JP4201129B2 - Mud pressure shield method - Google Patents

Description

  The present invention relates to a mud pressurizing shield method suitable when the soil to be excavated by the mud pressurizing shield method is soil with a high silt and clay content.

  For example, as shown in Non-Patent Document 1, the mud pressurizing shield method is provided with a partition wall at the rear part of the cutter wing to form a mud clay chamber, and the mud mud material is poured into the earth and sand excavated by the cutter and powerful with a mixing blade. The excavated sediment is converted into a mud with imperviousness and plastic fluidity, and this is filled in the mud chamber and the screw conveyor. This is a construction method in which mud pressure is generated in the mud, facing the earth pressure of the face and the groundwater pressure, and digging while balancing the propulsion amount of the shield machine and the amount of soil discharged. In other words, in this construction method, when the shield machine digs up, the mud pressure is constantly measured by a special earth pressure gauge attached to the bulkhead of the mud soil chamber, and shielded so that the formula mud pressure = static earth pressure + groundwater pressure is satisfied. By adjusting the jack speed and screw conveyor rotation speed, the face is stabilized and changes in the natural ground are minimized, and the groundwater in the natural ground is surely springed by the imperviousness of mud and the retaining action of the screw conveyor. Prevention can be achieved.

Edited by the Mud Pressurized Shield Construction Association “Muddy Pressurized Shield Method: Accumulated Materials” April, 1993 issue

  By the way, when excavating natural clay with this mud pressure shield method, when there is a lot of clay and silt (soil grain size of 0.074 mm or less) with respect to the cross section to be excavated, especially 30% or more (mud addition) Based on the “Calculation formula of concentration and injection rate” by the Pressure Shield Association.) When included, the excavation efficiency is significantly reduced, and when the excavated sediment is discharged with the sediment pump, Or when the piping is blocked, and when sediment transport is resumed, there is a problem that the pump pressure is suddenly increased and a failure is likely to occur.

  In order to solve such a problem, it is conceivable to add a large amount of water. In this case, however, the viscous soil is in a liquefied (muddy water) state, the face pressure is not stable, and the ground is weak. This hydration method is also not preferable because it has a problem that when it is easily liquefied and when liquefied excavated soil is pumped, air accumulates in the upper part of the pipe and noise is generated due to the air hammer phenomenon. .

  Furthermore, in this construction method, water and polymer additives are added to the face plate of the shield machine for the purpose of subsidizing plastic fluidization of excavated soil, preventing adhesion of viscous soil to the face plate, and facilitating unloading of excavated soil. In order to extend the pumping distance and prevent clogging at the site where the pumping system is used for injecting from the injection port formed in the bulkhead and the screw conveyor, or for excavating earth and sand. In order to reduce frictional resistance, water is injected through the water injection ring, but injecting excessive additives for the reason that it is easy to carry out and pump out excavated earth and sand leads to an increase in the amount of residual soil disposal. It is not preferable.

  The present invention was devised based on such knowledge, and the object of the invention is that when the soil to be excavated by the mud pressure pressurizing method is a lot of silt and clay, especially 30% of the total amount of soil. Excavation efficiency can be improved even when the soil is overly cohesive and very sticky, and mud soil can be equalized by reducing adhesion in the chamber. It is possible to extend the pumping distance, reduce the volume of the soil without liquefying the soil, and suppress the occurrence of the air hammer phenomenon to prevent noise during pumping. It is intended to provide a mud pressure shield method that can be used.

 When the present inventors examined the problems of the prior art in detail, when there is a large amount of clay and silt (soil particle size of 0.074 mm or less), especially 30% or more (concentration and injection rate by the Mud Pressurizing Shield Association) If it is included, the adhesive action (adhesive force) is rapidly increased because the colloidal particles are entangled in a chain and are very strongly linked by the electrochemical action of the colloidal particles in the clay. It is easy to adhere to the face plate (cutter pit) of the shield machine, the chamber, or the screw conveyor, and the excavation efficiency is remarkably lowered. Also, when excavating sediment is discharged with a sediment pump. It was found that viscous soil adheres inside the pressure feed pipe and the pipe resistance increases rapidly, leading to troubles such as failure of the pressure feed pump and blockage of the pipe. In addition, when the fluidity of the excavated soil is reduced due to blockage of the pipe due to consolidation dehydration in the pipe caused by continuous pressurization by the above-mentioned pumping pump, or the water absorption of colloidal particles in the pipe during the sediment pumping stop time, and sediment pumping is resumed In addition, it was also found that the pump pressure suddenly increased and it was easy to break down.

