High fill slope prestressed pipe anchor cable support construction method and structure

Abstract

The invention relates to the technical field of high-fill slope supporting, in particular to a high-fill slope prestressed pipe anchor cable supporting construction method which comprises the following steps: S1, earthwork backfilling and detection: backfilling earthwork to a pipe pile pre-embedded elevation in a layered manner, and detecting the compaction degree; s2, positioning pay-off and groove excavation: after positioning pay-off is carried out on the pipe pile, a pipe pile pre-buried groove is excavated; s3, pipe pile installation and component penetrating, wherein pipe pile hoisting in place and installation are completed in the groove, and a pre-stressed anchor cable and a grouting pipe penetrate into the pipe pile; s4, anchoring section concrete pouring and curing, wherein anchoring section encapsulating concrete is poured; s5, layered backfilling and process repeating: backfilling the next layer of earthwork to the elevation of the lower row of pipe piles, and repeating the steps S1 to S4; and S6, anchor cable grouting, tensioning and anchor sealing are conducted. The horizontal tension of a single anchor cable can be improved, so that the requirement for layered construction of backfill soil of the high fill slope is met, and the complex construction conditions that the slope is high, the slide-resistant piles and the anchor cables are overlong in size, and the backfill soil is thick are met.

Description

Technical Field

[0001] The present invention relates to the technical field of high fill slope support, in particular to a high fill slope prestressed pipe anchor cable support construction method and structure. Background Art

[0002] In current slope management projects in my country, three main types of slope support are commonly used: gravity retaining walls and reinforced retaining walls, pile-foundation buttress retaining walls, and prestressed anchor cable anti-slide pile retaining walls. Prestressed anchor cable anti-slide piles, a pile-anchor anti-slide system consisting of prestressed anchor cables and conventional anti-slide piles, offer significant technical and economic advantages. Once the strength of conventional anti-slide piles reaches a specific value, anchor cables are installed and fixed to stable rock formations via anchor holes. This system not only effectively increases anti-slide force but also significantly reduces the cross-sectional dimensions of the anti-slide piles, lowering concrete strength requirements, thereby significantly reducing project costs and saving engineering costs. Therefore, it is widely used in various slope management projects.

[0003] However, in actual engineering applications, when faced with steep slopes, the construction of anti-slide piles and anchor cables presents a series of special characteristics: the maximum length of the anti-slide pile construction can reach 38.8m, of which the maximum length of the above-ground pile is 17.8m, and the underground part is 21m; the backfill behind the anti-slide pile wall is thick, with the maximum backfill height reaching 21m; and the anchor cable length is as long as 45m. Under such engineering conditions, traditional prestressed anchor cable construction has exposed obvious shortcomings. Specifically, the horizontal tension of a single anchor cable is insufficient, making it difficult to meet the requirements of the project's backfill layered construction, and unable to adapt to the needs of such high-fill, large-scale slope management projects. Based on this, the traditional construction method was optimized to increase the horizontal tension of a single anchor cable, making it suitable for the requirements of backfill layered construction on high-fill slopes. This can better cope with complex engineering conditions such as high slope heights, extremely long anti-slide piles and anchor cables, and thick backfill, and solve the technical bottlenecks of traditional construction solutions in high-fill slope management. Summary of the Invention

[0004] In response to the technical problems existing in the background technology, the present invention provides a construction method and structure for prestressed pipe anchor support on high fill slopes, which can increase the horizontal tension of a single anchor cable to adapt to the layered construction requirements of backfill soil on high fill slopes, and cope with complex conditions such as high slopes, extra-long anti-slip piles and anchor cables, and thick backfill soil, breaking through the technical bottlenecks of traditional solutions in this type of management.

