A tension beam-controlled variable cross-section double-row pile support structure and construction method suitable for backfill slopes

Abstract

This invention discloses a tie-beam actively controlled variable cross-section double-row pile support structure and construction method suitable for backfill slopes. The structure includes a front row of piles, a rear row of piles, and at least two tie beams connecting the front and rear rows of piles. Both the front and rear rows of piles are arranged at intervals along the slope direction. This invention achieves a fundamental shift from traditional passive to active force-bearing in double-row pile support structures by employing prestressed tension beams. Traditional support structures only passively resist lateral pressure after slope deformation, while this invention actively applies prestress to the front and rear rows of piles by pre-tensioning the prestressed tendons within the tie beams, adjusting the structural stress state in advance and effectively suppressing lateral slope deformation and backfill settlement. Compared to anchor cables, tie beams, as rigid connection components, have stronger load-bearing capacity and superior deformation resistance, significantly reducing the risk of backfill settlement and ensuring long-term stability of the support structure, fully meeting the safety requirements for permanent support of backfill slopes.

Description

Technical Field

[0001] This invention relates to the field of geotechnical engineering technology, specifically to a tie-beam active control type variable cross-section double-row pile support structure and construction method suitable for backfill slopes. Background Technology

[0002] Backfilled slopes often fail to achieve the required compaction degree as per design specifications. Over time, they are susceptible to settlement and increased lateral deformation due to their own weight, rainfall, and external loads. Therefore, their permanent support structures must possess long-term reliable load-bearing and deformation resistance. Double-row pile support structures, with their advantages of high lateral stiffness and strong anti-overturning capacity, are widely used in the permanent support of backfilled slopes.

[0003] Traditional double-row pile support structures typically employ a single cross-section (e.g., circular) design for the piles. Circular piles offer advantages such as high efficiency and uniform stress distribution during underground construction. However, once exposed above ground, their connection to the horizontal tie beams is complex, resulting in poor force transmission performance and an irregular appearance. While square piles are easier to connect, underground drilling is relatively more difficult and costly.

[0004] Traditional double-row pile permanent support structures often use capping beams as the connecting components between the front and rear rows of piles, located at the ground level. Their core load-bearing characteristic is passive load-bearing, relying on the interaction between the piles and the soil to passively resist lateral slope pressure. They only exert their load-bearing function after slope deformation, unable to proactively adjust the load-bearing state in advance. Furthermore, the placement of the top beam connecting the traditional front and rear rows of piles often occupies upper space, causing significant inconvenience for subsequent construction projects such as pipeline laying, road construction, and landscaping on the backfilled slope. The passive load-bearing mode also suffers from drawbacks such as delayed response, uneven stress distribution, and low collaborative load-bearing efficiency. The support structure is prone to cracking and instability due to excessive deformation, failing to meet the long-term safety requirements of permanent support.

[0005] In recent years, active stress control methods have mostly focused on the use of anchor cables, without the active control of tie beams. Anchor cables are prone to deformation and have no load-bearing capacity, making them more suitable for temporary projects such as foundation pit support. They are difficult to guarantee the long-term stability, environmental adaptability and other special requirements of permanent support for backfilled slopes.

[0006] Therefore, developing a support structure that adapts to the permanent support requirements of backfill slopes, avoids space for upper pipeline laying, and possesses independent active control function of tie beams, transforming the double-row pile support structure from passive to active stress, can significantly improve the deformation control capability and stress balance of the support structure without significantly increasing construction costs, and can significantly reduce the degree of backfill soil settlement, is of great significance. Based on this, this invention proposes a tie beam active control variable cross-section double-row pile support structure suitable for backfill slopes. Summary of the Invention

[0007] Therefore, this invention provides a tie-beam active control type variable cross-section double-row pile support structure and construction method suitable for backfill slopes, in order to solve the problems in the prior art.

[0008] To achieve the above objectives, the present invention provides the following technical solution:

[0009] A tie beam active control type variable cross section double-row pile support structure suitable for backfill slopes includes a front row of piles, a rear row of piles, and at least two tie beams connecting the front row of piles and the rear row of piles. The front row of piles and the rear row of piles are arranged at intervals along the direction of the backfill slope. The front row of piles is set on the side close to the slope, and the rear row of piles is set on the side away from the slope.

