JPS61158528A - Foundation structure in soft ground and building thereof - Google Patents

Abstract

PURPOSE:To build a foundation at a low cost and in a short time and safely, by a method wherein a cylindrical structure is sunk in a soft ground for installation so that its lower end part is suck down to a hard ground, and soft soil in the cylindrical structure is improved to build a bridge pier. CONSTITUTION:A cylindrical structure 1 is sunk in a soft ground 3 for installation, and its lower end part is suck down to a hard ground 4. Soft soil 3a in the cylindrical structure 1 is improved into a hard excellent ground 5 by a ground improving method, but in case a ground is improved by a deep-seated mixing processing method, a work is carried out so that it is completed within one month. A bridge pier is built on an improved excellent ground 5 within the cylindrical structure 1. This enables building of a support ground which is sufficiently durable to even a structure, such as bridge pier, by which a huge vertical force is exerted thereon.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application This invention relates to a foundation structure on soft ground and a construction method thereof.

Problems with conventional technology Generally, huge vertical forces act on bridge piers and abutments.

Therefore, the foundations of bridge piers and abutments must be constructed on the ground that can withstand this.

By the way, conventional methods of improving soft ground into hard ground and constructing structures on this soil layer are often used when constructing port structures. However, with existing ground improvement methods, it is almost impossible to create a hard enough ground to support structures such as bridge piers that are subject to huge vertical forces. Not implemented.

For this reason, when the surface layer is soft ground or the hard ground is thin, methods are implemented in which piles are installed under the piers or caissons are installed to transmit the force acting on the piers to the expected ground. ing.

However, when using piles to support the structure, the diameter and number of piles are quite large, and the length is also very long, making construction extremely difficult and significantly increasing construction costs.

Furthermore, the support method using caissons requires the installation of reinforcing bars and steel frameworks within the caisson, which also have to be sunk deep into the ground, which significantly increases construction costs.

Purpose of the Invention The present invention was proposed to solve the above-mentioned conventional problems, and it is possible to build foundations for bridge piers, etc., safely, in a short period of time, and at a much lower cost than using piles or caissons. The purpose of this invention is to provide a foundation structure that can be constructed on soft ground and a method for its construction.

Structure of the Invention The construction method according to the present invention involves depositing a large-diameter cylindrical structure made of steel plate cells or the like in soft ground (usually submarine ground) with its lower end reaching hard ground; The above objective is achieved by improving the soft ground within a structure to a good quality ground using conventional ground improvement methods such as sand compaction or deep mixing method, and constructing foundation structures such as bridge piers on this ground. It is.

Further, the cylindrical structure used in this construction method is constructed of steel or prestressed concrete members that have extremely high member strength such as tensile strength, and is constructed as an integral type or an assembly type that can be assembled on site.

Furthermore, the cross-sectional design has been designed to be strong enough to withstand the bending and compressive forces that occur when the bridge is submerged, and since it is often installed on the seabed when constructing supporting ground for bridge piers, it is necessary to have semi-permanent durability. It is designed to. For example, if the material is steel, the amount of corrosion in soil or water is generally small, so if the thickness of the plate is determined taking into account the corrosion rate, it can be considered to have semi-permanent durability. The shaped structure is constructed in a shape close to a perfect circle,
Items that cannot be approximated to a perfect circle, such as quadrilaterals, are not suitable.

Example Hereinafter, the construction method according to the present invention will be explained in order.

■ First, a large diameter cylindrical structure (hereinafter referred to as the cylindrical structure) 1 is transported to the installation site by a crane ship 2 and installed on the soft ground 3 on the seabed (see Figures 2 and 3). .

(2) Subsequently, the cylindrical structure 1 is sunk into the soft ground 3 by a construction method such as press-fitting, and its lower end is made to reach the top of the hard ground 4 (see Fig. 4).

It is assumed that the work of sinking the cylindrical structure 1 will be completed within one day.

(2) Next, the soft ground within the cylindrical structure 1 of ±3a is improved to a hard, good quality ground 5 by a conventional ground improvement method such as sand compaction or deep mixing method. (See Figure 5). If ground improvement is carried out using the deep mixing method, it will generally be completed within one month. In the figure, numeral 7 is a soil improvement ship.

■ Next, the improved high-quality ground 5 inside the cylindrical structure 1
Build the upper pier 6 (see Figure 6).

Note that the diameter of the cylindrical structure 1 is determined depending on the scale of the structure to be constructed thereon.

Effects of the Invention The construction method according to the present invention does not have the above-mentioned configuration.According to this construction method, soft ground is improved to hard, good quality ground using conventional ground improvement methods, and the surrounding area is further surrounded by a cylindrical structure. It is possible to create a supporting ground that can sufficiently withstand structures that are subject to huge vertical forces, such as those that are subject to a huge vertical force. Therefore, if you use this as the foundation ground and build structures such as bridge piers directly on it, it will be much more economical, shorter, and safer than constructing pile foundations or caisson foundations. be able to.

[Brief explanation of the drawing]

Figures 1 to 6 show the construction method of the present invention, with Figure 1 being a sectional view of the improved ground, and Figures 2 to 6 being process charts of the construction method. l... Cylindrical structure, 2... Crane ship, 3... Soft ground, 3a... Soft soil, 4... Hard ground, 5... Good quality ground, 6... Bridge pier. Figure 3 Figure 5 Figure 4

Claims (2)

[Claims] (1) A foundation structure on soft ground characterized by improving the internal soft soil and constructing a pier on top of a cylindrical structure sunk in hard ground soil. (2) A cylindrical structure is sunk in soft ground with its lower end reaching the hard ground, and then the soft soil within the cylindrical structure is improved and a pier is constructed on top of it. Features: Construction method for foundation structures on soft ground.