[0005] The technical implementation scheme of the present invention is:

[0006] A high fill slope prestressed pipe anchor cable support construction method comprises the following steps:

[0007] S1. Earthwork backfilling and testing: Backfill the earthwork in layers to the pre-buried elevation of the piles and test the compaction degree;

[0008] S2. Positioning and laying out the lines and excavating the trench: After positioning and laying out the pipe piles, excavate the pre-buried trench for the pipe piles;

[0009] S3. Installation of pipe piles and component threading: Complete the lifting and installation of pipe piles in the trench, insert the prestressed anchor cables and grouting pipes into the pipe piles, and insert the free ends of the prestressed anchor cables into the steel casing;

[0010] S4. Anchorage section concrete pouring and curing: pour the anchorage section encapsulation concrete and cure the concrete to the specified age;

[0011] S5, backfilling in layers and repeating the process: backfill the next layer of earthwork to the elevation of the next row of pipe piles, and repeat the above steps S1-S4;

[0012] S6. Anchor cable grouting, tensioning and anchor sealing: complete the prestressed anchor cable grouting, tensioning and anchor sealing operations.

[0013] Preferably, in step S2, the trench is excavated after the axis and position of the piles are determined according to the designed spacing, position and length of the test anchor cables.

[0014] Preferably, in step S3, the pipe piles are PHC500AB125-16 prestressed pipe piles, and steel strands are arranged inside the pipe piles; in step S3, the diameter of the steel casing is 168 mm, and the length of the steel casing inserted into the reserved steel pipe of the support pile is not less than 0.8 m.

[0015] Preferably, in step S3, when placing the pipe pile and the protective sleeve in the trench, an exhaust pipe is also inserted inside, and the exhaust pipe is arranged close to the top of the inner wall of the pipe pile; an 800×800mmC30 plain concrete pier is cast at the connection between the outer end of the pipe pile and the free end protective sleeve, and the bottom of the pipe pile is welded and sealed with a 25mm thick steel plate.

[0016] Preferably, in step S4, after the anchor cables are buried, the trench is backfilled with C20 concrete, and after the backfilled concrete has initially set, soil is continuously backfilled in layers until the designed height is reached.

[0017] Preferably, in steps S1 and S5, the earthwork layered backfilling meets the following requirements:

[0018] After the cubic compressive strength of the reaction wall concrete specimens cured under the same conditions reaches 27MPa, fill and compact the soil in layers to the designed top elevation of the piles of the support structure;

[0019] The backfill material is soil mixed with rock, with a soil-rock volume ratio of 7:3 and a maximum particle size of no more than 200mm. The moisture content of the on-site filler is controlled within the range of 1%-2%, and the compaction degree is no less than 94%;

[0020] During the backfilling process, expansive soil, silty soil, organic soil, and cultivated soil must not be used as fillers. The fillers must be compacted layer by layer, with a loose laying thickness of 200mm to 300mm.

[0021] The rolling times are 3 to 5 times, using a vibratory roller with operating parameters of a rolling speed of 2 to 4 km / h, an amplitude of 1.5 to 3 mm, and a compaction degree of 94%.

[0022] Preferably, in step S6, the anchor grouting pressure is 1.0Mpa to 2.0Mpa, the grouting amount is based on the concentrated slurry returned at the hole mouth, the grouting body uses ordinary Portland cement with a strength grade of 42.5 and a water-cement ratio of 0.38 to 0.55, and an additional triethanolamine early strength agent of 0.05% of the cement dosage is added. The grouting body has a 28-day strength of not less than 30MPa. After the grouting is completed, it is cured to more than 90% of the designed slurry strength for anchor tensioning.

[0023] A prestressed anchor cable structure for pre-buried pipe piles on a high fill slope comprises a backfill soil trough, a steel cable casing, a grouting pipe, prestressed pipe piles and a prestressed anchor cable. The backfill soil trough is a rectangular hollow structure with an upper opening, and the backfill soil trough is provided with a prestressed anchor cable, a steel cable casing and prestressed pipe piles. The prestressed anchor cable is connected to the steel cable casing via a connecting bracket, and a grouting pipe is provided in the connecting hole of the connecting bracket. Concrete is filled in the cavity formed between the prestressed anchor cable and the steel cable casing to form a first concrete layer structure. The prestressed pipe pile is sheathed on the outside of the steel cable casing.

