JPH0517932A - Water permeable construction method for hole wall surface dug by using stabilizing liquid - Google Patents

Abstract

PURPOSE:To facilitate pumping from a dug hole by excavating the dug hole by using excavation stabilizing liquid, and adding a plant tissue breaking ferment, decreasing viscosity of muddy film stabilizing liquid formed in a wall surface, by a predetermined amount. CONSTITUTION:A retaining is executed in the periphery of a building constructing site to excavate an SMW wall 16. Liquid of stirring about 0.4pts. CMC and about 0.2 plant cellulose and high water absorbing resin adjusted relating to pure water is used as excavation stabilizing liquid to excavate a pumping hole 11 to about 16m depth. A steel pipe 12 and a pump 13 are set up in the pumping hole 11. Next, plant ferment of cellularb or the like for dissolving a water soluble high molecular viscosity increasing material is added to decrease viscosity of a stabilizing agent and to faciltate pumping work from an excavated surface.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a water permeation method for reducing the water permeation resistance of a mud film formed on the wall surface of a hole or trench excavated by using a stabilizing liquid for lowering the groundwater level at a construction site.

[0002]

2. Description of the Related Art In Japan, the annual rainfall is several times that of Europe and the United States, and the groundwater level of the ground is generally high. When excavating several meters in the plains, the groundwater level often occurs. It is well known that the ground is stabilized by lowering the groundwater level.Therefore, it is necessary to provide an open channel in the wetland to improve drainage, or to dig a hole underground to install a drainage pump in the hole. The method of installing and pumping groundwater is used.

In excavation earthworks below the groundwater level, a phenomenon called so-called boiling or quick sand occurs on the excavated surface in the direction of the groundwater streamline, which is a major cause of construction disasters. In order to prevent this, it is important to lower the groundwater level so that no seepage pressure is applied to the bottom and side of the excavation. The water level reduction method includes open channels,
There are underground water pipes, blind blinds, shallow well method, well point method, deep well method, vacuum method, etc. Among these methods, the deep well method has a diameter of 30 to 100 cm and a large depth of 10 m or more. Wells are often drilled. In this case, the stable liquid drilling method is generally used for drilling,
The stabilizing solution (also called muddy water) is a bentonite stabilizing solution prepared by suspending and dispersing bentonite in water, a solution containing a thickener and a dispersant, or sodium carboxymethyl cellulose (hereinafter referred to as CMC). Polymer stabilizers prepared by dissolving water-soluble thickeners such as in water in water, and those containing bentonite or clay in a few% are generally used. The function of these stabilizing liquids has been well understood.According to them, the stabilizing liquid acts on the excavation wall surface and forms a water-stopping mud film, which prevents peeling and collapse of the excavation surface. There is.

By the way, in the stable liquid excavation construction method such as underground wall construction and earth drill construction, in order to complete the construction method, the trenches and holes after the excavation are filled with concrete, and the water blocking wall and the structure are constructed. Is generally used as part of
If the muddy water film of the hole wall formed by the stable liquid used during excavation has good water permeability, the water-stopping effect will be poor, and the amount of the stable liquid that diffuses into the ground will increase, lowering the stable liquid level in the hole. Because
There is a fear of collapse of the hole wall. For this reason, until now, research on stable liquids for drilling has focused on how to prepare and secure stable liquids with low filtration and water permeability. At present, stabilizing liquids generally used are combined with stabilizing liquid materials for the purpose of sufficiently exerting the water blocking effect of the mud film.

[0005]

On the other hand, in order for the deep well method to function, it is necessary to pump up the groundwater that accumulates in the sandy layer of the excavation hole. Must flow in. However, when excavated using a conventional bentonite stabilizer or polymer stabilizer, which is focused on the preparation of a stable liquid with low filtration permeability, bentonite particles and clay particles form a solid and strong waterproofing mud film. The flow velocity of groundwater flowing through this mud film is small, and the economic burden such as the addition of wells is incurred in order to obtain the designed discharge volume.
As a method of ensuring the permeability of the excavated wall surface, it is possible to remove the mud film by a physical method such as a jet flow after excavation, but if the jet pressure is too high, the excavated wall surface will separate and the drill hole will collapse. There are problems such as danger.

Further, Japanese Patent Publication No. 48-28215 discloses that a microorganism or enzyme in soil or an auxiliary composition decomposes a stabilizing solution to reduce its viscosity.

