JP2002054131A - Soil improving structure and soil improving method capable of controlling peripheral ground displacement - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress and control horizontal displacement and ground settlement occurring in the ground on the periphery of an area targeted for improvement. SOLUTION: A plurality of drain materials 16 are almost vertically driven into the area 13 targeted for improvement with their head portions extended above the ground surface, and a vacuum pump 15 is connected to the head portions of the respective the drain materials via a horizontal drain material 12. Then, the drain materials and the horizontal drain material are hermetically coated with a sheet material 11, and a wall body or a groove is constructed along the drain materials in the ground on the periphery of the area targeted for improvement. Further, tiltemeters 18 for measuring horizontal displacement are set at the wall body or the groove, and the peripheral ground. While the horizontal displacement at stations are measured, the vacuum pump is driven to introduce and drain water from the drain materials via the horizontal drain material to the vacuum pump, and loading fill 14 is piled up on the sheet material, depending on fluctuations of the deformation, to thereby control the horizontal deformation.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a ground improvement structure and a construction method for improving a hard ground by discharging water contained in a soft ground, and more particularly to a construction method and a construction for improving the ground while controlling the displacement of the surrounding ground. About.

[0002]

2. Description of the Related Art A vacuum consolidation method is known as an economical method for improving soft, viscous ground. Such a vacuum consolidation method, a plurality of drain materials are poured into the ground to be improved, the head is extended to the ground, and a water-permeable material such as a sand mat or drain material is laid so as to contact the drain material head, A perforated pipe is placed under the water-permeable material, and a vacuum pump is connected to it. Lay the conductive sheet material. By operating the vacuum pump, a vacuum pressure acts on the ground covered with the sheet material, and this vacuum pressure is transmitted from the perforated pipe to the drain material through the water-permeable material, and further transmitted into the ground. When vacuum pressure acts on the ground in this way, water in the ground is sucked by the vacuum pressure, flows from the drain material to the perforated pipe through the water-permeable material, and is discharged to the ground.

[0003]

However, in the conventional vacuum consolidation method, the settlement of the surrounding ground progresses as the vacuum consolidation progresses, and the surrounding ground causes horizontal displacement toward the center of the area to be improved. Therefore, it is difficult to apply the method to an improvement target area where a structure such as a house is present around the area.

The present invention focuses on the above-mentioned problems of the prior art,
The challenge was to reduce horizontal displacement and land subsidence occurring in the surrounding ground around the area to be improved.
It is an object of the present invention to provide a ground improvement method and structure that can be controlled.

[0005]

In order to solve the above-mentioned problems, according to the present invention, a plurality of drain members are driven substantially vertically into the ground to be improved, and the head is extended to the ground surface. A vacuum pump is connected to the head of the drain material through a water-permeable material and a perforated pipe, and the plurality of drain material heads, the water-permeable material and the perforated pipe are air-tightly covered with a sheet material, While measuring the displacement in the underground horizontal direction around the ground to be improved, the vacuum pump is operated to guide water from the drain material to the vacuum pump through the water-permeable material and the perforated pipe and drain the water, A ground improvement method is provided, in which a loading embankment is loaded on the sheet material in accordance with an increase or a decrease in the displacement to thereby control the displacement so as to be suppressed. In the ground improvement method described above, it is preferable that the horizontal displacement measurement is performed at a plurality of depths in the surrounding ground.

Further, in the present invention, a plurality of drain materials are driven substantially vertically into the ground to be improved, and the heads are extended to the ground to be improved. A vacuum pump is communicated through a perforated pipe, the plurality of drain material heads, the water-permeable material and the perforated pipe are air-tightly covered with a sheet material, and the drain material is provided on the ground around the ground to be improved. Along with constructing a wall or groove along, setting a measuring point to measure the horizontal displacement on the surrounding ground, while measuring the displacement at the measuring point, operating the vacuum pump and operating the drain material from the drain material By guiding water to the vacuum pump through the water passage material and the perforated pipe to drain the water, and loading the embankment on the sheet material according to the increase or decrease of the displacement, so as to suppress the displacement. Ground characterized by controlling Good method is provided. In the ground improvement method described above, horizontal displacement measurement may be performed by measuring horizontal displacement at one or more ground surfaces in the surrounding ground, and is not necessarily required to be measured at a plurality of depths in the ground.

