Slope anti-skid treatment method for open-pit mining

Abstract

The invention discloses an open-pit mining side slope anti-skid treatment method, which belongs to the technical field of side slope treatment, and comprises the following steps: S1, probing main factors causing a landslide through hydrogeology, engineering geology and structural analysis in combination with an exploratory well mode; s2, removing the slippery mass or too loose rock-soil mass in the pre-slide from top to bottom, expanding the boundary of the stope, and enabling the slope angle of the renovation bench to be smaller than the internal friction angle of the rock mass at the position; s3, a pre-splitting blasting technology is adopted, the influence of blasting vibration is reduced, and the stability of slope rock mass is improved; s4, surface water is prevented and drained, and underground water is dredged; s5, carrying out comprehensive surface protection on easily-weathered and relatively-broken parts of the side slope rock; s6, a hole pile and well pile combined supporting and retaining project is arranged on the lower middle portion of the new sliding body and the lower middle portion of the old sliding body; s7, carrying out stability monitoring and evaluation after slope improvement; s8, restoring vegetation after treatment; after a series of treatment, the moving speed of the landslide is reduced, the rock mass at the upper part of the side slope can be in a relatively stable state, and a very good side slope treatment effect is achieved.

Description

Technical Field

[0001] The invention relates to the technical field of slope management, in particular to an open-pit mining slope anti-slip management method. Background Art

[0002] Open-pit mining of uranium is a common means of developing shallow hard rock uranium mines. However, with the increase in mining depth, open-pit mining is more difficult and more dangerous than other industries in mines with poor geological conditions. The safety of the slope is a prerequisite for ensuring the normal production operations of open-pit mines. Relevant personnel must do a good job of slope protection during work.

[0003] Most of the existing technologies use a single method for slope protection, which has relatively poor protection effects and cannot achieve better slope protection effects. Therefore, how to design an open-pit mining slope anti-slip treatment method to improve the slope protection effect is a technical problem that technical personnel in this field urgently need to solve. Summary of the invention

[0004] The purpose of the present invention is to provide an open-pit mining slope anti-slip treatment method to improve the slope protection effect in view of the defects and shortcomings in the prior art.

[0005] To achieve the above object, the technical solution adopted by the present invention is:

[0006] The present invention provides an open-pit mining slope anti-slip treatment method, which comprises the following contents:

[0007] S1. Exploring the main factors causing landslides through hydrogeological, engineering geological and structural analysis combined with exploration wells;

[0008] S2. Remove the loose rock and soil in the sliding body or pre-slide from top to bottom, expand the boundary of the stope, and make the slope angle of the regulation step smaller than the internal friction angle of the rock mass at that location;

[0009] S3. Use pre-splitting blasting technology to reduce the impact of blasting vibration and improve the stability of the slope rock mass;

[0010] S4. Prevent and drain surface water and divert groundwater;

[0011] S5. Comprehensively protect the easily weathered and broken parts of the slope rock;

[0012] S6. A support project combining bored piles and well piles is set up in the middle and lower parts of the new and old sliding bodies;

[0013] S7. Conduct stability monitoring and evaluation after slope improvement;

[0014] S8. Restore vegetation after treatment.

[0015] Preferably, in S2, a bulldozer is used to remove the overly loose rock and soil in the sliding body or pre-slide on the step with a working platform greater than 5 meters; an electric hammer is used to load the overly loose rock and soil in the sliding body or pre-slide on the step with a working platform less than 5 meters, and the soil and / or stone on the upper slope are pushed to the lower part, and the slope surface is manually trimmed and leveled.

[0016] Preferably, in S3, pre-splitting blastholes are drilled according to the designed slope angle, and the depth of the pre-splitting blastholes is 10m to 12m; if the resistance line of the pre-splitting hole exceeds 2m to 3m, a secondary main hole or a main blasthole is arranged; the pre-splitting hole is 8 to 12m ahead of the main blasthole; the pre-splitting hole is detonated ahead of the main blasthole, with an interval of not less than 50 milliseconds; and the pre-splitting hole adopts continuous charging.

[0017] Preferably, the method for preventing and draining surface water in S4 is: 15m to 30m outside the stope boundary, a main drainage ditch is built with paddle masonry blocks, and each step platform is built with mortar masonry blocks. The secondary drainage ditch is connected to the main drainage ditch to guide water into the main drainage ditch for drainage;

[0018] The method of diverting groundwater is as follows: drill inclined holes into the slope at intervals of 10m to 15m vertically at landslide and landslide-prone locations, drill 3 to 8 inclined holes horizontally for each gradient, and insert filter tubes into the inclined holes.