[0024] Preferably, the connection between the prestressed pipe pile and the steel cable sleeve is filled with concrete to form a concrete pier structure, and a sealing steel plate is provided at the other end of the prestressed pipe pile; the prestressed anchor cable is formed by twisting multiple steel strands, and a PE pipe is sleeved on the outer wall of the prestressed anchor cable, and anti-corrosion grease is filled between the prestressed anchor cable and the PE pipe; one end of the prestressed anchor cable is fixedly connected to the anti-slip pile; the backfill soil trough is backfilled with concrete.

[0025] The present invention has the following advantages:

[0026] 1. The present invention can improve the horizontal tension of a single anchor cable and adapt to the requirements of high-fill layered construction. By adopting an anchoring structure composed of PHC piles and steel strands, the bearing capacity of a single anchor cable is greatly enhanced, solving the problem of insufficient horizontal tension of traditional anchor cables. It can meet the construction requirements of backfill heights up to 21m and layered compaction, ensuring that stable restraint force can still be provided under the working conditions of an ultra-long anchor cable of 45m, meeting the anti-slip requirements of high-fill slopes.

[0027] 2. The present invention can adapt to the conditions of ultra-long structure construction and thick backfill. In view of the characteristics of the maximum length of 38.8m of the anti-slip pile and the thick backfill on the wall, through the process of combining layered backfill with vibration compaction, and the coordinated design of the pipe pile anchor section and the free section of the steel casing, it can not only withstand the compaction load of the thick backfill, but also ensure the structural integrity of the ultra-long anchor cable during the construction and operation stages, avoiding the problem of insufficient stability caused by the ultra-long structure in traditional construction.

[0028] 3. The present invention can enhance the construction safety and reliability under complex working conditions. By strictly controlling the degree of compaction, grouting pressure and material strength, combined with measures such as construction after the reaction wall strength reaches the standard and slurry curing to 90% strength before tensioning, it can effectively deal with the risks of excessive load and deformation of high fill slopes, solve the technical bottlenecks of traditional solutions such as force imbalance and poor construction adaptability under conditions of ultra-long structures and thick backfill, and ensure the overall safety of the project. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 It is a structural schematic diagram of the prestressed anchor cable structure of the present invention.

[0030] Figure 2 Schematic diagram of the internal structure of the backfill soil trough of the present invention.

[0031] Figure 3 It is a right view of the prestressed anchor cable structure of the present invention.

[0032] Figure 4 It is a structural schematic diagram of the grouting pipe part of the present invention.

[0033] Figure 5 It is a structural schematic diagram of the connecting bracket part of the present invention.

[0034] The meaning of the reference numerals in the figure: 1-anti-slide pile, 2-prestressed anchor cable, 3-steel cable casing, 4-backfill soil trough, 5-concrete pier, 6-prestressed pipe pile, 7-sealing steel plate, 9-PE pipe, 10-grouting pipe. DETAILED DESCRIPTION

[0035] To make the objectives, technical solutions, and advantages of the present invention more apparent, the present invention will be further described in detail below with reference to the accompanying drawings. It is hereby stated that any directional terms such as "up," "down," "left," "right," "front," "back," "inside," and "outside" that appear or will appear herein are based solely on the accompanying drawings and are not intended to limit the present invention.

[0036] Example 1:

[0037] The high fill slope prestressed pipe anchor cable support construction method described in this embodiment is suitable for complex engineering scenarios with large slope heights, extra-long anti-slide piles and anchor cables, and thick backfill soil. In a certain high fill slope treatment project, the maximum backfill height of the slope reached 21m, the maximum design length of the anti-slide piles was 38.8m (including 21m underground and 17.8m above ground), and the prestressed anchor cable length needed to reach 45m. This project adopted this construction method for support construction. The specific application process is as follows:

[0038] S1 Backfill and testing: Soil and stone are selected as backfill material according to the soil-stone volume ratio of 7:3. The maximum particle size of the filler is controlled not to exceed 200mm and the moisture content is 2%. A vibratory roller is used for layered compaction. The thickness of each loose layer is strictly controlled within 300mm. The compaction degree test reaches more than 94% until the backfill reaches the pre-buried elevation of the first layer of pipe piles.

[0039] S2 Positioning and laying out trenches: Use a total station to position and lay out pipe piles according to the designed spacing and position. After determining the buried axis of the pipe piles, use an excavator to excavate the pre-buried trench for the pipe piles to ensure that the trench size meets the requirements for pipe pile installation.

[0040] S3 pipe pile installation and component insertion: PHC 500 AB 125-16 prestressed pipe piles are selected as the anchoring section. The combined length meets the design requirements. The pipe piles are hoisted into the trench using a truck crane. Prestressed anchor cables made of steel strands, grouting pipes, and exhaust pipes (set close to the top of the inner wall of the pipe piles) are inserted into the pipe piles. At the same time, the free end of the prestressed anchor cable is inserted into a steel casing with a diameter of 168 mm. The steel casing is inserted into the supporting pile with a reserved length of 0.9 m inside the steel pipe to ensure that it is not damaged during the compaction of the overlying earth. The bottom of the pipe pile is sealed with a 25 mm thick steel plate using an electric welder.

[0041] S4 Anchorage Section Concrete Pouring and Curing: Pour 800×800mm C30 plain concrete pier at the connection between the outer end of the pile and the free end protective sleeve, and use a vibrator to compact it. After the concrete has initially set, backfill the trench with C20 concrete and then cover with a curing film for curing to ensure that the concrete reaches the specified age and strength.

[0042] S5: Backfill in layers and repeat the process: After the trench backfill concrete has initially set, continue to backfill the next layer of earthwork in layers according to the requirements of S1 until the elevation of the lower row of pipe piles is reached. Then repeat the construction steps of S2-S4 to complete the installation of multiple layers of pipe piles and anchor cables.

[0043] S6 anchor cable grouting, tensioning and anchor sealing: Use a grouting pump to grout the prestressed anchor cable, and the grouting pressure is controlled at 1.5MPa. The grouting body uses 42.5 grade ordinary Portland cement with a water-cement ratio of 0.45, plus a triethanolamine early strength agent with a cement dosage of 0.05%. Grouting is stopped until thick slurry returns to the hole mouth. After the grouting body is cured until the strength reaches more than 30MPa after 28 days (and reaches 90% of the designed slurry strength), prestressed tensioning equipment is used to tension the anchor cable, and finally the anchor sealing operation is completed.

[0044] It should be noted that the combined structure of PHC piles and steel strands significantly improves the horizontal tension of a single anchor cable, fully adapting to the requirements of the project's 21m high backfill layered construction. It can still provide stable restraint force under the working conditions of 45m ultra-long anchor cables, effectively solving the problem of insufficient horizontal tension of traditional prestressed anchor cables and meeting the force requirements of high-fill layered construction.

[0045] It should be further explained that the effective protection of the free section of the anchor cable by the steel casing, as well as the layered backfill and strict compaction control, prevented the pipe piles and anchor cables from being damaged during the compaction of the thick backfill soil, ensuring the structural integrity of the 38.8m long anti-slip piles and 45m long anchor cables, avoiding the lack of stability caused by the excessively long structure and high backfill pressure, and thus adapting to the conditions of ultra-long structures and thick backfill.

[0046] It should be further explained that the strict implementation of quality control measures in all links ensures the overall stability of the support structure. After the completion of the project, it was tested that the slope deformation was controlled within the design allowable range, the 28-day strength of the grouting body exceeded 30MPa, and the anchor tensioning effect met the standards, effectively responding to the complex working conditions of the high fill slope, solving the technical bottleneck of traditional construction solutions in this type of project, and ensuring the safety and reliability of the project construction.

[0047] Example 2:

[0048] In steps S1 and S5, the backfilling of earthwork in layers meets the following requirements:

[0049] First, after the cubic compressive strength of the reaction wall concrete specimens cured under the same conditions reaches 27 MPa, the soil is filled and compacted in layers to the designed top elevation of the piles of the support structure.

[0050] Secondly, during the backfilling process, expansive soil, silty soil, organic soil and cultivated soil must not be used as fillers. The fillers must be compacted layer by layer, and the loose laying thickness must be 280mm.

[0051] Finally, the rolling was performed 4 times using a vibratory roller with operating parameters of a rolling speed of 3 km / h, an amplitude of 2.5 mm, and a compaction degree of 94%.

[0052] It should be noted that the reference index of 90% of the C30 design strength corresponds to the "Code for Design of Concrete Structures" GB 50010.

[0053] The compaction degree reached 94%, based on the maximum dry density specified in the "Standard for Geotechnical Test Methods" (GB / T 50123). Specifically, during construction, on-site sampling and compaction testing were conducted to determine the maximum dry density and optimal moisture content of the backfill. The compaction degree is the ratio of the dry density of the layered fill during actual construction to the maximum dry density. This project required this ratio to be no less than 94%, ensuring that the backfill density meets the load-bearing and deformation resistance requirements of the high-fill slope, providing a stable foundation for subsequent pipe pile and anchor cable construction.

[0054] The following is the test phase of this construction method:

[0055] Purpose of the test:

[0056] To ensure the safe, economical and rational application of prestressed anchor cable structures for embedded pipe piles on high fill slopes, multiple objectives need to be achieved through testing: verifying the ultimate bond anchoring strength of the designed anchor cable in the rock and soil layer to provide a basis for the design bearing capacity; discovering defects in the design and construction of the anchor cable so that the structural parameters can be adjusted or the manufacturing, drilling, grouting, tensioning and other construction processes can be improved before formal use; analyzing the test results to determine the safety factor of the anchor cable, and at the same time revealing the various factors that affect the anchoring force of the anchor cable under the conditions of the formation and their degree of influence, and then verifying the design parameter values ​​to provide relevant parameters for the dynamic design of the slope anchor cable.

[0057] Test plan:

[0058] According to the slope support construction plan and the characteristics of this project, the anchor cable test was divided into two groups, with three anchor cables in each group. The first group was used for basic tests of prefabricated pipe pile anchor cables in the fill area; the second group was used for creep tests of prefabricated pipe pile anchor cables in the fill area.

[0059] The specific parameters of the test anchor cable are shown in the table below:

[0060] The first group of test anchor cables numbered MS01, MS02, and MS03 are used for basic tests of prefabricated pipe pile anchor cables; the second group of MS04, MS05, and MS06 are used for creep tests of prefabricated pipe pile anchor cables.

[0061] Table 1 is the test parameters of prestressed anchor cables

[0062]

[0063] Preparation of test equipment and instruments: hydraulic jack with matching oil pump; WBD-30 electronic dial indicator; accessories of test instruments.

[0064] Test construction: Carry out test construction according to the test process. Please ask the design unit to provide process guidance and collect construction parameters and test parameters; adjust the process according to the test situation and design requirements.

[0065] The anchor cable test can be carried out only after the anchor body strength reaches 90% of the design strength. The basic test of the anchor cable should adopt the graded cyclic loading and unloading method, and the maximum test load should not exceed 0.85 times the standard value of the tensile strength of the anchor cable steel strand, and should comply with the following provisions:

[0066] (1) After each level of load is applied or removed, the deformation should be measured immediately;

[0067] (2) The anchor head displacement should be measured at least three times during each loading and unloading observation time. When the anchor head displacement is not greater than 0.1 mm, the next level of load can be applied. Otherwise, the observation time should be extended until the anchor head displacement increment is less than 1.0 mm in 2 hours before the next level of load can be applied. The loading and unloading levels and the measurement interval time should be determined according to the following table.

[0068] Table 2 shows the timetable of the loading and unloading levels and displacement observation intervals for the basic test cycle of anchor cables (rods)

[0069]

[0070] Note: The estimated maximum failure load of bored anchor cable with length la=16m is 800kN; the estimated maximum failure load of pile anchor cable with length la=16m is 1200kN. If no failure occurs after loading to the estimated maximum failure load, continue to load in increments of 10% each level until failure occurs.

[0071] Test termination conditions:

[0072] During the test, if any of the following situations occurs, it will be regarded as anchor failure:

[0073] ① The displacement increment of the anchor head caused by the next level of load reaches or exceeds twice the displacement increment caused by the previous level of load;

[0074] ②The displacement of the anchor head does not converge;

[0075] ③The steel strand is broken;

[0076] ④The total displacement of the anchor head exceeds the displacement value allowed by the relevant specifications.

[0077] Experimental data collation and result analysis:

[0078] ① After each loading or unloading, the elongation of the anchor rod corresponding to each load level should be recorded separately, and the load-displacement (Q-S) curve should be drawn.

[0079] ② Through test records and results, analyze the actual pull-out capacity of each soil layer and promptly feed back the data to the design unit to make the design and construction more scientific, reasonable and economical.

[0080] ③ After the test is completed, a basic test report should be submitted to the owner, supervisor and design department in a timely manner to verify and adjust the design.

[0081] Conduct creep tests:

[0082] (1) The load level and observation time of the anchor cable creep test should meet the requirements of the following table. The load should remain constant during the observation time.

[0083] Table 3 shows the loading level and observation schedule of the anchor creep test

[0084]

[0085] (2) The creep amount should be recorded at each load holding time interval of 1, 2, 3, 4, 5, 10, 15, 20, 30, 45, 60, 75, 90, 120, 150, 180, 210, 240, 270, 300, 330, and 360 minutes.

[0086] (3) The test results are organized according to load-time-creep, and the creep-time logarithm (S-lgt) curve is drawn. The creep rate is calculated according to the following formula:

[0087] Formula 1

[0088] Where: is the rate coefficient of anchor cable creep; for The creep amount measured over time on test objects such as anchor cables; for The creep amount measured over time on test objects such as anchor cables; is the time point of the first creep measurement; This is the time point for the second creep measurement.

[0089] (4) The creep rate of the anchor cable under the maximum test load should not be greater than 2.00 mm / logarithmic period.

[0090] Acceptance test and completion sampling inspection:

[0091] (1) Acceptance test of prestressed anchor cables

[0092] Acceptance test shall be carried out by random sampling according to the construction drawings and the instructions of the supervising engineer, with the sampling quantity not less than 3 bundles. Acceptance test shall be carried out promptly after tensioning.

[0093] (2) Completion sampling inspection

[0094] ① The completion sampling inspection shall be based on stress control, and the measured value shall not be greater than 5% of the value specified in the construction drawings, nor less than 3% of the specified value;

[0095] ② When the acceptance test is combined with the completion sampling inspection, the number of tests shall be 10% of the total number of anchor cables;

[0096] ③ The completion sampling inspection shall be carried out according to the instructions of the supervising engineer.

[0097] Example 3:

[0098] like Figure 1-Figure 5 As shown, a prestressed anchor cable structure for embedded pipe piles on high fill slopes includes a backfill soil trough 4, a steel cable sleeve 3, a grouting pipe 10, a prestressed pipe pile 6 and a prestressed anchor cable 2. The backfill soil trough 4 is a rectangular hollow structure with an upper opening, and the backfill soil trough 4 is internally provided with a prestressed anchor cable 2, a steel cable sleeve 3 and a prestressed pipe pile 6; the prestressed anchor cable 2 is connected to the steel cable sleeve 3 through a connecting bracket 8, and a grouting pipe 10 is provided in the connecting hole of the connecting bracket 8; the cavity formed between the prestressed anchor cable 2 and the steel cable sleeve 3 is filled with concrete to form a first concrete layer structure; the prestressed pipe pile 6 is externally provided with a prestressed pipe pile 6.

[0099] It should be noted that:

[0100] The backfill soil trough 4 is the trench in the construction method. It is a rectangular hollow structure with an upper opening. It is filled with layered compacted soil and stones. It serves as the bearing foundation of the entire structure. The layered backfill process ensures the overall density and provides a stable installation environment for internal components.

[0101] Prestressed pipe piles 6, the PHC 500 AB 125-16 type pipe piles used in this construction method, are designed to match the designed anchorage depth and are installed outside the cable sleeve 3. The bottom of the pipe piles is welded and sealed with a 25mm thick steel plate. An 800×800mm C30 plain concrete pier is poured at the junction of the outer end and the cable sleeve 3, forming a rigid joint and enhancing the pullout bearing capacity of the anchorage section.

[0102] The cable sleeve 3, a 168mm diameter steel sleeve used in this construction method, covers the free end of the prestressed anchor cable 2 and is inserted 0.9m into the reserved steel pipe of the support pile. The gap between the sleeve and the prestressed pile 6 and the internal cavity are backfilled with C20 concrete, forming a wrap-around protective structure with concrete layer A to prevent sleeve deformation during earth compaction.

[0103] The prestressed anchor cable 2 and the steel strand used in the construction method are woven together, passing through the steel cable sleeve 3 and the prestressed pipe pile 6, and are fixedly connected to the steel cable sleeve 3 through the connecting bracket 8. A grouting pipe 10 is passed through the connecting hole of the connecting bracket 8 to ensure that the grouting body can fully fill the cavity between the anchor cable and the sleeve, forming a first concrete layer structure and enhancing the overall coordinated force-bearing capacity.

[0104] The grouting pipe 10 is set close to the top of the inner wall of the prestressed pipe pile 6, and cooperates with the exhaust pipe to achieve dense filling of the grouting body; the connecting brackets 8 are arranged at intervals, which not only fix the position of the anchor cable, but also provide an installation channel for the grouting pipe 10 to ensure grouting uniformity.

[0105] It should be further explained that the nested structure of the prestressed pipe piles 6 and the steel cable casing 3 forms a "double protection + rigid support" system. The pipe piles are rigidly connected to the casing through concrete piers. Combined with the first concrete layer between the anchor cable and the casing, the tension is effectively transmitted from the anchor cable 2 through the casing 3 and the pipe piles 6 to the backfill trough 4. The horizontal tension of a single anchor cable is increased by more than 30% compared with the traditional structure, which is suitable for the force requirements of the 45m ultra-long anchor cable; and the rectangular cavity design of the backfill trough 4 is suitable for the layered backfill process, which can form a stable structure synchronously with the earth filling; the steel cable casing 3 is inserted into the support pile with a reserved length of 0.9m in the steel pipe. Combined with the wall thickness design of the Φ168 casing, it can withstand the compaction load of 21m thick backfill soil, solving the problem of traditional casing being easily deformed under pressure.

[0106] It should be further explained that the connecting bracket 8 not only fixes the relative position of the anchor cable and the casing, but also provides a precise channel for the grouting pipe 10, ensuring that the grouting body fully fills the gap and the 28-day strength reaches more than 30MPa; the steel plate sealing at the bottom of the pipe pile and the reinforcement of the concrete pier node can avoid internal corrosion caused by rainwater infiltration or soil compression, thereby extending the service life of the structure; the connecting bracket and the pipe pile sealing steel plate can be prefabricated and quickly assembled on site through processes such as hoisting, welding and grouting, and carried out simultaneously with the layered backfill construction to reduce cross-operation interference.

[0107] The embodiments of the present invention are described in detail above with reference to the accompanying drawings. However, the present invention is not limited to the above embodiments. Various changes can be made within the scope of knowledge of those skilled in the art without departing from the spirit of the present invention.

Claims

1. A construction method for prestressed pipe anchor support on high fill slope, characterized in that: The following steps are involved: S1. Earthwork backfilling and testing: Backfill the earthwork in layers to the pre-buried elevation of the piles and test the compaction degree; S2. Positioning and laying out the lines and excavating the trench: After positioning and laying out the pipe piles, excavate the pre-buried trench for the pipe piles; S3. Installation of pipe piles and component threading: Complete the lifting and installation of pipe piles in the trench, insert the prestressed anchor cables and grouting pipes into the pipe piles, and insert the free ends of the prestressed anchor cables into the steel casing; S4. Anchorage section concrete pouring and curing: pour the anchorage section encapsulation concrete and cure the concrete to the specified age; S5, backfilling in layers and repeating the process: backfilling the next layer of earthwork to the elevation of the next row of pipe piles, and repeating the above steps S1-S4; S6. Anchor cable grouting, tensioning and anchor sealing: complete the prestressed anchor cable grouting, tensioning and anchor sealing operations.

2. A high fill slope prestressed pipe anchor cable support construction method according to claim 1, characterized in that: In step S2, the trench is excavated after the pile embedding axis and position are determined according to the designed spacing, position and test anchor length.

3. A high fill slope prestressed pipe anchor cable support construction method according to claim 1, characterized in that: In step S3, the pipe piles are PHC500AB125-16 prestressed pipe piles, and steel strands are arranged inside the pipe piles; In step S3, the diameter of the steel casing is 168 mm, and the length of the steel casing inserted into the reserved steel pipe of the support pile is not less than 0.8 m.

4. A high fill slope prestressed pipe anchor cable support construction method according to claim 1, characterized in that: In step S3, when placing the pipe pile and protective sleeve in the trench, an exhaust pipe is also inserted inside and placed close to the top of the inner wall of the pipe pile; an 800×800mm C30 plain concrete pier is cast at the connection between the outer end of the pipe pile and the free end protective sleeve, and the bottom of the pipe pile is sealed with a 25mm thick steel plate by welding.

5. A high fill slope prestressed pipe anchor cable support construction method according to claim 1, characterized in that: In step S4, after the anchor cables are buried, the trench is backfilled with C20 concrete, and after the backfilled concrete has initially set, soil is continuously backfilled in layers until the designed height is reached.

6. A high fill slope prestressed pipe anchor cable support construction method according to claim 1, characterized in that: In steps S1 and S5, the backfilling of earthwork in layers meets the following requirements: After the cubic compressive strength of the reaction wall concrete specimens cured under the same conditions reaches 27MPa, fill and compact the soil in layers to the designed top elevation of the piles of the support structure; The backfill material is soil mixed with rock, with a soil-rock volume ratio of 7:3 and a maximum particle size of no more than 200mm. The moisture content of the on-site filler is controlled within the range of 1%-2%, and the compaction degree is no less than 94%; During the backfilling process, expansive soil, silty soil, organic soil, and cultivated soil must not be used as fillers. The fillers must be compacted layer by layer, with a loose laying thickness of 200mm to 300mm. The rolling times are 3 to 5 times, using a vibratory roller with operating parameters of a rolling speed of 2 to 4 km / h, an amplitude of 1.5 to 3 mm, and a compaction degree of 94%.

7. A high fill slope prestressed pipe anchor cable support construction method according to claim 1, characterized in that: In step S6, the anchor grouting pressure is 1.0Mpa~2.0Mpa, the grouting amount is based on the concentrated slurry returned from the hole, the grouting body uses ordinary Portland cement with a strength grade of 42.5 and a water-cement ratio of 0.38~0.55, and an early strength agent of triethanolamine of 0.05% of the cement dosage is added. The grouting body has a 28-day strength of not less than 30MPa. After the grouting is completed, it is cured to more than 90% of the designed slurry strength for anchor tensioning.

8. The prestressed anchor cable structure of the pre-buried pipe piles on the high fill slope manufactured by the construction method according to claim 1 is characterized in that: The invention comprises a backfill soil trough body (4), a steel cable sleeve (3), a grouting pipe (10), a prestressed pipe pile (6) and a prestressed anchor cable (2); the backfill soil trough body (4) is a rectangular hollow structure with an upper opening, and the backfill soil trough body (4) is provided with a prestressed anchor cable (2), a steel cable sleeve (3) and a prestressed pipe pile (6); the prestressed anchor cable (2) is connected to the steel cable sleeve (3) through a connecting bracket (8), and a grouting pipe (10) is provided in a connecting hole of the connecting bracket (8); the cavity formed between the prestressed anchor cable (2) and the steel cable sleeve (3) is filled with concrete to form a first concrete layer structure; the prestressed pipe pile (6) is sleeved on the outside of the steel cable sleeve (3).

9. The prestressed anchor cable structure of the pre-buried pipe piles in the high fill slope according to claim 8, characterized in that: The connection between the prestressed pipe pile (6) and the steel cable sleeve (3) is filled with concrete to form a concrete pier structure (5), and a sealing steel plate (7) is provided at the other end of the prestressed pipe pile (6); The prestressed anchor cable (2) is formed by twisting a plurality of steel strands, and a PE tube (9) is sleeved on the outer wall of the prestressed anchor cable (2), and anti-corrosion grease is filled between the prestressed anchor cable (2) and the PE tube (9); One end of the prestressed anchor cable (2) is fixedly connected to the anti-slip pile (1); The backfill soil trough (4) is backfilled with concrete.

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