BACKGROUND OF THE INVENTION
Field of the Invention:
The present invention relates to a technique of
constructing a shaft in the ground for constructing sewerage,
laying electric wires, constructing a manhole or the like.
Description of the Prior Arts:
In sewerage or manhole construction, a shaft is excavated
by using an excavating apparatus such as a grab bucket or an
earth auger, and excavation for constructing a sewer is
performed from a starting pit entrance of the shaft by a shield
machine. In shaft excavating work, before excavating, a
cylindrical casing is clamped by a pressing and driving
apparatus provided on the excavating apparatus, and is pressed
into the ground with an oscillating rotational motion around
the axis of the casing or a rotational motion to one direction
around the axis of the casing. Then, the earth within the
casing is excavated and discharged by the grab bucket onto the
ground, and additional casings are successively joined and
pressed until the intended depth of the shaft is reached.
Accordingly, the cylindrical casing is used as an excavating
means when excavating a shaft in the ground, and also serves
as a retaining wall to be left in the ground after construction.
As mentioned above, after the cylindrical casing has been
driven in, followed by removal of earth from the casing, a
concrete bottom plate is cast on the bottom, and any remaining
water within the shaft is pumped out. Thus, a shaft enclosed
with a casing is constructed.
In the conventional construction method, the casing must
act as a retaining wall, and also be strong enough to withstand
the thrust of pressing-driving and torque and impact of the
edge of the excavating blade during excavation. Accordingly,
in order to improve the rigidity, casings of 10 to 25 mm in
thickness or double-structured casings having a total
thickness of about 45 mm have been employed.
However, in the above case, the total weight of the casing
is increased, and production costs also significantly increase
with the increased thickness.
Additionally, in the conventional construction method,
since the thicker casing is left in the ground after the shaft
has been constructed, a large amount of structural steel is
wasted. In this case, the increased structural steel which
remains in the ground would eventually cause environmental
problems due to corrosion, which is not something that can be
disregarded. Further, when a new underground structure is
built after the former structure is removed, it is necessary
to pull out the entire casing or to remove it by cutting and
scrapping. Casings of the conventional construction method
are difficult to cut and scrap due to their thick walls.
SUMMARY OF THE INVENTION
Accordingly, an object of the present invention is to
provide a shaft excavating technique which can reduce wasteful
consumption of casing material and which can result in a high
strength shaft.
In order to solve the problems mentioned above, in
accordance with the present invention, there is provided a
method of constructing a shaft comprising a step of inserting
a cylindrical earth-retaining casing into a shaft excavated
in the ground, and a step of corrugating said earth-retaining
casing to form the circumferential wall thereof into a
wave-like longitudinal cross section. By the above steps, the
corrugated earth-retaining casing is installed inside the
excavated shaft. The waveform corrugation provides increased
rigidity so that the earth-retaining casing will not be
deformed by the pressure of the earth even when the thickness
thereof is less than that of the casing in accordance with the
conventional construction method. Accordingly, a shaft of
high strength can be constructed, and wasteful consumption of
the casing material can be reduced.
Further, in accordance with the present invention, there
is provided a method of constructing a shaft comprising a step
of pressing and driving a cylindrical excavation casing in the
ground, a step of discharging earth from the excavation casing
after it has been driven into the ground, a step of inserting
a cylindrical earth-retaining casing into the excavation
casing, and a step of removing the excavation casing from the
ground while corrugating the earth-retaining casing to form
a wave-like pattern on the circumferential wall thereof. By
the above steps, the corrugated earth-retaining casing is
installed in the ground. The waveform corrugation provides
increased rigidity so that the earth-retaining casing will not
be deformed by the pressure of the earth even after the
excavation casing is removed from the ground, and the
constructed shaft has high strength. Further, since the
strength of the earth-retaining casing is improved by waveform
corrugation, an earth-retaining casing with less thickness
than that of the excavation casing can be used, and material
waste can be reduced.
Still further, in accordance with the present invention,
there is provided a method of constructing a shaft comprising
a step of pressing and driving a cylindrical excavation casing
into the ground, a step of discharging earth from the driven
excavation casing, a step of inserting a cylindrical
earth-retaining casing into the excavation casing, a step of
pouring a hardening agent into the space between the excavation
casing and the earth-retaining casing, and a step of removing
the excavation casing from the ground concurrently or
subsequently to the pouring of the hardening agent. By the
above steps, the earth-retaining casing and the hardening
agent layer formed on the outer surface of the casing are
installed in the ground. Since the integration of the
earth-retaining casing and the hardening agent layer increases
the rigidity, the earth-retaining casing will not be deformed
by the pressure of the surrounding earth even after the
excavation casing is removed from the ground. Thus, a shaft
having high strength can be constructed. Further, since the
strength is improved by integrating the earth-retaining casing
with the hardening agent layer, an earth-retaining casing with
a thinner wall than that of the excavation casing can be
employed. Accordingly, over-consumption of casing material
can be reduced.
In this case, when a earth-retaining casing
prefabricated a corrugation is used, the thickness can be
reduced while the rigidity is secured so that the consumption
of the casing material can be even further reduced.
