JPH09256784A - Excavation method and excavator therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prolong a cutter life and to promote a boring speed by forming cutting grooves or cracks with super-high pressure water having specific jet pressure along a planned passing line of a disc cutter, and crushing bedrocks or ground such as gravels while rolling the edge of the disc cutter on the cutter grooves or cracks. SOLUTION: A disc cutter 10 is provided with an edge body 10a having a wedge shaped section formed in the shape of a ring on the circumference of a cutter saddle, and it is mounted to a cutter mounting base 11 through a bearing 13 in a rolling state. A super-high pressure water jet device 12 is mounted near to a setting site of the disc cutter 10, and before the bedrock is crushed with the disc cutter 10, super-high pressure water having jet pressure 100-3500kg f/cm<2> is jetted toward a planned passing line of the disc cutter 10 to cutting grooves or cracks are formed in the excavated ground surface. By the constitution, the bedrocks or gorund such as gravels are easy to crush, and the order to prevent the abrasion in the edge of the disc cutter10, a cutter life is prolonged.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a tunnel excavator such as a TBM or a shield machine, an excavator for constructing a foundation pile for a large structure, an underground excavator for an underground space, and the like.
In particular, the present invention relates to an excavation method and an excavator for the purpose of prolonging the life of a disk cutter and efficiently crushing rock formations, gravel and other strata, concrete and the like.

[0002]

2. Description of the Related Art For example, when constructing tunnels for railways, roads, headraces, water and sewage systems, TBM (Tu
Tunnel excavators such as nnel Boring Machin) and shield machines (Shield Machin) are widely used. A tunnel excavator (hereinafter, also simply referred to as an excavator) is an excavator that excavates while continuously cutting and crushing earth and sand with a cutter head on the front surface. The TBM is a roller cutter type cutter structure such as a tooth cutter, a disk cutter, an insert cutter, etc. so that the excavator mainly used for mountain tunnels can efficiently excavate rocks and gravel layers. It is adopted. In addition, the shield machine mainly adopts a cutter structure in which cutting bits are fixed so that soft ground such as sandy soil and clay with high water content can be efficiently excavated, but it penetrates into the bedrock layer and gravel layer. In consideration of such a case, there is also a composite type using the roller cutter together.

In addition, a cutter system using a roller cutter or the like is also adopted in a drilling machine for foundation excavation of a large structure, an underground excavator for underground space, etc. in order to correspond to a rock layer or a gravel layer. There is.

Among these roller cutter type cutter structures, the present invention is particularly directed to a disk cutter having a blade body having a ring-shaped wedge-shaped cross section on the outer peripheral portion of the cutter saddle. For the cutter head portion, a plurality of disc cutters are arranged based on the design calculation so as to realize the most efficient excavation. Then, by rotating the excavation head while pressing the disk cutter against the rock mass with a constant thrust, the disk cutter rolls in the circumferential direction to cut / crush the rock mass.

In this case, as the excavation progresses,
The cutting edge of the disc cutter wears and the drilling speed gradually decreases. If you continue to use the worn cutter,
Although the cutter life can be extended, the drilling speed decreases, which increases the operating cost of the drilling machine equipment and the like and increases the drilling unit price as a whole. Therefore, since the unit cost of drilling is expressed as a function of the drilling speed and the life of the cutter, the drilling speed can be defined by geological conditions such as rock type and strength, operating conditions such as thrust and rotation speed, cutter type, cleaning. The tool life is determined from the formula of the drilling speed, and the life of the cutter is calculated from the formula of the wear rate of the cutter blade edge and the bearing, with the cutter penetration amount and the rotation speed as factors. The disk cutter is being replaced where it becomes.

In the case of crushing bedrock or gravel with a disc cutter, the rock quality and soil quality are investigated in advance, and the coefficient due to the effect of the cracks in the ground is added to the amount of intrusion of the cutter obtained under the condition that there are no cracks. Taking into consideration the optimum amount of cutter penetration.

[0007]

However, a large error is apt to occur due to variations in actual ground characteristics, which has a great influence on the cutter life and the excavation speed. That is, when the actual construction is started, the wear of the cutter may progress in a remarkably short time or the excavation speed may decrease, resulting in an increase in the cutter cost and a significant delay in the process. is there.

Further, since the ratio of the cutter cost to the total drilling cost is large, the drilling cost will inevitably increase as the number of times of exchanging the cutter increases. In the field, there is a permanent problem to extend the life of the cutter without lowering the excavation efficiency, or to improve the drilling efficiency.

