JP2008231677A - Pit mouth forming method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a pit mouth forming method for forming a pit mouth efficiently at a site located in a city area, a place near a residential area, and the neighborhood where the reduction of underwater level is undesirable. <P>SOLUTION: In this pit mouth forming method for forming the pit mouth for start or arrival of a shield machine on an earth retaining wall 3 provided in a vertical shaft 2, a hole 82 for discharge extended from a wall surface 80 of the earth retaining wall 3 to the inside of the earth retaining wall is formed in a pit mouth forming part 4 of the earth retaining wall, a discharge part 46 of an electrode 40 of a discharge breakdown device 5 and a pressure transmitting medium 83 surrounding the discharge part are installed in the hole 82 for discharge, and then voltage is applied to the electrode 40 for discharge to crush the pit mouth forming part 4 and form the pit mouth. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a method of forming a wellhead by electric discharge in an urban area, a residential neighborhood, a site where it is not desired to lower the groundwater level nearby.

When forming a wellhead for starting or reaching a shield machine on the earth retaining wall of a shaft, a method of forming a well opening by crushing and removing the well opening forming part of the earth retaining wall by blasting is known (for example, Patent Document 1).
Japanese Patent Laid-Open No. 8-246782

However, the method of crushing the pit-forming part of the retaining wall by blasting cannot be used in urban areas, residential areas, etc. because of the loud noise (explosive sound) at the time of crushing. In addition, when blasting is used, it has a large effect on the nearby ground, and it is often not possible to use it at a site where it is not desired to lower the groundwater level in the vicinity. That is, in the method using blasting, there is a problem that the place where it can be used is limited.
In view of the above problems, the present invention provides a wellhead forming method capable of efficiently forming a wellhead in an urban area, a residential neighborhood, a site where it is not desired to lower the groundwater level nearby.

The wellhead forming method of the present invention is a wellhead forming method for forming a shield machine start or reach wellhead on a retaining wall provided on a vertical shaft, and the earth wall is formed from the wall of the retaining wall to a wellhead forming portion of the retaining wall. A discharge hole extending inside the retaining wall is formed, and after the discharge part of the electrode of the discharge crushing device and the pressure transmission medium surrounding the discharge part are installed in the discharge hole, a voltage is applied to the electrode to cause discharge. Thus, the wellhead forming portion was crushed to form a wellhead.
It is also characterized in that a discharge hole extending obliquely downward from the wall surface of the retaining wall toward the interior of the retaining wall is also characterized.
It is also characterized in that the discharge in the discharge hole is performed after the free surface formation hole is formed along the portion that becomes the peripheral surface of the wellhead in the wellhead formation portion.

According to the wellhead forming method of the present invention, it is possible to efficiently form a wellhead in an urban area, a residential neighborhood, a site where it is not desired to lower the groundwater level nearby.
Since the discharge hole is formed to extend obliquely downward from the wall of the retaining wall toward the interior of the retaining wall, leakage of the pressure transmission medium filled in the discharge hole from the discharge hole is prevented. Can be prevented. Therefore, since the discharge in the pressure transmission medium can be maintained, a reduction in crushing force can be prevented.
Since the free surface forming hole is formed along the portion that becomes the peripheral surface of the wellhead in the wellhead forming portion, the crack generated by the discharge easily reaches the free surface, and the wellhead forming portion can be efficiently crushed.

  1 to FIG. 7 show the best mode 1, FIG. 1 shows a wellhead forming apparatus, FIG. 2 shows a retaining wall provided with a wellhead forming portion as viewed from the front, and FIG. 3 shows a cross section of the retaining wall. 4 shows an exploded view of the core column body, FIG. 5 shows the connection by the connecting portion of the core column body, FIG. 6 shows the electric discharge crushing device, and FIG. Is shown in cross section.

  As shown in FIG. 1, the wellhead forming device 1 includes a wellhead forming portion 4 and a discharge crushing device 5 provided on the earth retaining wall 3 of the shaft 2.

  As shown in FIG. 2, the retaining wall 3 is formed by arranging a plurality of retaining pillars 51 side by side on the ground ground 7. As shown in FIG. 3, the earth retaining column 51 includes a core column 52 and a water stop 53. The water stop part 53 is formed of a solidified material called a soil cement having a low strength, for example. As shown in FIG. 4, the core column body 52 includes a wellhead forming portion 55 and a steel material 56.