[0019] Preferably, the elevation angle of the inclined hole is 12° to 15°, the opening diameter is 90mm to 120mm, the final hole diameter is 60mm to 85mm, and a 2m or 2.5m filter tube is inserted into the final hole at a hole depth of (45±5)m.

[0020] Preferably, in S5, a small retaining wall is first set at the landslide corner, and then slope protection shotcrete is used in areas where the rocks are broken and weathered strongly, paddle block stone steps are used in fault fracture zones and areas prone to local collapse, and slope protection beams, paddle block stones and other slope protection measures are used in areas of local collapse.

[0021] Preferably, the S6 medium-hole pile is bored with a well drilling machine, a steel frame is lowered into the hole after the hole is completed, and then concrete is poured into the hole;

[0022] The sliding part of the pile is excavated manually, the bedrock below the sliding surface is blasted with gunpowder, and then a steel frame is lowered and poured with concrete.

[0023] Preferably, bored piles and well piles are arranged in the lower middle part of the sliding body, and a supporting project combining bored piles and well piles is arranged at intervals of 10m to 15m, wherein the interval distance between adjacent bored piles in a supporting project is 2.5m to 5m, the setting ratio of bored piles to well piles is 5 to 8:1, and the bored piles and the well piles are evenly arranged.

[0024] Preferably, in S7, an unbalanced thrust transfer method is used to analyze the stability of the slope;

[0025] The analysis results include four options: no treatment, only considering artificial anti-slip measures to reinforce the treatment, only considering setting up drainage holes to lower the water level below the sliding body, and considering combining artificial anti-slip measures with drainage holes.

[0026] Preferably, in S8, trees and grass are planted on the platform and the slope, wherein the row spacing and plant spacing between trees are both 1.5 m.

[0027] Compared with the prior art, the present invention has achieved the following technical effects:

[0028] The present invention firstly investigates the main factors causing the landslide, then removes the overly loose rock and soil in the sliding body or the pre-sliding body according to the factors causing the landslide, adopts the pre-splitting blasting technology to improve the stability of the rock mass of the slope, prevents and drains surface water, guides groundwater, protects the easily weathered parts of the slope, sets a retaining project combining bored piles and well piles in the middle and lower parts of the new and old sliding bodies, regularly monitors and evaluates the conditions after the slope is regulated, and restores vegetation planting. After these regulation measures, although the landslide still moves, the movement speed is very small, the average movement speed of the maximum displacement point is 1 mm / month, and the speed slows down; the bored pile stress value does not exceed the allowable stress, and the rock mass on the upper part of the slope is in a relatively stable state; it proves that the comprehensive measures taken are correct, the effect is good, and a good slope regulation effect can be achieved. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative labor.

[0030] Figure 1 A schematic diagram of the slope protection beam structure and position disclosed in a specific embodiment of the present invention;

[0031] Figure 2 A schematic diagram of the arrangement of crack monitoring points disclosed in a specific embodiment of the present invention;

[0032] Figure 3 A schematic diagram of displacement changes of crack monitoring points disclosed in a specific embodiment of the present invention;

[0033] Figure 4 A schematic diagram of displacement changes of each measuring point disclosed in a specific implementation manner of the present invention;

[0034] Figure 5 A schematic diagram of displacement monitoring of a new landslide disclosed in a specific embodiment of the present invention;

[0035] Figure 6 It is a schematic diagram of monitoring the rainfall and displacement of a new landslide disclosed in a specific implementation manner of the present invention. DETAILED DESCRIPTION

[0036] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0037] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the present invention is further described in detail below with reference to the accompanying drawings and specific embodiments.

[0038] The present invention provides an open-pit mining slope anti-slip treatment method, which comprises the following contents:

[0039] S1. Exploring the main factors causing landslides through hydrogeological, engineering geological and structural analysis combined with exploration wells;

[0040] S2. Remove the loose rock and soil in the sliding body or pre-slide from top to bottom, expand the boundary of the stope, and make the slope angle of the regulation step smaller than the internal friction angle of the rock mass at that location;

[0041] S3. Use pre-splitting blasting technology to improve the stability of the slope rock mass and reduce the impact of blasting vibration;

[0042] S4. Prevent and drain surface water and divert groundwater;

[0043] S5. Comprehensively protect the easily weathered and broken parts of the slope rock;

[0044] S6. A support project combining bored piles and well piles is set up in the middle and lower parts of the new and old sliding bodies;

[0045] S7. Conduct stability monitoring and evaluation after slope improvement;

[0046] S8. Restore vegetation after treatment.

