Note: Descriptions are shown in the official language in which they were submitted.
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SPECIFICATION
WOR~ METHOD OF IMPROVING OR STRENGTHENING GROUND
[Technical Field]
The present invention relates to a construction work method
for improving or strengthening the soft ground and in particular
to a construction work method for improving the ground by
grouting a self-curing material such ns cements of a high
viscosity or dry consistency into the ground which has been
preliminarily loosened so that the self-curing material is poured
into the ground.
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;~ [Prior Art]
`Various work methods of improving the ground of this type
have been known. The typical work method is the chemical
grouting method. In this method, a chemical liquid is grouted
into the grdund under a low pressure through a grouting pipe
which has been inserted into the ground as ls well kno~m. In
-this case, i~t is the principle that the chemical liquid is
penetrated and grouted into the ground under pressure without
disturbing the ground.
On the other hand, high pressure jetting methods, a
representative work method of which is a so-called jet grouting
method have been widely executed recently. In thi~ high pressure
jetting method, a grout is grouted into the ground simultaneouslY
with disturbing the ground with the high pressure of the grout
or water.
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This high pressure jetting method can also be referred to
as a method of agitating the ground in a wide meaning. On the
other hand, the genuine agitating method is conducted mainly for
the viscous ground. A cement material is supplied through an
agitating shaft having agitating blades or through a separate
supply system while the agitating shaft is inserted into the
ground. The ground area to be agita-ted is replaced with the
cement material or agitated and mixed with sand while the ground
is agitated.
However, the strength and durability of the improved ground
is low since 8 material having a low viscosity, mainly water
glass material is used for the penetration and pressure grouting
in the former chemical pressure grouting work method. The reason
why the strength of the improved ground is low is that the ratio
of the improving material per unit volume is low and the
improving material is nonuniform since the ground is not replaced
with the improving material, but the improving material is
penetrated or gro-uted into cracks in the ground.
There is another problem in that although penetration-
grouting can be usually conducted for the sandy soil layer, the
grout for penetration grouting will often be grouted into cracks
due to slight changes in grouting conditions, resulting in that
the penetration grouting becomes impossible. On the other hand,
if the grout is grouted into a viscous soil layer, it will be
often grouted into cracks, resulting in penetration in unwanted
direction Accordingly, it i5 hard to positively improve only
the desired area and loss of the material due to penetration in
unwanted directions is high. The diameter of the improved body
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is ununiform along the axi~l direction so that the improved body
may be often in the shape of tree or nerve.
In a second high pressure jetting method, the ground is
extremely disturbed and much labor and long period of time is
required for the treatment of the slime (muddy water). If
cutting and grouting is tried to conduct uniformly or discharge
of the slime is tried to sufficiently conduct, it would be
necessary to lower the improving speed and an extended period
time is taken.
Although desired strength of the improved ground is 30
kg/cmZ or higher and 10 kg/cma or higher ~or the sand ground and
viscouq ground respectively, there is A problem in that
variations in strength is very large depending upon the
properties of the ground and the positions of the improved body.
Particularly, in case of the viscous ground, variation in
strength is large due to leaving of lumps of earth which occur
by insufficient cutting of the ground.
A third agitating methodl has a big problem in that a
facility for this method becomeq large in size. In case of the
viscou~ ground, a mixture o-f earth particles and an improving
material will be rotated together with agitating blades so that
the agitating effect is not so high and the uniformity of the
improving strength i8 low. On the other hand, an object o-f the
agitating method is the viscous ground as mentioned above.
Although lt is not impossible to apply this agitating method to
the sand ground, it can not b~ applied to the sand ground without
using any huge agitating means since the resistance of the ground
against an agitating shaft and agitating bladeq is high.
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It is therefore a firs-t object of the present invention to
enhance the strength and uniformity of an improved body, to
enable a simple and compact facility to execute the work and to
form a firm improved body at a restricted or desired position by
a consolidation effect.
It i9 ~herefore a second object of the present invention to
increase the diameter of an improved body by extending the reach
range Oe pressurized wa-ter from a pressurized water jetting
nozzle.
It is a third object of the present invention to provide
an uniform improved body having a large diameter.
Disclosure of the Invention
In accordance with the present invention, an improved body
is formed by grouting a self-curing material of dry con~istencY
having a slump value of 15 cm or less into the loosened ground
under pressure while or after loosening the ground by jetting
pressurized water from a pressurized liquid jetting nozzle
provided at the front end portion o-~ a je~ting pipe which is
inserted into the ground.
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In this case, the improved body can be formed by jetting
pres~urized liquid for loosening the ground to convert the ground
into mud and by elevating and removing the resultant mud by
pres.sure-grouting the sel~-curing material.
-~ The time when the ground is loosened with the pressurized
liquid may be shifted from the time when the self-curing material
is grouted. The jetting and grouting pipe may be formed with a
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grouting opening at the front end portion thereof and be provided
with a jetting nozzle at a position closer to the base portion
than the grouting opening. Loosening of the ground may be
conducted substantially simultaneously with pressure^grouting of
the self-curing material during extracting of the jetting and
grouting pipe.
The jetting pressure of the pressurized water from the
pressurized liquid jetting nozzle may be 50 kg/cm G or higher.
The liquid for loosening -the ground may have an enhanced
cutting ability if water is added with a surfactant.
The materiQl which will form the improved body may be formed
by adding the self-curing material with the removed mud. It is
preferable to separate the removed mud into a supernatant liquid
and condensed mud and to reuse as a ground loosening liquid the
only supernatant liquid or the supernatant liquid which is added
to water. The condensed mud may be added to the self-curing
material so that it can be reused as an improved body forming
material.