Further, according to the present invention, in the area to be improved, a plurality of drain materials are installed substantially vertically from the ground surface into the ground, and a water-permeable material provided so as to communicate with the heads of the plurality of drain materials. And a perforated pipe, a vacuum pump connected to the perforated pipe, the plurality of drain material heads, a sheet material for hermetically covering the water-permeable material and the perforated pipe, and a periphery of the improvement target area. A wall or a groove constructed along the drain material on the ground, a horizontal displacement measuring means provided for measuring a horizontal displacement in a surrounding ground of the improvement target area, and the horizontal displacement measuring means. And a loading embankment loaded on the sheet material so as to suppress and control the displacement according to the displacement of the ground. In the above-mentioned ground improvement structure, the horizontal displacement measuring means is:
It may be installed at one or more ground surfaces in any of a wall, a groove, and the surrounding ground, and it is not always necessary to install the ground at a plurality of depths in the ground.

BEST MODE FOR CARRYING OUT THE INVENTION

In the present invention, the drain material may be any material as long as it can guide moisture contained in the ground to the upper water-permeable material and the perforated pipe. For example, a cardboard drain material, a sand drain However, the cardboard drain material is most suitable because it is relatively easy to handle and cast and is economical.

In the present invention, the wall and the groove are
It suppresses the influence of settlement and horizontal displacement on the surrounding ground of the improvement target area. Here, the wall is an SMW.
Pillar walls formed by mixing cement and local soil by the method of construction or deep mixing method, or underground walls with steel sheet piles can be used, but the ground in the area to be improved must be soft In consideration of the above, it is preferable to use an underground wall made of a steel sheet pile having relatively few heavy machines for construction. In the underground wall connected with steel sheet piles, sealing means for preventing the vacuum pressure acting on the improvement target area via the drain material from leaking out of the improvement target area from the joint portion of the steel sheet pile is provided. Must be provided. In the present invention, the groove is formed by filling a stabilizing liquid therein to prevent collapse of the groove wall. As the stabilizing liquid, bentonite stabilizing liquid, muddy water or fluidized soil can be used. . For the construction of the groove, a multi-axis stirring blade auger machine for soil cement wall construction, a horizontally moving soil cement wall construction machine, an earth auger excavator, a water jet type groove excavator, a chain saw type groove excavator, etc. Can be used. It is a rule that the depth of the wall and the groove is equal to that of the drain material. However, it is difficult to uniquely define the depth because the degree of the ground displacement to be reduced and the ground conditions are different.

In the present invention, the embankment described above may be provided only in a place where it is necessary to suppress and control the displacement in accordance with the horizontal displacement in the ground or the horizontal displacement in the ground. For example, when approaching a house, the loading embankment may be provided only on the sheet material in the adjacent area.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments will be described below with reference to the accompanying drawings, but the present invention is not limited to these embodiments. FIG. 1 is a sectional view showing one step of the ground improvement method. In FIG. 1, a ground improvement structure 10 includes a plurality of drain materials 16 that are installed at intervals of about 1 m in a substantially vertical direction from the ground surface in an improvement target area 13, and contacts the heads of the drain materials 16. Drainage material 12 composed of a water passing material (not shown) and a perforated pipe (not shown) laid in
The sheet material 11 laid on the ground surface so that the drain material 2 and the drain material 16 are airtightly covered, and a vacuum pump 15 connected to a perforated pipe of the horizontal drainage material 12 via a connecting pipe (not shown).
And an inclinometer 18 extending to a depth deeper than the improved depth in order to measure the underground horizontal displacement of the surrounding ground of the improvement target area, and controlling the displacement according to the increase or decrease of the underground horizontal displacement of the surrounding ground. And a loading embankment 14 loaded on the sheet material 11.

