End bearing friction pile

Abstract

The utility model relates to the technical field of construction pile bodies, and discloses an end bearing friction pile which comprises a pile body and a reinforcement cage, the reinforcement cage is located in the pile body, the pile body is composed of a plurality of arc-shaped faces in the circumferential direction, and the arc-shaped faces are the same in radian and used for increasing the surface area of the side face of the pile body. On the premise that the allowable value of the axial bearing capacity of a single pile is met, the section shape of the pile is optimized through a topological structure, so that the material consumption of the pile is reduced, the construction cost is reduced, and social resources are saved.

Description

Technical Field

[0001] The utility model relates to the technical field of construction pile bodies, and more specifically, to a bearing friction pile in particular. Background Art

[0002] The pile foundation is a deep foundation form with a long history and is widely used in engineering practice. With the progress of engineering construction level and modern technology, great development or improvement has been made in various aspects such as the pile forming process of piles, the design theory and calculation methods of piles. The building load is transmitted to the foundation through the pile foundation. The vertical load is generally supported by the frictional resistance generated by the soil on the pile side and the resistance of the soil layer at the pile bottom.

[0003] The bearing friction pile penetrates and is supported in a solid soil layer. Under the action of vertical load, the bearing capacity exerted by the foundation pile is mainly the side frictional resistance. According to the "Technical Code for Building Foundation Piles" (JGJ 94-2008), under the ultimate limit state of bearing capacity, the vertical load at the pile top of the friction pile is borne by the side resistance of the pile. The bearing friction pile has the characteristics of small construction difficulty and low project cost. Topological optimization is a mathematical method for optimizing the material distribution within a given area according to the given load conditions, constraint conditions, and performance indicators, and it is a kind of structural optimization.

[0004] As Figure 1 and Figure 2 shown, at present, the bearing friction pile 1 basically uses a circular or square cross-section. The bearing friction pile penetrates through the soft soil layer 2 to reach the medium soil layer 3. The contact area between the bearing friction pile 1 and the soft soil layer 2 is small, resulting in a small side pile friction force, which causes the bearing capacity of the bearing friction pile 1 to decrease. The cross-sectional area of the bearing friction pile 1 in the medium soil layer 3 is large. Such a bearing friction pile has problems of waste of building materials and increase in construction costs caused by some redundant structures not exerting bearing performance.

[0005] In view of this, this application proposes a bearing friction pile after topological optimization. Content of the Utility Model

[0006] The purpose of the utility model is to provide a bearing friction pile to solve the problems existing in the prior art. On the premise of meeting the allowable value of the axial bearing capacity of a single pile, the cross-sectional shape of the pile is optimized by using a topological structure to reduce the material usage of the pile, lower the project cost, and save social resources.

[0007] To achieve the above purpose, the utility model provides the following solution: The utility model provides a bearing friction pile, including: a pile body and a steel reinforcement cage. The steel reinforcement cage is located inside the pile body. The circumference of the pile body is composed of several arc surfaces, and the radian of several arc surfaces is the same, which is used to increase the surface area of the side of the pile body.

[0008] Further, there are 4 arc surfaces, and the two ends of adjacent arc surfaces are fixedly connected respectively to form the side surface of the pile body.

[0009] Further, both the top surface and the bottom surface of the pile body are four - cornered stars.

[0010] Further, the cross - section of the steel reinforcement cage is a cross - shaped structure.

[0011] Further, the pile body is a reinforced concrete structure.

[0012] The present utility model discloses the following technical effects:

[0013] In this device, the end - bearing friction pile after topological optimization is composed of a pile body and a steel reinforcement cage. The pile body is composed of several arc surfaces, which effectively increases the surface area of the side surface of the pile body, significantly increases the vertical friction resistance received by the pile body, reduces the vertical displacement generated when the pile body is subjected to vertical loads, and effectively improves the bearing capacity of the pile in the vertical direction; the pile body is composed of arc surfaces, which can reduce the cross - sectional area of the pile body, effectively improve the utilization efficiency of materials, save engineering materials, and reduce the project cost. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] In order to more clearly illustrate the technical solutions in the embodiments of the present utility model or the prior art, the following will briefly introduce the drawings required to be used in the embodiments. Obviously, the drawings in the following description are only some embodiments of the present utility model. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0015] Figure 1 It is the state diagram of the end - bearing friction pile during use in the existing engineering design practice;

[0016] Figure 2 It is the top view of the end - bearing friction pile in the existing engineering design practice;

[0017] Figure 3 It is the structural schematic diagram of the whole of the present utility model;

[0018] Figure 4 It is the top view of the whole of the present utility model;

[0019] Figure 5 It is the state diagram of the whole of the present utility model during use;

[0020] Figure 6 For Figure 5 the cross - section view of 4 - 1 in

[0021] Among them, 1. End - bearing friction pile; 2. Soft soil layer; 3. Medium soil layer; 4. Pile body; 401. Arc surface; 5. Steel reinforcement cage. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0022] The following will clearly and completely describe the technical solutions in the embodiments of the present utility model in conjunction with the accompanying drawings in the embodiments of the present utility model. Obviously, the described embodiments are only a part of the embodiments of the present utility model, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present utility model without creative efforts shall fall within the protection scope of the present utility model.

