Soil nail for reserved earthwork part of foundation pit and construction method thereof
By using a temporary support system and a lightweight filling layer in the reserved earth part of the foundation pit, combined with microwave curing technology and reinforcement mechanism, the problems of difficult, high cost and many safety hazards in the reserved earth part of the foundation pit in the existing technology are solved, and the construction cycle is shortened, efficiency improvement and safety improvement are achieved.
Patent Information
- Application Number
- CN202411986564.7
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-12-31
- Publication Date
- 2025-04-08
AI Technical Summary
The soil nail support in the reserved earth parts of the existing foundation pit has problems such as high construction difficulty, high cost, many safety hazards and long construction cycles, especially in the reserved earth area, the excavation efficiency is low and the degree of mechanization is not high.
The support rod and lightweight filling layer of the temporary support system are adopted to enhance the bearing capacity of the filling layer through microwave curing technology, replace the in-situ soil, reduce the amount of excavation in the later stage, and introduce reinforcement mechanisms to improve the stability and reinforcement effect of the soil nail body.
It effectively avoids slope instability, shortens the construction cycle, improves construction efficiency and safety, reduces resource waste and construction risks, and improves project quality.
Smart Images
Figure CN119777389A_ABST
Abstract
Description
Technical Field
[0001] The invention relates to the technical field of soil nail support, in particular to a soil nail for a reserved earthwork portion of a foundation pit and a construction method. Background Art
[0002] As one of the important means of foundation pit slope support, soil nail support has been widely used in various foundation pit engineering projects at home and abroad. By driving soil nails into the foundation pit wall and combining it with the sprayed concrete on the surface to form a composite retaining system, it effectively improves the stability of the slope and ensures the safety and economy of the foundation pit construction.
[0003] The existing soil nail support in the reserved earthwork area of the foundation pit is to retain the soil in the area without excavation, and then carry out construction after the reserved earthwork is removed in the subsequent stage. Although this treatment method can avoid the risk of damage caused by excessive force on the early soil nails to a certain extent, it faces many challenges in actual operation. On the one hand, due to the existence of reserved earthwork, it is difficult for equipment such as excavators to approach the working surface, which increases the difficulty and cost of construction; on the other hand, when the soil in the non-support area begins to be removed, the newly exposed unreinforced soil will be in an unstable state and needs to be supported quickly, otherwise it may cause safety accidents. There are obvious defects such as too long construction period, low degree of mechanization, and many safety hazards, which seriously affect the overall project progress and quality.
[0004] To this end, the present invention provides a soil nail for a reserved earthwork portion of a foundation pit and a construction method. Summary of the invention
[0005] In order to make up for the deficiencies of the prior art, at least one technical problem raised in the background technology is solved.
[0006] The present invention provides a soil nail for a reserved earthwork part of a foundation pit, comprising a foundation pit slope, reserved earthwork and a soil nail body; the side of the foundation pit slope is provided with reserved earthwork, a support rod is installed inside the reserved earthwork, and a temporary support rod is made of a galvanized steel pipe with a diameter of 48 mm and a wall thickness of 3.5 mm, which has good corrosion resistance and sufficient rigidity; a lightweight filling layer is provided on the surface of the reserved earthwork and the support rod, and microwave curing technology is adopted to enhance the bearing capacity of the lightweight filling layer; the frequency of microwave curing is set at 915 MHz, and the power range is 6 kW-12 kW to meet the curing requirements of fillers of different volumes; grouting holes are penetrated inside the foundation pit slope and the reserved earthwork, a soil nail body is installed inside the grouting hole, and a reinforcement mechanism is installed at the middle position of the soil nail body.
[0007] By adopting the above technical solution and introducing support rods of the temporary support system, the instability of the slope caused by premature unloading can be avoided. By using lightweight filling materials to replace the original soil, the amount of later excavation can be reduced, the construction process can be accelerated, and the overall cycle of soil nail construction in the reserved earthwork area of the foundation pit can be greatly shortened, thereby improving the overall benefits of the project and effectively solving the problem of low excavation efficiency in the reserved earthwork area. By adopting microwave curing technology, the mechanical properties of lightweight filling materials can be greatly improved in a short time, thereby improving the safety and reliability of the construction process.