Further, a shaft construction method provided in the
present invention includes a step of connecting earth-retaining
casings by inserting a non-corrugated earth-retaining
casing into a corrugated earth-retaining casing, to
a depth where they overlap each other at the adjacent ends,
and by corrugating the overlapping portions of said two
earth-retaining casings together.
Thus, since it is possible to construct a shaft by
successively joining earth-retaining casings, this method is
readily applicable to the construction of deep shafts.
Further, since the end portions of the earth-retaining casings
overlap and are corrugated, a secure connection with high
strength and excellent watertightness can be obtained. When
the waveform on the corrugated earth-retaining casing has been
given by using an apparatus for constructing a shaft to be
mentioned below, said earth-retaining casing has been wholly
expanded in diameter thereof, so that it is possible to insert
the end portion of the earth-retaining casing which has not
yet been corrugated into the end portion of the earth-retaining
casing which has been, and the two ends easily overlap.
Further, in a shaft construction method in accordance
with the present invention, the use of an earth-retaining
casing having a bottom plate which includes a water inlet and
a grout inlet with a check valve for each of said inlets
increases the strength of the earth-retaining casing. Thus
increased strength can prevent the deformation of the
earth-retaining casing while it is being inserted into a shaft
or into an excavation casing in the ground. Still further,
a concreting and curing process for the bottom of the shaft
is saved, while the watertightness of the shaft after
construction can be improved.
Here, if there is water remaining within the shaft or
the excavation casing when inserting the earth-retaining
casing having the bottom plate, subsidence of the earth-retaining
casing will be prevented due to the buoyancy of the
water. However, leading the water into the earth-retaining
casing through the water inlet with the check valve can promote
the subsidence of the earth-retaining casing. In this case,
it is necessary to keep the water inlet open while the
earth-retaining casing settles, and it is necessary to close
it afterwards. When a spring which works in the inlet closing
direction is provided for the check valve and a water soluble
solid is held between the check valve and a valve seat before
inserting the earth-retaining casing into the shaft or the
excavation casing, the check valve is kept open during the
subsidence of the earth-retaining casing. After the
subsidence, the water soluble solid dissolves and disappears
so that the check valve automatically closes.
Further, the grout inlet with the check valve provided
in the bottom plate of the earth-retaining casing can be used
for a mortar filling operation from above-ground to under the
bottom plate, and the deposited mortar will never flow backward
through the grout inlet before being cured.
In this case, if a tubular guide column is set up on the
bottom plate or on the grout inlet in a way to communicate with
it, said column can be used as a supporting member for guiding
and holding a shaft constructing apparatus, to be mentioned
below, in a corrugating operation for the earth-retaining
casing. Thus the stability of operation is improved. Further,
the mortar filling operation from above-ground to under the
bottom plate can be performed through the hollow inside of the
tubular guide column.
In accordance with the present invention, there is
further provided an apparatus for constructing a shaft
comprising an expanding means structured in such a manner as
to be installable inside a cylindrical earth-retaining casing
in the ground and to be capable of expanding and contracting
in the radial direction of the earth-retaining casing, and a
moving means for moving the expanding means in the axial
direction of the cylindrical casing. As being structured in
the above manner, the apparatus can apply corrugation
treatment on the cylindrical earth-retaining casing, without
using any other moving apparatus, by alternately repeating an
operation of expanding diameter of the earth-retaining casing
by means of the expanding means and an operation of moving the
expanding means in the axial direction by means of the moving
means. Since the waveform corrugation of the earth-retaining
casing greatly enhances rigidity in comparison with a simple
cylindrical body, a high-strength shaft which will not be
deformed by the pressure of the earth can be constructed.
Further, the thickness of the earth-retaining casing can be
reduced so that wasteful consumption of the casing material
can be restricted.
Further, in accordance with the present invention, there
is provided an apparatus for constructing a shaft, wherein the
expanding means comprises an upper expanding mechanism and a
lower expanding mechanism having press molds which are
disposed in a substantially circular manner along the inner
periphery of the earth-retaining casing and can expand and
contract in the radial direction of the earth-retaining casing,
and the moving means comprises a length-extending mechanism
capable of extending and shortening the distance between the
upper and lower expanding mechanisms. As having the above
structure, the shaft constructing apparatus can form a
corrugated waveform on the earth-retaining casing by
alternately repeating an operation of expanding and
contracting the press molds in the upper expanding mechanism
and the lower expanding mechanism and an operation of extending
and shortening the distance between the upper and lower
expanding mechanisms by means of the length-extending
mechanism. In this case, since the shaft constructing
apparatus can conduct a corrugating operation while ascending
within the earth-retaining casing in a looping movement, it
is not necessary to independently provide an apparatus to raise
the shaft constructing apparatus, thus simplifying
construction and making operation easy.
Still further, in a shaft constructing apparatus in
accordance with the present invention, the expanding means is
provided with a support column set up in the axial direction
of the earth-retaining casing and a support bar mounted in a
substantially horizontal manner on the support column. Thus,
the shaft constructing apparatus can be securely held during
a corrugating operation inside the earth-retaining casing. In
this case, when the support column body is formed to be tubular
or hollow, the mortar filling operation to under the bottom
plate of the earth-retaining casing can be performed through
the hollow inside of the support column.