Further, in the design of the excavator, a mechanical capacity is given a margin in consideration of an unexpected entry into the rock formation and an encounter with the rock formation having a strength higher than the design. If it is possible to improve the rippability (which is an index of the easiness of excavation of the rock), it will bring advantages such as reduction of mechanical power such as propulsion force of excavator and drive torque of disc cutter. .

In addition, in the case of the conventional open type TBM,
Dust is generated when the bedrock is crushed, which leads to a deterioration of the working environment and has other sanitary and environmental problems.

Therefore, the main problem of the present invention is to first
In addition to extending the life of the cutter, it is possible to reduce the excavation functional force compared with the conventional device by improving the drilling speed and secondly improving the ripperability artificially. , And to prevent dust during excavation and prevent deterioration of the working environment.

[0012]

In order to solve the above-mentioned problems, the present invention provides a method for crushing an excavated surface by a disk cutter,
A cutting groove or a crack was formed by ultra-high pressure water along the expected passage line of the disc cutter on this excavated surface, and the crushing was performed while the cutting edge of the disc cutter rolled on the cutting groove or the crack line. It is characterized by that.

In this case, the range of the injection pressure of the ultra-high pressure water is preferably 1000 to 3500 kgf / cm ² . Further, in the jet nozzle for jetting the super high pressure water, in order to prevent clogging of the jet nozzle due to the inflow of fine soil particles at the time of stopping the jet of the super high pressure water, even when the jet of the super high pressure water is always stopped It is good practice to continue drilling with a small amount of water spray. Further, by mixing a fine-grained abrasive in the ultra-high pressure water, it is possible to improve the efficiency of forming the cutting grooves or cracks.

As described above, in the case of the present invention, a cutting groove or a crack is formed in advance by ultra-high pressure water along the expected passage line of the disc cutter before the crushing by the disc cutter is performed. Therefore, the ground such as rock or gravel layer is likely to be crushed, and wear of the blade edge of the disk cutter is reduced, so that the cutter life is extended. Further, as a matter of course, the rock to be excavated is easily broken, so that the excavation speed is also improved. Further, since the rippability is improved by the artificially formed cutting grooves and cracks, the driving force of the excavator and the driving torque of the disc cutter can be reduced.

Further, in the open type TBM, since the dust is captured by the ultra-high pressure water jetted toward the excavation surface, the working environment is greatly improved.

In order to further clarify the action and effect of the ground excavation method according to the present invention, the destruction mechanism of the excavation method using the super high pressure water together will be described in detail below in comparison with the destruction mechanism using only the disk cutter. First, as shown in FIG. 13, a detailed description will be given of a crushing mechanism when the cutting edge 10a of the disk cutter 10 is penetrated into rock (“Study on drilling property of large diameter drilling machine”, 1978, 3). (See Ministry of Construction, Civil Engineering Research Institute). As shown in FIG. 14, generally, two stresses σ ₁ ,
When σ ₂ acts, normal stress σ and shear stress acting on an arbitrary inclined surface are expressed by the following equations (1) and (2).

[0017]

[Equation 1]

Microscopically, fracture is a phenomenon that occurs when the stress σ ₂ becomes larger than the tensile strength or when the shear stress becomes larger than the shear strength.
Since it is a value proportional to the principal stress from the Coulomb theory, the shear fracture is an angle of λ = π / 4−φ / 2 where φ is the internal friction angle of the Mohr-Coulomb equation in the above equation (2). appear.

On the other hand, as shown in FIG. 15, when the linear load P acts on the semi-infinite plate, the stress state at any point is given by the following equation (3) by Timoshenko and Goodier.

[0020]

[Equation 2]

Assuming that the fracture occurs on the plane forming an angle of λ _f with the direction of the maximum principal stress, the fracture line starting from the point r ₀ immediately below the loading point is always constant with the radiation centered on the loading point. It becomes a logarithmic helix with an angle λ _f . That is, it is expressed by the following equation (5).

[0022]

(Equation 3)

Further, from the above equations, the shear stress τ and the normal stress σ along the fracture line can be defined in the left and right directions as represented by the following equations.

[0024]

(Equation 4)

Maurer gives the following equation (8) because the ratio of the two stresses along the fracture line becomes constant from the above equations (6) and (7).

