JPH0470410A - Consolidation method for weak ground - Google Patents

Abstract

PURPOSE:To facilitate ground improvement by forming a circular hole in the middle between multiple drain pillars, and pressing a viscous material into it to consolidate the weak ground, and moving gap water located in the ground to the drain pillars, through which water is drained to the surface of the ground. CONSTITUTION:A circular cylinder 5 is struck in between multiple drain pillars 4, 4... into the weak ground 1 to the depth of a drain pillar 4 through a sand mat 2 to form a circular hole 7. While the circular cylinder 5 is being drawn up gradually, the circular hole 7 is filled with a viscous material 8 which is a unit volume weight of the weak ground. A pressure feed pump 12 installed at a pressure feed pipe 11 is operated and the viscous material 8 is pressed in, so that the weak ground 1 is consolidated and gap water in the ground is moved to the surrounding drain pillar 4, through which gap water is drained to the surface of the ground. It is thus possible to ensure consolidation of the ground in the horizontal direction.

Description

[Detailed Description of the Invention] (Industrial Application Field) The present invention is used in a consolidation dewatering method for improving soft ground such as soft and sticky soil containing pore water. The present invention relates to a method for consolidating soft ground that can replace surface-loaded embankments or reduce the loading amount of the loaded embankments.

(Prior art) Conventionally, in order to improve soft and viscous soil with high moisture content and high fluidity, a large number of vertical drain columns are installed at appropriate intervals in the soft ground using the sand drain method or pack drain method. In addition to shortening the horizontal consolidation drainage distance in the ground, loading embankments are applied to the soft ground surface and the vertical load increases the pore water pressure in the ground. The so-called consolidation dewatering method is used, which promotes consolidation of the ground by draining water.

In addition, while this vertical ground consolidation method using loaded embankment is adopted, a bag made of an elastic material such as rubber is placed in the soft ground, and liquid is injected into the bag to fill it. A construction method has also been developed in which a bag is inflated using hydraulic pressure and the expansion pressure is used to press soft ground horizontally.

(Problem to be Solved by the Invention) However, according to the method of consolidating soft ground by the weight of loaded embankment, the pore water pressure in the ground is determined by the absolute amount of loaded embankment, so the gap drained through the drain column is The amount of water will also be affected by the amount of loaded embankment.

At this time, if the amount of embankment required to obtain the ground improvement strength of the initial plan is constructed all at once, the large load on the soft ground will cause lateral flow and slippage, and this movement will cause the drain pillar to be cut in the middle. As discontinuities occur and consolidation dewatering becomes impossible, it is necessary to carry out loading embankment in stages to gradually consolidate the soft ground.

Therefore, after achieving the ground improvement strength by consolidation according to the loaded embankment, the next stage of embankment is carried out and consolidation settlement is carried out again, and this work has to be repeated, which not only complicates construction management but also causes unavoidable In view of the current situation, in which the construction period is generally long and the construction of loaded embankments accounts for the majority of the total construction cost, increasing the amount of embankment poses problems in terms of construction efficiency and economy.

On the other hand, the latter method, that is, placing the bag in soft ground,
Some of the above problems can be solved by a method of pressing the soft ground horizontally through the cough bag using the liquid pressure generated by injecting and filling the cough bag with liquid. The unit weight of the liquid injected into the bag is smaller than that of the soft ground, so when the liquid pressure is increased, the soft ground in the upper layer is relatively more pressurized than the soft ground in the lower layer. There is uneven horizontal consolidation of soft ground, and since the bag body is made of an elastic material such as rubber, the liquid pressure concentrates on the weak part of the ground, causing only that bag part to expand, causing damage to other ground. There was a problem in that there were cases in which the consolidation of parts was hardly performed.

The present invention provides a method for consolidating soft ground with the aim of solving these problems.

(Means for Solving the Problems) In order to achieve the above object, the consolidation method for soft ground described in claim A viscous substance whose unit volume weight is approximately equal to the unit volume weight of the soft ground is supplied to the cylindrical body, and while the cylindrical body is pulled out, a columnar body of the viscous substance is formed in the soft ground in which the cylindrical body was placed. It is characterized by applying pressure to consolidate soft ground in the horizontal direction.

