Construction method of fan foundation pit for desert region and fan foundation pit

Abstract

The embodiment of the invention provides a construction method of a draught fan foundation pit for a desert area and the draught fan foundation pit. The method comprises the steps that a foundation site is downwards excavated by a certain depth according to the designed gradient to form the foundation pit; driving-in type steel pipe soil nails are nailed into the slope surface; a certain distance is formed between the slope surface and the mesh surface ribs, and the mesh surface ribs are welded to the portions, exposed out of the stratum, of the driving-in type steel pipe soil nails; concrete is sprayed to the soil slope on which the net surface ribs are laid, so that the net surface ribs and the parts, exposed out of the stratum, of the driving-in type steel pipe soil nails are wrapped by the concrete, and a supporting structure is formed; and under the condition that it is determined that the strength of the supporting structure meets the design requirement, a certain depth is further excavated downwards on the basis of the current foundation pit, and the step that the driving-in type steel pipe soil nails are nailed into the slope formed through excavation at the design angle according to the first design distance is executed again till the depth of the foundation pit reaches the design depth. According to the embodiment of the invention, the stability of the foundation pit slope of the fan foundation can be improved.

Description

Technical Field

[0001] This application relates to the field of building construction technology, and in particular to a construction method and a wind turbine foundation pit for use in desert areas. Background Technology

[0002] As a renewable and pollution-free green energy generation method, wind power generation has a promising future with large-scale, high-proportion and multi-energy complementarity. In recent years, as the wind power industry has set its sights on the new goal of high-quality development and focused on promoting the construction of large bases in the "Three Norths" region, wind power projects have gradually expanded to desert and marginal areas.

[0003] Traditionally, wind turbine foundations are constructed using slope excavation. However, this method generally suffers from low overall stability. Therefore, improving the foundation pit construction method has become a crucial technical challenge for wind power projects in desert regions. Summary of the Invention

[0004] The purpose of this application is to provide a construction method and a foundation pit for wind turbine foundations in desert areas, so as to improve the stability of the slope of the foundation pit. The specific technical solution is as follows: In a first aspect, embodiments of this application provide a construction method for wind turbine foundation pits in desert areas, including: Within the selected foundation site, a foundation pit is excavated to a certain depth according to the designed slope. Driven steel pipe soil nails are driven into the excavated slope at a designed angle, with a portion of the nails fixed within the soil layer and the other portion exposed. Along the excavated slope, a mesh reinforcement is laid at a certain interval between the mesh reinforcement and the exposed portion of the driven steel pipe soil nails. Shotcrete is applied to the slope after the mesh reinforcement is laid, covering the exposed portion of the mesh reinforcement and the driven steel pipe soil nails to form a support structure. This support structure includes driven steel pipe soil nails, the mesh reinforcement, and a concrete surface layer formed during the shotcrete process. Once the strength of the formed support structure meets the design requirements, the foundation pit is further excavated to a certain depth, and the process of driving driven steel pipe soil nails into the excavated slope at a designed angle according to the first designed interval is repeated until the foundation pit depth reaches the designed depth.

[0005] Optionally, after driving driven steel pipe soil nails into the slope formed by excavation at the designed angle, and before laying the mesh reinforcement with a certain spacing between it and the slope, the construction method of the wind turbine foundation pit further includes: driving positioning bars into the slope formed by excavation according to the second designed spacing, so that part of the positioning bars is fixed in the stratum and the other part is exposed outside the stratum; the aforementioned laying of mesh reinforcement with a certain spacing between it and the slope formed by excavation includes: laying mesh reinforcement along the slope formed by excavation and welding the mesh reinforcement to the end of the positioning bar exposed outside the stratum, so that the mesh reinforcement forms a certain spacing between it and the slope under the support of the positioning bar.

[0006] Optionally, for the slope formed during the first downward excavation, the aforementioned laying of a mesh reinforcement with a certain spacing between it and the slope formed by the excavation includes: laying the mesh reinforcement along the slope formed by the excavation, such that a portion of the mesh reinforcement extends along the slope and forms a certain spacing between it and the slope, and another portion extends to the outer side of the slope top; welding the portion of the mesh reinforcement extending along the slope to the portion of the driven steel pipe soil nail exposed outside the stratum, and welding the portion of the mesh reinforcement extending to the outer side of the slope top to a ground anchor pre-installed on the outer side of the slope top.

[0007] Optionally, after laying the mesh reinforcement with a certain spacing between it and the slope formed by the excavation, and before spraying concrete onto the soil slope after laying the mesh reinforcement, the construction method of the wind turbine foundation pit further includes: on the side opposite to the foundation site in the part of the mesh reinforcement extending to the outer side of the slope top, setting a locking bar that abuts against the ground anchor and is located on the side of the ground anchor away from the foundation pit, and welding the locking bar to the mesh reinforcement and the ground anchor.

[0008] Optionally, the driven steel pipe soil nail is fixed in the stratum with one end in a closed cone shape and the other end exposed outside the stratum has an opening; the side wall of the driven steel pipe soil nail is provided with grouting holes arranged at the third design interval, and multiple angle steel barbs are respectively set outside each grouting hole; after the driven steel pipe soil nail is driven into the slope formed by excavation at the design angle, the construction method of the wind turbine foundation pit also includes: grouting into the driven steel pipe soil nail along the opening of the driven steel pipe soil nail.

[0009] Optionally, before spraying concrete onto the slope after the mesh reinforcement is laid, the construction method for the wind turbine foundation pit further includes: inserting drainage pipes spaced apart from each other into the slope, such that the first end of the drainage pipe is inserted into the stratum and the second end is exposed outside the stratum; the aforementioned spraying concrete onto the slope after the mesh reinforcement is laid includes: spraying concrete onto the slope after the mesh reinforcement is laid, avoiding the inserted drainage pipes, such that the second end of the mesh reinforcement is exposed outside the concrete surface layer formed by the spraying process, forming drainage holes; after excavating to the design depth of the foundation pit, the construction method for the wind turbine foundation pit further includes: setting up a ring-shaped drainage ditch at the bottom of the foundation pit with a certain distance between it and the toe of the slope; setting up at least one sump connected to the ring-shaped drainage ditch.

[0010] Optionally, before excavating a certain depth according to the design slope to form a foundation pit within the selected foundation site, the construction method of the wind turbine foundation pit may also include: setting up an annular water-retaining platform extending along the excavation edge line and having a certain distance between it and the excavation edge line on the outer side of the excavation edge line on the foundation site; and forming a drainage slope on the outer side of the annular water-retaining platform.