[0008] Preferably, the support rod is a steel pipe, and the lightweight filling layer is foam plastic.
[0009] By adopting the above technical solution, the support rods can avoid slope instability caused by premature unloading. The lightweight filling layer replaces the original soil and is filled to the top of the temporary support rods, which can ensure that the pressure in the entire area is evenly distributed and prevent local settlement.
[0010] Preferably, in order to improve the reinforcement of the soil nail body to the foundation pit slope, further enable the soil nail body to reinforce the foundation pit slope and improve the stability of the soil nail body, the reinforcement mechanism includes a connecting sleeve, a reinforcement ring, a reinforcement nail and a pushing structure, a connecting sleeve is threadedly installed at the middle position of the soil nail body, a reinforcement ring is installed on the inner wall of the connecting sleeve, reinforcement nails are movably installed inside the connecting sleeve and the reinforcement ring, and a pushing structure is installed through the inside of the soil nail body.
[0011] By adopting the above technical scheme, the reinforcement of the soil nail body to the foundation pit slope can be improved, and the soil nail body can further reinforce the foundation pit slope, thereby improving the stability of the soil nail body. The reinforcement mechanism forms a composite soil structure by tightly combining the soil nail body with the surrounding soil, thereby improving the overall strength and stability of the soil. This reinforcement structure not only enhances the pull-out resistance and shear strength of the soil nail, but also enables the soil nail to better withstand the soil pressure and external load of the foundation pit slope.
[0012] Preferably, the pushing structure includes a rotating rod and a pushing block, the rotating rod is rotatably installed at an inner position of the soil nail body, and the pushing block is installed on the outer surface of the rotating rod close to the reinforcement ring.
[0013] By adopting the above technical scheme, the reinforcement nails can be inserted into the foundation pit slope by rotating the rotating rod and the pushing block, so that the soil nail body can reinforce the foundation pit slope. At the same time, the stability of the soil nail body can be improved to avoid the movement of the soil nail body and affect the support effect of the soil nail body on the foundation pit slope.
[0014] Preferably, in order to reinforce the soil nail body and improve the support of the soil nail body to the foundation pit slope, reinforcement plates are equidistantly installed on the outer surface of the rotating rod, and one end of the reinforcement plate close to the inner wall of the soil nail body is curved.
[0015] By adopting the above technical solution, the inside of the ungrouted soil nail body can be processed to avoid foreign matter blocking the grouting holes inside the soil nail body. At the same time, the soil nail body can be reinforced by the reinforcement plate to improve the support of the soil nail body to the foundation pit slope.
[0016] Preferably, in order to make the soil nail body centered inside the grouting hole and avoid the soil nail body being offset and one side contacting the inner wall of the grouting hole, which affects the later grouting, two sets of limit rods are symmetrically installed on the outer surface of the connecting sleeve, and the limit rods are equidistantly distributed on the outer surface of the connecting sleeve.
[0017] By adopting the above technical solution, the soil nail body can be centered inside the grouting hole to avoid the soil nail body from being offset and contacting the inner wall of the grouting hole, so that concrete can be better poured into the grouting hole through the inside of the soil nail body to form. Such a soil nail wall support structure not only has high stability and safety, but also can effectively resist the influence of external loads and deformation.
[0018] Preferably, in order to achieve fixed installation of the soil nail body, a plurality of groups of grouting holes are provided inside the soil nail body, and the grouting holes are distributed inside the soil nail body at equal distances.
[0019] By adopting the above technical scheme, concrete can be poured into the grouting hole through the grouting hole inside the soil nail body, so that the concrete is formed inside the grouting hole, and the soil nail body is reinforced and positioned, so that the soil nail body supports the foundation pit slope and can effectively improve the stability of the foundation pit slope.
[0020] Preferably, a conical head is provided at one end of the soil nail body, the conical head is fixed to the end surface of the soil nail body close to the foundation pit slope, and the conical head can be inserted into the foundation pit slope.
[0021] By adopting the above technical solution, the soil nail body can be easily inserted into the grouting hole through the conical head. The design of the conical head makes it easier to insert the soil nail body into the grouting hole. Since its shape is similar to a cone, when pushed by external force, it can more easily penetrate the soil and grouting materials, reducing resistance and friction during the insertion process.
