JPS6030814B2 - Method to prevent subsidence of surrounding ground due to excavation - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a construction method for preventing deformation, subsidence, etc. of the surrounding ground due to excavation when excavating soft ground using the mountain-side/strike method.

BACKGROUND ART Conventionally, when constructing structures such as building foundations, the ground is generally excavated using the mountain crab/cut beam method.

In recent years, structures such as building foundations, public ditches, and subways have often been constructed on so-called soft ground such as reclaimed land or intermediate clay layers. The crab-cut beam method is usually used.
However, when excavating soft ground using the mountain retaining and strait construction method, for example, as shown in Figure 1, after installing the second tier 2, there is a need to wait until the next lower tier is installed, as shown by the two-dot chain line. During this period, the excavation-faced bell portion of the retaining wall 1 deforms inward, which causes the surrounding ground 3 to sink 6.
(or deformation, etc.) may occur, causing damage to nearby buildings or damaging structures.

This subsidence, deformation, etc. of the surrounding ground 3 is a phenomenon that spreads widely over a distance of several tens of meters, and the function of the retaining wall 1 and strut 2 is perfect, and there is no deformation or destruction of them. The above damage occurs even though it has not occurred, so it is a problem that needs to be dealt with. By the way, the above surrounding ground 3
The causes of subsidence and deformation are, in the case of soft ground,
Excavation places deep in the ground (excavation surface)
It is estimated that the ground will flow and slide toward the ground, and the result will be subsidence and deformation of the surrounding ground 3.

Therefore, conventional methods have been used to reduce the subsidence of the surrounding ground due to excavation of soft ground,
As a way to prevent deformation, etc., ■ Further increase the rigidity of the retaining wall.

In other words, increase the strength and rigidity of the sheet piles and struts, or use continuous underground walls as mountain crab walls. @ Further increase the number of struts. ■ Create an appropriate number of compaction piles near the bottom of the excavation (Japanese Unexamined Patent Publication No. 51-55111).

Measures such as these were planned and implemented.

However, method (2) has the problem that it is difficult to recover temporary construction materials such as sheet piles and struts, and it is too expensive to kill oaks. In addition, the @ method has the problem that the presence of struts causes various difficulties in the construction of the structure in question, causing a great deal of trouble. Furthermore, in the case of method Q, the continuous pile is
Near the bottom of the excavation, the slip failure line of the ground is assumed and this is fully taken into consideration, and an appropriate number of sub-consolidation piles are constructed so as to cross the slip failure line. Depending on how they are placed, it is unclear whether or not they will truly achieve the desired effect, and it is not always possible to fully rely on them.
The piles had to be created near the bottom of the excavation using a special construction method, which naturally made the construction technique difficult and inefficient, and it was unclear whether the intended compaction piles had been created. In other words, it is difficult to have full confidence in the effectiveness of the pile, and the material used for the continuous consolidation pile is special because it absorbs water, causes a hydration reaction, and strengthens the ground through the dehydration effect. Firstly, it is unclear whether the intended hydration reaction and dehydration effect are occurring after construction, and vertically compacted piles are simply scattered in the ground, so it is difficult to absorb the moisture necessary for the hydration reaction. Although it has absorption and dehydration effects, it has drawbacks and problems, such as being powerless against excess water and not being able to completely treat groundwater.

The purpose of this invention is to prevent subsidence, deformation, etc. of the surrounding ground that occurs when excavating soft ground using the retaining and sill construction method, and more specifically, to It has appropriate rigidity and water-stopping properties to prevent ground flow and slippage that may occur.
In addition, we provide an improved subsidence prevention method to prevent subsidence, deformation, etc. of the surrounding ground that occurs until the next lower strut is installed by using a ground improvement wall that is easy to dismantle and inexpensive depending on the need for later construction work. It's about doing.

The ultimate purpose of this invention is to excavate the ground at a location outside the retaining wall and close to the retaining wall to a required depth prior to the excavation process in the retaining and sill beam construction method, and
Accompanying the excavation, the process consists of forming a ground-improving earth wall, which is made by mixing the excavated existing site with a binder and fixing it, as a continuous underground wall that surrounds the entire circumference of the mountain. The objective is to provide a construction method to prevent subsidence of the surrounding ground.

Next, the present invention will be explained with reference to an embodiment shown in FIG.

Figure 2 is a diagram showing the implementation procedure of the surrounding ground subsidence prevention construction method according to the present invention, which was carried out when excavating soft ground using the mountain crab and strut method. The strut 3 that supports the retaining wall 1 is the surrounding ground (soft ground). In the figure, reference numeral 4 denotes a soil improvement wall formed outside the mountain crab wall 1 and close to the mountain retaining wall 1, for example, at a close position at a distance of about 50 skins to 100 skins (distance 1).