BRIEF DESCRIPTION OF THE DRAWINGS
Fig. 1 is a cross-sectional view which shows a step of
pressing and driving an excavation casing into the ground in
accordance with the first embodiment;
Fig. 2 is a cross-sectional view which shows a step of
inserting an earth-retaining casing into the excavation casing
in accordance with the first embodiment;
Fig. 3 is a cross-sectional view which shows a step of
casting a concrete bottom plate in the earth-retaining casing
in accordance with the first embodiment;
Fig. 4 is a cross-sectional view which shows a step of
pouring a hardening agent in the space between the excavation
casing and the earth-retaining casing while removing the
excavation casing in accordance with the first embodiment;
Fig. 5 is a cross-sectional view which shows a shaft
constructed in accordance with the first embodiment;
Fig. 6A is a front elevational view which shows a
corrugated segment applicable to the earth-retaining casing,
Fig. 6B is a plan view of the same, Fig. 6C is a side elevational
view of the same and Fig. 6D is a schematic view showing a state
in which the corrugated segments are assembled;
Fig. 7A is a front elevational view which shows a liner
plate segment applicable to the earth-retaining casing, Fig.
7B is a plan view of the same and Fig. 7C is a vertical
cross-sectional view of the same;
Fig. 8A is a perspective view which shows a reinforcing
ring for reinforcing the earth-retaining casing to be attached
to press against the inner peripheral surface of the
earth-retaining casing and Fig. 8B is a plan view of the same
with portions broken away for clarity;
Fig. 9 is a cross-sectional view showing an example in
which a manhole is constructed within a shaft;
Fig. 10 is a cross-sectional view showing an example in
which an underground tank is constructed within a shaft;
Fig. 11 is a cross-sectional view which shows a step of
inserting an earth-retaining casing into an excavation casing
in accordance with the second embodiment;
Fig. 12 is a cross-sectional view which shows a step of
expanding diameter in accordance with the second embodiment;
Fig. 13 is a cross-sectional view which shows a step of
expanding diameter in accordance with the second embodiment;
Fig. 14 is a horizontal cross-sectional view taken along
the line X-X in Fig. 12;
Fig. 15 is a horizontal cross-sectional view taken along
the line Y-Y in Fig. 12;
Fig. 16A, 16B and 16C are schematic views showing the
steps of the second embodiment;
Fig. 17 is a cross-sectional view which shows a shaft
constructed in accordance with the second embodiment;
Fig. 18 is a cross-sectional view which shows the third
embodiment;
Fig. 19 is a cross-sectional view which shows the fourth
embodiment; and
Figs. 20A and Fig. 20B are schematic views showing the
procedure of connecting earth-retaining casings.
DESCRIPTION OF THE PREFERRED EMBODIMENT
Four embodiments in accordance with the invention will
be described below with respect to the attached drawings.
Figs. 1 to 4 are schematic views which show steps of the
first embodiment in accordance with the present invention.
First, as shown in Fig. 1, an excavation casing 1 is pressed
and driven into the ground and earth within the excavation
casing 1 is excavated and discharged by using a shaft excavating
apparatus 50 disposed on the ground. The shaft excavating
apparatus 50 is provided with a swingable pressing apparatus
52 and a boom 53 on a moving vehicle 51 and has a grab bucket
54 at the front of the boom 53. The swingable pressing
apparatus 52 has a function of holding the excavation casing
1 by means of a clamp 52a and of driving the excavation casing
1 into the ground by pressing and oscillating the same, and
can excavate and discharge the earth within the driven
excavation casing 1 onto the ground by means of the grab bucket
54.
The excavation casing 1 is a hollow cylindrical body made
of a steel plate having a thickness of 10 to 25 mm, and after
the earth within the excavation casing 1 driven first in the
ground is excavated and discharged by the grab bucket 54,
another excavation casing 1 is driven on top of the first. In
this case, the joint portions between the excavation casings
1 which are vertically disposed, are joined by a dedicated joint
or integrally connected by welding. In this embodiment, two
excavation casings are driven in, and the second casing is
mounted on top of the first.
After the earth within the excavation casing 1 is
discharged, as shown in Fig. 2, an earth-retaining casing 2
is inserted into the excavation casing 1. In this case,
instead of the grab bucket 54, a hook 55 is mounted on the boom
53, to which a wire (not shown) is hooked, thereby hanging the
earth-retaining casing 2 during insertion.
After the earth-retaining casing 2 is immersed in the
water W remaining within the excavation casing 1, as shown in
Fig. 3, a tremie 56 is inserted into the earth-retaining casing
2, and a ready mixed concrete 6 is filled in a bottom portion
of the earth-retaining casing 2 from above-ground through the
tremie 56. Thus, a concrete bottom plate 7 is cast in such
a manner that the entire bottom of the earth-retaining casing
2 is covered. It is necessary to cure the concrete bottom plate
7 until it is completely hardened so that the earth-retaining
casing 2 will not come off with the excavation casing 1 when
it is pulled out from the ground.
When the concrete bottom plate 7 is hardened, as shown
in Fig. 4, a hardening agent 8 is filled in the space between
the excavation casing 1 and the earth-retaining casing 2 while,
at the same time, the excavation casing 1 is pulled out while
being oscillated by the swingable pressing apparatus 52.
