Anti-pulling and anti-compression steel pipe inclined pile rock-entering foundation pit supporting system and construction method

Abstract

According to the system, Q355 steel pipe inclined piles with the diameter of 377 mm and the wall thickness of 10 mm are embedded into a rock stratum at the angle of 45-90 degrees, cement paste or C30 concrete is poured for anchoring, eight C20 steel bars are arranged on the peripheries of the piles and anchored into a top beam, and a bracket type water stop steel plate is arranged at the joint of the piles and a bottom plate. During construction, a double-tower percussion drill is adopted to form holes with pipes, a soil layer section is connected with a casing pipe, a rock layer section is welded with a groove, the depth of entering slightly weathered rocks is larger than or equal to 3.5 m, and the compressive bearing capacity of a single pile is 2100 kN. Compared with a traditional support, the steel pipe pile can penetrate through special geologies such as sand layers and pebbles, the material consumption is reduced by 80%, the potential safety hazard of support dismounting is avoided, the steel pipe pile can be used as a building anti-pulling and anti-pressing pile after support dismounting, and the steel pipe pile is suitable for deep foundation pit support and has remarkable economic and social benefits.

Description

Technical Field

[0001] The present invention relates to the technical field of foundation pit support for construction projects, and specifically to a foundation pit support system and a construction method thereof, which provides pull-out and compressive bearing capacity by embedding steel pipe oblique piles into rock strata. The system is suitable for deep foundation pit excavation support under various geological conditions, and is particularly suitable for special geological conditions such as sand layers, pebbles, boulders, and caves, as well as engineering scenarios requiring rock anchoring. Background Art

[0002] In modern urban construction, deep foundation pit excavation is an essential step in basement construction. The safety of its support directly impacts the safety of surrounding buildings and underground pipelines. Traditionally, two- to three-story basement pit support often employs a "pile row + prestressed anchor cable" or "pile row + internal support" approach, but these approaches present the following technical bottlenecks: Space occupation and construction cycle issues: Traditional horizontal internal supports require a large amount of space in the pit, resulting in low efficiency in excavation and foundation construction. Later, blasting and cleaning are required to remove the supports, increasing construction time and costs. Geological adaptability limitations: Improved solutions such as concrete pipe pile bracing and mixing piles plus steel lattice bracing have difficulty penetrating special geological conditions such as sand layers, pebbles, and karst caves, and cannot be anchored in moderately or slightly weathered rock formations, resulting in insufficient bearing capacity. Waterstop and connection defects: The waterstop structure of the traditional support system is complex, the connection nodes are prone to leakage, and the support point displacement is large, affecting the stability of the foundation pit; Resource consumption and environmental protection issues: A large amount of reinforced concrete materials are used, and the subsequent dismantling of supports produces construction waste, which does not meet the requirements of green construction.

[0003] Therefore, there is an urgent need for a foundation pit support system that can adapt to complex geology, reduce space occupancy, and improve construction safety and economy. Summary of the Invention

[0004] The purpose of the present invention is to provide a foundation pit support system and construction method with pull-out and compression-resistant steel pipe oblique piles driven into the rock. Through the steel pipe oblique pile rock anchoring technology, the construction difficulties of the traditional support system under special geological conditions are solved, material consumption and construction costs are reduced, and the reliability and construction efficiency of the foundation pit support are improved.

[0005] In order to achieve the above object, the present invention is implemented through the following technical solutions: a foundation pit support system with anti-pulling and anti-compression steel pipe oblique piles embedded in rock, comprising: Steel pipe inclined piles, wherein anchor steel bars are arranged along the circumference of the piles, and the length of the anchor steel bars at the pile head meets the design requirements; In the rock anchoring structure, the steel pipe inclined pile is embedded in the rock layer at a predetermined angle, and the pile body is poured with solidifying material to form an anchoring section; The connection structure is that the steel pipe inclined pile is connected to the crown beam or the basement floor through a connection member.

[0006] As a further improvement to the technical solution of the present invention, the steel pipe inclined piles are made of Q355 steel with a diameter and wall thickness that meet predetermined specifications for the project. No less than 8 anchor steel bars are evenly distributed around the pile, and the length of the anchor steel bar at the pile head is no less than 70 cm.