If the jetting pipe ha3 two passages, one passage can be
used for supplying the ground loosening liquid and the other
passage can be used for both supplying of bore cutting llquid
when boring and supplying o~ the self-curing material after
loosening of the 8round.
If the jetting pipe has three passages, the first passage
can be used for supplying the ground 1003ening liquid, the second
passage can be used for supplying compressed air to enhance to
ground cutting ability of the loosening liquid and to lift the
mud upward and the third passage can be used ~or supplying the
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self-curing material after loosening of -the ground.
If reinforcing ~teel rods are inserted into an area to be
improved and buried in an improved body, a pile or w~ll can be
provided. If improved bodies are linked, a column arrayed pilar
or a column arrayed wall can be provided.
The present invention is based upon finding that if a self-
curing material is grouted into the ground which has been
loosened once, the consolidated area is enlarged and the strength
of the improved body is enhanced in comparison with the case in
which the ground is agitated simultaneously with grouting and a
grout having a higher unit water quantlty and a higher fluidity
is used like jet grouting method, for example.
If pressurized water is jetted in accordance with the
present invention, the target ground can be loosened. Loosening
of the ground is achieved mainly by discontinuation of the bond
between larger earth particleq and finer earth particles around
the larger earth particles which linking these larger earth
particles. This discontinuation will increase the ratio of
spaces, to which an improving material will subsequently grouted
under pressure.
If an improving material (self-curing material) of dry
consistency having a low slump value is grouted under pressure,
the improving material i~ grouted into the loosened portion of
the ground as if it is forced thereto. The improving material
i3 grouted in such a manner that it will expand the loosened
ground. ~t this time, thé improving materia] is prevented from
moving in unwanted di-rections since the slump value of the
improving material iQ low. The loosened ground portion is
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replaced trith the improving material as i~ that ground is charged
wi~h the improving material. The forcing pressure of the
improving material consolidates the ground portion and more
improving material is grouted into soft ground portion. On the
other hand, less improving material is grouted into the ground
portion having a higher strength since the loosening degree of
that ground portion i9 low. As a whole an improved body having
~niform stren~th and diameter can be thus formed.
On the other hand, the cost for the facility is lower than
those of the high pressure jetting method and the agitating
method since thi~ method can be sufficiently executed by using
a pipe having a small diameter of about 70 mm.
The resultant slime is not a mixed slime of cement with
earth particles which are formed by the high pressure jetting
method, but is a mixture of water and earth particles since
pressurized water is used for loosening the ground. AccordinglYJ
the treatment of the slime is advantageously easy. The cost for
treating the slime can be remarkably reduced as a whole by
separating the slime including only water and earth particles and
by reusing water as pressurized water for loosenin~ the ground
and the ~lurry containing earth particles which are added with
a self-curing material such as cement.
The present invention can be easily applied to the sandy
ground. In thi~ respect, the present method is remarkably
different from the prior art agitating method. The variation in
strength of the improved body which is found in the high pressure
jetting method is eliminated since loosening of a targe~ area of
the ground and pres3ure grouting of the improving material i9
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conducted in different steps or ~tages.
It is necessary ko increase the pressure of the pressuriz2d
water to e~tend the reaching distance of the pressurized water
from the jetting nozzle. Increasing of the pressure enlarges the
size of a pumping facility for the pres~urized water. Even if
the pressure is increased, this will not help extend the reaching
distance so much since the energy of the water will be rapidly
lowered in the ground.
In a second aspect of the present invention, there is
provided a method of improving or strengthening the ground
characterized in that it comprises providing a jetting pipe which
is provided at the front end portion thereof with a projecting
jetting portion which projects in an outer direction from the
jetting pipe at least when pressurized water is jetted toward the
ground to increase the diameter of the loosened ground, said
projecting jetting portion being provided with a jetting nozzle
for jetting pressurized water ~oward the ground in an outer
direction with respect to the axis of an impro~ed body to be
formed, said jetting pipe being formed with a self-curing
material grouting opening at a position closer to the front end
thereof than said jetting nozzle, inserting said jetting pipe
into a target ground to be improved; jetting pressurized water
from ~aid jetting nozzle with said projecting jetting portion
projecting in an outer direction from said jetting pipe while
rotating said jetting pipe around ~he axis thereof and extracting
said jetting pipe in an axial direction thereof to loosening the
ground which is located in an outer jetting direction from said
nozzle for forming a loosened mud column of the ground, and
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grouting a self-curing material of dry consistency from said
grouting opening into said loosened mud column during or after
forming said loosened mud column, whereby to form an improved
body.
There is also provided a method of improving or
strengthening the ground characterized in that it comprises
providing a jetting pipe which is provided on the outer
peripheral surface at the front end portion -thereof with a first
jetting nozzle for jetting pressurized water in a radial
direction and is provided at the front end portion thereof with
a projecting jetting portion which projects in an outer direction
from the jetting pipe at least when pressurized water is jetted
toward the ground to increase the diameter of the loo~ened
ground, said projecting jetting portion being provided with a
second jetting nozzle for jetting pressurized water toward the
ground beyond the outer end of ~he projecting jetting portion in
: an outer direction with respect to the axis of an improved body
to be formed, said jetting pipe being formed with a self-curing
~ material grouting opening at a position closer to the front end
:~ thereof than said jetting nozzle, inserting said jetting pipe
:~ into a target ground to be improved; jetting pressurized water
form said second jetting nozzle with said projecting jetting
portion projecting in an outer direction from said jetting pipe
while rotating said jetting pipe around the axis thereof and
~ extracting .~sid jetting pipe in an axial direction thereof to
loosening the ground which i5 located in an ou~er jetting
direction from said second jetting nozzle for forming a loosened
mud column of the ground, and grouting a self-curing material of
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dry consistenc~ from said grouting opening into said loosened mud
column during or after for~ing said loosened mud column, whereby
to form an improved body.