[0047] Among them, the location of the exploration well in S1 is determined by geophysical exploration. By excavating the exploration well, it can be observed whether there is a sliding surface or a potential sliding surface. If there is a sliding trace, it is definitely a sliding surface. If there is a weak layer, it is a potential sliding surface, which provides a basis for the stability analysis of the slope and provides basic data for the depth or length of bored piles, well piles, and anchor rods. Moreover, through the exploration well, the original samples of the sliding surface or weak layer can be collected, the strength index of the sample can be measured, and the geological structure and engineering geological conditions of the exposed lower and upper final slopes of the mining area can be understood.

[0048] When there is loose rock and soil on the slope surface and the slope foot is large, which is larger than the internal friction angle of the rock and soil, the slope is cleared. In S2, a bulldozer is used to remove the loose rock and soil in the sliding body or pre-slide on the step with a working platform greater than 5 meters; an electric hammer is used to load the sliding body or the loose rock and soil in the pre-slide on the step with a working platform less than 5 meters, and the soil and / or stone on the upper slope are pushed to the lower part, and the slope surface is manually trimmed and flattened. If the structural layer that causes the slope to slide is low, if a large amount of stone is cleared at this time, the rock structure that causes the slide will still exist, and the slope stability will not be greatly improved. On the contrary, it is not conducive to the stability of the slope. At this time, only the loose rock and soil in the sliding body is removed, and the boundary of the stope is appropriately expanded.

[0049] For open-pit mines, blasting is an external force that often acts on the slope. The existing technology uses large blasting. Under the instantaneous impact of the blasting power, the joints and fissures in the slope rock mass open and spread, and tensile cracks parallel to the slope appear, which weaken the strength of the rock mass itself. The present invention uses pre-splitting blasting technology, which not only reduces the impact of blasting vibration, but also makes the slope surface flat, and the slope angle and boundary line are accurately controlled, forming in one time, and can achieve good results. Among them, in S3, pre-splitting holes (inclined holes) are drilled according to the designed slope angle, and the depth of the pre-splitting holes is 10m to 12m; if the resistance line of the pre-splitting hole exceeds 2m to 3m, a secondary main hole or a main gun hole is arranged; the pre-splitting hole is 8 to 12m ahead of the main gun hole; the pre-splitting hole is detonated ahead of the main gun hole, with an interval of not less than 50 milliseconds; and the pre-splitting hole adopts continuous charging, and the explosive used in the pre-splitting hole is ammonium nitrate explosive. The structure of ammonium nitrate explosive is that the powder roll is tied to the detonating wire and detonated in sections with differential electric detonators.

[0050] The method for preventing and draining surface water in S4 is as follows: 15m to 30m outside the mining site boundary, a main drainage ditch is built with paddle-laid block stones, and secondary drainage ditches are built with mortar-laid block stones on each terrace platform. The secondary drainage ditch is connected to the main drainage ditch to direct water into the main drainage ditch for drainage; concrete surface protection is used for the flat areas of the mining site with strong surface permeability, and concrete or mortar-laid block stone slope protection is sprayed on the slope surface of each terrace of the slope, so that all atmospheric precipitation in the slope can be drained away.

[0051] The method of diverting groundwater is: use a drilling rig to drill inclined holes into the slope at every 10m to 15m vertically at the landslide and landslide-prone locations, and drill 3 to 8 inclined holes horizontally for each gradient. The elevation angle of the inclined hole is 12° to 15°, the opening diameter is 90mm to 120mm, the final hole diameter is 60mm to 85mm, and a 2m or 2.5m filter pipe is inserted after the final hole at a depth of (45±5)m.

[0052] In S5, a small retaining wall is first set up at the landslide corner, and then the slope protection sprayed concrete is used in the areas with broken rocks and strong weathering. The paddle block stone step type is used in the fault fracture zone and the areas prone to local collapse. In the local collapse area, the slope protection and surface protection measures such as slope protection beams and paddle block stones are used. Among them, the height of the small retaining wall at the landslide corner is 2m to 3m; the proportion of slope protection sprayed concrete is cement: sand: slag (0.5cm to 2cm) = 0.8 to 1.2: 13 to 16: 1.5 to 3.5, the sand particle size is less than 15mm, and the thickness of the sprayed concrete is 100-150mm. The paddle block stone steps are built along the slope, with a step width and height of 550 to 650; the slope protection beam is parallel to the landslide from top to bottom, with a lateral spacing of 15m to 20m, a beam width of 400mm to 500mm, and a height of 600mm to 700mm. Both sides are reinforced with paddle block stones with a width of 400mm to 600mm and a height of 300mm to 400mm. Anchor rods are staggered at intervals of 300mm to 1000mm in the longitudinal length, and the anchor rods extend perpendicular to the slope protection beam into the landslide. The length of the anchor rods in the slope protection beam is 500mm to 600mm, and the length in the landslide is 800mm to 1100mm.

