JPH0441728B2 - - Google Patents

Description

[Detailed Description of the Invention] (Industrial Application Field) The present invention relates to a method for reinforcing foundation piles, in which a foundation pile supporting a structure is mounted on a building foundation (footing) connected to the structure. This relates to a construction method that increases the horizontal bearing capacity.

(Conventional technology) In recent years, as a method to increase the horizontal bearing capacity of foundation piles, we have moved away from the conventional method of increasing the pile diameter or increasing only the bending capacity of the piles, and have begun to connect the upper parts of the piles to each other. Foundation and pile head reinforcement construction methods have been developed, and among these, the head reinforced pile foundation, which is particularly difficult, involves driving piles 3' into the ground and surrounding the pile head for a considerable length, as shown in Figure 10. The outer shell steel pipe 4' is sunk, and concrete is poured inside it and across the pile material. Awarded as a highly reliable foundation structure because the area in contact with the ground is increased to make effective use of the ground, and damage such as cracks that occur during driving in the head, which is difficult to loosen, can be reinforced with concrete filled with steel pipes on the outer shell. It is used.

(Problem to be Solved by the Invention) However, as described above, the pile head-reinforced pile foundation is constructed by driving the piles into the ground, then digging up the ground around the piles and inserting the piles into the piles from above. Since the outer shell steel pipe is crowned and the gap formed between the piles and the steel pipe is filled with concrete from above, it is not suitable for existing buildings where the building foundation is placed on top of the piles. Can not do it. In other words, because the building foundation is located above the pile head, it is not possible to install the outer shell steel pipe around the pile from above, and furthermore, the installation location of the pile is completely underground, making construction difficult. , which requires many construction methods and costs.

(Means for Solving the Problems) In contrast, the present invention forms the above-mentioned outer shell steel pipe as a vertically split two-part member so that it can be attached to the pile from the side, and Furthermore, by forming it into multiple short tubes and press-fitting them one by one using jacks, it is possible to limit the earth and sand excavation for pile head reinforcement work to the minimum work area, which is different from other construction methods. This construction method is much cheaper and less dangerous in construction.

(Embodiments of the invention) To explain the order and drawings for implementing the method of this invention, (1) After driving sheet piles 2 along the perimeter of the building foundation of an existing structure and applying earth retaining, Excavate that area to a depth of approximately 150cm to expose the top of foundation pile 3 (Figure 1).

(2) Surrounding this foundation pile 3, there are two halves 4c, 4c each having a semicircular cross section as shown in FIG. The same side of the base pipe 3 is approximately
Slanted bent edges 4 surrounding at 25mm intervals
a, 4a are pushed into the ground and set upright, and the contact side edges of these two halves 4c, 4c are connected by welding (w) to form an integral outer shell steel pipe 4 (third
figure).

(3) Thick plates 5a, 5a in the shape of a circular ring divided into two as shown in FIG. After that, three jacks (30 to 50 ton jacks) 6, 6, 6 are placed surrounding the foundation pile 3, with their lower ends positioned on the support plate 5, and the upper ends of the jacks made of the same two-split thick plate. Support plate 7
(Fig. 5).

(4) Operate the jacks 6, 6, 6 to remove the outer shell steel pipe 4.
Press fit and lower to the required depth. This operation is performed as many times as necessary depending on the depth of the part to be reinforced. Then remove the jacks 6, 6, 6 (Figure 6).

(5) Between the upper end surface of the embedded outer shell steel pipe 4 and the lower surface of the building foundation footing 1, the two-split member 4c is installed.
The uppermost outer shell steel pipe 8 is formed by positioning two split members 8a, 8a having the same shape as shown in FIG. Two split flange members 9b, 9b having an inlet 9a are attached with their flange surfaces pressed against the lower surface of the building foundation footing 1, and both ends are welded to form an integral flange 9, and the flange surfaces are attached to the lower surface of the building foundation footing 1. Attached with bolts to the flange 9 and the upper outer shell steel pipe 8, the upper and lower outer shell steel pipes 8,
4 etc. are connected together by welding (Fig. 8).

(6) Connect the mortar inlet 9a provided on the flange 9 to a concrete pump, and press-fit mortar (non-shrinkage mortar or regular mortar) 10 between the periphery of the foundation pile 3 and the outer shell steel pipe ( Figure 9).

Next, the sheet piles 2 are removed and backfilled, thus forming a reinforced pile foundation with increased horizontal force that extends below the existing building foundation.

In this way, the short cylindrical outer steel pipe 4 is press-fitted using the jack 6, and the outer shell steel pipe is successively added according to the construction depth to form the outer shell steel pipe of the required length. Even in the lower part of a building, the number of holes drilled to secure only the working space can be kept to a minimum, making it possible to perform extremely efficient work with only a small amount of excavated soil. The length of the entire outer shell steel pipe is determined by the short length that should be press-fitted according to this length, as it is necessary to enclose the part above the bottom of the assumed maximum bending moment caused by horizontal force such as an earthquake in foundation pile 3. It is determined by the number of cylindrical outer shell steel pipes.

(Effects of the Invention) According to the present invention, as detailed above, it is possible to easily reinforce foundation piles in an existing building against horizontal forces. If the structure of the building foundation is such that it cannot support the upper part of the jack, it is sufficient to tighten and fix a support band made of two halves to the top of the foundation pile, and use this support band to support the upper end of the jack. In any case, a reliable pile foundation with reinforced pile head can be obtained.

[Brief explanation of drawings]

1 to 9 are explanatory diagrams showing the order in which the method of the present invention is carried out, in which FIG. 1 is an excavated state, FIG. 2 is a slope view of the two-split member, and FIG. 3 is an outside view. Figure 4 is a plan view of the support plate; Figure 5 is the state in which the shell steel pipe is rolled down with the same jack; Figure 6 is the state in which it is embedded; Figure 7 is a slope view of the flange 9;
The figure shows a state in which the upper shell steel pipe is attached, FIG. 9 shows a state in which pile head reinforcement has been completed, and FIG. 10 is an explanatory sectional view of a conventional pile head reinforced pile foundation. 1...Building foundation footing, 3...Foundation pile,
4... Outer shell steel pipe, 4a... Gradient analysis curve, 5... Support plate, 6... Jacket, 8... Upper outer shell steel pipe, 9
...Flange, 9a...Mortar injection port, 10...
…mortar.

Claims (1)

[Claims] 1 Excavate the lower part of the foundation footing to expose the upper part of the foundation pile, surround the upper part of the foundation pile with a halved short cylindrical outer shell steel pipe, weld the steel pipe joints to form a cylinder, and then The steel shell tube is press-fitted into the soil using a jack installed directly under the foundation footing, and then the same halved short cylindrical steel shell tube is added and welded on top of this steel shell tube, and the outer steel tube tube is replaced by jacks again. The body is press-fitted into the soil, and this halved short cylindrical outer shell steel pipe is press-fitted into the soil and additionally welded a desired number of times to surround the foundation pile with the outer shell steel pipe body, and the gap between the foundation pile and the outer shell steel pipe body is closed. A foundation pile reinforcement method characterized by injecting and filling mortar.