In this case, the reaching distance of the pressurized water
from said first jetting nozzle may be made longer than the
projecting length of the proiecting jetting portion and said
jet-ting pipe may be inserted into the ground while loosening the
ground by jetting pressurized water -~rom at least the first
jetting nozzle.
The method may include inserting said jetting pipe into a
casing while or after a bore having a radius which is larger than
the distance between the front end of said projecting jetting
portion and the axis of said jetting pipe is bored by using a
casing; removing the casing; and loosening the ground by jetting
the pressurized water from the first jetting nozzle so that the
pressurized water reaches beyond a position where the ou-ter
surface of said casing was located and loosening -the ground by
Jetting pressurized water also from a second jetting nozzle so
that the reaching distance of the pres~urized water is longer
than that from the first jetting nozzle.
Said projecting jetting portion may be collapsible between
a folded position and an outernally extended position along the
axis of the jetting pipe by an operation from the ground surface,
the projecting jetting portion being folded when the jetting pipe
is inserted and being extended when the pressurized water is
jetted from the iettlng nozzle provided on the projec-ting jetting
portion.
In the first aspect of the present invention, the largest
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feature reside~ in that the diameter of the improved body is
increased by jetting pressurized water -~rom the projecting
jetting portion.
In order to loosen the target ground body having a large
diameter only by jetting pressurized water from a pressurized
water jettin~ nozzle provided on the outer periphery o~ the front
end portion of the jetting pipe, it is necessary to increase the
discharge amount of the water by increasing the pressure or to
decrease the discharge amoun-t by reducing the diameter of the
nozzle opening. However, increasing the water di~charge amount
by increasing the pressure will increase the amount of discharged
mud, resulting in that a discharged mud treating apparatus
becomes larger in size and the cost for the treatment is
increased. In case o~ decreasing the amount of the discharged
water by reducing the nozzle diameter, the energy of the
pressurized water is rapidly reduced after it has bee~ discharged
into the ground so that sufficien-t loosening effect can not be
obtained.
If the jetting pipe is provided with the jetting portion
which projects from the outer surface of the jetting pipe in the
second a3pect of the present invention, since the pressurized
water i.~ jetted from the projecting jetting portion, the diameter
o~ the improved body can be made larger by the projecting length
of the projected jetting portion (precisely, the di.~tance from
the outer surface of the pipe to the jetting nozzle) than that
in the case in which the préssurized water is discharged from
a simple pipe having no projecting jetting portion even if the
pressure is not increased, or the nozzle diameter is not
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decre~sed, or the discharge rate of the pressurized water is not
made excessive.
If the jetting pipe is used which is provided with the first
jetting nozzle for jetting pre~surized water in a radial
direction on the outer periphery of the front end portion of the
pipe and is provided with a projecting jetting portion which
projects in an outer direction from the pipe on the base portion
of the pipe with respect to the first jetting nozzle, said
projecting jetting pipe being provided with a second jetting
nozzle, a grea~ advantage can be obtained. In other words, the
ground can be loosened over a distance corresponding to the
reaching distance from the first jetting nozzle if pressurized
water is jetted from the first jetting nozzle when the jetting
pipe i~ inserted into the ground. Therefore, the jetting pipe
can be directly inserted into the ground without any necessity
of boring using a casing. The present method i5 excellent in
working readiness.
In the third aspect of the pre~ent invention, there is also
provided a method of improving or strengthening the ground
characterized in that it comprises providing a jetting pipe which
is provided at the front end portion thereof with a projecting
jetting portion which projects in an outer direction from the
jetting pipe at least when pressurized water is jetted toward the
ground to increase the diameter of the loosened ground, said
projecting portion or the jetting pipe being provided at a
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position below the projecting jetting portion with a jetting
nozzle for jetting pressurized water so that the ground area
which is at least as long as the projecting length of the
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projecting jetting portion is covere~, and said jetting pipe i~
provided with a self-curing material grouting opening at a
position closer to the front end thereof than a lowermost jetting
nozzle; inserting the jetting pipe into the ground; jetting
pressurized water from said je-tting nozzle over a range between
a given depth and the other depth to loosen at least the ground
area corresponding to the projecting length of said projecting
jetting portion for forming a loosened mud column; and thereafter
grouting a self-curing material o-f dry consi~tency under pressure
into said loosened mud column from said grouting opening at said
depth or while the jetting pipe is extracted.
Said jetting nozzle may be provided on the projecting
jetting por~ion in such a manner that it opens downward.
Alternatively, said jetting nozzle may be provided on the outer
qurface of the jetting pipe at a position bealow the projecting
jetting portion in such a manner it opens in a radial direction.
In the third aspect of the present invention, there is a
feature in that the projecting jetting portion or the jetting
pipe below the jetting portion is provided with a jetting nozzle
for jetting pressurized water to cover the ground area over at
least the length corresponding to the projecting length of the
projecting jetting portion in addition to that the jetting pipe
is provided with the projecting jetting portion.