  The wellhead forming portion 55 is formed of a solidified material such as high strength mortar or concrete. The wellhead formation part 55 is provided with the connection part 57 for the steel material connection provided up and down. Such a wellhead forming part 55 is filled with a solidifying material in the mold with the connecting part 57 installed on the mold so that a part of the connecting part 57 protrudes from both ends of the mold not shown. It can be formed by curing. The upper steel material 56a is connected to the connecting portion 57a above the wellhead forming portion 55, and the lower steel material 56b is connected to the connecting portion 57b below the wellhead forming portion 55. The connecting portion 57 and the steel material 56 are formed of, for example, H-shaped steel. The connection part 57 and the steel material 56 are connected by connection means such as a rivet joint, welding, a bolt, and a nut. For example, as shown in FIG. 5, the connecting portion 57 and the steel material 56 are connected to each other by a connecting plate 60 connected by these bolts 59a and nuts 59b, so that a wellhead is formed between the upper steel material 56a and the lower steel material 56b. The core column body 52 provided with the forming portion 55 is formed. The diameter of the wellhead forming portion 4 is set to be equal to or larger than the outside diameter of the shield machine (not shown), and the length of the core column body 52 is formed from the ground 10 to the length beyond the wellhead forming portion 4. The lengths of the upper steel member 56a, the lower steel member 56b, and the wellhead forming portion 55 of the core column body 52 are different depending on the location of the wellhead forming portion 4. That is, the upper connecting portion 57a is connected to the upper steel material 56a having a length corresponding to the length from the upper end portion of the wellhead forming portion 4 to the ground 10 and the lower connecting portion 57b is the lower end portion of the wellhead forming portion 4. A core column body 52 is formed by connecting a steel material 56 having a length matching the length from the bottom to the bottom of the retaining wall 3.

  According to the core column body 52 of the best mode 1, since the wellhead forming portion 55 is formed of a solidified material such as high-strength mortar or concrete, it is made of a material such as carbon fiber-containing concrete that can be cut with a cutter of a shield machine. Compared with the structure provided with the formed wellhead formation part, the cost of the core pillar body 52 and the earth retaining wall 3 using the same, and the cost concerning the wellhead formation work can be reduced. The core column body 52 provides the strength of the retaining wall 3 before the formation of the wellhead, and the wellhead forming portion 55 is formed only by a solidified material such as high-strength mortar or concrete that is easily broken by discharge described later. Therefore, the wellhead forming portion 55 can be easily broken by discharge by the discharge crushing device 5 described later, and the burden on the shield machine can be reduced.

A method for forming the earth retaining wall 3 will be described. A ground ground 7 is excavated from the ground 10 using an excavating machine such as an earth auger to form a hole 99 (see FIGS. 1 and 3) having a circular cross section in the depth direction of the ground 7. In this case, cement milk as a solidifying material for forming the water stop portion 53 is poured into the hole 99 while forming the hole 99, and stirred with the earth and sand at the current position to form a soil cement. After the hole 99 is formed to a desired depth, the core column body 52 is built from the lower steel material 56b side into the hole 99 containing the unconsolidated soil cement, so that the hardened soil cement is stopped. Function as. As shown in FIG. 2, a plurality of retaining pillars 51 are arranged side by side so that the retaining wall 3 provided with a wellhead forming portion 4 including a wellhead forming portion 55 of the plurality of retaining pillars 51. Is formed.
2A is an expected line of the wellhead to be formed in the wellhead forming portion 4. FIG. Further, the cross section of the left retaining column 51 in FIG. 3 shows a cross section obtained by cutting the portion of the upper steel material 56a of the retaining column 51, and the cross section of the central retaining column 51 in FIG. 3 is the retaining column. The cross section which cut | disconnected the part of the wellhead formation part 55 of the body 51 was illustrated, and the cross section of the earth retaining column body 51 of the right of FIG. 3 illustrated the cross section which cut | disconnected the part of the lower steel material 56b of the earth retaining column body 51.

