JPS5869918A - Improving work for soft ground - Google Patents

Abstract

PURPOSE:To improve soft ground without the use of load banking by a method in which a cylindrical casing whose lower end is provided an opening and closing body is driven into the ground while keeping the opening and closing body open, and the opening and closing body is closed underground to compress soft soil inside the casing. CONSTITUTION:The lower end of a steel pipe 1 is opened by extending bendable plates 4 and 5, and then the steel pipe 1 is driven underground by driving a vibrator 12. Then, an oil-pressure pump 6 is operated, an oil-pressure arm 2 is extended, the bendable plates 4 and 5 are bent, and the lower end of the steel pipe 1 is closed to take soft soil into it. Then, filter sand 15 is charged, an oil- pressure jack 13 is actuated to lower a pressing plate 14, and thereby pressure is slowly applied to the filter sand 15. When the pressing plate 14 is immersed under water, the pressing operation is stopped, the pressing plate 14 is lifted, and filter sand 15 is again charged and pressed. When soft soil inside the steel pipe 1 is compressed to a given value, the pressing operation is ended and the steel pipe is pulled out.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for improving soft ground of various soil types including humus and sand.

A variety of ground improvement effects have been known for a long time, but they can be broadly classified into the following three types. The first method is to improve sandy ground by applying dynamic loads such as vibrations and shocks using an exciter, etc., such as the vibroflow method, the piston construction method, etc. There are the pro-compounding method and the direct power compaction method. The second is a construction method that mainly improves cohesive soil by driving water-absorbing materials such as sand and drain paper into the ground to remove water and promote consolidation. There are lenin method and pack drain method. The third is a construction method in which setting materials such as cement and water glass, and water-absorbing and expanding materials such as lime are mixed into the ground (2-mix A) to strengthen the density.
There are injection methods, deep mixing methods, and chemico pile methods. However, these conventional ground improvement methods (C2) are limited in the soil conditions to which they can be applied, and cannot be expected to be particularly effective against humic soil (2).
In addition, since it is a dynamic construction method that adds two vibrations and [1], there are difficulties in construction management, and there is also a drawback that the soil improvement effect (:) is limited. In many cases, a loaded embankment is required, and in this case, the consolidation period can be as long as 3 to 6 months.
The disadvantage is that the time and economic losses are large.

Furthermore, the third construction method requires a large amount of material to be mixed into the ground and stirred, so there is a drawback that the construction cost is high.

The purpose of the present invention is to provide an improved construction method for soft ground that eliminates the drawbacks of these conventional construction methods. The provided cylindrical casing is driven into soft ground with the opening and closing body in an open state, and then the opening and closing body is in a closed state and soft soil is taken into the cylindrical casing. Detailed explanation from the upper part of the shaped casing.

First, the equipment used in the construction method of the present invention will be explained.

Reference numeral 1 denotes a rectangular steel pipe serving as a cylindrical casing, and four accommodation tubes 3 for accommodating hydraulic arms 2 are fixed to the inner surfaces of a pair of opposing walls 1a and 1b, respectively. The tip of each of the hydraulic arms 2 is connected to the opposing wall 1a.
, lb are pivoted to the respective upper ends of a pair of flexible plates 4.5 supported at their respective lower ends so as to be located along the inner surface of the steel tube IC. The bending plate 4 is divided into two parts at the center in the longitudinal direction, and protrusions 4a, 4b are provided opposite to these divided parts, and these opposing protrusions 4m, 4...b are connected so as to be bendable. This makes it flexible and flexible. The bending plate 5 also has the same configuration, but the protrusions ja and 5b here are provided so as to be positioned alternately with the protrusions 4a and 4b, so that the bending plates 4 and 5 are bent to the maximum extent. In this case, each of the protrusions 4a, 4b, 5a, and 5b4 is located in each of the two adjacent spaces so as to substantially close them. That is, when the pair of bending plates 4.5 are bent to the maximum limit, the lower end of the steel pipe 1 is closed, and the pair of bending plates 4.5 (=therefore forming an opening/closing body) are closed. 6 indicates each hydraulic arm 2.
This is a hydraulic pump to drive the. 7 is a water drain filter formed on each wall surface of the steel pipe 1; 8 is the steel pipe 1;
This is a measuring device installed at the lower end of the pore water pressure and earth pressure. Reference numeral 9 denotes an injection port that communicates with the lower end of the steel pipe 1 (2 formed inlet passage 10), and the inflow passage 10 is connected to an injection pipe 11 provided along the outer wall surface of the steel pipe 1.
-612 communicating with is an exciter to which the upper end of the steel pipe 1 is fixed, and this exciter 12 is connected to the hydraulic pump 6.
A hydraulic jack 13 driven by is also attached.

Reference numeral 14 denotes a pressure plate that is moved up and down by the hydraulic jack 13, and has a large number of drainage holes (not shown) transparent therein.

