CN112746610A

CN112746610A - Concrete pile

Info

Publication number: CN112746610A
Application number: CN201911042190.2A
Authority: CN
Inventors: 张国梁; 徐永洁
Original assignee: Individual
Current assignee: Individual
Priority date: 2019-10-30
Filing date: 2019-10-30
Publication date: 2021-05-04
Also published as: CN116397636A

Abstract

A concrete pile adopting a new structural design not only ensures the quality of a vertical end part during construction, and further ensures the design bearing capacity of the end part, but also gives play to the effect of side friction resistance by paying more attention to consideration, and brings increment of the bearing capacity of the pile. The concrete pile (1) comprises a pile body (4) and a branch (2) extending outwards, the structure of the branch (2) is the sum of the friction force of the side surface (3) of the branch (2) and the bearing force of the end part of the branch (2) according to the bearing force of the branch (2), so that the design of the structure of the branch (2) is set in a mode of exerting the effect of the friction force of the side surface (3) of the branch (2) by considering more, and further converting the effect into a part of the bearing force of the pile (1).

Description

Concrete pile

Technical Field

The invention relates to the field of civil engineering, in particular to the technical field of foundation foundations.

Background

In the technical field of foundation foundations, concrete piles with concrete discs and concrete branches have become an existing technology, but in the practice of design and construction of specific piles, even under the condition of branches, the bearing capacity of the piles is remarkably improved in the structural design concept of the piles in a mode of only considering the bearing capacity of the bottom surfaces of the end portions of the discs, however, in a soft soil foundation which is frequently encountered, soil in the disc cavities collapses during construction, diameter reduction is frequently encountered, the construction quality of the disc cavities is difficult to guarantee, the design bearing capacity of the end portions of the discs cannot be ensured, and the bearing capacity of the piles is adversely affected. That is, in the prior art, not only the frictional resistance of the soil is not considered, but also the bearing capacity of the end of the tray, which is heavily considered due to the construction factor and the soil body factor, cannot reach the designed value satisfactorily, so that the supporting potential of the soil body for the pile is not fully mobilized and exerted.

Disclosure of Invention

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a concrete pile, which can ensure the quality of a vertical end portion during construction, thereby ensuring the design bearing capacity of the end portion, and which can increase the bearing capacity of the pile by further paying attention to the effect of the frictional resistance of the branched side surfaces.

The concrete pile of the present invention comprises a pile body and a branch extending outward from the pile body, wherein the structure of the branch in the concrete pile satisfies the following relational expression that the bearing capacity of the branch is the sum of the frictional resistance of the side surface of the branch and the bearing capacity of the end portion of the branch, so that the design of the branch structure does not only consider the bearing capacity of the end portion of the branch but also develops the effect of the frictional resistance of the side surface of the branch in consideration and further converts the effect into a part of the bearing capacity of the pile without increasing the diameter of the pile body, namely, the relational expression is set so as to reduce the cost of the pile or improve the bearing capacity of the pile:

F＝(A×f)+(B×p)

f represents the total bearing force of the branches in the concrete pile;

a represents the area of the side surface of the branch which is in contact with the soil body;

f represents the friction coefficient of the soil body contacted with the side surface of the branch;

b represents a projected area in the vertical direction of the branch in the concrete pile;

p represents the pressure of the soil in the vertical direction of the branches in the concrete pile.

According to the scheme of the invention, when the bearing capacity of the end bottom surface is obtained by adopting the disc, when the disc cavity is manufactured, soil is easy to collapse, the disc cavity is irregular or incomplete, defects are generated, and the defects of the concrete disc are caused, namely the disc is incomplete or the disc diameter is greatly reduced compared with the designed diameter, the soil around the disc cavity is not compact enough to extrude, and finally the end surface bearing capacity (non-friction resistance) obtained through the disc end bottom surface is also greatly weakened, compared with the scheme, when the branch type concrete disc is adopted, the complete and through disc cavity is not required to be manufactured, only a plurality of branches extending outwards are formed at the same elevation relative to the pile body, for example, 6-8 branches are formed, adjacent branches in a group of branches at the same elevation are not mutually communicated, the adjacent branches are separated by the extruded soil, branch holes or cavities are not communicated, and the collapse degree is greatly reduced, the holes or cavities of the branches or the branches themselves are not significantly weakened compared to the structural dimensions of the branches that are designed, as a result of which the lateral area of the branches that are finally formed is ideal, the frictional resistance of the soil mass via the side faces of the branches is sufficient, and the vertical bearing capacity of the end bottom faces of the branches is also sufficient.

