KR20100124028A

KR20100124028A - Construction method of lower end expanded type cast-in-place piles

Info

Publication number: KR20100124028A
Application number: KR1020090043062A
Authority: KR
Inventors: 정부호
Original assignee: 중동건설주식회사
Priority date: 2009-05-18
Filing date: 2009-05-18
Publication date: 2010-11-26

Abstract

PURPOSE: An installation method for cast-in-place piles having expanded leading ends is provided to ensure bottom bearing force eve in soft ground by extending the effective section of the leading end of pile foundation. CONSTITUTION: An installation method for cast-in-place piles having expanded leading ends is as follows. When leading end of an injection pipe(25) reaches the designated depth of a cast-in-place pile and the injection and expansion of a liquid(32) are completed, the injection pipe is pulled out. The injected liquid is solidified in the ground and a consolidated structure(33) is formed. A casing is inserted until the leading end reaches the consolidated structure, and a mesh reinforcement(23) is inserted into the casing. Concrete(31) is poured and cured inside the casing to complete a cast-in-place pile integrated in the consolidated structure.

Description

Construction method of lower end expanded type cast-in-place piles}

BACKGROUND OF THE INVENTION Field of the Invention The present invention relates to a method for constructing cast-in-place piles installed on soft foundations that do not expect effective point bearings, particularly for pile foundations. Before the construction, the ground solidified body was formed by performing a grouting to inject high-pressure injection liquid such as cement liquid or water glass into the ground around the tip of the pile. And a site casting pile in which the tip portion is joined to the fastened body, thereby enabling construction of the site casting pile with the tip portion extended.

The pile foundation is a long column-shaped structure that is infiltrated into the ground and supports the load of the upper structure by the tip bearing force, which is the bearing force of the pile tip ground, and the principal surface friction force, which is the friction force between the pile outer peripheral surface and the surrounding ground. It is classified as a ready-made pile that forms a pile on the ground and an excavation hole in the ground, and then casts and cures the concrete.

The cast-in-place piles are widely used as foundations of large structures, such as bridges and large buildings, because they can effectively install large-diameter, large-depth piles, have high construction accuracy, and have low noise and low impact on surrounding structures. The construction process of such a cast-in-placement pile is shown in FIG. 1 and outlined as follows.

First, the casing 21 is fixed at the planned installation point of the cast-in-place pile, and the excavation equipment 22 such as a drill, auger, or bucket is inserted into the casing 21. Injecting or sinking the casing 21 while excavating the soil inside the casing (21).

Here, the casing 21 is usually made of steel pipe (pipe) to play a role of maintaining the vacant walls of the excavation hole, and as the excavation proceeds to continue to connect a plurality of casing 21 to the ground into the ground .

When the penetration and excavation of the casing 21 to the desired depth of plan is completed, the rebar network 23 assembled on the ground is inserted into the casing 21, and then a treme 24 reaching the bottom of the excavation hole is provided. Install it.

Subsequently, the concrete 31 is poured through the treme 24, and the casing 21 is drawn out, and the treme 24 is also drawn and disassembled to complete the on-site casting pile. Once the support is secured, the next step is to proceed.

In general, the support force of the cast-in-place pile is as shown in FIG. 2 by the point bearing force expressed by the bearing capacity of the hard ground 12 around the pile tip and the friction between the outer circumferential surface of the pile and the surrounding ground. The main surface friction force (柱面摩擦力, skin friction) that is expressed is composed of a combination, as shown in Figure 3, when there is no hard ground (12) expressing the desired ground support force at the pile construction point, the tip support force is expected Since it is impossible to provide the required bearing capacity of the pile, only the frictional force can be designed and constructed, and therefore, there is a serious problem that a pile of large depth can only be adopted to secure the friction area of the pile.

The present invention has been made in view of the above-described problems, the step of injecting the injection tube 25 to the planned point of the cast-in-place pile, and the injection liquid when the tip of the injection tube 25 reaches the planned depth of the cast-in-place pile Pressurizing the 32 and injecting the injection tube 25 when the injection of the injection liquid 32 is completed and the expansion of the ground is completed; and the injection liquid 32 is solidified in the ground to form a solidified body 33. ) And inserting the casing (21) into the planned point of the cast-in-place pile and excavating the earth and sand inside the casing (21), and when the tip of the casing (21) reaches the solidified body (33) (22) retreating and detecting the excavation hole, the step of entering the reinforcing bar network 23 into the casing 21, placing the concrete 31 inside the casing 21 and at the same time the casing ( 21) and the step of curing the concrete (31) to complete the cast-in-place pile integrated with the solidified body (33) Distal end an enlarged field type pouring pile construction method, characterized by true.