[0026]

(Equation 5)

This relationship is based on the maximum shear fracture line (λ _f = π /
In 4), τ. = Σ, and the stress is as shown in FIG.
As shown in (a), it changes along the fracture line and becomes 0 on the rock surface (θ = ± π / 2), and θ = ± (π / 2−λ
It becomes the maximum at _f ). Further, the maximum shear stress is generated just below the load. The fracture line of the crater shown in Fig. 16 (b) has a shear stress of 0 on the rock surface, so shear fracture occurs near the fracture zone along the fracture line and tensile fracture due to bending load occurs near the surface. Can be considered.

By the way, the minimum load required to generate craters when the cutter blade edge is pressed against the surface of the rock to penetrate it is called the threshold load. Since the penetration pressure of the cutting edge is related to this threshold load, the threshold load increases when the cutting edge wears and the contact area increases. As a study of the relational expression between the wear width of the cutting edge and the threshold load, there are experimental results by Maurer, M, C (The State of Mechanics Knowledge in Drillin
g, 8th symposium on Rock Mechanics AIME, University
of Minnesota, Sept., 1966, P.355). Berea sandstone with a tool with a cutting edge width of 1/2 in against the threshold load
The experiment shown in FIG. 17 shows the relationship between the wear width and the threshold load. The figure shows that craters can be formed in the area where the penetration force of the cutting edge is larger than the straight line in the figure, but in the area below that, the crater cannot be formed because only the cutting edge marks on the surface of the rock. It shows the reason why the threshold load is greatly increased by a slight abrasion, that is, the crushing efficiency is drastically lowered due to the abrasion of the cutting edge.

From the above description, the fracture mechanism when a vertical load is applied to the rock surface is clarified, and the reason why the threshold load increases and the drilling efficiency decreases when the cutting edge wears due to excavation is clarified. Becomes That is, in the case of fracture only by the disc cutter, the fracture occurs along the pseudo semi-elliptical shear fracture line due to the penetration force of the disc cutter acting perpendicularly to the excavation surface and from the tip of the cutting edge, and the threshold From the explanation of the load, it became clear that the breaking force is greatly influenced by the penetration force (penetration stress) transmitted from the tip of the cutting edge to the rock side.

By the way, in the case of the present invention, a cutting groove or a crack is formed at the penetration position by ultra-high pressure water immediately before the cutting edge is penetrated into the rock, and therefore, a fracture mechanism slightly different from the above-mentioned fracture mechanism is adopted. That is,
As shown in FIG. 11, since the cutting groove or the crack 14 is formed in advance prior to the crushing by the disc cutter, the cutting edge S of the disc cutter blade body 10a does not contact the rock or the like to be excavated or has contacted with it. As the cutting edge S
The penetrating force transmitted from the rock to the rock becomes a non-dominant contact state. The penetration force from the disc cutter is mainly the blade 10.
It is transmitted to the rock side from the contact points U between the side inclined surface of a and the shoulder of the cutting groove or the crack 14. When such a contact mode is adopted, as shown in FIG.
The vertical stress σ _N on the fracture line K due to the diagonal wedge penetration input P _U
And a shearing force τ along the breaking line K act, and the shearing force τ directly causes slip failure. That is, basically, the penetration force in the vertical direction does not act on the surface to be excavated, but the wedge penetration force P _U directly acts in an oblique direction from the cutting edge surface to push out the fractured portions 15, 15 on both sides sideways. And crush. Therefore, the crushing can be effectively performed at the point where the shear force directly acts, and as shown in the figure,
The blade edge S does not come into contact with rocks or the like, or even if it comes into contact, the penetration force acting on the blade edge portion is small, so that the blade edge wear is reduced.

Further, in the present invention, the tip of the cutting edge 10a does not directly contribute to the breakage. Therefore, the phenomenon such as the increase of the threshold load due to the wear of the cutting edge as described above does not occur or is small, so that the excavation performance can be maintained for a long period of time.

On the other hand, the excavator according to the present invention for carrying out the excavating method comprises one or a plurality of disc cutters in the excavating head portion, and at least the excavating head portion rotates around the axis in the excavating direction to remove the disc cutters. In an excavator that rolls to crush the excavation surface, a part of or all of the disk cutter is targeted, and during the crushing of the excavation surface by the disk cutter, a planned passage line of the disk cutter with respect to the excavation surface It is characterized in that an ultra-high pressure water jet device for forming a cutting groove or a crack along the line is provided.