According to the scheme of the invention, because a part of the bearing capacity of the pile is constructed by the frictional resistance of the side surfaces of the branches, compared with the occasion that the bearing capacity of the pile is constructed by adopting a disc in an end bearing mechanical mode, namely, only the end bearing capacity of the disc, the bearing mode of the invention is different from the traditional occasion of the pile with the disc, the soil body around or between the branches is more compact when the branches are manufactured, and thus the whole deformation of the pile is smaller.

According to the invention, in the structural design of the branches of the pile, the exertion of the area of the side faces of the branches is focused, that is, the action of the frictional resistance between the side faces of the branches and the soil is particularly considered sufficiently, so that the frictional resistance of the side faces of the pile due to the branches is more focused and more sufficiently considered than the frictional resistance of the side faces of the pile (or the branches) due to the bearing force of the end portions of the disks is merely considered and the frictional resistance of the side faces of the pile due to the branches is ignored in the design concept of the pile as in the conventional concrete pile with disks, and as a result, when the branches are provided, the bearing force of the end portions of the branches is shifted, and the action of the frictional resistance of the soil is shifted in the design of the pile, so that the bearing force of the branches of the pile is converted into the bearing force of the pile, that is converted into a part of the bearing force of the pile, and thus the bearing force of the pile, thereby reducing the cost of the pile or improving the bearing capacity of the pile. Essentially, according to the invention, it is most important to optimize the pile structure, focusing on the increase of the friction resistance by enlarging the area of the side face of the pile, rather than just on the bearing capacity of the end face of the disc, as in the case of the conventional piles with discs, and/or branches, if the bearing capacity of the pile is to be increased, because the friction resistance between the disc and the soil is slight and negligible, only on the increase of the number of discs and the enlargement of the diameter of the disc, whereas according to the invention, if the bearing capacity of the pile is to be increased, focusing on the increase of the number of branches and the increase of the area of the side face of the branch, the increase of the friction resistance between the branch and the soil is considered from the aspect of force, i.e. the shifting of the bearing capacity of the pile by the soil due to the friction resistance of the soil is considered to be emphasized. That is, from the construction environment, particularly in a soft ground, not only is a branched hole or cavity easily secured, which is not easily collapsed, but also frictional resistance of the side of the branch can be utilized. As a result, not only the (vertical) bearing capacity of the end portion of the bottom surface of the branch is ensured to reach the design value, but also an increase in the bearing capacity of the pile due to the frictional resistance is obtained, and since the hole or the cavity of the branch is easily ensured, it is not easily collapsed, and the increase can be ensured to reach the design value.

According to the scheme of the invention, because the frictional resistance of the soil body is adjusted through the branch, the bearing potential of the soil as the frictional resistance of the soil to the side surface (the side surface of the branch) of the pile is excavated, and compared with the radius of the disc in the occasion of obtaining the bearing capacity of the end bottom surface by adopting the disc, the radius of the vertical projection of the branch (the horizontal distance between the outer end of the branch and the vertical central axis of the pile) is greatly reduced, namely the horizontal extrusion radius when the branch hole is extruded is greatly reduced.

The concrete pile according to claim 2 of the present invention is characterized in that a plurality of branches are provided at one elevation of the pile body, and a plurality of branches located at different elevations are provided in the vertical direction of the pile body.

According to the scheme, because a plurality of branches are arranged at the same elevation, and a plurality of groups of branches are arranged at different elevations, a plurality of branches and a plurality of groups of branches are arranged in the horizontal direction and the vertical direction, more soil bodies can be mobilized to participate in stress, and the bearing capacity of the pile is greatly improved.

The concrete pile according to claim 3 of the present invention is characterized in that the phases of the branches of the adjacent groups of branches located at adjacent elevations among the plurality of groups of branches located at different elevations are staggered from each other in a vertical horizontal projection.

According to the scheme, because the phases of the branches in the adjacent groups of the branches positioned at the adjacent elevations in the multiple groups of branches arranged at different elevations are staggered from each other when viewed from the vertical horizontal projection, the multi-layer branches (the vertical distance between the vertically adjacent branches is smaller) can be adopted to meet the requirement of bearing capacity when the pile body is short and is not suitable for arranging disks (the vertical distance between the vertically adjacent disks is larger in the situation of arranging multiple layers of disks).