[0023] In order to make the above objects, features, and advantages of the present utility model more obvious and understandable, the present utility model will be further described in detail below in conjunction with the accompanying drawings and specific embodiments.

[0024] As Figures 3 - 6 shown, the present utility model provides an end-bearing friction pile, which includes a pile body 4 and a steel reinforcement cage 5. The pile body 4 is filled with the steel reinforcement cage 5. The steel reinforcement cage 5 is located inside the pile body 4 and plays a supporting role for the pile body 4.

[0025] As Figure 3 and Figure 4 shown, the pile body 4 is composed of a plurality of arc surfaces 401. In this embodiment, there are 4 arc surfaces 401. The 4 arc surfaces 401 are distributed in the circumferential direction of the pile body 4. The two ends of adjacent arc surfaces 401 are fixedly connected to form the pile body 4. The 4 side surfaces of the pile body 4 are the 4 arc surfaces 401 in this embodiment. The cross-sections of the top and bottom surfaces of the pile body 4 are four-pointed stars.

[0026] After topological optimization, the side surface of the pile body 4 in this embodiment is an arc surface 401. Compared with the cylindrical end-bearing friction pile 1 or the square end-bearing friction pile 1 in the prior art, the side surface area of the pile body 4 in this embodiment is larger, so that the vertical friction resistance received by the pile body 4 is significantly increased, reducing the vertical displacement generated by the pile body 4 under vertical load. The vertical friction resistance received by the pile body 4 is increased, effectively improving the bearing capacity of the pile body 4 in the vertical direction.

[0027] In this embodiment, the cross-sections of the top and bottom surfaces of the pile body 4 are four-pointed stars. Compared with the circular or square cross-sections of the end-bearing friction pile 1 in the prior art, the cross-sectional area of the pile body 4 in this embodiment is greatly reduced, effectively improving the material utilization efficiency, saving engineering materials, and reducing the project cost.

[0028] As Figure 5As shown in the figure, the pile body 4 penetrates through the soft soil layer 2 to reach the medium soil layer 3. In the soft soil layer 2, the skin friction of the pile body 4 is mainly considered, and the bearing capacity of the soft soil layer 2 is increased by the skin friction provided by the pile side. In this embodiment, the pile side is an arc surface 401, which can increase the contact area with the soft soil layer 2, thereby increasing the friction force and improving the support load of the pile side; in the medium soil layer 3, the skin friction of the pile side and the end bearing capacity of the pile tip are mainly utilized. The arc surface 401 of the pile side can provide greater friction force and support load. At the same time, when the end bearing capacity is satisfied, the cross-section of the pile tip is a four-corner star shape, which effectively reduces the cross-sectional area, reduces the use of engineering materials, and reduces the project cost.

[0029] As Figure 6 shown, the pile body 4 is a reinforced concrete structure. When pouring concrete, the steel reinforcement cage 5 is poured into the pile body 4. The cross-section of the steel reinforcement cage 5 is a cross-shaped structure, which is adapted to the arc-shaped side structure of the pile body 4 and can better support the pile body 4.

[0030] In this embodiment, the arc radian of the arc surface is determined through topology optimization calculation based on the allowable value of the axial compressive bearing capacity of a single pile, the pile body length, on-site geological and hydrological surveys and other data. Specifically: First, determine the basic parameters such as the unit weight of soil, the internal friction angle of the foundation soil, and the soil cohesion through on-site geological and hydrological surveys; determine the allowable value of the axial compressive bearing capacity of a single pile and the pile body length according to specific construction design requirements; use Terzaghi's bearing capacity theory to determine the ultimate bearing capacity of the foundation; establish a constraint equation related to the cross-sectional shape with the maximum allowable compressive bearing capacity as the constraint condition; conduct topology optimization with the goal of minimizing the use of engineering materials, that is, minimizing the cross-sectional area of the pile, to determine the cross-sectional shape of the pile body.

