JP2521597B2 - How to improve soft ground - Google Patents

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 soft ground such as cohesive ground and sandy ground containing pore water.

[0002]

2. Description of the Related Art A sand drain method has been widely used as a method for improving soft ground. This method is
As shown in FIG. 9, a large number of sand pillars B are vertically driven on the soft ground A to guide the groundwater (hereinafter referred to as pore water) contained in the soft ground between the particles of the sand pillar, The interstitial water is discharged to the side of the sand mat C laid on the ground through the interstices of the sand particles to reduce the interstitial water in the soft ground.

Further, as other soft ground improvement methods, there are a paper drain method and a plastic board drain method, and these methods are formed by a paper or a plastic material having a gap corresponding to the gap between the sand particles of the sand pillar. It is a method of driving ponds into the ground to reduce pore water.

In any of the above methods, in order to discharge the pore water in the soft ground to the surface of the earth through the drain material having a large number of pores such as sand particles and paper, the pore water pressure must be increased. It is necessary to place a large amount of loading embankment D such as earth and sand on the soft ground.

[0005] Then, the pore water pressure in the soft ground is increased by the loading of such earth and sand, and the pore water is permeated into the gap of the drain material and discharged to the surface side as described above. Is performed because the pore water pressure in the soft ground due to the applied load is higher than the pore water pressure (natural head) that permeates into the gap of the drain material. Must be increased.

Therefore, the embankment reaching a height of 5 to 10 m is usually carried out. However, when the necessary amount of embankment is applied all at once, the soft ground causes lateral flow and slip due to its large load, and its movement. Since there is a risk that the drain material will be cut at the middle part and a discontinuous portion will be generated, it is necessary to carry out loading embankment in stages to gradually settle the soft ground.

[0007]

Therefore, after the soil improvement strength is obtained by consolidation according to the load embankment, the next stage of embankment is performed and the settlement is performed again, and this work must be repeated. Not only becomes complicated, but also requires a long construction period, and considering the fact that the construction and removal of loaded embankments account for the majority of the total construction cost, increasing the embankment volume is both workability and economic efficiency. There was also a problem in terms of.

Further, since the pore water in the soft ground is constantly pumped through the drain material, the soil particles in the soft ground fluctuate in such a direction that they are always compressed as the pore water decreases. Since the shapes are various, there is a problem that the particles are aggregated in an irregular state in which gaps are formed and the consolidation enhancement of soft ground is reduced.

The present invention has been made in view of the above problems, and a large number of water passage holes are provided on the contact surface with the soft ground.
The drain material that has the perforated pipe body formed by repeatedly performing the draining action and the water supplying action on the soft ground to relatively move the soil particles and the soil particles, thereby collecting the particles in a compacted state to form a drain material. Around its entire length
The present invention provides a ground improvement method for enhancing the consolidation of soft ground in the surrounding area .

[0010]

In order to achieve the above object, the ground improvement method of the present invention comprises a non-perforated pipe body and a ground
A perforated pipe body having a large number of water passage holes on its contact surface.
And the lower ends of both pipes
A drain material which is made to communicate with each other is vertically driven to a desired depth in soft ground , and then a perforated pipe body of the drain material is formed.
Pore water in the soft ground that flows into the inside through the water passage small holes is drained onto the opening of the non-perforated pipe body or the perforated pipe body.
The step of pumping and removing by drainage means connected to and connected to the end , and the non-perforated pipe body or perforated pipe body of the drain material
Drain material through the water supply means that is connected to the upper end of the opening
And is characterized in Rukoto to promote settlement of the soft ground by repeating the step of supplying water to the perforated pipe soft in soil from a number of water passing pores of the.

[0011]

[Function] Perforated pipe of drain material placed in soft ground
When the pore water in the soft ground that flows into the perforated pipe body from a large number of water passage holes provided in the body is forcibly pumped up by a suction pump or the like, the inside of the drain material becomes atmospheric pressure. So
Then, along with the entire length of the drain material, the water pressure of the pore water existing between particles (hereinafter referred to as soil particles) such as soil particles and sand particles in the soft ground around the drain material is relatively increased ,
From the soft ground side through a large number of perforated pipe holes
Pore water flows into the drain material. At this time, the soil particles in the ground move in a direction of increasing the density of each other, and the consolidation of the ground is enhanced. In addition, as the drainage means in the perforated pipe body,
It is not a suction means like
It may be.

