JPH0344196B2 - - Google Patents

Description

[Detailed description of the invention]

(Technical Field) The present invention relates to a shield type tunnel excavation method, and particularly to a pressure chamber or This invention relates to a shield type tunnel excavation method that excavates the face ground by injecting air bubbles into the face surface. (Prior Art) In the conventional shield type tunnel excavation method in which air bubbles are injected into the pressure chamber or the face in front of the bulkhead of the shield body, the air bubbles are sufficiently mixed with the shear excavated by the rotary cutter in the pressure chamber, and this By being held in the shear in a dispersed state, the shear is given a predetermined fluidity and water-stopping property. By the way, when excavating the ground where the ratio of gravel weight per unit weight is large, the ratio of gravel weight in the shear in the pressure chamber increases, and the porosity of the shear in the pressure chamber increases. Therefore, when excavating ground with a large proportion of gravel weight, even if the amount of air bubbles supplied to the shear is increased and the effect of stirring the shear by the rotary cutter is increased, the supplied air bubbles will not separate from the shear. Therefore, the air bubbles cannot be held in the pressure chamber, and the desired effect cannot be achieved by supplying the air bubbles. (Objective) Therefore, the object of the present invention is to prevent separation of shear in the pressure chamber and air bubbles mixed with the shear even when excavating a tunnel in ground with a large proportion of gravel weight, and to provide the shear with appropriate fluidity. Another object of the present invention is to provide a shield type tunnel excavation method that enables suitable tunnel excavation by providing water-stop properties. (Structure and Effects) The present invention basically provides a pressure chamber or face surface in front of the bulkhead of the shield body in order to reduce the excavation resistance against the rotary cutter in the excavated ground or to provide fluidity and water stoppage to shear. A shield type excavation method in which air bubbles are injected, characterized in that fine grain material is supplied to the pressure chamber. According to the present invention, the fine grain material supplied to the pressure chamber reduces the gravel weight ratio of the shear in the pressure chamber, thereby reducing the porosity of the shear, and the air bubbles mixed with the shear. Since the separation from the shear is suppressed, the air bubbles are reliably retained in the shear, and therefore, even if the ground has a high gravel ratio, the predetermined effect of the air bubble supply can be exerted. This enables suitable tunnel excavation. The fine-grained material can be supplied to the pressure chamber using the air bubbles injected into the face surface or the pressure chamber as a transport medium, but generally the amount of the air bubbles is smaller than the amount of air bubbles supplied. Since the supply amount of the fine granule material is extremely small, and the control factors for the bubbles and the supply amount of the fine granule material do not match, the above-mentioned It is preferable to supply the fine granule material at the same time as the supply of the bubbles. The fine-grained material can be supplied to the pressure chamber using a liquid or a gas as a transport medium, and the fine-grained material can be forced into the pressure chamber by mechanical pressure; In order to supply the material continuously and smoothly, it is preferable to supply the fine-grained material to the pressure chamber in a mixed state with a liquid such as water. By mixing a solution containing bubbles, for example, an aqueous foaming agent solution, and the fine particulate material and supplying the mixture to the pressure chamber, the mixture containing the fine particulate material is smoothly supplied to the pressure chamber in a relatively low water content state. can be supplied to When the fine granular material is supplied to the pressurizing chamber in a state with a high water content ratio, in addition to reducing the efficiency of supplying the fine granular material to the pressurizing chamber, the fine granular material mixed with the fine granular material Since the moisture content of the shear increases, it becomes necessary to subject the shear discharged from the pressurizing chamber to a secondary treatment such as drying treatment. However, by mixing the fine particulate material with a foaming agent solution containing foam as described above, it becomes possible to supply the fine particulate material to the pressurizing chamber with a relatively low water content.
This not only makes it possible to efficiently supply the fine grain material to the pressurizing chamber, but also eliminates the need for secondary treatment of shear discharged from the pressurizing chamber. By supplying the fine particulate material to the pressurizing chamber in a mixed state with an aqueous solution of a foaming agent and a thickener,
It becomes possible to supply the fine particulate material to the pressurizing chamber with a lower moisture content. Further, in order to prevent the sludge discharged from the pressure chamber from turning into sludge and to facilitate the handling of the discharged sludge, it is preferable to use fine sand as the fine grain material. (Example) The features of the present invention will become clearer from the following description of an illustrative embodiment showing an example of a device for carrying out the method of the present invention. The so-called earth pressure balance type shield type tunnel excavation method 10 shown in FIG.
A jack 16 is provided at the rear of the shield body 12 to propel the shield body 12 by applying a reaction force to the segments 14, and a jack 16 is provided at the front to support a rotary cutter head 18 and to apply pressure in the shield body 12 in the front pressurized area. A partition wall 24 is provided to partition a chamber 20 and an atmospheric region 22 to be described later. The cutter head 18 is provided with a bubble supply path 26 that opens into the pressure chamber 20 on the back side of the cutter face via its rotating shaft 18a. The bubble supply path 26 includes a bubble supply pipe 3 extending from the foamer 28.
0 is connected, and the foaming agent solution sent to the foaming device 28 via the foaming agent solution supply pipe 32 is supplied to the foaming device 28.
The foam is subjected to a foaming process at , and is injected into the pressure chamber 20 via the foam supply pipe 30 and the foam supply path 26 . The cutter head 18 is rotated by the operation of a drive device 38 connected to the rotating shaft 18a via a gear 34 provided on the rotating shaft 18a and a pinion 36 meshing with the gear. A stirring blade 40 is provided on the back surface of the cutter head 18 to promote mixing of the shear and the bubbles by the rotation of the cutter head 18, and in the illustrated example, the bubble supply path 26