In this case, in the above-mentioned ultra-high pressure water injection device, in order to prevent clogging of the injection nozzle due to the inflow of fine soil particles when the injection of the ultra-high pressure water is stopped, an opening / closing lid can be provided at the injection port. In addition, it is possible to prevent clogging of the injection nozzle by controlling the rotational position of the injection nozzle portion with a spherical shape. On the other hand, when the disc cutter has a plurality of blades on the outer periphery of the cutter saddle,
The ultra-high pressure water jet device is provided for each of the blade bodies.

Also, like TBM and shield machines,
In a structure in which a ground contact portion provided with a plurality of disk cutters is rotatable about a central axis, in a disk cutter group arranged at a relatively long distance position with reference to the rotation center axis of the ground contact portion. It is also possible to provide the ultra-high pressure water injection device only for the above. The disk cutter group arranged relatively far from the central axis of rotation has a relatively long rolling distance per one rotation of the cutter head, so that the excavating load is larger than that of the disk cutter on the center side. The degree of wear of the cutting edge also increases. Therefore, in general, make sure that the load on the disc cutter is evenly distributed,
Although the number of disc cutters attached to the outer peripheral side is increased, the excavating load can be adjusted by forming cutting grooves or cracks in the present invention, and thus the disc cutter group on the outer peripheral side having a large excavating load as described above. It is possible to make the excavation load uniform by installing ultra-high pressure water injection equipment only in the area.

[0035]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 1 is a schematic view of a TBM adopting the cutter structure according to the present invention, and FIGS.
FIG. 7 is an enlarged view of a disc cutter unit. As shown in FIG. 1, a tunnel excavator 1 is provided with a cutter head (excavation head according to the invention) 2 on the front surface of a machine body, and a plurality of disc cutters 1 attached to the surfaces of the cutter heads 2.
The ground is continuously crushed by 0, 10 ... As shown in FIGS. 2 and 3, the disk cutter 10 has a cutter structure having a blade body 10a having a wedge-shaped cross section formed on the outer periphery of a cutter saddle 10b, and is fixed to the surface of the cutter head 2. It is rotatably attached to the cutter attachment base 11 via a bearing 13. When excavating the ground, the thrust head 8 provided in the excavator 1 applies a propulsive force in the rock contact direction to the cutter head 2 while the cutter head 2 is rotated by the cutter driving motor 24. Rotate around the axis of excavation. The disk cutters 10, 10 ... Roll in the circumferential direction, so that the blade 10a crushes bedrock, gravel and the like.

On the other hand, the body portion of the tunnel excavator 1 is composed of a front body portion 3 following the cutter head 2 and a rear body portion 4 and can be bent at a connecting portion between the front body portion 3 and the rear body portion 4. The middle bent portion 5 is formed to allow curved construction. The excavation scraps scraped off by the disk cutters 10, 10 ... Are taken into the cutter chamber 25, and are discharged to the ground side by the mud pipe 21 together with the water that has flowed in through the water supply pipe 20.

The front body 3 is provided with front grippers 6 and 6, and the main gripper 7 is provided on the rear side.
The front body 3 and the main gripper 7 are connected by a thrust jack 8. The tunnel machine 1 is propelled by releasing the support of the pit wall by the front gripper 6 and extending the main gripper 7 to take a reaction force against the pit wall, extending the thrust jack 8 and advancing the front body part 3. To excavate. When the excavation for one cycle length is completed, the front gripper 6 is extended to apply a reaction force to the pit wall, and the pit wall support by the main gripper 7 is released, and the thrust jack 8 is contracted, whereby the rear trunk portion 4 is pulled. Move forward to move forward.
The segment 23 is assembled by the erector 22 behind the tunnel excavator 1.

In the tunnel machine 1 of the present invention, FIG.
As shown in FIG. 3 and FIG.
Immediately before the rock crushing is performed by the disk cutter 10 in the vicinity of the locations where 0, 10 ... Are arranged, ultra-high pressure water is jetted toward the planned passage line of the disk cutter 10 to cut the excavated ground surface. An ultra-high pressure water jet device 12 is provided for forming grooves or crevices. As shown in FIG. 4, the ultra-high pressure water jetting device 12 includes a nozzle head 1
2b, an injection nozzle 12a fixed to the tip of the nozzle head 12b, and preferably a control valve 12c for performing on / off control of ultra-high pressure water. The nozzle diameter of the jet nozzle 12a is usually about 0.1 to 1.0 mm, and diamond is used as the material.