Next, water is poured into the drain material to make a perforated pipe body.
When water is supplied to the soft ground through a large number of water passage holes in
The direction that water is given buoyancy and diffuses each other
The soil particles of various sizes change their direction.
The orientation and arrangement of soil particles change.

Then, again, the perforated pie of the drain material is used.
When the water flowing in and staying in the pipe body is pumped, the pore water in the soft ground flows into the perforated pipe body of the drain material,
The soil particles in the ground move in a direction of increasing the density, and at that time, the soil particles are in a tightly packed state in which the soil particles are more closely packed with each other, and the consolidation of the ground is enhanced. In this way, by repeatedly supplying and draining water to the soft ground through the drain material, the consolidation settlement of the soft ground around the drain material is enhanced, and the soil is improved in a short period of time without a large amount of embankment. Is what makes it possible.

[0014]

FIG. 1 shows a drain material used for improving soft ground. The drain material 22 is made of a flexible synthetic resin material, a thin steel plate, or a thick cloth, and has a thickness of 3 It has a length of about 6 mm, a width of 70 to 100 mm, and a long length, and is formed into a flat flexible tubular body having a hollow crosswise hollow rectangular shape with a horizontal cross section of about 100 m. As shown in FIG. 2, the internal structure of the drain member 22 is divided into a plurality of pipe bodies by dividing it in the width direction by vertical partition plates 23, 23, ... is there. The pipe bodies 25, 25 other than the central pipe body 24 are provided with a large number of slit-like water passage small holes 26 at appropriate intervals in the longitudinal direction on the front and rear side wall surfaces of the drain member 22 forming the pipe bodies 25. , 26 ... 26 are bored to form a perforated pipe body,
The central pipe body 24 is a non-perforated pipe body.

Further, a filter 27 made of a non-woven fabric or the like is attached to the front and rear outer wall surfaces of the drain material 22, and a cap body 28 is attached to the lower end of the opening of the drain material 22 by an appropriate means such as a screw. This cap body 2
The reference numeral 8 is formed in an inverted triangular shape in cross section, and as shown in FIG. 3 , the front and rear end portions of the upper end surface thereof are horizontally projected outward from both side walls of the drain member 22. At the lower end of the opening of the drain member 22 closed by the upper end surface of the cap body 28, the lower ends of the central non-perforated pipe body 24 and the perforated pipe body 25 communicate with each other through a passage 29 as shown in FIG. I am doing it.

The drain material 22 having the above-described structure is cast on the soft ground 1. As the driving method, for example, as shown in FIG. 5, the long drain material 22 is arranged in a wound state on the driving carriage 30 and the leads 31 vertically supported on the tip end of the carriage 30. The draining material 22 is attached with the driving and clamping member 32 so that it can be raised and lowered.
2. Pull out the appropriate length part of 2 and sheave 33 on the upper end of the lead.
A cap body 28 that is sandwiched by a sandwiching member 32 via a pin, and the lower end of the sandwiching member 32 projects from the lower end of the drain member 22.
The outer peripheral surface of the upper end is contacted.

In this state, the holding member 32 is lowered along the lead 31 and driven into the desired depth of the soft ground 1.
Then, when the holding force of the holding member 32 is released and pulled up,
The drain member 22 is prevented from rising together by the cap body 28 attached to the lower end of the drain member 22 and maintains the state of being vertically driven in the soft ground 1, and only the holding member 32 is pulled up. Then, the drain member 22 is cut at the lower end side of the holding member 32.

At the time of driving the next drain material 22, the drain material 22 is pulled out through the sheave 33 according to the driving of the drain material 22 having the predetermined length, so that the lower end of the opening cut as described above. After mounting the cap body 28 on the ground, it is placed on the soft ground 1 in the same manner as described above. By repeating this placing work, as shown in FIG. 6, a large number of drain members 22 are placed at desired intervals in the plane direction of the soft ground 1.