In addition, another soft ground consolidation method of the present invention, which is different from the above-mentioned soft ground consolidation method, is as described in claim (2),
A cylindrical body containing a long bag made of non-stretchable flexible fabric in a radially contracted state is driven into soft ground to a predetermined depth, and then the bag is placed into the soft ground. Supply and fill the liquid into the bag while the bag is left in place, and then pull out the cylindrical body, or supply and fill the liquid into the bag while pulling out the cylindrical body, and pressurize the liquid inside the bag after pulling out the cylinder. This is characterized in that the soft ground is consolidated in the horizontal direction through the bag body that is in contact with the soft ground.

(Function) According to the soft ground consolidation method described in claim (■) above,
When a cylindrical body poured into soft ground is pulled up, the viscous substance poured into the cylindrical body comes into direct contact with the soft ground, but forms a thin film on the hole wall without penetrating into the soft ground. .

Furthermore, since the unit volume weight of the viscous substance is approximately equal to that of the soft ground, the surface in contact with the ground is pressed with a predetermined pressure in balance with the soil on the soft ground side.

When the viscous material is pressurized in this state, the soft ground receives a pressing force in the horizontal direction through the viscous material, and is consolidated.

Consolidation of this soft ground can be adjusted by controlling the pressure applied to the viscous material, and as the viscous material expands in the radial direction as the consolidation of the soft ground progresses, it is necessary to replenish the amount of viscous material that corresponds to the spread. This is to promote consolidation of the ground by applying pressure.

Next, according to the consolidation method for soft ground described in claim (2) above, since the bag housed in the cylindrical body and cast into the soft ground contracts in the radial direction, the cylindrical body When the bag is pulled out and liquid is forced into the bag and filled, the bag expands to a diameter much larger than the diameter of the cylindrical body, increasing the pressing force against the soft ground and exhibiting a good ground consolidation effect. It is.

Furthermore, since the bag body is made of non-stretchable, flexible fabric, there is no tremor caused by partial expansion depending on the ground conditions, unlike with rubber bags, and there is no tremor caused by the liquid being press-fitted and filled into the bag body. It is possible to apply pressure evenly over the entire surface to generate uniform expansion pressure to a constant diameter over the entire length, and the pressure adjustment can be easily and accurately controlled by a liquid pressure pump, and it is possible to It is also possible to detect compacted coal, allowing for precise construction management.

By attaching a floating resistance plate to the bottom of the bag in advance, it is possible to prevent the cylindrical body from lifting up when being pulled out.

(Example) To explain the embodiment of the present invention with reference to the drawings, in Fig. By constructing the loaded embankment (3), as is known,
Consolidation is performed in the vertical direction according to the weight of the embankment (3), and the pore water pressure in the ground is increased by the consolidation, and a large number of pore water pipes are formed at appropriate intervals in the soft ground. Vertical drain pillar (sand pile (4) (4) -...
4) to drain water to the ground.

As shown in FIGS. 2 and 3, a cylindrical body (5) is installed between the adjacent drain columns (4) (4) constructed by such a conventional construction method. The cylindrical body is driven to the same depth using an appropriate driving device, and discharged to the ground while excavating the ground using an excavating means (6) such as an auger screw installed in the cylindrical body (5) according to the driving. (5) reaches a predetermined depth, the excavation means is pulled out and the cylindrical body (5) is gradually pulled up. A viscous substance (8) whose unit volume weight is approximately equal to the unit volume li of the soft ground is supplied from the viscous substance (8).

In addition, such viscous substances (8) include soft ground (
1) Highly concentrated bentonite mud that does not penetrate is used.

In this way, while pulling out the cylindrical body (5), the viscous substance (8) is injected and filled into the circular hole (7) formed in the hole through the piping (9) to form a columnar body of the viscous substance, and the viscous substance (5) and after removing the pipe (9), the lower end of the turning part 00 is tightly fitted into the upper end opening of each circular hole (6), and the turning part 0ω is made to protrude upward from the embankment (3). Its upper end opening is connected and communicated with the viscous substance pressure feeding pipe 00.