[0010] Both the front and rear rows of piles are variable cross-section piles. The parts below ground are circular pile segments for the front and rear rows, and the parts above ground are square pile segments for the front and rear rows. The circular pile segments and square pile segments of the front and rear rows, as well as the square pile segments and circular pile segments of the rear rows, are integrally formed structures. A pile-to-pile baffle is installed behind the front row of piles, and drainage holes are installed between the pile-to-pile baffles.

[0011] Both tie beams are located above the original ground level and below the backfill ground level. Each tie beam adopts a tensioned prestressed structure, which includes the tie beam and a reserved tensioning duct. The tie beam is a reinforced concrete beam with a reserved duct inside for inserting prestressing tendons. The anchor head of the tensioned prestressed structure adopts a recessed sealing anchor structure.

[0012] Preferably, the first tie beam is 2m deep from the backfill ground, the second tie beam is located directly below the first tie beam, and the vertical distance between the two tie beams is 3m.

[0013] Preferably, the prestressing tendons in the tie beam are prestressed steel bars or prestressed anchor cables.

[0014] Preferably, the reserved ducts of the tie beam are set along the length of the beam, and the diameter of the ducts is slightly larger than the diameter of the prestressing tendons. The two ends of the ducts are reserved with installation grooves for placing bearing pads and anchors.

[0015] Preferably, the tensioning end of the rear pile tensioning structure is tensioned using a tensioning jack, which is a miniaturized jack or a combination jack.

[0016] Preferably, the prestressed duct is pre-embedded with a corrugated pipe, the diameter of which matches the diameter of the reserved duct, and the surface of the prestressed tendon is coated with an anti-corrosion coating.

[0017] Preferably, the diameter of the circular pile segment is 1000-1200mm, and it is constructed using the bored pile technique; the cross-sectional dimensions of the square pile segment are 700mm×700mm to 840mm×840mm, and it is constructed using the cast-in-place technique.

[0018] Preferably, the spacing between the front and rear rows of piles is 1.5 to 3 m, and the spacing between the front and rear rows of piles is 5 to 8 m; if there is no building load on the top of the fill slope, the spacing between the rear rows of piles can be twice the spacing between the front rows of piles.

[0019] Preferably, the cross-sectional dimensions of the main body of the tie beam are 700mm×800mm-800mm×1000mm, and reinforcing ribs are provided at the connection between the main body of the tie beam and the square pile section.

[0020] To achieve the above objectives, the present invention also provides the following technical solution:

[0021] A construction method for a tie-beam actively controlled variable cross-section double-row pile support structure suitable for backfill slopes includes the following steps:

[0022] Step 1: Construct the front and rear circular pile sections below ground level using the bored cast-in-place pile technology. After drilling to the designed depth, clean the hole and place the reinforcing cage.

[0023] Step 2: After the concrete curing of the circular pile segments of the front row and the circular pile segments of the rear row reaches the standard, the square pile segments of the front row and the square pile segments of the rear row are cast in place on top of them. The formwork is set and fixed, the concrete is poured and vibrated to compact it, and cured to the design strength. The tie beam steel bars and reinforcing bars are pre-embedded at the tie beam elevation, and the tensioning structure reserved for the connection between the tie beam and the pile body is reserved.

[0024] Step 3: After the construction of the first row of piles is completed, construct the pile-interval baffle between adjacent front piles and fix it to the front piles through pre-embedded connectors. Drainage holes are set between the baffles, and a reverse filter bag is set after the drainage holes.

[0025] Step 4: After backfilling the soil between the piles to the elevation of the tie beam, tie the tie beam reinforcement. Pre-reserved ducts are reserved along the length of the beam, and corrugated pipes are installed.

[0026] Step 5: Insert the prestressed tendons into the reserved ducts, and anchor both ends firmly in the reserved grooves of the pile. After the anchorages are installed in the rear piles, install the tensioning jacks.

[0027] Step 6: After tensioning is completed, grout is injected into the duct;

[0028] Step 7: Place the steel mesh into the reserved groove and tie it to the stirrups of the beam, then seal the anchor with concrete.