[0011] Optionally, the first design spacing includes vertical spacing and horizontal spacing; during construction, the depth of the unsupported portion of the foundation pit excavated downwards does not exceed the vertical spacing.

[0012] Optionally, the design slope is 1:0.75.

[0013] Secondly, this application provides a wind turbine foundation pit for use in desert areas, which is constructed using the wind turbine foundation pit construction method described in the first aspect.

[0014] Beneficial effects of the embodiments in this application: The construction method and the wind turbine foundation pit provided in this application for use in desert areas employ a composite support system of "driven-in steel pipe soil nails + mesh reinforcement + shotcrete" to protect the slope. The driven-in steel pipe soil nails provide active pull-out resistance, preventing overall slope instability; the mesh reinforcement enhances the integrity of the concrete surface layer, preventing localized spalling; the concrete surface layer seals the slope, isolating it from rainwater erosion, and together with the mesh reinforcement, forms a flexible support shell that transfers soil pressure to the driven-in steel pipe soil nails, avoiding localized stress concentration. Therefore, this composite support system, based on its synergistic effect in structure and stress distribution, can effectively improve the stability of the foundation pit slope.

[0015] Furthermore, the effective protection provided by the aforementioned support structure for the stability of the foundation pit slope allows for the appropriate steepening of the excavation slope while avoiding adverse effects on the stability of the foundation pit during actual construction. This creates the preconditions for steepening the excavation slope to save land area occupied by the foundation pit, thereby reducing the amount of earthwork excavation and backfilling, reducing transportation, waste soil, and backfilling costs, and shortening the construction period to minimize disturbance to the surrounding environment.

[0016] Of course, implementing any product or method of this application does not necessarily require achieving all of the advantages described above at the same time. Attached Figure Description

[0017] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other embodiments can be obtained based on these drawings.

[0018] Figure 1 A schematic flowchart illustrating a construction method for a wind turbine foundation pit provided in an embodiment of this application; Figure 2 A cross-sectional view of a wind turbine foundation pit provided in an embodiment of this application; Figure 3 This is a schematic diagram illustrating the connection between the driven steel pipe soil nail, the positioning bar, and the mesh reinforcement provided in an embodiment of this application. Figure 4 A schematic diagram illustrating the connection between driven steel pipe soil nails, mesh reinforcement, stiffeners, and equal-sided angle steel provided in the embodiments of this application; Figure 5 A schematic diagram illustrating the connection between the soil nailing wall and the landform on the outer side of the slope top, as provided in the embodiments of this application; Figure 6 A schematic diagram of a driven steel pipe soil nail provided in an embodiment of this application; Figure 7 A cross-sectional view of the grouting hole for a driven steel pipe soil nail provided in an embodiment of this application; Figure 8 A plan view of the annular water-retaining platform at the top of the wind turbine foundation pit provided in this embodiment of the application; Figure 9 This is another schematic diagram of the construction method for the wind turbine foundation pit provided in the embodiments of this application.

[0019] Figure label: 1-Driven steel pipe soil nail, 2-Mesh reinforcement, 3-Concrete surface layer, 4-Positioning reinforcement, 5-Strengthening reinforcement, 6-Equal angle steel, 7-Ground anchor, 8-Locking reinforcement, 9-Drainage hole, 10-Annular drainage ditch, 11-Sump well, 12-Annular water retaining platform; 101-Grouting hole, 102-Angle steel barbs. Detailed Implementation

[0020] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art based on this application are within the scope of protection of this application.

[0021] In traditional construction methods, the slope excavation method is generally used to build the foundation pit for wind turbines.

[0022] Specifically, the conventional wind turbine foundation structure is a reinforced concrete circular spread foundation. To ensure construction safety, the slope of the foundation pit is usually set at 1:1 or even greater. The diameter of large wind turbine foundations is typically 20-30 meters, meaning that the excavation diameter of the foundation pit after sloping can reach 36-50 meters, resulting in a large land area occupied by the foundation pit. In actual construction scenarios, an excessively large land area will significantly increase the amount of earthwork excavation and backfilling, correspondingly increasing transportation, waste disposal, and backfilling costs, and extending the construction period of the foundation pit. In addition, foundation pits constructed using traditional methods generally suffer from poor overall stability. These characteristics mean that the construction of foundation pits using traditional methods causes significant disturbance to the surrounding environment, and in ecologically sensitive areas, it may not meet environmental protection requirements.

[0023] In view of this, this application provides a construction method for wind turbine foundation pits in desert areas. Exemplarily, this method can be used to construct wind turbine foundation pits in geological conditions such as collapsible loess, general cohesive soil, silt, sand, and weakly weathered rock, or other similar geological conditions. The following is in conjunction with... Figures 1-8 The construction method for the foundation pit of the wind turbine is described in detail. See [link / reference]. Figure 1 The construction method for the wind turbine foundation pit includes the following steps: Step S101: Within the selected foundation site, excavate downwards to a certain depth according to the designed slope to form a foundation pit.

[0024] The design slope can be selected according to actual needs, and this application does not limit it. In one example, in order to reduce the land area occupied by the foundation pit, thereby reducing the amount of earthwork excavation and backfilling, the design slope can be set to 1:0.75.

[0025] In this embodiment, the foundation pit is excavated using a sloping layer method, following the principle of "excavating one layer and supporting one layer" during the excavation process. Specifically, after excavating to a certain depth according to the design slope to form a slope layer, the support structure for this slope layer is constructed according to steps S102-S104 below. After the strength of the support structure for this slope layer reaches the design requirements, the foundation pit is further excavated to a certain depth to form the next slope layer, and the support structure for this next slope layer is constructed according to steps S102-S104 below. After the strength of the support structure for this next slope layer reaches the design requirements, the foundation pit is further excavated to a certain depth to form the next slope layer, and the support structure for the next slope layer is constructed according to steps S102-S104 below. This process is repeated until the lowest slope layer is excavated, ensuring the foundation pit reaches the design depth, and the support structure for the lowest slope layer is constructed according to steps S102-S104 below.

[0026] In one example, during the excavation of a foundation pit using the inclined plane layering method, the layer thickness can be controlled to not exceed 2 meters. The layer thickness refers to the thickness of the excavated soil used to form a new slope layer each time a new layer of slope is formed by further excavating downwards on the basis of the current foundation pit.

[0027] Step S102: Drive-in steel pipe soil nails 1 into the slope formed by excavation at the design angle according to the first design spacing; part of the driven-in steel pipe soil nails 1 is fixed in the stratum, and the other part is exposed outside the stratum.

[0028] For details on the installation of driven steel pipe soil nails 1 on slopes, please refer to [link / reference needed]. Figure 2 The illustration is shown in the image.

