A precast pile uplift bearing capacity reinforcing mechanism
By adding reinforcing piles at the lower end of precast piles and using grouting technology to form lower and upper grouting bodies, the problem of insufficient pull-out resistance of precast piles at the junction of hard and soft soil layers was solved, improving the stability and bearing capacity of the pile foundation and achieving low-cost construction efficiency.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- SHANGHAI GEOTECHN INVESTIGATIONS & DESIGN INST
- Filing Date
- 2025-07-31
- Publication Date
- 2026-07-24
AI Technical Summary
Precast piles have insufficient tensile bearing capacity at the interface between hard and soft soil layers, which can lead to damage to the pile body or pile end connection, affecting structural safety. Furthermore, traditional reinforcement methods are costly or have limited effectiveness.
A reinforcing pile is added to the lower end of the precast pile, and a lower grouting body is formed between the reinforcing pile and the hard subsoil through grouting technology. Combined with the pile end and pile side grouting process, an upper grouting body is formed to enhance the pile-soil bond and integrity.
It improves the pull-out bearing capacity and stability of pile foundations, overcomes the stress concentration problem, and is efficient and cost-controllable in construction.
Smart Images
Figure CN224549095U_ABST
Abstract
Description
Technical Field
[0001] This utility model relates to the field of pile foundation engineering technology, and in particular to a mechanism for strengthening the pull-out bearing capacity of precast piles. Background Technology
[0002] In construction engineering, precast piles (such as precast pipe piles) are widely used in foundation treatment due to their advantages such as convenient construction and stable quality. However, when the pile tip is located in a hard stratum (such as strongly weathered rock or dense gravel), although the pile tip bearing capacity is high, the uplift bearing capacity of the pile body is often insufficient due to the soft soil layer (such as silt, loose fill, etc.) covering it. This makes the pile prone to failure under uplift loads, affecting structural safety. In addition, when the bearing stratum of the pile foundation has large undulations and the depth of the pile foundation into the bearing stratum is limited, pile foundation stability problems may also exist.
[0003] Traditional solutions typically improve pull-out resistance by increasing pile length, expanding pile diameter, or installing pile side grouting, or by using pilot holes to increase the depth of the bearing layer. However, these methods have problems such as high construction costs, low efficiency, or limited effectiveness. In addition, if only the structural strength of the precast pile itself is relied upon, stress concentration is easily formed at the junction of the hard subsoil and the soft soil layer, which can lead to damage to the pile body or the pile end connection.
[0004] To address the aforementioned problems, this invention proposes a precast pile tensile strength enhancement mechanism that can improve pile foundation stability at low cost and avoid stress concentration at the junction of hard and soft soil layers. Utility Model Content
[0005] To address the problems existing in the above-mentioned solutions for improving the pull-out resistance of foundation piles, this utility model provides a mechanism for strengthening the pull-out bearing capacity of precast piles.
[0006] According to one objective of this utility model, this utility model provides a mechanism for enhancing the pull-out bearing capacity of precast piles, wherein the stratum comprises a hard lower soil layer and a soft upper soil layer distributed from bottom to top, and the pull-out bearing capacity enhancement mechanism comprises:
[0007] A tubular precast pile is pressed into the soft upper soil layer, with the lower end of the precast pile located between the hard lower soil layer and the soft upper soil layer. The inner wall of the precast pile is pre-embedded with a grouting channel connecting the upper and lower ends of the precast pile.
[0008] A tubular reinforcing pile is constructed in which a through-hole is formed in the hard subsoil below the pile tip of the precast pile. The reinforcing pile is positioned to be vertically lowered into the through-hole through the interior of the precast pile. The lower end of the reinforcing pile is located at the lower end of the through-hole, and the upper end of the reinforcing pile is located inside the precast pile. An upper annular gap is formed between the reinforcing pile and the precast pile, and a lower annular gap is formed between the reinforcing pile and the through-hole.
[0009] The lower annular void is densely filled with lower grout, which consolidates the reinforcing pile and the hard subsoil to form a composite bearing structure. The upper annular void is densely filled with upper grout, and grout is injected through the grouting channel between the lower end of the precast pile and the stratum to form a pile end grout.
[0010] Preferably, the precast pile is a precast pipe pile or a precast hollow square pile.
[0011] Preferably, the reinforcing pile is a steel pipe pile or a square steel pile.
[0012] Preferably, the grouting body is a grouting body formed by pressurized cement grouting.
[0013] Preferably, the reinforcing pile has a lower grout outlet hole that connects to the lower annular gap, and a lower grouting pipe is provided on the inner side of the reinforcing pile. The upper end of the lower grouting pipe is exposed above the reinforcing pile, and the lower end of the lower grouting pipe is connected to the lower grout outlet hole.
