JPH0696940B2 - Viscosity-imparting material for earth pressure type shield construction method and earth pressure type shield construction method - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a shield construction method for excavating a tunnel or the like, and in particular, a viscosity for earth pressure type shield construction method suitable for excavating the soil quality of a sand layer or a gravel layer. The application material and earth pressure type shield construction method.

[Conventional technology]

The earth pressure type shield construction method generates pressure in the excavated earth and sand in the cutter chamber that can counteract the earth pressure of the cutting face, the water pressure of the groundwater, and the amount of water, and stabilizes the cutting face, preventing groundwater from seeping out and blocking the inside of the cutter chamber. While digging in. When the soil is a sand layer or a gravel layer, the friction resistance of the soil is large and the water permeability is large, so that the excavated sand has insufficient fluidity and it is difficult to prevent the outflow of groundwater. From the, to the excavated earth and sand in the cutter chamber, for example, an additive material that imparts viscosity consisting of bentonite and porcelain clay is injected and forcedly kneaded to improve the soil properties so that the excavated earth and sand have plastic fluidity, and the excavated earth and sand The water permeability is reduced and the digging is carried out.

[Problems to be Solved by the Invention]

However, the conventional additive material is, for example, bentonite and porcelain clay mixed in a weight ratio of 1: 1 and kneaded with water to have a predetermined viscosity, and the water pressure exceeds ² kg / cm ² in a high-pressure ground. In places with a lot of spring water and a homogeneous fine sand layer in the gravel layer ground, even if the additive material is injected into the excavated earth and sand in the cutter chamber, the excavated earth and sand and the additive material are easily separated due to the abundant groundwater. However, the additive was diluted and the viscosity of the whole excavated soil could not be increased. Therefore, the excavated earth and sand as a soil pressure transmitting medium with a stable face cannot be sufficiently mudized, and the excavated earth and sand cannot be provided with a force that resists the seepage water pressure and the amount of the seepage water. Therefore, not only is the cutting face unstable and jetting of groundwater occurs, the cutting face cannot be stabilized, but the abrasion delay effect is not exhibited in the sand layer where the wear of the cutter bit is a problem, and the abrasion is accelerated. Moreover, if the amount of the additive material injected is increased in order to increase the viscosity of the excavated soil and enhance the water-suppressing effect, a large amount of jetting will occur when the soil is discharged by the screw conveyor. If the ratio of bentonite to the clay is increased to increase the viscosity of the additive material in order to prevent the additive material from being diluted with groundwater, etc., the cost becomes significantly high. Moreover, because the equipment for making additive material is large, it is installed on the ground, and the additive material is pumped through the injection pipe to the underground excavation site, so that the additive material has a viscous resistance inside the injection pipe. This makes it difficult to inject into the cutter chamber. In addition, in order to absorb groundwater contained in excavated soil and prevent spouting, if a water reducing agent such as a polymer water supply agent is added and injected into the additive material, a dehydration phenomenon occurs in the injection pipe, and the additive material is kept stationary. Can no longer be pumped.

The present invention has been made in order to solve the above-mentioned drawbacks of the prior art, and a viscosity imparting material for an earth pressure type shield construction method capable of increasing the viscosity of excavated soil in the cutter chamber, and the viscosity imparting material in the cutter chamber. It is an object of the present invention to provide an earth pressure type shield construction method capable of surely pouring.

[Means and Actions for Solving the Problems]

In order to achieve the above object, the earth pressure type shield construction method viscosity imparting material according to the present invention is an earth pressure type shield construction method viscosity imparting material to be injected into excavated earth and sand in a cutter chamber, and a calcium compound is added to a sludge containing bentonite. It is characterized by having done.

The sludge containing bentonite can be obtained, for example, by mixing bentonite and porcelain clay in a weight ratio of 1: 1 with water and kneading the mixture. And as bentonite,
For example, those produced in Gunma prefecture having a composition of SiO ₂ 64 to 68% Al ₂ O ₃ 13% Fe ₂ O ₃ 3% Na ₂ O 1.5% and 14.5 to 18.5% by weight can be used. As the clay, for example, one having a composition of SiO ₂ 68.8% Al ₂ O ₂ 16.6% Fe ₂ O ₃ 1.7% CaO 0.7% MgO 0.8% and 11.4% by weight can be used. The mixing ratio of bentonite and porcelain clay can be arbitrarily changed depending on the soil condition, for example, porcelain clay 2 or porcelain clay 3 with respect to bentonite 1 by weight.