The soil improvement sandbags 4 are formed to reach a depth that is effective for preventing ground flow and slippage that would occur from the ground surface toward the excavation location deep in the ground. In other words, this soil improvement wall 4 is
Usually, it is formed much deeper than the retaining wall 1.
Moreover, this ground improvement earthen wall 4 is a mountain stop. Prior to the ground excavation process in the strut beam construction method, the retaining wall is formed continuously so as to surround the entire circumference of the wall, that is, as a continuous wall, and is made to function during the excavation process. This method of forming the ground improvement engineer 4 uses a grout pump and a rotary drilling machine such as an earth auger or a boring machine that is capable of injecting a chemical binder (grout). The ground where the wall 4 is to be formed is excavated to the required depth using a rotary boring machine, and the excavated site and a chemical binder such as water glass, cement, quicklime, or slaked lime are injected into it. The soil improvement wall 4 is formed by thoroughly mixing and solidifying the soil pile in the form of a slurry in the form of columns in close contact with each other. It is formed as an unreinforced improvement layer that has moderate rigidity and water-stopping properties by simply solidifying it with a chemical binder injected into it, and has a wall thickness W that is equal to the excavation width by the rotary excavator. The subsidence prevention method implemented as described above prevents landslides caused by excavation of the ground.
Water pressure etc. are all 1 on the pedestal wall as in the normal pedestal/cut beam construction method.
and supported by strut 2...

In other words, it is sufficient for the ground improvement wall 4 to have sufficient mechanical performance to transmit the soil and water pressure of the surrounding ground 3;
It is not required to have the rigidity and strength to support pressure and water pressure. On the other hand, as shown in Figure 2, after installing Gong Beams 2 and 2, excavation continues, and while the next lower strut shown by the two-dot chain line is being installed, there are The soil improvement wall 4 reliably prevents the flows and slips that would occur that are characteristic of soft ground due to its inherent rigidity and strength, which not only prevents the retaining wall 4 from deforming.
Prevent subsidence, deformation, etc. of the surrounding ground 3. Also, retaining wall 1
The ground improvement wall 4, which is continuously formed to surround the entire circumference of the excavated area, is effective in preventing the ground from flowing and sliding toward the excavated area because it surrounds the excavated area.
It also works effectively as a water-stop wall, dramatically reducing the burden required to treat groundwater at the excavation surface, and making excavation work much easier, such as by making dry excavation possible.

As explained above, the present invention, prior to the excavation process in the retaining and cutting beam construction method, excavates the ground at the location outside the mountain crab wall and close to the retaining wall to the required depth, and the process of forming a soil improvement wall, which is formed by mixing and solidifying the excavated existing soil and a binder, as an underground continuous wall that surrounds the entire circumference of the mountain retaining wall. The main purpose of this method is to prevent subsidence of the surrounding ground due to this, so it has the following effects.

First, prior to the excavation process in the mountain retaining and sill-beam construction method, the soil improvement wall formed on the outside of the retaining wall will move toward the excavated location as soft ground is excavated using the mountain crab and sill-beam construction method. It prevents the flow and slippage that is characteristic of soft ground, thereby reliably preventing subsidence and deformation of the surrounding ground, and preventing damage such as leaning of nearby buildings or damage to structures. It has the effect of preventing.

Second, the soil improvement wall, which is continuously formed to surround the entire circumference of the retaining wall, is effective in preventing the ground from flowing and sliding toward the excavated area, and is also effective as a water stop wall. This has the effect of significantly facilitating excavation on the excavated surface.

Second, the ground improvement wall is formed by excavating the ground, mixing the excavated existing material with a binder, and solidifying it as an unreinforced and low-rigid material. can be done cheaply, easily, and efficiently, and burying them does not pose a significant economic burden.

In addition, even if this is buried, if necessary later on, it can be easily dismantled and removed in the same way as excavating the ground with a regular excavator, and it does not cause any problems. .

[Brief explanation of the drawing]

Figure 1 is a vertical sectional view of the main part showing the implementation procedure of the conventional mountain retaining and sill beam construction method, and Figure 2 is a vertical sectional view of the main part showing the implementation procedure of the subsidence prevention construction method of the present invention using the mountain crab and sill construction method. FIG. 1... retaining wall, 2... cut beam, 3...
・Surrounding ground, 4... Ground improvement engineer wall, i...
··distance. Figure 1 Figure 2

Claims (1)

[Claims] 1. (a) Prior to the excavation process in the retaining and strut construction method, (b) excavating the ground in that area to the required depth at a location close to the retaining wall that was outside the retaining wall; and (d) forming a ground-improved soil wall by stirring and mixing the excavated existing soil and a binder and solidifying it as an underground continuous wall that surrounds the entire circumference of the mountain retaining wall. A process to prevent subsidence of the surrounding ground due to excavation.