[0014] Preferably, multiple sets of lower grout outlet holes are provided along the length direction of the reinforcing pile, and multiple lower grout outlet holes are provided in each set. The lower grout outlet holes in each set are equally spaced along the circumference of the reinforcing pile, and the lower grout outlet holes are arranged close to the lower end of the reinforcing pile.
[0015] Preferably, the upper grouting body is formed by grouting and compacting concrete or high-strength grouting material.
[0016] Preferably, the lower end of the precast pile is provided with a pile end grout outlet hole that connects to the grouting channel, and the pile end grouting body is a pile end grouting body formed by cement grout diffusing through the pile end grout outlet hole to the lower end of the precast pile and the surrounding strata.
[0017] Preferably, a pile end grouting pipe is installed inside the grouting channel, and multiple grouting channels are spaced apart in the circumferential direction of the precast pile.
[0018] Compared with the prior art, the beneficial effects of this utility model are:
[0019] The pull-out bearing capacity strengthening mechanism of this precast pile is to add a reinforcing pile at the lower end of the precast pile, so that it penetrates into the hard subsoil. The lower grout body is formed by high pressure grouting technology, which enhances the bond between the reinforcing pile and the hard subsoil. The reinforcing pile not only provides additional pull-out bearing capacity, but also forms a combined structure with the precast pile to share the load and increase the stability of the pile foundation.
[0020] By using post-grouting technology at the pile tip and pile side to form an upper grouting body and a pile tip grouting body, the cracks in the soil and rock are further filled, improving the integrity and bearing capacity of the pile-soil system and overcoming the problem of stress concentration at the interface between hard and soft soil layers.
[0021] The present invention will be further described below with reference to the accompanying drawings and embodiments. Attached Figure Description
[0022] Figure 1 This is an overall schematic diagram of the pull-out bearing capacity strengthening mechanism of a precast pile according to the present invention;
[0023] Figure 2 for Figure 1 Schematic diagram of the AA section;
[0024] Figure 3 for Figure 2 Schematic diagram of the BB cross section;
[0025] Figure 4 This is a schematic diagram of the construction conditions of the precast pile pull-out bearing capacity strengthening mechanism described in this utility model.
[0026] Figure 5 This is a schematic diagram of the second construction condition of the precast pile pull-out bearing capacity strengthening mechanism described in this utility model;
[0027] Figure 6 This is a schematic diagram of three construction conditions for the precast pile pull-out bearing capacity strengthening mechanism described in this utility model;
[0028] Figure 7 This is a schematic diagram of the construction conditions of the precast pile pull-out bearing capacity strengthening mechanism described in this utility model.
[0029] Figure 8 This is a schematic diagram of the fifth construction condition of the precast pile pull-out bearing capacity strengthening mechanism described in this utility model;
[0030] Figure 9 This is a schematic diagram of the construction conditions of the precast pile pull-out bearing capacity strengthening mechanism described in this utility model. Detailed Implementation
[0031] The following description is intended to provide a detailed account of the present invention so that those skilled in the art can implement it. The preferred embodiments described below are merely examples, and other obvious variations will occur to those skilled in the art. The basic principles of the present invention defined in the following description can be applied to other embodiments, modifications, improvements, equivalents, and other technical solutions that do not depart from the spirit and scope of the present invention.
[0032] Please see Figure 1-9 This utility model provides a technical solution: a mechanism for strengthening the pull-out bearing capacity of a precast pile, wherein the stratum includes a hard lower soil layer and a soft upper soil layer distributed from bottom to top, and the pull-out bearing capacity strengthening mechanism 1 includes:
[0033] A tubular precast pile 2 is pressed into the soft upper soil layer. The lower end of the precast pile 2 is located between the hard lower soil layer and the soft upper soil layer. The inner wall of the precast pile 2 is pre-embedded with a grouting channel 9 connecting the upper and lower ends of the precast pile 2.
[0034] A tubular reinforcing pile 3 is formed in the hard subsoil below the pile end of the precast pile 2 by drilling to form a through-hole 8. The reinforcing pile 3 is configured to be vertically lowered into the through-hole 8 through the interior of the precast pile 2. The lower end of the reinforcing pile 3 is located at the lower end of the through-hole 8, and the upper end of the reinforcing pile 3 is located inside the precast pile 2. An upper annular gap 4 is formed between the reinforcing pile 3 and the precast pile 2, and a lower annular gap 10 is formed between the reinforcing pile 3 and the through-hole 8.