During this operation, since the concrete bottom plate 7 has
already been cast in the earth-retaining casing 2, the
hardening agent 8 does not flow into the earth-retaining casing
2. Thus, by pulling out the excavation casing 1 while pouring
the hardening agent 8, the hardening agent 8 backfills the
earth-retaining casing 2 throughout its outer periphery from
the periphery of the concrete bottom plate 7 to the ground
surface.
In this embodiment, as shown in Fig. 4, the hardening
agent 8 consisting of a material of cement, inorganic salt,
sodium silicate or the like is mixed by a hardening agent mixer
57 on the ground, and is cast into the space between the
excavation casing 1 and the earth-retaining casing 2 through
a filling hose 59 by a hardening agent filling pump 58. Instead
of the above filling method, a nozzle for injecting the
hardening agent 8 may be used, or the hardening agent 8 may
be supplied through a hose connecting the hardening agent
filling pump 58 to a hole which is opened near the lower end
of the earth-retaining casing 2.
There is a gap between the excavation casing 1 and the
earth-retaining casing 2. When the excavation casing 1 is
pulled out as the hardening agent 8 is being cast, the hardening
agent 8 forms its layer in this gap. Therefore, the excavation
casing 1 can be pulled out without interfering with the outer
surface of the earth-retaining casing 2. Furthermore, the
excavation casing 1 does not sustain damage even if the wall
of the earth-retaining casing 2 is relatively thin. Since the
hardening agent 8 is in a near-liquid phase, the friction
coefficient between the excavation casing 1 and the earth-retaining
casing 2 can be kept low. Thus, the excavation
casing 1 can be pulled out smoothly and quickly.
The removal of the upper and the lower excavating casings
1 may be conducted as a continuous operation. However, the
removing and transporting operation on the ground can be
carried out more efficiently by disconnecting the upper
excavating casing 1 from the lower excavating casing 1, being
still in the ground, by means of removing the joint 1a upon
its appearance above the ground during the pulling-out process
of the excavating casing 1, or melting and removing the weld
bead if connected by welding. If a reinforcing ring 5 (refer
to Fig. 8) mentioned below is used for the earth-retaining
casing 2, it should be kept in the reinforcing state.
After the above steps, all pieces of equipment including
the shaft excavating apparatus 50 are removed. In half a day
or one day, after the concrete bottom plate 7 and the hardening
agent 8 have completely hardened and cured, the remaining water
W within the earth-retaining casing 2 is pumped out, and
thereafter the reinforcing ring 5 is removed. Thus, the shaft
as shown in Fig. 5 is constructed.
The shaft mentioned above is provided with a strong
cylindrical construction because the earth-retaining casing
2 is integrally covered with the hardening agent 8 around its
outer periphery. Accordingly, the shaft is strong enough to
withstand an external load due to the pressure of the earth,
buoyancy due to underground water and a bending load due to
shifting earth, thereby preventing collapse and deformation
of the earth-retaining casing. In this embodiment, the
earth-retaining casing 2, being formed in a corrugated shape,
has sufficient strength against compressing forces in axial
and radial directions even if the wall is relatively thin, which
leads to more effective maintenance of the shaft. Further,
since the earth-retaining casing 2 which is left in the ground
is relatively thin, less steel is needed in comparison with
the conventional method in which the excavation casing 1 is
left in the ground, and thus economy is improved.
In this embodiment, as the earth-retaining casing 2, a
corrugated pipe having a cross section of a uniformly
continuous waveform may be employed. In addition, a liner
plate or a segment type may also be used.
Referring to Fig. 6, a corrugated segment which is
applicable as a member of the earth-retaining casing 2 as well
as a method of assembling the same will be described below.
A corrugated segment 3 comprises a rectangular steel plate 3a
having a thickness of about 1.6 to 4 mm which is bent to make
an arc as shown in Fig. 6B, of which the cross section is a
waveform as shown in Fig. 6C. The steel plate 3a has connection
holes 3b in the peripheral portion thereof, and can be disposed
overlapping other steel plates 3a at the side end portions as
shown in Fig. 6D with rivets or bolts passing through the
connection holes 3b, thereby forming a hollow cylindrical body
to make the earth-retaining casing 2. Further, a plurality
of hollow cylindrical bodies can be connected in a vertical
direction with rivets or bolts passing through the connection
holes 3b in the axial ends which overlap in order to make the
earth-retaining casing 2 longer.
The above-described corrugated segments 3 can be
prefabricated, and assembled into the earth-retaining casing
2 at the construction site. Therefore, an earth-retaining
casing with a larger diameter can be easily transported by truck.
Of course, it is also possible that the corrugated segments
3 be assembled into the earth-retaining casing 2 in a shop,
and then the thus assembled earth-retaining casing 2 is
transported to the construction site and installed.
Next, referring to Fig. 7, a liner plate segment which
is applicable to the earth-retaining casing 2 and a method of
assembling the same will be described below. A liner plate
segment 4 is arc-shaped as shown in Fig. 7B, and has connection
flanges 4a and 4b projecting toward the inside of the shaft
and extending throughout the length of the periphery thereof.
Its wall 4c is corrugated for improved strength as shown in
Fig. 7C. A hollow cylindrical body can be formed by matching
and fixing the two side connection flanges 4a by means of bolts
or the like passing through connection holes 4a-1. Further,
the long body needed for the earth-retaining casing 2 can be
formed by vertically piling up the hollow cylindrical bodies
to match the flanges 4b and fix them with bolts passing through
connection holes 4b-1.
