JPS6251325B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a construction method for constructing improved piles in soft ground at the bottom of water.

In order to improve the soft ground at the bottom of the sea, rivers, lakes, etc., a few construction methods have already been proposed for constructing improvement piles in the soft ground. That is, the following construction methods are known.

(1) Inside a casing that is driven into soft ground, the sand in the sand bag is actively added water to moisten it, form a dense and tightly packed sand bag column, and then settle to the bottom of the casing. After that, only the casing is removed (hereinafter referred to as the water tightening method)
- For example, Tokuko Sho 53-16604, Tokuko Sho
Such as those described in Publication No. 54-20243.

(2) After the casing is driven into the soft ground with an underwater bottom, the water that has penetrated into the casing and remains is completely drained out, and then the ground reinforcement using sandbags or quicklime is applied inside the anhydrous casing. A construction method in which a drug bag is thrown in, allowed to fall, and only the casing is removed (hereinafter referred to as the waterless construction method) - for example, Japanese Patent Publication No. 11177/1983 or Japanese Patent Publication No. 1983/1983-
Such as those described in Publication No. 570.

However, all of these conventional construction methods have the following problems or drawbacks.

In the water-tightening method (1), the sand inside the sand bag is tightly water-tightened using a sand bag column, which becomes too hard and loses its fluidity and flexibility, making it difficult to follow the fluctuations of the soft ground under water. There was a problem that it might be difficult to do so.

In addition, in order to tighten the water and make it into a high-density sand bag pillar,
Compared to the method of using sand in a naturally moist state, extra sand was required, which was unfavorable in terms of material cost.

In the waterless construction method (2), firstly, it is technically difficult to completely drain the water that has entered the casing, and even if it were possible, it would require a great deal of labor and extra equipment. . Second, since the water that has entered the casing is discharged without being used as a damper when the sandbag, etc. settles, the weight of the sandbag, etc. increases, and there is a risk that the sandbag, etc. may break inside the casing. It was hot.

The purpose of the present invention is to overcome both the drawbacks of the conventional water tightening method and anhydrous method described above, and to eliminate the need to pour water into the sand, etc. in the sand bag placed in the casing, and to eliminate water from entering the casing and remaining there. There is no need to drain the water in advance, and the water inside the casing is used as a damper when the sandbag pillars settle, making it easy to construct and economically improving the soft ground at the bottom of the water by using naturally moist sand as it is. The object of the present invention is to provide an improved construction method for constructing piles.

In order to achieve this object, the first invention provides a method for constructing improved piles in soft ground with a water bottom. A flexible bag-like body whose diameter is approximately equal to or slightly smaller than the inner diameter of the casing is inserted, and a bottomed cylindrical bag filled with sand is placed over the flexible bag-like body into the casing. Forming a sand bag column with the flexible bag-like body at the tip, allowing the sand bag column to sink to the bottom of the casing while draining water below the flexible bag-like body in the casing, The second invention is characterized in that only the casing is removed while leaving the pillar in the soft ground at the bottom of the water.The second invention is characterized in that when constructing an improved pile in the soft ground at the bottom of the water, the casing is driven into the soft ground at the bottom of the water. After this, a flexible bag-like body filled with fluid and whose outer diameter in its natural state is approximately equal to or slightly smaller than the inner diameter of the casing is inserted into the casing, and the ground is strengthened from above the flexible bag-like body. A bottomed cylindrical bag filled with the agent is put into the casing to form a soil strengthening agent bag pillar with a flexible bag-like body at the tip, and the soil strengthening agent bag pillar is inserted into the flexible bag inside the casing. This system is characterized by draining the water below the casing and allowing it to settle to the bottom of the casing, leaving the soil strengthening agent bag pillars in the soft ground at the bottom and removing only the casing. The third invention is, when constructing an improved pile in soft ground with a water bottom, after driving a casing into the soft ground with a water bottom, the casing is filled with fluid, and the outer diameter of the casing is approximately equal to the inner diameter of the casing in its natural state. A slightly smaller flexible bag-like body is inserted, and sand is directly filled into the casing from above the flexible bag-like body to form a sand column with the flexible bag-like body at the tip. The method is characterized in that the sand column is allowed to settle to the bottom of the casing while draining water below the flexible bag-like body in the casing, and only the casing is removed, leaving the sand column in the soft ground at the bottom of the water. And, the fourth invention provides for, when constructing improved piles in soft water bottom ground, after driving a casing into the soft water bottom ground, the casing is filled with fluid and the outside of the pile is removed in a natural state. A flexible bag-like body whose diameter is approximately equal to or slightly smaller than the inner diameter of the casing is inserted, and a soil reinforcement agent is directly filled into the casing from above the flexible bag-like body to form a flexible bag-like body. A column of soil reinforcement is formed at the tip, and the column of soil reinforcement is allowed to sink to the bottom of the casing while draining water below the flexible bag-like body in the casing, and the column of soil reinforcement is caused to sink to the bottom of the casing. The feature is that only the casing is removed, leaving it in the soft ground.

