KR20220164975A - Complex foundation pre-loading structure and construction method to reduce residual settlement and improve support performance - Google Patents

Abstract

The present invention relates to a complex foundation preloading structure, which is able to, when a complex foundation using a pile foundation and a direct foundation together is applied, obtain a pounding effect by compressing the ground before building an upper structure for overcoming the problem that the load the direct foundation should bear is transferred to the pile foundation by the residual settlement of the upper structure, and a complex foundation preloading construction method for the same. The present invention provides the complex foundation preloading structure which comprises: a precast (PC) embossing block having a vertical hollow hole and having a lower surface coming in contact with the ground surface; a pressing plate horizontally embedded in the embossing block and exposed on a middle end of the hollow hole; a coupling plate located on a lower end in the hollow hole; a plurality of connection rods having an upper end and a lower end fastened by respectively penetrating the pressing plate and the coupling plate; and one or more piles inserted into the ground and having a head unit coupled to the coupling plate. The PC embossing block is embedded and fixed in the direct foundation concrete while compressing the ground downward.

Description

Complex foundation pre-loading structure and construction method to reduce residual settlement and improve support performance}

In the present invention, when a composite foundation using a pile foundation and a direct foundation is applied, the ground is compacted by compressing the ground before the construction of the superstructure to overcome the problem that the load to be shared by the direct foundation is transferred to the pile foundation due to the residual settlement of the superstructure It relates to a composite foundation wire-load structure that can achieve the effect and a composite foundation wire-load method for constructing such a structure.

If the condition of the foundation ground is insufficient for a direct foundation, but the ground is good to some extent (N=20 or more) and the ground itself has the bearing capacity, a pile-front composite foundation using a pile foundation and a direct foundation in combination is used. can be applied In the building foundation structure design standard (KDS 41 20 00: 2019), as shown in [Table 1] below, it is stipulated that the pile front composite foundation can be applied. However, pile-front composite foundations are not used frequently because the design procedure is complicated and finite element analysis must be performed.

4. Design
4.5 Combined basis
4.5.4 Piled Raft Foundation
(1) The pile front composite foundation is a foundation type in which a direct foundation and a pile foundation support the upper structure in a complex way. must be satisfied simultaneously.
(2) The safety of pile-faced composite foundations should be checked by reviewing the following items.
① It is necessary to ensure that the deformation and deformation angle of the foundation member that can affect the upper structure is within the allowable value to ensure structural safety.
② The stress, deformation angle, and crack width of each member acting on the foundation member should be reviewed.
③ The vertical bearing capacity and settlement of the foundation ground should be reviewed, and the level of compaction of the ground under the front foundation plate should be checked. In addition, the safety of piles and foundations should be confirmed by conducting tests in accordance with KDS 41 10 10(10).

The load acting on the pile-front composite foundation is presented as [Equation 1] and [Reference Figure 1] below (Katzenbach & Reul, 1997),

[Equation 1] R _tot = R _raft + ∑R _pile

Where, R _tot : Total reaction force of the load on the structure

R _raft : bearing capacity borne by the raft

∑R _pile : total bearing capacity shared by piles

[Reference Figure 1]

Therefore, when designing a pile front composite foundation, the review of the direct foundation and the pile foundation should be performed at the same time. The stability of the pile foundation itself should also be fully reviewed by estimating the load sharing ratio between the direct foundation and the pile foundation. If the piles are supported on rock mass, the ratio may change depending on the pile stiffness.

The load sharing ratio of pile foundations is expressed as α _pr (∑R _pile /R _tot ), and [Reference Figure 2] below shows the relationship between α _pr and ground subsidence. Based on the ground subsidence in the absence of piles, the subsidence decreases according to α _pr . The design range can be derived using this relationship, and α _pr 0.4 to 0.7 is judged to be a reasonable design range.

[Reference Figure 2]

The pile-front composite foundation as above cannot be applied to the soft ground, and when the weight of the upper building is large in the ground with an N value of 20 to 50, the effect of the ground and the effect of the pile work in combination, so the stiffness ratio between the pile and the ground should be correct to some extent. However, in general, since piles have high stiffness and ground has low initial stiffness, the load is transferred to the pile while the ground is subjected to a compressive load at the beginning of loading, reducing the effect of the composite foundation.