  Therefore, the present inventors, in the case of viscous soil excavation, is suitable for viscous mud from the viewpoint of eliminating the above colloidal chain without adding excessive water and reducing the adhesion of colloidal particles in the viscous mud. As a result of investigating the agent, a new mud pressure shield construction method that achieves the above-mentioned purpose was found.

That is, in the present invention, the mud material is poured into the silt and sand having a large amount of silt and clay excavated by the cutter, kneaded to make mud, and this is filled in the mud chamber in the rear of the cutter and generated in the mud chamber. A mud pressurizing shield method that excavates by mud pressure, and includes a cationic surfactant consisting of the following general formula (Chemical Formula 1) in the mud material: .

 Furthermore, the present invention is the mud pressure shield method, wherein the general formula (Chemical Formula 1) includes one or more of lauryltrimethylammonium chloride, cetyltrimethylammonium chloride, stearyltrimethylammonium chloride, and distearyldimethylammonium chloride. It is desirable to use a cationic surfactant.

  In the present invention, a cationic surfactant having an electrochemical action is used as an additive, so that the cation is adsorbed on colloidal particles of viscous soil having a high adhesive force and repels the colloidal particles. Thus, the viscosity of the clay can be reduced. In addition, the cationic surfactant is adsorbed on the viscous soil, and the surface of the excavated soil is hydrophobized, so that the swelling of the viscous soil is suppressed and adhesion to the shield machine can be greatly reduced.

  Furthermore, in the present invention, this cationic surfactant reduces cutting efficiency because it reduces adhesion to the shield machine face plate despite the low moisture permeability of the cut clay-like viscous soil. Can be greatly improved.

 In addition, by using the cationic surfactant according to the present invention, compared to the conventional method of water injection, the adhesion force is significantly reduced with less water injection and without liquefying the clay soil. The excavation and propulsion efficiency during construction of the mud mud pressure shield method can be greatly improved, and the piping pumping efficiency of the waste clay can be improved, and the waste clay is liquefied. Since it can be pumped in a hard state without causing it to occur, it is possible to reduce the volume of the soil, and to suppress the occurrence of air hammer reduction, thereby preventing the generation of noise during pumping.

 The specific cationic surfactant according to the present invention is represented by the general formula (Chemical Formula 1) from the viewpoint of adsorptivity to clayey soil, lauryltrimethylammonium chloride, cetyltrimethylammonium chloride, stearyltrimethylammonium chloride, distearyldimethylammonium chloride. It is preferable to mix one or more of these.

  More specifically, the cationic activator according to the present invention includes Cotamin 24P manufactured by Kao Corporation as lauryltrimethylammonium chloride, Coatamine 60W manufactured by Kao Corporation when cetyltrimethylammonium chloride is used, and stearyltrimethylammonium chloride. In the case of using chloride, Cotamin 86P manufactured by Kao Corporation, in the case of using distearyldimethylammonium chloride, Cotamin D86P manufactured by Kao Corporation, and in the case of using a mixture of cetyltrimethylammonium chloride and stearyltrimethylammonium chloride. Cotamin 86W manufactured by Kao Corporation can be used.

  When the cationic surfactant according to the present invention is used in the shield excavation method, it is necessary to use an aqueous solution prepared by mixing about 1 to 5 parts by weight of the product of Example 1 with respect to 100 parts by weight of water. preferable.

 A preferred embodiment of the construction method according to the present invention will be described. The shield machine used in the present invention is preferably composed of a cutter, a mud chamber, a shield jack, and a mud discharge conveyor.

 The soil is excavated from the ground, ground, etc. with a cutter, mud material is poured into the excavated soil, kneaded and converted into mud, filled into the mud chamber, and put into the mud chamber by the thrust of the shield jack. A typical mechanism is to generate mud pressure and excavate.

  Here, the mud is a kneaded material of excavated earth and mud material, and has water impermeability and plastic fluidity.

 The cutter includes a face plate method, a spoke method, and the like, and a spoke method with a small adhesion area is preferable from the viewpoint of adhesion of viscous soil.

 From the viewpoint of mud fluidity of the earth and sand excavated by the cutter, the mud chamber is preferably in a shape with few staying portions in the mud chamber.

 It is preferable to sufficiently knead the mud material and earth and sand in the mud chamber behind the cutter while excavating with the cutter. In such a case, it is preferable that a mixing blade is installed at the rear part of the cutter.

 It is preferable to inject the mud material into the excavated soil from the fishtail part, spoke part, mud soil chamber part, etc. in the center of the cutter, and in particular from the viewpoint of uniform dispersion and reduction of adhesion, preferable.