[0007] As a further improvement of the technical solution of the present invention, the predetermined angle is 45°-90°, the solidifying material is cement slurry or self-compacting underwater concrete, wherein the cement slurry is prepared with 42.5R ordinary Portland cement, the water-cement ratio is 0.5, the compressive strength of the pile body is not less than 30 MPa, and the grouting pressure is 2.5 MPa.

[0008] As a further improvement to the technical solution of the present invention, the soil layer section of the steel pipe inclined pile is connected by casing, the rock layer section is connected by groove butt welding, the depth of embedding in the slightly weathered rock is not less than 3.5m, and the characteristic value of the compressive bearing capacity of a single pile is not less than 2100kN.

[0009] As a further improvement to the technical solution of the present invention, when the steel pipe inclined piles are arranged toward the outside of the foundation pit, a barb structure is provided in the non-rock layer section of the pile body, and the connecting member includes a corbel-type water-stop steel plate or a steel corbel.

[0010] As a further improvement to the technical solution of the present invention, a construction method for a foundation pit support system with anti-tension and anti-compression steel pipe oblique piles embedded in rock comprises the following steps: Step S1: leveling the site and completing the support pile construction; Step S2: The impact drill is positioned to determine the position of the steel pipe inclined pile according to a predetermined angle; Step S3: Processing steel pipe piles, with different connection methods used for the soil layer section and the rock layer section; Step S4: drilling with a drill rig and pipe to a designed rock penetration depth; Step S5, pouring curing material to solidify the pile body; Step S6: Cast the crown beam and connect it to the top of the steel pipe inclined pile through a connecting member; Step S7: excavating earth in layers and constructing the basement structure; Step S8: After the strength of the support beam to be replaced reaches 80%, the steel pipe inclined piles are removed.

[0011] As a further improvement to the technical solution of the present invention, the impact drill rig has a double-tower structure, which can realize construction at an angle of 45°-90°. When drilling, the grouting pipe is lowered to the bottom of the hole and then lifted 50mm, and grouting is carried out at a pressure of 2.5MPa until pure slurry emerges from the hole mouth.

[0012] As a further improvement to the technical solution of the present invention, a corbel-type water-stopping steel plate is provided at the junction of the steel pipe inclined pile and the basement floor, and the steel plate is welded to the foundation floor to form a water-stopping structure.

[0013] As a further improvement to the technical solution of the present invention, the steel pipe inclined piles retained under the bottom plate after the support is removed serve as vertical load-bearing and anti-pullout members of the building and are rigidly connected to the foundation structure.

[0014] As a further improvement to the technical solution of the present invention, when the steel pipe inclined pile replaces the prestressed anchor cable, a barb structure is welded in the non-rock layer section, the barbs are symmetrically arranged around the pile, double-sided welded and the welding length is not less than 5 times the diameter of the steel bar.

[0015] The present invention has the following beneficial effects: The geological adaptability has been significantly improved: it can pass through special geological conditions such as sand layers, pebbles, boulders, and caves, and anchor into medium and slightly weathered rock layers. The characteristic value of the compressive bearing capacity of a single pile reaches 2100kN, and the characteristic value of the horizontal component force is 1450kN, meeting the requirements of first-level foundation pit support.

[0016] Construction efficiency and economic advantages: Compared with traditional concrete internal supports, material consumption is reduced by more than 80%, no blasting or dismantling of supports is required, construction period is shortened by more than 30%, and construction costs are reduced by more than 40%.

[0017] Optimized space utilization and safety: The steel pipe inclined piles adopt a triangular support structure, which occupies a small space in the pit and the displacement of the support point is controllable (the soil reaction force in each working condition meets the requirements of the specification), avoiding safety hazards caused by stress release when the support is removed.

[0018] Green construction and functional reuse: Reduce the use of reinforced concrete. After the support is removed, the steel pipe piles can also be used as engineering piles, reducing resource consumption; the corbel-type water-stop steel plate structure effectively prevents leakage and improves the durability of the support system.

