An end bearing plastic supporting pile composite pile foundation

Abstract

The utility model relates to the technical field of foundation engineering, disclose a kind of end bearing plastic supporting pile composite pile foundation, comprising: end bearing rigid pile;Located the pile foundation platform of end bearing rigid pile upper part;Foamed concrete layer is located at the pile end of end bearing rigid pile;Wherein, the foamed concrete layer is applied lateral restraint, so that it has yield and densification characteristics when bearing the vertical pressure transmitted by end bearing rigid pile.The utility model in the end bearing rigid pile pile end is provided with the foamed concrete layer of being restrained, when the stress of rigid pile pile end is less than the yield strength of foamed concrete layer, foamed concrete layer is in elastic stage, and deformation is very small;When the stress of rigid pile pile end is greater than the yield strength of foamed concrete layer, foamed concrete layer has obvious yield deformation, but stress is basically unchanged, and rigid pile produces obvious settlement deformation downward, but bearing capacity is basically unchanged, and subsequent load is borne by foundation soil, reaches the effect of plastic supporting pile.

Description

Technical Field

[0001] This utility model relates to the field of foundation engineering technology, and in particular to a composite pile foundation with end-bearing plastic support piles. Background Technology

[0002] In foundation engineering, composite pile foundations are often used to fully utilize the bearing capacity of the natural soil beneath the pile cap. However, when using traditional end-bearing pile foundations, because the stiffness of the pile body is much greater than that of the soil between the piles, most of the load from the superstructure is directly transferred to the bearing layer at the pile ends through the pile body. This results in the soil between the piles below the pile cap bearing only a very small proportion of the load, significantly wasting its bearing potential and failing to achieve true pile-soil interaction, thus reducing the overall economic efficiency of the foundation.

[0003] To address the problem of uneven load distribution between piles and soil, the engineering community proposed the concept of plastic-bearing piles. The core mechanism is to allow the pile to undergo plastic deformation after reaching a certain load level, thereby transferring subsequent incremental loads to the soil between the piles. However, this concept is traditionally achieved through friction piles, which rely on the pile tip penetrating the soil and causing settlement after the pile's side friction reaches its limit. This method severely limits the application scenarios of plastic-bearing piles, especially in karst geological areas common in southern my country, where the overlying soil layer is often thin or lacks sufficient bearing capacity. The pile foundation must be supported by a hard, moderately weathered rock layer, making friction-bearing plastic piles unsuitable in these situations. This results in significant regional and geological limitations to the application of this technology.

[0004] Furthermore, even for traditional friction-type plastic bearing piles, the triggering and development of plastic deformation is highly dependent on complex pile-soil interactions, and the development of pile side friction is affected by various uncertainties such as geological conditions and construction quality. This makes it difficult for engineers to accurately preset and control the load value and deformation amount at which the pile body begins to undergo plastic deformation. There is a lack of an active, reliable, and easily quantifiable design method to regulate the stress and deformation behavior of pile foundations, posing challenges to the accuracy and reliability of engineering design. Utility Model Content

[0005] The purpose of this invention is to address the shortcomings of existing technologies and propose an end-bearing plastic support pile composite pile foundation.

[0006] To achieve the above objectives, this utility model adopts the following technical solution: an end-bearing plastic-supported composite pile foundation, comprising: End-bearing rigid piles; The pile cap located on top of the end-bearing rigid pile; The foamed concrete layer located at the end of the end-bearing rigid pile; The foamed concrete layer is laterally constrained so that when subjected to the vertical pressure transmitted by the end-bearing rigid pile, its stress-strain relationship exhibits three-stage characteristics: an elastic segment, a yield plateau segment, and a densification and strengthening segment.

[0007] As a further description of the above technical solution: The foamed concrete layer is embedded in the moderately weathered rock layer, and the moderately weathered rock layer applies the lateral constraint to it.

[0008] As a further description of the above technical solution: The foamed concrete layer is disposed within the constraint sleeve, and the lateral constraint is applied to it through the constraint sleeve.

[0009] As a further description of the above technical solution: The constraint sleeve is a steel sleeve, and the lower end of the constraint sleeve rests on the top surface of the moderately weathered rock layer.

[0010] As a further description of the above technical solution: The end-bearing rigid pile is a reinforced concrete cast-in-place pile.

[0011] As a further description of the above technical solution: The cross-sectional dimension of the foamed concrete layer is greater than or equal to the cross-sectional dimension of the end-bearing rigid pile.

[0012] As a further description of the above technical solution: The end-bearing rigid piles can be alternately arranged with conventional friction rigid piles under the pile cap.