Next, four construction methods of the present invention that are carried out using the apparatus configured as described above will be explained.

The pair of bent plates 4.5 are extended, the lower end of the steel pipe 1 is opened, and the steel pipe 1 is driven into the soft ground to be improved by moving the vibrator 12 once (see Figure 1). . Next, a pressure compression step is performed (see FIG. 2). Introduction,
The hydraulic pump 6 is driven to extend each hydraulic arm 2, bend the pair of bending plates 4.5 to their maximum limits, and close the lower end of the steel pipe 1. In this state, (2) soft soil will be taken into the steel pipe 1 (2).
2. Next, a filter sand 15 is introduced from the open upper end of the steel pipe 1, and the pressure plate 14 is lowered by driving the hydraulic jack 13 to slowly pressurize the filter sand 15 from above. If this pressurization is applied rapidly, the pore water pressure will rise sharply. Also, if the friction acting on the inner wall surface of the steel pipe 1 is excessive, the load may not be sufficiently transmitted to the lower end of the steel pipe 1. Therefore, the amount of pressurization is gradually increased while measuring the pore water pressure value and earth pressure value with the measuring device 8. Then, when the water reaches a state where the water reaches the top of the pressure plate 14,
After the pressurizing operation is stopped and the pressurizing plate 14 is raised, the filter sand 15 is put in again and the above-described pressurizing operation is performed. By repeating the above operations and compressing the soft soil in the steel pipe 1 to a predetermined value, the pressure compression process is completed. Next, in the drawing process (see Fig. 3), the hydraulic arm 2 is retracted to make the pair of bending plates 4 and 5 extend again, and the lower end of the steel tube 1 is opened. This state sounds;
(Secondly, the steel pipe 1 is pulled out from the soft ground. The void created by this pulling out in the soft ground C2 is injected at the same time as the pulling operation) (Injecting sand or cement milk from the pipe 11) -, this is ejected from the injection port 9 and filled up.

By sequentially applying each of these steps to the adjacent soft ground 4, the soft ground is compressed and strengthened as shown in Figure 7, C2 plus C2.

In FIG. 7, 16 is compressed and strengthened soil, and 17 is injected sand or cement milk.

In the above-mentioned embodiment, the steel pipe was driven in using a vibrator, but it is also possible to use the weight of the construction machine to press-fit the steel pipe with a hydraulic jack. By using this, a series of processes such as driving steel pipes, compressing the ground, and pulling out steel pipes can be carried out without noise or vibration. Moreover, a circular steel pipe 0 or the like can also be used as the cylindrical casing. Furthermore, the opening/closing body may also have the configuration of the above-mentioned embodiment (but is not limited to two).

As is clear from the above description, the present invention can provide the following effects. 1st
(Secondly, since it is a static pressure compression operation that does not require vibration etc., the compression load and amount of compression can be freely selected, and the desired ground improvement effect can be achieved. 2C2) Necessary materials Only a small amount of sand or cement is needed to fill the void after the casing is pulled out, and it can be done at the same time as the construction is completed (
Second, since consolidation is almost completed immediately, there is no need for soft embankment, which is extremely economical in terms of cost and time. Sixth, the compaction effect on the humus layer, which was not sufficiently effective with conventional construction methods, is significant. 4C2: Since pressure is applied to a certain amount of blocked ground, there will be no subsidence to the surrounding ground.
1. It does not have any negative effects such as rising or flowing.

[Brief explanation of drawings]

The figures show preferred embodiments of the present invention, with Fig. 1 being a partial cross-section showing a steel pipe driven into soft ground, and Fig. 2 being a partially omitted partial cross-section showing a pressurized compression operation state. Figure 3 is a partially omitted partial cross-sectional view showing the steel pipe pulling operation, Figure 4 is a cross-sectional view of the steel pipe showing the open/closed state, and Figure 5 is a cross-sectional view of the steel pipe showing the closed state. Figure, 6th
The figure is a partial front view of the bending plate, and FIG. 7 is a sub-sectional view of the soft ground showing the completed construction state. 1...Steel pipe 2...Hydraulic arm 4゜5・:・
Bent plate 6...Hydraulic pump 7...Drain filter 8...Measuring instrument 9...Inlet 12...
″・Exciter 1・3・Hydraulic jack 14・・
・Pressure plate 15...Filter sand. Patent applicant: Geotechnical Laboratory Co., Ltd.

Claims (1)

[Claims] Lower end part number = A cylindrical casing equipped with an opening and closing body that can be opened and closed by an appropriate drive mechanism is driven into the soft ground to be improved (2) with the opening and closing body in the open state, and with the opening and closing body in the closed state, the cylindrical casing is After the soft soil is poured into the casing, this soft soil is applied from the upper part of the cylindrical casing.