[0019] Flexible adaptability to working conditions: It can be set inside or outside the foundation pit, serving as a supporting member or replacing prestressed anchor cables. The barb structure enhances the pull-out resistance and adapts to different geological and support requirements. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Other features, objects and advantages of the present invention will become more apparent upon reading the detailed description of non-limiting embodiments with reference to the following drawings: Figure 1 This is a schematic diagram of deep foundation pit steel pipe inclined piles passing through pebbles and caves; Figure 2 Schematic diagram of the dismantling of steel pipe inclined piles in a deep foundation pit (the remaining steel pipe piles can provide the building with compressive and tensile bearing capacity); Figure 3 This is a schematic diagram of deep foundation pit steel pipe inclined piles passing through the silt layer; Figure 4 This is a schematic diagram of deep foundation pit steel pipe inclined piles passing through the isolated rock layer; Figure 5 Schematic diagram of deep foundation pit steel pipe inclined piles passing through pebbles and caves (instead of prestressed anchor cables); Figure 6 Schematic diagram of deep foundation pit steel pipe inclined piles passing through the silt layer (instead of prestressed anchor cables); Figure 7 Schematic diagram of deep foundation pit steel pipe inclined piles passing through the isolated rock layer (instead of prestressed anchor cables); Figure 8 This is a schematic diagram of node sample 1 (connection between steel pipe pile head and crown beam); Figure 9 This is a schematic diagram of node sample 2 (connection between steel pipe piles and building foundation slab); Figure 10 This is a schematic diagram of node sample 3 (connection of steel pipe piles with crown beam or waist beam); Figure 11 This is a schematic diagram of steel pipe casing (hoop) connection (used for non-rock formation steel pipe connection); Figure 12 This is a schematic diagram of the steel pipe butt welding connection sample (used for rock formation steel pipe connection); Figure 13 This is a schematic diagram of the steel pipe pile barb (used for steel pipe inclined piles to replace prestressed anchor cables to resist pullout in silt and sand layers); Figure 14 This is a diagram of a self-designed dual-tower impact drill rig with a working range of 45° to 90° (90° in this state) Figure 15 This is a diagram of a self-designed dual-tower impact drill rig with a working range of 45° to 90° (45° in this state); Figure 16 This is working condition 1 - excavation diagram; Figure 17 This is the working condition 2 - support diagram; Figure 18 This is the working condition 3 - excavation diagram; Figure 19 This is the schematic diagram of working condition 4 - adding rigid hinge (10.00m); Figure 20 This is the schematic diagram of working condition 5 - adding rigid hinge (4.5m); Figure 21 This is the schematic diagram of working condition 6 - dismantling the support. DETAILED DESCRIPTION

[0021] The present invention will be described in detail below with reference to the accompanying drawings and specific embodiments. The exemplary embodiments and descriptions of the present invention are used to explain the present invention but are not intended to limit the present invention.

[0022] It should be noted that all directional indications in the embodiments of the present invention (such as up, down, left, right, front, back, upper end, lower end, top, bottom...) are only used to explain the relative position relationship, movement status, etc. between the various components under a certain specific posture (as shown in the accompanying drawings). If the specific posture changes, the directional indication will also change accordingly.

[0023] In the present invention, unless otherwise specified or limited, the term "connection" should be understood in a broad sense. For example, "connection" can mean fixed connection, detachable connection, or integration; mechanical connection, electrical connection; direct connection, or indirect connection through an intermediate medium; internal communication between two elements, or interaction between two elements, unless otherwise specified. Those skilled in the art will understand the specific meanings of the above terms in the present invention based on specific circumstances.

[0024] In addition, the terms "first," "second," and so on, used in this disclosure are for descriptive purposes only and should not be construed as indicating or implying their relative importance or implicitly indicating the number of the technical features indicated. Therefore, features defined as "first" or "second" may explicitly or implicitly include at least one such feature. Furthermore, the technical solutions of various embodiments may be combined with each other, but only on the basis that they can be implemented by a person of ordinary skill in the art. If the combination of technical solutions contradicts or cannot be implemented, it shall be deemed that such a combination of technical solutions does not exist and is not within the scope of protection claimed by this disclosure.

[0025] The present invention will be further described in detail below with reference to the accompanying drawings.

