A method for constructing deep underground spaces in open-pit mine spoil heaps

Abstract

This invention discloses a method for constructing a deep underground space in an open-pit mine spoil heap. When the spoil heap reaches the construction level of the underground space, a waterproof structural layer is constructed, and then the underground space is built on top of it. Further waterproof structural layers are then constructed around the underground space. After the waterproof structural layers are completed, spoil heap continues to be filled. During the filling process, a load-reducing device layer and a load-reducing reinforcement structure layer are alternately installed from bottom to top above the underground space. The load-reducing device layer consists of multiple load-reducing devices, and a load-reducing reinforcement structure is located on each side above the load-reducing devices along their length. These load-reducing reinforcement structures are arranged to form a load-reducing reinforcement structure layer. After the uppermost load-reducing reinforcement structure layer is installed, spoil heap continues to the elevation of the spoil heap. This invention uses load-reducing devices, arranged in layers and stages above the underground space, to perform secondary unloading of the load above the underground space, fully utilizing the load-reducing effect under deep burial conditions.

Description

Technical Field

[0001] This invention relates to a method for constructing underground space, specifically a method for constructing a deep underground space in an open-pit mine spoil heap. Background Technology

[0002] Open-pit mine spoil heaps are characterized by their great depth and wide area. Constructing deep-buried spaces within them allows for secondary use of the space without occupying excess land, offering significant safety protection value and cost advantages. However, this area is still in the preliminary research stage, with no engineering cases or targeted load-reducing materials and construction techniques available. Issues such as waterproofing and the enormous load pressure above the space have become major bottlenecks restricting the construction of this project.

[0003] In traditional highway and railway engineering, EPS (expanded polystyrene) boards are generally used as load-reducing materials, laid on top of culverts to reduce load. The basic principle is that EPS boards have relatively low stiffness. After being laid on top of the culvert, when excavated soil is dumped, the settlement of the soil column (the rectangular section of soil directly above the culvert) is greater than the settlement of the soil on both sides. This results in an upward frictional force between the soil on both sides and the soil column, thus reducing the pressure on the culvert top to less than the soil column's own weight, thereby achieving the load-reducing effect of the EPS board. Conversely, without EPS boards, i.e., without load-reducing measures, the settlement of the soil column is less than that of the soil on both sides, resulting in a downward frictional force between the soil on both sides and the soil column, thus increasing the pressure on the culvert top to greater than the soil column's own weight. When this solution is applied to the construction of deep underground spaces in open-pit mines, it faces the following problems: First, EPS boards are non-degradable plastics, and large-scale application may lead to serious environmental and ecological problems; second, existing research indicates that EPS boards can only play a load-reducing role within a burial depth of no more than 60m, and the load-reducing effect no longer increases after the EPS board thickness exceeds 80cm, while the deep underground spaces of spoil heaps in open-pit mines are generally no less than 200m deep, limiting the pressure unloading limit; third, a single-layer arrangement of load-reducing devices has limited load-reducing effect. Therefore, EPS boards cannot yet be used as load-reducing materials for deep underground spaces in spoil heaps of open-pit mines.

[0004] Based on this, the present invention proposes a method for constructing a deep underground space in an open-pit mine spoil heap, which specifically addresses the above-mentioned problems. Summary of the Invention

[0005] To address the problems existing in the prior art, this invention provides a method for constructing deep underground spaces in open-pit mine spoil heaps, solving the problem of excessive overburden loads that restrict the development of underground space construction.

