JPS58150615A - Vertical drain material - Google Patents

Abstract

PURPOSE:To obtain new water absorbing and discharging actions by breaking kraft papers when soft ground is dewatered and settled by placing a drain material formed by covering whole length of the periphery of a conventional vertical drain material with a kraft paper cylinder into the soft ground. CONSTITUTION:The periphery of a belt-shaped water conveyance plate 2 having vertically continuous grooves 1 is covered with a water-proof synthetic resin thin nonwoven fabric of polyester, polypropylene, etc., to form a vertical drain material similar to the conventional ones, and then the whole length of the vertical drain material is further covered with a kraft paper cylinder 4 to form a vertical drain material A. The preferred sizes of the vertical drain material are 5-10m/m in thickness, 10cm in width, and 30-100m in length. By this, when the vertical drain material A is placed in soft ground, large amounts of soil are adhered to the kraft paper, the kraft paper is broken as dewatering proceeds, and thereby new water absorbing and discharging actions by the drain material are performed.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a long-effective particulate drain material used for deep improvement of soft ground.

Currently, the bank drain method, developed by Chiyoda Corporation, is most commonly used for deep soil improvement. Synthetic resin threads are woven into a mesh to form a tubular bag, and this bag is driven into soft ground. In this method, sand piles are formed in soft ground by filling them with high-quality sand and protecting them with mesh-like bags. Although the construction technology for this method has been established and its effectiveness has been demonstrated, recently high-quality sand has become difficult to obtain and expensive. For this reason, chemical materials that are of stable quality and can be stably obtained at low prices are expected.

A variety of chemical products have been developed and used, but a common defect in these particulate drain materials is that in experiments using fresh water, they have very good absorption and drainage capabilities. However, when actually used on soft ground, its suction and drainage capacity is not fully demonstrated, and the capacity decreases particularly over a short period of time. The reason for this is that chemical product particle drainage materials are all wrapped in non-woven fabric or surface materials with micron-sized pores, and water is absorbed from this surface.・It is known that colloidal soil particles adhere to the surface of the drain material and cause clogging.

Another reason is that when pouring drain material, it is good to protect the surrounding area with a casing, but in most cases, the tip is pulled while the material is being poured, so the surface of the drain material rubs against the ground, causing fine soil particles to become visible. It is assumed that this is due to blockage.

The inventor conducted an experiment to explore such an entity. A nonwoven fabric approximately 3io+ thick was inserted into water containing many fine soil particles, and water was absorbed and drained using the siphon phenomenon. As time passed, the amount of absorbed water decreased and when it reached almost O, the nonwoven fabric was taken out and mud several inches thick had adhered to the periphery of the nonwoven fabric. Only the mud on the surface was removed and water was immersed in muddy water again for treatment and drainage. This clearly indicates that the decrease in water absorption and drainage is due to the layer of mud adhering to the surface of the nonwoven fabric, rather than clogging of the water pipe inside the nonwoven fabric.

Next, we conducted a comparison experiment on the suction capacity using a nonwoven fabric approximately 3 m thick and a nonwoven fabric approximately 108 thick in the same width, and found that there was no noticeable difference in the total displacement until the suction capacity reached O. I couldn't. From this, it was also inferred that the amount of water absorbed depends more on the surface area than the thickness of the nonwoven fabric.

Some foreign-made particulate drainage materials use kraft paper instead of non-woven fabric as the surface material, but in Japan, this material is used because the surface material tears during use and does not allow sufficient absorption and drainage. It has not been. Following the above experiment, the inventor conducted the following experiment. That is, we wrapped the nonwoven fabric in kraft paper and, as in the previous experiment, inserted it into muddy water to test the suction and drainage. The amount of water absorbed reached O in approximately the same time as in the previous experiment. Mud was attached to the surface of the kraft paper, just like the nonwoven fabric, but when the kraft paper was removed, almost no mud was attached to the surface of the nonwoven fabric. When the kraft paper was removed and the nonwoven fabric was reinserted into muddy water, there was a lot of absorption and drainage.