The ratio of the mixture of bentonite and porcelain clay (hereinafter, also simply referred to as a mixture) to water is about 0.5 to 1.2 with respect to 1 part by weight of water, and the viscosity of the sludge is desirably.
Mixture 0.6 to 1 water to obtain 2000 to 4000 cP
0.9 so that it can be easily pumped with an existing pump. When the amount of the mixture is 0.5 or less, the effect of improving the viscosity of the calcium mixture described later is small, and the mixture is diluted by spring water, so that the excavated earth and sand cannot be sufficiently provided with the water suppressing effect and the plastic fluidity. Further, if the amount of the mixture exceeds 1.2, not only the effect of adding the calcium compound is not obtained, but also it becomes difficult to pump the mixture. After mixing a predetermined amount of water into Misaki, this slurry is kneaded by sequentially adding bentonite and porcelain clay while stirring with a stirrer.

As the calcium compound, calcium hydroxide (slaked lime), calcium oxide (quick lime), calcium chloride or the like can be used, but calcium hydroxide is suitable. Calcium hydroxide is suspended in water and added to a sludge containing bentonite, clay and water. It is considered that the calcium hydroxide added to the sludge reacts with bentonite, SiO _{2 in} the clay and Na ₂ O in the bentonite as follows, and the bentonite aggregates to increase the viscosity of the sludge.

SiO ₂ + Na ₂ O + Ca (OH) ₂ → CaSiO ₃ + 2NaOH The amount of calcium hydroxide added to the slurry depends on the ratio of bentonite and porcelain clay to water and the ratio of bentonite and porcelain clay. ~ 0.3%
If the added amount of calcium hydroxide is less than 0.15%,
It is difficult to improve the viscosity of the slurry, and when the viscosity imparting material is injected into the excavated soil, it may be diluted by groundwater. Also, the amount of calcium hydroxide added is 0.3
If it exceeds%, the reaction between the sludge and calcium hydroxide will proceed, and the viscosity of the viscosity-imparting material may become too large, making it difficult to inject it into the excavated soil. Then, when the concentration of the mixture in water is low, the ratio of calcium hydroxide to be added is increased, and when the concentration of the mixture in water is high, the ratio of calcium hydroxide to be added is lowered. Desirably, the slurry has a concentration of 60% (mixture with respect to 1 weight of water)
When the concentration is in the range of 0.6) to 120% (mixture 1.2 to water 1), the amount of calcium hydroxide added is 0.25 to 0.2% by weight of the slurry. At this time, the ratio of calcium hydroxide to bentonite is about 1.3 to 0.75 by weight.
%. This is based on the fact that the mixture of bentonite and porcelain itself has the effect of increasing the plastic flowability of excavated soil.

The amount of calcium hydroxide suspended in water is preferably in the range of 1 to 5% by weight of water.
The concentration of the calcium hydroxide suspension added to the 4000 cP mixture is preferably about 3%. Calcium hydroxide may be added to the slurry immediately before the viscosity imparting material is injected into the excavated soil. If calcium hydroxide is added to the slurry too soon, the viscosity of the slurry will increase during pumping, making it difficult to inject it into the excavated soil.

To make it easier to inject the viscosity-imparting material into the excavated soil,
The earth pressure type shield construction method according to the present invention is an earth pressure type shield construction method in which excavation earth and sand in a cutter chamber is advanced while injecting a viscosity-imparting material, in an underground excavation site, just before injecting into the excavation earth and sand, bentonite is contained in the bentonite. It is characterized in that a coagulant for coagulating is added to produce a high-viscosity viscosity-imparting material, and the high-viscosity viscosity-imparting material is injected into the excavated earth and sand while excavating.

As the sludge containing bentonite, for example, the above-mentioned bentonite and porcelain clay may be mixed at a weight ratio of 1: 1 and the mixture may be kneaded with water. Since this sludge is used in a large amount, it is preferable to prepare it on the ground and pump it to the step of adding a flocculant such as calcium hydroxide that flocculates bentonite. Then, the step of injecting the coagulant into the sludge to form the viscosity imparting material may be performed immediately before supplying the viscosity imparting material to the shield excavator. When a coagulant is added to the sludge on the ground and supplied to the shield excavator, the sludge and the coagulant react with each other due to the long transportation path, and the viscosity of the viscosity imparting material increases, so the pump capacity must be increased. In addition, the transportation pipe is often blocked, and it is often impossible to inject and mix the excavated sediment in the cutter chamber.

The flocculant such as calcium hydroxide is added to the slurry by dissolving the flocculant in water, thoroughly stirring both to uniformly mix them, and then pouring them into the excavated earth and sand in the cutter chamber with a pump.

As the coagulant, in addition to calcium hydroxide, an inorganic coagulant such as a sulfuric acid band, polyaluminum chloride, calcium chloride, ferric sulfate, a polyacrylamide partial hydrolyzate, and an anionic coagulant such as sodium polyacrylate. A cationic polymer flocculant such as an organic polymer flocculant, polyethyleneimine, a polyacrylamide cationic variant, or a nonionic polymer flocculant such as polyacrylamide or polyethylene oxide can be used.