Hereinafter, the present invention will be specifically explained with reference to the drawings.

FIG. 1 is a vertical cross-sectional view of an improved pile making device (principal part) according to an embodiment of the first (second) invention, and FIG.
The figure is a longitudinal cross-sectional view showing a state in which a sand bag pillar (soil reinforcement bag pillar) with a balloon (fluid-filled flexible bag-shaped body) at its tip sinks while draining water inside the casing.

First, the first invention will be explained.

In FIG. 1, 1 is a casing, and 2 is a bottom plug provided at the bottom of the casing so as to be openable and closable with a hinge or the like.
The casing 1 has already been driven into the soft ground 4 at the bottom of the water (3 is the water surface), and water W has entered the casing 1 and remains (the casing 1 is inserted below the water surface 3 with the bottom plug 2 open). When the bottom plug 2 lands on the soft ground 4, the bottom plug 2 is automatically closed by a hinge or the like, so water W remains inside the casing 1).

A support frame 5 is fixed to the upper end of the casing 1,
By hitting the upper end 6 of this support frame 5 in the direction shown by arrow H with a hammer (not shown) installed on a work boat (not shown), the casing 1 is driven into the soft ground 4 at the bottom of the water. It will be absorbed.

An intermediate plate 7 is fixedly installed in the middle of the support frame 5, and a sandbag attachment device 8 is attached below the intermediate plate 7. A sand bag 9, which has been sewn in advance into a bottomed cylindrical net bag having a required diameter and length, is compressed in the longitudinal direction and attached to the outer periphery of the sand bag attachment device 8 in an accordion shape. Note that the portion of the sand bag 9' containing the sand S is stretched in the longitudinal direction by the weight of the sand S.

On the other hand, a sand feed pipe 10 with a hopper is mounted so as to be able to be extracted, passing through the central opening of the intermediate plate 7 and the sand bag mounting device 8.

A guide cylinder 11 is provided at the lower part of the support frame 5 to serve as a guide when filling the sand bag 9 with sand S. Furthermore, a movable stopper 12 consisting of a plurality of rollers is provided at the lower end opening of the guide tube 11 (at the border with the upper end of the casing 1). Movable stopper 12
can be freely inserted and removed in a direction substantially perpendicular to the axial direction of the guide tube 11 via a link 14 by operating a suitable actuator, such as a hydraulic cylinder 13.

Reference numeral 15 designates a balloon (a fluid-filled flexible bag-like body), and a balloon whose outer diameter in its natural state is almost equal to or slightly smaller than the inner diameter of the casing 1 can be preferably used. Reference numeral 16 indicates the upper surface of the water W that has entered and remains in the casing 1, and the balloon 15 is inserted and placed on the water surface 16.

Note that the balloon 15 does not necessarily have to be in contact with the water surface 16, and may be inserted above the water surface 16, for example, like a balloon 15'. In short, it is sufficient that the balloons 15, 15' are inserted between the water surface 16 and the sand bag 9, and when the sand bag 9 sinks inside the casing 1 with the balloon 15 at the tip, the same is true for both. state (see Figure 2).

However, if the amount of water W remaining in the casing 1 is too small and the water level 16 is too low, water may be added to the casing 1 to increase the water level 16.
After bringing it somewhat close to the top of casing 1,
Preferably, the balloon 15 is inserted into the casing 1.

A drain port 17 is located slightly above the bottom end of the casing 1.
A drain pipe 18 is provided so as to communicate with the drain port 17 and project above the water surface 3. 19 is a drain pump, and 20 is a drain valve.

The procedure for carrying out the first invention using the apparatus shown in FIG. 1 will be described below.

After driving the casing 1 into the soft underwater ground 4,
Balloons 15, 15' are inserted into the casing 1 (on or above the water surface 16). As the balloon 15, an elastic ball containing a gas such as air or an elastic ball containing a liquid such as water - in short, a flexible bag-like body containing a fluid may be used.
Therefore, the material for the balloon 15 is preferably one that is neither breathable nor water permeable (such as rubber or synthetic resin).

Thereafter, naturally moist sand S is supplied from a work boat (not shown) through a sand pipe 10 with a hopper, and the sand bag 9' is filled with sand in the guide tube 11.
At this time, the movable stopper 12 is located at the lower end opening of the guide tube 11 and supports the bottom of the sand bag 9'.

When the sand filling reaches a certain stage, the stopper 12 is removed by operating the hydraulic cylinder 13 and the link 14. As a result, the sand bag 9' falls into the casing 1 under its own weight and reaches the top surface of the balloon 15 (see FIG. 2). At this time, the sand filling is still continuing, and the pressure by the sand bag column 21 is applied to the water W in the casing 1 via the balloon 15.