Viscous substance injected into the circular hole (7)! (8) forms a film on the wall surface in contact with the circular hole (7) without penetrating into the ground, and since the unit volume weight of the viscous substance (8) is approximately equal to that of the soft ground (1), it is suitable for soft ground. (1) Press the surface in contact with the ground with hydraulic head pressure in balance with the earth pressure on the side.

In this state, as shown in FIG. 1, when the slurry pump 0 installed in the pressure feed pipe (11) is operated, a viscous substance is filled from the circular hole (7) into the turning section αω! (8)! Furthermore, the viscous material is press-fitted into the circular hole (the viscous material (8) of 10,000 yen is subjected to compressive force, and the pressure acts horizontally on the soft ground (1) and consolidates the soft ground (1). , the pore water pressure in the ground is increased to forcibly move the pore water toward the surrounding drain pillar (4), and the water is drained to the ground through the drain pillar (4).

This horizontal consolidation is performed together with the vertical consolidation by the embankment (3), but by increasing the weight of the embankment (3), the vertical consolidation of the soft ground (1) is adjusted. (7) The pressure applied to the viscous substance (8) injected into the soil is controlled by the pressure management of the mud pump 021, and the horizontal consolidation of the soft soil m(1) is adjusted as it progresses.

At this time, the viscous substance (8) expands in the radial direction as the soft ground consolidates, and the viscous substance (8) is replenished in an amount corresponding to the expansion and pressurized to promote the consolidation of the ground.

In addition, the embankment (3) suppresses the soft ground (1) and is made of viscous material.
(8) This prevents the soft ground (1) from swelling or erupting when pressurized.

Next, FIGS. 4 to 12 show another embodiment of the Mita construction method of the present invention, in which the middle part of each of the adjacent drain columns (4) (4) constructed by the above-mentioned conventional construction method is The cylindrical body (5) is driven to the same depth as the drain column (4) using an appropriate driving device (not shown), but at this time, a non-stretchable material is inserted into the cylindrical body (5). flexible fabric,
For example, a long bag body (+3) made of non-woven fabric is built in (Fig. 5).

The diameter of this bag body 0cm is larger than the diameter of the cylinder body (5), for example, if the cylinder body (5) has a diameter of 10cm, the diameter is 30~40 cm.
It is formed to have a diameter of m, and is stored in a contracted state by being bent to form wavy folds in the circumferential direction, as shown in Fig. 7.8.

Further, as shown in Fig. 9.10, a disk-shaped tip cap body having a slightly larger diameter than the cylindrical body (5) and closing the open end is provided at the lower end opening of the bag body 03). 04)
is attached, and a detent anchor plate surface is vertically protruded from the center of the lower surface of the tip cap body side, and the tip cap body 04) is provided on both sides of the anchor plate.
A semicircular floating resistance plate Q6) (lω is arranged on the lower surface of the
One end of these floating resistance plates 000ω is rotatably attached to the tip cap body 04) by means of a pin θ'r).

This is a resistance plate rotating rod body protruding downward from both sides of the lower end of the side cylindrical body (5), and is brought into contact with and engaged with one end of the floating resistance plate 06).

Insert the bag 0ω into the cylindrical body (5) with the upper surface of the outer periphery on the tip cap body side of the bag 0 mark constructed in this manner abutting and locking the lower end surface of the opening of the cylindrical body (5). Store it and the 5th
As shown in the figure, a muddy water supply pipe a9 is inserted into the upper end of the opening, and the upper end of the bag body (5) is tied and fixed to the outer peripheral surface of the pipe Q9 with a string-like material or the like.

In this state, the cylindrical body (5) is driven into the soft ground (1) to a predetermined depth using an appropriate driving device. At this time, bag body 0
The upper surface of the outer circumference of the tip cap body (2) attached to the lower end of the cylinder body (5) is locked to the opening lower end surface of the cylinder body (5). ) while preventing dirt from entering the bag body ( ).
+3) can be press-fitted into soft ground (1) with built-in
During this press-fitting, an appropriate liquid such as the above-mentioned viscous substance (8) is injected into the bag surface through the muddy water supply pipe surface, and if necessary, viscous material is also injected into the space between the bag aperture and the cylindrical body (5). The substance (8) is injected and filled using a suitable supply tube.