Therefore, by applying a pre-loading to the ground to prevent ground displacement behavior at the beginning of loading, it is considered that the bearing capacity of the ground can be increased and the effectiveness of the composite foundation can be increased, and a structure that can implement this and method was developed.

1. Registered Patent No. 10-214125 "3-axis seismic pile structure and construction method" 2. Registered Patent No. 10-1229090 "Synthetic pile and its manufacturing method and method for embedding composite piles using the same" 3. Registered Patent No. 10-1056027 "Combined structure of tapered prestressed concrete composite pile with tension member and expanded foundation"

The present invention is a composite foundation line that can improve the supporting performance by overcoming the problem that the load to be shared by the direct foundation is transferred to the pile foundation due to the residual settlement of the upper structure when the composite foundation using the pile foundation and the direct foundation is applied. Its purpose is to provide a load structure and construction method.

In order to solve the above-described problems, the present invention is a PC (Precast) acupressure block in which hollow holes are formed in the vertical direction and the lower surface is in contact with the ground; a pressing plate buried in the acupressure block in a horizontal direction and exposed to the middle of the hollow hole; a coupling plate disposed at an inner lower end of the hollow hole; a plurality of connecting rods having upper and lower ends penetrating the pressure plate and the coupling plate, respectively; And a single or a plurality of piles penetrated into the ground and having a head coupled to the coupling plate, and the PC pressure block is directly embedded in the foundation concrete in a state of pressing the ground downward and fixed. It provides a composite foundation wire load structure characterized in that.

The coupling plate is provided with a guide tube for guiding the installation angle of the pile, and it is possible to apply that the head of the pile is inserted and coupled to the guide tube.

As the pile, it is possible to apply a three-axis inclined pile spaced apart from the center of the coupling plate at equal intervals and inclined to spread downward and outward.

The pressure plate may be configured to form one or a plurality of through holes on the plate surface so that the space between the pressure plate and the coupling plate is directly filled with foundation concrete.

In addition, the present invention is a construction method of the above-described composite foundation wire load structure, (a) fastening the lower end of the connecting rod to the coupling plate; (b) penetrating and fixing the pile at a planned point, and combining the head of the pile with the coupling plate; (c) placing the PC acupressure block on the ground so that the upper end of the connecting rod passes through the pressure plate and the coupling plate is located at the lower end of the hollow hole; (d) applying a compressive load to the pressing plate by a reaction force pulling the connecting rod, and fastening the upper end of the connecting rod to the pressing plate in a state in which the PC acupressure block presses the ground; And (e) pouring and curing direct foundation concrete so that the PC acupressure block is buried; It provides together with a composite foundation wire loading method, characterized in that it includes.

According to the composite foundation wire load structure and method provided by the present invention, the following effects can be obtained.

1. Residual settlement is reduced by applying a pre-load to the ground in a loose state so that the ground is compressed and compacted, and each part of the composite foundation effectively shares the load of the upper structure by adjusting the stiffness ratio between the pile and the ground in an appropriate ratio You can do it.

2. It is possible to load a line load on the ground as a reaction force against the pulling force pulling the connecting rod, and the pulling force acts as a pre-stress for the piles fixed in the ground, so that the pile's bearing capacity for the compressive load is combined. It increases.

[Figure 1] shows a longitudinal section of the composite foundation wire load structure embodiments provided by the present invention.
[Figure 2] is (a) a perspective view, (b) a plan view and (c) a longitudinal sectional view of the PC acupressure block embodiment applied to the present invention.
[Figure 3a] shows a state in which one file is coupled to the coupling plate.
[Figure 3b] shows a state in which the three-axis file is coupled to the coupling plate.
[Fig. 4a] to [Fig. 4e] respectively show steps (a) to (e) of the composite foundation wire loading method provided by the present invention (based on 3-axis piles).
[Figure 5] shows a state in which the direct foundation and the pile foundation evenly share the load of the superstructure by the composite foundation wire load structure provided by the present invention.