[0022] Preferably, in order to shield the grouting holes after grouting, prevent the concrete inside the grouting holes from flowing out, and avoid affecting the molding quality of the concrete inside the grouting holes in the later stage, a sleeve is installed on the outside of the soil nail body away from the end of the conical head, and a grouting plug is installed on the side of the sleeve, and the grouting plug has the same diameter as the grouting hole.
[0023] By adopting the above technical solution, the grouting holes after grouting can be shielded. After the grouting inside the grouting holes is completed, the casing and the grouting plug can be moved to the grouting port of the grouting holes to prevent the concrete inside the grouting holes from flowing out, thereby avoiding affecting the molding quality of the concrete inside the grouting holes in the later stage.
[0024] On the other hand, the present application also provides a method for constructing soil nails in a reserved earthwork area of a foundation pit according to the above, comprising the following steps: S1: Pre-buried temporary support rods within a certain range above the reserved earthwork, the temporary support rods are made of steel pipes, and the length is adjusted according to the height of the reserved earthwork; S2: While carrying out normal foundation pit excavation, the standard soil nailing arrangement in the surrounding area of the reserved earthwork is completed simultaneously; S3: When the predetermined elevation is reached, a lightweight filling layer is used to replace the original soil to fill the top of the temporary support rod to ensure that the pressure is evenly distributed in the entire area and prevent local settlement. Subsequently, microwave curing technology is used to quickly enhance the bearing capacity of the filling material to ensure that it can withstand the pressure of the upper soil in a short period of time; S4: Gradually remove the reserved soil and immediately install the permanent soil nail body, and at the same time carry out the mesh spraying and surface protection operation until the entire reserved area is fully supported.
[0025] By adopting the above technical solution, the reserved earthwork area is stabilized by preset temporary support rods, and the lightweight filling layer is used to replace the original soil, thereby reducing the amount of subsequent excavation and accelerating the construction process. The use of microwave curing technology can greatly improve the mechanical properties of the lightweight filling layer in a short period of time, ensuring safety and stability during construction. In the final cleaning stage of the reserved earthwork, the installation of the permanent soil nail body is immediately followed up to maintain the continuity and integrity of the overall support of the foundation pit.
[0026] The beneficial effects of the present invention are as follows: the soil nails and construction method for the reserved earthwork area of the foundation pit described in the present invention, through the coordinated use of the foundation pit slope, reserved earthwork, lightweight filling layer, support rods and soil nail bodies, by using lightweight filling materials to replace the original soil, reducing the later excavation volume, accelerating the construction process, greatly shortening the overall period of soil nail construction in the reserved earthwork area of the foundation pit, improving the comprehensive benefits of the project, effectively solving the problem of low excavation efficiency in the reserved earthwork area, and reducing unnecessary waste of resources; by adopting microwave curing technology, the mechanical properties of lightweight filling materials can be greatly improved in a short time, and the safety and reliability of the construction process are improved. At the same time, by introducing temporary support system support rods, the slope instability caused by premature unloading can be avoided. Through the above measures, not only the construction time can be significantly shortened, but also the construction risk can be greatly reduced and the project quality can be improved.
[0027] The soil nails and construction method for the reserved earthwork area of a foundation pit described in the present invention are used in combination with a connecting sleeve, a reinforcement ring, a reinforcement nail, a pushing structure, a rotating rod and a pushing block. A worker rotates the rotating rod, which drives the outer pushing block to rotate. The pushing block applies a thrust to one end of the reinforcement nail, and the other end of the reinforcement nail can be inserted into the foundation pit slope. By inserting the reinforcement nail into the foundation pit slope, the soil nail body reinforces the foundation pit slope, and at the same time, the stability of the soil nail body can be improved to prevent the soil nail body from moving.
