DESCRIPTION Construction method of underground diaphragm wall and excavator for the underground diaphragm wall BACKGROUND OF THE INVENTION Technical Field The present invention relates to a construction method of underground diaphragm wall and excavator for the underground diaphragm wall. For details, the construction method of the underground diaphragm wall and excavator for the underground diaphragm wall which can construct a highly homogeneous quality underground diaphragm wall easily and effectively for a short term.

Description of the Related Art In the past, as a concise method to construct a soil-cement underground-diaphragm wall, a general construction method is that after excavating underground by using a multi-shafts earth auger, agitating and blending excavated soil with solidifier liquid in-situ condition, a core beam is built up.

However, in this conventional peristyle construction method, if a depth of an underground wall increases, a water leak from a portion which is not overlapped enough, and a difficultness of inserting of the steel beam caused by excessive skew hole have occurred. Further, constrain that the steel beam position is limited to a center of the auger has occurred.

The auger's height above the ground surface needs more than a depth of the underground wall, and when the depth of the underground becomes deep, turnover accidents while its moving have often happened in

the past. Therefore, when the underground wall is deeper than 30 m, a method which adds the auger is mainly used, and in this case, operating efficiency is fallen.

Further, because soil from the deepest part to the ground is not agitated up and down direction, even strength cannot be obtained since the soil quality is heterogeneous. Therefore, it has not been able to construct ideal homogeneous underground wall.

To solve above-mentioned problems of conventional peristyle construction method, in Japanese Patent Publication No. 8G729 of 1994, a construction method of a soil-cement underground diaphragm wall is disclosed. In the method, an excavator with a core beam installed a rotatable endless chain with cutter bits is used. After the endless chain with cutter bits is inserted vertically in the ground, the excavator moves in horizontal direction without moving the core beam up and down, a solidifier liquid is discharged from predefined part, and the soil-cement underground diaphragm wall is constructed.

The construction method of the underground diaphragm wall disclosed in above-mentioned patent document excels in solving various problems which the prior arts have. However, the method also has some problems as described below.

At first, a structure of the excavator is that two hydraulic cylinders installed up and down at frame above the ground moves horizontally while putting the core beam in the ground with cantilevering. Therefore, a big deflection occurs at the bottom of core beam by resistance force. An operation to mend this deflection is needed. This operation requires enough experience that a skilled driver combines intricately various

operations like a normal rotation and reverse rotation of a drive motor and pulling and pushing movement of the core beam while watching deflection at an inclinometer attached to the core beam. Further, the operation is very difficult to automate, and the driver is always in tense during the operation.

After constructing the underground diaphragm wall, a redundant excavation for the refuge of the core beam not to be affected the discharged cement solidifier liquid is required. The required length for the refuge excavation depends on the wall depth, thickness, soil condition and solidifier liquid condition of the construction. Usually, in case of standard soil hardness, with the depth is from 30 to 40 m, it is required 2 m not to be affected by the cement hardening of solidifier liquid, and it takes about 2 hours. Therefore, it costs a lot for the redundant excavation.

The present invention is invented to solve above-mentioned prior art's problem and provides the construction method of the underground diaphragm wall and an excavator for the underground diaphragm wall that can efficiently construct high quality underground diaphragm wall for short period by easy operation.

SUMMARY OF THE INVENTION The invention according to claim 1 relates to a construction method of underground diaphragm wall wherein, in a construction method of underground diaphragm wall, which a core beam (4) winded an endless chain (17) with a cutter bits is installed to a movable main body on the ground and the core beam is moved while excavating ground and discharging a solidifier liquid into the ground with the core beam is inserted

in the ground, a movement of said core beam includes a motion which makes said core beam turn centrally a supporting point installed said movable body.

The invention according to claim 2 relates to the construction method of underground diaphragm wall described in claim 1 wherein, a turn movement of said core beam includes a movement which makes a bottom part of said core beam turn to forward direction with said supporting point position fixed and a movement which makes said supporting position move parallel to the ground surface while turning said bottom part of the core beam to backward direction.

