JP2003064986A - Cutting face cave-in preventing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for positively preventing cave-in of a cutting face at a front end of a leading body when a small-diameter steel pipe is propulsively embedded. SOLUTION: The method for preventing the cave-in of the cutting face at the front end of the leading body during propelling work, is carried out by mounting a cutting tool on the periphery of the leading body at the front end when the small-diameter steel pipe is propulsively embedded while the natural ground is being cut. According to the method, a cutoff device is set on an inner surface of the steel pipe at a rear end thereof. The cutoff device is formed of a cylinder body, a cutoff ring, and a plate. The cylinder body has a diameter smaller than the inner diameter of the steel pipe. The cutoff ring is mounted on a shell of the cylinder body in a manner abutting on an inner surface of the steel pipe. The plate is rigidly set on the cylinder body to block the same. Then, by injecting slurry from the cutoff device into the steel pipe to fill the same, slurry pressure is generated in the steel pipe, and the small-diameter pipe is propelled by a driving machine set in a starting shaft while resisting cutting face earth pressure and hydraulic pressure.

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for preventing collapse of a face at the tip of a leading conductor in a propulsion method for protruding and embedding a small-diameter steel pipe. 2. Description of the Related Art A conventional propulsion method for burial of a small-diameter sewer is relatively small in length because the length of propulsion is relatively short and does not require a direction correcting device or the like. Propulsion construction from the starting shaft is possible. As the pipe material, a steel pipe manufactured to a length that can be installed in the starting shaft is mainly used. The excavator installed in the starting shaft has a structure in which a driving device mounted on a guide frame can move forward and backward by a cylinder device. The outer periphery of the rear end of the steel pipe is grasped by the steel pipe chuck portion of the driving device, and the excavation device is driven to transmit the rotation to the steel pipe via the steel pipe chuck portion. At the tip of the steel pipe, a tip conductor equipped with a drilling tip on the outer circumference is installed, the steel pipe is advanced while giving a rotating force to the steel pipe by the steel pipe chuck part of the drive device, and the ground is cut by the drilling tip at the tip, It is a method of burying steel pipes while taking excavated earth and sand into the steel pipes. [0003] The above-described propulsion method for burying small-diameter steel pipes has made it possible to efficiently lay and bury steel pipes from the inside of a small-diameter starting shaft. However, in the case of a ground with soft soil conditions or a ground with a lot of groundwater, since the tip conductor 14 at the tip is open as shown in FIG. The steel pipe 11 flows into the tip conductor 14 together with the groundwater.
Cavities 16 are formed outside the space, which causes the ground to sink. [0004] Therefore, in the case of soft ground or ground with a lot of groundwater, an auxiliary construction method has been adopted in which the ground is improved by injecting a chemical solution into the buried portion of the steel pipe to make the ground at the face part self-supporting. However, the above-mentioned auxiliary method by the injection of the chemical liquid is difficult to penetrate the chemical liquid between the soil particles in the soft ground, and in the ground with a lot of groundwater, the chemical liquid is flowed or diluted before hardening, and it is difficult to expect the effect thereof. There was a problem. [0005] Therefore, the present invention provides a method for preventing collapse of the face ground at the end of an open leading conductor in a propulsion method for propelling and embedding a small-diameter steel pipe. [0006] That is, the present invention is to provide a cutting tool on the outer periphery of the leading conductor at the tip and to bury a small-diameter steel pipe while propelling and embedding it while cutting the ground. In a method for preventing the face at the tip of the leading conductor from collapsing, the outer shell of the cylinder smaller than the inner diameter of the steel pipe is equipped with a water stop ring so as to abut against the inner surface of the steel pipe, so as to