Then, as shown in FIG. 7, the drain material 22 is sent to the open upper end of the non-perforated pipe body 24 of the drain material 22 and is connected to the drain pipe 34, and these drain pipes 3 are connected.
4 is connected to and communicates with a suction device 11 such as a vacuum pump installed at an appropriate place on the ground and a water supply pump 12 via suction pipes 15 and water supply pipes 16 provided with valves 13 and 14, respectively.
The perforated pipe body 2 by alternately switching the valves 13 and 14
The drainage and the water supply are alternately repeated for 5 to improve the soft ground 1.

Drainage of pore water through the drain material 22,
The water supply method for the soft ground 1 is performed as follows. That is, when the drain material 22 is cast into the soft ground 1, the pore water in the ground passes through the filter 27 and flows into the perforated pipe body 25 through the large number of water passage small holes 26, and the drain material 22 Stays in the lower part of the. When this accumulated water is discharged to the ground side through the non-perforated pipe body 24 by the operation of the suction device 11, the water head pressure in the drain material 22 decreases and the drain material 2 from the soft ground 1 side through the perforated pipe body 25.
Pore water positively flows into the inside of 2, and the groundwater level lowers, and it moves in the direction where soil particles in the ground gather, and the ground consolidates.

Next, after the clearance water is removed for an appropriate period of time, the suction device 11 is stopped while the water supply pump 12 is operated to pass through the non-perforated pipe body 24 to the drain material 22 in the soft ground. If water is injected until the head pressure is higher than the groundwater pressure of the
Water is supplied so that water permeates through the soil particles of the soft ground 1 through 7. Due to this water supply, the soil particles in the soft ground are given a buoyancy force and the relative displacement between the particles occurs, and the arrangement state between the particles changes.

After the water supply for a desired time, the water supply pump 12 is stopped, the suction device 11 is activated again, and the pore water penetrating between the soil particles of the soft ground 1 is made to flow into the drain material 22. , The aggregate particles move in the direction of becoming closer to each other due to the elimination of pore water, and at the time of the aggregate, the orientation and arrangement state of the particles are changed so that another soil particle is closely intervened in the gap between the soil particles, and the soil particles are changed. The space changes to a state in which they are tightly pressed together, and the state of consolidation of the ground is promoted more than in the previous step of removing the accumulated water.

Next, water is supplied to the soft ground 1 again, and
Similarly, by repeatedly performing the water supply process and the drainage process, consolidation settlement of the soft ground is promoted in stages.
Such improvement of the ground can also be performed with one drain material.

Also, as shown in FIG.
For example, 2 is divided into a plurality of row groups for each row, drainage is performed to the adjacent drain material group A, and the other drain material group A is drained.
The step of supplying water to the drain material group A and the step of supplying water to one drain material group A and draining the other drain material group A after repeating this step for a predetermined time are repeated. Good. Further, in this case, the drain material may be cast in at least two places on the soft ground 1, and the above steps may be repeated for one drain material and the other drain material.

In order to remove the interstitial water from the drain material 22, the perforated pipe body 25 may be pumped through the perforated pipe body 25 by applying the suction force of the suction device 11. In this case, the non-perforated pipe body 24 serves to send the outside air into the drain material 22 according to its suction force. Instead of the suction device 11, the non-perforated pipe body 25 of each drain material 22
A pressure means (not shown) such as a compressor is connected to the upper end of the opening of the drainage pipe through an air supply pipe, and this pressure means removes the interstitial water entering and staying in the drain member 22 through the perforated pipe body 25. In short, in short, the drain material 22 may be used to remove pore water and supply water to the soft ground 1.

Further, in the above embodiments, it is not necessary to load a large amount of embankment as in the conventional case, but since the ground is consolidated and settled by the removal of pore water, the height corresponding to the settling amount is set. The embankment 35 may be applied.

