JPS61106817A - Method of replacing ground with crushed stones - Google Patents

Abstract

PURPOSE:To form a stable ground, by a method wherein crushed stones are banked on the surface of an unstable soft soil, and soft soil is replaced with crushed stones through utilization of a water flow. CONSTITUTION:Through the driving of a water pouring pump 9, installed within a temporary fence of steel sheet piles 4, sea water is poured on crushed stones 8. The sea water flows through a crushed stone 8 layer into the surface of soft soil 3, and is accompanied by the soft soil 3 to produce muddy water which flows through slits 6 into a shallow sump 5. The muddy water is pumped up with the aid of a drainage sand pump 7 to remove the muddy water through a feed mud pipe 10. This causes the crushed stones 8 to be sunk and enables the soft soil 3 to be replaced with the crushed stones 8.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention replaces soft ground with crushed stones to form stable ground.

Problems that the invention aims to solve During normal times, seawalls and structure foundations are stable and perform their functions, but during earthquakes, the soft soil deforms or liquefies due to vibrations and collapses, causing loss of bankwall and foundation functions. There is.

For the above-mentioned ground, it is necessary to reconstruct the structure itself or improve the ground.

Conventional ground improvement methods include removing soft soil and replacing it with good quality soil, and strengthening soil by injecting stabilizers into the soft soil.

The present invention is a replacement method, and its features are as follows.

(1) To remove soft soil, instead of using general excavation, soil particles are guided into the kamaage by water flow and removed by a submersible sand pump installed in the kamaage.

(2) Crushed stones, etc. that were piled up on the soft soil in advance will be removed in an amount equivalent to the soft soil removed. Sediment.

(3) By the continuous operation of (1) and (2), unstable soft soil is replaced with stable crushed stone, etc.

Advantages of the present invention are (1) the stability of the existing structure is not compromised during the replacement work;

(2) Noise and vibration during replacement work are extremely small.

(3) No pollution as no chemicals are used.

Means and Embodiments for Solving Problems The present invention surrounds the ground improvement area with steel sheet piles, etc., provides a pumping and drainage slit kettle in the surrounding sheet pile, and piles up crushed stone between the kettle and the sheet pile.

After that, water is injected onto the crushed stone, and the injected water is pumped up by a sand pump inside the pot. The injected water flows through the interface between crushed stone and soft soil into the pot. The inflowing water carries soil particles into the kettle, and the inflowing soil particles are replaced by crushed stone.

Examples will be described below with reference to the drawings.

In Figures 1 and 2, 1 is the existing seawall facing the sea 2. The seabed in front of the seawall 1 is a loose sand layer that liquefies during an earthquake, and this is replaced with crushed stone to strengthen the seawall 1. First, a temporary enclosure is provided by erecting steel sheet piles 4 in the area where the ground is to be replaced, and a drainage slit kettle 5 is built in the center of the enclosure.

In this case, the steel sheet piles 4 and the pot lifts 5 need to be built at the depth of the ground where they will be replaced or deeper. The drainage slit kettle 5 has a cylindrical shape, and has a slit 6 at its lower end that allows water and soil particles to pass through, but does not allow crushed stone to pass through. , , ij ＃＊
"j-y)" g y 7' 7 t Rt L"C
k < o Hr 1゛Crushed stone 8 inside the temporary enclosure of steel sheet pile 4
is raised and a water injection pump 9 installed outside the temporary enclosure is operated to inject seawater onto the crushed stones 8. The seawater passes through the 8 layers of crushed stones and reaches the surface of the soft soil 3, which turns into muddy water accompanied by the soft soil 3 and flows into the pot 5 through the slit 6. This muddy water is pumped up by a drainage sand pump 7 and removed via a mud feeding pipe 10. In the space where the soft soil 3 was removed, the crushed stone 8 piled up on the surface sinks, and as shown in Figure 3, the soft soil ±3 is crushed stone 8.
replaced by

Once the replacement is complete, the steel sheet piles 4 and the kettle 5 are removed. The crushed stone after replacement can be piled up to the height of the steel sheet pile.

Function/Effect This invention consists of the above configuration. In this construction method, soft soil is removed along with the flow of water, and after removal, crushed stone placed on the ground surface sinks and is replaced.

Therefore, unlike the conventional method of excavating and removing soft soil, there is no risk of impairing the stability of surrounding existing structures, even if they are close to the soft soil to be replaced, such as the existing revetment in the embodiment. In addition, this construction method does not generate noise, noise, or vibration, and there is no environmental pollution caused by chemical solutions.

It goes without saying that this construction method can also be applied to the replacement of soft soil on land in addition to the above embodiments.

[Brief explanation of the drawing]

The drawings show an example of this construction method, and are shown in Figure 1.
FIG. 2 is a plan view and longitudinal sectional view before replacement, and FIG. 3 is a longitudinal sectional view after replacement. 1. Existing seawall, 2. Sea, 3. Soft soil, 4. Steel sheet pile, 5. Drainage slit kettle, 6. Slit, 7.
Drainage sand pump, 8... crushed stone, 9... water injection pump, 1
0...Sludge pipe. Scene 1 Figure 2 n

Claims (1)

[Claims] (1) A crushed stone replacement method in which crushed stone (including gravel or slag) is piled up on the surface of unstable soft soil, and water flow is used to replace the soft soil and crushed stone to form a stable ground.