevent dust, landslide and soil erosion. Promote the recovery technology of tailings re-election and associated minerals and valuable elements; use tailings processing to produce building materials and products, such as cement additives, tailings bricks, etc.; promote the use of tailings, waste rock as filling, filling Process technology for goaf or collapse.

Fourth, strictly prevent the deterioration of engineering geological conditions

Through engineering geological survey and analysis of deterioration factors, targeted technical measures are implemented to prevent geological disasters caused by deterioration of engineering geological conditions.

1, using drainage and drainage technology measures

According to the regional selection of corresponding drainage and drainage technology measures, in the highly weathered geological area, the robustness and effectiveness of the drainage project should be ensured to reduce the erosion and softening degree of the engineering rock mass to improve the shear strength of the engineering rock mass. And stability; for the cracking step body, it is advisable to adopt comprehensive drainage and drainage measures such as sparse, intercept, guide and row.

2. Reinforcement and reinforcement measures for slope rock mass

For slope areas with poor engineering geology, technical measures such as reinforcement and support and anti-collapse can be implemented, such as hanging net slope protection, grouting, retaining walls, anti-slide piles, anchors, etc., to increase rock mass strength and reduce engineering rock. The degree of damage caused by poor engineering geological factors caused by excavation.

V. Suggestions

1. Reasonable planning and sustainable development. In addition to the core area of ​​PD molybdenum ore, there are many small mines nearby, so reasonable planning should be carried out for mineral resources exploration, mining, protection and mine ecological environment protection. Plans for mining design, selection, safety, and environmental protection of mines should be carefully demonstrated and verified. Adhere to the standardization of mine production, sustainable development of mining and environmental protection.

2, to prevent the main, prevention and control. For mines, spoils, abandoned rocks, etc., which may cause landslides, collapses, mudslides, etc., appropriate measures should be taken to treat them as soon as possible.

3. Strengthen investigations and improve forecasting ability. Comprehensive understanding and prediction of the laws of geological disasters in the region will provide a basis for governance. In particular, it is necessary to pay attention to the destruction of vegetation during mining, causing soil erosion, surface deformation, formation of ground fissures, collapses, exposed pits, waste rock piles, etc., and it is easy to induce geological disasters such as landslides, collapses, mudslides, etc. Monitoring and forecasting of geological disasters that may be induced during the development process, setting up monitoring points for key geological disasters throughout the year, and adopting effective prevention and control measures to minimize the occurrence of sudden geological disasters.

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