[0029] The present invention has the following advantages:

[0030] Excellent Active Control Performance: This invention utilizes a tensioned prestressed structure in the tie beam, achieving a fundamental shift from traditional passive to active stress distribution in double-row pile support structures. Traditional support structures passively resist lateral pressure only after slope deformation occurs. In contrast, this invention actively applies prestress to the front and rear rows of piles by pre-tensioning the prestressed tendons within the tie beam, adjusting the structural stress state in advance and effectively suppressing lateral slope deformation and backfill settlement. Compared to anchor cables, the tie beam, as a rigid connection component, has stronger load-bearing capacity and superior deformation resistance, significantly reducing the risk of backfill settlement and ensuring long-term stability of the support structure, fully meeting the safety requirements for permanent support of backfilled slopes.

[0031] The space is used rationally, which facilitates subsequent construction: Both tie beams are set above the original ground and below the backfill ground, avoiding the upper space. This solves the problem that the traditional front and rear pile top beams occupy the upper space, causing inconvenience for pipeline laying, road construction and greening projects. It provides sufficient space for subsequent construction on the upper part of the backfill slope, improves the site utilization rate and reduces the overall coordination difficulty of the project construction.

[0032] The variable cross-section pile design takes into account both construction and connection advantages: the front and rear piles adopt an integrated variable cross-section design with round piles below ground and square piles above ground. The round piles below ground can be adapted to efficient and mature underground construction techniques such as bored piles, effectively reducing the difficulty and cost of underground drilling and ensuring construction efficiency; the square piles above ground facilitate reliable connection with tie beams, simplify connection node treatment, and improve force transmission performance. At the same time, the square piles have a regular appearance, which enhances the overall aesthetics of the structure.

[0033] Easy to construct, without increasing costs or extending the construction period: The construction technology adopted in this invention is a mature technology in the field of geotechnical engineering, such as bored piles, cast-in-place concrete, and prestressed tensioning. Construction technicians can easily master these technologies, without the need to introduce complex new construction equipment and processes. The construction of variable cross-section piles and tie beams can be seamlessly connected, with clear logic and smooth flow in each construction step. This will not increase construction costs or extend the construction period, demonstrating good engineering applicability and economy.

[0034] The structure boasts high durability and adaptability to long-term support requirements: In the tie-beam prestressed structure, the surface of the prestressing tendons is coated with an anti-corrosion coating, the prestressing ducts are protected by pre-embedded corrugated pipes, and the anchor heads adopt a recessed sealing anchor structure, effectively preventing the prestressing tendons from being eroded by the external environment and improving structural durability. The variable cross-section piles are integrally formed, ensuring reliable connections. Combined with the active force-bearing characteristics of the tie beams, the entire support structure possesses long-term self-adaptive safety performance, capable of resisting the adverse effects of long-term self-weight, precipitation, and external loads on the backfilled slope, resulting in a long service life. Attached Figure Description

[0035] To more intuitively illustrate the prior art and this application, exemplary drawings are provided below. It should be understood that the specific shapes and structures shown in the drawings should not generally be regarded as limiting conditions for implementing this application; for example, based on the technical concept disclosed in this application and the exemplary drawings, those skilled in the art are able to easily make conventional adjustments or further optimizations to the addition / reduction / classification, specific shapes, positional relationships, connection methods, size ratios, etc. of certain units (components).

[0036] Figure 1 A structural diagram of a tie-beam active control variable cross-section double-row pile support structure suitable for backfill slopes provided in this application embodiment;

[0037] Figure 2 A cross-sectional schematic diagram of a tie-beam active control variable cross-section double-row pile support structure suitable for backfill slopes, provided in this application embodiment;

[0038] Figure 3 This is a schematic diagram showing the connection between the prestressed structure of the tie beam and the pile body in a tie beam active control variable cross-section double-row pile support structure suitable for backfill slopes, provided in an embodiment of this application.