The inclinometer 18 is used for measuring the underground horizontal displacement in both the improvement target area 13 and the surrounding ground.
Boring is performed deeper than the improved depth, an inclinometer is inserted into each borehole, the inclination angle of the measurement point 18a is measured for each depth, and the horizontal displacement is calculated from the inclination angle at each depth. The inclinometer 18 should be arranged in multiple stages at multiple locations in the borehole, or one inclinometer should be raised and lowered in the borehole at each measurement point 18a for each measurement. Can be. In any case, since the horizontal displacement for each depth is calculated assuming that the deepest part of the measurement is a fixed point, the deepest part of the measurement is made deeper than the improved depth. Also, a sinkometer (not shown) is appropriately placed on the area to be improved and the surrounding ground surface.

As the drainage material 16, for example, a cardboard type drain material, a sand drain, or the like can be used. However, in consideration of ease of handling, economy and water collecting effect, the cardboard type drain material is not used. Optimal.

The water-permeable material as the horizontal water-permeable material 12 is formed in a belt shape, and is laid at predetermined intervals so as to contact the head of the drain material 16 protruding from the ground surface. As the perforated pipe as the horizontal water-permeable material 12, a pipe body such as a vinyl chloride pipe having a plurality of holes is used, and is extended so as to intersect the plurality of water-permeable materials. Further, the sheet material 11 has its ends buried in the sheet embedding grooves 17 so that outside air does not flow into the inside from these ends.

Next, the ground improvement method and its operation will be described with reference to FIG. First, a preparation step for vacuum consolidating the improvement target area 13 and installation of an inclinometer 18 for measuring the underground horizontal displacement around the improvement target area 13 are performed.
In the preparation process of vacuum consolidation, a plurality of drain materials 16 are placed substantially vertically at intervals of about 1 m into the improvement target area 13,
The horizontal drainage material 12 is laid so as to communicate with the heads of the drain materials 16, and the plurality of drain materials 16 and the horizontal drainage material 1 are arranged.
2 is air-tightly covered with a sheet material 11, and an end of the sheet material 11 is embedded in a sheet embedding groove 17, and a predetermined horizontal drainage material 1 is provided.
2 is connected to a vacuum pump 15 via a connecting pipe. Also, the inclinometer 18 is arranged in multiple stages at a plurality of locations in the borehole, so that the deepest part of the measurement is deeper than the improved depth, and a subsidence meter is also installed.

After the above preparation step and the installation of the inclinometer 18 are completed, the initial values before the construction, which are the criteria for the horizontal displacement and the settlement amount, are measured in both the improvement target area and the surrounding ground, and then the vacuum pump 15 is operated Then, the vacuum consolidation process of the improvement target area 13 is started.

When the horizontal displacement and the subsidence amount are measured at least once a day while performing the vacuum consolidation process, the subsidence progresses in the improvement target area 13 as the vacuum consolidation progresses, and the surrounding ground becomes the improvement target area. 13 is displaced horizontally toward the center of the thirteenth. That is, in the vacuum consolidation step, the ground contracts by reducing the pressure of the entire improvement target area 13 via the drain material 16 and the horizontal drainage material 12.
The land subsidence accompanying the contraction of the ground and the horizontal displacement of the ground toward the center of the improvement target area 13 occur, and this horizontal displacement usually becomes maximum near the ground surface, and cracks occur in the surrounding ground. Things. 5 and 6 show actual measurement examples of the amount of subsidence and the amount of horizontal displacement of the ground surface 35 days after the start of vacuum consolidation, respectively.
It can be seen that the effects of subsidence and horizontal displacement occurring in the surrounding ground are not small.

After the start of vacuum consolidation, the embankment loading is started when it is determined that the surface ground strength of the improvement target area 13 has increased to such an extent that predetermined heavy equipment work can be performed. Normally, the embankment of the loaded embankment becomes possible in about one week after the start of vacuum consolidation. At this time, due to insufficient supporting capacity of the ground and sliding deformation accompanying the embankment of the loading embankment 14, the ground is in the area 1 to be improved.
Horizontal displacement occurs from 3 toward the surrounding ground. Since the maximum value of the horizontal displacement often occurs in the underground portion, in the case of a loaded embankment, it is necessary to measure not only the ground surface displacement amount but also the ground displacement amount.