[0006] To achieve the above objectives, the present invention provides the following technical solution: a method for constructing a deep underground space in an open-pit mine spoil heap, comprising the following steps: When dumping waste from an open-pit mine into the underground space construction layer, a waterproof structural layer is first constructed, and then the underground space is constructed on top of it. After the underground space is completed, waterproof structural layers are then constructed on the left and right side walls and the top wall along the length of the underground space. After the waterproof structural layer is completed, the internal spoil disposal site continues to dump soil. During the soil dumping process, a load-reducing device layer and a load-reducing reinforcement structural layer are alternately installed from bottom to top above the underground space. The load reduction device layer is composed of multiple load reduction devices arranged together. On both sides of the load reduction device in the same layer, there is a load reduction reinforcement structure. The load reduction reinforcement structures in the same layer are arranged to form a load reduction reinforcement structure layer. After setting the top layer of load-reducing and strengthening structure, continue dumping soil to the elevation of the inner dump site.

[0007] Furthermore, the load reduction device is a cuboid box structure with multiple circular through slots of two different diameters arranged symmetrically along its length, namely large through slots and small through slots. Multiple horizontal ribs are arranged at intervals above and below the circular through slots, and vertical ribs are arranged between adjacent circular through slots. The angle between the vertical ribs and the horizontal ribs is 90 degrees.

[0008] Furthermore, the unloading displacement that can be generated after the unloading device is damaged is : ; In the formula: h is the cross-sectional height of the load reduction device, d is the width of the load reduction device, R is the radius of the large through slot, r is the radius of the small through slot, N is the number of large through slots, n is the number of small through slots, and η is the solid material fragmentation rate of the load reduction device.

[0009] Furthermore, the load-reducing device is positioned directly above the underground space. The length and width of the load-reducing device correspond to the width and length of the underground space, respectively. The length of the load-reducing device is equal to the width of the underground space, and multiple load-reducing devices are arranged side by side in the width direction to cover the entire length of the underground space.

[0010] Furthermore, the first load-reducing device layer is directly set above the waterproof structure layer. Soil is discharged in the space at the same height as the first load-reducing device layer. The two sides along the length of the first load-reducing device layer are the load-reducing lines. The load-reducing range extends 10-30m to each side of the load-reducing lines as the center. Load-reducing reinforcement structures are set in the load-reducing range on both sides. Soil is discharged in the space between and outside the load-reducing reinforcement structures at the same height as the load-reducing reinforcement structures. Then, the second load-reducing device layer and the second load-reducing reinforcement structure layer are set in the same way as above, and so on, until the last load-reducing reinforcement structure layer is set. Soil is then discharged on top of it to the elevation of the inner spoil heap.

[0011] Furthermore, the waterproof structural layer includes an inner core and an outer layer. The inner core is wrapped inside the outer layer. The inner core is composed of clay-like material that is easily cemented when exposed to water or has strong density after compaction, and has a thickness of 3-5m. The outer layer is a waterproof cloth reinforced with steel wire.

[0012] Furthermore, the unloading device is made of fly ash, activated coal gangue, crushed coal gangue, a small amount of cement and water.

[0013] Furthermore, the load-reducing and strengthening structure is made by flattening and compacting granite or basalt fragments from open-pit mine overburden.

[0014] Compared with the prior art, the present invention has the following advantages: Using locally sourced solid waste materials from the mine, a new type of load-reducing device is constructed, effectively avoiding potential construction pollution to the internal spoil heap caused by existing engineering materials. Arranged in layers and stages above the underground space, the device allows for layered unloading and displacement, fully leveraging its load-reducing effect even at great depths, thus achieving the goal of reducing the overburden load on the deep underground space of the open-pit mine spoil heap.

[0015] By utilizing existing materials in the mining area to construct a waterproof structural layer, the dryness of the underground space can be effectively guaranteed.

[0016] The design incorporates a load-reducing and strengthening structure to perform secondary unloading of the load above the underground space. The construction process is simple and the load-reducing effect is good.