1. Complex foundation wire load structure

The present invention relates to a pile-front composite foundation (piled raft foundation, hereinafter abbreviated as 'composite foundation') structure in which a direct foundation and a pile foundation support an upper structure in a complex manner, It is compressed and compacted to reduce residual settlement, and by adjusting the stiffness ratio of the pile (hereinafter collectively referred to as 'pile') and the ground to an appropriate ratio, each part of the composite foundation can reduce the load of the upper structure. It is about a composite foundation wire load structure configured to effectively share.

As shown in [Fig. 1], the present invention is a PC (Precast) acupressure block 10 in which hollow holes 11 are formed in the vertical direction and the lower surface is in contact with the ground 1; A pressing plate 20 buried in the acupressure block 10 in a horizontal direction and exposed to the middle of the hollow hole 11; a coupling plate 30 disposed at an inner lower end of the hollow hole 11; a plurality of connecting rods 40 having upper and lower ends penetrating and fastening the pressure plate 20 and the coupling plate 30, respectively; And penetrating into the ground, including a single or a plurality of files (pile, 50) having a head (51) coupled to the coupling plate (30), the PC acupressure block (10) is the ground (1) It provides a composite foundation wire-loading structure (100), characterized in that it is embedded and fixed to the direct foundation concrete (60) in a downwardly pressing state.

The PC acupressure block 10 and the pressure plate 20 are components for the aforementioned line load, the coupling plate 30 and the pile 50 are components corresponding to the pile foundation of the composite foundation, and the connecting rod (40) is a component that transmits a compressive force for pressing the ground while connecting the PC acupressure block 10 and the file 50. In the present invention, actions and effects are derived by the organic combination and mutual relationship of the above components.

The PC acupressure block 10 is arranged so that the lower surface is in contact with the ground 1, and as a member for reducing residual settlement by compressing the ground 1 through load loading before the construction of the upper structure, it presses the ground 1 It is directly embedded and fixed to the foundation concrete 60 in the state of doing. Therefore, the PC acupressure block 10 is preferably configured in a plate-like thickness, as shown in [Fig. 2].

The PC acupressure block 10 has a hollow hole 11 in the vertical direction is formed. A pressure plate 20 is buried in the acupressure block 10 in a horizontal direction, and the pressure plate 20 is exposed to the middle of the hollow hole 11. That is, the pressure plate 20 crosses the middle of the hollow hole 11 in the horizontal direction so that the hollow hole 11 is divided into upper and lower regions 11-1 and 11-2.

A coupling plate 30 is disposed at the inner lower end of the hollow hole 11, and accordingly, the lower surface of the coupling plate 30 comes into contact with the ground. The lower end of the connecting rod 40 and the head 51 of the pile 50 are coupled to the coupling plate.

By constructing an inverted conical ground anchoring part converging downward at the bottom of the coupling plate 30, the coupling plate 30 can be made to have the shape of a top file as a whole. In this case, the ground anchoring unit may be installed in such a way that it is pressed into the ground.

A plurality of connecting rods 40 are installed in a vertical direction, and the upper end passes through the pressure plate 20 and is fastened, and the lower end passes through the coupling plate 30 and is fastened. The pressure plate 20 and the coupling plate 30 act as one body by the connecting rod 40 . Since the pressure plate 20 is embedded in the PC acupressure block 10, and the coupling plate 30 is combined with the file 50, the integral behavior of each component is achieved through the connecting rod 40 do.

As described above, the single or multiple piles 50 are installed, and the head 51 is coupled to the coupling plate 30.

In the case of installing one pile 50, it is preferable to install so that the head 51 of the pile 50 vertically penetrates the center of the coupling plate 30, as shown in [Fig. 3a].

In the case of installing a plurality of the piles 50, as shown in [Fig. 3b], a three-axis pile 50 spaced at equal intervals from the center of the coupling plate and inclined downward to the outside can be applied. . The three-axis pile 50 can be installed in a stable tripod form with the installation angle of each of the three piles widening by 120 °. In this way, the three-axis pile 50 installed obliquely in the form of a tripod can counteract the horizontal load as well as the vertical load.