The invention according to claim 3 relates to an excavator for the underground diaphragm wall wherein, an excavator for underground diaphragm wall is that a flame (3) is installed at a movable base machine (2) and a core beam (4) winded endless chain with cutter bits is installed to be able to move relatively to the said flame, the said excavator has a main leader (7) which can move along the said flame from side to side and a sub leader (9) which can move up and down relatively to the said main leader, and the said core beam is installed to be able to turn relatively to the said sub leader.

The invention according to claim 4 relates the excavator for the underground diaphragm wall described in claim 3 wherein, a drive section flame (11) is installed to the said sub leader to be able to turn via a pin (12), and the upper end of the said core beam is connected to the said drive section flame.

The invention according to claim 5 relates to the excavator for the underground diaphragm wall described in claim 4 wherein, a motor (13) is

installed inside the said sub leader, and a pinion (14) installed at an output shaft of the said motor is engaged with a gear (15) installed at the said drive section flame.

BRIEF DESCRIPTION OF THE DRAWINGS FIG 1 is a side view of an excavator for the underground diaphragm wall in this invention.

FIG 2 is a front view of the excavator for the underground diaphragm wall in this invention.

FIG 3 is an expanded cross-sectional view of A-A line of Figure 1.

FIG 4 is a side view showing an initial condition of an underground wall construction process by the present invention.

FIG 5 is a schematic diagram showing a first process of the underground wall construction process by the present invention.

FIG 6 is a schematic diagram showing a second process of the underground wall construction process by the present invention.

FIG 7 is a schematic diagram showing a third process of the underground wall construction process by the present invention.

FIG 8 is a schematic diagram showing a fourth process of the underground wall construction process by the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, preferred embodiments of the construction method of the underground diaphragm wall and excavator for the underground diaphragm wall which relate to the present invention is explained by referring to the drawings. Figure 1 is a side view of the excavator for the

underground diaphragm wall in this invention, Figure 2 is a front view of the excavator for the underground diaphragm wall in this invention, and Figure 3 is an expanded cross-sectional view of A-A line of Figure 1.

The excavator for the underground diaphragm wall which relates to the present invention has a base machine 2 which is movable by a crawler 1 located at the lower part of the base machine 2, a frame 3 installed to the base machine 2 and a core beam 4 which is installed so that it can move parallel to the frame 3.

The frame 3 has two horizontal frames 31 and 32 installed on a parallel each other and more than two longitudinal frames 33 or inclined frames which connect between these horizontal frames 31 and 32.

The upper horizontal frame 31 of the frame 3 is interconnected with the base machine 2 via a frame holding backstay 5, and an angle of gradient of the frame 3 to the base machine 2 can be adjusted by telescopic motion of a hydraulic cylinder 6 which is installed under the frame holding backstay 5.

A main leader 7 is installed to the frame 3.

The main leader 7 moves from side to side to the frame 3 and makes a drive section frame 11 goes up and down in vertical direction via a sub leader 9.

Traverse slide parts 34 and 35 are installed parallel to each other with a space on a backside of the frame 3. The upper traverse slide part 34 is attached to the upper horizontal frame 31 to be able to slide transversely, and the lower traverse slide part 35 is attached to the lower horizontal frame 32 to be able to slide transversely.

Hereby, the main leader 7 is to be able to slide from side to side

along the frame 3 with the upper and the lower part of the main leader 7 held by the frame 3.

It is normal that the heavy structures such as the main leader 7, sub leader 9 and drive section frame 11 support their weight at the under horizontal frame 32 of the frame 3. Therefore, usually, the main leader 7 is slid by telescopic motion of a hydraulic cylinder 8 installed along the lower horizontal frame 32. More than one hydraulic cylinder 8 can be installed.

The sub leader 9 is attached to the main leader 7.

Slide guides 71 which extend linearly to up and down are installed to both sides of the main leader 7. The sub leader 9 is installed to be able to slide up and down along the slide guide 71 via both slide guide holding members 91 located on the backside of the sub leader 9 (refer to Figure 3).

Hereby, the sub leader 9 can slide up and down along a central axis of the main leader 7.

The sub leader 9's movement up and down is performed by a telescopic motion of a pair of hydraulic cylinders 10 which are installed at the both sides of the central axis of the main leader 7.

The drive section frame 11 is installed to be able to turn on the sub leader 9 via a pin 12.

