JPH0820941A - Stabilization of water bearing soft ground - Google Patents

Abstract

PURPOSE:To provide soft ground stabilization in which the pore water in a water bearing soft ground is forcibly sgueezed out and an effective area per pipe with holes is large and the start of construction work can be accelerated and the construction period and cost are greatly reduced and the pipes with holes are not damaged with the ground subsidence and unnecessary residual settlement is minimized and the buoyant force of the soft ground is eliminated and the self-weight is converted to the consolidation load and hence, a loading fill can be reduced. CONSTITUTION:A number of pipes 1 with holes are vertically inserted in the ground A and cylindrical submerged pumps 2 provided with an automatic switch 3 are installed in respective pipes 1 with holes. The pore water in the ground A collected in the pipes with holes is pumped up to the ground level. When the water level in the pipe 1 with holes reaches a specified level, the automatic switch 3 is turned on and the submerged pump 2 is actuated to discharge the pore water to the outside periodically.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for improving water-containing soft ground by collecting water contained in water-containing soft ground (hereinafter referred to as pore water) and forcibly discharging it with an underwater pump.

[0002]

2. Description of the Related Art Conventionally, paper has been used as a method for constructing water-containing soft ground.
There are drain method, sand pile method, pack drain method, etc. As shown in FIG. 6, this paper drain construction method uses a sand mat on a soft ground (A) and uses a fibrous material and has a long cross section with a width of 15 to 20 cm and a thickness of about 2 cm. Form a different paper member and drive it into the ground (A) from the ground at 1.5m intervals. Then, the paper member is a construction method in which the pore water around the periphery of the paper member permeates and the pore water is discharged to the ground by the action of the capillary action, and the pore water permeates into the sand mat to evaporate.

FIG. 7 is a diagram showing a sand pile method.
This is the same as the paper drain method, in which a sand mat is loaded on the soft ground (A) and sand is used to make a diameter of about 30.
Form a cm sand pile. The sand piles are driven at 5 m intervals and from the ground to a predetermined depth. Then, the pore water around the sand pile penetrates into the sand pile, and due to the action of the capillary phenomenon, it is a construction method in which the pore water is transmitted through the sand pile to the ground or the pore water permeates the sand mat to evaporate. This method can make the capillary phenomenon efficient by paying attention to the particle size of the sand used. Fig. 8 is a diagram showing the pack drain construction method, which has a similar principle to the paper drain construction method. Sand bags are used for the sand piles, and the sand is about 12.5 cm in diameter. Drive piles at 1.5m intervals and from the ground to a specified depth. Then, the surrounding pore water permeates into the sand pile, and the water is drained to the ground through the sand pile by the action of the capillary action or the pore water permeates into the sand mat to evaporate.

[0004]

However, in the case of the above-mentioned paper drain construction method, only a simple permeation action is utilized, and the paper member absorbs pore water in a narrow range, and The effect was not improved unless the number of paper members was increased. Further, since the action of the capillary phenomenon serves as a substantial drainage power, the drainage capacity was extremely low. Next, in the case of the sand pile method, the efficiency of the capillarity can be made slightly better than that of the paper drain method, but the effect is narrow due to simple penetration, and the capillarity is driven by the power. Therefore, the drainage capacity is low. In addition, since the discharged pore water contains a large amount of organic substances,
The sand used is easily clogged and drainage capacity is quickly reduced. Moreover, since it was only sand piles, it was extremely weak against shearing force. For this reason, there is a pack drain construction method in which the shearing force of the sand pile is strengthened, but this construction method is the same as the sand pile construction method except that a sand bag is used for the sand pile. Although the efficiency of can be improved to some extent, there is a problem that the drainage capacity is extremely low because the capillary phenomenon is used as the power.

Further, in the conventional auxiliary construction method which requires a sand mat or the like, the ground is lowered along with the drainage, and the capillarity members such as paper members and sand piles are damaged due to the ground subsidence, and the drainage capacity is reduced. It was easy to drop. Further, since the paper members, sand piles, and sand bags remain in the ground, residual subsidence occurs, and the embankment work cannot be performed unless the effect of the sand mat is reduced. As a result, the start of construction work was delayed, making it difficult to start work early.

The present invention eliminates the damage of perforated pipes due to ground subsidence and forcibly squeezes out pore water, so that the dehydration effect is promoted, and the consolidation effect due to the decrease in water content can be achieved earlier than the conventional method, and It is an object of the present invention to provide an improved construction method for water-containing soft ground that can be significantly shortened and can reduce the construction unit price.