[0017] The construction process of this invention is closely integrated with the construction of the open-pit mine spoil heap, and is promoted in a coordinated manner. It does not affect the normal spoil heap construction in the mining area, nor does it affect the capacity of the spoil heap. At the same time, it makes full use of the internal space of the spoil heap, thus saving land resources. Attached Figure Description

[0018] Figure 1 This is a cross-sectional view of the internal spoil disposal site and underground space of this invention; Figure 2 This is a side view of the load reduction device of the present invention; Figure 3 This is a top view of the load reduction device of the present invention; In the diagram: 1-Underground space; 2-Load reduction device; 2.1-First load reduction device layer; 2.2-Second load reduction device layer; 2.3-Third load reduction device layer; 3-Load reduction reinforcement structure; 4-Waterproof structural layer; 5-Internal spoil heap; 6-Large channel; 7-Small channel; 8-Vertical reinforcement; 9-Horizontal reinforcement. Detailed Implementation

[0019] The invention will now be further described with reference to the accompanying drawings.

[0020] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0021] like Figures 1 to 3 As shown, the present invention provides a technical solution, comprising the following steps: When disposing of waste from open-pit mine dump 5 into underground space 1, a waterproof structural layer 4 is constructed first, followed by the construction of underground space 1 on top of the waterproof structural layer 4. After underground space 1 is completed, waterproof structural layers 4 are then constructed on the left and right side walls and the top wall along the length of underground space 1. The waterproof structural layer 4 consists of an inner core and an outer layer, with the inner core encased within the outer layer. The inner core is composed of clay-like materials from the open-pit mine strippings that are easily cemented by water or have high density after compaction, with a thickness of 3-5m. The larger value is used in areas with abundant groundwater, and in areas with particularly abundant groundwater, the thickness of the waterproof layer can be doubled. During construction, if easily cemented materials are used, pre-watering is required after laying to allow the materials to cement in advance, achieving waterproofing while reducing subsequent deformation. If highly dense materials are used, compaction is required, serving the same purpose. The outer layer is a waterproof fabric reinforced with steel wire, serving two purposes: shaping to prevent the inner core from being lost and reinforcing waterproofing.

[0022] After the waterproof structural layer 4 is completed, the inner spoil disposal site 5 continues to dump soil. During the soil dumping process, a load-reducing device layer and a load-reducing reinforcement structural layer are alternately installed from bottom to top above the underground space 1. The load-reducing device layer is composed of multiple load-reducing devices 2.

[0023] The load reduction device 2 is a rectangular box structure, which is integrally cast from fly ash, activated coal gangue, coal gangue crushed stone, a small amount of cement and water. After curing, it is transported to the installation site as needed.

[0024] like Figure 2 and Figure 3 As shown, the load reduction device 2 has multiple circular through slots of two different diameters arranged symmetrically along its length, namely large through slot 6 and small through slot 7. Multiple horizontal ribs 9 are arranged at intervals above and below the circular through slots, and vertical ribs 8 are arranged between adjacent circular through slots. The angle between the vertical ribs 8 and the horizontal ribs 9 is 90 degrees. The materials of the vertical ribs 8 and the horizontal ribs 9 are strip bamboo or steel bars.

[0025] The function of symmetrically spaced circular channels with two different apertures is to achieve the following: when the load-reducing device 2 is subjected to the load of the inner spoil disposal site 5 at a height of H1, the large channel 6 will fail first and undergo partial settlement. When the inner spoil disposal site 5 continues to increase the disposal height to H2 (H2≥1.5H1), the small channel 7 will fail next and continue to settle. This achieves the step-by-step failure, step-by-step settlement, and step-by-step load-reducing effect of one load-reducing device 2, preventing the channels from failing simultaneously and generating dynamic loads or impact loads, which would lead to dynamic load failure of the tunnel.

[0026] A mechanical model was established using mechanical simulation software. By repeatedly adjusting the apertures of the large channel 6 and the small channel 7, as well as the reinforcement structure of the vertical and horizontal ribs 8 and 9, the ultimate load at which the channel fails was finally simulated, which are also the ultimate heights H1 and H2 of the inner spoil heap 5. The apertures of the large channel 6 and the small channel 7 determine the unloading displacement when the load reduction device 2 is completely destroyed, directly controlling the load reduction effect; while the reinforcement structure mainly maintains the integrity of the load reduction device 2, ensuring that the structure is not damaged during hoisting.