However, before pumping is possible, 1
It takes about a week. In addition, although organic substance degrading bacteria are used as part of the stable liquid composition, the degrading activity of microorganisms depends on environmental conditions, that is, temperature, pH, etc. There is also the problem that it is difficult to control.

An object of the present invention is to provide a method for permeabilizing a stable liquid capable of promptly and reliably reducing the water permeation resistance of a mud film formed on an excavated wall surface after excavating with the stable liquid. The purpose is to do.

[0009]

The water permeable method of the present invention is
In the groundwater level lowering method, a hole or ditch is drilled using a stabilizing solution containing a water-soluble polymer thickener, plant fibers and a superabsorbent resin, and after the drilling the water-soluble polymer thickener is added to the stabilizing solution. It is characterized by adding an enzyme agent that decomposes to the stabilizing solution to reduce the permeability resistance of the mud film formed on the excavated wall surface and facilitate the movement of groundwater.

[0010]

EXAMPLES The stabilizing solution used in the water permeation method of the present invention is characterized by containing a water-soluble polymer thickener, vegetable fibers and a super absorbent polymer.

In general, the fine solids of bentonite and clay particles used in the bentonite stabilizer and polymer stabilizer easily pass through the gaps in the sand layer, which increases the bentonite concentration and the polymer concentration, and the stabilizer becomes viscous. There have been proposed a method of preventing the stable liquid from flowing out from the gap by resistance, a method of preventing the stable liquid from flowing out by adding an appropriate plugging material or the like. Conventional stabilizers are used in combination with bentonite and inorganic particles such as clay particles to make solid and strong waterproofing mud film, whereas the components of the stabilizer used in the water permeation method of the present invention are all organic. It is a substance that can be decomposed. The water blocking effect of the mud film formed by the stabilizing solution is as follows.

First, the gaps in the sandy layer are filled with vegetable fibers and the superabsorbent resin expanded to 300 to 500 times its own weight, and the gaps formed by these materials are smaller than the gaps in the sand layer. It is considered that the aqueous solution of the water-soluble polymer thickener is difficult to pass through this small gap due to viscous resistance, and the stable liquid as a whole is difficult to flow out through the excavation wall.

Specific examples of the water-soluble polymer thickener include CMC, guar gum, sodium hydroxyethyl cellulose (HEC), methyl cellulose (MC), xanthan gum, locust bean gum, poval, polyacrylamide, polyethylene oxide, polyacrylic acid. Examples thereof include sodium and glucomannan. Of these thickeners, C is preferred because it is easily decomposed by enzymes.
It is preferable to use MC, HEC, guar gum, xanthan gum, glucomannan, locust bean gum.

As the vegetable fiber, Avicel, cellulose, pulp, waste paper pulp or the like can be used. Among these plant fibers, it is preferable to use paper powder pulp made from old newspapers and magazines as a raw material in terms of shape, size, economy and the like. The size of the plant fiber is not particularly limited in the present invention, but a fiber having a diameter of 15 to 80 μm and a length of 600 to 1400 μm is usually used. The sawdust described in Japanese Examined Patent Publication No. 2-56475 is unsuitable as a clogging material for a stabilizing solution because the polymer solution is washed out when it is dehydrated with a pressure dehydrator after being mixed with the polymer solution. Is. As the super absorbent polymer, starch-based ones, acrylic-based ones, etc. are appropriately used.

The above-mentioned respective components are compounded in such a manner that the water-soluble polymer thickener is usually added in an amount of 0.1 to 1.0 part and plant fiber 1 to 100 parts of water.
5 parts, super absorbent polymer 0.1-0.5 parts, especially water 100
It is preferable that 0.3 to 0.5 parts of the water-soluble polymer thickener, 3 to 5 parts of vegetable fiber, and 0.3 to 0.5 part of the superabsorbent resin are used for each part from the viewpoint of enhancing the sludge-removing effect.

The stabilizing solution is prepared, for example, by adding a predetermined amount of a water-soluble polymer thickener to tap water and dissolving the mixture by stirring for about 24 hours with a stirrer such as a paddle type mixer. It can be performed by adding predetermined amounts of materials and mixing.

Next, the water permeation method of the present invention will be described.