As mentioned above, along with the corrugated segment
3, the liner plate segment 4 is also corrugated. Thus, they
maintain high compression strength in both axial and radial
directions even if the material is relatively thin, which
enhances the strength of the earth-retaining casings. If, to
reduce costs, a hollow cylindrical body made of a thin, plane
plate is used as the earth-retaining casing, a reinforcing ring
as shown in Fig. 8 should be employed for safety.
Fig. 9 is a cross sectional view showing a manhole
constructed within the shaft as an underground structure. In
this example, a plurality of frames 61 are vertically stacked
within the earth-retaining casing 2 to constitute a manhole.
The lowest frame 61 is held by mortar 63 which is cast to fill
the gaps above the concrete bottom plate 7. After a manhole
cover 62 is mounted on top of the frame 61, the gaps around
the outer periphery of the manhole are filled with backfill
soil 64.
Fig. 10 is a cross sectional view showing an underground
tank constructed within the shaft. In this example, a tank body
31 is inserted into the earth-retaining casing 2 so as to be
mounted on the concrete bottom plate 7, and the gaps between
the earth-retaining casing 2 and the tank body 31 are filled
with backfill soil 32. Further, mortar 33 is cast on the ground
surface.
In the above examples, the pre-constructed shaft has high
strength due to the earth-retaining casing 2 being integrated
with the hardening agent 8. An underground structure such as
a manhole or an underground tank constructed in this way remains
in good condition, without sustaining damage or breakage.
Further, in either of the above constructions, the
excavation casing 1 is recovered from the ground when pouring
the hardening agent 8 after excavation and discharge of the
earth from the excavation casing 1 is completed. Thus, the
excavation casing 1 can be reused many times. Since the
excavation casing 1 will not be wasted, it may be made of a
more expensive construction: for example, the excavation
casing 1 may have a specially designed blade tip made of a
special alloy to improve the excavation efficiency, or may be
made of a special steel for further enhanced durability.
Further, it is possible to make the excavation casing 1 a
lightweight double structure with high strength. Further, a
large-sized excavation casing which exceeds the width limit
of vehicle transportation may have a vertically dividable type
structure.
Next, the second embodiment of the present invention will
be described below with reference to Figs. 11 to 15. Fig. 11
is a vertical cross-sectional view wherein an earth-retaining
casing is inserted into an excavation casing; Fig. 12 is a
vertical cross-sectional view which shows a mechanism for
increasing diameter; Fig. 13 is a vertical cross-sectional
view which illustrates an extending operation with a
length-extending mechanism; and Figs. 14 and 15 are transverse
sectional views taken along the line X-X and Y-Y in Fig. 12,
respectively.
In this embodiment, in the same manner as the steps shown
in Fig. 1 in accordance with the first embodiment, an excavation
casing 12 is driven into the ground, and the earth within the
pressed excavation casing 12 is excavated and discharged using
a shaft excavating apparatus 50 disposed on the ground. After
the above operation is completed, as shown in Fig. 11, an
earth-retaining casing 13 to which a bottom plate 15 with a
tubular guide column 14 is mounted is inserted into the
excavation casing 12. During this operation, the remaining
water 18, if present within the excavation casing 12, can be
introduced into the earth-retaining casing 13 through a water
inlet 16 in the bottom plate 15 by setting a check valve 16v
thereof, also provided in the bottom plate 15, to the open
position beforehand. Thus, the earth-retaining casing 13 can
easily subside.
It is necessary to keep the check valve 16v of the water
inlet 16 open while the earth-retaining casing 13 subsides,
and it is necessary to eventually close it when pumping out
the water 18 remaining within the earth-retaining casing 13.
Therefore, a material which has a predetermined hardness in
open air and dissolves in water over a predetermined length
of time, such as a sugar material, is placed between the check
valve 16v and the valve seat.
When the earth-retaining casing 13 is completely
inserted into the excavation casing 12, a corrugating
13 starts.
The structure of the corrugating apparatus 20 which is
a part of the shaft constructing apparatus will be described
below. The corrugating apparatus 20 consists of an upper
expanding mechanism A and a lower expanding mechanism B which
are vertically disposed. Fig. 14 shows the upper expanding
mechanism A, and Fig. 15 shows the lower expanding mechanism
B. Eight hydraulic actuators 21 and 23 which are extendable
and contractible are radially disposed in the expanding
mechanisms A and B, respectively, and arc-shaped press molds
22 and 24 are mounted at the ends of the hydraulic actuators
21 and 23, respectively, so as to form a substantially circular
shape along the inner periphery of the earth-retaining casing
13. Further, as shown in Figs. 12 and 13, an extendable
hydraulic actuator 25 for changing the distance between the
expanding mechanisms A and B is provided.
An anti-rotation member S is also provided for each of
the hydraulic actuators 21, 23 so that the press molds 22 and
24 will not slip out of place with the rotation of rods R of
the hydraulic actuators 21 and 23. The hydraulic actuators
21, 23 and 25 are operated by hydraulic pressure supplied
through a hydraulic hose from a hydraulic pump controlled by
a control panel located on the ground, which is not shown in
the drawings.