[0029] The first design spacing includes a vertical spacing and a horizontal spacing. The vertical spacing refers to the vertical distance between two adjacent driven steel pipe soil nails 1, while the horizontal spacing refers to the horizontal distance between two adjacent driven steel pipe soil nails 1. This application does not specifically limit the values ​​of the vertical and horizontal spacing. In one example, both the vertical and horizontal spacing can be set to 200 mm.

[0030] The design angle refers to the angle between the length direction of the driven steel pipe soil nail 1 and the horizontal plane, that is... Figure 2 The angle α is shown in the figure. The design angle can be set according to actual needs; in one example, the design angle can be set to 15°.

[0031] The design length of the exposed portion of the driven steel pipe soil nail 1 (that is, the part of the driven steel pipe soil nail 1 exposed outside the stratum after being driven into the slope) can also be set according to actual needs. In one example, the design length of the exposed portion can be set to 100-200mm.

[0032] In actual construction scenarios, the process of driving driven steel pipe soil nails 1 into the slope can include: first, marking points on the slope according to the first design spacing to determine the hole positions of the soil nails, and determining the angle and depth of each soil nail hole according to the design angle, the length of the driven steel pipe soil nails 1 used, and the designed length of the exposed part; drilling holes at the hole positions according to the determined angle and hole depth to form soil nail holes; and then driving the driven steel pipe soil nails 1 into the soil nail holes, so that part of the driven steel pipe soil nails 1 is fixed in the stratum and the other part is exposed outside the stratum.

[0033] For example, when drilling at a hole location, for soil layers such as clay, silty clay, and silt, a Luoyang shovel can be used for hole formation; for geological layers such as sand, silt, gravel, and weakly weathered rock, an impact drill or down-the-hole hammer can be used. During drilling, the drill tip is aligned with the hole location and drilled steadily, with drill rods installed section by section as the hole depth increases. The angle is strictly controlled during drilling. Once the hole reaches the determined depth, drilling should stop, and the drill rod or Luoyang shovel should be rotated for one minute before slowly withdrawing the drill. Accumulated soil at the hole opening should be cleaned promptly to reduce resistance from soil return. In one example, when drilling, the design diameter of the soil nail hole can be determined based on the diameter of the driven steel pipe soil nail 1, ensuring that the drill bit diameter is at least 3mm larger than the design diameter.

[0034] In one example, when the design angle is set to 15°, the allowable deviation of the hole inclination angle can be controlled to ±5% during the drilling process to form a soil nail hole.

[0035] In one example, the driven steel pipe soil nail 1 can be 3 meters long and 48mm in diameter. 3.5 mm (outer diameter 48 mm, wall thickness 3.5 mm) steel pipe. For this example, the diameter of the soil nail hole can be set to 80-120 mm, and the positional deviation can be controlled within ±50 mm; and the depth of the soil nail hole can be set to 3100-3200 mm, so that the drilling depth is 100-200 mm longer than the length of the driven steel pipe soil nail 1, so as to facilitate the driving of the driven steel pipe soil nail 1 and grouting.

[0036] Before driving the driven steel pipe soil nail 1 into the soil nail hole, the guide frame can be installed first. This includes: first, fixing the guide frame to the slope or operating platform, then adjusting the angle of the guide frame to match the design angle of the driven steel pipe soil nail 1, and ensuring the guide frame is stable to prevent it from shifting during the driving process. After the guide frame is installed, the driven steel pipe can be positioned, including: placing the processed driven steel pipe soil nail 1 into the guide frame, adjusting the driven steel pipe soil nail 1 to align with the driving point of the soil nail hole, and checking whether the verticality or inclination angle of the driven steel pipe soil nail 1 meets the requirements. After the driven steel pipe soil nail 1 is in place, it can be driven into the soil nail hole, including: starting the vibratory hammer or hydraulic hammer and driving the driven steel pipe soil nail 1 into the soil along the guide frame; during the driving process, the hammering direction should be kept stable to prevent the driven steel pipe soil nail 1 from bending, and the driving speed should be reasonably controlled to avoid excessive impact causing deformation of the driven steel pipe soil nail 1 or detachment of the interface.

[0037] During the process of driving the driven steel pipe soil nail 1 into the soil nail hole, it should be ensured that the driving depth of the driven steel pipe soil nail 1 meets the design requirements, and the deviation should be controlled within the preset allowable deviation range (such as ±100mm). Specifically, in order to control the deviation, the position of the driven steel pipe soil nail 1 can be corrected after the driving is completed, including: checking the position, inclination angle and exposed length of the driven steel pipe soil nail 1. If the actual length of the exposed part deviates from its design length by more than the allowable deviation range, the driven steel pipe soil nail 1 should be re-driven or re-driven.

[0038] In one example, during the layered excavation of the foundation pit, the excavation depth of each layer can be controlled to not exceed the vertical spacing of the driven steel pipe soil nails 1. The excavation depth of one layer is the depth to which further excavation is carried out on the basis of the current foundation pit to return to the depth further excavated in step S102.

[0039] Step S103: Along the slope formed by excavation, lay a mesh reinforcement 2 with a certain spacing between it and the slope, and weld the mesh reinforcement 2 to the part of the driven steel pipe soil nail 1 exposed outside the stratum.

[0040] In this embodiment, the mesh reinforcement 2 can be considered to be laid along the slope, but it does not directly contact the slope; instead, a certain distance is formed between it and the slope. Specifically, the mesh reinforcement 2 can form a distance with the slope under the support of the driven steel pipe soil nail 1 welded to it. For details on the arrangement of the mesh reinforcement 2 and the driven steel pipe soil nail 1 on the slope, please refer to [link to relevant documentation]. Figure 3The diagram illustrates this. The spacing between the mesh reinforcement 2 and the slope can be set according to actual needs. In one example, the spacing between the mesh reinforcement 2 and the slope can be set to be no less than 30mm to ensure the thickness of the concrete layer formed on the slope in step S104.

[0041] In one example, the reinforcing mesh 2 can be made of a single layer of HPB300 (d8)@200x200 (8mm diameter, 200mm longitudinal spacing, and 200mm transverse spacing plain round steel bars) reinforcing mesh, and the lap length of the reinforcing mesh 2 can be 300mm. Furthermore, during the processing of the reinforcing mesh 2, to ensure its quality, the dimensional deviation and mesh spacing deviation can be controlled to not exceed ±10mm; after the reinforcing mesh 2 is laid on the slope, the fit deviation between the reinforcing mesh 2 and the slope can be controlled to not exceed ±20mm.

