JPS59130913A - Soft ground improvement work - Google Patents

Abstract

PURPOSE:To reduce the weight of a structure by raising the sliding resistance of a superstructure to be placed on the improved ground by a method in which a solidifying agent is charged slantly into soft ground and mixed the soil with stirring in such a way as to harden and improve the ground to form skew improved soil pillars or walls. CONSTITUTION:Unimproved ground in the seabed is removed to some extent, and improvement in the vertical direction is made on the ground in the same way as in the usual method to form a vertically improved ground 2. Furthermore, improvement in the slant direction is made on the ground to form a slantly improved ground 3. When a heavy structure 1 is constructed on the improved ground, the horizontal force acting on the structure 1 is transmitted to the slantly improved ground 3 through oblique planes 4 formed by slantly cutting the bottom of the structure 1.

Description

[Detailed Description of the Invention] An improved form of the deep mixing method, which is one of the soft ground improvement methods, is as shown in Figure 1. The main purpose is
The improved soil pillar or wall C, which is the improved ground, was constructed vertically.

The ivy improved soil pillar or wall C is made by putting an assimilating agent into the soft ground.
Obtained by stirring and mixing to improve the hardening of soft ground.

The soft ground improvement work vessel d used for the Suntako construction method is the second
As shown in the figure, the turret f for raising and lowering the agitator e that performs the agitation and mixing described above is tilted vertically and cannot be lowered. won.

Therefore, with conventional improved construction methods and improved work vessels, the vertical bearing capacity can be addressed by increasing or decreasing the improvement rate and selecting the type of improved ground, but the ground does not have any bearing capacity against the horizontal load acting on the superstructure a. It was so hard to increase the power. In other words, the improved ground could not be expected to significantly increase the resistance to sliding between the structure and the improved ground.

Therefore, many of the structures installed on the improved ground using deep layer and mixed treatment methods are gravity type, and are subject to seismic loads, wave loads, etc.
By increasing the weight of the structure against large water pressures such as water pressure, it can be expected to increase frictional resistance.In other words, it can resist not only lead force but also water debris movement, and the improved ground can absorb horizontal force. There was a need for construction that would provide an improved form of construction.

SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide a method for improving soft ground that eliminates the drawbacks of the conventional method and improves the ground to effectively resist horizontal external forces.

The feature is that assimilating agent is put into the soft ground, and 13
In the method of hardening and improving soft ground by stirring and mixing, the soft ground is hardened and improved into diagonal improved soil column dimensions or wall shapes, and the diagonal improved soil column dimensions or walls also resist horizontal sliding. Because I can.

The weight of the superstructure placed on the improved soft ground can be reduced.

Embodiments of the present invention will be described in detail below with reference to the drawings.

Figures 3 and 4 show examples of soil improvement types, and Figures 5 and 6 show examples of the work carried out by the improvement work boat used for the construction.

There are two types of improvement, as shown in Figures 3 and 4. Type A, shown in Figure 3, eliminates unimproved ground to some extent, and Type B, shown in Figure 4, does not require it at all. It is. In each figure, (1) is a gravity-type structure, (2) is a conventionally improved vertically improved ground, and (3) is an obliquely improved ground, which is the main point of the present invention to absorb horizontal forces acting on the structure. shows.

In this ground improvement example, the horizontal force acting on structure (1) is
) is transmitted to the ground through the slope part (4) which has an obliquely missing bottom part and the slope of the mound (5) installed on the ground or ground - A, and the force is resisted by the improved ground constructed diagonally. It is something. The type of diagonal improved ground (3) may be pile type, column type, wall type, or a combination thereof.

For vertically improved ground (2) and diagonally improved ground (3), a solidifying agent is added to the soft ground (6), stirred and mixed, and the improved column i
Or get the wall.

Furthermore, the B type mound (5) shown in Figure 4 is made of rubble.
It is made of reinforced concrete and steel and is installed on the ocean floor. In the figure, (6) indicates reinforcing bars, steel frames, etc. that are sledded after construction of the improved ground (3) in order to increase the shear resistance of the diagonally improved ground (3) and the mound (4).