If the projecting jetting portion which projects from the
outer surface of the jetting pipe i provided and the projecting
jetting portion is pro~ided with the jetting nozzle in accordance
with the third aqpect, the reaching distance of the pressurized
water from the axis of the jetting pipe can be made longer
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2~879~3
although the reaching distance of the pressurized water from the
axis of the ietting pipe can be ma~e longer although the reaching
distances of the pressurized water from respective jetting nozzle
are short. Accordingly, the ground can be positively loosened
over at least a length corresponding to the projecting length of
the projecting jetting portion without increasing the pressure
Oe water, or reducing the nozzle diameter, or increasing the
di~charging rate.
If the jetting nozzle i~ provided on the outer surface of
the jetting pipe at a position below the projecting jetting
portion so that it opens in a radial direction, there is no
advantage in respect of reaching diqtance. If the jetting pipe
can not be inserted into the ground in this or former case, this
means that the projecting jetting portion is resisted by the
unloosened ground at this depth position. The loosening of the
ground can be qualified based upon the resistance of the ground
against the insertion of the pipe. If the jetting pipe can not
be inserted into the ground, the groundlcan be positively
loosened over at least a leng~h corresponding to the projecting
length of the projecting jetting portion by reducing the
rotational speed, or the lowering speed o~ the jetting pipe, or
increasing the pressure or the flow rate of the pressurized water
from the jetting nozzle. Since the projecting jetting portion
has an agitating effect to some extent similarly to the agitating
blade in both cases, there is an advantage that the loosening
ability of the ground can be enhanced.
BRIEF DESCRIPTION OF THE DRAWINGS
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2087963
Fig. 1 is a schematic view illustrating a ~irst step o-f a
first embodiment in order of working steps;
Fig. 2 is a schematic view illustratihg a second step of the
first embodiment in order of working s-teps;
Fig. 3 is a schematic view of illus-trating a third step of
the first embodiment in order of working steps;
Fig. 4 is a schematic view illustrating a fourth step of the
first embodiment in order of work:Lng steps;
Fig. 5 is a schematic view illustrating pressure grouting
of a self-curing material;
Fig. 6 is a schematic view illustrating the moving process
of an improving agent;
Fig. 7 is a schematic view of another embodiment;
Fig. 8 is a schematic view of another improving example;
Fig. 9 i9 a schematic view of a further example;
Fig. 10 i9 a schematic view of a further example;
Fig. 11 is a schematic view of an example of reutilization
of mud;
Fig. 12 is a sectional view showing main components of
triple pipe;
Fig. 13 is a schematic view of an example in which grouting
is conducted;
Fig. 14 is a sectional view of a column arrayed pile;
Fig. 15 is a plan view of the column arrayed pile;
Fig. 16 are schematic views showing the steps of another
improving method using an apparatus having agitating blades;
Fig. 17 i9 a schematic view showing a state in which a mud
cclumn is formed in the ground;
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Fig. 18 is a schematic view showing a work condition in a
second aspect of the present invention;
Fig. 19 i9 a schematic view showing a work condition of
another example;
Fig. 20 is a schematic view of a work condition of a further
e~ample;
Fig. 21 is a longitudinal qectional view showing an example
of a jetting pipe;
Fig. 22 is a longitudinal sectional view showing a casing
boring;
Fig. 23 is a longitudinal sectional view showing a
subsequent extracting process;
; Fig. 24 i9 a view showing a improved-jetting pipe;
Fig. 25 is a view showing another improved jetting pipe;
Fig. 26 is a view showing a further different jetting pipe;
Fig. 27 is a schematic view showing a further exampie of a
jetting pipe having agitating blades;
Fig. 28 is a schematic view showing a blade expanding type
jetting pipe;
Fig. 29 is a view ~howing an expanded condition of the blade
- expanding type jetting pipe;
Fig. 30 is a schematic view showing another improved ground;
Fig. 31 is a schematic view showing a further example of
reutilization of mud;
Fig. 32 are plan views showing column arrayed walls or
column arrayed walls;
Fig. 33 is a longi~udinal view of an improved body in
accordance with a method of present invention;
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E~'ig. 34 is a horizontal sectional view of the improved body;
Fig. 35 is a longitudinal sectional view showing an improved
body in accordance with the jet grouting method; and
Fig. 36 is a horizontal sectional view of the same.
BEST MODES FOR EMBODYING THE INVENTION
The present invention will be described by way of
embodiments with reference to drawings.
[~MBODIMENTS]
Now, the present invention will be described by way of
examples with reference to drawings. Figs. 1 through 4 show a
first e~ample of a firqt embodiment. A jetting pipe 2 having a
nozzle 1 at the front end thereof is inserted into the ground to
a given depth as shown in Fig. 1. Thereafter, pressurized water
W is jetted from the jet nozzle 1 under a pressure depending upon
the properties of the ground (soil, softness, etc.) and the
desired diameter of an improved body, preferably a pressure of
50 kg/cm2 or more, more pre~erably a pressure of 80 to 350 kg/cm2
to loosen the target ground when the jetting pipe 2 is extracted
while rotating as shown in Fig. 2. The loosened ground portion
is repre3ented by a reference character S.
Then, after completion of this step, a pressure grouting
pipe 2A is inserted into the loosened target portion as shown in
Fig. 3 and a self-curing improving material G having a slump
value (Japanese Industrial Standards JIS A 1101) of 5 to 16 cm,
more preferably 8 to 15 to form a improved body as shown in Flg.
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A manner for grouting the improving materia~ ~ under
pressure is sho~ in Figs. 5 and 6. Reference numerals 1 to 3
in Fig. 6 show the lapse of time. It is understood from these
drawings that the improving material o~ ~he present invention is
penetrated into the ground in an outer radial direction similar
to paste when the improving material is grouted under pressure.