[0053] The S6 medium-hole pile is drilled with a well drilling machine, and after the hole is completed, a steel frame is lowered and concrete is poured into the hole;

[0054] The sliding part of the pile is excavated manually, the bedrock below the sliding surface is blasted with gunpowder, and then a steel frame is lowered and poured with concrete.

[0055] Bored piles and well piles are set in the middle and lower part of the sliding body, and a supporting project combining bored piles and well piles is set at intervals of 10m to 15m. Among them, the interval distance between adjacent bored piles in a supporting project is 2.5m to 5m, the setting ratio of bored piles to well piles is 5 to 8:1, and the bored piles and the well piles are evenly arranged.

[0056] The hole diameter of the pile is 300mm~600mm, the hole depth is 15m~30m, the depth of the pile body embedded in the bedrock is 1 / 2 of the pile length, and the cross section of the pile is 1.2~1.8×1.5~2.2m 2 , depth 20m ~ 25m. The concrete ratio is cement: sand: slag (0.5 ~ 2cm) = 0.8 ~ 1.2: 13 ~ 16: 1.5 ~ 3.5.

[0057] In S7, the unbalanced thrust transfer method is used to analyze the stability of the slope; the analysis results include four types: no treatment, only considering artificial anti-sliding measures to strengthen the slope, only considering setting up drainage holes to lower the water level below the sliding body, and considering combining artificial anti-sliding measures with drainage holes.

[0058] In S8, trees and grass were planted on the platform and slopes, with the row and plant spacing between trees being 1.5m.

[0059] Figure 1 (1) is the anchor bolt layout diagram, where 1 is the weak surface position; 2 is the anchor bolt, which penetrates 800mm to 1100mm into the landslide and 500mm to 600mm into the beam;

[0060] (2) is the reinforcement diagram of the slope protection beam, where 1 is the weak surface position, 2 is the anchor rod, and the bottom one is the anchor rod at the base, 3 to 5 anchor rods are set, and the anchor rod at section II penetrates 800mm to 1100mm into the slope protection beam; 3 is the reinforcement of the slope protection beam; below 4 is the bottom of the slope; 5 means 900mm to 1200mm deep into the base;

[0061] (3) is a schematic diagram of the cross-sectional structure at II, where 6 represents mortar-laid blocks.

[0062] Example:

[0063] The ore body of an open-pit uranium mine is located in a fractured structural zone. The mining area is a single-sided hillside open-pit, east-west oriented, 500 meters long and 400 meters wide. The slope height is 165 meters. The slope angle is 41 degrees. The step is 10 meters high and the platform is 2 meters wide. A cleaning platform is set every three steps, and the cleaning platform is 6 meters wide. The size of the mining area is 500 meters long and 400 meters wide from the surface, 100 meters long and 30 meters wide at the bottom.

[0064] 1. After analysis, the causes of landslides are: internally, there are weak interlayers, which are continuously distributed, the occurrence of the weak interlayers is consistent with the slope, and the inclination angle of the rock layer is smaller than the slope angle. At the same time, there are faults parallel to the slope direction (east-west direction) and small faults in the north-south direction. These faults constitute the cutting surface of the slope rock mass. The role of groundwater is an important factor leading to slope damage. According to observation and records, it has a great relationship with rainfall. There is a law of "heavy rain leads to heavy slippage, light rain leads to small slippage, and no rain leads to no slippage". Externally, due to open-pit mining and slope excavation, an air-facing surface is formed (referring to the boundary surface of free space when the rock and soil body slides, such as the slope surface of the slope, the side wall of the chamber, the riverbed surface downstream of the dam foundation, etc.). The initial stress state of the slope rock mass is redistributed, and stress is released. In addition, the direction of the designed slope is consistent with the direction of the rock layer and is inclined in the same direction. These are all factors that are not conducive to slope stability. The influence of blasting power. For open-pit slopes, blasting power is the most common and frequent factor affecting slope stability. Under the instantaneous impact of blasting power, the joints and cracks in the slope rock mass open and spread, and tensile cracks parallel to the slope direction appear, all of which weaken the strength of the rock mass itself.