In this way, after the cylindrical body (5) is cast into the soft ground (1) and the inside and outside of the bag body 03) is filled with the viscous substance (8), the cylindrical body (5) is rotated in the circumferential direction by an appropriate means. As shown in Fig. 11.12, the rod body 08) fixed to both sides of the lower end of the cylindrical body (5) opens the semicircular shape disposed on both sides of the lower surface of the tip cap body 04. One end of the floating resistance plate 0ω06) is pushed forward, and these floating resistance plates (+63 (16)) rotate outward around the bottle rm, and are press-fitted and locked into the ground.At this time, the tip cap body 04 Since the anchor plate 0ω protruding from the center of the lower surface of the unit protrudes into the ground, only the floating resistance plate 06) opens horizontally without the end cap body rotating together, and is pressed into the ground and locked. This prevents the bag body 0■ from floating.

Next, the cylindrical body (5) is extracted by appropriate means, and the filling with the viscous substance (8) may be performed while the cylindrical body (5) is being extracted.

At this time, since the floating resistance plate 00, which penetrates into the ground and is locked, is attached to the bottom of the bag (13), it is possible to reliably prevent it from being pulled out together with the cylindrical body (5).

After removing the cylindrical body (5), as shown in Fig. 4, the muddy water supply pipe (+9) of each bag body (13) cast in the soft ground (1) is connected to the pressure feeding pipe eΦ with the valve (21). At the same time, the pressurized pipe @ is connected to the mud pump a21 disposed in the mud tank (22).

In addition, a pressure gauge (23) and a valve (24) are installed in the pressure pipe [phase].
) is provided.

Thereafter, when the mud feeding pump surface is operated to force-fill the viscous substance (8) into each bag surface, the contracted bag side begins to expand in the diametrical direction.

The pressure of the viscous substance (8) supplied into the bag 03) is adjusted by the mud pump a so that the pressure is greater than the sum of the pore water pressure in the soft ground (1) and the horizontal earth pressure. As the filling amount of the viscous substance (8) increases, the bag body 03) expands to a constant diameter much larger than the diameter of the cylindrical body (5), and the expansion pressure causes the soft ground (1
) is horizontally compressed, the pore water pressure increases, and the pore water moves toward the drain column (4).
) is drained to the ground through.

At this time, since the bag surface is made of non-stretchable and flexible fabric, there is no possibility of partial expansion depending on the ground condition, unlike with rubber bags, and the bag is press-fitted and filled. The pressure caused by the viscous substance (8) is applied uniformly over the entire surface to generate a uniform expansion pressure over the entire length, and the pressure adjustment can be easily and accurately controlled by a mud water pump. The degree of consolidation of the ground can be detected, allowing for precise construction management.

Non-woven fabric is preferably used as the material forming the bag side, and non-woven fabric is inexpensive and easily available, and has relatively high tensile strength and tear strength, so it can sufficiently withstand stress during expansion. When a viscous substance (8) consisting of highly concentrated bentonite mud is press-fitted into the bag, hentonite particles form a non-woven fabric. It is trapped between the fibers of the bag to form a mud film, exhibiting water-stopping properties and allowing the bag surface to inflate smoothly.

In this way, when the consolidation and dehydration work of the soft soil M(1) due to the expansion of the hot water bag A is completed, cement mortar is supplied into the bag body 03) instead of the viscous substance (8), and the viscous substance (8) is
If the cement mortar is hardened with the bag surface expanded, it can also be used as a friction pile.

In addition, if the bag body is made of flexible fabric such as a non-water permeable and non-stretchable synthetic resin sheet, the unit volume weight of the liquid to be supplied and filled into the bag body will be the same as that of soft ground. Water and other liquids can be used without being limited to substantially equivalent viscous substances.

In addition, the above-mentioned friction piles can be formed using a viscous material (8) that is formed directly in soft ground without using a bag.
Of course, this method can also be applied to columnar bodies.

(Effects of the Invention) As described above, according to the soft ground consolidation method of the present invention, columns of viscous material whose unit volume weight is approximately equal to that of the soft ground are formed in the soft ground, and the columns are expanded. So,
It is possible to reliably consolidate the ground in the horizontal direction by pressing the surface in contact with the ground horizontally with a predetermined pressure while balancing the earth pressure on the soft ground side, and it is also possible to consolidate the ground at a deep level. By implementing a vertical consolidation method using loaded embankment together with this consolidation method, it is possible to reduce the amount of earth for the loaded embankment and shorten the construction period.