In the present invention, self-curing improving materials
~uch as cement mortars, cement clays, limes may be used.
Improving materials having a high viscosity are used as mentioned
above.
Cement mortar~ are most preferable among these improving
materials. Various additives such as other organic materials
including fine particle slag, bentnite, foaming agents, frothing
agents, antiseparating agents an~ water reducing agents may be
added to the cement mortar. ~ water-glass or a curing agent for
the same may be further added to the cement mortar at a given
ratio.
In -the first example, the jetting pipe 2 and the pressure-
grouting pipe 2A are separately used. In a second example shown
in Fig. 7, a jetting pipe 20 which is a coaxial double pipe,
including inner and outer pipes 21 and 22 is used. The ground
is cut by mean~ of a cutting bit 29 at the front end thereof
while rotating the pipe 20 and forcing the pipe 20 in a downward
direction so that the jetting pipe 20 is inserted into the
ground to a giv~n depth.
In a subqequent course of extracting of the jetting pipe 20
while rotating, pressurized water is jetted from jetting nozzles
24 provided on the peripheral wall of the pipe at the base end
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thereo~ ~or loosening the target ground. SimultaneouslY ~Jith
this, -the improving material G is pressure grouted from a
grouting opening 25 which opens at the front end of the pipe 20.
A reference numeral 26 denotes a plug for closing a space
between the inner and outer pipes 21 and 22.
Concept of consolidation working will be described with
reference to Fig. 7. A-fter the ground which has been loosened
onece is filled with the improving material G by grouting, the
grouting is further continued. The subsequent improving material
will force the previously discharged improved material in an
outer radial direction, resulting in that the improved ground
including a solidified area Z2 disposed in the center and a
consolidated area Zl of the improving material therearound is
formed as shown in Fig. 7.
Alternatively, the ground can be loosened by jetting
pressurized water while the jetting pipe is inserted if a double
pipe or double passage pipe is u~ed like the second example.
Loosening of the ground in the course of lowering the pipe is
applicable to the first e~ample.
Although a continuous improved body is formed ln the above-
mentioned examples, discontinuous improved stages can be formed
as shown in Fig. 8. In this case, reinforcing of the whole of
the ground by a branched skeleton is aimed.
The pressure of the pressurized water in the present
invention usually means the pre~sure which is detected by a gauze
provided in the vicinity of a pressure grouting pipe or on the
discharge side of a grouting pump. The pressure is preferably
50 kg/cm2 or higher a~ mentioned above. In some cases, the
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pressure is preferably 100 kg/cm2 or higher. The rate of the
jetted water is preferably 5 to 15 l/minute. The jetting pipe
having an outer diameter of 80 mm or less may be used in the
present invention. This is same as the grou-ting tube. In order
to conduct grouting, a hose and the like may be used.
The present invention can be applied-to various construction
works such as reinforcing of a sand area 30 in a sub ba~e course
of a track 31 shown in Fig. 9 and a soft ground below a concrete
building 40 a~Q sho~l in Fig. 10. A reference numeral 32 denotes
ballast.
The pres~urized liquid for loosening the ground is
preferably water in view of availability and cost. Cutting
ability for the ground can be enhanced by adding a surfactant to
water. After the slurry which is generated by the loosening of
the ground is separated into supernatant liquid and condensed
mud, the supernatant liquid may be used for the pressurized
liquid. For example, as shown in Fig. 11, a mud pit 50 is formed
on the ground in the vicinity of the base o-f the pressure jetting
pipe 20, mud 51 which is formed by the replacement with the
improving material G and is elevated between the pressure jetting
pipe 20 and the bore wall i~ pumped out by a pump 52 up to the
pit 60 in which it is separated into supernatant liquid 51A and
condensed mud 51B. The supernatant liquid 51A is added to
pres~urized water W by a pump 54 or only supernatant liquid 51
is supplied so that it may be used for cutting the ground. On
the other hand, the conden~ed mud is supplied to a mixing drum
56 via a hopper 65 and it is mlxed with ~he improving material
G in the drum 56. Thereafter the mud 51B may be supplied to the
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pressure jetting pipe 20 by a pump 67 as a -filling or replacing
modifier material. If the supernatant liquid is used for cutting
the ground in such a manner, the cutting ability is excellent
since it contains fine particles. If the condensed mud is
reused, the slurry treatment efficiency is then lowered. The mud
51 may be added to the improving material G without any treatment
thereof.
Since the used pipe which is a single pipe and has both
functions of the jetting pipe 2 and the grouting pipe 2A which
are independently provided the foregoing case, the ability of
execution of working is excellent. In case of the double pipe
shown in Fig. 7, the outer pipe can be used for supplying the
liquid for loosening the ground and the inner pipe can be used
for supplying the improving material G and for supplying bore
cutting water prior to the supplying of the material G.
A triple pipe 60 shown in Fig. 12 may be used. The triple
pipe 60 includes an outer pipe 61, an intermediate pipe 62 and
an inner pipe 63. A jetting nozzle 60 is mounted upon the outer
wall and an annular air discharging slot is formed around the
nozzle 64. If compressed or pressurized air of 5 kg/cmg or more
- is discharged from the narrow annular discharging slot 65, the
mud 51 is smoothly discharged up to the ground surface by the
smoothly air lift effect and the cutting ability of the ground
is enhanced.