Further, the ultra-high pressure water jetting device 12 has all the disc cutters 10 and 10 provided on the cutter head 2.
Can be provided for ... Or can be provided only for a part thereof. As an example of the case of providing this part group, for example, each disk cutter 1
In order to prevent the deviation of the degree of wear between 0, 10, ..., It can be provided only for the disk cutter group arranged at a relatively long distance position with respect to the rotation center axis of the cutter head 2. Further, the disc cutter 10 has two blade bodies 1.
In the case of having a double disk structure having 0a, 10a or more blade bodies, as shown in FIG. 5, for each blade body 10a, 10a ...
12 is provided.

As another mode of the ultra-high pressure water jetting device 12, in addition to the method of mounting the cutter mounting base 11 as a supporting base as shown in the figure, a groove hole is formed in the cutter mounting base 11 to directly spray water. The nozzle 12a can also be attached.

Further, it is also possible to supply an abrasive to the nozzle head 12b portion and jet the abrasive together with the ultra-high pressure water onto the excavated surface. In addition, as the abrasive, silica sand (about 60 mesh) and garnet (60-100) are generally used.
In addition to (mesh)), abrasive materials such as alumina, cast iron grids, corundum, etc. are used.

On the other hand, an ultrahigh pressure water unit 9 is installed in the already-excavated tunnel of the tunnel excavator 1 of the present invention. The ultrahigh pressure water produced by the ultrahigh pressure water generation unit 9 is sent to the ultrahigh pressure water injection device 12. The ultra high pressure water unit 9
Is composed of a hydraulic unit 30, a water supply unit 31, a booster (pressure booster) 32, and an accumulator 33,
The hydraulic oil discharged from the hydraulic unit 30 moves the piston in the booster 32 to the left and right to compress the water in the water chamber into ultra-high pressure water. Further, the pressure of the super high pressure water is kept constant by interposing the accumulator 33. Normally, the ultra-high pressure water unit 9 can generate 1000-4000 kgf / cm ² of ultra-high pressure water.

As shown in FIG. 2, the crushing of a rock bed or the like by the disc cutter 10 is performed by the disc cutter 10 as shown in FIG.
Immediately before crushing with the disk cutter 10
The ultra high pressure water jetted from the ultra high pressure water jetting device 12 collides with the expected passage line of the cutting water to cause a cutting groove or a crack 14 on the excavation surface.
Is formed so that the crushing is performed while the cutting edge 10a of the disk cutter 10 passes over the cutting groove or the crack 14 line.

As the installation and injection mode of the ultra high pressure water injection device 12, as shown in FIG. 2, the ultra high pressure water injection device 12 attached to the cutter mount 11 vertically extends to the excavation surface. Can be made to collide,
Further, as shown in FIG. 6, it is possible to collide with an inclination angle. Further, the ultra-high pressure water jetting device 12 can be attached to the face plate of the cutter head 2 and jetted to the excavation surface. Further, as shown in FIG. 8, it is also possible to attach the ultra-high pressure water jetting device 12 at a position laterally offset from the line of the blade 10a of the disc cutter 10 and jet from the diagonal position to the planned passage line. it can.

By the way, the excavation method using the above-mentioned ultra-high pressure water is basically intended for a rock bed, a gravel layer, etc., and when the soft layer is rushed during excavation, the ultra-high pressure water is also used together. You may excavate only with a disk cutter without it. When the injection of ultra-high pressure water is stopped, muddy water or fine soil particles in the mud may enter the injection nozzle 12a and cause clogging. It is desirable to excavate the ground while continuously injecting the above water. In addition, the injection nozzle 12a
Nozzle clogging may be prevented by providing an openable and closable lid. Further, as shown in FIG. 9, the injection nozzle 26 is a sphere, and its rotational position can be controlled by hydraulic pressure or hydraulic pressure (not shown), and it is positioned at the rotational position shown in FIG. Then, the super high pressure water is injected, and when the injection is stopped, as shown in FIG.
The nozzle opening may be closed inside by rotating the spherical nozzle 26. Note that FIG. 9 and FIG.
In the example of the nozzle structure of No. 0, the washing water flow passage 27 is separately provided so that the super high pressure water passage can be washed by the backflow water when the injection is stopped.

In the above embodiment, the present invention has been described by taking the tunnel excavator as an example. However, the present invention can be applied to other works such as chipping work for rocks and concrete surfaces, peeling work for pavement surfaces, etc. It can also be applied to cutting, crushing, and peeling work using other disc cutters.