close the cylinder. A water stop device consisting of a fixed plate is installed on the inner surface of the rear end of the steel pipe, and muddy water is injected into the steel pipe from the water stop device to fill the steel pipe, thereby generating mud pressure inside the steel pipe and causing the face to fall. This is a method for preventing face collapse, in which a small-diameter steel pipe is propelled by an excavator installed in a starting shaft while resisting earth pressure and water pressure. [0007] The water shut-off device is manufactured by making a cylindrical body smaller than the inner diameter of the steel pipe to a predetermined length in the propulsion direction. A waterproof ring made of a rubber material having a predetermined height is attached to the outer shell of the cylindrical body along the outer periphery of the steel pipe so as to abut on the inner surface of the steel pipe. The water blocking ring may be formed by making the inside of the ring hollow and sending compressed air or the like into contact with the inner surface of the steel pipe. On one of the front and back of the cylinder,
A plate is fixed by welding or the like so as to close the cylinder. The plate is provided with an injection hole for injecting muddy water into the steel pipe and a discharge hole for discharging muddy water and excavated soil. The excavator has a mechanism for moving a driving device mounted on a guide frame back and forth by a cylinder device. The outer periphery of the steel pipe is grasped by the steel pipe chuck part of the drive unit. By driving the driving device, the steel pipe chuck portion rotates, and a rotational force is transmitted to the steel pipe. The driving device is mounted on a guide frame, and can be moved forward and backward by a cylinder device mounted on the guide frame. The leading conductor forms a cylindrical body having substantially the same diameter as the outer diameter of the steel pipe, and is attached to the leading end of the steel pipe by welding or the like. A hard drilling tip is embedded and cuts the cutting ground at the tip of the leading conductor. A water stop device is installed on the inner peripheral surface at the rear end of the steel pipe, and muddy water is injected from an injection hole provided in the plate to fill the inside of the steel pipe with muddy water. The muddy water is sealed by the water stop ring of the water stop device and does not leak backward. The muddy water is retained in the steel pipe in the front and the collapse of the face ground is prevented. By driving the driving device to rotate the steel pipe chuck portion, the propulsion construction of the steel pipe is performed while cutting the ground with a cutting tip of a leading conductor at the tip. At this time, muddy water is sent from the injection hole,
Efficient propulsion construction can be performed by discharging and circulating mud from the discharge holes. When the propulsion construction of one steel pipe is completed, the drive unit of the excavator is retracted, the next steel pipe is installed in the space, and joined to the rear end face of the previous steel pipe. When the joining is completed, the water stopping device installed inside the rear end of the previous steel pipe is pulled back to the rear end of the newly connected steel pipe by the pull-back means. When the installation of the water stopping device is completed, the driving device is driven to resume the propulsion construction. Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a plan view illustrating a method for preventing face collapse according to the present invention. The excavator 1 is installed in the circular starting shaft 12. As the structure of the excavator 1,
The guide frame 4 is assembled so that the steel pipe 11 to be buried is at the planned burial position, and the drive unit 2 having the steel pipe chuck unit 3 is mounted on the guide frame 4. (Not shown) are connected to each other, so that the driving device 2 can move back and forth on the guide frame 4.
A steel pipe chuck 3 for grasping the outer periphery of the end is provided, and a mechanism for transmitting rotation by the driving device 2 to the steel pipe 11 is provided. Inside the rear end of the steel pipe 11, a water stop device 5 is installed. The structure of the water stop device 5 is provided with a water stop ring 7 on the outer periphery of the cylindrical body 6 smaller than the inner diameter of the steel pipe 11 so as to abut against the inner surface of the steel pipe 11. The plate 8 is fixed to one side.
