JPS638245B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a ground improvement method for soft ground such as a clay layer.

Ground improvement methods for such soft ground include consolidation promotion methods such as sand drains and paper drains, and solidification methods using chemical injection, but all of these methods take time to produce improvement effects and require a large amount of soil. It has the disadvantage of high cost due to the need to use ground improvement agents, and further disadvantages such as increased consolidation settlement of soft ground such as clay layer beneath the improved ground due to increased weight. It was hot.

For example, Japanese Patent Application Laid-Open No. 50-26310 discloses a technique for forming a square-shaped hardened wall that reaches the hard surface during ground improvement. However, such known techniques require a large amount of soil improvement material, and the construction period becomes long, resulting in increased costs.

The present invention was made in order to eliminate the above-mentioned drawbacks of conventional ground improvement methods, and allows the effect of ground improvement to be achieved at an early stage, minimizes consolidation settlement deeper than the improved area, and can be carried out at the lowest possible cost. This was done with the aim of providing a ground improvement method for soft ground that can be improved.

Therefore, according to the ground improvement method according to the present invention, in the method for improving soft ground such as a clay layer, a guide hole is drilled in the soft ground, and the guide hole is used to drill into the soft ground in the vertical direction and By spraying membrane material horizontally at predetermined intervals to form a flexible, water-impermeable membrane in the vertical and horizontal directions, the membrane divides the soft ground into blocks and wraps them. A ground improvement method is provided in which pore water is sealed in each block and the entire block is floated into the surrounding soft ground.

Here, as the film-forming material, materials suitable for the rigidity of the ground, such as water glass, asphalt, and cement, can be suitably used. In this way, by dividing soft ground such as a clay layer into a large number of blocks that are wrapped both vertically and horizontally by flexible membranes that do not allow water to pass through, the pore water in the soft ground is encapsulated in each block. An apparent overconsolidated ground is created, and the overconsolidated ground divided into blocks floats into the surrounding soft ground, thereby preventing ground subsidence.

The construction method of the present invention does not completely prevent ground subsidence, but rather reduces the amount of subsidence as much as possible.
As the flexible membrane is compressed as it sinks, it does not bear any load, so the membrane will not be destroyed and its effectiveness will not be lost. In addition, the tensile strength, water permeability, spacing between membranes, etc. of the membrane are determined as appropriate, taking into account the condition of the ground to be constructed.

By adopting such a ground improvement method, the amount of consolidation settlement of the soft ground deeper than the improved area will be minimized, and the improvement effect will be immediately apparent once the membrane is strong. Furthermore, the film can be formed using the jet grouting method, which is relatively inexpensive, requires only a small amount of material, and exhibits excellent effects such as a small amount of excavation slippage.

Note that in carrying out the present invention, the order of the steps for forming the horizontal film and the vertical film is arbitrary, and it is clear that either one may be performed first.

Further, in order to form a film in the lateral direction, a plurality of stages may be formed at once, or a plurality of stages may be formed one step at a time.

Embodiments of the present invention will be described below with reference to the drawings, taking as an example a case in which the method of the present invention is implemented to improve clay ground.

As shown in FIG. 1, a vertical guide hole 2 is drilled in the clay ground 1A to be improved, and a multistage cross or Y-shaped monitor 3 is inserted into the hole. While rotating this monitor 3, a high-pressure water jet of 3000Kg/cm ² , 50/min water and membrane materials such as water glass, asphalt, cement, etc. mixed according to the rigidity of the ground, as well as induction materials and shear. Air as a conveying material is injected from separate nozzles. As a result, circular membranes 4a as shown in FIG. 2 are formed in the clay ground 1A at predetermined intervals in the vertical direction.

Next, the monitor 3 is pulled up by 1 to 3 m and the same operation is performed to sequentially form horizontal circular films 4b, 4c ₁ . . . in the clay ground 1A. Note that the spacing between the films, the thickness of the films, the reach length of the film material, etc. are determined as appropriate depending on the degree of improvement. The thickness of the membrane is usually about 10 cm.