[0013] This utility model has the following beneficial effects: 1. In this utility model, by setting a constrained foamed concrete layer at the pile end of the end-bearing rigid pile, when the stress at the pile end of the end-bearing rigid pile is less than the yield strength of the foamed concrete layer, the foamed concrete layer is in the elastic stage and the deformation is very small; when the stress at the pile end of the end-bearing rigid pile is greater than the yield strength of the foamed concrete layer, the foamed concrete layer undergoes obvious yield deformation but the stress remains basically unchanged, the end-bearing rigid pile undergoes obvious settlement deformation downward but the bearing capacity remains basically unchanged, and the subsequent increased load is borne by the foundation soil, thus achieving the effect of a plastic support pile.

[0014] 2. In this utility model, by setting a foamed concrete layer at the end of the end-bearing rigid pile, when the stress at the pile end is greater than the yield strength of the foamed concrete layer, the foamed concrete layer undergoes plastic deformation. The stress remains basically unchanged, but the deformation increases significantly, thereby coordinating the pile-soil deformation. This expands the application range of friction-type plastic support piles to end-bearing plastic support piles.

[0015] 3. In this utility model, the yield strength of the foamed concrete layer can be determined according to the designed pile end bearing capacity, and the thickness can be determined according to the pile end settlement requirements and the yield strain of the foamed concrete, which has good engineering applicability. Attached Figure Description

[0016] Figure 1 This is a schematic diagram of the internal structure of an end-bearing plastic support pile composite pile foundation proposed in this utility model; Figure 2 This utility model provides a plan view of the frame columns and pile locations for an end-bearing plastic-supported composite pile foundation. Figure 3 Typical stress-strain test curves for foamed concrete embedded in moderately weathered rock layers under pressure.

[0017] Legend: 1. Foamed concrete layer; 2. End-bearing rigid pile; 3. Friction rigid pile; 4. Soil between piles; 5. Moderately weathered rock layer; 6. Pile cap; 7. Constraint sleeve; 8. Frame column. Detailed Implementation

[0018] The technical solutions of the present utility model will be clearly and completely described below with reference to the accompanying drawings of the embodiments. Obviously, the described embodiments are only some embodiments of the present utility model, and not all embodiments. Based on the embodiments of the present utility model, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the protection scope of the present utility model.

[0019] Example: A composite pile foundation with end-bearing plastic support includes: End-bearing rigid pile 2; The pile cap 6 is located on top of the end-bearing rigid pile 2; Foamed concrete layer 1 located at the end of end-bearing rigid pile 2; Among them, the foamed concrete layer 1 is subjected to lateral restraint so that when it is subjected to the vertical pressure transmitted by the end-bearing rigid pile 2, its stress-strain relationship exhibits three-stage characteristics: elastic segment, yield plateau segment, and dense strengthening segment.

[0020] The foamed concrete layer 1 is embedded in the moderately weathered rock layer 5, and the moderately weathered rock layer 5 applies lateral restraint to it.

[0021] The foamed concrete layer 1 is placed inside the constraint sleeve 7, and lateral constraints are applied to it through the constraint sleeve 7.

[0022] The constraint sleeve 7 is a steel sleeve, and the lower end of the constraint sleeve 7 sits on the top surface of the moderately weathered rock layer 5.

[0023] End-bearing rigid pile 2 is a reinforced concrete cast-in-place pile.

[0024] The cross-sectional dimension of the foamed concrete layer 1 is greater than or equal to the cross-sectional dimension of the end-bearing rigid pile 2.

[0025] End-bearing rigid piles 2 can be alternately arranged with conventional friction rigid piles 3 under the pile cap 6.

[0026] Example 1: Reference Figure 1-3 This embodiment provides an end-bearing plastic bearing composite pile foundation. The composite pile foundation is mainly built under geological conditions where moderately weathered rock layer 5 is the main bearing layer, and its upper part is covered by soil between piles 4.

[0027] The core structure of the composite pile foundation includes, from bottom to top, a foamed concrete layer 1, end-bearing rigid piles 2, and a pile cap 6 located on top of all the end-bearing rigid piles 2.

[0028] The pile cap 6 is a component that connects the superstructure and the lower pile foundation. It is usually made of reinforced concrete. Its function is to distribute the load transmitted from the upper frame column 8 evenly to the multiple end-bearing rigid piles 2, friction rigid piles 3 and the soil between piles 4 below it.

[0029] The end-bearing rigid pile 2 is the main vertical component that bears and transmits loads. In this embodiment, it is preferably a reinforced concrete cast-in-place pile, and its cross-section can be designed as circular or square according to engineering requirements. The main body of the end-bearing rigid pile 2 is located in the soil between piles 4, and its pile end is connected to the bearing layer, i.e., the moderately weathered rock layer 5, through a foamed concrete layer 1.