Based on such experiments, the present invention aims to provide a particulate drainage material with a long absorption and drainage effect.

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

[Example 1]

As shown in Figure 1, a thin non-woven fabric made of durable and water-resistant synthetic fibers such as polyester and polypropylene (
3) to form a conventional particulate drain material, and further cover the entire length with a cylinder of kraft paper (4) to form a particulate drain material.

The size of the drain material is usually 5 to 1030 mm thick and 1 mm wide.
A long one with a diameter of 0 cM1 and a length of about 30 to 100 m is common.

[Example 2] As shown in Figure 2, a 5-10 m thick fabric made of durable and water-resistant synthetic fibers such as polyester and polybutylene
A long nonwoven fabric (3) with a width of 20 cIR is folded in a zigzag pattern to form a width of about lOcrI1, and the top is covered over the entire length with a cylinder of craft paper (4) to form a particulate drain material.

Since the party force drain material of the present invention is constructed in this way, even if it is poured into soft ground without being protected by a casing, the outer kraft paper will rub against the soft ground.
Internal particulate drain material is not protected. As the water is absorbed, a large amount of mud adheres to the surface of the kraft paper, as seen in the experiment. At this stage, the kraft paper does not have much water resistance, so it becomes weak and easily torn.

Soft ground settles as dewatering progresses. For example, if there is 2m of ground subsidence due to 10m of deep improvement, various forces such as tension, bending, and friction will be applied to the party force drain material in the soft ground, and the outer kraft paper weakened by water will It ruptures and the internal party power drain is exposed and a new intake and water flow begins.

In particular, as seen in Example 2, if a wide non-woven fabric is folded and sealed, the size is about the same as conventional drain material when pouring, so conventional pouring machines can be used. Since it is thin, the total amount of nonwoven fabric used is the same as before, so the cost does not increase significantly. On the other hand, the effect is that as the soft ground settles, it is rubbed in the soil and the surrounding kraft paper is torn, and the folded nonwoven fabric is at least partially unfolded, creating a new surface that comes into contact with the soil. For this reason, compared to conventional drain materials, it takes a longer time to cause clogging, and therefore the effectiveness of particulate drain materials is longer.

In addition, another experiment showed that if drain material is soaked in an aqueous solution of flocculant/surfactant that has a strong tendency to ionize and then poured into the ground, soil particles become less likely to adhere to the surface of the drain material due to the action of ions. It turned out that. If the drainage material of the present invention, the outside of which is covered with kraft paper, is used in conjunction with this method, even longer-term effects can be expected.

still. In the present invention, the outer skin was made of kraft paper, but although it is water resistant for a short period of time, its strength decreases significantly if it is in contact with water for days or weeks. The material is not limited to kraft paper. The conventional particulate drain material that is wrapped inside is not limited to the embodiments, and any form or material may be used as long as it is used alone as a particulate drain material.

In addition, in Example 2, the nonwoven fabric was folded in a zigzag pattern, but
The folding method may be simply folded in two.

In addition to improving soft ground, the present invention can also be applied to rope-shaped drain materials used for dewatering activated sludge.

[Brief explanation of drawings]

FIG. 1 and FIG. 2 are perspective views showing an embodiment. A...Party drain material 1...Groove, 2...Water guide plate, 3...Nonwoven fabric, 4...
・Craft paper.

Claims (1)

[Claims] (1) Pack drain ● Drain materials conventionally used as particulate drain materials, such as plastic drains, have water permeability such as kraft paper, but if they are in contact with water for a period of days to weeks, their strength deteriorates significantly. Particular drain material (2) whose outer periphery is covered with a material that degrades
Particular drain material #Ii made of non-woven fabric etc. After forming a wide material into a Φ width by folding it, the outer periphery is made of a material such as kraft paper, which is water permeable but whose strength decreases significantly if it is in contact with water for a period of days to weeks. A particulate drain material that covers the