[0042] In one possible implementation of this application, to ensure that the mesh reinforcement 2 is firmly laid on the outside of the slope, after step S102 and before step S103, positioning reinforcement 4 can be driven into the excavated slope according to the second design spacing, so that part of the positioning reinforcement 4 is fixed in the stratum and the other part is exposed outside the stratum; and in step S103, the mesh reinforcement 2 is specifically laid along the excavated slope, the mesh reinforcement 2 is welded to the end of the positioning reinforcement 4 exposed outside the stratum, and the mesh reinforcement 2 is welded to the part of the driven steel pipe soil nail 1 exposed outside the stratum, so that the mesh reinforcement 2 forms a certain spacing with the slope under the support of the positioning reinforcement 4 and the driven steel pipe soil nail 1.

[0043] For details on the installation of the mesh reinforcement 2, positioning reinforcement 4, and driven steel pipe soil nail 1 on the slope, please refer to [link / reference needed]. Figure 3 The illustration is shown in the image.

[0044] Specifically, positioning bars 4 can be nailed into the slope in a quincunx pattern, and the second design spacing between adjacent positioning bars 4 can be set according to actual needs. For example, the second design spacing can be set to 2.0 meters.

[0045] In one example, the positioning bar 4 can be made of Φ12 HRB400 (12mm diameter, grade III threaded steel) rebar, with a length of 200-300mm. For instance, when the length of the positioning bar 4 is 200-300mm, one end of the positioning bar 4 can be inserted into the soil or rock of the slope to a depth of at least 150mm, and the other end of the positioning bar 4 can be welded and fixed to the mesh reinforcement 2, ensuring that the distance between the mesh reinforcement 2 and the slope surface is at least 30mm.

[0046] In addition, if there are already driven steel pipe soil nails 1 at the points on the slope where the positioning reinforcement 4 is to be driven into the slope, as determined by the second design spacing, then it is not necessary to drive the positioning reinforcement 4 into those points again. The mesh reinforcement 2 can then be directly welded to the driven steel pipe soil nail 1 at those points.

[0047] In one example, during the welding of the mesh reinforcement 2 to the positioning reinforcement 4, and the welding of the mesh reinforcement 2 to the driven steel pipe soil nail 1, the number of welding points at each node shall not be less than 3, the weld length shall not be less than 50mm, and the weld thickness shall not be less than 6mm, so as to ensure a firm connection.

[0048] In one possible implementation of this application, after laying the mesh reinforcement 2 according to step S103 and before performing the subsequent step S104, a reinforcing rib 5 can be further provided on the outside of the mesh reinforcement 2, and the reinforcing rib 5 can be welded to the mesh reinforcement 2 to further improve the firmness of the mesh reinforcement 2.

[0049] For example, when setting reinforcing ribs 5 on the outside of the mesh reinforcement 2, a portion of reinforcing ribs 5 that abut against the driven steel pipe soil nail 1 can be set around the driven steel pipe soil nail 1, and this portion of reinforcing ribs 5 can be welded to the mesh reinforcement 2 and the driven steel pipe soil nail 1. In one example, to ensure that the rod of the driven steel pipe soil nail 1 is firmly connected to the reinforcing ribs 5, the lap length of the reinforcing ribs 5 can be set to 10d (10 times the diameter of the reinforcing bar).

[0050] In one possible implementation of this application, after setting the reinforcing rib 5 on the outside of the mesh reinforcement 2 and before performing the subsequent step S104, an equilateral angle steel 6 that abuts against the driven steel pipe soil nail 1 can be further set on the outside of the reinforcing rib 5. The equilateral angle steel 6 is welded to the reinforcing rib 5 and the driven steel pipe soil nail 1 to further improve the firmness of the mesh reinforcement 2.

[0051] In one example, the dimension of the equilateral angle steel 6 can be L50. 5mm (50mm side length, 5mm thickness), length can be 200mm.

[0052] The installation method for driven steel pipe soil nails 1, mesh reinforcement 2, reinforcing bars 5, and equilateral angle steel 6 on the slope can be referred to Figure 4 The illustration is shown in the image.

[0053] Step S104: Spray concrete onto the slope after the mesh reinforcement 2 is laid, so that the concrete covers the exposed parts of the mesh reinforcement 2 and the driven steel pipe soil nails 1 to form a support structure.

[0054] The support structure includes the aforementioned driven steel pipe soil nails 1, mesh reinforcement 2, and a concrete surface layer 3 formed by the shotcrete process. Specifically, the driven steel pipe soil nails 1 provide active pull-out resistance to prevent overall slope instability; the mesh reinforcement 2 enhances the integrity of the concrete surface layer 3, preventing localized spalling; the concrete surface layer 3 seals the slope, isolates it from rainwater erosion, and together with the mesh reinforcement 2, forms a flexible support shell, transferring earth pressure to the driven steel pipe soil nails 1 and avoiding localized stress concentration. Therefore, based on the synergistic effect of "driven steel pipe soil nails 1 + mesh reinforcement 2 + concrete surface layer 3," the support structure can effectively improve the stability of the foundation pit slope.

[0055] In one example, ordinary Portland cement of grade P.O42.5 (a strength grade) with an initial setting time not exceeding 3 hours and a final setting time not exceeding 12 hours can be used. Medium sand with a mud content not exceeding 3% is selected as fine aggregate, and crushed stone with a mud content not exceeding 1% and a particle size not exceeding 15mm is selected as coarse aggregate to prepare the concrete used in step S104. Specifically, a quick-setting agent accounting for 3%-5% of the cement dosage can be added during the preparation process (ensuring that the initial setting time does not exceed 5 minutes and the final setting time does not exceed 10 minutes), and the water-cement ratio is controlled at 0.45-0.55. The concrete is prepared according to a mass ratio of cement:medium sand:crushed stone = 1:2.0:2.5, and the slump is controlled at 80-120mm. The strength grade of the prepared concrete is C25 (a strength grade).

[0056] In one example, during the shotcrete process, the shotcrete thickness in the regular area can be controlled at 100-120mm, while the shotcrete thickness in the weak interlayer, slope top and slope toe areas can be increased to 150mm. The thickness of the concrete surface layer 3 on the outside of the mesh reinforcement 2 (that is, the side of the mesh reinforcement 2 away from the slope) should be controlled to be no less than 30mm.