[0026] Technical solution: refer to Figures 1 to 15 (1) Foundation pit support system structure Steel pipe inclined pile body The steel pipe inclined piles are constructed using Q355 steel with a diameter and wall thickness meeting the project's pre-determined specifications. No fewer than eight anchor bars are evenly distributed around the pile circumference, and the length of the anchor bars at the pile head meets design requirements (e.g., no less than 70 cm). The steel pipe inclined piles are connected using casing (hoops) in the soil layer and groove butt welding in the rock layer, forming a monolithic load-bearing structure.

[0027] Rock anchoring structure The steel pipe inclined piles are embedded in the rock formation at a predetermined angle of 45°-90°. The depth of penetration is determined by project requirements (for example, at least 3.5 meters into slightly weathered rock). The pile body is filled with cement grout or self-compacting underwater concrete to form the anchoring section. The cement grout is prepared using 42.5R ordinary Portland cement with a water-cement ratio of 0.5. The pile body compressive strength is not less than 30 MPa. The grouting pressure is 2.5 MPa to ensure that the steel pipe pile is firmly anchored in the rock formation.

[0028] Connection structure The steel pipe inclined piles are connected to the crown beam or basement floor via connecting members. When installed toward the inside of the foundation pit, a corbel-style water-stop steel plate is installed at the intersection with the basement floor. When installed toward the outside of the foundation pit, they are connected to the crown beam via steel corbels. When replacing prestressed anchor cables, barbs are installed in the non-rock section of the pile body to enhance pullout resistance.

[0029] (2) Construction method Construction preparation: The site is leveled and support pile construction is completed, and steel pipe piles that meet the design requirements are prepared (the soil layer section and the rock layer section are processed using different connection methods).

[0030] Drilling and anchoring: Use a double-tower percussion drill rig to drill holes at an angle of 45°-90°. After reaching the designed rock penetration depth, lower the grouting pipe to the bottom of the hole and lift it 50mm. Then pour cement slurry or concrete at a pressure of 2.5MPa.

[0031] Structural connection: Cast the crown beam and connect it to the top of the steel pipe inclined pile through a corbel-type water-stop steel plate or steel corbel to form an overall support system.

[0032] Earthwork and structural construction: Excavate earth in layers, and construct the basement structure and replace the support beams and slabs simultaneously; after the strength of the replacement support beams reaches 80%, remove the steel pipe inclined piles, and the steel pipe piles retained under the bottom slab will serve as the vertical load-bearing and anti-pullout components of the building.

[0033] Example: This invention utilizes rock-penetrating steel pipe inclined piles as diagonal braces for foundation pit support projects, resolving the problem that concrete pipe pile inclined braces and steel lattice inclined braces cannot penetrate sand layers, pebbles, boulders, karst caves, and other special geological conditions, and cannot penetrate medium- and slightly weathered rock. It can reduce the amount of internal support material used by over 80%, while also reducing the workload of later dismantling the support. The specific process is as follows: 1. The site is leveled and the support piles are completed; 2. The impact drill can be put into place; 3. Determine the position and angle of the steel pipe inclined piles; 4. Processing of steel pipe piles: The steel pipes are connected in sections of 6 meters. Casing (hoops) are used to connect the steel pipes in the soil section, and groove butt welding is used to connect the steel pipes in the rock section.

[0034] 6. Use impact drill with pipe to drill holes for steel pipe inclined piles; 7. Steel pipe inclined piles are poured with cement slurry or concrete; 8. Cast the crown beam on the top of the support pile and connect it with the top of the steel pipe inclined pile; 9. Earth excavation; 10. During basement floor construction, install corbel-type water-stop steel plates on the steel pipe inclined piles and connect them to the foundation floor; 11. Construction of the basement middle floor structure and replacement of support beams and slabs; 12. After the strength of the replacement support beam reaches 80%, the steel pipe inclined piles are removed and the construction is completed.

[0035] The construction method of the present invention adopts a construction process that is cross-constructed with the retaining piles, which greatly shortens the construction period; it can realize barrier-free excavation and basement structure construction; it does not require a large amount of reinforced concrete supports and column piles and other materials, and there is no need for blasting, demolition and cleaning of concrete in the later stage, which can significantly reduce construction costs; at the same time, it avoids the safety hazards and risks caused by stress release during support removal and cantilevering of retaining piles in the later stage, and can better ensure the overall construction safety.