[0039] In the diagram: 1. Front row of piles; 2. Rear row of piles; 3. Pile-to-pile baffle; 4. Tie beam; 5. Prestressed structure; 6. Schematic diagram of the original strata of the slope; 7. Schematic diagram of the backfill soil layer of the slope; 8. Reinforcing bar; 11. Square pile section of the front row of piles; 12. Round pile section of the front row of piles; 13. Crown beam of the front row of piles; 21. Square pile section of the rear row of piles; 22. Round pile section of the rear row of piles; 23. Crown beam of the rear row of piles; 31. Drainage hole; 51. Reserved duct; 52. Prestressed tendon; 53. Reserved groove; 54. Bearing pad; 55. Anchorage; 56. Tensioning jack; 57. Sealing anchor; 61. Original ground line of the slope; 62. Ground line after backfilling of the slope. Detailed Implementation

[0040] The following specific embodiments illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. It should be understood that these embodiments are merely for further explanation of the present invention and should not be construed as limiting the scope of protection of the present invention. Technical engineers in the field can make some non-essential improvements and adjustments to the present invention based on the above-described content. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0041] Please see Figure 1-3A tie-beam active control type variable cross-section double-row pile support structure suitable for backfill slopes includes a front row of piles 1 and a rear row of piles 2 arranged at intervals along the direction of the backfill slope. The front row of piles 1 is close to the slope side, and the rear row of piles 2 is far away from the slope side. There is a building load at the top of the backfill slope. The spacing of the front row of piles 1 is 1.5m, and the spacing of the rear row of piles 2 is set to 1.5m. The row spacing between the front row of piles 1 and the rear row of piles 2 is 8m.

[0042] Both the front row of piles 1 and the rear row of piles 2 are variable cross-section piles. The diameter of the circular pile segment 12 of the front row of piles and the circular pile segment 22 of the rear row of piles below ground is 1000mm, and they are constructed using the bored pile technology. The cross-sectional dimensions of the square pile segment 11 of the front row of piles and the square pile segment 21 of the rear row of piles above ground are 700mm×700mm, and they are constructed using the cast-in-place technology, with the circular piles and square piles being formed as one piece. A reinforced concrete pile-interlocking baffle 3 is constructed after the front row of piles 1.

[0043] After slope backfilling, both tie beams 4 are located below ground level. The first tie beam 4 is 2m below ground level, and the second tie beam 4 is 3m vertically spaced from the first tie beam 4. The main body of tie beam 4 is a reinforced concrete beam with a cross-sectional dimension of 700mm × 800mm. Reinforcing bars 8 are installed at the connection between tie beam 4 and the square pile section. Pre-reserved ducts 51 are pre-drilled along the length of tie beam 4. The diameter of the pre-reserved ducts 51 is slightly larger than the diameter of the prestressing tendons 52. Corrugated pipes are pre-embedded, and the diameter of the corrugated pipes matches the diameter of the pre-reserved ducts 51. The prestressing tendons 52 are made of prestressed steel bars with an anti-corrosion coating on the surface. Grooves 53 are pre-drilled at both ends of the pre-reserved ducts 51.

[0044] The construction steps for permanent support of backfill slopes using the support structure described in the above embodiment are as follows:

[0045] Step 1: Construct the front row of circular piles (section 12) and the rear row of circular piles (section 22) below ground level using the bored cast-in-place pile technology. After drilling, clean the holes and then place the reinforcing cage. The main reinforcement of the reinforcing cage consists of 12 HRB400 φ25mm steel bars, and the stirrups consist of HPB300 φ8mm steel bars, spaced 200mm apart.

[0046] Step 2: After the concrete pouring of the front row of circular pile segment 12 and the rear row of circular pile segment 22 is completed, cure for 7-14 days until the concrete strength reaches 70% of the design strength. Then, construct the front row of square pile segment 11 and the rear row of square pile segment 21 in place on top of them. Set up steel formwork and fix it firmly with tie bolts. Pour C30 concrete and compact it with an immersion vibrator. Cure for 14 days until the design strength is reached. Embed the reinforcing bars of tie beam 4 and the reinforcing bars 8 at the elevation of tie beam 4. The reinforcing bars 8 are HRB400 φ20mm steel bars. At the same time, reserve the tensioning structure 53 for the connection between tie beam 4 and the pile body.