[0057] For example, when spraying concrete, the working pressure of the air compressor can be set to 0.6-0.8 MPa, and the outlet pressure of the sprayer can be set to 0.4-0.6 MPa. During the spraying process, the nozzle should be kept perpendicular to the surface being sprayed, and the distance between the nozzle and the surface being sprayed should be 600-1000 mm. In the actual process of spraying concrete, a 30-50 mm thick initial layer can be sprayed first to fix the mesh reinforcement 2, then a middle layer can be sprayed to ensure that the thickness of the concrete surface layer 3 outside the mesh reinforcement 2 reaches the design thickness. Finally, a second layer can be sprayed to finish the surface, ensuring that the slope of the sprayed concrete is flat, without exposed reinforcement or voids. Furthermore, during the spraying of the initial or middle layer, the spraying operation can be carried out in sections and pieces sequentially, with the spraying sequence from bottom to top, and each section being 2-3 meters long.

[0058] In addition, during construction, manual finishing should be carried out according to the designed slope to ensure that the thickness of the sprayed concrete surface layer 3 is consistent and the surface is flat and aesthetically pleasing. During the spraying of concrete, the mesh reinforcement 2 should also be supported to ensure that the thickness of the concrete protective layer on the inner side of the mesh reinforcement 2 (i.e., the side of the mesh reinforcement 2 closest to the slope) is not less than 30mm, and the sprayed concrete thickness should be appropriately increased at the joints of the driven steel pipe soil nails 1.

[0059] Step S105: If the strength of the formed support structure meets the design requirements, further excavate to a certain depth on the basis of the current foundation pit, and return to the aforementioned step S102 until the foundation pit depth reaches the design depth.

[0060] Specifically, after constructing the support structure for the newly excavated slope layer based on steps S102-S104, once it is confirmed that the strength of the support structure for this slope layer meets the design requirements, the excavation can be carried out further to a certain depth to form the next lower slope layer, and the process returns to step S102. This continues until the excavation reaches the designed depth and the support structure for the lowest slope layer is constructed based on steps S102-S104.

[0061] In actual construction scenarios, the strength of the support structure can be determined based on specific needs to determine whether it meets the design requirements. This application does not limit the specific determination method. For example, after the support structure for the newly excavated slope layer is completed, the strength of the support structure for that slope layer can be considered to have met the design requirements if the concrete surface layer 3 of the support structure meets a preset first condition: the slope shows no obvious deformation, cracks, spalling, or slippage. The preset first condition may include: the strength of the concrete surface layer 3 reaches more than 70% of the design strength, or the curing time of the concrete surface layer 3 reaches approximately 24 hours (specifically based on the strength of the concrete surface layer 3 test blocks).

[0062] As can be seen from the above, the construction method for wind turbine foundation pits in desert areas provided in this application uses a composite support system of "driven steel pipe soil nails 1 + mesh reinforcement 2 + shotcrete" to protect the slope, thereby effectively improving the stability of the foundation pit slope.

[0063] Furthermore, the effective protection provided by the aforementioned support structure for the stability of the foundation pit slope allows for the appropriate steepening of the excavation slope while avoiding adverse effects on the stability of the foundation pit during actual construction. This creates the preconditions for steepening the excavation slope to save land area occupied by the foundation pit, thereby reducing the amount of earthwork excavation and backfilling, reducing transportation, waste soil, and backfilling costs, and shortening the construction period to minimize disturbance to the surrounding environment.

[0064] In one example, the construction method for the wind turbine foundation pit provided in the embodiments of this application can be used to construct the foundation pit with an excavation depth of 5-12 meters using a 1:0.75 slope. Compared with the conventional wind turbine foundation 1:1 design slope excavation, the land area occupied can be reduced by about 180m², and the amount of earthwork excavation and backfilling can be reduced by about 540m³.

[0065] In one embodiment of this application, for the slope formed during the first downward excavation (i.e., the first layer of slope, which is the slope formed based on step S101), when laying the mesh reinforcement 2 along the slope formed by excavation according to the aforementioned step S103, specifically, a portion of the mesh reinforcement 2 can extend along the slope and form a certain gap with the slope, while another portion extends to the outer side of the slope top; and the portion of the mesh reinforcement 2 extending along the slope is welded to the portion of the driven steel pipe soil nail 1 exposed outside the stratum, and the portion of the mesh reinforcement 2 extending to the outer side of the slope top is welded to the ground anchor 7 pre-set on the outer side of the slope top.

[0066] The length D of the portion of the reinforcing mesh 2 extending to the outer edge of the slope can be set according to actual needs. In one example, the length D of the portion of the reinforcing mesh 2 extending to the outer edge of the slope can be set to 1 meter, and the ground anchor 7 can be set at a position 800mm away from the top of the slope.

[0067] The installation details of ground anchor 7 and mesh reinforcement 2 on the outer side of the slope crest can be found in [reference needed]. Figure 5 The illustration.

[0068] As is easy to understand, in practical applications, multiple ground anchors 7 can be set on the outer side of the slope top to surround the foundation pit. In one example, the ground anchors 7 can be made of Φ22 (22mm in diameter) steel bars with a length of 1500mm, and the spacing between adjacent ground anchors 7 can be set to 1500mm. The depth of each ground anchor 7 in the soil is 1200mm, and the length of the part exposed outside the soil layer is 300mm.

[0069] Specifically, the ground anchor 7 can fix the mesh reinforcement 2, preventing the mesh reinforcement 2 from falling into the pit under the action of gravity, thereby helping to improve the stability of the mesh reinforcement 2.

[0070] In one example, when the mesh reinforcement 2 is fixed by the ground anchor 7, a locking bar 8 can also be set on the side of the site opposite to the foundation on the outside of the slope top where the mesh reinforcement 2 extends, and is located on the side of the ground anchor 7 away from the foundation pit. The locking bar 8 is then welded to the mesh reinforcement 2 and the ground anchor 7.

[0071] The installation details of ground anchor 7, locking reinforcement 8, and mesh reinforcement 2 on the outer side of the slope crest can be found in [reference needed]. Figure 5 The illustration.

[0072] In one example, the locking rib 8 can be made of 100mm HRB400(d22) (22mm diameter grade III threaded steel) rebar.

[0073] Based on the embodiments of this application, the locking rib 8, the mesh rib 2, and the ground anchor 7 form a reliable connection and constitute a whole, thereby effectively ensuring the stability of the mesh rib 2.

[0074] In one embodiment of this application, such as Figures 6-7 As illustrated, the driven steel pipe soil nail 1 has a closed pointed cone shape at one end fixed in the stratum, and an open end exposed outside the stratum; and the side wall of the driven steel pipe soil nail 1 is provided with grouting holes 101 arranged at the third design interval, and a plurality of angle steel barbs 102 respectively provided outside each grouting hole 101.