The electric discharge crushing apparatus 5 is demonstrated with reference to FIG. The discharge crushing device 5 includes a power supply device 8 and an electrode device 9.
The power supply device 8 includes a booster device 12 and a pulse power output device 13. The booster 12 includes a power supply voltage input unit 14A, a booster circuit 15 including a transformer (not shown), and an output unit 14. The booster circuit 15 inputs a three-phase AC 200V power supply voltage via a power supply cable 14C connected to the power supply voltage input unit 14A, generates a 22 kV DC voltage, for example, and outputs a 22 kV DC voltage from the output unit 14. The output unit 14 includes a positive terminal 14a and a negative terminal 14b. The pulse power output device 13 includes an input terminal 16, a charging circuit 17, and an electrode connection unit 18 as an output unit. The input terminal 16 includes a positive terminal 16a and a negative terminal 16b. The electrode connecting portion 18 includes a positive terminal 18a and a negative terminal 18b. The charging circuit 17 includes a positive electrode line 17a, a negative electrode line 17b, a capacitor device 19, a capacitor device connection unit 20, and switches 21; 22. A switch 21 and a switch 22 are connected in series to the positive electrode line 17a. One end of the positive electrode line 17 a is connected to the positive electrode terminal 16 a of the input terminal 16, and the other end of the positive electrode line 17 a is connected to the positive electrode terminal 18 a of the electrode connection part 18. One end of the negative electrode wire 17 b is connected to the negative electrode terminal 16 b of the input terminal 16, and the other end of the negative electrode wire 17 b is connected to the negative electrode terminal 18 b of the electrode connection portion 18. The capacitor device connection unit 20 includes a plurality of positive electrode connection terminals 20a connected in parallel between the switch 21 and the switch 22 in the positive electrode line 17a and a plurality of negative electrode connection terminals 20b connected in parallel to the negative electrode line 17b. Prepare. A capacitor device connection terminal 20A for connecting one capacitor device 19 is formed by the pair of positive electrode connection terminal 20a and negative electrode connection terminal 20b. That is, since the capacitor device connection unit 20 includes a plurality of capacitor device connection terminals 20 </ b> A, a plurality of capacitor devices 19 can be connected to the booster device 12 and the electrode connection unit 18. The capacitor device connection unit 20 includes, for example, six capacitor device connection terminals 20A and can connect any number of capacitor devices 19 from one to six. That is, it is possible to obtain the power supply device 8 capable of arbitrarily increasing or decreasing the capacitor device 19 from one to six. The switch 21 is a switch for charging the voltage supplied from the booster 12 to the capacitor device 19, and the switch 22 is for discharging the charge charged in the capacitor device 19 and outputting it to the electrode device 9 via the electrode connection portion 18. It is a switch. Although not shown, the charging circuit 17 is grounded.

The electrode device 9 includes a connection cord portion 31 and an electrode portion 32. The connection cord part 31 includes an input side connector 35 having a positive terminal 35a and a negative terminal 35b connected to each of the positive terminal 18a and the negative terminal 18b of the electrode connection part 18 of the power supply device 8, and an electrode connection of the electrode part 32. An output side connector 37 connected to the connector 36 and an electrical connection cord 38 for connecting the input side connector 35 and the output side connector 37 are provided.
The electrode unit 32 includes an electrode connection connector 36 connected to the output side connector 37 and an electrode 40. That is, since the electrode portion 32 includes an electrode connection connector 36 that can be attached to and detached from the output-side connector 37 of the connection cord portion 31, and the electrode connection connector 36 includes an unillustrated electric wire attachment portion that can connect the electric wire 43 detachably, The wire electrode 41 described later can be easily replaced.

As shown in FIG. 6, for example, a wire electrode 41 or a coaxial electrode 42 is used as the electrode 40.
In the wire electrode 41, the electric wire 43 is cut, and a discharge portion 46 is formed by maintaining a constant discharge interval (gap) between the cut surface of the electric wire 43 and the cut surface of the electric wire 43 by the interval holding member 45. It is a configuration. The electric wire 43 is formed of a so-called covered wire having a wire diameter of about 4 mm to 5 mm in which a conductor wire such as a copper wire having a wire diameter of about 2 mm to 3 mm is covered with a resin such as vinyl resin. The wire electrode 41 includes one or more discharge portions 46.