The concrete pile according to claim 4 of the present invention is characterized in that the phases of the branches of the plurality of sets of branches provided at different elevations are staggered from each other in a vertical horizontal projection.

According to the scheme, the phases of the branches in the multiple groups of branches arranged at different elevations are staggered from the vertical horizontal projection, so that the branches between the branches of all layers are not aligned up and down, the influence of disturbance on the soil body between the branches is small, the branches of more layers can be adopted, and the requirement of higher bearing capacity is met.

The concrete pile according to claim 5 of the present invention is characterized in that the branch is tapered at the tip.

According to the scheme, the front end of the branch is conical, so that the construction is convenient to adopt an arch-shaped press to manufacture branch holes or cavities.

The concrete pile according to claim 6 of the present invention is characterized in that the vertical cross-section of the branch is triangular.

According to the scheme, the vertical section of the branch is triangular, so that the construction is convenient to adopt the bow-shaped press to manufacture the branch hole or cavity.

The concrete pile according to claim 7 of the present invention is characterized in that the number of branches extending outward from the pile body is 6 in total at an elevation where the branches of the pile body are located, as viewed in a horizontal direction.

According to the scheme, the number of branches extending outwards from the pile body at the elevation where the branches of the pile body are located is 6 in total when viewed from the horizontal direction, so that higher frictional resistance and bearing capacity of the end parts of the bottom surfaces of the branches are obtained under the condition that the soil body is not disturbed excessively.

The concrete pile according to claim 8 of the present invention is characterized in that the number of branches extending outward from the pile body is 8 in total at an elevation where the branches of the pile body are located, as viewed in a horizontal direction.

According to the scheme, the number of branches extending outwards from the pile body at the elevation where the branches of the pile body are located is 8 in total when viewed from the horizontal direction, so that higher frictional resistance and bearing capacity of the end parts of the bottom surfaces of the branches are obtained under the condition that the soil body is not disturbed excessively.

The concrete pile according to claim 9 of the present invention is characterized in that the pile body and/or the branch is made of steel fiber concrete.

According to the scheme, the pile body and/or the branches are made of the steel fiber concrete, and the friction force obtained through the branches and the effective end bearing capacity of the bottom surfaces of the branches are utilized, so that the use of steel bars can be saved or the steel bars are not adopted, and the cost of the concrete is greatly saved.

The concrete pile according to claim 10 of the present invention is characterized in that the pile body and/or the branch is made of ultra high performance concrete, i.e., UHPC.

According to the above scheme, since the pile body and/or the branch is made of ultra-high performance concrete, i.e. UHPC, for example, ultra-high strength concrete, compared with the situation that when high bearing capacity is required, like the prior art ordinary pile without branch and tray, high bearing capacity is obtained by adopting frictional resistance or large pile diameter, but the pile body is made of low grade concrete (at this time, because the pile diameter is thicker, it is not suitable for using UHPC, otherwise, the cost is higher), the bearing capacity of the soil (i.e. the bearing capacity caused by frictional resistance and the bearing capacity caused by end bearing capacity) is sufficiently adjusted by the structure of the branch of the pile, and the requirement of the compressive resistance of the pile body is met, because the pile body itself is thinner, a thinner pile body can be formed by UHPC, and the UHPC works in coordination with the novel branch structure of the present invention, and while the high bearing capacity is met, the diameter of the pile is reduced, and the cost is further reduced.

Drawings

Fig. 1 is a perspective view of a concrete pile according to an embodiment of the present invention;

fig. 2 is a top view of the concrete pile shown in fig. 1;

fig. 3 is a side view illustrating a branch of the concrete pile shown in fig. 1;

FIG. 4 is a perspective view showing a concrete pile constituting an example of a construction test according to another embodiment

Fig. 5 is a cross-sectional view of one of the 1-component branches of the concrete pile shown in fig. 4 in a pile diameter direction thereof;

fig. 6 is a top view of a group 2 branch of the concrete pile shown in fig. 4;

fig. 7 is a top view of group 1 branches of the concrete pile shown in fig. 4;

FIG. 8 is an elevation view of a concrete pile with a disc as a comparison, constituting a prior art;

fig. 9 is a plan view showing a disc in the concrete pile shown in fig. 8;

fig. 10 is a side view illustrating a disc in the concrete pile shown in fig. 8.

Detailed Description

Embodiments of the present invention will be described below with reference to the accompanying drawings.

