BACKGROUND OF ART
The present invention relates to underground continuous wall building
method and apparatus for building a variety of continuous walls in the ground for
water cutoff purpose, reinforcing purpose and other purposes.
As a technique for building an underground continuous wall, there
has been conventionally known a method according to which a chain cutter is vertically
mounted on a running carriage (e.g. a base machine of a crawler crane), the running
carriage is moved in a transverse direction while the cutter is rotated, thereby
excavating a continuous trench of a fixed width, and a continuous wall is built
by pouring a wall material such as cement or concrete into this continuous trench
and solidifying it therein or by inserting a concrete panel therein (refer to Japanese
Unexamined Patent Publication Nos. 5(HEI)-280043 and 5(HEI)-280044).
The cutter is constructed such that an endless chain is fitted between
upper and bottom ends of a cutter post which is a vertically long boxlike frame,
and a continuous trench Gis excavated by a multitude of excavating blades provided
at the outer surface of the chain.
However, according to this technique, only vertically extending continuous
walls can be built. Therefore, such walls cannot have a water cutoff function along
vertical direction as cutoff walls, but can only be used as cutoff walls along horizontal
Thus, in the case that a water cutoff function along vertical direction
is required, the ground must be filled up after being excavated to built a horizontal
cutoff wall or a vertical wall must be built up to an impermeable bed. However,
such techniques are poor in performance and high in cost.
Another technique for building an underground continuous wall is known
from EP 0 188 282, relating to a system of forming a region in the ground where
underground water is kept from entering. Specifically, a region is defined by a
rock layer 8 and sealing walls 2. Underground water in the defined region is drawn
out by a vacuum pump 6. The sealing wall 2 is formed by injecting a mixture of bentonite,
filler and cement, or mixing of solid, asphalt basis into the ground.
Accordingly, it is an object of the present invention to provide an
improved underground continuous wall building method capable of easily building
a cutoff wall having a water cutoff function along vertical direction as well as
multi-purpose underground continuous walls.
This object is solved with an underground wall building method according
to claim 1 or 4, the features in the respective preambles of which are disclosed
in EP-A-0 577 430. Further embodiments are set forth in the sub claims.
BRIEF DESCRIPTION OF THE DRAWINGS
BEST MODES FOR CARRYING OUT THE INVENTION
- FIG. 1 is a side view showing the overall construction of an excavator as a
building apparatus according to an explanatory example of the invention;
- FIG. 2 is a front view of a chain cutter of the excavator;
- FIG. 3 is a portion of a first roof wall built according to a method according
to a first embodiment of the invention for building a repair roof of a radioactive
waste stockroom as a first variation of a continuous wall building method using
the above excavator;
- FIG. 4 is a section showing a state where a second continuous trench is excavated
according to the above method;
- FIG. 5 is a section of a roof completed according to the above method;
- FIG. 6 is a section showing a state where a reinforcement for a bank wall is
built as a second embodiment;
- FIG. 7 is a section showing a state where a lower cutoff wall is built at the
time of building a common trench as a third embodiment;
- FIG. 8 is a section showing a state where a liquefaction prevention ground is
built as a fourth embodiment;
- FIG. 9 is a section showing a state where a bank protection wall is built as
explanatory example not covered by the appended claims;
- FIG. 10 is a section showing a state where the bank protection wall has been
washed out to be exposed to the outside;
- FIG. 11 is a section showing a state where a cutoff wall is built to prevent
the leakage from a river side to a land side as a further explanatory example;
- FIG. 12 is a section showing a state of a slip destruction of an embankment
as an explanatory example;
- FIG. 13 is a section showing a state where a reinforcement wall a further explanatory
example is built in an embankment to prevent this slip destruction;
- FIG. 14 is a section showing a state where a reinforcement wall a further explanatory
example is built in a foundation portion of the embankment;
- FIG. 15 is a section showing a state where a reinforcement wall a further explanatory
example is so built as to extend over the embankment and its foundation portion;
- FIG. 16 is a section showing a state where a conical continuous trench is excavated
in the ground as a method for building a conical cutoff roof in the ground as a
- FIG. 17 is a section showing a state where a conical cutoff roof and a cylindrical
side wall are built according to the above method;
- FIG. 18 is a section showing a state where an inverted conical continuous wall
and a conical continuous wall are built at upper and lower sides of the underground
as a method for building a conical cutoff bottom wall in the ground as a sixth embodiment;
- FIG. 19 is a section showing a state where pit excavation is performed with
a conical continuous wall used as a cutoff bottom wall according to the above method;
- FIG. 20 is a section showing a state where a cutoff bottom wall for a pit excavation
area or liquefaction prevention area is built in the ground as a further explanatory
Embodiments of the invention and explanatory examples are described
with reference to the accompanying drawings.