Furthermore, the horizontal consolidation density of soft ground can be easily and accurately set by adjusting the amount of viscous material supplied and the discharge pressure of the pressure pump, making it possible to maintain a constant level of consolidation and dewatering at all times. The time required to obtain the same amount of consolidation settlement can be significantly shortened, and the consolidation work can be easily managed, leading to improved workability.

In addition, when forming a columnar body using a liquid such as a viscous substance in soft ground, a cylindrical body with a long bag made of non-stretchable and flexible fabric built inside in a radially contracted state is used. After driving the bag into soft ground to a predetermined depth, supply and fill the bag with liquid while leaving the bag in the soft ground, and then pull out the cylindrical body, or insert it into the bag while pulling out the cylindrical body. If the bag is formed by supplying and filling liquid, and then supplying and filling the liquid into the bag after the cylindrical body is pulled out, the bag that is placed in the soft ground while being housed in the cylinder will be able to move in the radial direction. Since it is contracted, when the cylindrical body is pulled out and liquid is forced into the bag and filled, the bag expands to a constant diameter that is much larger than the diameter of the cylindrical body.
The pressing force against the soft ground is increased and a good ground consolidation effect can be exerted.

Furthermore, since the bag body is made of non-stretchable and flexible fabric, there is no risk of partial expansion depending on the ground conditions, unlike with rubber bags, and there is no risk of partial expansion due to the liquid being press-fitted and filled into the bag body. It is possible to apply pressure evenly over the entire surface and generate uniform expansion pressure over the entire length, and therefore, it is possible to consolidate soft ground evenly from the upper layer to the lower layer.
Moreover, the pressure adjustment can be easily and accurately controlled by a viscous material pressure pump, and compacted coal in the ground can also be detected, allowing precise construction management.

[Brief explanation of the drawing]

The drawings show an embodiment of the present invention, and FIG. 1 is a simplified longitudinal sectional side view showing the consolidation state, FIGS. 2 and 3 are longitudinal sectional views showing the process of forming columns of viscous material, and FIG. Figures 4 to 12 show examples of another consolidation method of the present invention, with Figure 4 being a simplified vertical side view, and Figures 5 and 6 showing the construction of the bag when it is buried in soft ground. FIG. 7 and FIG. 8 are enlarged cross-sectional views showing the bag in the stored state; FIG. 9 is a simplified vertical cross-sectional view of the means for preventing the bag from rising; FIG. 10 1I is a vertical sectional side view with the floating resistance plate open, and FIG. 12 is a bottom view thereof. (1)...Soft ground, (4)...Drain pillar, (5
)... Cylindrical body, (8)... Viscous substance, OD... Pressure feeding pipe, (121... Sludge pump, (13)... Bag body, Circle... Tip cap body, 0ω ...Floating resistance plate, Q
G... Pressure feed pipe. RaN j Elementary 2beq 〉Beha≧X To 6 → To BeβQ To 7 tongues → To Pegita ≥K 10 RoraN 1 again

Claims (2)

[Claims] (1) After driving a cylindrical body into soft ground to a predetermined depth, a viscous substance whose unit volume weight is approximately equal to the unit volume weight of the soft ground is supplied into the cylindrical body, and while the cylindrical body is pulled out, the cylindrical body is A method of consolidation of soft ground that is characterized by forming columns of viscous material in the soft ground that has been poured, and compressing the columns to horizontally consolidate the soft ground. (2) After driving a cylindrical body containing a long bag made of non-stretchable and flexible fabric in a radially contracted state into soft ground to a predetermined depth, the bag is Either supply and fill the liquid into the bag while it remains in the soft ground, then pull out the cylinder, or supply and fill the liquid into the bag while pulling out the cylinder, and then remove the liquid inside the bag after pulling out the cylinder. A method for consolidating soft ground, which comprises compressing the soft ground in the horizontal direction through a bag that is in contact with the soft ground by pressurizing a liquid.