The feature of the water permeation method of the present invention is that after the groove or hole is excavated by using the stabilizing solution described above, the enzyme agent for decomposing the water-soluble polymer thickener in the stabilizing solution is added to the stabilizing solution. It is characterized by being added to. Then, by adding such an enzyme agent, the viscosity of the stabilizing solution is lowered, the water permeation resistance of the mud film is reduced, and the water flow from the excavated wall surface of groundwater is facilitated.

As the enzyme agent, cellulase, glucomannase, galactomannase, hemicellulase and the like, which are plant tissue-disintegrating enzymes, can be used. The enzyme agent is added to the stabilizing solution in an amount of usually 0.05 to 2% (weight%, the same applies hereinafter), preferably 0.2 to 0.5%.

In addition to the above enzyme agent, CaCl ₂ ,
An inorganic salt such as MgCl ₂ or NaCl may be added to the stabilizing solution. By adding the inorganic salt, the superabsorbent resin extrudes water and shrinks, so that the mud film is not clogged, and the water permeability of the mud film is further enhanced. The amount of the inorganic salt added varies depending on the type and blending ratio of the super absorbent polymer in the stabilizing solution and the type of the inorganic salt, but is usually 0.5 to 3% based on the stabilizing solution.

According to the water permeable method of the present invention, the water permeability is improved only 0.5 to 6 hours after the addition of the enzyme agent.
When the water permeability effect is expected for a long period of time, the plant fibers in the stabilizing solution are gradually decomposed by the bacteria in the soil, and accordingly the water permeability is further improved.

Next, the water permeation method of the present invention will be described based on experimental examples and examples.

[0023] filled with silica sand of grain size shown in FIG. 2 vertical seen sand layer at the bottom of the transparent test column shown in Experimental Example Figure 1, gently flowing stabilizer thereon, the 3 kgf / cm ² After pressurizing with pressure, the amount of filtrate flowing out from the bottom outlet was measured, and a stable solution with a smaller amount of filtered water was regarded as a better stable solution, and the filtration water permeability of the stable solution was examined.
The results are shown in Fig. 3.

In FIG. 1, 1 is a transparent resin cylinder, 2 is a stabilizing liquid, 3 is silica sand, 4 is pressurized air, 5 and 6
Is a gate valve, and 7 is a safety valve.

For the preparation of the stabilizing solution, a predetermined amount of CMC was added to tap water, and the mixture was stirred for 24 hours with a paddle mixer to dissolve, and predetermined amounts of each component material were added and mixed therein. Table 1 shows the blending amount of the stabilizing solution.

[0026]

[Table 1]

Formulation I (100 parts water, 5 parts newspaper pulp (hereinafter referred to as CP)) and II (100 parts water, CMC0.
4 parts) of the stabilizing solution immediately flowed out of the sand layer, and no water-stopping effect was observed, but compounding formulation III (water 100 parts, CMC0.
4 parts, CP1 part) and IV (100 parts water, 0.4 parts CMC,
A stable solution of CP3 part) has a large initial outflow, but a water-stopping effect is recognized, and V (water 100 parts, which is combined with sodium polyacrylate crosslinked product (hereinafter referred to as WAP))
CMC0.4 part, CP1 part, WAP0.1 part) and VI (water
It was revealed that the stabilizing solution of 100 parts, CMC 0.4 part, CP3 part, WAP 0.1 part) further reduced the amount of filtrate and functioned as a stabilizing solution. That is, as the component composition of the stabilizing solution,
Using water, CMC, CP and water, CMC, CP, WAP, it was found that the stable liquid obtained by the combination of these has a low filtration water permeability and can be used as a stable liquid for drilling.

Next, an enzyme or salt was added to this stabilizing solution to make the mud membrane permeable. The experimental method was as follows: When the stabilizers of III to VI were filled in the tester of Fig. 1 respectively and pressurized at a pressure of 3 kgf / cm2, a mud film was formed in the sand layer and the drainage rate of the drainage became sufficiently small ( Pressurization time is 15 minutes), pressurization is stopped temporarily, and the stable amount of the solution that has been filtered out is replenished, then the enzyme amount (E) is added to 0.5%, and the solution is gently stirred and again Pressurization was started. When pressurization start time is set to 0 hour and the amount of filtrate is measured every pressurization time, the result of Fig. 4 is obtained. When enzyme is added, the amount of filtrate is increased in a short time and the permeation resistance of the mud membrane is , Significantly reduced and improved. On the other hand, in the case of VI without addition of enzyme, the amount of drainage was not significantly increased over time.