FIG. 1 shows an overall construction of an excavator (continuous wall
building apparatus) for excavating a continuous trench which serves as a base of
an underground continuous wall.
This excavator is basically constructed such that a chain cutter 2
is mounted on a running carriage (e.g. a base machine of a crawler crane) 1 capable
of running by itself. A continuous trench G of specified length is excavated by
moving the cutter 2 in a transverse direction while rotating it with the cutter
2 placed in a hole dug by a suitable means such as a hydraulic shovel.
The cutter 2 is, as shown in FIG. 2, constructed such that an endless
chain 6 is fitted between a drive wheel (sprocket) 4 provided at an upper end of
a cutter post 3 which is a vertically long boxlike frame and a driven wheel (pulley)
5 at a bottom end thereof and a multitude of excavation blades 7 are provided on
the outer surface of the chain 6 to excavate the trench G.
The cutter 2 is mounted on the running carriage 1 as follows.
As shown in FIG. 1, a main frame 8 is mounted on the running carriage
This main frame 8 has its bottom and upper ends supported on the running
carriage 1 via a horizontal shaft 9 and an expandable backstay 10 comprised of a
hydraulic cylinder, respectively. The main frame 8 is inclinable about the horizontal
shaft 9 according to the expansion and contraction of the backstay 10, i.e. an inclination
(&thetas;) thereof with respect to a horizontal plane is adjustable.
A leader 11 and a slide frame 12 are mounted on the front surface
of the main frame 8 and on the upper end of the cutter 2 (cutter post 3), respectively.
This slide frame 12 is movably mounted on the leader 11 upward and downward.
Identified by 13 is a hydraulic cylinder provided between the leader
11 and the slide frame 12 to move the slide frame 12 upward and downward. The slide
frame 12 (cutter 2) moves upward and downward as the cylinder 13 expands and contracts,
thereby adjusting an excavation depth.
In this way, the excavator is constructed, such that the cutter 2
is obliquely mounted on the running carriage 1 and the inclination (&thetas;) thereof
Next, there is described methods according to which a continuous trench
is excavated using this excavator and a variety of underground continuous walls
are built on the basis of this excavated continuous trench.
A. Repair of an Underground Stockroom for Radioactive Wastes as a first
embodiment of the invention (see FIGS. 1, 3 to 5)
If an underground stockroom 14 for radioactive wastes as an underground
construction becomes decrepit, there is a likelihood that radioactive components
leak to the ground surface by being mixed in rainwater.
Accordingly, in order to prevent this leakage, a repair roof is constructed
above the stockroom 14 in the following procedure.
It should be noted that the roofs R1, R2 can be so built as to cross.
In such a case, the roof presser R3 is not necessary.
In this way, the roof R of the stockroom 14 can be easily built at
the ground surface side at a reduced cost and for a short time, thereby preventing
the leakage of radioactive components to the ground surface.
B. Reinforcement of a Bank Wall as a second embodiment (see FIG. 6)
After a land side of a caisson 16 installed on a riprap mound 15 is
reclaimed, a construction work is done to reinforce the ground of a reclaimed area.
- (1) A vertical reinforcement wall 17 is built on the rear surface of the caisson
The vertical reinforcement wall 17 can be built by, after a continuous
trench is excavated by the excavator in which the cutter 2 shown in FIGS. 1 and
2 is vertically mounted on the running carriage 1, pouring a solidifying solution
into the continuous trench and solidifying it therein.
- (2) Behind the vertical reinforcement wall 17, a slanting continuous trench
is excavated using the excavator of FIG. 1, and an oblique wall 18 is built by pouring
a solidifying solution into the continuous trench and solidifying it therein.
- (3) A vertical reinforcement wall 17 is built behind this oblique wall 18.
After an underground reinforcement is constructed by successively
building the vertical reinforcement walls 17 and the oblique walls 18 within a specified
area, a paved road 19 is built on the ground surface.
The oblique wall 18 may be comprised of a single wall obliquely extending
between the vertical reinforcement walls 17 or two crosswise intersecting walls.
By building the oblique walls 18 between vertical reinforcement walls
17, the strength of the underground reinforcement can be considerably enhanced and,
particularly, a highly earthquake-resistant bank wall can be built.
C. Water Cutoff during the Construction of a Common Trench as a third embodiment
(see FIG. 7).
In the case that a common trench 20 of concrete or like material for
accommodating wires and pipes such as gas pipes, electric wires, water pipes and
sewage pipes is built in the ground, since there is a likelihood of submergence
from below during the excavation of the trench in a place where free-water elevation
is high, a cutoff bottom wall needs to be built below the common trench 20.