The plate 8 is provided with an injection hole 9 for feeding muddy water and a discharge hole 10 for discharging muddy water and excavated soil. A gate valve is provided in the injection hole 9 and the discharge hole 10. To the rear end of the water stopping device 5, a telescopic jack, which is a retraction means 13 provided in the excavator 1, is connected so that the steel pipe 11 can move forward and backward. The water stop ring 7 may be a ring shape made of a rubber material having a predetermined height so as to be in contact with the inner surface of the steel pipe 11, or a hollow inside the ring to feed compressed air to the steel pipe 11. A method of contacting the inner surface may be used. Although a telescopic jack has been disclosed as the retraction means 13, other retraction techniques according to the prior art can be used. FIG. 2 is a plan view for explaining a method of installing a steel pipe when propulsion of one steel pipe is completed. When the propulsion construction of one steel pipe 11 is completed, the connection between the water stop device 5 and the telescopic jack is disconnected, and the telescopic jack is reduced. Further, the steel pipe 11 of the steel pipe chuck portion 3 is also opened, and returned together with the driving device 2 by the cylinder device. The next steel pipe 11 is hung in the space formed between the rear end of the previous steel pipe 11 and the driving device 2, and is installed on the guide frame 4. When the installation is completed, the rear end of the steel pipe 11 is grasped by the steel pipe chuck 3, the steel pipe 11 is advanced by the driving device 2, and the butt joint is joined to the previous steel pipe 11 by welding. When the retractable jack, which is the retraction means 13, is contracted, since the retraction force of muddy water is acting on the water stopping device 5, a stopper is attached to the end face of the steel pipe 11 in advance to return the water stopping device. To prevent FIG. 3 is a plan view for explaining a method of moving the water stopping device of the present invention. When the joining of the steel pipe 11 is completed, the telescopic jack is extended and the head of the telescopic jack is connected to the rear end of the water stop device 5. When the connection is completed, the telescopic jack is contracted, and the water stop device 5 is moved backward while sliding in the steel pipe 11. At this time, since the volume in the steel pipe 11 in front of the water stop device 5 changes, muddy water is injected from the injection hole 9 and the steel pipe 11 is moved with the muddy water being filled. When the water stop device 5 moves to the rear of the rearmost steel pipe 11, the propulsion work of the steel pipe 11 is restarted. As described above, according to the method for preventing face collapse according to the present invention, the steel pipe is filled with muddy water, and the muddy water pressure constantly acts on the face at the tip of the leading conductor. Even in soft ground or ground with a lot of groundwater, the ground and groundwater can be held down by muddy water pressure, and the collapse of the face can be prevented reliably, and safe small-diameter steel pipe propulsion construction can be performed. [0018]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a plan view for explaining a face collapse prevention method of the present invention. FIG. 2 is a plan view illustrating a method for installing a steel pipe when propulsion of one steel pipe is completed. FIG. 3 is a plan view illustrating a method of moving the water stopping device of the present invention. FIG. 4 is a vertical cross-sectional view illustrating a face condition in a conventional small-diameter steel pipe propulsion construction. [Description of Signs] 1 Excavator 2 Drive 3 Steel Pipe Chuck 4 Guide Frame 5 Water Stopper 6 Cylindrical 7 Water Stop Ring 8 Plate 9 Injection Hole 10 Discharge Hole 11 Steel Pipe 12 Starting Pillar 13 Pullback Means 14 Leading Conductor 15 Excavation Tip 16 cavity

Claims (1)

[Claim 1] A cutting tool is provided on the outer periphery of a leading conductor at the tip to cut and bury a small diameter steel pipe while cutting ground, so that a cutting face at the leading end of the leading conductor is cut during propulsion construction. In a method for preventing collapse, the outer shell of a cylindrical body smaller than the inner diameter of the steel pipe is provided with a water stop ring so as to abut against the inner surface of the steel pipe, and is constituted by a plate fixed to close the cylindrical body. The water stop device is installed on the inner surface at the rear end of the steel pipe, and muddy water is injected into the steel pipe from the water stop device to fill the steel pipe, thereby generating mud pressure inside the steel pipe and resisting face pressure and water pressure. A method for preventing face collapse, wherein a small diameter steel pipe is propelled by an excavator installed in a starting shaft while the shaft is being driven.