A motor 13 is located in the sub leader 9, and a pinion 14 is installed on an output shaft of the motor 13. Further, a gear 15 is installed on the drive section frame 11, and the pin 12 penetrates a center of the gear 15.

A pinion 14 and a gear 15 are engaged, which enables the rotating force of the motor 13 to be transmitted from the pinion 14 to the gear 15, and the drive section flame 11 rotates along with the gear 15 rotating.

The lower part of the drive section flame 11 is connected to the upper

end of the core beam 4 via a flange 16.

The core beam 4 is winded an endless chain 17 with cutter bits, which constitutes an endless chain cutter. This endless chain cutter has the same structure with publicly known underground diaphragm wall excavator. Its lower part is omitted in figures.

The endless chain 17 rotates by the force transmitted from the rotation of a hydraulic motor 18 installed on top part of the drive section flame 11 via speed reducer (which is not shown in figures) and others inside drive section flame.

Inclinometer (which is not shown in figures) to measure the degree of inclination of a core beam is installed in the center of the core beam 4.

The inclinometer is generally used to measure the deflection angle toward the moving direction of the core beam 4 and the inclination angle of the wall at the same time, and is the publicly known structure which is adopted in other diaphragm wall construction methods.

In this invention, it is enough to install at lease one inclinometer at the lower end of the core beam 4, however it is possible to install plurality of inclinometers at places from the upper end to the lower with appropriate spaces.

Inside the core beam 4, a nozzle which is connected to the outside supple source of solidifier liquid like cement milk is installed to discharge solidifier liquid into the ground. (The nozzle is not shown in figures.) In this invention, this nozzle is installed at two or more places of the lower end and the middle part of the core beam 4. The concrete position to be installed the nozzle in the middle part is decided by the depth of constructed underground diaphragm wall and the rotating angle of core

beam.

The method to construct underground diaphragm wall using underground diaphragm wall excavator with the above structures is explained as follows.

Firstly, a hole with the predetermined depth is excavated at the spot where underground diaphragm wall is going to be constructed. After inserted the core beam 4 into this hole, the core beam 4 is installed to the main body with the movable base machine 2 (see the figure 4). The upper end of the core beam 4 is installed to the base machine 2 via the drive section flame 11 and the flame 3.

Next, while endless the chain 17 with the cutter bits is rotated by the driving hydraulic motor 18, the core beam 4 is turned at the pin 12 of its supporting point at predetermined angle ct to one direction (which is called a forward direction for convenience) by the driving motor 13. The underground diaphragm wall can be constructed by discharging solidifier liquid slurry like cement milk from the nozzle, which is installed at the lower end of the core beam 4, into the ground, while agitating and excavating the ground.

The main leader 7 remains to be stopped during the above performance.

The predetermined angle cr is not limited particularly in this invention, however depending on the hardness of soil, it is presumed that the core beam 4 is repeatedly turned in the range of 7. 5° to 15° for a standard working time if its depth is from 30 to 40 m.

Figure 5 is a schematic view showing the construction process of underground diaphragm wall (the first process) by the above performance.

Underground diaphragm wall is constructed in the sectoral part with hatching by the first process.

In figure 5, it is indicated A as the position of the pin 12 as a turning supporting point of the core beam 4, B as the position of the lower end of the core beam 4 before the turning performance, C as the position of the lower end of the core beam 4 after the turning performance, LI as the depth to insert the core beam 4 from the ground surface GL, and L2 as the height from the ground surface GL to the pin 12 respectively. If it is not explained particularly in the following figures, the same symbols are used with the same meanings.

Next, while an output shaft is turned in the opposite direction to the first process by the driving motor 13 and then the lower end of the core beam 4 is turned at a predetermined angle a in the opposite direction to the first process, the hydraulic cylinder 8 is extended, the main leader 7 is moved horizontally along with the flame 3, which enables the upper end of the core beam 4 to move parallel to the ground surface GL. This moving distance is equal to horizontal moving distance of the lower end of the core beam 4 in the first process.

During the above performance of the core beam 4, slurry is discharged from the nozzle on the middle part (point H in Figure 6) of the core beam 4.

Figure 6 is a schematic view showing the construction process of underground diaphragm wall (the second process) by the above performance.