As shown in FIG. 7, the spacing member 45 is formed in a cylindrical shape, and is a wire fixing portion 61; 62 formed by both end portions of the cylindrical hole, and a spacing maintaining portion 63 formed by the central portion of the cylindrical hole. Is provided. The hole diameters of the electric wire fixing portions 61; 62 are formed to have a diameter with which the electric wires 43 can be fitted. The hole diameter of the space | interval maintenance part 63 is formed in the diameter smaller than the diameter of the electric wire fixing | fixed part 61; 62. The central axes of the wire fixing portion 61, the wire fixing portion 62, and the interval maintaining portion 63 are the same. Electric wire end face abutting surfaces 64; 65 as stoppers are formed by step surfaces which are step portions between the spacing maintaining portion 63 and the electric wire fixing portions 61; 62.
In the state where the end surfaces of the wires 43; 43 fitted to the wire fixing portions 61; 62 are respectively abutted against the wire end surface abutting surfaces 64; 65, the spacing member 45 and the wires 43 are not shown in the figure. The gap maintaining part 63 forms a discharge gap g between the electric wires 43 by being fixed to each other with an agent or the like. That is, the gap maintaining unit 63 maintains the gap g as a discharge gap between the end surface of the electric wire 43 fixed to the electric wire fixing unit 61; 62 and the end surface of the electric wire 43. It can be set accurately. Note that an insulating vinyl adhesive tape, a fastening band, a rubber band, a dedicated connector, or the like may be used as the spacing member 45.

  As shown in FIG. 6, the coaxial electrode 42 includes, for example, a rod-shaped inner conductor 73 as one electrode such as a + electrode, a cylindrical insulator 74 that covers the outer periphery of the inner conductor 73, and an insulator 74. And an outer conductor 75 as the other electrode, such as a negative electrode. The outer conductor 75 constitutes a plurality of floating electrodes 76 provided at intervals in a direction along the center line of the inner conductor 73. The floating electrode 76 is an electrode that is electrically insulated from the power supply side. A tip-side discharge gap between the tip electrode 73t formed by the tip of the internal conductor 73 protruding and exposed from the tip 74t of the insulator 74 and the tip-side floating electrode 76t that is the floating electrode 76 closest to the tip electrode 73t. 77 is formed, and an intermediate discharge gap 78 is formed between the end 76s and the end 76s of the floating electrodes 76 facing each other. A plurality of intermediate discharge gaps 78 are formed. A discharge portion is formed by the tip electrode 73t and the tip side floating electrode 76t arranged with the tip side discharge gap 77 therebetween. A discharge portion is formed by the floating electrode 76 and the floating electrode 76 arranged with the intermediate discharge gap 78 therebetween. That is, the coaxial electrode 42 includes a plurality of discharge portions. In this case, since the electrode portion 32 includes the electrode connection connector 36 connected to the output side connector 37 and the coaxial electrode 42, the coaxial electrode 42 can be easily replaced by attaching and detaching the electrode connection connector 36 to the output side connector 37. .

  Next, a method for forming a wellhead will be described. The earth retaining wall 3 is formed, and the inner ground surrounded by the earth retaining wall 3 is excavated to form the shaft 2 for starting the shield machine. Then, a free surface forming hole 81 and a discharge hole 82 extending from the wall surface 80 of the retaining wall 3 (inner wall surface of the shaft 2) to the inside of the retaining wall 3 are formed in the well opening forming portion 4 of the retaining wall 3. For example, as shown in FIG. 2, the free surface forming hole 81 is formed along the portion that becomes the peripheral surface of the wellhead in the wellhead forming portion 4, and the discharge is performed on the inside of the peripheral surface of the wellhead in the wellhead forming portion 4 A plurality of use holes 82 are formed. The free surface forming hole 81 is preferably formed by continuous drilling along the predicted line 4A of the wellhead so as to surround the wellhead forming portion 4. The discharge hole 82 is formed to extend obliquely downward from the wall surface 80 of the retaining wall 3 toward the interior of the retaining wall 3. The distance a between the discharge hole 82 and the free surface forming hole 81 and the distance b between the discharge hole 82 and the discharge hole 82 adjacent to each other are determined by experience. For example, the distance a is about 30 cm and the distance b is about 30 cm.

  The discharge operation is performed by applying a voltage to the electrode 40 after installing the discharge portion 46 of the electrode 40 in the discharge hole 82 and a pressure transmission medium 83 such as water or the like surrounding the discharge portion 46. Discharge. Thereby, the wellhead formation part 4 can be crushed. Thereafter, the shield machine is carried into the shaft 2 and driven, and the crushed pieces are sent to the rear of the shield machine by a soil removal device such as a screw conveyor or a soil discharge pump outside the shield machine. That is, after the pit formation portion 4 inside the shaft 2 is crushed by electric discharge, the fragments are removed by the shield machine. In this case, since the wellhead forming portion 4 is crushed by crushing by discharge, the wellhead forming portion 4 can be finely crushed. As a result, the starting wellhead is formed. It is also possible to form a wellhead for reaching the shield machine.