Next, as shown in Figure 3, the monitor 3 is lowered into the guide hole 2 again, this time the rotation of the monitor 3 is stopped, and while continuous injection is being performed, the monitor 3 is gradually pulled up and the vertical direction is moved as shown in Figure 4. membrane 5
a, 5b... are formed.

Thereafter, guide holes 2 were drilled at a pitch twice the range of the monitor 3, and the above operations were performed sequentially to create a flexible, water-impermeable membrane vertically and horizontally in the clay ground 1A, as shown in Figure 5. As shown, clay ground 1A is divided into blocks and wrapped with membranes 4 and 5.
As a result, the pore water in the clay ground 1A is enclosed in each block, creating an apparent overconsolidated clay. Such flexible and water-resistant membranes 4, 5
A large number of blocks wrapped vertically and horizontally are combined into one, and the surrounding clay ground 1
It will be in a floating state at A.

Figure 6 shows improved ground 1 improved by the above method.
A building 6 is erected at B, and the building 6 is supported by a floating foundation, that is, improved ground 1B. 7 indicates a hard foundation ground.

As explained above, the ground improvement method of the present invention is
By forming a flexible membrane that is difficult for water to pass through in the soft ground in the vertical and horizontal directions, and dividing the soft ground into blocks and wrapping them with this membrane, the pore water in the soft ground is sealed in each block, and the Since the entire block is floated as one piece into the surrounding soft ground, the weight of the improved ground does not increase substantially, and the amount of consolidation settlement deeper than the improved area is minimized. At this time, since the membrane is a flexible membrane, it will not be compressed as it sinks and bear any load, so the membrane will not be destroyed and its effectiveness will not be lost. Moreover, if the strength of this film is developed, the improvement effect will be immediately exhibited. Furthermore, when forming the film, it is possible to use the jet grouting method, which is relatively inexpensive to construct, and since it is sufficient to form a relatively thin film in soft ground, only a small amount of material is needed, and the amount of drilling is small, compared to the conventional method. It has many excellent effects, including being cheaper to implement than conventional construction methods. For this reason, it is particularly effective in improving ground where the foundation ground is deep and the soft ground layer is thick, making construction difficult in the past.

[Brief explanation of the drawing]

The drawings show an example in which the method of the present invention was implemented for ground improvement in a clay layer. Figure 1 is a longitudinal section showing a state in which a monitor is inserted into a guide hole drilled in a clay layer to form a horizontal membrane. Figure 2 is a plan view of the membrane in the horizontal direction, Figure 3 is a longitudinal sectional view showing the state in which the monitor is inserted into the guide hole again after forming the membrane in the horizontal direction, and Figure 4 is the membrane in the vertical direction. Figure 5 is a front view of the building, Figure 5 is a perspective view showing the state in which the clay layer is divided and covered by vertical and horizontal membranes, and Figure 6 is a floating view showing the state in which the building has been erected on the improved floating ground. It is a vertical cross-sectional view of the ground. 1A...Clay ground, 1B...Improved clay ground, 2...Guide wheel, 3...Monitor, 4
...Horizontal film, 5... Vertical film, 6...
Building, 7...Foundation ground.

Claims (1)

[Claims] 1 In the method of improving soft ground such as clay layer, multiple guide holes are drilled in the soft ground, a monitor is inserted into the soft ground using those guide holes, and the monitor is placed at a fixed position. The membrane material is sprayed while rotating to form multiple rows of flexible horizontal membranes that are impermeable to water, and multiple rows of vertical membranes are formed by moving the monitor up or down without rotating it. It is characterized by dividing the soft ground into blocks and enclosing them with a membrane, thereby sealing the water in the soft ground into each block, and making the entire block float into the surrounding soft ground as one unit. Ground improvement method.