[0030] The key technology of this embodiment lies in the construction of a foamed concrete layer 1. The foamed concrete layer 1 is located at the bottom of the end-bearing rigid pile 2. To achieve its special mechanical function, during construction, a hole must first be drilled to a predetermined depth within the moderately weathered rock layer 5, forming a cavity with a bottom and sidewalls made of rock. Then, foamed concrete is poured into this cavity to form the foamed concrete layer 1. In this way, the foamed concrete layer 1 is surrounded laterally and basally by the hard moderately weathered rock layer 5, and its lateral deformation is strongly constrained.

[0031] This lateral constraint is a prerequisite for achieving the technical effects of this utility model. (Refer to...) Figure 3 The typical stress-strain curve of foamed concrete shows that when the lateral deformation of the foamed concrete is effectively constrained, it exhibits three distinct stages when subjected to vertical pressure from the end-bearing rigid pile 2: Elastic stage: In the initial stage of loading, the stress at the pile tip is less than the yield strength of the foamed concrete. At this time, the stress and strain are roughly linearly related, the deformation of the foamed concrete layer 1 is very small, and the entire pile exhibits the characteristics of a traditional end-bearing rigid pile.

[0032] Yield plateau stage: When the stress at the pile tip reaches and exceeds the yield strength of the foamed concrete, its internal porous structure begins to be compressed and destroyed, resulting in irreversible plastic deformation. During this stage, the strain, i.e., the vertical compression, continues to increase significantly, while the stress only increases slightly or remains essentially unchanged. This is the core stage in which this invention exerts its "plastic support" function.

[0033] Dense strengthening stage: When plastic deformation continues and the pores inside the foamed concrete are basically compacted, the material enters a dense state, and its stiffness and strength will increase rapidly, and its deformation resistance will be significantly enhanced, thereby preventing the pile from settling indefinitely and playing a final safety guarantee role.

[0034] Through the above mechanism, when the upper load increases to the point that the stress at the pile tip exceeds the preset value, i.e., the yield strength of the foamed concrete layer 1, the foamed concrete layer 1 yields, causing a significant and controllable settlement of the end-bearing rigid pile 2. This settlement mobilizes the soil 4 between the piles below the pile cap 6 to participate in bearing, so that a portion of the load originally borne mainly by the pile body is transferred to the soil 4 between the piles in a controlled manner, thereby realizing the joint action of the pile and the soil and fully utilizing the bearing potential of the natural foundation.

[0035] In this embodiment, the cross-sectional dimensions of the foamed concrete layer 1 can be designed to be the same as those of the end-bearing rigid pile 2. In some cases where a greater pile end bearing capacity is required, enlargement construction can also be carried out after drilling into the moderately weathered rock layer 5, so that the cross-sectional dimensions of the poured foamed concrete layer 1 are larger than those of the end-bearing rigid pile 2, forming an enlarged-base end-bearing plastic support pile to improve the bearing capacity of a single pile.

[0036] Example 2: This example provides another structural form of end-bearing plastic-supported composite pile foundation. This example is mainly suitable for working conditions where the moderately weathered rock strata are extremely hard, difficult to drill, or too costly.

[0037] The main difference from Embodiment 1 lies in the implementation method of lateral constraint. In this embodiment, the drilling rig only needs to drill to the top surface of the moderately weathered rock layer 5, without needing to drill further into the rock layer. After thoroughly cleaning the sediment at the bottom of the pile hole, a prefabricated constraint sleeve 7 is placed at the bottom of the hole. This constraint sleeve 7 is preferably a steel sleeve welded from a 2-3mm thick steel plate, with its lower end face resting directly on the top surface of the moderately weathered rock layer 5.

[0038] Subsequently, foamed concrete is poured inside the restraining sleeve 7 to form a foamed concrete layer 1. In this structure, the lateral restraint of the foamed concrete layer 1 is provided by the robust restraining sleeve 7. The sleeve functions equivalently to the rock wall of the moderately weathered rock layer 5 in Example 1, and similarly ensures that the foamed concrete layer 1 exhibits the aforementioned three-stage mechanical properties of elasticity, yielding, and densification under pressure, thereby achieving the same technical principle and effect.

[0039] The subsequent procedures are the same as in Example 1. After the foamed concrete layer 1 reaches the predetermined strength, the upper end-bearing rigid pile 2 and the pile cap 6 are constructed.

[0040] A significant advantage of this invention lies in its controllability. Engineers can pre-determine the load-sharing ratio between the piles and the soil based on the superstructure load and foundation conditions. For example, the piles can be designed to bear 40% of the total load, while the soil between the piles bears 60%. Based on the load allocated to the single end-bearing rigid pile 2 and the cross-sectional area of ​​the pile tip, the required yield strength of the foamed concrete layer 1 can be accurately calculated. Then, based on the estimated settlement of the soil 4 between the piles when bearing its share of the load, combined with the yield strain of the selected foamed concrete, the required design thickness of the foamed concrete layer 1 can be calculated. This method transforms the complex pile-soil interaction problem into a controllable structural design problem.