CaCl ₂ or NaCl instead of oxygen
Fig. 5 shows the result of examining the water permeability of the mud membrane by adding the above.
The experimental method is as described above, but the rate of increase in the amount of filtered water was smaller than that in the oxygen addition method, but CaCl ₂ , Na
The water permeability of the mud film was slightly better than when Cl was not added. Further, an experiment was also conducted for the case where 0.5% of the enzyme and 3% of CaCl ₂ were added together, and similarly good results were obtained.

From the above results, the stabilizing solution used in the water permeation method of the present invention sufficiently exhibits the function as a stabilizing solution for excavation, and an enzyme agent or an inorganic material such as CaCl ₂ is used for the water permeation of a mud film. Obviously, this can be achieved by adding salts.

Next, examples of the present invention will be described.

Example A geological survey of the ground was carried out during the building construction work. As a result, the groundwater level was high, and it was feared that spring water and boiling would occur during the excavation of the basement.
Therefore, in order to carry out the construction safely, it was decided to adopt the groundwater level lowering method. Since it was determined that it was difficult to sufficiently lower the groundwater level with the conventional deep well using the drilling fluid, a large diameter deep well using the water permeation method of the present invention was planned and implemented. The outline will be described with reference to the drawings.

First, SMW (Soil M
ixing Wall) was used to carry out earth retention of 24 m underground and planned 4 deep wells on the site (see Figures 6 to 7).
In FIGS. 6-7, 16 represents the SMW wall. As the drilling fluid, 0.4 parts of CMC, 3 parts of vegetable fiber (newspaper pulp) and 0.2 part of superabsorbent resin (crosslinked sodium polyacrylate) were added to 100 parts of fresh water, and the mixture was prepared by stirring. The pumping hole 11 with a diameter of 1000 mm was drilled with a drill excavator to a depth of 16 m. A 500 mm perforated steel pipe 12 was installed in the excavated pumping hole, and a pumping pump 13 was installed in it.
Set. Gravel 14 was filled around it. In order to bring the enzyme and CaCl ₂ into contact with the mud film, the stabilizing solution in the hole was circulated through the water tank 15 together with the enzyme and CaCl ₂ . After left overnight, pumping was started, and in 6 hours the groundwater level was successfully lowered to 13 m or below the root cutting point, and the construction was completed.

[0034]

As described above, according to the stabilizing solution used in the water permeation method of the present invention, the gap such as the sand layer becomes smaller due to the filter composed of the plant fiber and the super absorbent resin. The stable liquid thickened by the thickener is less likely to pass through water, which reduces the amount of dehydration.

Further, in the water permeation method of the present invention, the water-soluble polymer thickener in the stabilizing solution is decomposed by the enzyme, so that the viscosity of the stabilizing solution is lowered and the water permeability of the mud membrane is improved. Further, when an inorganic salt such as CaCl ₂ is added to the stabilizing solution, the highly water-absorbent resin extrudes water and contracts due to polyvalent ions of the inorganic salt, so that the clogging effect is lost and the water permeability is further improved. .

[Brief description of drawings]

FIG. 1 is an explanatory view of an experimental device for demonstrating the water permeation method of the present invention on sand ground.

FIG. 2 is an explanatory diagram of particle size distribution of silica sand packed in the experimental apparatus shown in FIG.

FIG. 3 is a diagram showing an effect as a stabilizing solution.

FIG. 4 is a diagram showing a water permeation effect by the water permeation method of the present invention.

FIG. 5 is a diagram showing a water permeation effect when an inorganic salt is added.

FIG. 6 is a schematic plan view of a large diameter deep well method performed as an example.

FIG. 7 is a schematic cross-sectional explanatory view of a large-diameter deep well method performed as an example.

[Explanation of symbols]

2 Stabilizer 3 silica sand 11 Pumping hole 12 perforated steel pipe 13 Pumping pump 14 gravel 15 aquarium

Claims (2)

[Claims] 1. In the groundwater level lowering method, a stabilizing solution containing a water-soluble polymer thickener, plant fibers and a superabsorbent resin is used to excavate a hole or groove, and after the excavation, the stabilizing solution is highly soluble in water. A water permeation method characterized by adding an enzyme agent that decomposes a molecular thickener to reduce the permeation resistance of the mud film formed on the excavated wall surface and facilitate the movement of groundwater. 2. The method according to claim 1, wherein an inorganic salt is further added to the stabilizing solution.