A guide tube 31 for guiding the installation angle of the pile 50 is coupled to the coupling plate 30, and the head 51 of the pile 50 is inserted and coupled to the guide tube 31. In particular, in the case of applying the three-axis pile 50, the piles 50 can be penetrated into the ground while accurately maintaining the installation angle by the guide pipe 31.

Meanwhile, one or a plurality of through holes 21 are formed on the surface of the pressing plate 20 to form a space between the pressing plate 20 and the coupling plate 30, that is, the lower region 11-2 of the hollow hole 11. ) can be filled with direct foundation concrete (60).

As the direct foundation concrete 60 is filled up to the lower region 11-2, the integrity of the composite foundation is reinforced.

2. Composite foundation pre-loading method

Hereinafter, the construction method of the above-described composite foundation wire-loading structure 100, that is, the composite foundation wire-loading method will be described in detail.

The present invention is a construction method of the composite foundation wire load structure 100, "(a) fastening the lower end of the connecting rod 40 to the coupling plate 30; (b) penetrating and fixing the pile 50 at a planned point, and combining the head 51 of the pile 50 with the coupling plate 30; (c) placing the PC acupressure block 10 on the ground so that the upper end of the connecting rod 40 passes through the pressure plate 20 and the coupling plate 30 is located at the lower end of the hollow hole 11; (d) a compressive load is applied to the pressure plate 20 with a reaction force pulling the connecting rod 40, and the PC acupressure block 10 presses the ground 1, and the upper end of the connecting rod 40 is pressed against the pressure plate signing with; And (e) pouring and curing the direct foundation concrete 60 so that the PC acupressure block 10 is buried; It provides a composite foundation line loading method comprising a.

Prior to the application of the composite foundation preloading method as above, the size of the direct foundation installation and the type, installation point and quantity of the pile foundation are determined by structural calculation, and the PC acupressure block 10 is installed accordingly.

The step (a) is a step of fastening the lower end of the connecting rod 40 to the coupling plate 30 as shown in [FIG. 4a]. In a state where the lower end of the connecting rod 40 passes through the coupling plate 30, the lower end of the connecting rod 40 is fastened by applying a fixing means such as welding, nut, or wedge to the upper and lower surfaces of the coupling plate 30.・It can be fixed.

The step (b) is a step of penetrating and fixing the pile 50 at the planned point as shown in [Fig. 4b], and combining the head 51 of the pile 50 with the coupling plate 30. to be.

The step (b) may proceed with a process of first penetrating the pile 50 into the ground and then fitting and coupling the coupling plate 30 to the head 51 protruding on the ground, but the coupling plate 30 When the guide pipe 31 is formed, the pile 50 is first inserted into the guide pipe 31, and then penetrated into the ground along the installation angle guided by the guide pipe 31, and the head 51 It can proceed efficiently by the process of combining with the guide pipe 31.

In this step (b), a steel pipe (not shown) having an auger inside is inserted into the guide pipe 31 to drill the ground along the installation direction of the guide pipe 30, and then to the drilling hole. A process of inserting and fixing the file 50 can be applied.

As shown in [Fig. 4c], in the step (c), the PC acupressure is performed so that the upper end of the connecting rod 40 penetrates the pressure plate 20 and the coupling plate 30 is positioned at the lower end of the hollow hole 11. This is the step of arranging the block 10 on the ground.

In this step (c), the PC acupressure block 10 is placed at the planned point, and in this process, the upper end of the connecting rod 40 penetrates the pressure plate 20, and the coupling plate 30 passes through the hollow hole. (11) will be located at the bottom.

As shown in [Fig. 4d], the step (d) applies a compressive load to the pressing plate 20 with a reaction force pulling the connecting rod 40 so that the PC acupressure block 10 presses the ground 1 This is a step of fastening the upper end of the connecting rod 40 to the pressing plate in the state of doing so.

In this step (d), a preloading device such as a screw jack or a hydraulic jack is installed in the upper region 11-1 of the hollow hole 11, and the pressure plate 20 is pressed and the connecting rod 40 is pulled. As a result, the PC acupressure block 10 integral with the pressure plate 20 can press the ground 1.