Through the present invention, by extending the effective section of the tip end of the pile foundation to induce a mechanical behavior similar to the spread footing, the main surface friction as in the high-functional clay ground ( It is possible to obtain the effect of expressing the desired lower end bearing capacity even in soft ground where only the bearing capacity by skin friction is effective.

As a result, it is possible to reduce the required depth of pile foundation of the soft ground, which is inevitably designed and constructed with a larger depth than other grounds, and can greatly reduce the construction cost.

The detailed configuration and implementation of the present invention will be described with reference to the accompanying drawings.

Figure 4 illustrates the construction process of the present invention sequentially, as shown in the figure, first inject the injection pipe 25 to the planned point of the site-pouring pile.

The injection pipe 25 may be introduced into the ground by a drilling device, etc., and performs a grouting to inject the injection liquid 32 into the ground at high pressure through the injection pipe 25, which is hard. Bishop work on the ground (12) is to drill the borehole once through the drilling equipment, such as the excavation bit at the distal end, and then put a separate miter equipped with a packer at the distal end into the borehole to perform the bishop In the present invention, as a construction method for the soft ground 11, it may be possible to drill and pierce by injecting the forced injection pipe 25 into the ground, so that specific limitations on the penetration method of the injection pipe 25 are given. I never do that.

When the tip of the injection pipe 25 reaches the planned depth of the cast-in-place pile, the injection liquid 32 such as cement liquid or water glass is injected at a high pressure through the injection pipe 25 into the soft ground 11. After inflated at, the infusion tube 25 is drawn out.

The injection liquid 32 injected and expanded into the soft ground 11 is solidified to form a solid body 33. The solid body 33 is mechanically behaved like a kind of spread foot. The lower portion supporting force similar to the tip supporting force is applied to the pile to be bonded to the top of the solidified body 33.

When the solidification of the injection liquid 32 is completed and the solidified body 33 is formed, the casing 21 is introduced into the planned point of the cast-in-place pile, and at the same time, the earth and sand inside the casing 21 are excavated and the tip of the casing 21 is terminated. When the solidified body 33 is reached, the excavation equipment 22 is retracted, and then the preparatory process is performed, such as detecting the eccentricity of the casing 21 and removing the slime inside.

Here, if the tip portion of the casing 21 is constructed so as to be penetrated into the solidified body 33 by a predetermined depth, the attachment area between the concrete 31 and the solidified body 33 is increased when the concrete 31 is poured later, and thus the pile body and the solidified body ( 33) solid connection is possible.

When the excavation work including the inspection is completed, the reinforcing bar 23 is inserted into the casing 21, and a treme 24 is installed so that the end reaches the bottom of the excavation hole. The casing 21 is drawn at the same time as the concrete 31 is poured through the 24, and the trem 24 is also drawn and disassembled.

When the casting of the concrete 31 is completed, the site-casting pile of the present invention is completed by making a solid connection between the pile body and the solidified body 33 through the curing process of the concrete 31.

Figure 5 is a schematic diagram representing the mechanical behavior of the cast-in-place piles constructed through the present invention, as can be seen through the drawing, the cast-in-place piles constructed through the present invention, as well as a kind of enlarged skin friction (skin friction) It can be seen that the lower end supporting force by the solidified body 33 which plays a role such as spread footing also works.

1 is a diagram illustrating a construction process of a conventional cast-in-place pile

2 is a schematic diagram of pile foundations in which the tip bearing capacity and the principal surface friction coexist;

Figure 3 is a pile foundation schematic effective only principal friction

4 is an explanatory diagram of the construction process of the present invention

5 is a schematic view of the site-pouring pile constructed through the present invention

11: soft ground

12: hard ground

21 casing

22: Excavation Equipment

23: rebar network

24: tremie

25 injection tube

31: concrete

32: injection liquid

33: solidified

Claims

Injecting an injection tube (25) into a planned point of the cast-in-place pile;

Pressurizing the injection liquid 32 when the tip of the injection pipe 25 reaches the planned depth of the cast-in-place pile;

Drawing the injection tube 25 when the injection of the injection liquid 32 and expansion in the ground are completed;

When the injection liquid 32 is solidified in the ground to form the solidified body 33, injecting the casing 21 into the planned point of the cast-in-place pile and simultaneously excavating the soil inside the casing 21;

Retracting the drilling rig 22 and detecting the drilling hole when the tip of the casing 21 reaches the solidified body 33;

Entering a reinforcing bar 23 into the casing 21;

Pouring concrete 31 into the casing 21 and drawing the casing 21 at the same time;

A method of constructing a site-mounted pile with a distal end portion, characterized in that the step of curing the concrete 31 to complete the cast-in-place integrated with the solidified body 33.