[0036] Rock-entry steel pipe inclined piles are installed in rows toward the inside of the foundation pit, ensuring no impact on surrounding buildings and facilities while fully utilizing land resources. Their triangular structure allows them to penetrate moderately and slightly weathered rock formations, making them more reliable and safer. Furthermore, rock-entry steel pipe inclined piles can be installed in rows toward the outside, replacing prestressed anchor cables. These piles are suitable for use in geological conditions such as deep sand layers, pebbles, boulders, and caves, where prestressed anchor cables are impractical. 1. Computational Analysis

[0037] The calculation and analysis is carried out using a 10-meter-deep foundation pit and rock-penetrating steel pipe inclined piles as supports. The rock-penetrating steel pipe inclined piles have a diameter of 377mm, a wall thickness of 10mm, and are made of Q355: 1. Calculate total information: Standards and Regulations Technical Specification for Building Foundation Pit Support JGJ 120-2012 Internal force calculation method Incremental method Support structure safety level Level 1 <![CDATA[Importance coefficient γ0 of the retaining structure]]> 1.10 Foundation pit depth h(m) 10.000 Embedment depth (m) 1.500 Pile top elevation (m) 0.000 Pile material type reinforced concrete Concrete strength grade C30 Pile section type round └Pile diameter (m) 1.000 Pile spacing (m) 1.200 With or without crown beam have ├Crown beam width (m) 1.100 ├Crown beam height (m) 1.000 └Horizontal lateral stiffness (MN / m) 0.001 waterproof curtain have ├Waterproof curtain height (m) 8.000 └Waterproof curtain thickness (m) 0.600 Grading levels 0 Overload number 1 Horizontal concentrated forces on the supporting structure 0 2. Soil layer parameters: Layer number Soil type name Layer thickness (m) <![CDATA[Heavy (kN / m 3 )]]> <![CDATA[Bulk unit weight (kN / m 3 )]]> Cohesion (kPa) Internal friction angle (degrees) Cohesion underwater (kPa) Internal friction angle underwater (degrees) 1 Miscellaneous fill 1.99 18.0 8.0 12.00 14.00 12.00 14.00 2 silt 1.10 18.5 8.5 16.00 18.00 16.00 18.00 3 medium sand 1.80 19.0 9.3 0.00 30.00 0.00 30.00 4 pebble 1.70 18.0 8.0 0.00 45.00 0.00 45.00 5 silt 0.70 18.5 8.0 16.00 18.00 16.00 18.00 6 slightly weathered rock 5.50 24.0 14.0 450.00 34.00 450.00 34.00 3. Supporting information:

[0038] 4. Working condition information: Working condition number Working condition type Depth (m) Anchorage number 1 Excavation 1.500 --- 2 Add support --- 1. Internal support 3 Excavation 10.000 --- 4 Rigid hinge 10.000 --- 5 Rigid hinge 4.500 --- 6 Removal of support --- 1. Internal support 5. Calculation and analysis of each working condition like Figures 15 to 20 shown.

[0039] 6. Calculation results: The diameter of the steel pipe inclined pile is 377mm, the wall thickness is 10mm, and the material is Q355. According to the specification, the characteristic value of the bearing capacity of a single pile can be calculated as follows: The steel pipe inclined piles shall penetrate into the slightly weathered limestone for no less than 3.5m. The characteristic value of the compressive bearing capacity of a single pile is 2100kN, the characteristic value of the horizontal component force is 1450kN, and the design value is 1800kN.

[0040] Working condition 1: Ps = 570.316 ≤Ep = 12924.679, the soil reaction meets the requirements.

[0041] Working condition 2: Ps = 570.316 ≤Ep = 12924.679, the soil reaction meets the requirements.

[0042] Working condition 3: Ps = 153.756 ≤Ep = 3161.380, the soil reaction meets the requirements.

[0043] Working condition 4: Ps = 153.756 ≤Ep = 3161.380, the soil reaction meets the requirements.

[0044] Working condition 5: Ps = 153.756 ≤Ep = 3161.380, the soil reaction meets the requirements.

[0045] Working condition 6: Ps = 197.866 ≤Ep = 3161.380, the soil reaction meets the requirements.