[0041] Furthermore, the application of this invention is highly flexible. In a large pile foundation cap 6, the end-bearing rigid piles 2 of this invention can be alternated and mixed with traditional friction rigid piles 3 or other types of piles. This combination allows designers to perform more refined cap and plastic pile foundation design based on the loads transmitted by the frame columns 8 at different locations, optimizing the stiffness and bearing capacity of the entire foundation and achieving higher economic and technical benefits.

[0042] Working Principle: By innovatively setting a mechanically controllable foamed concrete layer 1 between the pile tip of the end-bearing rigid pile 2 and the hard bearing layer, and applying effective lateral restraint to it, the rigid support of the traditional end-bearing pile is transformed into a controllable plastic support. This fully utilizes the three distinct mechanical stages exhibited by the laterally restrained foamed concrete under compression: elasticity, yield plateau, and densification strengthening. Elastic Bearing Stage: Under the initial load on the composite pile foundation, the stress at the pile tip of the end-bearing rigid pile 2 is less than the yield strength of the foamed concrete layer 1. In this stage, the foamed concrete layer 1 behaves as an elastic body with minimal deformation. The stress mode of the pile foundation is similar to that of a traditional end-bearing rigid pile, with the load mainly borne by the end-bearing rigid pile 2 and transferred to the bearing layer. Plastic Yield and Load Transfer Stage: When the upper load continues to increase, causing the pile tip stress to reach and exceed the yield strength of the foamed concrete layer 1, the key link in the working principle is triggered. When the foamed concrete layer 1 enters the yield plateau stage, its internal structure undergoes plastic deformation. This manifests as a relatively constant bearing stress, but a significant increase in vertical compressive deformation (i.e., settlement). This controllable pile tip settlement is equivalent to the effect of a traditional plastic-supported pile tip penetrating the soil, thus forcing coordinated deformation between the pile cap 6 and the soil between the piles 4. This effectively and smoothly transfers the subsequently increased load to the soil between the piles 4, ultimately achieving the goal of shared load sharing between the piles and the soil. Dense Strengthening and Safety Assurance Stage: If settlement continues, after the internal pores of the foamed concrete layer 1 are fully compacted, it will enter the dense strengthening stage. At this time, its stiffness and strength will significantly increase, and its deformation resistance will rapidly strengthen, thus providing a final safety reserve for the entire pile foundation system and preventing excessive settlement of the piles.

[0043] Finally, it should be noted that the above description is only a preferred embodiment of the present utility model and is not intended to limit the present utility model. Although the present utility model has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present utility model should be included within the protection scope of the present utility model.

Claims

1. A composite pile foundation with end-bearing plastic support, characterized in that: include: End-bearing rigid pile (2); The pile cap (6) is located on the top of the end-bearing rigid pile (2); Foamed concrete layer (1) located at the end of the end-bearing rigid pile (2); The foamed concrete layer (1) is subjected to lateral restraint so that when it is subjected to the vertical pressure transmitted by the end-bearing rigid pile (2), its stress-strain relationship exhibits three-stage characteristics: elastic segment, yield plateau segment, and dense strengthening segment.

2. The composite pile foundation with end-bearing plastic support according to claim 1, characterized in that: The foamed concrete layer (1) is embedded in the moderately weathered rock layer (5), and the lateral constraint is applied to it by the moderately weathered rock layer (5).

3. The composite pile foundation with end-bearing plastic support according to claim 2, characterized in that: The foamed concrete layer (1) is disposed inside the constraint sleeve (7), and the lateral constraint is applied to it through the constraint sleeve (7).

4. The composite pile foundation with end-bearing plastic support according to claim 3, characterized in that: The constraint sleeve (7) is a steel sleeve, and the lower end of the constraint sleeve (7) sits on the top surface of the moderately weathered rock layer (5).

5. The composite pile foundation with end-bearing plastic support according to claim 1, characterized in that: The end-bearing rigid pile (2) is a reinforced concrete cast-in-place pile.

6. The composite pile foundation with end-bearing plastic support according to claim 1, characterized in that: The cross-sectional dimension of the foamed concrete layer (1) is greater than or equal to the cross-sectional dimension of the end-bearing rigid pile (2).

7. The composite pile foundation with end-bearing plastic support according to claim 1, characterized in that: The end-bearing rigid pile (2) can be alternately arranged with the conventional friction rigid pile (3) under the pile cap (6).

Images