Next, described below is a corrugating operation for the
earth-retaining casing 13 by use of the corrugating apparatus
20. After the corrugating apparatus 20 is completely inserted
into the earth-retaining casing 13, as shown in Fig. 12, the
excavation casing 12 is lifted up to a depth not interfering
with the diameter-expanding operation, and the hydraulic
actuators 23 of the lower expanding mechanism B are extended
so that the earth-retaining casing 13 is given a waveform crest
by the press molds 24. Then, the hydraulic actuators 21 of
the upper expanding mechanism A is extended so that the
earth-retaining casing 13 is given another waveform crest by
the press molds 22. The distance between the upper expanding
mechanism A and the lower expanding mechanism B at this stage
determines the interval between waveform crests.
Next, the press molds 22 are removed from the second
waveform crest on the earth-retaining casing 13 by contracting
the hydraulic actuators 21 of the upper expanding mechanism
A. Then, the hydraulic actuator 25 is extended so that the
upper expanding mechanism A is lifted up a step as shown in
Fig. 13, and the hydraulic actuators 21 are again extended so
that the earth-retaining casing 13 is given the next crest by
the press molds 22. During this operation, the lower expanding
mechanism B keeps the press molds 24 pressed against the first
waveform crest of the earth-retaining casing 13. Thus, the
corrugating apparatus 20 does not fall or slip. The excavation
casing 12 is gradually pulled up in accordance with the progress
of the operation so as not to disturb the corrugating operation.
Then, the press molds 24 are removed from the first
waveform crest of the earth-retaining casing 13 by contracting
the hydraulic actuators 23 of the lower expanding mechanism
B, and the hydraulic actuator 25 is contracted to raise the
lower expanding mechanism B a step. The hydraulic actuators
23 are again extended so that the press molds 24 are pressed
against the second waveform crest previously formed by the
press molds 22 of the upper expanding mechanism A, thereby
adjusting the waveform into a proper shape. While the lower
expanding mechanism B is in motion, the upper expanding
mechanism A keeps the press molds 22 pressed against the newest
waveform crest on the earth-retaining casing 13. Thus, the
corrugating apparatus 20 does not fall or slip.
As shown in Figs. 14 and 15, the press molds 22 and 24
in the upper expanding mechanism A and the lower expanding
mechanism B are disposed to project evenly around the tubular
guide column 14 covering alternating areas. Thus, the concave
portions 13r, which have not been properly pushed out due to
their positions corresponding to gaps between the press molds
22 in the upper expanding mechanism A, can be shaped properly
by the press molds 24 of the lower expanding mechanism B.
Accordingly, irregularity in the waveform is eliminated so that
the strength, particularly resistance to pressure, is greatly
improved. Further, since the press molds 22 and 24 have an
arc shape and are disposed in a substantially circular manner
along the inner periphery of the earth-retaining casing 13,
the waveform created in the earth-retaining casing 13 is a
series of substantially concentric circles.
Thereafter, the hydraulic actuators 21 in the upper
expanding mechanism A are contracted again to detach the press
molds 22 from the current waveform crest positions, and the
hydraulic actuator 25 is extended so that the upper expanding
mechanism A is further raised a step. The hydraulic actuators
21 are again extended so that the earth-retaining casing 13
is given another waveform crest by the press molds 22. By
repeating the above operation further while the excavation
casing 12 is gradually raised, the corrugating apparatus 20
forms the waveform on the earth-retaining casing.
In other words, the corrugating apparatus 20 ascends in
a looping movement by alternately repeating the operation of
expanding diameter of the earth-retaining casing 13 by means
of the upper expanding mechanism A and the lower expanding
mechanism B and the operation of extending and shortening the
distance between the upper expanding mechanism A and the lower
expanding mechanism B by means of the hydraulic actuator 25,
as shown in Figs. 16A to 16C, to form a continuous, uniform
waveform on the earth-retaining casing 13.
If the ground in the outer periphery of the earth-retaining
casing 13 to be corrugated by the upper expanding
mechanism A is not homogeneous, the pressing force applied by
the press molds 22 may not be uniform. However, since the press
molds 22 are held by both the lower expanding mechanism B and
the tubular guide column 14, the operation of molds 22 will
not be affected by differences in reaction force, and the
corrugating operation will progress evenly. In this case, the
tubular guide column 14 also serves as a guide for the vertical
motion of the hydraulic actuator 25, which changes the distance
between the upper expanding mechanism A and the lower expanding
mechanism B.
After the waveform is formed up to a predetermined
position of the earth-retaining casing 13, mortar M is grouted
under the bottom plate 15 through a grout hole 17 (see Fig.
11) provided on the tubular guide column 14. The mortar M does
not flow backward because a check valve 19v is provided in a
grout inlet 19 of the bottom plate 15. Thus, after the grouting
of the mortar is finished, the tubular guide column 14 can be
removed regardless of the hardness of the mortar M. Thereafter,
the water inside the earth-retaining casing 13 is pumped out,
and the shaft will be in a state as shown in Fig. 17. Thus,
the shaft construction is completed. In the example described
above, the corrugating apparatus 20 has two diameter-expanding
mechanisms; also, the earth-retaining casing 13 can be
corrugated with a corrugating apparatus having three or more
diameter-expanding mechanisms by following the procedure as
described above.