[0046] Where: Ps is the resultant reaction force of the soil inside the foundation pit acting on the embedded section of the retaining member (kN); Ep is the resultant passive earth pressure acting on the embedded section of the retaining member (kN).

[0047] Project Cases: Taking a 10-meter-deep first-level safety level foundation pit as an example, the specific implementation of the present invention will be further described in conjunction with the accompanying drawings: (1) Construction of support system Steel pipe pile processing Q355 steel pipes with a diameter of 377mm and a wall thickness of 10mm are used and processed in 6-meter sections: the soil section is connected with casing (hoops), and the rock section is connected with 30° groove butt welding; 8 C20 steel bars are evenly welded around the pile, and the pile head anchor steel bar is 70cm long and is used to anchor the crown beam corbel.

[0048] Rock anchoring construction The twin-tower percussion drill rig can be put into position, adjusted to an angle of 60°, and drilled to a depth of 3.5m in slightly weathered rock; After lowering the grouting pipe to the bottom of the hole, lift it 50mm and inject 42.5R ordinary Portland cement slurry (water-cement ratio 0.5) at a pressure of 2.5MPa until pure slurry emerges from the hole mouth, forming an anchoring section with a compressive strength ≥30MPa.

[0049] Connection structure implementation The steel bars at the top of the steel pipe piles are anchored into the crown beam corbels (the crown beam is 1.1m wide and 1.0m high) and fixed with double-sided welding; A corbel-type water-stop steel plate is welded at the junction of the basement floor and the steel pipe piles. The size of the steel plate is the pile diameter + 500mm, and it is welded to the bottom plate steel bars to form a water-stop system.

[0050] (2) Construction process Preliminary procedures: site leveling → construction of C30 supporting cast-in-place piles (diameter 1.0m, spacing 1.2m) → casting of crown beams.

[0051] Construction of steel pipe inclined piles: drilling rig in place → determining pile position and angle → drilling holes with pipes → pouring cement slurry → connecting crown beams.

[0052] Earthwork and structural construction: Excavate in layers to a depth of 10 meters, simultaneously construct the basement floor and install the corbel-type water-stop steel plates; When constructing the middle floor structure, cast the replacement support beam plate (strength grade C30).

[0053] Removal of supports and functional reuse: After the strength of the replacement support beam reaches 80%, the steel pipe inclined piles are removed, and the remaining part under the bottom plate is used as the building's pull-out and compression piles, which are rigidly connected to the foundation structure.

[0054] (3) Working condition verification Through incremental calculation and analysis, when this support system is used in a 10-meter deep foundation pit: The characteristic value of the compressive bearing capacity of a single pile is 2100kN, and the characteristic value of the horizontal component force is 1450kN; The resultant soil reaction force Ps acting on the embedded section of the retaining element under all working conditions is less than the resultant passive earth pressure Ep (for example, in working condition 3, Ps = 153.756 kN ≤ Ep = 3161.380 kN), meeting the requirements of the Technical Code for Construction Foundation Pit Support JGJ 120-2012 and verifying the safety and reliability of the system.

[0055] In summary, the present invention has the following significant advantages over the prior art: 1. Compared with concrete pipe pile diagonal bracing, after the concrete pipe pile diagonal bracing is pressed, it will move greatly due to the compression of the soil, resulting in a relatively large displacement of a single support point, which seriously affects the stability of the foundation pit; the steel pipe diagonal pile is embedded in the rock layer, and the displacement of the support point is relatively small, which can effectively ensure the safety of the side wall of the foundation pit.

[0056] 2. The water-stopping connection between the concrete pipe pile diagonal support and the floor is limited, and the connection with the crown beam is not as convenient as steel pipes; the rock-penetrating steel pipe diagonal piles can be connected to the bottom plate by welding water-stop steel plates at any point, and the crown beam can be connected by welding multiple steel bars at the end of the rock-penetrating steel pipe diagonal piles. The process is simple and the construction is convenient.

[0057] 3. When concrete pipe piles are used in special geological conditions such as sand layers, pebbles, caves, and boulders, the construction of concrete pipe piles is difficult and increases the construction cost. Rock-penetrating steel pipe piles can penetrate special geological conditions such as sand layers, pebbles, caves, rock layers, and boulders, and be anchored in medium to slightly weathered rocks.