FIG. 3 shows a comparison between the horizontal displacement caused by the loading embankment and the horizontal displacement caused by the vacuum consolidation. As shown in the figure, in the case of vacuum consolidation, the horizontal displacement becomes the maximum near the ground surface in many cases, and in the case of loaded embankment, the maximum horizontal displacement often occurs in the underground, Acts to offset. Therefore, if the embankment speed and height of the loading embankment are adjusted within a range of approximately 10 to 30 cm / day while monitoring the direction and amount of displacement of the underground horizontal displacement, the amount of horizontal displacement of the surrounding ground is within an allowable range. It is also possible to control so as to be about ± 1 to 5 cm. In addition, when the displacement toward the center of the improvement target area 13 is notable, the embankment is further performed.
Depending on the situation, an increase in displacement can be suppressed by temporarily stopping the vacuum pump 15. In addition, the area in which the loading embankment is to be buried need not necessarily be formed in the entire area to be improved 13. For example, as shown in FIG.
It is effective to place the embankment emphasis on the end of the sheet material 11 on the side facing 2 from the viewpoint of suppressing the influence on the house 22.

FIG. 2 is a sectional view showing one step of the ground improvement method different from that of FIG. In the ground improvement structure of FIG.
As a configuration different from the embodiment of FIG. 1, a buffer groove 20 and a measuring device (not shown) for measuring the horizontal displacement of the ground surface in the improvement target area 13 and the surrounding ground 25 are provided. Such an inclinometer 18 is not provided, and the other configuration is the same as that of FIG.

Here, the buffer groove 20 is a groove formed between the area 13 to be improved and the surrounding ground 25 filled with a bentonite stabilizing solution or the like. Reduces settlement and horizontal displacement to the surrounding ground.

The underground wall may be constructed by connecting steel sheet piles in addition to the buffer groove 20, and FIG. 4 shows the effect of reducing the displacement of the underground wall made of the steel sheet piles during vacuum consolidation. From this example, it can be seen that by driving the steel sheet pile, the ground surface horizontal displacement was reduced to about 15% of the case without the underground wall.

By providing the buffer groove 20 or the underground wall of the steel sheet pile, the distribution of the horizontal displacement in the ground during vacuum consolidation is averaged, and in many cases, the displacement of the ground surface is maximized. By monitoring, the influence of subsidence and horizontal displacement on the surrounding ground during vacuum consolidation can be grasped. Therefore, in the embodiment of FIG. 2, the measurement of the underground horizontal displacement is not a necessary condition. In addition, the underground wall such as the buffer groove 20 or the steel sheet pile not only has the effect of preventing the transmission of horizontal displacement but also has the effect as a water blocking wall.
Even when the permeable layer 21 is present in the improvement target area as described above, the vacuum consolidation method can be applied without obstacle.

When the underground wall such as the buffer groove 20 or the steel sheet pile is provided as shown in FIG. 2, the ground improvement is performed by the same steps as the ground improvement method shown in FIG. In other words, in the ground improvement method shown in FIG. 2, instead of the inclinometer 18, a device for measuring the horizontal displacement of the ground surface is installed, and this device monitors the amount of horizontal displacement of the ground surface due to vacuum consolidation and loading embankment. However, the ground horizontal displacement of the surrounding ground is within an allowable range by adjusting the filling speed and height of the loading embankment, and stopping and restarting the vacuum pump 15 so that the horizontal displacement of the ground due to the two cancels out. It is controlled so as to be about ± 1 to 5 cm.

[0025]

According to the present invention, while performing vacuum consolidation,
By performing embankment loading based on the measured data of the horizontal displacement of the ground in the surrounding ground, the horizontal displacement of the surrounding ground can be greatly reduced, for example, in places where houses are densely packed around the area to be improved Also, the vacuum consolidation method can be applied.

Further, in the present invention, since the apparatus for measuring the horizontal displacement in the ground is used, even if the ground is complicated, the embankment speed and height of the loaded embankment and the vacuum operation can be determined based on the accurate horizontal displacement in the ground. Stop / restart can be reliably controlled. In the present invention, since the wall and the buffer groove are provided, the horizontal displacement of the surrounding ground can be further reduced by the blocking effect and the displacement absorbing effect. In addition, since the water blocking effect of the wall and the buffer groove can prevent or block the lowering of groundwater in the surrounding ground, the settlement of the surrounding ground can be greatly reduced. Furthermore, when there is a permeable ground in the area to be improved, it was difficult to apply the vacuum consolidation method due to air leakage, but it was possible to prevent air leakage by providing walls and buffer grooves, The application of the vacuum consolidation method became possible. In addition, by providing the wall, the underground horizontal displacement is averaged, so that displacement control based on the ground surface displacement can be performed.

