JPH0629502B2 - Liquefaction prevention method for soft ground - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial field of application) The present invention requires a required number of drain piles made of gravel (crushed stone, gravel, slag, etc.) with good water permeability in soft ground, particularly sand ground that is easily liquefied. By burying it, when the pore water pressure of the sand ground rises during an earthquake, the moisture in the ground is sucked up and discharged to the ground through these drain piles, thereby losing the bearing capacity of the sand ground even during an earthquake. The present invention relates to a method for preventing liquefaction of soft ground in order to make it safe ground.

(Prior Art) In this type of construction method, water discharged to the ground through a drain pile is conventionally made to flow out of a predetermined site ground by a gravel mat laid on the ground surface. However, since this gravel mat is laid almost entirely on the ground of the site, a large amount of gravel was required for the formation of this mat, which was one of the factors that caused the construction cost to rise. .

Therefore, instead of such a gravel mat, a gravel is used to form a ridge-shaped overhanging part that connects the heads of the drain piles to each other, and this overhanging part allows water discharged to the ground to flow out of the site ground. Such a construction method is disclosed in JP-A-56-89619. With this ridge-shaped overhang, a small amount of gravel is required, and the construction cost can be reduced accordingly.

(Problems to be solved by the invention) Since the ridge-shaped overhanging portion as described above is formed by raising the gravel into a ridge-like shape, the overhanging portion easily collapses when the earth and sand are covered from above. Also, when it rains, the soil particles of the sand and sand enter the gravel gaps of the water permeable pit and become clogged, which impedes the water permeable function of the overhanging part and prevents effective drainage.
Furthermore, it takes a lot of time and labor to form such an overhanging portion, and there is a problem that the construction efficiency is very poor.

The present invention aims to provide a method capable of solving such a problem.

(Means for Solving the Problems) In order to achieve the above-mentioned object, the construction method of the present invention is to connect the heads of the drain pile 1 to each other by the drain pipe 2 and to connect the drain pipe 2 with a mesh body. 3 is attached, and water overflowing from the head of each drain pile 1 is drained from this drain pipe 2
It is characterized in that it is discharged to a predetermined place through.

(Example) An example of the method of the present invention will be described with reference to the drawings. As shown in Figs. 1 and 2, a drain composed of a gravel G such as crushed stone is formed on a soft sand ground W in a predetermined site A. Pile 1
Are buried at a predetermined interval from each other. Then, on the surface side of the sand ground W in which these drain piles 1 are buried, for example, as shown in FIG. 1, along with one row of drain piles arranged in the left-right direction, a groove (not shown) having an appropriate depth is formed. Moat,
The circular drain pipes 2 ... Are fitted into these concave grooves, and the open ends of the drain pipes 2 are attached to the drain piles 1.
The head portion of the drain pile 1 is connected to the head portion of the drain pile 1 by the drain pipe 2 while being applied to the head portion of the drain pile 1 from both sides in the diametrical direction.

At this time, each drain pipe 2 connected to the head of the drain pile 1
A mesh body 3 is attached to the open end (connection portion) of the drain pile 1 so that the gravel G of the drain pile 1 does not flow into the drain pipe 2 as shown in FIG. Further, as is apparent from FIG. 1, the drain pipes 2 and 2 at both ends are appropriately extended outside the predetermined site A.

In this way, when the heads of the drain piles 1 ... Are completely connected by the drain pipes 2 ...
The foundation W is covered with earth and sand or the like on the grounded W to which, for example, is piped.

According to the sand ground W improved by the above-described construction method, when the pore water pressure of the sand ground W increases during an earthquake, the moisture in the sand ground W is wicked to the ground side through each drain pile 1. Is drained and overflows from the head of each drain pile 1, and the overflowed water is received by each drain pipe 2 connected to the head of the drain pile 1 and goes out of the predetermined site A through this drain pipe 2. It is appropriately discharged, and thereby the liquefaction of the sand ground W is prevented.