[0035] The lower annular void 10 is densely filled with a lower grouting body 11, which consolidates the reinforcing pile 3 and the hard lower soil to form a composite bearing structure. The upper annular void 4 is densely filled with an upper grouting body 12, and a pile end grouting body 13 is formed by grouting through the grouting channel 9 between the lower end of the precast pile 2 and the stratum.
[0036] In this embodiment, the precast pile 2 is a precast pipe pile or a precast hollow square pile, and the reinforcing pile 3 is a steel pipe pile or a square steel pile.
[0037] The lower grouting body 11 is formed by pressurized cement grouting. The grouting pressure and grout ratio are adjusted according to the geological conditions. Specifically, the reinforcing pile 3 is provided with a lower grout outlet hole 5 that connects to the lower annular gap 10. A lower grouting pipe 6 is provided on the inner side of the reinforcing pile 3. The upper end of the lower grouting pipe 6 is exposed above the reinforcing pile 3, and the lower end of the lower grouting pipe 6 is connected to the lower grout outlet hole 5.
[0038] Multiple sets of lower grout outlet holes 5 are arranged along the length direction of the reinforcing pile 3. Each set contains multiple lower grout outlet holes 5. The lower grout outlet holes 5 in each set are equally spaced along the circumference of the reinforcing pile 3. The lower grout outlet holes 5 are arranged close to the lower end of the reinforcing pile 3. Preferably, the number of lower grout outlet holes 5 in each set is 4.
[0039] The upper grouting body 12 is formed by grouting and compacting concrete or high-strength grout.
[0040] The lower end of the precast pile 2 is provided with a grout outlet hole that connects to the grouting channel 9. The grouting body 13 is formed by cement grout diffusing through the grout outlet hole to the lower end of the precast pile 2 and the surrounding strata, thereby enhancing the pile end bearing capacity and side friction resistance. Specifically, a pile end grouting pipe 7 is installed inside the grouting channel 9. Furthermore, multiple grouting channels 9 are spaced apart around the circumference of the precast pile 2.
[0041] The construction of the pull-out bearing capacity strengthening mechanism for this precast pile includes the following steps:
[0042] S1. See also Figure 4 On the ground, a pile driving device is used to drive the precast pile 2, which is a precast pipe pile or a precast hollow square pile, vertically into the soil layer until the predetermined design elevation is reached.
[0043] S2. See also Figure 5 At the lower center of the precast pile 2, a down-the-hole hammer or geological drilling rig is used to penetrate the rock layer or hard subsoil at the bottom of the pile and drill to the predetermined elevation to form a through hole 8. The hole diameter must match the size of the subsequent reinforcing pile 3.
[0044] S3. See also Figure 6 High-pressure water guns or mechanical hole cleaning equipment are used to remove the mud and sediment adhering to the inner wall of the precast pile 2 core to ensure the inner wall is clean and avoid affecting the installation of the reinforced pile 3 and the grouting bonding effect.
[0045] S4. See also Figure 7 The pre-processed reinforcing pile 3 is a steel pipe pile or a square steel pile. The reinforcing pile 3 is lowered vertically along the center hole of the precast pile 2 until the bottom of the reinforcing pile 3 reaches the bottom elevation of the through hole 8. The pile body of the reinforcing pile 3 is opened with the grout outlet hole 5 according to the design requirements to facilitate subsequent grouting diffusion.
[0046] S5. See also Figure 8 Cement grout is injected under high pressure into the lower annular gap 10 between the reinforcing pile 3 and the through hole 8 through the pre-embedded lower grouting pipe 6 inside the reinforcing pile 3. The grout is filled and consolidated into the surrounding rock and soil to form a composite bearing structure. The grouting pressure and grout ratio need to be adjusted according to the geological conditions.
[0047] S6. See also Figure 9 Concrete or high-strength grout is poured into the upper annular gap 4 between the precast pile 2 and the reinforced pile 3 to ensure that the two are stressed together. The filling should be carried out continuously and compacted by vibration.
[0048] S7. See also Figure 9 Cement grout is injected into the bottom of the precast pile 2 through the grouting channel 9 and the grouting pipe 7 embedded in the precast pile 2. The grout diffuses to the pile end and the surrounding soil layer through the grout outlet hole on the pile end of the precast pile 2, thereby enhancing the bearing capacity and side friction of the pile end.
[0049] In summary, the tensile bearing capacity enhancement mechanism of this precast pile is to add a reinforcing pile 3 at the lower end of the precast pile 2, so that it penetrates into the hard subsoil, and form a lower grout body 11 through high-pressure grouting technology, which enhances the bond between the reinforcing pile 3 and the hard subsoil. The reinforcing pile 3 not only provides additional tensile bearing capacity, but also forms a combined structure with the precast pile 2 to share the load and increase the stability of the pile foundation.