[0065] 2. Remediation measures

[0066] According to the actual situation, measures including exploration, clearing, reduction, dredging, protection, storage and evaluation were adopted to regulate the slope, and vegetation restoration was carried out after regulation.

[0067] The weak sliding surface was determined mainly through hydrogeological, engineering geological and structural analysis, and finally combined with the investigation of 4 exploration wells on site.

[0068] Rock layers exposed on the open-pit slope: Quaternary slope accumulation layer, sub-clay with gravel, thickness less than 10m, exposed above 455m. Cambrian, shallow seashore marine sedimentary sandstone, slightly metamorphic, lithology is mica fine sandstone, siltstone, intercalated with slate and marl. According to its engineering geological characteristics, it is divided into the following three rock groups: 1) The first rock group: in the west of the slope (bounded by the F fault), it is gray-green, gray-white medium and thick layers of mica quartz fine sandstone, intercalated with black slate, hard, and undeveloped joints; 2) The second rock group: exposed to the east of the F fault, above the 435m elevation, with weathered marl as the bottom boundary. The lithology is interbedded with slate and siltstone, and slate is dominant upwards, with severe weathering, rock strength, and a severe weathering zone; 3) The third rock group: below the 435m elevation, it is medium and thick layers of mica quartz fine sandstone, intercalated with mudstone and marl. The 405m-435m bench section is yellow-green sandstone, and the rock is broken. The size of the weathered rock block is 0.3m-1.0m, which is a strong differentiation zone. Below 405m, the thickness of the fine sandstone increases, with a layer thickness of 0.5m-1.5m. The rock layer is relatively complete, slightly weathered, and the rock strength increases. Regional fault structures F2, F3-1, F3-2, and F. It is large in scale and runs through the entire lower slope of the mining area. Among them, F2 mainly controls the stability of the final slope of its upper plate. The slope rock mass often slides with F2 and its broken zone as the sliding surface. Exploration wells were set up for exploration at the 475m, 435m, 415m, and 395m elevation stages to finally determine the specific locations of the new and old sliding surfaces.

[0069] The clearing is carried out from top to bottom. A bulldozer is used on steps with a working platform greater than 5 meters. Electric hammers are used on steps with a platform less than 5 meters to push the soil (stone) on the upper slope to the lower part. Except for some large pieces that need to be blasted with small cannons, the slope surface is manually trimmed and leveled. The clearing situation of each step is shown in Table 1.

[0070] Table 1 Cleaning situation of each ladder section

[0071]

[0072] The pre-splitting blasting method is used to reduce the impact of blasting vibration. Pre-splitting holes (inclined holes) are drilled according to the designed slope angle, with a hole depth of 11.5 meters. If the resistance line of the pre-splitting hole exceeds 2.5 meters, it is necessary to arrange the secondary main control or main gun hole, and the pre-splitting hole is 10 meters ahead of the main gun hole. The pre-splitting hole is detonated ahead of the main gun hole. The interval is not less than 50 milliseconds. The pre-splitting hole adopts continuous charging and is detonated in sections with differential electric detonators.

[0073] For surface drainage, a main drainage ditch made of paddle block stone is built 15m to 30m outside the boundary of the mining area. Secondary drainage ditches are set up on each terrace platform. The secondary drainage ditches are connected to the main drainage ditch to guide water into the main drainage ditch for drainage, forming a complete drainage system. For underground drainage, XU-100 and AD-100 drilling rigs are used to drill inclined holes in the slope to drain groundwater. The elevation angle is 12 to 15 degrees, the opening diameter is 110mm, the final hole diameter is 75mm, and the hole depth is about 50 meters. A filter pipe of 2m or 2.5m is placed after the final hole. The inclined hole plays a role in local drainage. The inclined hole on the east side of the F fault produces water all year round, and the amount of water inflow increases significantly in the rainy season. The groundwater level in the slope drops by 1m to 3m. The inclined hole exposes the aquifer at 15m to 20m in the slope, forming a small-scale descending funnel, which reduces the amount of groundwater in the slope.

[0074] In terms of slope protection, a small retaining wall with a height of 2m to 3m is set at the slope corner, and then the following three forms of slope protection are adopted according to different situations. For areas with broken rocks and strong weathering, sprayed concrete is used for protection. The concrete ratio is cement: sand: crushed stone = 1:10:2.5. Particles larger than 20mm are removed by sieving. The thickness of the protection is 100mm to 150mm. For fault fracture zones and areas prone to local collapse, paddle block stone step-type protection is used. For areas with local collapse, slope protection beams and paddle block stone are used for slope protection, which can withstand a certain amount of sliding force.