Next, a third embodiment of the invention will be
described below with reference to Fig. 18. In this embodiment,
a corrugating apparatus 40 consists of an upper expanding
mechanism A and a lower expanding mechanism B which are
vertically disposed. A tubular guide column 42 having a
longitudinal through hole 41 guides the movement of the
corrugating apparatus 40. The tubular guide column 42 is fixed
to a fixing metal fitting 45 provided in a bottom plate
reinforcing bar 44 which is fixed to the bottom portion of an
earth-retaining casing 13 while the corrugating apparatus 40
is applying corrugation treatment. After the corrugating
operation is completed, the tubular guide column 42 is removed
from the fixing metal fitting 45, and a concrete bottom plate
is cast. The bottom plate reinforcing bar 44 also serves as
a reinforcing bar for the concrete bottom plate.
The corrugating apparatus 40, like the corrugating
apparatus 20 mentioned above, applies corrugation treatment
to the earth-retaining casing 13 inserted inside the excavation
casing 12 while raising the upper expanding mechanism A and
the lower expanding mechanism B by using the tubular guide
column body 42 as a guide. In the case of supporting the tubular
guide column 42 by the bottom plate reinforcing bar 44,
deviation of the upper portion of the tubular guide column 42
due to the softness of the fixing metal fitting 45 is prevented
by a substantially horizontal support bar member 43 which
supports the upper portion of the tubular guide column 42 so
that the center of the waveform formed on the earth-retaining
casing 13 does not shift. In this case, the earth-retaining
casing 13 descends in relation to the position of support bar
member 43 as the corrugating progresses, and therefore a slight
clearance is provided between an end 43a of the support bar
member 43 and the inner surface of the earth-retaining casing
13.
Next, a fourth embodiment of the invention will be
described below with reference to Fig. 19. In this embodiment,
a corrugating apparatus 60 consists of an upper expanding
mechanism A and a lower expanding mechanism B which are
vertically disposed. Eight hydraulic actuators 21 and 23
which are extendable and contractible are radially disposed
in each of the expanding mechanisms A and B, and arc-shaped
press molds 22 and 24 are mounted at the ends of the hydraulic
actuators 21 and 23, respectively, so as to form a substantially
circular shape along the inner periphery of the earth-retaining
casing 13. Further, an extendable and contractible hydraulic
actuator 25 for changing the distance between the expanding
mechanisms A and B is provided. Since the corrugating
apparatus 60 ascends in a looping movement while supporting
the apparatus itself by pushing the press molds 22 and 24
against the earth-retaining casing 13, it can carry out a
corrugating operation for the earth-retaining casing 13
without having a tubular guide column set up on the bottom
plate.
However, without the tubular guide column, the
corrugating apparatus 60 is likely to move upward in a zigzag
manner. This can be prevented by controlling the corrugating
apparatus 60 to vertically climb within the earth-retaining
casing 13 by means of a hollow support column 26 set up on the
lower expanding mechanism B and a substantially horizontal
support bar 27 provided at an upper position of the hollow
support column 26. Further, a slight clearance provided
between a pad 27a mounted at the end of the support bar 27 and
the earth-retaining casing 13 enables the corrugating
apparatus 60 to smoothly ascend.
With reference to Fig. 20, a method of connecting the
earth-retaining casing 13 will be described below. Fig. 20
is a schematic view which illustrates the procedure of
connecting two earth-retaining casings 13. In the method of
constructing a shaft in accordance with this embodiment, the
excavation casing 12 is extended by connecting the members by
use of bolts or by welding. The earth-retaining casings 13
are assembled by putting an end portion of an earth-retaining
casing 13a on an end portion of another earth-retaining casing
13b, which are disposed in a vertically adjacent manner as shown
in Fig. 20, and corrugating the overlapping ends together.
Specifically, as shown in Fig. 20A, the lower end of the
earth-retaining casing 13b which has not yet been corrugated
is inserted inside the upper end of the corrugated earth-retaining
casing 13a to the extent that the lower end of the
non-corrugated casing 13b covers one or two wave crests on the
upper end of the corrugated casing 13a, and the lower end of
the non-corrugated casing 13b is corrugated as it overlaps with
the end of the corrugated earth-retaining casing 13a. The
corrugation firmly connects the earth-retaining casings 13a
and 13b as shown in Fig. 20B. In this case, the diameter of
the earth-retaining casing 13a has been enlarged even at the
troughs 13v in the waveform along with the diameter expansion
at the crests 13m by the original corrugation. This makes it
easy to insert the non-corrugated earth-retaining casing 13b
therein.
Further, a paste or the like may be applied to the joining
faces between the earth-retaining casings 13a and 13b to gain
complete watertightness. As mentioned above, in the method
of constructing the shaft according to this embodiment,
relatively thin earth-retaining casings 13a and 13b can be used,
and the casings can be easily and securely joined without using
bolting or other troublesome means.
The present invention has advantages as follows:
(1) The method of constructing a shaft includes a step
of inserting a cylindrical earth-retaining casing into a shaft
excavated in the ground, and a step of applying corrugation
to the earth-retaining casing inserted into the shaft.