[0075] Specifically, the grouting holes 101 can be symmetrically arranged around the periphery of the driven steel pipe soil nail 1. In one example, they can be arranged as follows: Figure 6 As illustrated, two grouting holes 101 are provided at each grouting section. For example, for a driven steel pipe soil nail 1 with an outer diameter d1 of 48mm, the distance d2 between the grouting hole 101 closest to the nail top (the open end of the driven steel pipe soil nail 1) and the nail top can be set to 1 / 2 to 1 / 3 of the total length of the driven steel pipe soil nail 1. The spacing d3 of the grouting holes 101 in the length direction of the driven steel pipe soil nail 1 (the third design spacing) is 250-500mm. The distance d4 between the grouting hole 101 closest to the nail bottom (the closed conical end of the driven steel pipe soil nail 1) and the nail bottom is 250-500mm.

[0076] The angle steel barbs 102 installed outside the grouting hole 101 are used to protect the grouting hole 101 to prevent soil or rock in the stratum from blocking the grouting hole 101 and preventing the cement grout injected into the driven steel pipe soil nail 1 from seeping out of the grouting hole 101. In one example, the angle steel barbs 102 can be made of Q235B (grade B carbon structural steel conforming to GB / T 700-2006 standard) hot-rolled equal angle steel. The width of the angle steel can be set to 30-63mm, the thickness can be set to 3-6mm, and the length can be set to 50-60mm. The angle between the angle steel barbs 102 and the pipe body of the driven steel pipe soil nail 1 can be set to 20°-30°.

[0077] In one example, the apex angle of the cone at the base of the driven steel pipe soil nail can be 30°-60°.

[0078] In one example, a reinforcing structure can be provided at the top of the driven steel pipe soil nail 1 to prevent deformation of the steel pipe during driving, thereby improving the structural stability of the driven steel pipe soil nail 1.

[0079] In this embodiment of the application, after the driven steel pipe soil nail 1 is driven into the slope, it is also necessary to inject grout into the driven steel pipe soil nail 1 through the opening of the driven steel pipe soil nail 1.

[0080] Grouting involves injecting cement grout into the driven steel pipe soil nail 1. By grouting the driven steel pipe soil nail 1, the cement grout can flow out from the grouting hole 101 of the driven steel pipe soil nail 1 and seep into the stratum, so that the driven steel pipe soil nail 1 and the stratum become a whole, thereby helping to improve the stability of the foundation pit slope.

[0081] In one example, the cement grout used for grouting can be ordinary Portland cement grout of grade 42.5 or higher with a water-cement ratio of 0.5. For instance, the grouting pressure can be controlled to be no less than 0.6 MPa during the grouting process.

[0082] The amount of grout injected during the grouting process can be determined based on the stratum and the location of the driven steel pipe soil nail 1. Specifically, when grouting into the driven steel pipe soil nail 1, grouting should be stopped after grout return appears around the top of the pipe. When no grout return appears, intermittent grouting can be used to inject grout into the driven steel pipe soil nail 1.

[0083] In addition, the cement grout used in the grouting process should be stirred evenly and used immediately after mixing. The cement grout mixed at one time should be used up before initial setting.

[0084] In one embodiment of this application, after the excavation reaches the designed depth of the foundation pit, an annular drainage ditch 10 with a certain distance between it and the slope toe (i.e., the slope bottom line) can be set at the bottom of the foundation pit, and at least one water collection well 11 connected to the annular drainage ditch 10 can be set.

[0085] The arrangement of the annular drainage ditch 10 and the collection well 11 at the bottom of the foundation pit can be found in [reference needed]. Figure 2 and Figure 8 The illustration shows that, Figure 2 The locations of the annular drainage ditch 10 and the collection well 11 on the cross-section of the foundation pit are shown. Figure 8 This shows the position of the annular drainage ditch 10 and the water collection well 11 in the top view of the foundation pit.

[0086] The distance between the annular drainage ditch 10 and the toe of the slope can be set according to actual needs. In one example, the annular drainage ditch 10 can be set 1 meter away from the toe of the slope.

[0087] The number and size of the water collection wells 11 can also be set according to actual needs. For an example, please refer to... Figure 8 The diagram illustrates that two water collection wells 11 are set for a wind turbine foundation, and the dimensions of the water collection wells 11 are set to 500×500×500mm.

[0088] The annular drainage ditch 10 can be used to collect groundwater and rainwater within the foundation pit slope, and the water collected by the annular drainage ditch 10 can be gathered into the sump well 11. During the actual construction process, the water in the sump well should be pumped out in a timely manner to reduce the soil moisture and prevent the pit from being soaked by groundwater for a long time, so as to ensure the stability of the foundation pit slope.

[0089] In one possible implementation, in order to drain the accumulated water in the lower layer of the foundation pit slope to ensure slope stability, drainage holes 9 arranged at intervals can also be provided on the concrete surface layer 3.

[0090] In one example, the spacing between the drain holes 9 can be set to 2.5m × 2.5m.

[0091] Specifically, for the newly excavated slope, before spraying concrete in step S104, drainage pipes spaced apart can be inserted into the slope, with the first end of each pipe inserted into the ground and the second end exposed outside. During the spraying of concrete in step S104, the drainage pipes should be avoided to prevent them from being blocked by concrete, and the second end of each pipe should be exposed outside the concrete surface layer 3 to form drainage holes 9. In one example, the drainage pipes can be made of PVC (Polyvinyl Chloride, a synthetic material).

[0092] For details on the installation of drainage hole 9 on the slope, please refer to [link / reference needed]. Figure 2 The illustration is shown in the image.

[0093] By setting drainage holes 9 on the concrete surface layer 3, water accumulated in the lower layer of the slope due to groundwater, rainwater, etc., can be effectively drained, preventing the concrete surface layer 3 from cracking and falling off due to water pressure, thereby helping to ensure the stability of the slope. In this embodiment, the annular drainage ditch 10 can effectively intercept the water flowing out of the drainage holes 9 and collect it into the collection well 11, so as to prevent the water from soaking the foundation pit and affecting the stability of the slope.

[0094] In one embodiment of this application, before performing the aforementioned step S101, an annular water-retaining platform 12 extending along the excavation edge and having a certain distance between it and the excavation edge can be set outside the excavation edge on the foundation site.

[0095] The excavation boundary line, also known as the pit top line, is the boundary line where the pit excavation will take place. The details of the annular water-retaining platform 12 can be found in [reference needed]. Figure 2 and Figure 8 The illustration.

[0096] In one example, the annular water-retaining platform 12 can be set 2m away from the top of the pit and can be arranged along the natural slope of the site.

[0097] In one example, a ring-shaped water-retaining platform 12 can be constructed using C25 concrete, with a width of 300mm and a height of 300mm.