[0028] The soil nails and construction method for a reserved earthwork area of a foundation pit described in the present invention are used in combination with a rotating rod and a reinforcing plate. One end of the reinforcing plate with an arc surface is attached to the inner wall of a soil nail body. The reinforcing plate is driven to rotate by the rotating rod, so that the reinforcing plate can process the interior of the soil nail body that has not been grouted, thereby preventing foreign matter from blocking the grouting holes inside the soil nail body. At the same time, the soil nail body can be reinforced by the reinforcing plate, thereby improving the support of the soil nail body to the foundation pit slope. BRIEF DESCRIPTION OF THE DRAWINGS
[0029] Figure 1 is a stereogram of an embodiment of the present invention; Figure 2 It is a schematic diagram of the internal structure of the reserved earthwork part in the present invention; Figure 3 It is a schematic diagram of the internal structure of the foundation pit slope part in the present invention; Figure 4 It is a structural schematic diagram of the soil nail body in the present invention; Figure 5 It is a structural schematic diagram of the reinforcement mechanism in the present invention; Figure 6 It is a structural schematic diagram of the reinforcement plate in the present invention.
[0030] Description of reference numerals: 1. Foundation pit slope; 101. Grouting hole; 2. Reserved earthwork; 201. Lightweight filling layer; 3. Support rod; 4. Soil nail body; 401. Grouting hole; 402. Conical head; 403. Casing; 404. Grouting plug; 5. Reinforcement mechanism; 501. Connecting sleeve; 502. Reinforcement ring; 503. Reinforcement nail; 504. Pushing structure; 5041. Rotating rod; 5042. Pushing block; 6. Limiting rod; 7. Reinforcement plate. DETAILED DESCRIPTION
[0031] The subject matter described herein will now be discussed with reference to example embodiments. It should be understood that the discussion of these embodiments is only to enable those skilled in the art to better understand and implement the subject matter described herein, and the functions and arrangements of the elements discussed may be changed without departing from the scope of protection of the contents of this specification. Each example may omit, replace or add various processes or components as needed. In addition, the features described relative to some examples may also be combined in other examples. Example
[0032] The following is a further detailed description of the technical solution of the present invention in conjunction with the accompanying drawings and specific embodiments. Figures 1 to 6 , this application provides a soil nail for the reserved earthwork area of the foundation pit, please refer to Figure 1 , Figure 2 and Figure 3 , including a foundation pit slope 1, reserved earthwork 2 and a soil nail body 4; a reserved earthwork 2 is provided on the side of the foundation pit slope 1, and a support rod 3 is installed inside the reserved earthwork 2. The temporary support rod 3 uses a galvanized steel pipe with a diameter of 48mm and a wall thickness of 3.5mm, which has good corrosion resistance and sufficient rigidity. A lightweight filling layer 201 is provided on the surface of the reserved earthwork 2 and the support rod 3. The microwave curing technology is used to enhance the bearing capacity of the lightweight filling layer 201. The frequency of microwave curing is set at 915MHz, and the power range is 6kW-12kW to meet the curing requirements of fillers of different volumes. A grouting hole 101 is penetrated inside the foundation pit slope 1 and the reserved earthwork 2, and a soil nail body 4 is installed inside the grouting hole 101. One end of the soil nail body 4 that passes through the grouting hole 101 is connected and opened, and a reinforcement mechanism 5 is installed at the middle position of the soil nail body 4.
[0033] Please refer to Figure 1 , Figure 2 and Figure 3 The support rod 3 is a steel pipe, and the lightweight filling layer 201 is a foam plastic.
[0034] Specifically, the workers determine the position of the temporary support rod 3, use a drilling machine to drill holes, pre-embed the temporary support rod 3 within a certain range above the reserved earthwork 2, insert the prefabricated support rod 3 into the hole, and fix it with an anchor to ensure a firm connection. By introducing the temporary support system support rod 3, the slope instability caused by premature unloading is avoided. While carrying out normal foundation pit excavation, the standard soil nail arrangement in the surrounding area of the reserved earthwork 2 is completed simultaneously. When the predetermined elevation is reached, a lightweight filling layer 201 is used to fill it to the top of the temporary support rod 3. By using lightweight filling materials to replace the in-situ soil, the amount of later excavation is reduced, the construction process is accelerated, the overall period of soil nail construction in the reserved earthwork part of the foundation pit is greatly shortened, and the overall project efficiency is improved. The benefits are achieved through the combined use of the above methods, which effectively solves the problem of low excavation efficiency in the reserved earthwork area, reduces unnecessary waste of resources, and ensures that the pressure in the entire area is evenly distributed. Subsequently, the external microwave generator is started, and the microwave curing technology is used to heat the lightweight filling layer 201 to enhance the bearing capacity of the lightweight filling layer 201. The microwave curing technology can greatly improve the mechanical properties of the lightweight filling material in a short time, thereby improving the safety and reliability of the construction process. The reserved earthwork 2 is then removed in turn, and the soil nail body 4 is then placed inside the grouting hole 101 at the corresponding position, and the mesh spraying surface protection operation is carried out at the same time until the entire reserved area is fully supported. The reinforcement mechanism 5 is used to improve the reinforcement of the soil nail body 4 to the foundation pit.
[0035] Please refer to Figure 5 and Figure 6 The reinforcement mechanism 5 includes a connecting sleeve 501, a reinforcement ring 502, a reinforcement nail 503 and a pushing structure 504. The connecting sleeve 501 is threadedly installed at the middle position of the soil nail body 4, the reinforcement ring 502 is installed on the inner wall of the connecting sleeve 501, the reinforcement nail 503 is movably installed inside the connecting sleeve 501 and the reinforcement ring 502, and the pushing structure 504 is installed through the inside of the soil nail body 4.
[0036] Please refer to Figure 5 and Figure 6 The pushing structure 504 includes a rotating rod 5041 and a pushing block 5042. The two sides of the pushing block 5042 are arc-shaped. The rotating rod 5041 is rotatably installed at the internal position of the soil nail body 4. The pushing block 5042 is installed on the outer surface of the rotating rod 5041 near the reinforcement ring 502. The interior of the soil nail body 4 is hollow. One end of the rotating rod 5041 is rotatably connected to the interior of the soil nail body 4 near the conical head 402. The worker can rotate the rotating rod 5041 from the other end of the soil nail body 4.
[0037] Specifically, in order to improve the reinforcement of the soil nail body 4 to the foundation pit slope 1, the reinforcement nail 503 is moved to the inside of the connecting sleeve 501 and the reinforcement ring 502, and the end of the reinforcement nail 503 close to the reinforcement ring 502 is an arc surface. The worker assembles the reinforcement mechanism 5 and the soil nail body 4 through a thread, and then puts the soil nail body 4 into the grouting hole 101. At this time, the worker rotates the rotating rod 5041 inside the soil nail body 4, and the rotating rod 5041 drives the outer pushing block 5042 to rotate. The pushing block 5042 applies a thrust to one end of the reinforcement nail 503, and the other end of the reinforcement nail 503 can be inserted into the foundation pit slope 1. Then, the soil nail body 4 can further reinforce the foundation pit slope 1, and at the same time, the stability of the soil nail body 4 can be improved.
[0038] Please refer to Figure 5 and Figure 6 The outer surface of the rotating rod 5041 is equidistantly provided with reinforcing plates 7, and one end of the reinforcing plates 7 close to the inner wall of the soil nail body 4 is in an arc surface.
[0039] Specifically, in order to reinforce the soil nail body 4 and improve the supporting capacity of the soil nail body 4 to the foundation pit slope 1, one end of the reinforcing plate 7 with an arc surface is attached to the inner wall of the soil nail body 4. The soil nail body 4 can be reinforced by the reinforcing plate 7, thereby improving the supporting capacity of the soil nail body 4 to the foundation pit slope 1.
[0040] Please refer to Figure 5 and Figure 6 Two groups of limiting rods 6 are symmetrically installed on the outer surface of the connecting sleeve 501 , and the limiting rods 6 are equidistantly distributed on the outer surface of the connecting sleeve 501 circumferentially.
[0041] Specifically, in order to make the soil nail body 4 centered inside the grouting hole 101, when the soil nail body 4 is located inside the grouting hole 101, because the outer surface of the limit rod 6 is an arc surface and multiple groups of limit rods 6 are equidistantly distributed, the soil nail body 4 can be centered inside the grouting hole 101, avoiding the position of the soil nail body 4 from being offset and one side contacting the inner wall of the grouting hole 101, which affects the later grouting.
[0042] Please refer to Figure 3 and Figure 4 A plurality of grouting holes 401 are arranged inside the soil nail body 4, and the grouting holes 401 are distributed inside the soil nail body 4 at equal distances.
[0043] Please refer to Figure 3 and Figure 4 A conical head 402 is provided at one end of the soil nail body 4. The conical head 402 is fixed on the end surface of the soil nail body 4 close to the foundation pit slope 1, and the conical head 402 can be inserted into the foundation pit slope 1.
[0044] Specifically, in order to achieve the fixed installation of the soil nail body 4, the soil nail body 4 can be easily inserted into the grouting hole 101 through the conical head 402, and then concrete is poured into the soil nail body 4. The concrete will be poured from the inside of the soil nail body 4 to the inside of the grouting hole 101 through the grouting hole 401. Finally, the concrete solidifies and fixes the soil nail body 4 inside the foundation pit slope 1, so that the soil nail body 4 supports the foundation pit slope 1.
[0045] Please refer to Figure 3 and Figure 4 A sleeve 403 is installed on the outer side of one end of the soil nail body 4 away from the conical head 402 , and a grouting plug 404 is installed on the side of the sleeve 403 . The grouting plug 404 has the same diameter as the grouting hole 101 .
[0046] Specifically, in order to shield the grouting hole 101 after grouting, after the grouting inside the grouting hole 101 is completed, the sleeve 403 and the grouting plug 404 are moved to the grouting port of the grouting hole 101 to prevent the concrete inside the grouting hole 101 from flowing out, thereby avoiding affecting the molding quality of the concrete inside the grouting hole 101 in the later stage.
[0047] On the other hand, the embodiment of the present application also provides a method for constructing soil nails in a reserved earthwork area of a foundation pit according to the above, comprising the following steps: S1: Determine the position of the temporary support rod 3 according to the design drawing, use a drilling machine to drill a hole with a depth exceeding the expected maximum settlement value of 50 cm, and bury the temporary support rod 3 within a certain range above the reserved earthwork 2. The length of the temporary support rod 3 is adjusted according to the height of the reserved earthwork 2. Insert the prefabricated support rod 3 into the hole and fix it with an anchor to ensure a firm connection; S2: While carrying out normal foundation pit excavation, the standard soil nailing arrangement in the surrounding area of reserved earthwork 2 is completed simultaneously; S3: When the predetermined elevation is reached, a lightweight filling layer 201 is used to replace the original soil to fill the top of the temporary support rod 3 to ensure that the pressure in the entire area is evenly distributed to prevent local settlement. Subsequently, the external microwave generator is started to heat the lightweight filling layer 201 according to the set parameters for 10 minutes. The microwave curing technology is used to quickly enhance the bearing capacity of the lightweight filling layer 201 to ensure that it can withstand the pressure of the upper soil in a short period of time; S4: Remove the reserved earthwork 2 in sequence, with the thickness of each stripping not exceeding 50 cm, and then place the soil nail body 4 at the corresponding position, and carry out the mesh spraying and surface protection operation at the same time until the entire reserved area is fully supported.
[0048] Working principle: In the early stage of construction, the reserved earthwork 2 area is stabilized by the preset temporary support rods 3. In the normal foundation pit excavation process, the soil nails around the reserved earthwork 2 are arranged first to build a preliminary protection system; the lightweight filling layer 201 is used to replace the original soil, which reduces the amount of later excavation and accelerates the construction process; the use of microwave curing technology can greatly improve the mechanical properties of the lightweight filling layer 201 in a short time, ensuring safety and stability during construction; in the final cleaning stage of the reserved earthwork 2, the installation of the permanent soil nail body 4 is immediately followed up to maintain the continuity and integrity of the overall support of the foundation pit.
[0049] An example of the present specific implementation mode is described above, but the present embodiment is not limited to the above-mentioned specific implementation mode, which is merely illustrative and not restrictive. A person skilled in the art may make many forms inspired by the present embodiment, all of which are protected by the present embodiment.
Claims
1. A soil nail for a reserved earthwork portion of a foundation pit, comprising a foundation pit slope (1), reserved earthwork (2) and a soil nail body (4); characterized in that: A reserved earthwork (2) is provided on the side of the foundation pit slope (1), a support rod (3) is installed inside the reserved earthwork (2), a lightweight filling layer (201) is provided on the surface of the reserved earthwork (2) and the support rod (3), grouting holes (101) are provided through the inside of the foundation pit slope (1) and the reserved earthwork (2), a soil nail body (4) is installed inside the grouting hole (101), and a reinforcement mechanism (5) is installed at the middle position of the soil nail body (4).
2. The soil nail for reserved earthwork area of foundation pit according to claim 1, characterized in that: The support rod (3) is a steel pipe, and the lightweight filling layer (201) is foam plastic.
3. The soil nail for reserved earthwork area of foundation pit according to claim 1, characterized in that: The reinforcement mechanism (5) comprises a connecting sleeve (501), a reinforcement ring (502), a reinforcement nail (503) and a pushing structure (504); the connecting sleeve (501) is threadedly installed at the middle position of the soil nail body (4); the reinforcement ring (502) is installed on the inner wall of the connecting sleeve (501); the reinforcement nail (503) is movably installed inside the connecting sleeve (501) and the reinforcement ring (502); and the pushing structure (504) is installed through the inside of the soil nail body (4).
4. The soil nail for reserved earthwork area of foundation pit according to claim 3, characterized in that: The pushing structure (504) comprises a rotating rod (5041) and a pushing block (5042); the rotating rod (5041) is rotatably mounted at an inner position of the soil nail body (4); and the pushing block (5042) is mounted on the outer surface of the rotating rod (5041) close to the reinforcement ring (502).
5. The soil nail for reserved earthwork area of foundation pit according to claim 4, characterized in that: Reinforcement plates (7) are equidistantly mounted on the outer surface of the rotating rod (5041); one end of the reinforcement plate (7) close to the inner wall of the soil nail body (4) is in the form of an arc surface.
6. The soil nail for reserved earthwork area of foundation pit according to claim 3, characterized in that: Two groups of limit rods (6) are symmetrically mounted on the outer surface of the connecting sleeve (501), and the limit rods (6) are equidistantly distributed on the outer surface of the connecting sleeve (501) at a circumference.
7. The soil nail for reserved earthwork area of foundation pit according to claim 1, characterized in that: A plurality of groups of grouting holes (401) are provided inside the soil nail body (4), and the grouting holes (401) are distributed at equal distances inside the soil nail body (4).
8. The soil nail for reserved earthwork area of foundation pit according to claim 1, characterized in that: A conical head (402) is provided at one end of the soil nail body (4); the conical head (402) is fixed to the end surface of the soil nail body (4) close to the foundation pit slope (1), and the conical head (402) can be inserted into the foundation pit slope (1).
9. The soil nail for reserved earthwork area of foundation pit according to claim 1, characterized in that: A sleeve (403) is installed on the outer side of one end of the soil nail body (4) away from the conical head (402), and a grouting plug (404) is installed on the side of the sleeve (403). The grouting plug (404) has the same diameter as the grouting hole (101).
10. A method for constructing soil nails in a reserved earthwork area of a foundation pit according to any one of claims 1 to 9, characterized in that: The following steps are involved: S1: pre-burying a temporary support rod (3) within a certain range above the reserved earthwork (2), wherein the temporary support rod (3) is made of a steel pipe, and the length of the temporary support rod (3) is adjusted according to the height of the reserved earthwork (2); S2: While carrying out normal foundation pit excavation, the standard soil nailing arrangement in the surrounding area of the reserved earthwork (2) is completed simultaneously; S3: When the predetermined elevation is reached, a lightweight filling layer (201) is used to replace the original soil and fill the top of the temporary support rod (3) to ensure that the pressure in the entire area is evenly distributed and prevent local settlement. Subsequently, microwave curing technology is used to quickly enhance the bearing capacity of the filling material to ensure that it can withstand the pressure of the soil above in a short period of time; S4: gradually remove the reserved earthwork (2) and immediately install the permanent soil nail body (4), while performing mesh spraying and surface protection operations until the entire reserved area is fully supported.