JPS587033A - Constructing method for foundation endurable to concentrated load employing soft ground mixture processing method - Google Patents

Abstract

PURPOSE:To reasonably transfer a load of a structure to an amended ground and constitute a foundation so that the amended ground and a reinforced core material are monolithically united, by a method wherein the forward end of the core material is expanded in a taper, and the reinforcing material is placed to the upper part of the core material. CONSTITUTION:A core material 4 has a tapered reinforcing material, dispersing a perpendicular force and increasing a support force and a pulling force, at a forward end, and has a reinforcing material 3, dispersing a horizontal force as an adhesive power and preventing the occurrence of a tension destruction of an amended ground 5, at the upper part. Firstly, a soft ground is treated by a depth mixture processing method to construct an amended ground 5. A cure retarding agent is mixed in the ground 5 thereupon to keep the ground in a condition that it is soft enough for the core material 4 to be inserted. The core material 4 already manufactured is then inserted into the ground 5. After allowing the ground 5 to be cured and display a sufficient strength, an upper structure is built.

Description

[Detailed Description of the Invention] This invention provides a pre-concentration type anchor foundation for mooring a floating marine structure in a supporting foundation such as a steel bratform sea berth constructed on the soft ground of the seabed. The present invention relates to the provision of a new method for constructing foundations that can be constructed on soft ground by combining ground improvement and reinforced core material.

Conventionally, steel offshore structures built on soft ground are usually fixed to a seabed support plate with piles.

However, if the soft ground is thickly piled up, the pile length will not be long], and the horizontal resistance will be small due to the softness of the ground, making it difficult to drive piles with large horizontal bites. Therefore, even if the supporting force is sufficient, the pull-out resistance is insufficient, and there are various other problems.

On the other hand, in order to improve the soft ground, the deep mixing method is used to improve the soil, which is a construction method that hardens the soft ground layer by natural sedimentation or burial, and improves the ground to be able to support the upper load. The hardening material is poured into a slurry form at the plant, and then pumped into a deep mixing treatment machine using a hydraulic pump to mix it completely and uniformly over the entire depth of the soft layer in the Kaiarashi range, and to form the ground to obtain the specified strength. However, it is not used as a foundation for steel structures that carry concentrated loads such as those mentioned above, and is most commonly used in ports and harbors that carry distributed loads such as berths and breakwaters. It has been used only as the foundation ground for structures.

This is due to the strength characteristics of the improved soil, which is strong against compression and shear, but weak against tension, as shown in the diagram in 1g, or because the material exhibits brittleness under normal confining stress. ing.

In other words, when a large vertical concentrated load is applied, tensile
This is because piles made by digging with ivy can crack when horizontal force is applied to them, making them unsuitable for use as foundation ground.

In the diagram in Figure 1, qu is compressive strength, tf is shear strength, and Δt is tensile strength *'t-, respectively, and this is for the case where the amount of cement is 15%.

As mentioned above, due to its strength characteristics, the improved ground cannot be used as a foundation for support structures such as steel brat forms and sea berths, or rounded anchors for floating floating offshore structures. As mentioned above, it has been lined and solidified into one piece, so we can take advantage of this condition and make some improvements to the core material to be excavated in this area to improve the ground. If it is possible to create an integrated foundation as a whole by combining it with the core material, there is no need to drive ordinary piles all the way to the seabed support ground K, and the above-mentioned problem due to the presence of a soft ground layer in the middle can be resolved. Therefore, it is suitable because it will contribute to expanding the field of application of the deep mixing method.

The present invention was made in view of the above points, and its purpose is that when vertical, horizontal, and moment concentrated loads act on the foundation, such as steel structures such as sea berths, the mechanics of improved soil By using specially devised steel and other reinforcing core materials to disperse concentrated loads in a rounded shape that prevents the soil from breaking easily due to its characteristics, the improved soil is made with #1 so that the load is transmitted smoothly to the improved soil. It is possible to use it as a concentrated load-resistant foundation where the reinforcing core material behaves as one.

A detailed explanation will be given below based on the t-diagram.

In other words, as a core material, improve the concentrated load:.