Figures 5 and 6 show specific examples of soft ground improvement work vessels. The condition shown in Figure 5 is the vertically improved ground (
2), the state shown in Figure 6 shows the state in which the diagonal improved ground (3) in Figures 3 and 4 is constructed. The structure of each part shown in Figures 5 and 6 is as follows:
Reference numeral 8) is a turret tiltably supported on the hull (7), and reference numeral 9 is a skid, which can be moved back and forth and left and right as in the conventional case. Furthermore, O■ indicates a hydraulic or air cylinder for tilting the turret (8), and (Il
1 is an agitator that unloads the cargo by docking on the turret (8). Therefore, when constructing columns or walls on the diagonally improved ground (3), construction can be performed at any inclination angle by adjusting the expansion and contraction of the 7 Linder 00).

In this way, the upper structure (1) is constructed using the diagonally improved ground (3).
It is possible to increase the sliding resistance due to the horizontal force acting on the surface. The reason for this is as follows.

The stability of the superstructure and the bearing capacity of the ground are generally expressed as follows according to Figure 7.

W: Vertical force acting on the structure H: Horizontal force acting on the structure R: Vertical bearing capacity of the ground S: Horizontal bearing capacity of the ground (
In FIG. 7, A is the superstructure and B is the ground. ) In the above relationship, the requirements for structure A to be stable are as follows:'1 (1) R≧W and (2) S≧H (1) In the case of soft ground, the requirements for improvement are: By applying this, the salt content of R can be reduced to meet the requirements.

On the other hand, requirement (2) cannot be satisfied simply by increasing the strength of the ground. This is because the horizontal supporting force S of the +lh board B is generally expressed by the following equation.

S-μ・W (μ: coefficient of friction between the ground and structure), that is, the horizontal supporting force S is determined only by the coefficient of friction μ and the vertical force W, so the force that increases the weight of structure A; increases the coefficient of friction. It can be increased by However, the coefficient of friction is mainly related to the roughness of the contact surface, and is not influenced much by the strength of the ground.

Therefore, as in this embodiment, by making the inclined surface lean against the structure, the eighth
As shown in the figure, it is a good idea to resist the horizontal component of the diagonal ground support force T by one horizontal force H. .

Therefore, the following effects are achieved.

In conventional gravity-type structures, the soil bearing capacity can be improved by increasing the soil improvement rate, but the sliding resistance against large horizontal forces can be improved by increasing the effective ground pressure of the superstructure, that is, by increasing the structure's positioning. Whereas previously the only option was to increase the power by adding ballast, etc., the diagonal ground improvement pillars (walls) increase the sliding resistance, so the weight of the superstructure can be reduced. This has the ripple effect of reducing the ground improvement rate.

By installing the curved slope (4) in advance on the ground (or mound) and the bottom of the structure, it will serve as a guide when the structure (1) is being sunk, allowing easy installation positioning.

In this example, the vertical improved soil pillar or wall-like hardening improvement was performed, but this may be omitted if the vertical soil bearing capacity of this portion is sufficient. That is, the upper structure may be provided with an inclined surface, and the soft ground in contact with this surface may be inclined to improve hardening.

In short, according to the invention.

In the method of hardening and improving soft ground by adding a hardening agent into the soft ground and stirring and mixing, the soft ground is hardened and improved into diagonal improved soil pillars or walls, which are placed on improved land M and L. The sliding resistance of the superstructure can be increased and thus the weight of the structure is also reduced.

[Brief explanation of the drawing]

Figure 1 is a side sectional view of the improved ground showing an example of building a structure on improved ground that has been improved from conventional soft ground. Figure 2 is a side view of the soft ground improvement work boat used for the construction. :
Figures 3 and 4 are based on the construction method according to the present invention. First improved ground
．． A side sectional view showing the second example, Figures 5 and 6 are side views showing the working state of the soft ground improvement work boat used in the construction, and Figures 7.8 are the stability of the superstructure and the rigidity of the ground. FIG. ]゛... Gravity type structure, 2... Vertical improved ground, 3.
・・・Diagonal improved ground, 4...Slope part; 5...Mau/
8 Figure 4 Figure 5 @ Figure 7 Figure 8

Claims (1)

[Claims] A method for hardening and improving soft ground by putting an assimilating agent into the soft ground and stirring and mixing it, which is characterized by hardening and improving the soft ground into diagonal improved soil column dimensions or wall shapes.