[Brief description of the drawings]

FIG. 1 is a sectional view showing one step of a ground improvement method according to the present invention.

FIG. 2 is a cross-sectional view showing one step of a ground improvement method different from FIG.

FIG. 3 is a diagram for comparing and explaining underground displacement caused by vacuum consolidation and embankment loading;

FIG. 4 is a diagram for explaining the effect of reducing horizontal displacement by a wall made of steel sheet pile.

FIG. 5 is a diagram showing a subsidence shape of the ground due to vacuum consolidation.

FIG. 6 is a diagram showing horizontal displacement of the ground due to vacuum consolidation.

FIG. 7 is a cross-sectional view showing an arrangement of a loading embankment in an improvement target area.

[Explanation of symbols]

 Reference Signs List 10 ground improvement structure 11 sheet material 12 horizontal drainage material (water passing material and perforated pipe) 13 ground to be improved 14 embankment 15 vacuum pump 16 drain material 18 inclinometer

 ────────────────────────────────────────────────── ─── Continuing from the front page (72) Inventor Tetsu Koga 2-5-8 Kita-Aoyama, Minato-ku, Tokyo Intra-company group (72) Inventor Mutuo Ohno 2-58-8 Kita-Aoyama, Minato-ku, Tokyo Stock Intra-company group (72) Inventor Kimiaki Ishihara 2-5-8 Kita-Aoyama, Minato-ku, Tokyo Co., Ltd. Intra-company group (72) Inventor Hirobo Shima 3-13-14 Nishiazabu, Minato-ku, Tokyo Kajitani Engineer Co., Ltd. (72) Inventor Kazuyoshi Nakakuma 422 Takemazawa, Miyoshi-cho, Iruma-gun, Saitama Maruyama Industry Co., Ltd. F-term (reference) 2D043 CA04 CA08 CB08 DA04 DA05 DA09

Claims (3)

[Claims] 1. A plurality of drain materials are poured substantially vertically into the ground to be improved and their heads are extended to the ground surface, and the heads of the plurality of drain materials are connected to each other through a water-permeable material and a perforated pipe. The vacuum pump is communicated, and the plurality of drain material heads, the water-permeable material and the perforated pipe are air-tightly covered with a sheet material, and while measuring a horizontal displacement in the ground around the ground to be improved, Operate the vacuum pump to guide the water from the drain material to the vacuum pump through the water passage material and the perforated pipe to drain the water, and fill the embankment on the sheet material according to the increase or decrease in the displacement. A ground improvement method, wherein the displacement is controlled by loading the ground. 2. A plurality of drain materials are poured substantially vertically into the ground to be improved, and their heads are extended to the ground to be improved. A water-permeable material and a perforated pipe are provided at the heads of the plurality of drain materials. And a plurality of drain material heads, the water-permeable material and the perforated pipe are air-tightly covered with a sheet material, and a wall is formed along the drain material on the ground around the ground to be improved. While constructing a body or a groove, a measuring point for measuring a horizontal displacement is set on the surrounding ground, and while measuring the displacement at the measuring point, the vacuum pump is operated to operate the drainage material from the drainage material. And guiding the water to the vacuum pump through the perforated pipe to drain the water, and loading the embankment on the sheet material in accordance with the increase or decrease in the displacement to control the displacement. Ground improvement method characterized by the following. 3. A plurality of drain materials which are installed substantially vertically from the ground surface into the ground in the area to be improved, a water-permeable material provided so as to communicate with the heads of the plurality of drain materials, and a perforated material. A pipe, a vacuum pump connected to the perforated pipe, a plurality of drain material heads, a sheet material for hermetically covering the water-permeable material and the perforated pipe, and a ground around the improvement target area. A wall or a groove constructed along the drain material, a horizontal displacement measuring unit provided for measuring a horizontal displacement in a ground around the improvement target area, and a displacement from the horizontal displacement measuring unit. A ground embankment loaded on the sheet material so as to suppress and control the ground in accordance with the ground embankment.