・ Experimental example 1
(1) Viscous soil Based on on-site viscous soil in Kawasaki City, Kanagawa Prefecture, the concentration and addition rate are set as shown in Table 1 using three types of water and additives, and rotational friction resistance measurement made by Kido Giken Co., Ltd. A friction resistance comparison test was performed using a machine.
On-site sample soil collection location near Daishi, Kawasaki City, Kanagawa GL-15m
Soil Water content of clay mixed with silt 39.4%
Adhesive strength Cuu 0.067N / mm2
As shown in FIGS. 2 and 3, the rotary friction coefficient measuring machine used in this experimental example has a test piece in a disk shape, and measures the frictional resistance during towing by rotating it. The detailed configuration is as follows.
・ Drive section Rotation speed 0-0.7p. m
・ Measurement unit body Load cell digital scale
Maximum measuring force 20kgf
・ Shape dimensions Lower specimen frame outer diameter φ170mm
Upper specimen frame outer diameter φ146mm, inner diameter φ46mm
・ Weight frame 3.5kg (one set of upper and lower parts)
(2) Mudstone material An aqueous solution having a predetermined solid content concentration was used as a mud material. The clay material 1 is only water.

  1 and 2 show a schematic configuration of the frictional resistance tester used in this experiment. FIG. 1 is a plan view and FIG. 2 is a cross-sectional view.

Table 3 shows the results of evaluation using a frictional resistance tester having the above-described configuration. In addition, the evaluation criteria evaluated highly the measured value with low frictional resistance.
Table 2 shows the degree of reduction in frictional resistance for each mud soil material and addition rate, assuming that the friction resistance value at 0% addition rate without the mud soil material is 100.

添加率：現場資料土の容量に対する作泥土材の添加容量の比率

Rate of addition: Ratio of the added capacity of mud material to the capacity of on-site data soil

  As is clear from the above experiment, it can be seen that the frictional resistance is clearly reduced by using the mud clay material 4 according to the present invention rather than simply adding water to eliminate the colloidal chain.

・ Experimental example 2
Next, using the model shown in FIG. 3, the excavated earth and sand excavated by the mud pressurizing shield method using the earth and sand pressure pump was compared with water and additives, and the discharge pressure of each pressure pump was measured. . The results are shown in Table 4.
Location GL-15m near Daishi, Kawasaki City, Kanagawa Prefecture
Soil Clay water content 39.4%
Adhesive strength Cuu 0.067N / mm2
In FIG. 3, the distance between the pump P0 and the pump P1 and between the pump P1 and the pump P2 is 400 m, the distance between the pump P2 and the pump PE is set to 425 m, and the piping of 8B size is used. Moreover, the discharge pressure of Comparative Examples 1, 2, 4, and 6 was not measured.

添加率：掘削対象土の容量に対する作泥土材の容量添加率の比率

Rate of addition: Ratio of volume addition rate of mud material to volume of excavated soil

As is clear from the experimental results, when the product of Example 1 was added and pumped, when water was added and pumped, or when a conventional polycarboxylic acid or polyacrylic acid polymer was added and pumped In comparison, the discharge pressure of each pump is small, and the load on the pump can be kept low. In addition, it can be seen that this load reduction is more effective when a large amount of Example 1 product is added, such as 20% rather than 10%.

  INDUSTRIAL APPLICABILITY The present invention can be used in a mud pressure shield method for excavating soil quality including cases where the tackiness is remarkable.

It is a top view which shows schematic structure of the frictional resistance tester used for the adhesive force comparison test of the excavated earth and sand excavated by the mud pressure pressurization shield method which concerns on this invention. It is sectional drawing of the same frictional resistance tester. It is a model figure of the apparatus which pumps and excavates excavated earth and sand excavated by the mud pressure pressurization shield method concerning this invention with a pump.

Claims (2)

The mud material is poured into the silt and sand with a lot of clay and excavated by the cutter, kneaded to make mud, and this is filled in the mud chamber in the rear of the cutter, and is dug by the mud pressure generated in the mud chamber. A mud pressurizing shield method, wherein a cationic surfactant composed of the following general formula (Chemical Formula 1) is contained in the mud clay material.

In the general formula (Chemical Formula 1), R1 represents a saturated or unsaturated alkyl group having 1 to 18 carbon atoms, and R2 represents a benzyl group or a saturated or unsaturated alkyl group having 10 to 18 carbon atoms. The mud pressure shield according to claim 1, wherein the general formula (Chemical Formula 1) is a cationic surfactant containing at least one of lauryltrimethylammonium chloride, cetyltrimethylammonium chloride, stearyltrimethylammonium chloride, and distearyldimethylammonium chloride. Construction method.

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