In such a case, even if the base layer T is muddy due to rainfall or the like and the drain pipe 2 is immersed in muddy water, the muddy water does not directly enter the drain pipe 2, and therefore the drain pipe 2 is not drained. There is no possibility that the pipe 2 will be clogged and the drainage action will be hindered. Further, since the mesh body 3 is stretched at the connection portion of the drain pipe 2 connected to the head of each drain pile 1, the gravel G on the head of the drain pile 1 is placed in the drain pipe 2 by the water pressure of the overflow water. It does not flow in, thus preventing collapse of the drain pile 1 head. By the way, when the head of the drain pile 1 collapses, the earth and sand on the ground surface block the connection of the drain pipe 2,
The drainage pipe 2 enters into the drain pipe 2 through the connection portion and hinders the drainage function of the drain pipe 2.

As the drain pipe 2, in addition to metal pipes such as steel pipes, ready-made pipes made of synthetic resin may be cut to a required length and used, and the diameter of the drain pipe 2 can be arbitrarily selected. is there. In addition, the drain pile 1 is formed by inserting a rotary drive type casing in which a screw is screwed on the outer peripheral surface or a drive type casing by an exciter to a predetermined depth in the ground, and after filling the casing with gravel. ,
It can be formed by pulling out the casing while pressurizing the filled gravel.

In the embodiment shown in FIGS. 1 and 2, an example in which the drain pile is buried so that its head is almost located near the ground is shown, but as shown in FIG. 3, it is called the second floor or the third floor. In the case of the ground W'of the site of a building having such a basement, a recess 4 having a considerable depth is excavated from the ground, and therefore, in the drain pile 11 buried in such ground W '. The horizontal pipe portion 12a of the drain pipe 12 is embedded in the soil 5 formed by placing concrete or the like at the bottom of the recessed portion 4 and the horizontal pipe portion 12a is formed as shown in the drawings. It is advisable to connect it to the head of the drain pipe 12a, connect the vertical pipe portion 12b to the drain pipe 12a, and further connect another horizontal pipe portion 12c to the end portion of the horizontal pipe portion 12c to the ground. . According to this, the water sucked up through the drain piles 11 is transferred from the horizontal pipe portion 12a in the soil 5 to the vertical pipe portion 12a.
It is discharged to the ground outside the specified site via b and the horizontal pipe section 12c. Although not shown, the pipe portion 12a of the drain pipe 11
A mesh body as shown in FIG. 2 is attached to the connection portion with the head portion of the drain pile 11.

(Effect of the Invention) According to the method of the present invention, the heads of the drain piles are connected to each other by the drain pipes so that the water overflowing from the drain pipe heads can be discharged to a predetermined place through the drain pipes. However, unlike the conventional method, drainage gravel is not deposited on the entire upper surface side of the specified site ground where drain piles are buried, so material costs and work costs associated with the use of gravel are significantly reduced. can do.

In particular, the method of the present invention uses a drain pipe in place of the conventional overhanging portion formed by raising a drain material such as gravel into a ridge-like shape. Since the cut drain pipe can be connected to the head of the drain pile, the workability is far better than the work to form the overhanging part using the conventional drain material. Therefore, the construction period will be greatly shortened and the construction cost will be significantly reduced. be able to.

Further, according to the method of the present invention, even if soil or the like is deposited on the upper side of the drain pipe, there is no risk of collapsing like the conventional overhanging portion, and the soil or the like deposited on the drain pipe due to rainfall or the like becomes muddy soil. Even if it gets wet, it will not flow into the drain pipe such as sediment, and since the mesh body is attached to the connection part of the drain pipe to each drain pile head, the gravel of the drain pile head will be There is no risk of flowing into the drain pipe together with the overflowing water, so it is possible to prevent damage to the head of the drain pile and blockage inside the drain pipe, which allows the drainage function to be fully exerted and good drainage for a long period of time. be able to.

[Brief description of drawings]

1 is a plan view showing an embodiment of the present invention, FIG. 2 is an enlarged sectional view taken along line II-II of FIG. 1, and FIG. 3 is a longitudinal sectional view showing another embodiment. W, W '... Soft sand ground, G ... Gravel, 1, 11 ...
… Drain piles, 2, 12… Drain pipes, 3… Nets.

Claims (1)

[Claims] 1. A method for preventing liquefaction of soft ground, in which drain piles made of gravel such as gravel are buried in a required number of soft grounds, and moisture in the soft ground is sucked up and discharged through the drain piles to the ground. , The heads of the drain piles are connected to each other by a drain pipe, and a mesh is attached to the connection portion of the drain pipes, and the water overflowing from the drain pile heads is discharged to a predetermined place through the drain pipes. A method for preventing liquefaction of soft ground, which is characterized in that