~-~If it is desired that improving material G be positively or
-~more grouted, the improving material G which waq initially poured
or grouted at a lower pressure can be grouted at a higher
pressure by clo3ing the passage for supplying the improving
21
, ' ' ' '' '
2~7~63
material G with a lid Z7 as shown in Fig 27 when the ground does
not accept more grout G. The grouting degree, that is, the
consolidation of the ground can be controlled while monitoring
the pressure by a pressure gauge 28 at this time. It is desired
that the consolidation be conducted prior to curing of the
improving material G since the grout is cured or semi-cured
within several hours.
Since an improved ground having a high strength can be
obtained in accordance with the present invention, a pile
structure having a high strength can be formed. A column arrayed
pile or column arrayed wall can be formed by linking such piles.
In this case, it is preferable to reinforce the improved ground
by inserting one or plural reinforcing steel rods or properly
shaped steel rods (hereina~ter referred to as resinforcing rods).
For example, as shown in Figs. 14 and 15, the column arrayed pile
or column wall can be formed by burying reinforcing rods 70
including one or plural reinforcing rods or properly 3haped steel
members in each of improved ground Z and by overlapping the
improved ground~ Z. The jetting pipe which was used for feeding
the improving material is left in the ground as the reinforcing
rods so that it can be used for reinforcing the improved ground.
The pre~ent invenkion can be embodied in combination with
mechanical agitating mixing means.
For e~ample, the ground is cu-t and bored to a given depth
by means of a cutting rod 80 having a cutting bit 82 at the front
end thereof as shown in Fig. 16. Of course, cutting and boring
is preferably achieved while loosening the peripheral ground by
an jetting nozzle 83 which is provided below the cutting bit 82.
2~
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~87~
Then, the improving material G is dropped by gravity or is
grouted under pressure in the course o-~ extracting as sho~m in
Fig 18 This provides a improved ground as shown in Fig 19
The rod 80 may be provided with agitating blades above the
cutting bit 82 so that they project from the rod 80.
In the foregoing ~`irst embodiment, the reaching distance of
the pressurized ~ater is limited even if the jetting energy of
the pressurized water is increased. Accordingly, it is hard to
provide an improved ground ha~ing a large diameter
Therefore, it is preferable to adopt a second embodiment
which will be described hereafter if an improved ground having
a large diameter is obtained.
A firgt e~ample of the second embodiment will be described
with reference to Figs. 1, 17 and 18 As shown In Fig 1, a
loosening pipe 2 having a cutting bit at the front end face
thereof and pressurized water jetting nozzles 1 on the peripheral
wall of the front end portion thereof is inserted into the ground
to a predetermined dep~h. Thereafter, pressurized water W is
jetted for loosening the target ground to ~orm a looqened mud
column under a pressure depending upon the properties of the
ground (soil, softness, etc.) and the desired diameter of the
ground to be improved, preferably 50 kg/cmZ or higher, more
preferably 80 to 350 kg/cm2 in the course of extracting the
loosening pipe 2 while rotating of the pipe 2 as shown in Fi~.
17. The primary loo~ened area is represented by a reference
character Sl. If ~he improved area is below the level of the
ground water, the resching distance of the pressurized water is
remarkably short. Even if water i jetted under a pressure of
23
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,
.
2 1~ 3 ~
200 kg/cm2, for example, extending of the reaching distance can
be achieved by making the jetting pipe 2 of a double pipe and
ietting air around the pressurized water like jet grouting method
since the diameter of the improved ground is about 40 cm.
If this working step is completed, the jetting pipe 3 is
forced into the loosened mud column as sho~n in Fig. 18. The
jetting pipe 3 is provided in the vicinity of the front end
thereof with a projecting jetting portion 30 which projects from
the pipe in an outer radial direction at least when water i~
jetted to increase the diameter of the improved ground. The
projecting jetting portion 30 is provided with a jetting nozzle
31 for jetting pressurized waker upon the loosened ground in an
outer radial direction. The jetting pipe 3 is further formed at
the front end beyond the projecting jetting portion 30 with a
grouting opening 32 for grouting a self-curing material.
After the jetting pipe 3 has been inserted into the improved
target ground, the pipe 3 is extracted from the ground in an
a~ial direction and rotated around the axis of the pipe as shown
in Fig. 18. In the course of this extraction of the pipe, the
ground which i~ in the outer jetting direction of the jetting
nozzle 31 is loosened with the jetting pressurized water from the
jetting nozzle 31 while the projecting jetting portion 30
projects in an outer rad~al direction. Thus loosened area will
be referred to as secondary loo~ened area and i~ represented by
a reference character S2.
While the loo~ened ground i~ formed, a improved body A is
formed by preqsure grouting the above mentioned self curing
material G of dry consistency. Formation of the improved bod~
.
24
, ' ; ' ' '
2~8~9~
A is conduc~ed up to the ground surface or a predetermined depth
position.
In this ca~e, pressure grouting of the self-curing grout is
conducted while the jetting pipe 3 is gradually extracted upward
from the bottom of the mud column in such a manner that the self-
curing grout G is gradually deposited upon the bottom. Grouting
should be conducted while a predetermined depth of the immersion
of the jetting pipe 3 in the self-curing material G is kept. The
immersion depth is preferably 30 cm or more, more preferably 50
cm or more.
In the first example of the second embodiment, the loosening
pipe 1 and jetting pipe 3 are separately used. A second example
in which formation of the primary and secondary loosened areas
Sl and S2 and grouting of the self-curing material ~ is conducted
by the same jetting pipe 3A i3 illustrated in Figs. 19 and 10.
The jetting pipe 3A in the second example of the second
embodiment comprises inner and outer pipes 33 and 34 shown in
Fig. 21, for example, as main components. Aipassage member 35
is provided be-tween the inner and outer pipes 33 and 34 in such
a manner that a passage for the self-curing material G is formed
in the inner pipe 33 and passages of the pressurized water for
the first and second jetting nozzles 31A and 31B are ~ormed.