[0058] Because concrete pipe piles cannot penetrate moderately or slightly weathered rock, the characteristic bearing capacity of a single pile is low. This results in smaller spacing between concrete pipe piles, impacting excavation and building foundation construction, increasing construction costs and time. Rock-penetrating steel pipe piles can penetrate rock, and their characteristic bearing capacity is more than twice that of concrete pipe piles. The wide spacing between piles minimizes the impact on excavation and building foundation construction.

[0059] 5. Compared with the concrete pipe pile inclined bracing, the concrete pipe piles are connected by circular welding, and the connection between the piles is weak. The concrete inclined piles are easy to break when encountering a collision, which seriously affects the safety of the foundation pit. The rock-penetrating steel pipe inclined piles are connected by casing (hoops), which is simple and convenient to construct. After excavation, the connection position of the steel pipe inclined piles is safer and more reliable.

[0060] 6. Compared to mixed piles and steel lattice bracing, steel lattice bracing uses a drilling-first, then driving-in pile method, and cannot penetrate rock formations. The construction process is complex, and the cost is twice as high as rock-driven steel pipe bracing. The bearing capacity and stability are also lower, and they cannot penetrate sand layers, pebbles, caves, boulders, and other unusual geological conditions. Steel pipe bracing, on the other hand, uses a percussive drill with pipe, a simple construction method that allows it to penetrate moderately to slightly weathered rock formations. It has a higher bearing capacity, wider spacing, and better stability, minimizing the impact on underground building structures. This significantly reduces construction time, material usage, and costs.

[0061] 7. Reduce the risk of increased project costs due to safety hazards caused by stress release and cantilevered support piles during later demolition.

[0062] 8. When the rock-penetrating steel pipe inclined piles are set from a row of piles to the inside of the foundation pit, they will not affect the buildings and facilities around the foundation pit; when they are set from a row of piles to the outside of the foundation pit instead of prestressed anchor cables, they can be anchored into medium and slightly weathered rock strata, with higher pull-out bearing capacity, and are safer and more reliable.

[0063] 9. Rock-penetrating steel pipe inclined piles can be used in special geological conditions such as sand layers, pebbles, boulders, and caves. They can enter medium and slightly weathered rock layers. The angle can be adjusted within the range of 45°~90°, and they have strong applicability.

[0064] 10. Compared with traditional methods, it can reduce a large number of reinforced concrete internal supports and column piles, and there is no need for blasting, demolition and cleaning of concrete in the later stage, which significantly shortens the construction period and reduces costs.

[0065] 11. After the support is removed, the rock-penetrating steel pipe inclined piles retained under the base plate can be used as the vertical bearing and pull-out resistance of the building.

[0066] 12. When using rock-penetrating steel pipe inclined piles instead of prestressed anchor cables, barbs are set in non-rock geological locations to increase the pull-out bearing capacity of the rock-penetrating steel pipe inclined piles and ensure the safety of the foundation pit.

[0067] 13. The use of impact drills with pipes for rock-penetrating steel pipe inclined pile construction has the characteristics of strong rock penetration ability, fast drilling speed, dry drilling, etc., and higher stability; it ensures the safety and civilization of the construction site; it can also be applied to slope support.

[0068] This foundation pit support system, featuring tensile and compression-resistant steel pipe oblique piles driven into the rock, utilizes percussive drilling rigs with pipes to penetrate moderately and slightly weathered rock formations. It addresses the impact of the pile-and-anchor system on surrounding buildings and facilities, as well as the impact of the pile-and-internal support system on underground building construction. It also addresses the difficulties encountered by concrete pipe piles and mixing piles plus steel lattice bracing in penetrating deep sand layers, pebbles, boulders, and karst caves, as well as the inability to penetrate the rock. Rock-penetrating steel pipe oblique piles significantly reduce construction difficulty, improve efficiency, reduce resource loss, and conserve substantial amounts of concrete, rebar, and steel. They are environmentally friendly and energy-efficient, making them widely applicable to deep foundation pit support projects in various geological conditions, with significant economic and social value.