Underground diaphragm wall is constructed in the inverted triangle part with cross hatching by the second process.

In figure 6, it is indicated D as the position of the pin 12 as a turning

supporting point of the core beam 4 after moving, C as the position of the lower end of the core beam 4, which is consequently moved to E. E as the next start position of the lower end of the core beam 4 after the turning performance, X1 as the moving distance of the main leader 7, and H as the position to discharge slurry respectively.

Figure 7 is a schematic view showing the construction process of the underground diaphragm wall (the third process) by the above performance.

The underground diaphragm wall is constructed in the partial sector with cross hatching by the third process.

While the core beam 4 is turned at the pin 12 of its supporting point at a predetermined angle 2 a in the forward direction by the driving motor 13 and then the ground is agitated and excavated, at the same-time solidifier liquid slurry like soil cement is discharged from the nozzle installed at the lower end of the core beam 4 to construct underground diaphragm wall.

The main leader 7 remains to be stopped during the above performance.

In figure 7, it is indicated D as the position of the pin 12 as a turning supporting point of the core beam 4, E as the position of the lower end of the core beam 4 before the turning performance, F as the position of the lower end of the core beam 4 after the turning performance, and G as the lowest point which the lower end of the core beam 4 draws and the point on the vertical line of the turning center D respectively.

With the position of lower end of the core beam 4 fixed, the hydraulic cylinder 8 is extended, the main leader 7 is moved horizontally along with the flame 3, which enables the upper end of the core beam 4 to move parallel

to the ground surface GL. At the same time, solidifier liquid slurry like soil cement is discharged from the nozzle at the lower end of the core beam 4 to construct underground diaphragm wall.

Figure 8 is a schematic view showing the construction process of the underground diaphragm wall (the forth process) by the above performance.

The underground diaphragm wall is constructed in the inverted triangle part with cross hatching by the forth process.

In figure 8, it is indicated J as the position of the pin 12 as a turning supporting point of the core beam 4 after moving, F as the position of the lower end of the core beam 4 respectively.

The underground diaphragm wall with the area of (horizontal distance from point A to point J) x (depth L1) is constructed by the above processes from the first to the forth.

Strictly speaking, it is short of the depth of (L1-L3) between intersecting point N of arc BC and arc EG and line BG, but this can be solved by excavating the short depth of L5 which is taken into consideration beforehand.

Although deflection is arouse by the resistance reaction force during the above processes, if the degree of this deflection becomes large, it can be easily mended by switching the turning direction from forward to backward or vice versa.

Because the performance of the core beam 4 is simple turning one, the deflection of core beam edge can be easily estimated from the soil's resistance reaction force which is added to the entire core beam, and the turning angle velocity.

Since it can be assumed the deflection line of core beam's entire

length from one point of deflection on the lower end of the core beam, it is enough to have at least one inclinometer, and the system can be simplified substantially.

In figure 8, after the predetermined area of the underground diaphragm wall finishes to be constructed, the core beam 4 is turned at the pin 12 of supporting point at only minute angle/3 while discharging not hardening liquid like bentonite, which is changed from the solidified liquid, from the lowest end of the core beam 4. The entire core beam 4 is stopped to move at the line of J-K away from soil cement wall. The degree of minute angle 3 is not particularly limited, but for example it is not more than 5°.

This invention can prevent bad effects, for example, cement solidifier liquid attaches to the core beam 4 by leaking from cement solidified substance (left part of the line of J-F) which is solidifying after the construction.

The conventional construction method requires around 2 m for refuge distance, and it takes about 2 hours to finish the work. This method is efficient since the core beam 4 can refuge from the cement solidified finishing line of J-F at the minute angle/3, especially from the lower part to be required to refuge. And also the working time can be shortened largely.

As explained in detail above, the construction method of the underground diaphragm wall and excavator for the underground diaphragm wall thereof in this invention excels in workability and safety during the performance since simple operating method makes it possible to excavate and to construct underground diaphragm wall continuously.

Moreover, this invention can construct the continuous and seamless underground diaphragm wall and can obtain homogenized wall even if the soil is heterogeneous.

This method can also simplify measurement system of deflection of core beam, mend the deflection easily, and reduce largely the construction time and cost which is required for refuge excavation.