[0007]

The present invention has been made to solve the above problems. That is, a large number of perforated pipes are vertically inserted into the ground, and the bottoms of the perforated pipes are provided. A method is provided in which a cylindrical submersible pump having an automatic switch is installed, and the submersible water in the ground collected in the perforated pipe is discharged to the ground by the submersible pump. Further, when the water level in the perforated pipe reaches a certain level, an automatic switch is turned on and the submersible pump is operated to periodically discharge pore water to the outside.

[0008]

Next, the operation of the present invention will be described. First of all,
As shown in Fig. 5, a water-containing soft ground (A) has a large number of perforated pipes (1) vertically inserted, and a cylinder having an automatic switch (3) at the bottom of each perforated pipe (1). The submersible pump (2) is also installed. In addition, the drainage channel (5) is provided at a position slightly higher than the groundwater level. At this time, the ground (A)
Inside, as shown in Fig. 2 (a), dead load acts downward as indicated by the solid arrow in the figure, and buoyancy acts upward as indicated by the dashed arrow in the figure. ing. When time passes in this state, the water collection hole (11) of the perforated pipe (1)
Pore water gathers and collects inside. When the water level in the perforated pipe (1) reaches a certain level, the automatic switch (3) is turned on and the submersible pump (2) is activated to suck up pore water to the upper part and to the ground drain (5). It is drained and begins to flow out. The submersible pump (2) operates for a certain period of time and then stops. Further, when the water in the ground (A) is collected as pore water in the water collection hole (11) and the water level in the perforated pipe (1) reaches a certain level, the automatic switch (3) is turned on and the submersible pump (2). Activates to discharge pore water to the ground. In this way, the water level of the pore water accumulated in the perforated pipe (1) is periodically changed by turning on and off the automatic switch (3), which causes a phenomenon that the water vibrates in the ground (A). The pore water is squeezed out, and the effect of compacting the water-containing soft ground (A) is produced. As a result, the pore water is drained and a large amount of water in the ground (A) is drained and dehydrated by the submersible pump (2), so that the groundwater level drops in a short time and reaches the state of FIG. 2 (b). . At this time, the ground (A) discharges a large amount of water by the submersible pump (2), so that the initial consolidation is promoted and the dead load on the soft ground (A) is increased due to the overall decrease in the groundwater level over the entire construction area. Since the water content is increased and the pore water is forcibly squeezed out, the dehydration effect is promoted, the consolidation effect due to the decrease in the water content can be achieved earlier than the conventional method, and the construction period can be greatly shortened.

In the method of the present invention, the soil particles in the upper part are moved by the water flow due to the periodic vertical movement of the groundwater level and are carried to the soft ground (A), so that the density of the soft ground (A) is increased. . In addition, because the submersible pump (2) forcibly discharges pore water without relying on the capillary phenomenon, there is no clogging due to water stains as in the past, and the water collection hole (1) of the perforated pipe (1)
By increasing the value of 1), it is possible to prevent the reduction of water collection capacity.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a diagram showing the construction method of the present invention, and based on this, the parts will be described first. (1) is a large number of perforated pipes vertically installed on the soft ground (A) at intervals of about 10 m, and the perforated pipes (1) are cylindrical with a bottom and a large number of them on the entire peripheral wall. The water collecting hole (11) is provided, and its shape is preferably circular as shown in FIG. 3A or grooved as shown in FIG. The perforated tube (1) is mainly a vinyl chloride tube having a diameter of 10 to 15 cm. The perforated water in the ground (A) is collected by the perforated pipe (1). (2) is a small cylindrical submersible pump installed near the bottom of the perforated pipe (1), and (3) is for operating the submersible pump (2) when pore water rises to a certain point. It is an automatic switch and uses a float switch. (4) is a check valve provided on the ground, and (5) is a drain.