〔Example〕

Preferred examples of the viscosity imparting material for the earth pressure type shield construction method and the earth pressure type shield construction method according to the present invention will be described in detail below.

A mixture of bentonite and porcelain clay having the above-mentioned composition in a weight ratio of 1: 1 is prepared, 500 g of water is added to this mixture and stirred well to obtain various concentrations of sludge, and then water is mixed in a weight ratio of about 1: 1. 3% suspended calcium hydroxide was added to each sludge, and the mixture was stirred for about 5 minutes to obtain a high-viscosity viscosity-imparting material. The viscosity of this high-viscosity viscosity-imparting material was the viscosity of the sludge before adding calcium hydroxide. Compared with. The results are shown in Table 1. A C-type viscometer was used to measure the viscosity.

As is clear from Table 1, the viscosity-imparting materials of the examples have remarkably improved viscosity as compared with the slurry before adding calcium hydroxide. That is, even if the amount of expensive bentonite and porcelain used is the same as the conventional amount, the viscosity of the additive to be injected into the excavated soil can be significantly improved by adding a small amount of inexpensive calcium hydroxide, and By increasing the plastic flowability and suppressing the dilution of the viscosity-imparting material by groundwater, it is possible to stabilize the face and reduce the occurrence of jetting.

FIG. 1 is an explanatory view showing an example of an apparatus for carrying out the earth pressure type shield construction method according to the present invention.

In FIG. 1, the clay and bentonite in the clay silo 10 and bentonite silo 12 provided on the ground are mixed through pipes 18 and 20 equipped with measuring devices 14 and 16, respectively, to a mixer 22,
It is thrown into 24. Below the mixers 22 and 24, a mud storage tank 26 with a stirrer is arranged. A water supply pipe 28 is connected to the mixers 22 and 24, and a flow meter 32 and a valve are connected to the water supply pipe 26.
34 are provided so that the amount of water supplied to the mixers 22 and 24 can be adjusted. On the other hand, a pipe 30 is connected to the mud storage tank 26 with a stirrer, and the tip of the pipe 30 is connected to the suction side of the pressure pump 36.

A transport pipe 38 is connected to the discharge side of the pressure pump 36.
The tip side of the transport pipe 38 extends into the horizontal shaft 42 through the vertical shaft 40, is provided with a solenoid valve 43, and is connected to an agitation / injection device 44 provided in an underground excavation site. . Further, the stirring / injecting device 44 is provided with a tip end portion of a pipe 48 having the other end connected to the stirring / storage tank 46, and an injection pipe 50 is connected thereto. The stirring / storage tank 46 has a flow meter.
A water supply pipe 56 having a valve 52 and a valve 54 is connected to supply water for obtaining a suspension of calcium hydroxide (slaked lime) 58.

On the other hand, the tip of the injection pipe 50 is connected to the shield excavator 60 so that the high-viscosity viscosity imparting material manufactured by the stirring / injecting device 44 can be injected into the cutter chamber. The shield excavator 60 is an ordinary excavator used in the earth pressure type shield construction method, and includes a screw conveyor 62 for carrying out excavated soil. A branch pipe 64 of the injection pipe 50 having a valve is connected to the screw conveyor 62 so that the viscosity imparting material can be injected also from the branch pipe 64.

The stirring / injecting device 44 has a stirring tank 66 as shown in FIG.
A tip end of a pipe 48 having a large number of supply holes extends above the stirring tank 66, and an ultrasonic level switch 67 is provided above it. And, in the lower part of the stirring tank 66,
A stirring screw 68 is provided. Stirring screw 68
Is driven by a chain by a motor 70, and mixes the slurry supplied to the stirring tank 66 and the suspension of calcium hydroxide. Further, the motor 70 drives an injection pump 72 provided below the stirring tank 66. The injection pump 72 is connected to the injection pipe 50 having the electromagnetic flow meter 74. further,
The injection pipe 50 is provided with a valve 76 and a return pipe 78.

The stirrer / injection device 44 configured as described above is used in the moving carriage 80
It is installed in. Wheels 82 are attached to the movable carriage 80,
A control device including a drive motor 84 and a control panel 86 is provided.

As shown in FIG. 3, the agitation / storage tank 46 is mounted on a trolley 90, an agitator 92 is provided inside, and a feed pump 94 is provided below. The dolly 90 is a coupler 96.
Is attached, and is connected to the moving carriage 80 and towed by the moving carriage 80.