[0031] The bearing capacity of the pile bottom is calculated by Terzaghi's formula, and the calculation method is as follows:

[0032] Ultimate bearing capacity of the foundation: Q b =c·N c +σv0·N q (X)

[0033] In the formula: Q b is the bearing capacity of the pile bottom (kN), c is the soil cohesion (kN / m 2 ), N c is the bearing capacity coefficient related to cohesion, σv0 is the effective vertical stress at the pile bottom (kN / m 2 ), N q is the bearing capacity coefficient related to the internal friction angle.

[0034] The shear strength on the shear plane between the pile and the soil is calculated by Coulomb's theory, and the calculation method is as follows:

[0035] Ultimate skin friction of the pile side:

[0036] In the formula: Q s is the shaft friction resistance of the pile (kN), K is the coefficient of lateral earth pressure, γ is the unit weight of the soil, z is the depth, and c a is the adhesion between the pile and the soil (kPa), L is the length of the pile (m), and A(z) is the lateral area of the pile (m 2 ).

[0037] Specific implementation case:

[0038] Suppose the conditions of a certain project site are as follows:

[0039] The unit weight of the soil γ is 20 kN / m 3 , the internal friction angle σ of the soil is 20°, the cohesion c of the soil is 30 kN / m 2 , the friction angle ξ between the pile and the soil is 10°, N c , N q can be obtained from in-situ tests on site. In this case, the minor influence of the cross-sectional shape on the relevant coefficients is ignored, and N c = 7.42, N q = 17.6, the coefficient of lateral earth pressure K = 0.447, and the adhesion ca between the pile and the soil is 28 kPa.

[0040] Set the pile length L = 10 m. The original design plan is a cylindrical cross-section pile with a diameter of 2 m. It can be calculated from the formula:

[0041] Q b = 3742.6 kN

[0042] Q s = 15061.504 kN

[0043] The total bearing capacity Q0 = 18804.104 kN

[0044] The total volume V0 = π×(D / 2) 2 ×L = π×(2 / 2) 2 ×10 = 31.4159 m 3

[0045] The process of topology optimization is as follows:

[0046] Based on the cylindrical pile with the original specified dimensions, through automatic computer search and optimization, redundant materials of the pile body are excavated, so that the top view of the pile top after removing the redundant materials is a four-corner star. Further, according to the obtained pile body, the lateral friction resistance Q s of the pile is calculated using formula (Y), and the end bearing capacity Q b of the pile is calculated using formula (X), and the following optimization problem is established:

[0047] Objective function: minV

[0048] Maxf=(Q s +Q b )

[0049] Constraint condition: Q b =c·N c +σv0·N q

[0050]

[0051] When removing the pile body material, use meta - heuristic automatic search to obtain the maximum value of f.

[0052] After optimizing according to the above process, a special - shaped pile with a four - corner star - shaped pile cross - section can be obtained. Each arc of the four - corner star of the pile cross - section is a quarter of a circle with a radius of 1.25m. Further, the bearing capacity Q and volume V of the special - shaped pile can be obtained.

[0053] Q=19279kN>Q0

[0054] V=A×L=1.34126×10=13.4126m 3 <V0

[0055] By comparing the two schemes, it can be found that when the bearing capacities are similar, the volume of the pile structure after topology optimization is significantly reduced, a large amount of engineering materials are saved, and the construction cost is reduced.

[0056] In the description of the present utility model, it should be understood that the orientation or positional relationship indicated by the terms "longitudinal", "transverse", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc. is based on the orientation or positional relationship shown in the drawings. It is only for the convenience of describing the present utility model, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the present utility model.

[0057] The embodiments described above are only for describing the preferred mode of the present utility model, and do not limit the scope of the present utility model. Without departing from the design spirit of the present utility model, various deformations and improvements made by those of ordinary skill in the art to the technical solutions of the present utility model should fall within the protection scope determined by the claims of the present utility model.

Claims

1. A bearing friction pile, characterized in that, Including: A pile body (4) and a steel reinforcement cage (5), the steel reinforcement cage (5) is located inside the pile body (4), the circumferential direction of the pile body (4) is composed of a plurality of arc surfaces (401), and the radian of a plurality of the arc surfaces (401) is the same, which is used to increase the surface area of the side surface of the pile body (4).

2. The end-bearing friction pile according to claim 1, characterized in that There are 4 arc surfaces (401) provided, and both ends of adjacent arc surfaces (401) are fixedly connected respectively to form the side surface of the pile body (4).

3. The end-bearing friction pile according to claim 2, wherein: Both the top surface and the bottom surface of the pile body (4) are four - cornered stars.

4. The end-bearing friction pile according to claim 1, wherein: The cross - section of the steel reinforcement cage (5) is a cross - shaped structure.

5. The end-bearing friction pile according to claim 1, wherein: The pile body (4) is a reinforced concrete structure.

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