Therefore, a shaft constructed by this method has high strength,
being protected by an earth-retaining casing which has gained
increased rigidity by being corrugated. This method also
realizes lessened wasteful consumption of casing material
because casings can secure sufficient strength with walls
thinner than those used in the conventional method. Further,
as corrugation treatment is applied within the shaft, the
earth-retaining casing and the ground around the casing are
firmly pressed against each other to generate strong friction,
thereby preventing the earth-retaining casing from floating
due to the pressure of the underground water. (2) The shaft constructing method involves a step of
pressing and driving a cylindrical excavation casing into the
ground, a step of discharging earth from the excavation casing
inserted in the ground, a step of inserting a cylindrical
earth-retaining casing inside the excavation casing, and a step
of removing the excavation casing from the ground while
applying corrugation treatment to the earth-retaining casing.
Thus, this method can construct a highly strong shaft because
the earth-retaining casing installed inside the shaft in the
ground has increased rigidity gained by corrugation, and can
withstand the pressure of the earth and other forces without
sustaining deformation even after the excavation casing is
removed from the ground. Further, since sufficient strength
can be secured by an earth-retaining casing thinner than the
excavating casing, wasteful consumption of casing material can
be reduced. (3) The shaft constructing method involves a step of
pressing and driving a cylindrical excavation casing into the
ground, a step of discharging earth from the excavation casing
inserted in the ground, a step of inserting a cylindrical
earth-retaining casing into the excavation casing, a step of
pouring a hardening agent into the space between the excavation
casing and the earth-retaining casing, and a step of removing
the excavation casing from the ground concurrently or
subsequently to the pouring of the hardening agent. Thus, this
method can construct a highly strong shaft because the
earth-retaining casing installed inside has increased
rigidity by being integrated with the hardening agent layer
and withstands the pressure of the surrounding earth or other
forces without sustaining deformation even after the
excavation casing is removed. Further, since sufficient
strength can be secured by an earth-retaining casing thinner
than the excavating casing, wasteful consumption of casing
material can be reduced. (4) In the case (3) mentioned above, when an earth-retaining
casing which has been corrugated before insertion
underground is used, the thickness can be reduced while
maintaining high rigidity so that consumption of casing
material can be further reduced. (5) The shaft construction method further includes a step
of connecting the corrugated earth-retaining casing with
another earth-retaining casing which has not yet been
corrugated by inserting the non-corrugated casing into the
corrugated casing to the extent that the lower end portion of
the non-corrugated casing just overlaps the upper end portion
of the corrugated casing, and then by corrugating the
overlapping portions. This method, which allows successive
connection of additional earth-retaining casings, is easily
applicable for construction of a deep shaft. Further, since
the overlapping ends of the two earth-retaining casings are
corrugated together, the joint gains high strength and
excellent watertightness. (6) The earth-retaining casing having a bottom plate
which is provided with a water inlet and a grout inlet
respectively including a check valve has high strength and thus
prevents deformation thereof during the insertion operation
into the shaft excavated in the ground or into the excavation
casing inside the shaft. Further, the use of this earth-retaining
casing not only saves the concreting and curing
process for the bottom of the shaft, but it can improve
watertightness of the constructed shaft. In addition, mortar
can be filled from above-ground to under the bottom plate
through the grout inlet, and the check valve can prevent the
deposited mortar from backwashing. (7) A tubular guide column, which is set up (on the bottom
plate of the earth-retaining casing or) on the grout inlet in
the bottom plate of the earth-retaining casing in a way to
communicate with the inlet can secure stability of operation
by being used as a supporting member for guiding and holding
the shaft constructing apparatus during the corrugating
operation for the earth-retaining casing. Further, mortar can
be filled from above-ground to under the bottom plate through
the hollow inside of the tubular guide column. (8) The apparatus for constructing a shaft comprises an
expanding means which can be inserted into a cylindrical
earth-retaining casing inserted in the ground and is expandable
and contractible in the radial direction of the earth-retaining
casing, and a moving means for moving the expanding means in
the axial direction of earth-retaining casing. By having this
structure, the shift constructing apparatus can give a
continuous uniform waveform to the earth-retaining casing
while it climbs within the casing by its own force without using
any other moving means. (9) The expanding means comprises an upper expanding
mechanism and a lower expanding mechanism having press molds
which are disposed along the inner periphery of the earth-retaining
casing in a substantially circular manner, and is
expandable and contractible in the radial direction. The
moving means comprises a length-extending mechanism capable
of extending and shortening the distance between the upper and
lower expanding mechanisms. Thus structured shaft
construction apparatus forms a waveform on the earth-retaining
casing by alternately repeating an operation of extending and
contracting the press molds in the upper expanding mechanism
and the lower expanding mechanism and an operation of changing
the distance between the upper and lower expanding mechanisms
by means of the length-extending mechanism. In this case,
since the shaft constructing apparatus can apply corrugation
treatment while climbing within the earth-retaining casing in
a looping movement by its own force, it is not necessary to
provide a separate lifting apparatus, which means simple
construction of the apparatus, and easy and efficient
operation. (10) The expanding means is further provided with a
support column set up in the axial direction of the earth-retaining
casing and a support bar mounted on the support column
in a substantially horizontal manner. Accordingly, the shaft
constructing apparatus can be securely held during the
corrugating operation for the earth-retaining casing so that
a properly shaped waveform can be formed.