An example of the earth pressure type shield construction method using the apparatus configured as described above is as follows.

After injecting 769 kg of water into the mixers 22 and 24 via the water supply pipe 28, 269 kg of bentonite in the bentonite silo 12 is weighed by the measuring device 16, and the mixture is put into the mixers 22 and 24 and stirred, and the clay silo 10 is added. 269 kg of porcelain clay in the inside is weighed by the weighing device 14, put into the mixers 22 and 24, and stirred. And
The clay and the bentonite are sufficiently mixed by the mixers 22 and 24 to form a 70% concentration sludge composed of bentonite, the clay and water, and the mud is stored in the mud storage tank 26 with the agitator 26. The sludge in the mud storage tank 26 with a stirrer is sucked by a pressure pump 36 through a pipe 30, and is pressure-fed through a transport pipe 38 to a stirring tank 66 of a stirring / injecting device 44 provided at an underground excavation site. The viscosity of this slurry is approximately 2000-4000 cP.

On the other hand, 3 g of calcium hydroxide is added to 100 cc of water in the stirring / storage tank 46 and stirred by a stirrer 92 to make a suspension of calcium hydroxide having a concentration of 3%. This suspension is supplied to the stirring tank 66 of the stirring / injecting device 44 via the pipe 48 by the feed pump 94. The slurry supplied to the agitation / injection device 44 and the suspension of calcium hydroxide 58 is mixed with the agitation screw 68.
To obtain a uniform viscosity-imparting material. The supply amount of the suspension of calcium hydroxide is such that the viscosity of the viscosity imparting material becomes about 15000 cP.

The viscosity imparting material obtained by the agitation / injection device 44 is injected into the excavated earth and sand in the cutter chamber of the shield excavator 60 which is being excavated by the injection pump 72 through the injection pipe 50. The injection conditions of the viscosity imparting material are as follows: injection pressure 4 to 15 kg / cm ² , flow rate 5 to 50 l /
min, the amount of calcium hydroxide used in the slurry is 2.5-3.
It was set to 0 kg / m ³ .

Thus, according to the earth pressure type shield construction method of the embodiment, just before injecting into the cutter chamber at the underground excavation site, the slurry and calcium hydroxide are mixed to manufacture and inject the viscosity imparting material. Therefore, the viscosity imparting material having high viscosity can be easily injected into the excavated earth and sand in the cutter chamber. As a result, compared with the conventional injection of additive material consisting of bentonite and porcelain clay, it is possible to enhance the plastic flowability of excavated soil without being diluted by groundwater, to stabilize the cutting face, It was possible to remarkably improve the effect of improving the emission prevention.

In addition, in the case of a device used in the conventional earth pressure type shield construction method, the viscosity range of the viscosity imparting material to be injected may be adjusted to 7,000 to 20000 cP in consideration of the capacity of the pump.

〔The invention's effect〕

As described above, according to the viscosity imparting material of the present invention, it is not diluted by groundwater, the plastic flowability of excavated soil is enhanced, and the occurrence of jetting can be reduced. Further, according to the earth pressure type shield construction method according to the present invention,
It is possible to easily inject a highly viscous material into the excavated earth and sand in the cutter chamber.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an explanatory view of an apparatus for carrying out the earth pressure type shield construction method according to the present invention, FIG. 2 is an explanatory view of a stirring / injecting apparatus of the apparatus shown in FIG. 1, and FIG. FIG. 3 is an explanatory view of a stirring / storage tank of the apparatus shown in FIG. 10 …… Ceramic clay silo, 12 …… Bentonite silo, 22, 24
…… Mixer, 26 …… Muddy storage tank with stirrer, 36 …… Pressure pump, 44 …… Stirring / injecting device, 46 …… Stirring / storage tank, 58 …… Calcium hydroxide, 60 …… Shield excavator,
62 …… Screw conveyor, 68 …… Stirring screw, 72
…… Injection pump, 92 …… Agitator, 94 …… Feed pump.

Claims (2)

[Claims] 1. The earth pressure shield construction method, characterized in that 0.15 to 0.3% by weight of a calcium compound is added to sludge containing bentonite in a viscosity imparting material for earth pressure shield construction method to be injected into excavated earth and sand in a cutter chamber. Viscosity imparting material. 2. In an earth pressure type shield construction method for advancing while injecting a viscosity imparting material into excavated earth and sand in a cutter chamber, a sludge containing bentonite is prepared on the ground and is applied to the excavation tip through a shield starting shaft. A high-viscosity imparting material was manufactured by adding a flocculant consisting of 0.15 to 0.3% by weight of a calcium compound to the sludge delivered and delivered at the rear part of the shield excavator. An earth pressure type shield construction method characterized by excavating while pouring into excavated soil.