In this case, there has been conventionally adopted a time and labor
consuming method for building vertical walls up to an impermeable bed at the opposite
sides of the common trench.
Contrary to this, if a building method according to the invention
is adopted, after vertical walls 21 are built at the opposite sides of the common
trench 20, a slanting continuous trench is so excavated as to extend over the two
vertical walls 21 and a solidifying solution is poured thereinto and solidified
therein. In this way, a slanting cutoff bottom wall 22 can be easily built at a
reduced cost and for a short time.
D. Prevention of the Liquefaction of the Ground as a fourth embodiment
The liquefaction of the ground can be prevented by preventing the
gushing of groundwater.
Accordingly, as shown in FIG. 8, slanting continuous trenches are
continuously excavated in a zigzag manner in the ground which is likely to experience
a liquefaction. A zigzag continuous cutoff wall 23 is built by pouring a solidifying
solution into the zigzag trench and solidifying it therein. A liquefaction prevention
ground which is cut off from groundwater is built over a wide range above the continuous
cutoff wall 23.
E. Conservancy of River and Sea Banks as further explanatory examples (Hereafter,
Description is Made Taking a River Bank as an Example).
E-1 Construction of a Bank Protection Wall
Conventionally, a construction work for the protection of a bank to
stop a washout (erosion of the river bank) has been generally done by a following
- (a) A poling board is placed in water near the river bank to dam up the water,
thereby performing a so-called coffering.
- (b) After the water at the land side with respect to the poling board is pumped
out, the slope of the river bank is reformed.
- (c) Concrete is deposited on the bank surface including the slanting surface
thereof to consolidate the foundation.
- (d) After the concrete surface at the slope is covered with soil or earth, the
poling board is removed.
However, according to this technique, since the natural bank slope
is worked, it cannot meet a recent demand for remaining natural views.
Further, many construction steps of this technique leads to a poor
construction efficiency and a higher cost.
Furthermore, the river is dammed up and the construction work is done
at the outside of the river bank, it is difficult to quickly evacuate at the time
of the rise of water. Thus, no construction work is normally possible during a flooding
period (June through November).
Accordingly, as shown in FIG. 9, a slanting continuous trench is excavated
in the river bank along a natural bank slope 24, and a slanting bank protection
wall 25 is built along the bank by pouring a solidifying solution into this continuous
trench and solidifying it therein.
According to this technique, since it is not necessary to work the
natural bank slope 24 and the bank protection wall 25 is concealed in the ground,
natural views can be maintained.
Further, even if the bank slope 24 is washed out to expose the bank
protection wall 25 as shown in FIG. 10, since the bank protection wall 25 is slanting,
the bank is allowed to have a bank slope which is very similar to the original bank
In addition, since the construction work can be done on the bank and
it is not necessary to dam up the river, evacuation at the time of the rise of water
can be easily made. Thus, the construction work can be made possible even during
a flooding period.
E-2 Countermeasure against the Leakage of Already Existing Embankments
In the case that an embankment itself or its foundation portion is
a permeable bed, there is a likelihood that river water permeates through this permeable
bed and leaks to the land side.
In such a case, a labor and cost consuming technique has been conventionally
adopted: a cutoff wall is built on the bank slope at the river side in the case
that the embankment itself is a permeable bed, whereas a poling board for water
cutoff purpose is placed in the case that the foundation portion is a permeable
Accordingly, as shown in FIG. 11, in the case that a foundation portion
27 of an embankment 26 (or the embankment itself) is a permeable bed, a slanting
continuous trench is excavated along a bank slope 28 on the embankment, and a slanting
cutoff wall 29 is built by pouring a solidifying solution into this trench and solidifying
it therein. Identified by 30 is an impermeable bed.
According to this technique, a construction work for preventing the
leakage from the river side to the land side can be efficiently performed with a
fewer number of construction steps and at a reduced cost.
E-3 Reinforcement of an Already Existing Embankment
As shown in FIG. 12, slip destruction occurs when the embankment 26
is weak. Further, if the embankment 26 and the foundation portion 27 are both weak,
slip destruction occurs, extending over the both as indicated by phantom line in
In order to prevent such a slip destruction, a slanting reinforcement
wall 31 is built in the embankment 26 as shown in FIG. 13, or in the foundation
portion 27 as shown in FIG. 14, or over the embankment 26 and the foundation portion
27 as shown in FIG. 15.
In such a case, as compared with the vertical reinforcement wall,
a leaning wall effect: the weight of the slanting reinforcement wall 31 acts against
the earth pressure, can be obtained, thereby enhancing a reinforcing function and
a slip destruction preventing effect.