[0050] Meanwhile, by using the post-grouting process at the pile tip and pile side to form the upper grouting body 12 and the pile tip grouting body 13, the cracks in the rock and soil are further filled, improving the integrity and bearing capacity of the pile-soil system and overcoming the problem of stress concentration at the junction of hard soil layer and soft soil layer.
[0051] This technology effectively solves the problem of insufficient pull-out resistance of traditional precast piles in "soft upper and hard lower" strata, or the instability caused by insufficient depth of pile tip into the bearing layer. It also has advantages such as high construction efficiency, controllable cost, and significant improvement in bearing capacity.
[0052] The embodiments described above are only used to illustrate the technical ideas and features of this utility model. Their purpose is to enable those skilled in the art to understand the content of this utility model and implement it accordingly. The scope of patent application of this utility model should not be limited by these embodiments. That is, any equivalent changes or modifications made in accordance with the spirit disclosed in this utility model still fall within the patent scope of this utility model.
Claims
1. A mechanism for strengthening the pull-out bearing capacity of precast piles, wherein the strata comprise a hard lower layer of soil and a soft upper layer of soil distributed from bottom to top, characterized in that, The pull-out bearing capacity strengthening mechanism (1) includes: A tubular precast pile (2) is pressed into the soft upper soil layer. The lower end of the precast pile (2) is located between the hard lower soil layer and the soft upper soil layer. The inner wall of the precast pile (2) is pre-embedded with a grouting channel (9) connecting the upper and lower ends of the precast pile (2). A tubular reinforcing pile (3) is formed in the hard subsoil below the pile end of the precast pile (2) through a drilled hole (8). The reinforcing pile (3) is configured to be vertically lowered into the through hole (8) through the interior of the precast pile (2). The lower end of the reinforcing pile (3) is located at the lower end of the through hole (8), and the upper end of the reinforcing pile (3) is located inside the precast pile (2). An upper annular gap (4) is formed between the reinforcing pile (3) and the precast pile (2), and a lower annular gap (10) is formed between the reinforcing pile (3) and the through hole (8). The lower annular void (10) is densely filled with a lower grouting body (11), which consolidates the reinforcing pile (3) and the hard lower soil to form a composite bearing structure. The upper annular void (4) is densely filled with an upper grouting body (12), and the lower end of the precast pile (2) and the stratum are grouted through the grouting channel (9) to form a pile end grouting body (13).
2. The precast pile pull-out bearing capacity strengthening mechanism according to claim 1, characterized in that, The precast pile (2) is a precast pipe pile or a precast hollow square pile.
3. The precast pile pull-out bearing capacity strengthening mechanism according to claim 1, characterized in that, The reinforcing pile (3) is a steel pipe pile or a square steel pile.
4. The precast pile pull-out bearing capacity strengthening mechanism according to claim 1, characterized in that, The lower grout body (11) is formed by pressurized grouting of cement slurry.
5. A precast pile pull-out bearing capacity strengthening mechanism according to claim 1, characterized in that, The reinforcing pile (3) has a lower grout outlet (5) that connects to the lower annular gap (10). A lower grouting pipe (6) is provided on the inner side of the reinforcing pile (3). The upper end of the lower grouting pipe (6) is exposed above the reinforcing pile (3). The lower end of the lower grouting pipe (6) is connected to the lower grout outlet (5).
6. A precast pile pull-out bearing capacity strengthening mechanism according to claim 5, characterized in that, Multiple sets of the lower grout outlet holes (5) are provided along the length direction of the reinforcing pile (3). Each set contains multiple lower grout outlet holes (5). The lower grout outlet holes (5) in each set are equally spaced along the circumference of the reinforcing pile (3). The lower grout outlet holes (5) are positioned close to the lower end of the reinforcing pile (3).
7. A precast pile pull-out bearing capacity strengthening mechanism according to claim 1, characterized in that, The upper grouting body (12) is formed by grouting and compacting concrete or high-strength grout.
8. A precast pile pull-out bearing capacity strengthening mechanism according to claim 1, characterized in that, The lower end of the precast pile (2) is provided with a grout outlet hole that connects to the grouting channel (9). The grouting body (13) at the pile end is formed by cement grout spreading through the grout outlet hole to the lower end of the precast pile (2) and the surrounding strata.
9. A precast pile pull-out bearing capacity strengthening mechanism according to claim 8, characterized in that, The grouting channel (9) is provided with a pile end grouting pipe (7), and multiple grouting channels (9) are provided at intervals around the precast pile (2).