Fig. 1 shows a partial perspective view of a concrete pile 1 according to an embodiment of the present invention, the concrete pile 1 including a

pile body

4 and 1 set of branches b, the 1 set of branches b being disposed at a prescribed height in the pile body 4 as viewed from a partial view of the illustrated pile, the set of branches b including 8 branches 2 uniformly arranged, the 8 branches 2 protruding outward from the pile body 4 as viewed from a horizontal side as shown in fig. 3, fig. 2 showing a side surface of the branches 2, the 8 branches 2 of the set of branches b being arranged spaced apart at a uniform angular interval as viewed from a top surface, in the present embodiment, each branch 2 of the 8 branches 2 is identical in size and dimension, as shown in fig. 2, each branch 2 is substantially triangular as viewed from a side surface as shown in fig. 3, each branch 2 is substantially rectangular as viewed from a top surface, a three-dimensional shape of each branch 2 is substantially triangular piece-like, the vertical height of each branch 2 in contact with shaft 4 is indicated by 25, the horizontal projection length of 5 of each branch 2 projecting outwards from shaft 4 is indicated by 23, the vertical dimension of the cone in each branch 2, which is the most projecting front part, is indicated by 24, and the thickness of the sheet in each branch 2 in the horizontal direction is indicated by 22 (see fig. 6, 7).

In the case of one branch 2 of the group 1 of branches B, the shape and the dimensions are determined in such a way that the bearing capacity F is substantially the sum of the lateral friction of the branch 2 and the bearing capacity of the end of the branch 2, the lateral friction of the branch 2 being equal to a × F, i.e. the product of the total effective area a of the 2 sides of the branch 2 and the soil friction coefficient F, and the bearing capacity of the end of the branch 2 being equal to B × p, i.e. the product of the horizontal projected area B of the branch 2 and the soil pressure p.

F＝(A×f)+(B×p)＝{[2×(2₃×2₅)]×f}+(2₂×2₃×p)

F represents the total bearing force of the branches in the concrete pile;

In terms of the bearing capacity of the 1 group of branches b, where n represents the number of the 1 group of branches b, and the shape and size of each branch in the group of branches are the same, the bearing capacity of the 1 group of branches b is:

F_{single group}＝n×[(A×f)+(B×p)]＝n×{[2×(2₃×2₅)×f]+(2₂×2₃×p)}

In one experimental example, as shown in fig. 4 to 7, the concrete pile 1 includes 4 sets of branches b, each branch 2 in the 4 sets of branches b is identical in size and shape, and in order from top to bottom, an included angle α between a radial line passing through the shaft center and a radial line passing through the shaft center of a 1 st branch 2 on the left side of the y-axis in a 1 st branch b in the 4 sets of branches b is 45 °, and as shown in fig. 7, an included angle α between a radial line passing through the shaft center and a y-axis of a 1 st branch 2 on the left side of the y-axis in a 2 nd branch b in the 4 sets of branches b is₁Is 22.5 deg., as shown in fig. 6, where alpha is not equal to alpha₁That is, in the case where the phases of 8 branches 2 in the 1 st group branch b of the 4 groups of branches b and 8 branches 2 in the 2 nd group branch b of the 4 groups of branches b are shifted from each other in a plan view, and in the same manner, the phases of 8 branches 2 in the 2 nd group branch b of the 4 groups of branches b and 8 branches 2 in the 3 rd group branch b of the 4 groups of branches b are shifted from each other in a plan view, and the phases of 8 branches 2 in the 3 rd group branch b of the 4 groups of branches b and 8 branches 2 in the 4 th group branch b of the 4 groups of branches b are shifted from each other in a plan view, the length of the shaft 4 of the concrete pile 1 is 14.45m, the diameter of the shaft 4 is 1.6m, and the specific dimensions for each branch 2 are: 2₂Is 54cm, 2₃Is 75cm, 2₃Is 20cm, 2₅180cm, and for the concrete pile 1, the diameter of the pile body 4 is 160cm, as shown in fig. 5.