is opened to the pressure chamber 20 by the stirring blade. An opening of the bubble supply channel 26 can be provided in the front surface of the cutter head 16 in order to inject the bubbles fed through the bubble supply channel 26 into the face surface. In addition, the foamer 28 is used to increase the strength of the bubbles.
A thickener can be added to the foaming agent solution supplied to the foaming agent solution. When excavating ground where the ratio of gravel weight in the ground to be excavated is relatively low, when the air bubbles injected into the pressure chamber 20 or the face are mixed with shear in the pressure chamber, the air bubbles are dispersed into the shear. It is held in this state without being separated from the shear.
Therefore, it is possible to give the shear in the pressure chamber 20 a predetermined fluidity and watertightness, and it is also possible to reduce the digging resistance of the cutter head 18, thereby maintaining the pressure in the pressure chamber 20 appropriately. , it is possible to prevent the collapse of the face and perform excavation in a suitable manner. The shear mixed with the air bubbles in the pressure chamber 20 is
For example, by operating a screw conveyor 44 having a drive device 42 that is operated in accordance with the excavation of the excavation device 10, the screw can be opened to the atmospheric region 22 without causing a pressure drop in the pressure chamber 20. They are sequentially discharged from the discharge port 46 of the conveyor. By the way, when excavating a tunnel in ground where the ratio of gravel weight exceeds 80%, for example, the amount of air bubbles supplied to the pressure chamber 20 is increased in order to mix with the shear of the pressure chamber 20, and the inside of the pressure chamber 20 is increased. Even if sufficient agitation is given to the shear, the porosity of the shear increases, and the volume of each void defined between the gravels in the shear in the pressure chamber 20 becomes large. Bubbles tend to separate from the pressure chamber 20, and most of the bubbles stay in the upper part of the pressure chamber 20, making it impossible to achieve the desired effect by supplying the bubbles. Therefore, in the present invention, fine grain material is supplied to the pressure chamber 20 in order to reduce the weight ratio of gravel in the shear inside the pressure chamber 20. In the illustrated example, the means for supplying fine granules into the pressure chamber 20 is from a stirring tank 48 for mixing the fine granules and, for example, a foaming material solution, through each wall 24 and into the pressure chamber 20. An elongated fine-grain material supply pipe 50 is provided. The supply pipe 50 is provided with pressure for feeding the mixture of the foaming agent solution and the fine particulate material, which have been partially foamed in the tank 48, into the pressure chamber 20 through the supply pipe 50. A pump 52 is provided. The fine particulate material supplied to the pressure chamber 20 in a state mixed with the foaming agent solution containing foam, that is, the foaming agent solution that is at least partially foamed, is By mixing, the weight ratio of gravel in the shear in the pressure chamber 20 is reduced, and the porosity of the shear is reduced. In other words, the fine-grained material mixed in the shear partially fills the voids between the gravels in the shear, reducing the volume of each void defined between the gravels, thereby reducing the amount of space between the sand components of the shear. The foam is ensured to be retained in each gap between the gravels as well as in the defined gaps. Therefore, when the bubbles supplied to the pressure chamber 20 via the bubble supply path 26 are mixed with the shear in the pressure chamber, they are not easily separated from the shear and are retained in the shear. Even if the ground has a high proportion of gravel, the predetermined effect of the air bubble supply can be exerted, thereby allowing suitable tunnel excavation. The supply amount of the mixture of the fine grain material and the foaming agent solution is determined by measuring the weight of gravel per unit weight of the ground to be excavated in advance, or by determining the amount of shear discharged from the pressure chamber 20 or the rotational torque of the cutter head 18. Based on the observation, the gravel weight ratio of the shear is appropriately selected depending on the advancing speed of the excavation device 10, for example, to be about 75%. The fine-grained material can be press-fitted alone, for example mechanically, into the pressure chamber, and gas can be used as a transport medium for the fine-grained material, but it is also possible to feed the fine-grained material continuously through a conduit. In addition, in order to supply the fine particles smoothly, the fine particles are mixed with the liquid in the pressure chamber 2.
It is preferable to supply it to 0. A liquid such as water may be used as the liquid, and the fine particle material may be mixed with this liquid and supplied to the pressure chamber. However, in this case, it is necessary to supply fine grain material smoothly and continuously.
The amount of water relative to the fine grain material increases, and the water content ratio in the mixture of water and fine grain material supplied to the pressure chamber 20 increases.
The value exceeds 230%. Such an increase in the water content ratio not only causes a decrease in the efficiency of supplying the fine granule material to the pressure chamber 20, but also causes an increase in the moisture content of the shear mixed with the fine granule material within the pressure chamber 20. As a result, it becomes necessary to subject the sludge discharged from the pressure chamber 20 to a secondary treatment such as drying treatment. In order to eliminate the need for such secondary treatment and to improve the supply efficiency of the fine grain material, it is preferable to supply the mixture of the liquid and the fine grain material to the pressure chamber 20 with a low moisture content. In order to smoothly and continuously supply the fine granular material with a moisture content to the pressure chamber 20, it is desirable to use a solution containing foam, such as a foaming agent solution, as the liquid. Furthermore, by using an aqueous solution of a foaming agent and a thickener as the liquid, the strength of the bubbles in the aqueous solution can be increased, thereby allowing the fine granular material to be smoothly introduced into the pressure chamber 20 with a lower water content. can be supplied. As the foaming agent, for example, Pozolith No. 505 (trade name) manufactured by Pozolith Bussan Co., Ltd. can be used, and as the thickening agent, for example, CMC-TE-V manufactured by Ternite Co., Ltd. can be used. A portion of the foaming agent solution fed to the foamer 28 can be fed to an agitated tank 48 for feeding fines. Various fine particulate materials such as clay, silt, coal ash, or slag can be used as the fine particulate material. It is preferable to use fine sand in order to facilitate handling of the scum. The following table shows an example of the supply conditions for fine grain material adopted when excavating an excavated ground with a gravel ratio of 80% using the excavation device 10.