The first jetting nozzle 31A is provided on the outer
periphery o~ the jet~ing pipe 3A. An outwardly radially
projecting jetting portion 30 is integral with the outer pipe 34
above the first jetting nozzle 31A similarly to the above
mentioned first e~ample. The radially projecting je~ting portion
30 is provided with a second jetting nozzle 31B for jetting
2~
~; , . . .
..
.
.
.' ~' ' ' ' .
2 ~ 3
pressurized water in an outer radial direction beyond the outer
end o-f the projecting jetting portion 30. The jetting pipe 3A
i~ further formed with a ~el~-curing material grouting opening
32 at the front end thereof below the first je-tting nozzle 31A.
If such a jetting pipe 3A is used, the jetting pipe 3A is
inserted to a predetermined depth of the ground while jetting
pressurized water from the first jetting nozzle 31A as shown in
Fig. 19. At thi~ time, cutting and boring water is discharged
from the grouting opening 32. If the jetting pipe 3A reaches at
the predetermined depth, pressurized wa-ter is jetted from only
the second jetting nozzle 31B and the self-curing material G is
grouted from the grouting opening 32 while rotating and
e~tracting the jetting pipe 3A as shown in Fig. 20 so that the
secondary loosened area S2 is formed around ~he primary loosened
area Sl. An improved ground A having a prede-termined length is
formed of the self-curing material G.
Figs. 22 and 23 show a third `example of the second
embodiment. Prior to insertion of the jetting pipe 3 into the
ground, boring is preliminarily conducted by using a casing
having a diameter which is larger than the distance between the
front end of projecting jetting portion 30 and the axis of the
jetting pipe. Thereafter, the je~ting pipe 3 is inserted into
the casing 4 and the casing 4 i~ then removed. The ground ia
loosened by ie~ting pressurized water from the jetting nozzle 31
and the self-curing grout G is pressure grouted from the grouting
opening 32 while rotating and e~tracting the jetting pipe 3.
In accordance with the present invention, a plurality of,
for example two radially projecting jetting portions which are
'-
26
2~87~
spaced in a longitudinal direction of the pipe may be provided
as shown in Fig. 24. In this case, insertion area for the
projecting jet~ing portion 30A is formed by loosening of the
ground by pressure water from the first jetting nozzle 31A. The
insertion area for the radially projecting branch 30B is formed
by the pressuri~.ed water from the second jetting nozzle 31B.
Finally, pressurized water from the third jetting nozzle 31C
forms an improved ground having a diameter larger than the
projecting length of the projecting jetting portion 30B. In this
example, it i.~ not necessary to insert the jetting pipe 3 again
after the ground is firstly loosened by the loosening pipe 1
unlike the first example of the second embodiment. Insertion of
the jetting pipe 3 loosening of the ground and grouting of the
self-curing material from the grouting opening 32 after reaching
at the lowermost position can be carried out by using only the
jetting pipe 3C.
Developing this concept, an e~ample shown in Fig. 25 is
possible in which, for example, cone shaped projecting jetting
portion 30C i~ provided and jetting nozzles 31E ... which are
provided on the sloped surface thereof are used for loosening the
ground so that the jetting pipe 31 can be inserted and
pressurized ~ater is jetted toward the peripheral ground from
jetting nozzles 31D on the outermost periphery thereo~.
Alter~atively, jetting nozzles 31E which face downward may
be provided on ~he lower surface of a radially projecting jetting
portion 30 and may be used for loosening the ground so that the
jetting pipe 3C can be inqerted as shown in Fig. 26.
Fig. 27 shows an example in which an agitating blade 40 is
27
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', ' : '; '
. . . ~ ~ . .
,
~8~
provided above the projeoting jetting portion 30. The agitating
blade 40 will further loosen the loosened ground. The blade can
be used aq an indexing member for determine the resiqtance of the
ground since it can be determined that the loosened ground does
not have a predetermined value il the resistance of the ground
against the rotatiorl of the jetting pipe 3C is excessively high.
Although the projec~ing jetting portion initially projects
in an outer radial direction from the pipe in the foregoing
examples, it suffices for the projecting je-tting portion to
project iIl a outer direction from the pipe at least when it jets
pres~urized water to enlarge the diameter of the loosened ground.
As shown in Figs. 28 and 29, the jetting portion does not project
from the pipe up to a given dep~h. For example, a blade having
a blade expanding link mechanism blade 41 is provided below a
given depth. The expanding link mechanism blade can be expanded
a~ shown in Fig. 29 at the time when the diameter is desired to
be increased.
Forcing the outer pipe 42 do~mward from the ground surface
enables the blade to be expanded. A reference numeral 43 denotes
a bore cutting blade.
If the diameter of the improved body is increased only over
a given length of the pipe in a depth direction of the ground,
the diameter of the bore in the vicinity of the ground surface
may be ~maller while the diameter of the formed improved ground
may be larger ~g shown in Fig. 30.
In the example of Fig. 24, 27, 16, an improved ground is
formed by pre~ure grouting the self-curing grout from the
grouting opening 32 of the jetting pipe which has been inserted
'
28
~ . . .
,
2a~7~3
to a given depth. ~lthough it is possible to pressure grout the
self-curing material by means of the separate exclusively used
pressure grouting pipe. Ea~iness of execution of work is
remarkably lowered.