[0069] The technical solutions provided by the embodiments of the present invention are introduced in detail above. Specific examples are used herein to illustrate the principles and implementation methods of the embodiments of the present invention. The description of the above embodiments is only applicable to help understand the principles of the embodiments of the present invention. At the same time, for those skilled in the art, according to the embodiments of the present invention, there may be changes in the specific implementation methods and application scopes. In summary, the contents of this specification should not be understood as limiting the present invention.

Claims

1. The foundation pit support system with anti-tension and anti-compression steel pipe oblique piles embedded in the rock is characterized by: include: Steel pipe inclined piles, wherein anchor steel bars are arranged along the circumference of the piles, and the length of the anchor steel bars at the pile head meets the design requirements; In the rock anchoring structure, the steel pipe inclined pile is embedded in the rock layer at a predetermined angle, and the pile body is poured with solidifying material to form an anchoring section; The connection structure is that the steel pipe inclined pile is connected to the crown beam or the basement floor through a connection member.

2. The foundation pit support system for anti-tension and anti-compression steel pipe oblique piles embedded in rock according to claim 1 is characterized by: The steel pipe inclined piles are made of Q355 steel, with diameter and wall thickness meeting the predetermined specifications of the project. No less than 8 anchor steel bars are evenly distributed around the pile, and the length of the anchor steel bars at the pile head is no less than 70 cm.

3. The foundation pit support system for anti-tension and anti-compression steel pipe oblique piles embedded in rock according to claim 1 is characterized by: The predetermined angle is 45°-90°, and the solidifying material is cement slurry or self-compacting underwater concrete, wherein the cement slurry is prepared with 42.5R ordinary Portland cement with a water-cement ratio of 0.5, the pile body compressive strength is not less than 30MPa, and the grouting pressure is 2.5MPa.

4. The foundation pit support system for anti-tension and anti-compression steel pipe oblique piles driven into rock according to claim 1 is characterized by: The soil layer section of the steel pipe inclined pile is connected by casing, and the rock layer section is connected by groove butt welding. The depth of embedding in the slightly weathered rock is not less than 3.5m, and the characteristic value of the compressive bearing capacity of a single pile is not less than 2100kN.

5. The foundation pit support system for anti-tension and anti-compression steel pipe oblique piles embedded in rock according to claim 1 is characterized by: When the steel pipe inclined pile is arranged toward the outside of the foundation pit, a barb structure is provided in the non-rock layer section of the pile body, and the connecting member includes a corbel-type water-stop steel plate or a steel corbel.

6. A construction method of a foundation pit support system according to any one of claims 1 to 5, characterized in that: The following steps are involved: Step S1: leveling the site and completing the support pile construction; Step S2: The impact drill is positioned to determine the position of the steel pipe inclined pile according to a predetermined angle; Step S3: Processing steel pipe piles, with different connection methods used for the soil layer section and the rock layer section; Step S4: drilling with a drill rig and pipe to a designed rock penetration depth; Step S5, pouring curing material to solidify the pile body; Step S6: Cast the crown beam and connect it to the top of the steel pipe inclined pile through a connecting member; Step S7: excavating earth in layers and constructing the basement structure; Step S8: After the strength of the support beam to be replaced reaches 80%, the steel pipe inclined piles are removed.

7. The construction method according to claim 6, characterized in that: The percussion drilling rig has a double-tower structure and can realize construction at an angle of 45°-90°. When drilling, the grouting pipe is lowered to the bottom of the hole and then lifted 50mm. Grouting is carried out at a pressure of 2.5MPa until pure grout emerges from the hole mouth.

8. The construction method according to claim 6, characterized in that: A corbel-type water-stopping steel plate is provided at the junction of the steel pipe inclined pile and the basement bottom plate, and the steel plate is welded to the foundation bottom plate to form a water-stopping structure.

9. The construction method according to claim 6, characterized in that: After the support is removed, the steel pipe inclined piles retained under the bottom plate serve as the vertical load-bearing and anti-pullout components of the building and are rigidly connected to the foundation structure.

10. The construction method according to claim 6, characterized in that: When the steel pipe inclined pile replaces the prestressed anchor cable, a barb structure is welded in the non-rock layer section. The barbs are symmetrically arranged around the pile, double-sided welded, and the welding length is not less than 5 times the diameter of the steel bar.

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