[0075] The retaining works for the old landslide are located at the 455m step. The retaining works for the new landslide are located at the 425m and 415m steps. The pile characteristics are shown in Table 2.

[0076] Table 2 Characteristics of bored piles

[0077]

[0078] At the same time, four well piles were constructed in the 455-meter section to anchor the old sliding body. The net cross-section of the well is 1.5×2.4m 2 . Depth 21 meters. On Line 1 (close to the main axis of the new sliding body), three exploration wells were constructed. Section 1.6×1.9m 2 . Depth 20m~25m.

[0079] The vegetation restoration plan adopts indigenous species, and at the same time, the natural landscape of the open-pit mining ruins is coordinated with the rural village pattern, and the long-term stability of the open-pit mining slope is guaranteed. The specific implementation is to plant trees on the 325m~355m platform and slope, with a row and plant spacing of 1.5m, and 25,069 trees are planted. Considering that grass can grow quickly after covering with soil, it can play the role of protecting the slope as soon as possible, and the platform and slope can be sown with seeds to plant grass, with a total grass planting area of ​​56,405m 2 .

[0080] 3. Remediation results

[0081] Stability Analysis of High and Steep Slopes

[0082] (1) Stability analysis method

[0083] According to the on-site investigation, the slope is unstable due to broken line sliding. Therefore, the unbalanced thrust transfer method is used to analyze the stability of the slope. Since the sliding surface is known, the safety factor (k s ) is calculated as shown in formula (2-2-4-1).

[0084]

[0085] T i =G i sinθ i (3)

[0086]

[0087] U i =γ w h i l i (2-2-4-5)

[0088] Where Ks is the safety factor; Ri is the anti-sliding force of the i-th calculation strip (KN / m); Ti is the sliding force of the i-th calculation strip (KN / m); Gi is the deadweight of the i-th calculation strip (KN / m); U i The single width of the i-th calculation strip is subject to water buoyancy (KN / m); h i is the average water head height at the bottom of the i-th calculation line (m); is the internal friction angle of the sliding surface of the i-th calculation line, c is the transfer coefficient of the i-th calculation item to the i+1-th calculation item; i is the cohesion of the sliding surface of the i-th calculation line (kPa); l i is the length of the sliding surface of the i-th calculation strip (m); θ i The angle between the sliding surface of the i-th calculation line and the horizontal line. ∑f length is the single-width anti-sliding force of the support project (kN / m).

[0089] The open-pit mining slope has two sliding surfaces, old and new. In order to analyze its stability, the sliding surface of the open-pit mining slope is simplified. The original local sliding surface is a smooth curve and is simplified to a broken line. Figure 2 .

[0090] Taking into account the height of the slope is 145m, according to the classification of my country's building slopes it should be a first-level slope, and the safety factor of a first-level slope should be 1.35. The following analysis and evaluation are based on a safety factor of 1.35.

[0091] (2) Stability analysis of high and steep slopes

[0092] The sliding body of the old landslide is divided into 6 sliding blocks according to the broken line of the sliding surface for calculation, and the new landslide is calculated as 7 sliding bodies. The specific calculation parameters are shown in Tables 3 and 4.

[0093] Table 3 Related parameters of the old landslide

[0094]

[0095]

[0096] Table 4 Related parameters of the new landslide

[0097]

[0098] The stability and safety analysis of old and new landslides is conducted under the following four circumstances:

[0099] 1) No treatment;

[0100] 2) Only consider artificial anti-slip measures for reinforcement;

[0101] 3) Only consider setting up drainage holes to lower the water level below the sliding body;

[0102] 4) Consider combining artificial anti-slip measures with drainage holes.

[0103] The old landslide was reinforced with bored piles and well piles at an elevation of 455m. The calculated anti-sliding capacity of the bored piles per width was 384.6kN, and the anti-sliding capacity of the well piles per width was 160.4kN. The new landslide was reinforced with bored piles at elevations of 425m and 415m. The calculated anti-sliding capacity of the bored piles per width was 312.5kN and 357.1kN, respectively. Combining the relevant parameters in Tables 2 and 3, the safety factor k of the above four cases was calculated using formula (1). s , see Table 5 for details.