As described above, the bearing capacity F for a single group of branches is calculated according to the following formula,

Specifically, for the present test example, the bearing capacity F of the single component is:

F_{single group}＝4×{[2×(75×180)×f]+(54×75×p)}

At the 1 st group of branches b (the uppermost 1 group of branches b), the soil is silty clay, the friction coefficient f of the soil layer is 20, the end face pressure p of the soil layer is 80,

at the 2 nd branch b (1 group branch below the 1 st branch b), the soil is clay, and the friction coefficient of the soil layer is 2₅The end face pressure of the soil layer is 160,

at the 3 rd group branch b (1 group branch b below the 2 nd group branch), the soil is clay, the friction coefficient f of the soil layer is 30, the end face pressure p of the soil layer is 200,

at the 4 th group of branches b (1 group of branches b below the 3 rd group of branches), the soil is strongly weathered granite, the friction coefficient f of the soil layer is 80, the end face pressure p of the soil layer is 450,

TABLE 1

Table 1 shows the relative bearing capacity of a pile with 4 sets of branches

(1) The geology of the pile is characterized in that: the silty clay stratum is long in short piles and is densely arranged and branched;

(2) the bearing capacity provided by the side friction resistance of the 4 groups of branches is greater than that provided by the side friction resistance of the pile body;

(3) the side friction of the 4 groups of branches accounts for 66.5 percent of the total side friction bearing capacity and accounts for 41.2 percent of the total bearing capacity provided by the branches.

In contrast, a comparative example of a prior art pile with 2 disks (not shown in the figures, but the pile of fig. 8 can be referred to, but only with 2 disks a instead of 3 disks a) is given, where only 2 disks, but not 3, can be made due to geological constraints.

The diameter of the pile body 4 of the concrete pile 1 is 1.6m, the pile length is 14.45m, the disc diameter is 3.1m, the disc height is 1.6m, and the effective area of the disc bottom surface is as follows: 0.25X π×(3.1²-1.6²)＝5.534m²

TABLE 2

Table 2 shows the values of the relative bearing capacity for the case of the design with branched piles and the design with disc piles.

In contrast to the design of the pile with 4 sets of branches b and the design of the pile with 2 discs, the sides of the branches 2 provide a large amount of side friction (colloquially referred to as "side friction"), thereby significantly increasing the bearing capacity (in this case, the side friction of the 4 groups of branches b increases the bearing capacity of the pile, with a contribution rate of 34.1%), and specifically, by comparison, although the bearing capacity of the design scheme of the pile adopting the 4 groups of branches b and the end face bearing capacity of the design scheme of the pile adopting the 2 disks are 2392KN and 2760KN respectively, the difference of the end face bearing capacities (commonly called as end bearing) of the two is not large, however, the design with 4 sets of branches b had a total bearing capacity of 4910KN, whereas the total bearing capacity of the design with piles of 2 discs was 3926KN, the total bearing capacity of the design with piles of 4 sets of branches b was 1.25 times the total bearing capacity of the design with piles of 2 discs.

Claims

1. A concrete pile comprising a pile body and a branch extending outward from the pile body, wherein the branch structure in the concrete pile is set so as to satisfy the following relationship that the bearing capacity of the branch is the sum of the frictional resistance of the side surface of the branch and the bearing capacity of the end portion of the branch, whereby the branch structure is designed not only in consideration of the bearing capacity of the end portion of the branch but also in consideration of the effect of the frictional resistance of the side surface of the branch, and is converted into a part of the bearing capacity of the pile, that is, the bearing capacity of the pile is improved, without increasing the diameter of the pile body, the relationship being such that:

F＝(A×f)+(B×p)

f represents the total bearing force of the branches in the concrete pile;

2. Concrete pile according to claim 1, characterised in that one set of branches is provided at one elevation of the pile body and a plurality of sets of branches at different elevations are provided in the up-down direction of the pile body.

3. Concrete pile according to claim 2, characterized in that the phases of the branches of adjacent groups of branches at adjacent elevations of the groups of branches at different elevations are staggered with respect to each other in a vertical horizontal projection.

4. Concrete pile according to claim 3, characterized in that the phases of the branches of the sets of branches arranged at different elevations are mutually staggered, viewed in vertical horizontal projection.

5. A concrete pile according to claim 1, wherein said limbs are tapered at their forward ends.

6. A concrete pile according to claim 1, wherein said branches have a triangular vertical cross-section.

7. Concrete pile according to claim 1, characterised in that the number of branches projecting outwards from the pile body, seen in horizontal direction, at the level of the branches of the pile body, amounts to 6.

8. The concrete pile according to claim 1, wherein the number of branches extending outward from the pile body is 8 in total at the level of the branch of the pile body as viewed in the horizontal direction.

9. Concrete pile according to claim 1, characterised in that the shaft and/or the branches are steel fibre concrete.

10. Concrete pile according to claim 1, characterised in that the shaft and/or the branches are made of Ultra High Performance Concrete (UHPC).