F. Further embodiments of Vertical Water Cutoff Technique
According to the vertical water cutoff techniques shown in FIGS. 7
and 8, the slanting cutoff walls 22, 23 are linearly built. Accordingly, in the
case that an area is desired to be enclosed by cutoff walls, vertical walls need
to be built at the opposite sides with respect to the widthwise directions of the
cutoff walls 22, 23. In other words, there is a disadvantage that the cutoff walls
cannot be continuously built.
In view of the above, following techniques may be adopted.
- (I) In the case that a stockroom for compressed air or the like is constructed
in the ground, a conical continuous trench G is excavated by moving the excavator
in circle on the ground with a contact point of the cutter 2 with the ground surface
as a fixed point as shown in FIGS. 16 and 17. By pouring a solidifying solution
into this trench G and solidifying it therein, a conical cutoff roof 32 is built.
As shown in FIG. 17, a cylindrical side wall 33 according to a fifth
embodiment of the invention is built around the cutoff roof 32 up to an impermeable
bed 34. The underground stockroom is constructed by removing earth and sand between
the cutoff roof 32, the side wall 33 and the impermeable bed 34 and connecting the
cutoff roof 32 and the side wall 33.
- (II) In the case that a cutoff bottom wall is built at the time of pit excavation,
the excavator is moved in circle on the ground with an intermediate point of a portion
of the cutter placed in the ground as a fixed point, thereby excavating an inverted
conical and a conical continuous trenches G at upper and lower sides of the underground,
respectively, with their apices in contact with each other as shown in FIG. 18.
A solidifying solution is poured into these trenches G and solidified therein, thereby
building an inverted conical and a conical continuous walls 35, 36 at the upper
and lower sides, respectively, as a sixth embodiment of the invention.
After or before this operation, a cylindrical side wall 37 is built
up to an impermeable bed 38.
Thereafter, as shown in FIG. 19, pit excavation is performed for an
area enclosed by the side wall 37 with the lower side conical continuous wall 36
used as a cutoff bottom wall.
It should be noted that this technique may also be used as a technique
for constructing an underground stockroom deep in the underground by building the
side wall 37 deeper than the lower side conical wall 36 and using the conical wall
36 as a cutoff roof as indicated by phantom line in FIG. 19.
- (III) By moving the excavator in circle with the bottom end of the portion of
the cutter placed in the ground as a fixed point, an inverted conical continuous
trench G is excavated as shown in FIG. 20. A solidifying solution is poured into
this trench G and solidified therein. In this way, a cutoff bottom wall for a circular
pit excavation area or liquefaction prevention area can be efficiently continuously
built according to a further explanatory example.
In the foregoing embodiments and explanatory examples, the solidifying
solution (cement slurry) is poured into the excavated continuous trench and mixed
with the soil available in the original position to build a continuous wall of soil
cement. However, concrete may be poured into the excavated trench and solidified
therein to build a concrete continuous wall.
Alternatively, the continuous wall may be built by inserting panels
of steel or concrete into the excavated continuous trench while connecting them
in a transverse direction.
The present invention is widely applicable to a variety of purposes
other than those mentioned in the foregoing embodiments.
On the other hand, in the building apparatus (excavator), the backstay
10 is constructed by a hydraulic cylinder and the inclination is adjusted by expanding
and contracting this hydraulic cylinder in the foregoing embodiments. However, the
backstay 10 may be telescopically constructed merely by an inner tube and an outer
tube and the inclination may be adjusted with the help of a crane or like lifting
As described above, according to the present invention, the slanting
continuous trench is excavated by obliquely mounting the chain cutter provided with
excavation blades on the running carriage and moving the running carriage in the
transverse direction while rotating the cutter with the cutter obliquely placed
in the ground, and the wall material is poured into this excavated trench, thereby
building the slanting continuous wall in the ground. Accordingly, the application
of the continuous walls is the use as a cutoff wall having a water cutoff function
along vertical direction.
Furthermore, according to the invention the continuous wall is built
as the repair roof of the underground construction such as a stockroom for radioactive
According to the invention defined in claim 2, the roof and the floor
for preventing the entry of water into the underground stockroom can be efficiently
built with a fewer number of construction steps.
In this case, according to the invention defined in claim 3, the inverted
conical and conical continuous walls are built at the upper and lower side with
the apices thereof in contact with each other, and the lower continuous wall can
be used as a cutoff bottom wall for pit excavation or an underground roof for an
Further, according to the invention defined in claim 4, the continuous
wall can be built as a water cutoff bottom wall for preventing the entry of groundwater
into a trench excavated, e.g. to build a common trench in the ground where free-water
elevation is high.