[0047] Step 3: After the construction of the front row of piles 1 is completed, construct the inter-pile baffle 3 between adjacent front row piles 1. The baffle is made of C30 reinforced concrete cast in place, with a thickness of 100mm, and is reliably fixed to the front row of piles 1 by pre-embedded steel plates. Drainage holes 31 with a diameter of 110mm are set between the baffles. According to the backfill height of the slope, two rows of drainage holes 31 are set, with a vertical hole spacing of 2m. A filter bag is installed after the drainage holes 31.

[0048] Step 4: After backfilling the soil between the piles to the elevation of tie beam 4, tie the reinforcing bars of tie beam 4. The main reinforcement of tie beam 4 uses HRB400 φ20mm steel bars, and the stirrups use HPB300 φ8mm steel bars, with a spacing of 200mm. There are reserved ducts 51 along the length of the beam, with a diameter of 250mm, and corrugated pipes are embedded there.

[0049] Step 5: Insert the prestressing tendons 52 into the reserved ducts 51. The prestressing tendons 52 are made of 3Φs15.2 steel strands. Both ends are firmly anchored at the reserved grooves 53 of the pile through the bearing pads 54 and anchors 55. After the anchors 55 are installed in the rear pile 2, install the tensioning jacks 56 consisting of two small jacks.

[0050] Step Six: Tension the anchor 57 using tensioning jack 56. The tensioning sequence is to tension the second tie beam 4 first, then the first tie beam 4. After tensioning, grout the duct using P.O42.5 cement grout until uniform grout overflows from the grout outlet pipe.

[0051] Step 7: Place the pre-tied steel mesh with a spacing of 50mm and HPB300φ8mm into the groove and reliably tie it to the pre-embedded stirrups in the beam. After installation, use C30 concrete to seal the anchor 57. After sealing the anchor, the surface of the front row of square piles 11 and the rear row of square piles 21 is smooth and flat.

[0052] The implementation effect of this embodiment is as follows:

[0053] After the completion of the support structure, 12 months of monitoring showed that the connection between tie beam 4 and the front pile 1 and rear pile 2 was reliable, with no cracking or loosening, minimal prestress loss, and uniform structural stress. Simultaneously, because tie beam 4 avoided the upper space, pipeline laying and road construction at the top of the slope proceeded smoothly without being affected by the support structure. This embodiment fully demonstrates that the support structure of the present invention has advantages such as strong active deformation control capability, good bearing capacity, convenient construction, and saving upper space, while the construction cost and construction period are not increased compared to traditional support structures, fully meeting the requirements for permanent support of backfilled slopes.

[0054] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A tie-beam actively controlled variable cross-section double-row pile support structure suitable for backfill slopes, characterized in that, It includes a front row of piles (1), a rear row of piles (2), and at least two tie beams (4) connecting the front row of piles (1) and the rear row of piles (2). The front row of piles (1) and the rear row of piles (2) are arranged at intervals along the direction of the backfill slope. The front row of piles (1) is set on the side close to the slope, and the rear row of piles (2) is set on the side away from the slope. The front row of piles (1) and the rear row of piles (2) are both variable cross-section piles. The part below the ground is the circular pile section (12) of the front row of piles and the circular pile section (22) of the rear row of piles. The part above the ground is the square pile section (11) of the front row of piles and the square pile section (21) of the rear row of piles. The circular pile section (12) of the front row of piles and the square pile section (11) of the front row of piles, and the square pile section (21) of the rear row of piles and the circular pile section (22) of the rear row of piles are all integrally formed structures. A pile baffle (3) is set behind the front row of piles (1). A drainage hole (31) is set between the pile baffles (3). Both tie beams (4) are located above the original ground and below the backfill ground. Each tie beam (4) adopts a tensioned prestressed structure (5). The prestressed structure (5) includes the tie beam (4) and a reserved duct (51). The tie beam (4) is a reinforced concrete beam. The reserved duct (51) is reserved inside the beam for inserting prestressing tendons (52). The anchor head of the tensioned prestressed structure (5) adopts a recessed sealing anchor (57) structure.

2. The tie-beam active control type variable cross-section double-row pile support structure suitable for backfill slopes according to claim 1, characterized in that, The first tie beam (4) is 2m deep from the backfill ground, and the second tie beam (4) is located directly below the first tie beam (4). The vertical distance between the two tie beams (4) is 3m.