Therefore, the water W is pushed in the direction of the arrow in FIG. Due to this pressure and the auxiliary suction action of the drain pump 19, the water W is discharged out of the casing 1 through the drain pipe 18. At this time, the drainage speed, that is, the settling speed of the sand bag column 21, can be adjusted by the sand S supply speed and the opening degree of the drainage valve 20.

In this way, the sandbag pillar 21 with the balloon 15 at the tip is allowed to settle into the casing 1, and finally, when the sandbag pillar 21 reaches the bottom, the casing 1 is pulled up (at this time, the bottom plug 2 is moved naturally by the hinge etc. sandbag pillars 21 are left in the soft ground 4 as ground improvement piles. Note that the balloon 15 may remain at the bottom of the improved pile, but it is also possible, for example, to provide a means such as a needle on the top surface of the bottom plug 2 of the casing 1 to crush the balloon 15. .

The most important thing in the first invention is the tip of the sandbag pillar 21, that is, the sandbag pillar 21 and the casing 1.
A balloon 15, which is a fluid-filled flexible bag, is provided at the boundary with the water W inside. Since the balloon 15 is filled with fluid, there is internal pressure, and since it is a flexible bag-like body, the casing The casing 1 is deformed into a slightly flat shape in a direction perpendicular to the axial direction of the casing 1, and is pressed tightly against the inner wall of the casing 1 (see FIG. 2). In addition, there are some unevenness inside the casing, but even if there are unevenness, the flexible bag-like body deforms to follow the unevenness, so the flexible bag-like body inside the casing Watertightness is completely achieved, and as a result, water intrusion into the sandbag pillar can be completely prevented.

Therefore, the balloon 15 located at the tip of the sandbag column 21 acts as a water barrier material that prevents water W from entering and rising into the sandbag column 21, and also acts as a water barrier material to prevent water W from entering and rising into the sandbag column 21. It also acts as a piston when pushing down W to drain water.

As a result of preventing the water W from entering and rising into the sand bag pillar 21 by the balloon 15, the sand S in the sand bag pillar 21 does not boil (boiling up, rising), so the sand bag 9' The sand S filled in the sand bag pillar 2
The time required to form and stabilize 1 (cycle time) is shorter than the conventional water tightening method,
Workability is improved.

At the same time, the sand S forming the sand bag column 21 will be buried in the soft ground 4 at the bottom of the water while maintaining its natural moist state, so it will be buried in the soft ground 4 at the bottom of the water. Compared to bag piles, they can maintain more flexibility and fluidity, and can more easily and flexibly follow fluctuations in the soft ground 4.

Furthermore, since it is sufficient to simply use the naturally wet sand S, no extra sand is required compared to the conventional water tightening method, and the material cost can be reduced accordingly.

Note that when filling the balloon 15 with fluid,
By adding a small amount of fluid, the balloon 15 can be freely deformed by external pressure. By doing so, when the water rises toward the sand pile, or conversely when the sand pile descends toward the water, the balloon 15 easily deforms before the water or the sand pile rises or falls. As a result, the sand boiling phenomenon can be prevented and the quality of the sand pile can be improved.

Therefore, the amount of fluid that can be placed into the balloon 15, ie, the flexible bladder, can be as much as is considered optimal in each case.

The above was an explanation of the first invention, but
The same applies to the second, third and fourth inventions.

In other words, as a material constituting the improved pile for the underwater soft ground 4, the sand bag pillar 2 is made by filling the sand bag 9' with sand S.
1, it is also possible to use a soil-strengthening agent bag post 21' in which a bag 9' is filled with a soil-strengthening agent (for example, lime, quicklime, slaked lime, etc.). This is the second invention.

Further, in the first and second inventions, the balloon 1
Since the balloon 5 can act as a complete water-shielding material and piston, the balloon 15 is directly filled with sand S or the ground strengthening agent without using the bags 9, 9', and the sand column or the ground is strengthened. It is also possible to form reinforcement columns. This is the third and fourth inventions.

In the third and fourth inventions, devices and members such as the sandbag attachment device 8, sandbag 9, guide tube 11, stopper 12, hydraulic cylinder 13, and link 14 as shown in FIG. 1 are no longer necessary. Become.

As explained above, since the present first to fourth inventions have the above-mentioned configurations, the following effects can be achieved.

The balloons at the tips (bottoms) of the sand bag pillars, soil reinforcement bag pillars, sand pillars, and soil reinforcement pillars are in close contact with the inner wall of the casing and act as pistons. The water in the casing is pushed down by the pump's auxiliary suction (auxiliary suction) and gradually settles, and the water in the casing acts as a damper when each column sinks, so these two work together to reduce the settling speed of each column. It can be controlled more appropriately.