[0104] Table 5 Safety factors for four landslide situations

[0105]

[0106]

[0107] As can be seen from Table 5, when the new and old landslides are not treated or only adopt artificial anti-slip measures, their safety factors are less than 1.35, especially the new landslide has a lower safety factor. Only adopting anti-slip measures, the safety factors of the old and new landslides are only increased by 0.06 and 0.11 respectively. The drainage holes are set in the sliding body to reduce the groundwater level in the sliding body to below the sliding surface. The safety factors of the old and new landslides are greater than or equal to 1.35, which meets the requirements of the first-level slope. After setting the drainage holes and combining artificial anti-slip measures, the safety and stability of the new and old landslides are much higher than 1.35. It can be seen that the key to the stability of the slope here is the role of groundwater. Therefore, to ensure the safety and stability of the slope, it is necessary to ensure that the drainage of the drainage holes in the slope is effective for a long time.

[0108] (3) Stability monitoring and evaluation of high and steep slopes

[0109] In order to ensure the safety and stability of the open-pit high slope, monitoring points are set for cracks, new and old landslides, and displacement monitoring is carried out using theodolites and other means. Combined with the local rainy season, the main monitoring period is between July of the current year and June of the following year. Figure 3 .

[0110] The fracture displacement monitoring is mainly carried out between August and September. The displacement changes of each measuring point are shown in Figure 4 As shown in the figure, the horizontal displacement of monitoring point 1# occurred on August 10, and the horizontal displacement of the fissure remained basically unchanged until around the 28th. After that, it increased sharply from 3mm to 27mm around September 5th; the horizontal displacement changes of monitoring points 3# and 4# were the same as those of monitoring point 1#, and they all increased sharply after the 28th, but the increase values ​​were different; and the water displacement of monitoring point 2# was larger, starting from 50mm, and increased sharply to 710mm from August 28th to around mid-September. The different horizontal displacements of these monitoring points are mainly caused by the different distribution of the landslide. Monitoring point 2# is at the rear edge of the new landslide, so its displacement is large, which also shows that the landslide is a push-type landslide.

[0111] In order to find out the displacement change of the new landslide, three monitoring points 415C, 425C, and 435C were set up on the new landslide. The changes of horizontal displacement and vertical displacement of the three detections are shown in Figure 5 . From the figure, it can be seen that the horizontal and vertical displacements of the 415C and 425C measuring points changed dramatically around October 10 of the same year, while the displacement of the 435C point changed dramatically around October 6. Then until September 4 of the following year, the horizontal and vertical displacements did not change much. From the monitoring data, it can be seen that the horizontal displacements of the three points ranged from 2000mm to 3000mm, and the maximum vertical displacement was about 1000mm. It can be seen that the new landslide had very little sliding after October 10 of the same year, and basically did not slide. The main reason was that artificial anti-slip was carried out during this period.

[0112] In order to understand the relationship between water and sliding, the correlation between rainfall monitoring and new landslide sliding was monitored. Figure 6 As can be seen from the figure, the displacement of the landslide increases sharply from July to November in the rainy season, which is not synchronized with the rainfall. The main reason is that it takes time for the rain to infiltrate the groundwater. After the rock and soil on the slope absorb water, it softens and the strength index cohesion C and internal friction angle Ф also need time to decrease. After the start, there is little change until the rainy season of the following year. The main reasons are artificial reinforcement of the landslide and the setting of drainage holes in the slope and landslide body to drain the groundwater. In short, from the correlation between rainfall and sliding, it can be seen that rainwater is a very important factor affecting the stability of landslides.

[0113] After comprehensive treatment, the new and old landslides in the upper part of the slope (above 405m elevation) moved. But the movement speed was very small, with the average movement speed of the maximum displacement point being 1 mm / month (equivalent to 0.02 of the initial sliding stage), and the speed slowed down. The bored pile stress value did not exceed the allowable stress, and the rock mass in the upper part of the slope was in a relatively stable state. This proved that the comprehensive measures taken were correct and the effect was good.

[0114] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the claims of the present invention.

[0115] It should be noted that it is obvious to those skilled in the art that the present invention is not limited to the details of the above exemplary embodiments, and that the present invention can be implemented in other specific forms without departing from the spirit or essential features of the present invention. Therefore, no matter from which point of view, the embodiments should be regarded as exemplary and non-restrictive, and the scope of the present invention is defined by the appended claims rather than the above description, and it is intended that all changes falling within the meaning and scope of the equivalent elements of the claims are included in the present invention, and any figure mark in the claims should not be regarded as limiting the claims involved.