[0027]

As described above, according to the method for improving soft ground of the present invention , a large number of contact surfaces between the non-perforated pipe body and the ground are provided.
Assembled integrally with a perforated pipe body with small water passage holes
And make sure that the lower ends of both pipes communicate with each other.
The drain material is placed vertically to the desired depth in soft ground.
After that, in the pipe body with the drain material, the above-mentioned water passage small hole
No drain material the pore water of the soft in the ground which flows through
Connects and communicates with the upper end of the opening of a perforated pipe or perforated pipe
The step of pumping and removing by drainage means , and connecting to the open upper end of the non-perforated pipe body or perforated pipe body of the drain material ,
Drained perforated pipe body
Since it is characterized by repeating the process of supplying water to the soft ground from a large number of water passage holes , it contacts the soft ground
The perforated pipe body through a large number of water-permeable small holes of the perforated pipe body
Smooth pore water in the soft ground around the inside of the perforated pipe body
Inflow can reduce the groundwater level and
Connects and communicates with the upper end of the opening of a perforated pipe or perforated pipe
Since the water is forcibly pumped up by the drainage means , a perforated pipe
Pore water that has flowed into and accumulated in the body can be removed by suction
Not only the inside of the drain material is at atmospheric pressure to the lower end
It is possible to do so over the entire length of the drain material.
Relative increase of water pressure of pore water around soft ground
It is possible to remove pore water existing between soil particles in soft ground.
Through a large number of water passage holes in the perforated pipe body
It is possible to positively inflow into the ground and positively improve the consolidation of the ground.

Further, after draining the pore water, water is poured into the drain material to supply water to the soft ground through a large number of water passage holes of the perforated pipe body, so that soil particles having various shapes of large and small have buoyancy by the water supply. It is possible to change the orientation and arrangement state of these soil particles at the time of consolidating given that they move in the direction of diffusing with each other, and after this state, again flow into the perforated pipe body of the drain material, stay Since the accumulated water is pumped up and removed, the interstitial water between the soil particles flows into the perforated pipe body of the drain material again, and flows and is compressed in the direction in which the soil particles gather together. Aligning and arranging so that other soil particles are closely intervened in the gap of
It is possible to further enhance the consolidation of the ground around the perforated pipe body over the entire length of the pipe body .

The repetition of such pore water elimination process and water supply process for soft ground is as if the hydrated sand lump was gripped and the grip force was applied to the sand lump, and then the grip force was released to grip the sand lump. By repeating the action of changing the state and then applying the grip force again, it is equivalent to the action of raising the contained water to solidify the sand lump in a compressed state, rather than constantly applying the grip force. , It is possible to enhance the drainage by changing the orientation state of the sand particles, therefore, according to the soil improvement method of the present invention, by the repeated water supply and drainage action to the soft ground through the drain material, soft It is possible to improve the ground efficiently in a short period by positively increasing the consolidation settlement of the ground.

[Brief description of drawings]

FIG. 1 is a partially cutaway front view of a drain material,

FIG. 2 is a cross sectional view thereof,

FIG. 3 is a vertical sectional side view of a cap body portion,

FIG. 4 is a sectional view showing a pumped state,

FIG. 5 is a simplified side view of the drain material placing device,

FIG. 6 is a plan view of a drain material placed in soft ground,

FIG. 7 is a simplified vertical sectional view showing a ground improvement state,

FIG. 8 is a simplified plan view showing a state of being divided into a plurality of drain groups.

FIG. 9 is a simplified vertical sectional view showing a conventional example.

[Explanation of symbols]

 1 Soft ground 22 Drain material 24 Non-perforated pipe body 25 Perforated pipe body 27 Filter 34 Transmission and drainage pipe

Claims (1)

(57) [Claims] 1. A large number of non-perforated pipe bodies and the contact surface with the ground
Assembled integrally with the perforated pipe body with the small water passage
And make sure that the lower ends of both pipes communicate with each other.
Da設vertically to drain material made to the desired depth of soft in the ground
After that, the small amount of water passing through the perforated pipe body of the drain material.
The interstitial water of soft in the ground which flows through the pores of the drain member
Connects and communicates with the open upper end of non-perforated pipes or perforated pipes
The process of pumping and removing by the drainage means connected to the drain material and the upper end of the opening of the non-perforated pipe body or the perforated pipe body of the drain material.
A perforated pipe made of drain material through a connecting and communicating water supply means
Improved method of soft ground characterized by Rukoto to promote settlement of the soft ground by repeating the step of supplying water from a large number of water passing pores of the body to the soft in soil.