[0027] The unloading displacement that can be generated after the unloading device 2 is damaged is : ; In the formula: h is the cross-sectional height of the load reduction device 2, d is the width of the load reduction device 2, R is the radius of the large through slot 6, r is the radius of the small through slot 7, N is the number of large through slots 6, n is the number of small through slots 7, and η is the solid material fragmentation rate of the load reduction device 2.

[0028] The specific steps for alternately setting load-reducing device layers and load-reducing reinforcement structure layers from bottom to top above underground space 1 during the soil removal process are as follows: Figure 1 As shown, taking the setting of a three-layer load reduction device layer and a load reduction reinforcement structure layer as an example, the illustration mainly aims to clearly show the positional relationship of each part, but fails to truly reflect the actual proportion of each part.

[0029] The first load-reducing device layer 2.1 is directly set above the waterproof structure layer 4. The load-reducing device 2 is located directly above the underground space 1. The length and width of the load-reducing device 2 correspond to the width and length of the underground space 1, respectively. The length of the load-reducing device 2 is equal to the width of the underground space 1. Multiple load-reducing devices 2 are arranged side by side in the width direction to cover the entire length of the underground space 1. After the first load-reducing device layer 2.1 is laid, soil continues to be discharged in the space at the same height as the first load-reducing device layer 2.1. The frictional force generated by the relative displacement between the rectangular cross-section soil directly above the first load-reducing device layer 2.1 and the soil on both sides is an important source of load-reducing capacity. Therefore, this contact surface is designed with precision. That is, the two sides along the length of the first load-reducing device layer 2.1 are taken as the load-reducing line, and the range extending 10-30m to both sides of the load-reducing line is taken as the load-reducing range. The greater the burial depth of the underground space 1, the larger the value of the load-reducing range. Load-reducing reinforcement structures 3 are set in the load-reducing range on both sides to improve the regional friction. The load-reducing reinforcement structure 3 is made of high-hardness and high-roughness stripping material from open-pit mines, such as granite or basalt fragments, which are laid flat and compacted. Soil is continuously discharged in the space between and outside the load-reducing reinforcement structures 3 on both sides at the same height as the load-reducing reinforcement structure 3. All load-reducing reinforcement structures 3 in this layer are arranged to form a load-reducing reinforcement structure layer. Then, the second load-reducing device layer 2.2 and the second load-reducing reinforcement structure layer are set up in the same way as above, until the third load-reducing device layer 2.3 and the third load-reducing reinforcement structure layer are set up. Soil is then discharged on top of these layers up to the elevation of the inner spoil heap 5. Simultaneously with the construction of the underground space, the passage connecting the surface and underground spaces is also constructed.

[0030] When setting up load-reducing device layers and load-reducing reinforcement structure layers layer by layer, the requirements are as follows: when the soil is discharged to the height of the second load-reducing device layer 2.2, the large channel 6 of the load-reducing device 2 in the first load-reducing device layer 2.1 is damaged, while the small channel 7 remains intact; when the soil is discharged to the height of the third load-reducing device layer 2.3, the small channel 7 of the load-reducing device 2 in the first load-reducing device layer 2.1 is damaged, while the second load-reducing device layer 2.2 remains intact. During the continued increase in height of the inner spoil heap 5, the large channel 6 and small channel 7 of the load-reducing device 2 in the second, third, and finally topmost load-reducing device layers are successively damaged. By adjusting the design ultimate load of the load-reducing device 2, the engineering nodes of structural failure can be adjusted.

[0031] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from its spirit or essential characteristics. Therefore, the embodiments should be considered in all respects as exemplary and non-limiting, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, all variations falling within the meaning and scope of equivalents of the claims are intended to be included within the present invention. No reference numerals in the claims should be construed as limiting the scope of the claims.