[Table] Fine sand is used as the mixture and the fine grain material in the above table, and the above table shows the mixing ratio of the mixture and the foaming agent solution,
Figure 3 shows the feed rate of the mixture and the weight percentage of gravel in the shear reduced by the feed of the mixture. According to the above table, a mixture in which 1.312 tons of fine sand is mixed with water and a foaming agent solution at a ratio of 0.18 m ³ and 0.100 m ³ , respectively, is
^Pressure chamber 2
0, and the gravel weight ratio of shear in the pressure chamber is
75%, indicating that separation of the bubbles supplied from the bubble supply path 26 and shear was prevented. In addition, as the foaming agent solution at this time, the foaming agent and water are each 0.4 kg per 1 kg of thickener.
and 100. According to the foaming agent solution to which a thickener was added, the mixture could be properly supplied with an extremely low water content of 30.0% to show that On the other hand, in the case of mixtures, the foaming agent solution without the addition of a thickener is ^13.2
By supplying the shear particles to the pressure chamber 20 so that the amount of shear particles becomes 75%, it is possible to reduce the weight ratio of shear particles in the pressure chamber to 75%, thereby preventing separation of the bubbles supplied from the bubble supply path 26 and the shear particles. If a mixture of foaming agent solution and fine sand with no added thickener was used, this mixture should be reduced by 50%.
This shows that the water content was properly supplied into the pressure chamber 20. In order to reduce the weight ratio of shear in the pressure chamber to 75%, in order to smoothly supply the fine grain material to the pressure chamber as a mixture of fine grain material and water, the water content of the mixture must be a high value exceeding 230%. By supplying the fine granular material as a mixture with the foaming agent solution containing air bubbles, it is possible to properly supply the fine granular material at a water content as low as 50%. Also,
By adding a thickener to the foaming agent solution,
It becomes possible to properly supply the mixture at a lower water content. As is clear from the above, by supplying fine grain material to the pressure chamber and thereby reducing the gravel ratio in the shear in the pressure chamber, it is possible to create a rock with a high gravel ratio of 80%. Even during excavation, by supplying air bubbles to the pressure chamber, appropriate fluidity and water-stopping properties can be imparted to the shear, thereby allowing suitable tunnel excavation.

[Brief explanation of drawings]

FIG. 1 is a longitudinal sectional view schematically showing a shield excavation device for carrying out the method according to the invention. 10: Shield drilling equipment, 12: Shield main body, 20: Pressure chamber, 24: Bulkhead.

Claims (1)

[Claims] 1. A shield type tunnel excavation method in which air bubbles are injected into a pressure chamber or a face in front of a partition wall of a shield body, characterized in that fine grain material is supplied to the pressure chamber. Method. 2. The shield type tunnel excavation method according to claim 1, wherein the fine grain material is supplied to the pressure chamber using a solution containing bubbles as a transport medium. 3. The shield type tunnel excavation method according to claim 2, wherein the solution is an aqueous foaming agent solution. 4. The shield type tunnel excavation method according to claim 2, wherein the solution is an aqueous solution of a foaming agent and a thickener. 5. The shield type tunnel excavation method according to claim 2, wherein the water content of the mixture of the solution and the fine grain material is approximately 30%. 6. The shield type tunnel excavation method according to claim 1, wherein the fine grain material is fine sand.