Next, examples of the method of the present invention will be described. First, as shown in FIG. 2A, the dead load acts downward as indicated by the solid arrow in the figure, and the buoyancy acts upward as indicated by the dashed arrow in the figure. When time passes in this state, pore water collects and collects in the water collecting hole (11) of the perforated pipe (1). When the water level in the perforated pipe (1) reaches a certain position, the submersible pump (2) is automatically operated by the float switch (3), and the submersible water is sucked by the submersible pump (2). It is fried and drained from the drainage gutter (5) on the ground to start outflow. The submersible pump (2) operates for a certain period of time and then stops. In addition, to the water collection hole (11) Ground (A)
When the water content inside is collected as pore water and the water level in the perforated pipe (1) reaches a certain level, the float switch (3) is turned on,
The submersible pump (2) operates to discharge the pore water to the ground. The phenomenon that the pore water accumulated in the perforated pipe (1) is vibrated in the ground (A) by periodically changing the water level by turning the float switch (3) ON and OFF. Therefore, the pore water is squeezed out, and the effect of compacting the water-containing soft ground (A) is generated. As a result, the pore water is drained and the water in the ground (A) is removed by the submersible pump (2).
By draining a large amount of water and dehydrating it, the groundwater level drops in a short time and reaches the state shown in Fig. 2 (b). Then, when the target pressure density is reached, the submersible pump (2) is completely stopped. When the time required for the compaction density to reach 80% is compared between the method of the present invention and the method of the conventional method, the method of the present invention achieves about one-third the time of the conventional method. It was confirmed (see FIG. 4).

[0012]

The present invention having the above-mentioned constitution has the following effects.

A cylinder having a plurality of perforated pipes (1) vertically inserted into the ground (A) and having an automatic switch (3) at the bottom of each perforated pipe (1). A submersible pump (2) is installed, and a perforated pipe (1) is installed in the submersible pump (2).
By discharging a large amount of pore water in the ground (A) collected in the ground to the ground, the pore water is forcibly squeezed out and the effective area per one perforated pipe (1) increases, so Significantly shortened construction cost can be reduced. Furthermore,
System damage due to negative friction associated with consolidation settlement of the ground (A) is extremely reduced. In the method of the present invention, since the perforated pipe (1) is self-supporting, the perforated pipe (1) is erected from the beginning of the embankment work to discharge a large amount of groundwater and pore water in the ground (A) to the ground. You can In addition, since the perforated pipe (1) can be added to correspond with the progress of the embankment, consolidation can be promoted from the beginning of the embankment work, so the start of construction work on the ground (A) where consolidation has been completed is hastened. It becomes possible.

When the water level in the perforated pipe (1) reaches a certain level, the automatic switch (3) is turned on and the submersible pump (2) is operated to periodically discharge the pore water to the outside. By doing so, the periodic groundwater level moves up and down, the soil particles in the upper part move by the water flow, and are carried to the soft ground (A), so that the density of the soft ground (A) is increased. Further, due to the fluctuation of the groundwater level, the pore water in the ground (A) is squeezed out and has the effect of compacting. As a result, the groundwater level drops in a short time, and the target compaction density is reached in about one-third of the time required by the conventional method, and the construction period can be shortened. The method of the present invention uses the submersible pump (2) when the target compaction density is reached.
If the buoyancy acting on the remaining pressure density is positively utilized by stopping the progress of the consolidation by stopping the step, the load is reduced, and unnecessary residual settlement can be minimized. Further, since the buoyancy of the soft ground (A) is eliminated and the own weight is changed to the consolidation overweight, the embankment can be reduced.
Moreover, the hose from the submersible pump (2) can directly drain the water to the outside, and the auxiliary construction method such as sand mat is unnecessary, so that the construction method can be simplified.

[Brief description of drawings]

FIG. 1 is an explanatory view showing a working example of a water-containing soft ground according to the method of the present invention.

FIG. 2 is an explanatory view showing a changing water level state of the method of the present invention.

FIG. 3 is an explanatory view showing a perforated pipe used in an example of the method of the present invention.

FIG. 4 is a diagram comparing the conventional method with the method of the present invention showing the relationship between the amount of dehydration and time.

FIG. 5 is a diagram comparing the conventional method with the method of the present invention showing the relationship between compaction density and time.

FIG. 6 is an explanatory diagram showing an example of construction of a water-containing soft ground according to a conventional method.

FIG. 7 is an explanatory view showing a working example of a conventional water-containing soft ground.

FIG. 8 is an explanatory diagram showing an example of construction of a water-containing soft ground according to a conventional method.

[Explanation of symbols]

 A Ground 1 Perforated pipe 2 Submersible pump 3 Automatic switch

Claims (2)

[Claims] 1. A cylindrical submersible pump (2) having a large number of perforated pipes (1) vertically inserted into the ground (A) and having an automatic switch (3) at the bottom of each perforated pipe (1). Is installed and the submersible water in the ground (A) collected in the perforated pipe (1) is discharged to the ground by the submersible pump (2). 2. The automatic switch (3) is turned on when the water level in the perforated pipe (1) reaches a certain level, and the submersible pump (2) is activated to periodically discharge pore water to the outside. Item 1. A method for improving a water-containing soft ground according to Item 1.