[0032] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any minor modifications, equivalent substitutions, and improvements made to the above embodiments based on the technical essence of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for constructing a deep underground space in an open-pit mine spoil heap, characterized in that, Includes the following steps: Step S1: When dumping the spoil from the open-pit mine (5) to the underground space (1) construction layer, first construct a waterproof structural layer (4), and then construct the underground space (1) on top of it. After the underground space (1) is constructed, continue to construct waterproof structural layers (4) on the left and right side walls and the upper wall of the underground space (1) along its length. Step S2: After the waterproof structural layer (4) is completed, the inner spoil heap (5) continues to dump soil. During the dumping process, the load reduction device layer and the load reduction reinforcement structural layer are alternately set from bottom to top above the underground space (1). The load reduction device layer is composed of multiple load reduction devices (2) arranged together. A load reduction reinforcement structure (3) is provided on both sides above the load reduction device (2) in the same layer along the length direction. The load reduction reinforcement structures (3) in the same layer are arranged to form a load reduction reinforcement structure layer. Step S3: After setting the top load-reducing and strengthening structural layer, continue to discharge soil to the inner spoil heap (5) elevation; The load reduction device (2) is a rectangular box structure. Along the length direction, multiple circular channels with two different apertures are symmetrically arranged at intervals, namely large channel (6) and small channel (7). Multiple horizontal ribs (9) are arranged at intervals above and below the circular channels. Vertical ribs (8) are arranged between adjacent circular channels. The angle between the vertical ribs (8) and the horizontal ribs (9) is 90 degrees. The load reduction device (2) is made of fly ash, activated coal gangue, coal gangue crushed stone, cement and water. The load reduction strengthening structure (3) is made of granite or basalt crushed material from open-pit mines, which is laid flat and compacted.

2. The method for constructing a deep underground space in an open-pit mine spoil heap according to claim 1, characterized in that, The unloading displacement that can be generated after the unloading device (2) is destroyed is : ； In the formula: h is the cross-sectional height of the load reduction device (2), d is the width of the load reduction device (2), R is the radius of the large through groove (6), r is the radius of the small through groove (7), N is the number of large through grooves (6), n is the number of small through grooves (7), and η is the solid material fragmentation rate of the load reduction device (2).

3. The method for constructing a deep underground space in an open-pit mine spoil heap according to claim 1, characterized in that, The load reduction device (2) is set directly above the underground space (1). The length and width of the load reduction device (2) correspond to the width and length of the underground space (1), respectively. The length of the load reduction device (2) is equal to the width of the underground space (1). Multiple load reduction devices (2) are arranged side by side in the width direction to cover the entire length of the underground space (1).

4. The method for constructing a deep underground space in an open-pit mine spoil heap according to claim 3, characterized in that, The first load reduction device layer (2.1) is directly set above the waterproof structure layer (4). Soil is discharged in the space at the same height as the first load reduction device layer (2.1). The two sides of the length direction of the first load reduction device layer (2.1) are the load reduction line. The range extending 10-30m to both sides of the load reduction line is the load reduction range. Load reduction reinforcement structures (3) are set in the load reduction range on both sides. Soil is discharged in the space between and outside the load reduction reinforcement structures (3) at the same height as the load reduction reinforcement structures (3). Then, the second load reduction device layer (2.2) and the second load reduction reinforcement structure layer are set in the same way as above, and so on, until the last load reduction reinforcement structure layer is set. Soil is discharged on it to the elevation of the inner dumping site (5).

5. The method for constructing a deep underground space in an open-pit mine spoil heap according to claim 1, characterized in that, The waterproof structural layer (4) includes an inner core and an outer layer. The inner core is wrapped inside the outer layer. The inner core is composed of clay material that is cemented by water or compacted after being exposed to open-pit mine strippings, with a thickness of 3-5m. The outer layer is a waterproof cloth reinforced with steel wire.

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