If the lowermost ietting nozzle is separated ~rom the self-
curing grout grouting opening 32 at a distance of at least about
50 cm, preferably 1 m or more in the foregoing examples, no
interference between the pressurized water and the self-curing
grout G arise~ re~ulting ln that an excellent improved ground can
be obtained.
Also in the second embodiment, mud which was generated by
loosening of the ground and pres.~ure grouting of a self-curing
material is separated into supernatant liquid and condensed mud
and thereafter the supernatant liquid may be used. This e~ample
is shown in Fig. 31.
In other words, a mud pit 50 is provided in the vicinity of
the base or upper end of the pressure jetting pipe 3. The mud
51 which has been lifted between the pressure jetting pipe 20 and
the bore wall by the replacement with the self-curing material
G is pumped out by a pump 52 and is separated into supernatant
liquid 51A and condensed mud 51B. The supernatant liquid 51A is
temporarily reserved in a tank 58 by a pump 54 so that it will
be used as pressurized water for forming next loosened mud
column. Using the supernatant liquid for cutting the ground
makes the cutting efficiency higher 3ince it contains fine
particles.
On the other hand, the condensed mud 51B is supplied to a
mlxing drum 56 via a hopper 5~, where it is mixed with the self-
29
.
. . ' .
2~7~
curing material G. Thereafter the mixture c~n be supplied to thepre~,~,ure jetting pipe 20 as filling or replacing self-curing
grout by the pump 57. If the condensed mud is reused, the
treatment of the muddy water i~, correspondingly reduced. The mud
51 can be directly added to the self-curing material G without
being treated.
Since an improved ground having a high strength can be
obtained in accordance with the present invention, a pile having
a high strength can be formed. Various column arrayed piles or
column arrayed walls (continuous wall) can be formed as shown in
Fig. 32 by linking these colunns. In this case, it is preferable
to reinforce the impro~ed ground by inserting one or plural
reinforcing rods or properly shaped steel members into the
improved ground a3 well as forming the improved ground of only
the self-curing material. When a column arrayed pile or a column
arrayed wall is formed, the plural jetting pipes are held by a
single lifting machine since each of the pipes has a small
diameter and a light weight. An improvement in the ground can
be achieved by jetting pipes simultaneously.
After the ground has been loosened in the foregoing example,
only grouting of the self-curing grout may be conducted while
jetting of the pressurized water from the jetting pipe is stopped
and the jetting pipe is fixed at the depth position.
In a third embodiment of the pre~ent invention, a mud column
is formed while in~erting a jetting pipe having a projecting
jetting portion into the ground without preliminarily forming a
mud column.
A first example of the third embodiment will be described
-
.
,~
with reference to ~igs. 19 and 20. A jetting pipe 3A has a bore
cutting bit at the front end face thereof and a pressurized water
jetting nozzle 31A on the peripheral wall in the vicinity of the
front end thereof. The jetting pipe 3A is further provided with
a projecting jetting portion 30 which projects in an ou-ter radial
direction at least when the diameter of the loosened ground is
increased by jetting. The projecting jetting portion 30 is
provided with a jetting nozzle 31B for jetting pressurized water
outwardly with respect to an axis and the jetting pipe 3A is
formed with a self-curing grout grouting opening 32 at the front
end below the jetting nozzle 31A.
- Such a jetting pipe 3A is inserted into the ground at a
predetermined depth while rotating the pipe and jet-ting
pressurized water from the first jetting nozzle 31A as shown in
Fig. 19 so tha~ the reaching distance is as long as or longer
than the length of the projecting jetting portion 30. At this
time, bore cutting water may be discharged from the grouting
opening 32 according to needs. The ground is loosened by jetted
pressurized water and a mud column which is referred to as
primary loosened area Sl is formed.
If the jetting pipe reaches a given depth, a secondary
loosened area S2 i~ formed around the primary loosened area Sl
by jetting pres~urized water ~rom only the second jetting nozzle
31B and the self-curing material G is grouted from the grouting
opening 32 while rotating and extracting the jetting pipe 3A.
- An improved body A having a predetermined length is formed of the self-curing material G.
The pres~urized w~ter W ~rom both jetting nozzles 31A and
31
......
~g7~3
31B may be at a pressure of 80 to 350 kg/cmZ depending upon the
nature of the ground (soil, softness, etc.) and the diameter o-f
the desired improved body similarly to the foregoing examples.
(Experimental Example)
The present inventors made experiments for improvement in
crushed stone dust buried ground as follows: ground loosening
liquid: pressurized water (pressure 200 kg/cma), the rate of
jetted water: 80 liter/minute, cutting speed: 30 minutes/m,
used improving material3: cement, bentonite, sand cement-
bentonite mortar. On the other hand, an improvement was made by
so-called CCP work as a comparative example.
After several days since the execution of work, solidified
body was dug out for observing the improved condition thereof.
The resultant body of the present invention had the configuration
qhown in Figs. 33 and 34. In contrast to this, a resultant
solidified body of the comparative example was irregular in
configuration as shown in Figs. 35 and 36. A multiplicity of
lumps of earth were left in the solidified body as shown in the
drawing so that the uniformity of the body was poor. The
experiment~ showed that an improved solidi~ied body having an
ideal configuration could be provided in accordance with the
present invention in comparison with the prior art.
Industrial Utilization
Aq mentioned above, the present invention provides an
advantage in that a uniform and firm improved body having an
enhanced ~trength can be formed at a limited or de~ired position
due to qolidification effec~ by execution of work using a simple
and compact facili~y. Further an improved body of the ground
- ' ~ ,
'' ~
;
20~79~3
having a large diameter can be po~itively formed.
33
,.
. .
:
