A construction method for permanent and temporary combined prestressed anchor structure

Abstract

The present invention provides a method for constructing a permanent and temporary prestressed anchor structure, which adopts a prestressed anchor combination structure and is provided with multiple anchor sections. The construction method includes two stages: foundation pit slope construction and lining structure construction. In the foundation pit slope construction stage, the prestressed anchor structure is tensioned for the first time and temporarily anchored without grouting; in the lining structure construction stage, the prestressed anchor is extended using a connector, and the anchor structure is tensioned for the second time, and anchoring, grouting and sealing are completed. The present invention can reduce the number of anchor projects, reduce construction difficulty and safety risks, ensure the stability and safety of the lining structure, reduce rock fragmentation and collapse, and slope disturbance problems; ensure that the anchor structure and concrete are integrated into a complete whole, reduce tensioning prestress loss, ensure that the grouting is full and dense, ensure construction quality, and reduce project costs.

Description

Technical Field

[0001] The present invention relates to the technical field of foundation pit slope support, and in particular to a construction method of a permanent and temporary combined prestressed anchor rod structure. Background Art

[0002] Generally, the prestressed anchor structure consists of three parts: the anchor head, the free section and the anchoring section. The anchoring force generated by the anchor head applies a certain prestress to the surrounding rock, actively reinforcing the surrounding rock. This is a method of reinforcement and support commonly used in the construction of slopes, deep rock and soil foundation pits and other projects.

[0003] The building structure uses prestressed anchor-type lining walls, but the foundation pit is different. During the excavation process, temporary support is required for the foundation pit slope to ensure construction safety. If prestressed anchor rods are used for reinforcement, the project will be large in number, the construction will be difficult, the construction period will be long, and the project cost will be high. The design adopts a prestressed anchor-type lining wall structure. Generally, the foundation pit slope is preferably 65° or above, and the rock mass is relatively broken to reduce the amount of concrete filling behind the lining wall. Based on the general prestressed anchor rod structure, it is of great significance to study a new prestressed anchor rod combination structure according to the application characteristics and needs.

[0004] The Chinese patent application number is CN 202023170563.5, which discloses a steel pipe pile anchor cable combined support structure, in which the anchor cable includes a free section and an anchoring section, the steel pipe pile wraps the free section of the anchor cable, the top of the free section of the anchor cable and the top of the steel pipe pile are fixed by a fixed platform, and a grouting pipe is provided in the fixed platform for grouting. It has a multi-section anchor cable structure, but there are the following problems: the free section of the anchor cable wrapped by the steel pipe pile is not pulled out, and if there is no special sliding damage design requirement for the slope, the cost of the anchor cable project is still increased. At the same time, when grouting the anchoring section, it is possible to enter the grouting through several grouting holes provided in the steel pipe pile, affecting the length of the free section; when the anchor cable is tensioned and locked, the steel plate is not provided with a grouting exhaust hole, which affects the fullness and density of the grouting and makes it difficult to guarantee the quality. Summary of the Invention

[0005] The present invention aims to address the technical problems of the prior art by providing a method for constructing a permanent and temporary prestressed anchor structure. This method employs a prestressed anchor structure with multiple anchor sections. Through a two-stage prestressing control construction method, this method achieves both permanent and temporary reinforcement of foundation pit slope support and lining wall anchoring.

[0006] In order to solve the above technical problems, the technical solution adopted by the present invention is:

[0007] A construction method for a permanent and temporary combined prestressed anchor structure is provided, wherein a multi-section anchor structure is provided, including an anchoring section, a first free section, a first anchor head, a second free section, and a second anchor head. The construction method includes:

[0008] S1: Construction of foundation pit slope: excavate the foundation pit layer by layer from top to bottom, construct the prestressed anchor structure layer by layer, tension the anchor head and anchor rod, temporarily anchor, do not grouting, and complete the mesh spraying or protective netting of the slope layer;

[0009] S2: Lining structure construction; after the foundation pit is excavated to the bottom layer, the lining structure is poured layer by layer from bottom to top, and the filling concrete pouring is completed in time. The prestressed anchor structure is extended layer by layer, the second anchor tensioning is carried out, and the anchoring, grouting and anchor sealing are completed.

[0010] The step S1 specifically includes the following steps:

[0011] S11: Anchor hole drilling: Excavation of the foundation pit is stopped when the prestressed anchor structure is below the design elevation of 0.5m. The coordinate positions of the anchor holes in each anchoring section and free section are measured. The holes are drilled and cleaned.

[0012] S12: Anchor rod fabrication and installation, anchor hole grouting; the anchor rod of the free section 1 is sheathed with a smooth round plastic tube, isolated from the anchor section, and sealed with engineering tape; the fabricated anchor rod is placed in the anchor hole, and the bottom of the hole is grouting is performed in time before the construction of the reinforced concrete foundation. The slurry is injected through the grouting pipe at the bottom of the hole, and the air is discharged through the anchor rod grouting exhaust pipe. The anchor section and the anchor holes outside the free section 1 are grouted fully and densely.

[0013] S13: Construction of the anchor head structure; first, tie the reinforced concrete base steel bars, leaving space for connecting the slope mesh and shotcrete reinforcement mesh; accurately position the anchor head embedded pad, connect the grouting pipe on the pad to the bottom of the round plastic pipe, and connect the slurry return exhaust pipe to the top of the round plastic pipe; pour the reinforced concrete base concrete, and make sure the reinforced concrete base is in close contact with the foundation pit slope;

[0014] S14: Tensioning and temporary anchoring of anchor head, free section and anchor rod; after the strength of the anchoring section and reinforced concrete base meets the requirements, tensioning of anchor head, free section and anchor rod is carried out and temporarily locked with anchor device; during the construction process, the anchor rod and anchor device are well protected, and the stress of the anchor rod is monitored. If there is any loss, re-tensioning is carried out in time.

[0015] In the step S14, after the anchor head-free section-prestressing is tensioned, temporary anchoring is performed without grouting.

[0016] The step S2 specifically includes the following steps:

[0017] S21: Lining structure reinforcement construction; complete lining structure reinforcement binding according to the design drawings;

[0018] S22: Construction of the second anchor rod in the free section; use a connector to connect the rod body at one end of the anchor head, install the second anchor head pad, connect the grouting pipe and install the corrugated steel pipe, seal the ends of the corrugated steel pipe with the pad, and ensure that the grouting exhaust pipe on the second anchor head pad is connected to the top of the corrugated steel pipe;

[0019] S23: Lining structure concrete construction; after the hidden steel bar and anchor bolt works are accepted, the lining structure concrete is poured by formwork;

[0020] S24: Concrete filling construction; after the concrete strength of the lining structure meets the requirements, the anchor head two anchor rods are pre-tensioned and temporarily locked with the anchor head two upper anchors, and the concrete filling behind the wall is started. The horizontal displacement of the lining structure is observed and the anchor rod pre-tension is adjusted in time;

[0021] S25: tensioning, anchoring, and grouting the second anchor rod of the second free section of the anchor head; after the strength of the filled concrete meets the requirements, tensioning and anchoring the second anchor rod of the second free section of the anchor head; pouring cement slurry through the second grouting pipe of the anchor head until the slurry concentration discharged from the second slurry return exhaust pipe of the anchor head is the same as the grouting concentration;

[0022] S26: The anchor head is sealed with two anchor rods; the outer anchor head of the lining structure is sealed with a concrete anchor body.

[0023] In the step S25, when the free segment 2 is tensioned, the total length of the free segment 2 and the free segment 1 is not less than 5m, thereby reducing the loss of prestress caused by the tensioning of the anchor head 2.

[0024] In the step S25, after the free section 2 of the anchor head is prestressed and anchored, the free section 1 and the free section 2 are grouted together, and the smooth round plastic pipe of the free section 1 and the corrugated steel pipe of the free section 2 are connected through the grouting pipe and the return grouting exhaust pipe to ensure that the grouting is full and dense.

[0025] The free section 2 is sealed with a corrugated steel pipe, which has a strong bond strength with the concrete, ensuring that the anchor rod structure and the concrete are integrated into a complete whole.

[0026] In the step S24, the filling concrete is constructed layer by layer along with the lining structure, and the lining structure is ensured to be stable and safe by pre-tensioning and timely adjustment of the pre-tensioning force.

[0027] The anchor rod structure construction method is suitable for designing a prestressed anchor lining wall structure to carry out permanent and temporary reinforcement of the foundation pit slope support and lining wall anchoring. In order to reduce the amount of concrete filling behind the lining wall, the foundation pit slope is 65° or above, the rock mass is relatively broken, and the surrounding rock integrity coefficient Kv value is greater than 0.35.

[0028] A permanent and temporary combined prestressed anchor rod structure, comprising a multi-section anchor rod structure, wherein the multi-section anchor rod structure is, from bottom to top, an anchoring section, a free section 1, an anchor head 1, a free section 2, and an anchor head 2;

[0029] The anchoring section is an anchoring body used to transfer the tension of the slope support and lining structure to the surrounding strata. The anchoring body is formed by bonding the anchor rod body and the rock and soil together with cement paste or cement mortar.

[0030] The free section 1 includes an anchor rod body located between the anchor section and the anchor head 1. The outer side of the anchor rod body is connected to a smooth round plastic tube sealed with the anchor section. The upper end is connected to the anchor rod body of the free section 2 through a connector. The length of the free section 1 is not less than 5m.

[0031] The smooth round plastic tube and the anchoring section are sealed by wrapping engineering tape around the outside.

[0032] The anchor head is used to transfer the tension from the anchor body to the foundation pit slope, and includes a reinforced concrete base, a pad and an anchor. The reinforced concrete base is connected to the slope hanging mesh spraying or protective net to form a temporary support structure for the foundation pit slope. The pad is connected to the grouting pipe and the return slurry exhaust pipe. The grouting pipe is connected to the bottom of the smooth round plastic pipe, and the return slurry exhaust pipe is connected to the top inside the smooth round plastic pipe.

[0033] The free section two includes an anchor rod body located between the anchor head one and the anchor head two, a corrugated steel pipe is sleeved on the outside of the anchor rod body, both ends of the corrugated steel pipe are sealed and connected to the pads of the two anchor heads, and the lower end of the anchor rod body is connected to the anchor rod body of the free section one through a connector. The length of the free section two is determined according to the anchor rod structure position, slope angle and lining structure thickness, and the total length of the free section two and the free section one accounts for 1 / 3 to 1 / 2 of the total length of the anchor rod body.

[0034] The second anchor head is used to transfer the tension from the rod body to the lining structure, and includes a pad, an anchor and a sealing anchor body. The pad is pre-buried in the lining structure. The grouting pipe and the return slurry exhaust pipe are connected to the pad. The grouting pipe is connected to the bottom of the corrugated steel pipe and is connected and passed through the grouting pipe on the anchor head pad. The return slurry exhaust pipe is connected to the top of the inner part of the corrugated steel pipe. The sealing anchor body is connected to the lining structure as a whole to seal the anchor.

[0035] By adopting the construction method of the present invention, the permanent and temporary combined reinforcement effects of foundation pit slope support and lining wall anchoring can be achieved, thereby reducing the number of anchor rod projects; foundation pit excavation and anchor rod structure are constructed in layers from top to bottom, and lining structure and anchor rod extension are constructed in layers from bottom to top, thereby reducing construction difficulty and safety risks; filling concrete construction is convenient, and the stability and safety of the lining structure are guaranteed by pre-tensioning and timely adjustment of the pre-tensioning force. At the same time, the first free section is sealed with a smooth round plastic tube to isolate it from the anchor section. Grouting is performed at the bottom of the hole immediately before the foundation concrete is constructed. The anchor section and the outer sides of the first free section are filled with grout, minimizing rock fragmentation, collapse, and slope disturbance. The second free section is sealed with a corrugated steel tube, which provides a strong bond with the concrete, ensuring that the anchor structure and concrete are integrated into a single piece. The second and first free sections of the anchor structure are grouted simultaneously, ensuring that when the second anchor head is tensioned, the total length of the free section is no less than 5m, minimizing prestress loss. The first free section's smooth round plastic tube is connected to the second free section's corrugated steel tube via a grouting pipe and a grouting return exhaust pipe to ensure full and dense grouting and guarantee construction quality. Overall, the adoption of this Yonglin-integrated prestressed anchor structure construction method has accelerated project progress, ensured project quality and safety, and reduced project costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 It is a cross-sectional schematic diagram of the implementation effect of the permanent and temporary combined prestressed anchor rod structure of the present invention.

[0037] Figure 2 It is a schematic diagram of the prestressed anchor rod structure of the present invention. DETAILED DESCRIPTION

[0038] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0039] Example 1

[0040] like Figure 1 、 Figure 2 As shown, the cross section of the permanent and temporary combined prestressed anchor structure of the present invention includes a prestressed anchor structure 1, a foundation pit slope 2, a lining structure 3, and a filling concrete 4. The prestressed anchor structure 1 includes a multi-segment anchor structure, which, from bottom to top, comprises an anchoring segment 1-1, a free segment 1-2, an anchor head 1-3, a free segment 2 1-4, and an anchor head 2 1-5.

[0041] The anchoring section 1 - 1 is an anchoring body used to transmit the tension of the slope support and lining structure 3 to the surrounding strata. The anchoring body is formed by bonding the anchor rod body 5 to the rock and soil with cement paste or cement mortar.

[0042] The free section 1-2 includes an anchor rod body 5 located between the anchor section 1-1 and the anchor head 1-3. The outer side of the anchor rod body 5 is sleeved with a smooth round plastic tube 9 sealed with the anchor section 1-1, and the upper end is connected to the anchor rod body 5 of the free section 2 1-4 through a connector 6. The length of the free section 1-2 is not less than 5m.

[0043] The smooth round plastic tube 9 and the anchoring section 1 - 1 are sealed by wrapping engineering tape around them.

[0044] The anchor head 1-3 is used to transfer the tension from the anchor rod body 5 to the foundation pit slope 2, and includes a reinforced concrete base 13, a pad 7 and an anchor 8. The reinforced concrete base 13 is connected to the slope hanging mesh spraying or protective net to form a temporary support structure for the foundation pit slope. The pad 7 is connected to a grouting pipe 11 and a return slurry exhaust pipe 12. The grouting pipe 11 is connected to the bottom of the smooth round plastic pipe 9, and the return slurry exhaust pipe 12 is connected to the top of the inside of the smooth round plastic pipe 9.

[0045] The free section 2 1-4 includes an anchor rod body 5 located between the anchor head 1-3 and the anchor head 2 1-5. The outer side of the anchor rod body 5 is sleeved with a corrugated steel pipe 10. Both ends of the corrugated steel pipe 10 are sealed with the pads 7 of the two anchor heads. The lower end of the anchor rod body 5 is connected to the anchor rod body 5 of the free section 1-2 through a connector 6. The length of the free section 2 1-4 is determined according to the position of the anchor rod structure 1, the slope angle and the thickness of the lining structure 3. The total length of the free section 2 1-4 and the free section 1-2 accounts for 1 / 3 to 1 / 2 of the total length of the anchor rod body 5.

[0046] The anchor head 2 1-5 is used to transfer the tension from the rod body to the lining structure 3, and includes a pad 7, an anchor 8 and a sealing anchor body 14. The pad 7 is pre-buried in the lining structure 3. The pad 7 is connected to a grouting pipe 11 and a return slurry exhaust pipe 12. The grouting pipe 11 is connected to the bottom of the corrugated steel pipe 10 and is connected to the grouting pipe 11 on the anchor head 1 1-3 pad 7. The return slurry exhaust pipe 12 is connected to the top of the inner part of the corrugated steel pipe 10. The sealing anchor body 14 is connected to the lining structure 3 as a whole to seal the anchor 8.

[0047] Example 2

[0048] like Figure 1 、 Figure 2 As shown, a construction method of a permanent and temporary combined prestressed anchor structure includes the following two stages:

[0049] S1: Construction of foundation pit slope 2. The foundation pit is excavated layer by layer from top to bottom, and the prestressed anchor structure 1 is constructed layer by layer. The first anchor tensioning and temporary anchoring are carried out without grouting. The slope mesh or protective net is then installed.

[0050] S2: Construction of lining structure 3. After the foundation pit is excavated to the bottom layer, the lining structure is poured layer by layer from bottom to top, and the filling concrete 4 is poured in a timely manner. The prestressed anchor structure 1 is extended layer by layer, and the second anchor tensioning is carried out. The anchoring, grouting, and anchor sealing are completed.

[0051] S1 specific construction method includes the following steps:

[0052] S11: Anchor hole drilling. Excavation is stopped when the foundation pit reaches a height below the design elevation of the prestressed anchor structure 1 by 0.5 m. The coordinates of the anchor holes in the anchoring section 1-1 and the free section 1-2 are measured. The holes are drilled and cleaned.

[0053] S12: Anchor bolt fabrication and installation, anchor hole grouting. The anchor bolt of the free section 1-2 is sheathed with a smooth round plastic tube 9 and sealed with engineering tape. The fabricated anchor bolt is placed in the anchor hole, grout is injected from the bottom of the hole, and air is expelled from the anchor bolt hole. The anchor holes outside the anchor section 1-1 and the free section 1-2 are grouted to ensure full and dense grouting.

[0054] S13: Construction of the Anchor Head 1-3 Structure. First, tie the reinforced concrete base 13, reserving space for connecting the steel bars for the slope mesh spraying. The anchor head 1-3 pre-embedded pad 7 is accurately positioned. The grouting pipe 11 on the pad 7 is connected to the bottom of the round plastic pipe 9, and the grouting exhaust pipe 12 is connected to the top of the round plastic pipe 9. Concrete is poured for the reinforced concrete base 13, ensuring that the reinforced concrete base 13 is in close contact with the foundation pit slope 2.

[0055] S14: Anchor head 1-3 anchor rod tensioning and temporary anchoring. After the anchor body and reinforced concrete base 13 meet the required strength, anchor head 1-3 anchor rod tensioning is performed and temporarily locked with anchor 8. During construction, the anchor rods and anchor 8 must be well protected, and the anchor rod stress must be monitored. If any damage occurs, re-tensioning is carried out promptly.

[0056] S2 specific construction method includes the following steps:

[0057] S21: Lining structure 3 reinforcement construction. Complete lining structure 3 reinforcement binding according to the design drawings.

[0058] S22: Free section 2 1-4 anchor bolt construction. Connect the anchor head 1-3 end rod 5 with the connector 6, install the anchor head 2 1-5 pad 7, connect the grouting pipe 11, and install the corrugated steel pipe 10. The ends of the corrugated steel pipe 10 are sealed with the pad 7. Ensure that the grouting exhaust pipe 12 on the anchor head 2 1-5 pad is connected to the top of the corrugated steel pipe 10.

[0059] S23: Lining Structure 3 Concrete Construction. After the hidden steel and anchor works are accepted, the lining structure 3 concrete is poured with formwork.

[0060] S24: Concrete filling 4. After the concrete strength of the lining structure 3 meets the requirements, the anchor rods 1-5 are pre-tensioned and temporarily locked with the anchor rod upper anchor 8. The concrete filling behind the wall begins. The horizontal displacement of the lining structure 3 is observed and the anchor rod pre-tension is adjusted in time.

[0061] S25: Tensioning, anchoring, and grouting anchor rods 1-5 of anchor head 2. After the concrete 4 meets the required strength, tensioning and anchoring anchor rods 1-5 of anchor head 2 are performed. Cement slurry is poured through the anchor head 2 grouting pipe 11 until the slurry concentration discharged from the anchor head 2 grouting exhaust pipe 12 is the same as the grouting concentration.

[0062] S26: Anchor head 2 1-5 anchor rods are used to seal the anchor. The outer anchor head of the lining structure 3 is sealed with a concrete anchor body 14.

[0063] In the steps S1 and S2, the foundation pit excavation and the prestressed anchor structure 1 are constructed in layers from top to bottom, and the lining structure 3 and the anchor extension are constructed in layers from bottom to top, which reduces the construction difficulty and safety risks.

[0064] The free section 1-2 is sealed with a smooth round plastic tube 9 and isolated from the anchoring section 1-1. The bottom of the hole is grouting carried out in time before the concrete construction of the reinforced concrete base 13. The outside of the anchoring section 1-1 and the free section 1-2 are filled with grouting to reduce the problems of rock crushing, collapse and slope disturbance.

[0065] After the anchor head 1-3 is prestressed, it is temporarily anchored without grouting. When the free section 2 1-4 is tensioned, the total length of the free section is guaranteed to be not less than 5m, reducing the prestress loss of the anchor head 2 1-5.

[0066] After the anchor head 1-5 is prestressed and anchored, the free section 1-2 and the free section 1-4 are grouted together. The free section 1-2 smooth round plastic pipe 9 and the free section 1-4 corrugated steel pipe 10 are connected through the grouting pipe 11 and the return slurry exhaust pipe 12 to ensure that the grouting is full and dense.

[0067] The free sections 1-4 are sealed with corrugated steel pipes 10, which have strong contact and bonding strength with the concrete, ensuring that the anchor structure 1 and the concrete are combined into a complete whole.

[0068] The filling concrete 4 is constructed layer by layer along with the lining structure 3, and the lining structure 3 is ensured to be stable and safe by pre-tensioning and timely adjusting the pre-tensioning force.

[0069] The described structure and construction method are suitable for designing a prestressed anchored lining wall structure to achieve a combination of permanent and temporary reinforcement for the foundation pit slope support and lining wall anchoring. To reduce the amount of concrete fill behind the lining wall, the foundation pit slope should ideally be 65° or higher, the rock mass should be relatively fragmented, and the surrounding rock integrity factor (Kv) should be greater than 0.35.

[0070] The above description is merely a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any person skilled in the art who, within the technical scope disclosed in the present invention, makes equivalent substitutions or modifications based on the technical solutions and inventive concepts of the present invention shall fall within the scope of protection of the present invention.

Claims

1. A construction method for a permanent and temporary combined prestressed anchor structure, characterized by: A multi-section anchor rod structure is provided, including an anchoring section, a first free section, a first anchor head, a second free section, and a second anchor head. The construction method includes: S1: Construction of foundation pit slope: excavation of foundation pit from top to bottom, construction of prestressed anchor structure in layers, anchor head and anchor bolt tensioning, temporary anchoring, no grouting, and completion of mesh spraying of the slope layer; specifically including the following steps: S11: Anchor hole drilling: Excavation of the foundation pit is stopped when the prestressed anchor structure is below the design elevation of 0.5m. The coordinate positions of the anchor holes in each anchoring section and free section are measured. The holes are drilled and cleaned. S12: Anchor rod fabrication and installation, anchor hole grouting; the anchor rod of the free section 1 is sheathed with a smooth round plastic tube, isolated from the anchor section, and sealed with engineering tape; the fabricated anchor rod is placed in the anchor hole, and the bottom of the hole is grouting is performed in time before the construction of the reinforced concrete foundation. The slurry is injected through the grouting pipe at the bottom of the hole, and the air is discharged through the anchor rod grouting exhaust pipe. The anchor section and the anchor holes outside the free section 1 are grouted fully and densely. S13: Construction of the anchor head structure; first, tie the reinforced concrete base steel bars, leaving space for connecting the slope mesh and shotcrete reinforcement mesh; accurately position the anchor head embedded pad, connect the grouting pipe on the pad to the bottom of the round plastic pipe, and connect the slurry return exhaust pipe to the top of the round plastic pipe; pour the reinforced concrete base concrete, and make sure the reinforced concrete base is in close contact with the foundation pit slope; S14: Tensioning and temporary anchoring of the anchor head, free section, and anchor rod; after the strength of the anchor section and reinforced concrete foundation meets the requirements, tensioning of the anchor head, free section, and anchor rod is carried out, and temporarily locked with an anchor tool without grouting; during the construction process, the anchor rod and anchor tool are well protected, and the anchor rod stress is monitored. If any loss occurs, re-tensioning is carried out in a timely manner; S2: Lining structure construction: After the foundation pit is excavated to the bottom layer, the lining structure is poured layer by layer from bottom to top, and the filling concrete is poured in time. The prestressed anchor structure is extended layer by layer, the second anchor tensioning is carried out, and the anchoring, grouting and anchor sealing are completed. The specific steps include the following: S21: Lining structure reinforcement construction; complete lining structure reinforcement binding according to the design drawings; S22: Construction of the second anchor rod in the free section; use a connector to connect the rod body at one end of the anchor head, install the second anchor head pad, connect the grouting pipe and install the corrugated steel pipe, seal the ends of the corrugated steel pipe with the pad, and ensure that the grouting exhaust pipe on the second anchor head pad is connected to the top of the corrugated steel pipe; S23: Lining structure concrete construction; after the hidden steel bar and anchor bolt works are accepted, the lining structure concrete is poured by formwork; S24: Concrete filling construction; after the concrete strength of the lining structure meets the requirements, the anchor head two anchor rods are pre-tensioned and temporarily locked with the anchor head two upper anchors, and the concrete filling behind the wall is started. The horizontal displacement of the lining structure is observed and the anchor rod pre-tension is adjusted in time; S25: tensioning, anchoring, and grouting the second anchor rod of the second free section of the anchor head; after the strength of the filled concrete meets the requirements, tensioning and anchoring the second anchor rod of the second free section of the anchor head; pouring cement slurry through the second grouting pipe of the anchor head until the slurry concentration discharged from the second grouting exhaust pipe of the anchor head is the same as the grouting concentration; after the second free section of the anchor head is prestressed and tensioned, grouting is performed on the first and second free sections simultaneously, and the smooth round plastic pipe of the first free section and the corrugated steel pipe of the second free section are connected and connected through the grouting pipe and the grouting exhaust pipe to ensure that the grouting is full and dense; S26: The anchor head is sealed with two anchor rods; the outer anchor head of the lining structure is sealed with a concrete anchor body.

2. The method for constructing a permanent and temporary prestressed anchor structure according to claim 1, characterized in that: In the step S25, when the free segment 2 is tensioned, the total length of the free segment 2 and the free segment 1 is not less than 5m, thereby reducing the loss of prestress caused by the tensioning of the anchor head 2.

3. The method for constructing a permanent and temporary prestressed anchor structure according to claim 1, characterized in that: The free section 2 is sealed with a corrugated steel pipe, which has a strong bond strength with the concrete, ensuring that the anchor rod structure and the concrete are integrated into a complete whole.

4. The method for constructing a permanent and temporary combined prestressed anchor structure according to claim 1, characterized in that: In the step S24, the filling concrete is constructed layer by layer along with the lining structure, and the lining structure is ensured to be stable and safe by pre-tensioning and timely adjustment of the pre-tensioning force.

5. A method for constructing a permanent and temporary combined prestressed anchor structure according to any one of claims 1 to 4, characterized in that: The anchor rod structure construction method is suitable for designing a prestressed anchor lining wall structure to carry out permanent and temporary reinforcement of the foundation pit slope support and lining wall anchoring. In order to reduce the amount of concrete filling behind the lining wall, the foundation pit slope is 65° or above, the rock mass is relatively broken, and the surrounding rock integrity coefficient Kv value is greater than 0.35.

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