[0098] In another example, for ecologically fragile areas or areas with high environmental protection requirements, considering factors such as project environmental protection, subsequent site restoration, and construction costs, the construction materials for the annular water-retaining platform 12 can be sourced locally. Furthermore, it can be set with a width of 800mm and a height of 400mm.

[0099] like Figure 2 As illustrated, the area outside the annular water-retaining platform 12 is the original terrain outside the site. In one example, while constructing the annular water-retaining platform 12, the ground elevation outside the site can also be constructed to form a drainage slope to prevent rainwater from eroding the slope.

[0100] To facilitate understanding, the following provides an illustrative example of a possible construction process for foundation pit construction based on the construction method provided in the above embodiments of this application. Exemplarily, this construction process is applicable to the construction of large wind turbine foundation pits with excavation depths of approximately 5-12 meters in geological conditions such as collapsible loess, general cohesive soil, silt, sand, and weakly weathered rock, or other similar geological conditions. See [link to relevant documentation]. Figure 9 The construction process specifically includes the following steps: Step S901: Construction preparation.

[0101] Specifically, thorough pre-construction preparations should be made, including technical preparation, site preparation, material preparation, and labor preparation. Workers should be familiarized with the construction drawings, geological survey report, and foundation pit support design documents. The layout, length, spacing, design angle, and shotcrete parameters for the driven steel pipe soil nails (1) should be clearly defined. The site should be leveled, the construction area cleared, temporary power and water supply arrangements completed, and fencing, warning signs, and warning lights installed to ensure construction safety.

[0102] Step S902: Construction of the water-retaining platform at the top of the wind turbine foundation slope.

[0103] Specifically, the surveying and layout of the water-retaining platform construction area was carried out and a circular water-retaining platform 12 was constructed, as detailed in the previous text.

[0104] Step S903: Layered excavation of the wind turbine foundation pit.

[0105] The excavation process of the foundation pit should strictly follow the principles of segmentation, layering, balance, and timeliness, as well as the principle of "excavating one layer and supporting one layer". Each layer of earthwork excavation can only be carried out after the strength of the upper support structure has reached the design requirements. After excavating one layer of earthwork, the construction of the support structure of that layer should be completed within 24 hours. Over-excavation is prohibited.

[0106] During the earthwork excavation, no loads or heavy machinery are allowed to be piled up within 2 meters of the edge of the foundation pit. The foundation pit is excavated using the sloping layer method, with each layer not exceeding 2 meters in thickness. The wind turbine foundation pit is excavated using a slope, with a slope of 1:0.75.

[0107] Step S904: Repairing the slope of the wind turbine foundation pit.

[0108] After each layer of earthwork is excavated, loose soil and loose rocks are promptly removed manually. The slope is controlled according to the design slope value to ensure that the flatness deviation does not exceed ±50mm, thus creating conditions for the laying of the mesh reinforcement and the construction of shotcrete.

[0109] Step S905: Drilling holes for the wind turbine foundation pit.

[0110] Specifically, this involves surveying and setting out lines, and drilling holes on the slope to create soil nailing holes, as explained in the previous text.

[0111] Step S906: Clean the hole.

[0112] Specifically, after drilling the soil nail holes, the soil accumulated at the hole opening should be cleaned up in a timely manner to reduce the resistance of the soil returning from the hole.

[0113] Step S907: Installation of driven steel pipe soil nail 1.

[0114] Specifically, the driven steel pipe soil nail 1 is driven into the soil nail hole drilled in step S905.

[0115] Step S908b: Grouting.

[0116] This involves grouting into the driven steel pipe soil nail 1, as detailed in the previous description. Furthermore, before performing step S908b, cement grout should be mixed according to step S908a and used immediately after mixing.

[0117] Step S909: Maintenance.

[0118] This means curing the driven steel pipe soil nail 1 after grouting.

[0119] Step S910: Install positioning rib 4.

[0120] For details on the installation process of positioning rib 4, please refer to the instructions above.

[0121] Step S911b: Laying and fixing of the mesh reinforcement 2.

[0122] For details on the laying and fixing process of the mesh reinforcement 2, please refer to the instructions above. In addition, before performing step S911b, the mesh reinforcement 2 should be prepared according to step S911a.

[0123] Step S912: Fix the end of the steel pipe in the wind turbine foundation pit.

[0124] That is, the exposed part of the driven steel pipe soil nail 1 is fixed by setting up a pad, nut / welding, etc.

[0125] Step S913b: Shotcrete spraying for wind turbine foundation pit.

[0126] See the previous explanation of step S104. Furthermore, before performing step S913b, concrete mixing should be carried out according to step S913a.

[0127] Step S914: Excavation of the lower layer of the wind turbine foundation.

[0128] Specifically, once the upper concrete surface layer reaches more than 70% of its design strength or has been cured for approximately 24 hours (the exact amount depends on the strength of the test blocks), and there are no obvious signs of deformation, cracks, spalling, or slippage on the slope, and the foundation pit monitoring data is stable or within acceptable limits, then the process can return to step S903 to excavate the lower layer of soil and repeat the cycle until the foundation pit depth reaches the design depth.

[0129] It can be seen that the above construction process, compared with the conventional 1:1 slope excavation scheme, reduces the slope of the excavation and adopts a composite support system of "driven-in steel pipe soil nails + mesh reinforcement + shotcrete". The composite support system of "driven-in steel pipe soil nails + mesh reinforcement + shotcrete" follows the following collaborative principles: First, stress coordination: the shotcrete surface layer and the driven-in steel pipe soil nails are fixed by welding to ensure effective transmission of soil pressure and avoid local stress concentration; second, structural coordination: the exposed parts of the mesh reinforcement and the driving-in steel pipe soil nails, as well as the positioning bars, are reliably connected, and the concrete surface layer completely covers the mesh reinforcement and the ends of the driven-in steel pipe soil nails to ensure continuous protection; third, schedule coordination: following the principle of "excavating one layer and supporting one layer", the excavation depth of each layer of the wind turbine foundation is ≤ the vertical spacing of the driven-in steel pipe soil nails, and the laying of the steel mesh and the construction of shotcrete are completed within 24 hours after excavation, reducing the exposure time of the slope.

[0130] By reducing the excavation slope, the land area occupied, the amount of earthwork excavation and backfilling can be effectively reduced, transportation, spoil disposal, and backfilling costs can be decreased, and the construction period can be shortened, thereby reducing disturbance to the surrounding environment. Through the stress coordination design and structural optimization of the composite support system of "driven steel pipe soil nails + mesh reinforcement + shotcrete," the overall stability of the slope can be guaranteed, and deformation control and safety protection requirements can be met. Therefore, the construction method for the wind turbine foundation pit provided in this application has the advantages of less earthwork excavation and better overall stability compared to conventional slope excavation methods; and compared to other deep foundation pit support structures, it has the advantages of fast construction speed, relatively low cost, low site requirements, low construction noise, low vibration, and ease of subsequent earthwork excavation and main construction.