The adhesion force of the curved surface of the core material and the dispersion of the support reaction force by expanding the shape of the tip and the tension of the upper part 1141
Reinforcement has been applied to prevent collapse, and by making the entire improved ground work as a larger unified foundation, the reaction force on the bottom and 11 sides is reduced, strength is reduced, and resistance to deformation is increased. As a strong foundation, Quo 9, as shown schematically in Figure 2, a 4t core material with reinforcement 1.2.3 at the tip, middle and upper part - concentrated load resistant foundation with a structure installed on the improved ground 5. The core material 4 is mainly made of steel pipe, etc., and has a tapered reinforcing material 1t at the tip to disperse vertical force and increase supporting force and pulling force. 4 reinforcing materials 3 to disperse horizontal force as attachment force and prevent tensile failure of the improved soil, and furthermore, if necessary, reinforcement w2 in the middle to increase attachment force. Made of steel, reinforced steel, or steel-framed concrete. belongs to.

The procedure for creating this foundation is shown in Figure 3.

First, the soft ground is treated using the deep mixing method to create improved ground 5 that is mechanically continuous.

At this time, improved jl! If the disc is large, a hardening retardant f must be mixed in to ensure the strength of the bonded part and to keep it soft enough to allow insertion of the core material 4 (Figure a).

Next, the already produced core material 4 is inserted and installed. When inserting, it is installed at a predetermined depth and plane position not only by its own weight but also by applying pushing force or vertical movement (Figures b and a).

Wait until the improved ground 5 has hardened and exhibits sufficient strength. After that, the upper structure is attached (not shown).

The mechanism of load transfer from the superstructure to this foundation can be briefly described as follows.

Compression, pull-out vertical loads, horizontal loads and moments from the superstructure - top, middle and tip reinforcements 3.2.
11i-, the improved ground 5 and the core material 4. It is thought that it behaves as a unified foundation.

Therefore, in designing, the necessary size and shape of the improved ground 5 are first determined by considering the stability of the improved ground 5 as a whole against concentrated external forces, ie, sliding slippage, supporting capacity, etc.

Depending on whether or not it is anchored to the sand and gravel layer below the soft layer, it is classified into support type and friction type foundations.

Additionally, the required strength of the improved ground 5 can be determined from the internal stress.

Furthermore, it is necessary to consider the adhesion force, supporting force, and pull-out force against vertical loads, as well as the adhesion resistance against horizontal loads and moments, and the bending resistance. , 3 no gis? and material can be determined.

A conceptual diagram of such a design is shown in Fig. 4A and Fig. 4C shows a possible structural design example.

Further, FIGS. 5a and 5b show examples in which this foundation is used as a support foundation for a marine structure 6 and as an anchor foundation for a floating marine structure 7, respectively.

With such a concentrated load-resistant foundation KTo, improved soil can be used as needed, so it can have a large bearing capacity and horizontal resistance. Since the friction on the horse's surface provides resistance, it can provide a large amount of pulling resistance.

As described above, the present invention is a steel platform as a marine structure.
It is extremely useful as a support foundation for sea berths, power transmission towers, etc., or as an anchor foundation for floating offshore structures such as nuclear power plants.

[Brief explanation of drawings]

Figure 1 is a t-arasu chart of the strength characteristics of the improved ground obtained by the deep mixing method, Figures 2a and b are a plan and front view schematically showing the foundation in the present invention, and Figure 3a is a diagram. b80 is a diagram of the foundation construction procedure of the present invention, Figure 41 is a conceptual diagram of the design of the foundation of the present invention, Figure 11iIbso is a diagram showing an example of a structural design that can be considered with this, and Figure 5 is an example of the use of the foundation of the present invention. FIG. 1.2.3... Reinforcement material, 4- Core material, 5... Improved ground. /? /l τ □□□□□□-'' vortex 0 2O N/m2) -z history 0゜4 3ゝ5 3 4 2 1 y ω 3m a, b・ a, b・

Claims (1)

[Claims] By utilizing the initially soft nature of the improved ground prepared by the deep mixing method that uses a slurry hardening agent, the load is distributed in advance to the tip, middle, and upper part of the ground, and the improvement is carried out. A core with reinforcement material attached to prevent ant in the ground is inserted and installed, and after hardening, it can be used as a support foundation or anchor foundation for marine structures that can survive concentrated loads. Foundation construction method.