Claims

1. A method for preventing slippage of open-pit mining slopes, characterized in that: Includes the following: S1. Exploring the main factors causing landslides through hydrogeological, engineering geological and structural analysis combined with exploration wells; S2. Remove the loose rock and soil in the sliding body or pre-slide from top to bottom, expand the boundary of the stope, and make the slope angle of the regulation step smaller than the internal friction angle of the rock mass at that location; S3. Use pre-splitting blasting technology to reduce the impact of blasting vibration and improve the stability of the slope rock mass; S4. Prevent and drain surface water and divert groundwater; S5. Comprehensively protect the easily weathered and broken parts of the slope rock; S6. A support project combining bored piles and well piles is set up in the middle and lower parts of the new and old sliding bodies; S7. Conduct stability monitoring and evaluation after slope improvement; S8. Restore vegetation after treatment.

2. The method for preventing slippage of open-pit mining slopes according to claim 1 is characterized in that: In S2, a bulldozer is used to remove the loose rock and soil in the sliding body or pre-slide on the step with a working platform greater than 5 meters; an electric hammer is used to remove the loose rock and soil in the sliding body or pre-slide on the step with a working platform less than 5 meters, and the soil and / or stone on the upper slope are pushed to the lower part, and the slope surface is manually trimmed and leveled.

3. The method for preventing slippage of open-pit mining slopes according to claim 1 is characterized in that: In S3, pre-splitting holes are drilled according to the designed slope angle, and the depth of the pre-splitting holes is 10m to 12m. If the resistance line of the pre-splitting holes exceeds 2m to 3m, a secondary main hole or main gun hole is arranged; the pre-splitting holes are 8 to 12m ahead of the main gun holes; the pre-splitting holes are detonated ahead of the main gun holes, with an interval of not less than 50 milliseconds; and the pre-splitting holes are charged continuously.

4. The method for preventing slippage of open-pit mining slopes according to claim 1, characterized in that: The method of preventing and draining surface water in S4 is: 15m to 30m outside the stope boundary, a main drainage ditch is built with mortar-laid block stones, and secondary drainage ditches are built with mortar-laid block stones on each terrace platform. The secondary drainage ditch is connected to the main drainage ditch to guide water into the main drainage ditch for drainage; The method of diverting groundwater is as follows: drill inclined holes into the slope at intervals of 10m to 15m vertically at the landslide and landslide-prone locations, drill 3 to 8 inclined holes horizontally for each gradient, and insert filter tubes into the inclined holes.

5. The method for preventing slippage of open-pit mining slopes according to claim 4 is characterized in that: The elevation angle of the inclined hole is 12° to 15°, the opening diameter is 90mm to 120mm, the final hole diameter is 60mm to 85mm, and a 2m or 2.5m filter pipe is inserted into the final hole at a hole depth of (45±5)m.

6. The method for preventing slippage of open-pit mining slopes according to claim 1, characterized in that: In S5, a small retaining wall is first set up at the landslide corner, and then shotcrete is used for slope protection in areas with broken rocks and strong weathering. Paddle block stone steps are used in fault fracture zones and areas prone to local collapse. Slope protection beams, paddle block stones and other slope protection measures are used in areas of local collapse.

7. The method for preventing slippage of open-pit mining slopes according to claim 1, characterized in that: The S6 medium-hole pile is drilled with a well drilling machine, and after the hole is completed, a steel frame is lowered and concrete is poured into the hole; The sliding part of the pile is excavated manually, the bedrock below the sliding surface is blasted with gunpowder, and then a steel frame is lowered and poured with concrete.

8. The method for preventing slippage of open-pit mining slopes according to claim 7, characterized in that: Bored piles and well piles are set in the middle and lower part of the sliding body, and a supporting project combining bored piles and well piles is set at intervals of 10m to 15m. Among them, the interval distance between adjacent bored piles in a supporting project is 2.5m to 5m, the setting ratio of bored piles to well piles is 5 to 8:1, and the bored piles and the well piles are evenly arranged.

9. The method for preventing slippage of open-pit mining slopes according to claim 1, characterized in that: In S7, the unbalanced thrust transfer method is used to analyze the stability of the slope; The analysis results include four options: no treatment, only considering artificial anti-slip measures to reinforce the treatment, only considering setting up drainage holes to lower the water level below the sliding body, and considering combining artificial anti-slip measures with drainage holes.

10. The method for preventing slippage of open-pit mining slopes according to claim 1, characterized in that: In S8, trees and grass were planted on the platform and slopes, with the row and plant spacing between trees being 1.5m.

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