Therefore, compared to the conventional waterless construction method explained at the beginning, the water that inevitably enters the casing and remains can be effectively used as a damper when sandbag columns settle, making it easier and more reliable. It is possible to control the settling speed of sandbag pillars, etc.

In addition, since the water inside the balloon and casing acts as a damper and a (movable) stopper, there is no risk of the bag breaking even if the weight of the sand bag column becomes large, and in principle it can be applied to any depth of water. be able to.

The balloon receives pressure from above and below and adheres to the inner wall of the casing, and acts as a water barrier to prevent water from entering and rising into the sandbag pillars, etc., so the sand in the sandbag pillars does not boil. Sand bag pillars etc. can be formed stably in a short time.
Therefore, it has good workability.

At the same time, sandbag pillars, etc. can be embedded in the soft ground at the bottom of the water while maintaining natural moisture, making them more flexible than the highly densely packed piles created using the conventional water tightening method. Since it is possible to create certain improved piles, it is possible to more easily and flexibly follow changes in soft ground.

In addition, since no extra sand is required, the amount used can be reduced, making it economically advantageous. Furthermore, since water can be completely blocked during settling in the casing, improved piles can be created stably and quickly without unnecessarily reacting with water, even when using a soil reinforcement agent mainly composed of quicklime. be able to.

[Brief explanation of the drawing]

FIG. 1 is a vertical cross-sectional view of an improved pile making device (principal part) according to an embodiment of the first (second) invention, and FIG.
The figure is a longitudinal cross-sectional view showing a state in which a sand bag pillar (soil reinforcement bag pillar) with a balloon (fluid-filled flexible bag-shaped body) at its tip sinks while draining water inside the casing. 1...Casing, 4...Soft ground at the bottom of the water, 10...
Sand conveying pipe with hopper, 15...Balloon (fluid-filled flexible bag-like body), 21...Sand bag column (or 21'...Soil reinforcement bag column).

Claims (1)

[Claims] 1. When constructing an improved pile in soft ground with a water bottom, after driving a casing into the soft ground with a water bottom, the casing is filled with fluid and its outer diameter is the same as the inner diameter of the casing in its natural state. A flexible bag-like body that is approximately the same size or slightly smaller is inserted, and a bottomed cylindrical bag filled with sand is thrown into the casing from above the flexible bag-like body.
A sandbag pillar is formed with a flexible bag-like body at the tip,
The sand bag column is allowed to sink to the bottom of the casing while draining water below the flexible bag-like body in the casing, and only the casing is removed, leaving the sand bag column in the soft ground at the bottom of the water. An improved pile construction method for soft submerged ground characterized by: 2. When constructing improved piles in soft ground with a water bottom, after driving a casing into the soft ground with a water bottom, the outer diameter of the casing may be approximately equal to or slightly smaller than the inner diameter of the casing in its natural state, with fluid inside the casing. A flexible bag-like body is inserted, and a bottomed cylindrical bag filled with a soil strengthening agent is put into the casing from above the flexible bag-like body, and the ground is formed with the flexible bag-like body at the tip. A reinforcing agent bag pillar is formed, and the soil strengthening agent bag pillar is allowed to sink to the bottom of the casing while draining water below the flexible bag-like body in the casing, and the soil strengthening agent bag pillar is made to soften under water. This is an improved pile construction method for soft underwater ground, which is characterized by leaving only the casing in the ground and removing it. 3. When constructing improved piles in soft ground with a water bottom, after driving a casing into the soft ground with a water bottom, the outer diameter of the casing may be approximately equal to or slightly smaller than the inner diameter of the casing in its natural state, with fluid inside the casing. A flexible bag-like body is inserted, and sand is directly filled into the casing from above the flexible bag-like body to form a sand column with the flexible bag-like body at the tip, and the sand column is A soft water bottom ground characterized by draining the water below the flexible bag-like body in the casing and allowing it to settle to the bottom of the casing, leaving the sand columns in the soft water bottom ground and only removing the casing. Improved pile construction method. 4 When constructing improved piles in soft ground with a water bottom, after driving a casing into the soft ground with a water bottom, the outer diameter of the casing may be approximately equal to or slightly smaller than the inner diameter of the casing in its natural state, with fluid inside the casing. A flexible bag-like body is inserted, and a soil strengthening agent is directly filled into the casing from above the flexible bag-like body to form a soil-strengthening agent pillar with the flexible bag-like body at the tip. The soil reinforcement column is allowed to sink to the bottom of the casing while draining water below the flexible bag-like body in the casing, and only the casing is removed, leaving the soil reinforcement column in the soft ground at the bottom of the water. This is an improved pile construction method for soft underwater ground.