Since the lower end of the connecting rod 40 is fastened to the coupling plate 30, the pile 50 fixed in the ground resists the pulling force applied through the connecting rod 40, and the reaction force to the pulling force is the ground Since it acts as a compressive force for (1), it has a pre-compacting effect on the ground, which can reduce residual settlement after the construction of the superstructure, and as a result, efficient support load distribution to the composite foundation improves support performance. do.

One plate, the pulling force pulling the connecting rod 40 acts as a pre-stress for the pile 50 fixed on the ground, and the bearing capacity of the pile 50 against the compressive load is increased together.

In a state in which a compressive load is applied to the pressure plate 20 by a reaction force pulling the connecting rod 40, a fixing means such as a nut or a wedge is applied to the upper surface of the pressure plate 20 to fasten the upper end of the connecting rod 40・It can be fixed.

The step (e) is a step of pouring and curing the direct foundation concrete 60 so that the PC acupressure block 10 is embedded, as shown in [FIG. 4e].

By performing this step (e), the PC acupressure block 10 is buried so that it becomes a part of the direct foundation, and the composite foundation is completed. By forming a through hole 21 in the pressure plate 20 buried in the PC acupressure block 10, the direct foundation concrete 60 can be filled in the lower region 11-2 of the hollow hole 11 as well. have.

Due to the composite foundation wire-loaded structure constructed in the above process, the ground is first compacted before the superstructure is built, and the residual settlement is reduced, and as shown in [Fig. By evenly distributing the support performance is improved.

In the above, the present invention was examined in detail with specific examples. However, the present invention is not limited by the above embodiments and can be modified and modified within the scope without departing from the gist of the present invention. Accordingly, the claims of the present invention include such modifications and variations.

1: ground
10: PC acupressure block 11: hollow hole 11-1: upper area
11-2: lower region 20: pressure plate 21: through hole
22: through hole (pressing plate) 30: coupling plate 31: guide pipe
32: through hole (bonding plate) 40: connecting rod 50: file
60: direct foundation concrete
100: complex foundation line load structure

Claims (5)

A PC (Precast) acupressure block 10 in which a hollow hole 11 is formed in the vertical direction and the lower surface is in contact with the ground 1;
A pressing plate 20 buried in the acupressure block 10 in a horizontal direction and exposed to the middle of the hollow hole 11;
a coupling plate 30 disposed at an inner lower end of the hollow hole 11;
a plurality of connecting rods 40 having upper and lower ends penetrating and fastening the pressure plate 20 and the coupling plate 30, respectively; and
It penetrates the ground and includes a single or multiple piles 50 having a head 51 coupled to the coupling plate 30,
The PC acupressure block 10 is a composite foundation line load structure 100, characterized in that embedded and fixed to the direct foundation concrete 60 in a state of pressing the ground 1 downward.
In paragraph 1,
The coupling plate 30 is provided with a guide pipe 31 for guiding the installation angle of the pile 50,
The composite foundation wire load structure 100, characterized in that the head 51 of the pile 50 is inserted and coupled to the guide pipe 31.
In paragraph 1,
The pile 50 is a composite foundation line load structure 100, characterized in that the three-axis inclined pile spaced at equal intervals from the center of the coupling plate 30 and inclined to spread downward and outward.
In paragraph 1,
Composite foundation, characterized in that the pressure plate 20 has one or a plurality of through holes 21 formed on the plate surface so that the direct foundation concrete 60 is filled in the space between the pressure plate 20 and the coupling plate 30 Line load structure (100).
As a construction method of the composite foundation wire load structure 100 of any one of claims 1 to 4,
(a) fastening the lower end of the connecting rod 40 to the coupling plate 30;
(b) penetrating and fixing the pile 50 at a planned point, and combining the head 51 of the pile 50 with the coupling plate 30;
(c) placing the PC acupressure block 10 on the ground so that the upper end of the connecting rod 40 passes through the pressure plate 20 and the coupling plate 30 is located at the lower end of the hollow hole 11;
(d) a compressive load is applied to the pressure plate 20 with a reaction force pulling the connecting rod 40, and the PC acupressure block 10 presses the ground 1, and the upper end of the connecting rod 40 is pressed against the pressure plate signing with; and
(e) pouring and curing the direct foundation concrete 60 so that the PC acupressure block 10 is buried; Composite foundation wire loading method comprising a.

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