[0131] In summary, the construction method for wind turbine foundation pits provided in this application not only improves slope stability but also features a simple structure, mature and reliable construction technology, high safety, and economic rationality. It has strong potential for widespread application and lays a solid foundation for safer and more economical construction of large-scale wind farms in desert areas and the application of large wind turbine foundations in complex scenarios. This effectively solves the current problems in desert areas where conventional slope excavation for deep foundation pits of large wind turbines involves large excavation volumes and low overall stability, while other deep foundation pit support structures suffer from low construction efficiency and unsatisfactory economics.

[0132] Based on the same inventive concept, this application also provides a wind turbine foundation pit for desert areas, which is constructed using the construction method for wind turbine foundation pits for desert areas provided in any of the above embodiments. For the beneficial effects and further details regarding this wind turbine foundation pit, please refer to the descriptions in the preceding method embodiments.

[0133] It should be noted that, in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0134] The various embodiments in this specification are described in a related manner. Similar or identical parts between embodiments can be referred to mutually. Each embodiment focuses on describing the differences from other embodiments. In particular, the wind turbine foundation pit embodiment is relatively simple in description because it is basically similar to the method embodiment; relevant parts can be referred to the descriptions in the method embodiment.

[0135] The above description is merely a preferred embodiment of this application and is not intended to limit the scope of protection of this application. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application are included within the scope of protection of this application.

Claims

1. A construction method for wind turbine foundation pits in desert areas, characterized in that, include: Within the selected foundation site, excavate downwards to a certain depth according to the designed slope to form a foundation pit; Driven steel pipe soil nails are driven into the slope formed by excavation at the designed angle according to the first design spacing; part of the driven steel pipe soil nails is fixed in the stratum, and the other part is exposed outside the stratum; Along the slope formed by excavation, a mesh reinforcement with a certain spacing between it and the slope is laid, and the mesh reinforcement is welded to the part of the driven steel pipe soil nail exposed outside the stratum. Shotcrete is applied to the soil slope after the mesh reinforcement is laid, so that the concrete covers the exposed portions of the mesh reinforcement and the driven steel pipe soil nails to form a support structure; the support structure includes the driven steel pipe soil nails, the mesh reinforcement, and a concrete surface layer formed by the shotcrete process. Once it is confirmed that the strength of the formed support structure meets the design requirements, further excavate to a certain depth based on the current foundation pit, and return to the step of driving driven steel pipe soil nails into the excavated slope at the design angle according to the first design spacing, until the foundation pit depth reaches the design depth.

2. The method according to claim 1, characterized in that, After driving driven steel pipe soil nails into the slope formed by excavation at the designed angle, and before laying the mesh reinforcement with a certain spacing between it and the slope, the method further includes: According to the second design spacing, positioning bars are driven into the slope formed by excavation, so that part of the positioning bars are fixed in the stratum and the other part is exposed outside the stratum; Along the slope formed by excavation, a mesh reinforcement with a certain spacing between it and the slope is laid, including: A mesh reinforcement is laid along the slope formed by excavation, and the mesh reinforcement is welded to the end of the positioning reinforcement exposed outside the stratum, so that the mesh reinforcement forms a certain gap with the slope under the support of the positioning reinforcement.

3. The method according to claim 1, characterized in that, For the slope formed during the first downward excavation, the laying of a mesh reinforcement with a certain spacing between it and the slope along the excavated slope includes: A mesh reinforcement is laid along the slope formed by excavation, such that part of the mesh reinforcement extends along the slope and forms a certain gap with the slope, while another part extends to the outer side of the slope top. The portion of the mesh reinforcement extending along the slope is welded to the portion of the driven steel pipe soil nail exposed outside the stratum, and the portion of the mesh reinforcement extending to the outer side of the slope top is welded to the ground anchor pre-installed on the outer side of the slope top.

4. The method according to claim 3, characterized in that, After laying a mesh reinforcement bar with a certain spacing between it and the slope formed by excavation, and before spraying concrete onto the slope after laying the mesh reinforcement bar, the method further includes: On the side opposite to the foundation site in the portion of the mesh reinforcement extending to the outer side of the slope top, a locking bar is provided that abuts against the ground anchor and is located on the side of the ground anchor away from the foundation pit. The locking bar is then welded to the mesh reinforcement and the ground anchor.

5. The method according to claim 1, characterized in that, The driven steel pipe soil nail is fixed in the formation at one end in a closed cone shape, and the other end exposed outside the formation has an opening; the side wall of the driven steel pipe soil nail is provided with grouting holes arranged at the third design interval, and multiple angle steel barbs are respectively provided outside each grouting hole. After driving driven steel pipe soil nails into the slope formed by excavation at the designed angle, the method further includes: Grout is injected into the driven steel pipe soil nail through the opening.

6. The method according to claim 1, characterized in that, Before spraying concrete onto the slope after the reinforcing mesh has been laid, the method further includes: Drainage pipes arranged at intervals are inserted into the slope, such that the first end of the drainage pipe is inserted into the stratum and the second end is exposed outside the stratum. The spraying of concrete onto the slope after the reinforcement mesh has been laid includes: Avoiding the inserted drainage pipe, spray concrete onto the soil slope after the mesh reinforcement is laid, so that the second end of the mesh reinforcement is exposed outside the concrete surface layer formed by the spray concrete process, forming a drainage hole; After excavation to the designed depth of the foundation pit, the method further includes: At the bottom of the foundation pit, a ring-shaped drainage ditch is set up at a certain distance from the toe of the slope; At least one water collection well is provided that is connected to the annular drainage ditch.

7. The method according to claim 1, characterized in that, Before excavating a certain depth downwards according to the designed slope to form a foundation pit within the selected foundation site, the method further includes: An annular water-retaining platform is set outside the excavation edge line on the foundation site, extending along the excavation edge line and having a certain distance between it and the excavation edge line; A drainage slope is formed on the outer side of the annular water-retaining platform.

8. The method according to claim 1, characterized in that, The first design spacing includes vertical spacing and horizontal spacing; during construction, the depth of the unsupported portion of the foundation pit excavated downwards does not exceed the vertical spacing.

9. The method according to claim 1, characterized in that, The designed slope is 1:0.

75.

10. A wind turbine foundation pit for use in desert areas, characterized in that, The foundation pit for wind turbines in desert areas is constructed using the construction method described in any one of claims 1-9.

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