According to the best mode, the sound generated at the time of crushing by electric discharge is smaller than that when crushing by blasting, so it can be used in urban areas, residential areas, etc. Since the crushing is performed by increasing the pressure in the discharge hole 82 by the volume expansion caused by the vaporization of the transmission medium 83, the wellhead can be formed efficiently. Moreover, crushing due to electric discharge has little influence on the nearby ground, and can be used at a site where it is not desired to lower the groundwater level in the vicinity, so that a wellhead can be formed efficiently.
When performing the above-mentioned discharge, if discharge is performed after closing the opening on the wall surface 80 side of the discharge hole 82 with the lid of the steel plate or the cutter head of the shield machine, the discharge hole 82 at the time of discharge is used. The pressure leakage from the inside to the outside can be prevented, the crushing force can be increased, and the wellhead forming portion 4 can be effectively crushed.

  According to the best mode, the discharge hole 82 is formed so as to extend obliquely downward from the wall surface 80 of the retaining wall 3 toward the interior of the retaining wall 3, so that the discharge hole 82 is filled. Leakage from the discharge hole 82 of the pressure transmission medium 83 can be prevented. Therefore, since the discharge in the pressure transmission medium 83 can be maintained, a reduction in crushing force can be prevented. In addition, the pressure transmission medium 83 can be easily filled into the discharge hole 82, and refilling work can be reduced.

  According to the best mode, since the free surface forming hole 81 is formed along the portion that becomes the peripheral surface of the wellhead in the wellhead forming portion 4, cracks generated by the discharge easily reach the free surface, and the wellhead forming portion 4 is formed. Can be efficiently crushed. In particular, since the free surface forming hole 81 is formed by continuous drilling, a wellhead having a desired diameter can be formed efficiently.

  According to the best mode, the wellhead forming portion 4 is not cut by a shield machine, but is crushed by electric discharge, so that a dedicated cemented carbide cutter is not required because the wellhead forming portion 4 is cut by a shield machine. This can reduce the work load of the shield machine required for cutting.

  According to the best mode, the well opening forming portion 4 can be finely crushed by electric discharge crushing, and the fragments can be efficiently discharged by the earthing device of the shield machine.

  According to the best mode, since the core column body 52 having the wellhead forming portion 55 formed of a solidified material such as high-strength mortar or concrete is used, the core column body 52 and the earth retaining wall 3 using the core column body 52 are used. Cost, and in turn, the cost related to the wellhead formation work can be reduced.

If the electrode 40 including a bag or a box filled with the pressure transmission medium 83 so as to surround the discharge unit 46 is used, the direction of the discharge hole 82 may not be downward.
The method of forming a wellhead by electric discharge according to the present invention includes a reinforced concrete retaining wall constructed using steel sheet piles such as H-shaped steel and sheet pile as a formwork, and a reinforced concrete retaining wall made of continuous walls (continuous underground wall). The present invention can also be applied when forming a wellhead. In this case, after the concrete portion is crushed, the rebar portion that is not crushed may be removed.

The block diagram which shows a well-hole formation apparatus (best form). Front view of earth retaining wall (best mode). Cross-sectional view of the earth retaining wall (best mode). The exploded perspective view of the core pillar (the best form). The figure which shows the connection state of the connection part of a core pillar body, and steel materials (best form). The block diagram which shows an electric discharge crushing apparatus (best form). Sectional drawing which shows a space | interval maintenance material (best form).

Explanation of symbols

1 wellhead forming equipment, 2 shafts, 3 retaining walls, 4 wellhead forming parts,
5 discharge crushing device, 40 electrodes, 46 discharge section, 80 wall of earth retaining wall,
81 free surface forming holes, 82 discharge holes, 83 pressure transmission medium.

Claims (3)

  Discharge extending from the wall of the retaining wall to the inside of the retaining wall in the well opening forming method of forming a wellhead for starting or reaching the shield machine in the retaining wall provided in the shaft After forming the hole for discharge and installing the discharge part of the electrode of the discharge crushing device and the pressure transmission medium surrounding the discharge part in the discharge hole, the voltage is applied to the electrode to discharge and crush the wellhead forming part A wellhead formation method characterized by forming a wellhead.   2. The wellhead forming method according to claim 1, wherein a discharge hole extending diagonally downward from the wall surface of the retaining wall toward the inside of the retaining wall is formed.   The method for forming a wellhead according to claim 1 or 2, wherein the discharge in the discharge hole is performed after the free surface forming hole is formed along the portion that becomes the peripheral surface of the wellhead in the wellhead forming portion. .

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