[0047]

As described above in detail, according to the present invention, the cutting groove or the crack is formed in advance before the crushing by the disc cutter, so that the life of the cutter can be extended. Further, since rocks and the like are easily crushed, the drilling speed is improved, and the excavation functional force can be reduced as compared with the conventional device. Furthermore, various advantages are brought about, such as being able to suppress dust during excavation and prevent deterioration of the working environment.

[Brief description of drawings]

FIG. 1 is a schematic view of a tunnel excavator.

FIG. 2 is a side view of a disc cutter portion structure according to the present invention.

FIG. 3 is a plan view of a disc cutter portion structure according to the present invention.

FIG. 4 is a detailed view of an ultra-high pressure water injection device.

FIG. 5 is a plan view of a double disk structure.

FIG. 6 is another ultra-high pressure water injection mode diagram.

FIG. 7 is another ultra-high pressure water injection mode diagram.

FIG. 8 is a vertical cross-sectional view at the time of jetting ultra-high pressure water in another nozzle structure example.

FIG. 9 is a vertical cross-sectional view of another nozzle structure example when the ultra-high pressure water is stopped.

FIG. 10 is another ultra-high pressure water injection mode diagram.

FIG. 11 is a conceptual diagram of crushing in the case of the present excavation method.

FIG. 12 is an enlarged schematic view of a crushed portion.

FIG. 13 is a conceptual diagram of crushing using only a disc cutter.

FIG. 14 is an explanatory diagram of a destruction mechanism by only the disc cutter.

FIG. 15 is an explanatory diagram of a destruction mechanism only by the disc cutter.

FIG. 16 is an explanatory diagram of a destruction mechanism only by the disc cutter.

FIG. 17 is an explanatory diagram of a threshold load.

[Explanation of Codes] 1 ... Tunnel excavator, 2 ... Cutter head, 3 ... Front body,
4 ... rear torso part, 5 ... middle bent part, 6 ... front gripper, 7
... Main gripper, 8 ... Thrust jack, 9 ... Ultra high pressure water generating unit, 10 ... Disk cutter, 11 ... Cutter mount, 12 ... Ultra high pressure water injection device, 12a ... Injection nozzle, 12b ... Nozzle head, 12c ... On-off valve ,
30 ... Hydraulic unit, 31 ... Water supply unit, 32 ... Booster, 33 ... Accumulator

Claims (9)

[Claims] 1. During crushing of an excavated surface by a disk cutter,
A cutting groove or a crack was formed by ultra-high pressure water along the expected passage line of the disc cutter on this excavated surface, and the crushing was performed while the cutting edge of the disc cutter rolled on the cutting groove or the crack line. An excavation method characterized by the above. 2. The injection pressure of the ultra-high pressure water is 1000 to 350.
The excavating method according to claim 1, wherein the excavating method is 0 kgf / cm ² . 3. In the jet nozzle for jetting the ultra-high pressure water, in order to prevent clogging of the jet nozzle due to inflow of fine soil particles when the jet of the super-high pressure water is stopped, the jet nozzle is used only when the jet of the super-high pressure water is stopped. 3. The excavation method according to claim 1, wherein the excavation is performed while constantly ejecting a small amount of water. 4. The excavating method according to claim 1, wherein the efficiency of forming the cutting groove or the crack is improved by mixing an abrasive in the ultrahigh pressure water. 5. An excavation system comprising one or a plurality of disc cutters in an excavation head part, wherein at least the excavation head part rotates about an axis in the excavation direction to roll the disc cutters to crush the excavation surface. In the machine, during the crushing of the excavation surface by the disk cutter for a part or all of the disk cutter, an ultra high pressure for forming a cutting groove or a crack along the expected passage line of the disk cutter with respect to the excavation surface An excavator equipped with a water injection device. 6. The excavator according to claim 5, wherein in the ultra-high pressure water injection device, a lid that can be opened and closed is provided at the ultra-high pressure water injection port to prevent clogging of the injection nozzle when the injection is stopped. 7. The excavator according to claim 5, wherein in the ultra-high-pressure water jetting device, the jetting nozzle portion is a sphere and its rotational position is controlled to prevent the jetting nozzle from being clogged when the jetting is stopped. 8. The excavator according to claim 5, wherein when the disc cutter has a plurality of blades on the outer periphery of the cutter saddle, the ultra-high pressure water jetting device is provided for each blade. 9. An excavating head section having a plurality of disc cutters, wherein the ultra-high pressure water jetting device is provided only for a group of disc cutters arranged at a long distance relative to a rotation center axis. Item 5-8 excavator.