3. The tie-beam active control type variable cross-section double-row pile support structure suitable for backfill slopes according to claim 1, characterized in that, The prestressed tendons (52) in the tie beam (4) are prestressed steel bars or prestressed anchor cables.

4. A tie-beam active control type variable cross-section double-row pile support structure suitable for backfill slopes according to claim 1, characterized in that, The reserved duct (51) of the tie beam (4) is set along the length of the beam body. The diameter of the duct is slightly larger than the diameter of the prestressing tendon (52). The two ends of the duct are reserved with installation grooves for placing the pressure bearing plate (54) and the anchor (55).

5. A tie-beam active control type variable cross-section double-row pile support structure suitable for backfill slopes according to claim 1, characterized in that, The tensioning end of the rear pile (2) is tensioned using a tensioning jack (56), which is a miniaturized jack or a combination jack.

6. A tie-beam active control type variable cross-section double-row pile support structure suitable for backfill slopes according to claim 1, characterized in that, The reserved channel (51) is pre-embedded with a corrugated pipe, the diameter of which matches the diameter of the reserved channel (51), and the surface of the prestressed tendon (52) is coated with an anti-corrosion coating.

7. A tie-beam active control type variable cross-section double-row pile support structure suitable for backfill slopes according to claim 1, characterized in that, The diameter of the circular pile segment is 1000-1200mm, and it is constructed using the bored pile technique; the cross-sectional dimensions of the square pile segment are 700mm×700mm to 840mm×840mm, and it is constructed using the cast-in-place technique.

8. A tie-beam active control type variable cross-section double-row pile support structure suitable for backfill slopes according to claim 1, characterized in that, The spacing between the front row of piles (1) and the rear row of piles (2) is 1.5 to 3m, and the spacing between the front row of piles (1) and the rear row of piles (2) is 5 to 8m. If there is no building or other load on the top of the fill slope, the spacing of the rear row of piles (2) can be twice the spacing of the front row of piles (1).

9. A tie-beam active control type variable cross-section double-row pile support structure suitable for backfill slopes according to claim 1, characterized in that, The cross-sectional dimensions of the main body of the tie beam (4) are 700mm×800mm-800mm×1000mm, and a reinforcing bar (8) is provided at the connection between the main body of the tie beam (4) and the square pile section.

10. A construction method for a tie-beam actively controlled variable cross-section double-row pile support structure suitable for backfill slopes, characterized in that, Includes the following steps: Step 1: Construct the front row of circular piles (12) and the rear row of circular piles (22) below ground level using the bored pile technology. After drilling to the design depth, clean the hole and place the steel cage. Step 2: After the concrete curing of the front row of round piles (12) and the rear row of round piles (22) reaches the standard, the front row of square piles (11) and the rear row of square piles (21) are cast in place on the top. The formwork is set and fixed, the concrete is poured and vibrated to compact it, and cured to the design strength. The tie beam (4) is at an elevation higher than the pre-embedded tie beam (4) steel bars and reinforcing bars (8), and a pre-reserved groove (53) for the tensioning structure connecting the tie beam (4) and the pile body is reserved. Step 3: After the construction of the front row of piles 1 is completed, a pile-to-pile baffle (3) is constructed between adjacent front row piles (1). It is fixed to the front row of piles (1) by pre-embedded connectors. A drainage hole (31) is set between the pile-to-pile baffles (3), and a filter bag is set behind the drainage hole (31). Step 4: After backfilling the soil between the piles (3) to the elevation of the tie beam (4), tie the reinforcing bars of the tie beam (4), and pre-reserved ducts (51) are reserved along the length of the beam and corrugated pipes are installed. Step 5: Insert the prestressed tendons (52) into the reserved duct (51), and anchor both ends firmly at the reserved groove (53) of the pile. After the anchorage (55) is installed on the rear pile (2), install the tensioning jack (56). Step 6: After tensioning is completed, grout is injected into the duct; Step 7: Place the steel mesh into the reserved groove (53) and tie it with the stirrups of the beam, and use concrete to seal the anchor (57).

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