Note: Descriptions are shown in the official language in which they were submitted.
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T I "-L,k._O E' _T ~I E__l`JVENT I ON
L0~1 [ ~D _IPE FOE~_IPE TA_K ~G
The present invention relates -to a pipe of socke-t and
spigot -type adapted for pipe jacking ancl havincJ a spigo-t
whose internal and external diameters are larger than
-those of the pipe body.
Pipe jacking is a methocl for burying a water main.
The rear end of a rnetal straigh-t pipe is inserted in the
ear-th almost horizontally at a launch pit. Pressure is
applied by a hydraulic jack or ~he like wi-thou-t excavating
the ground. The spigot of the nex-t straight pipe is joined
in the socket at -the rear of the preceding pipe. I`he
pipes are :inser-tecl in the earth ancl pressure is appliecl by
L5 the hydraulic jaclc. 'rhese steps are repeated to ~orm the
requirecl pipe line.
In -this method a drawback is that ~ecause of the
enlarged spigot of the pipes, considerable resistance is
unavoidable during forward movement under the ground. To
overcome this a circumférential flange has been provided
on the spigo-t of each pipe to receive -the driving force
and the outer periphery of the pipe is coated with cement
mortar so -tha-t the outer periphery of the pipe be-tween -the
flange on the spigot and the socket is almost the same as
the larges-t external diameter of the socke-t. O-ther
countermeasures, for example welding of ribs between the
flanye on the spigot and pipe body, incorporation of
reinforcing rods in the coating cement mortar have also
been used to provide reinforcement.
These conventional pipes for pipe jacking still ha~e
various disadvantages, for example instability of the
mortared surface and an intricate manufacturing or
assembling process. To mee-t -these disadvantclges applican-t
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hc~s proposed an 1mproved pipe aclaptecl for pipe jacking.
This improvecl pipe has a spigot prov:iclecl with an annular
flarlge arld reinforced with a rib. Ar- outer pipe has
smooth external surface and is fixed a-t the ou-ter edge
5 be-tween the spigot and the socket in longituclinal
direc-tion. An annular CJap between the outer pipe ancl the
pipe body is filled with a filler such dS sancl or foaming
mortar. As a resul-t several advan-tages are aehievecl. E`or
example frictional resistance between the outer surface of
the pipe and -the earth is reduced enabling the pipe to be
easily movecl forward by pipe jacking, loss of -the cement
mortar is prevented, and manufacturillg ancl carrying of the
pipe is easy.
The above improved pipe overeomes -the disadvantages
of the known ancl customary pipe eoatecl with eement mortar,
bu-t progress in the field of pipe line laying has brought
several eonclitions cl:ifferent from the eonventional pipe
jaeking ancl i-t is now necessary to review pipe
requirements. For example, a pipe replaeement method
without open art has been developed. Aeeording to this
new method, when old pipe line beeomes obsolete, i-t is
replaced with a new pipe while crushing and removing the
old pipe. This differs from the eonven-tional pipe jaeking
whieh is employed only when new pipe line is eonstrueted
without exeavation.
In pipe jaeking as described above new pipe to be
jaeked is moved forward in the horizontal eavity already
provided under the ground by the old pipe line. Thus the
required jaeking foree ean be mueh smaller than in
conventional pipe jaeking. Aecordingly, it is not always
neeessary to provide a flange on the spigot of the new
pipe. Moreover, in the assembling proeess, it is difficult
to fit an outer pipe, serving as an ou-ter easing, over the
pipe body if there is a flange or rib present. In
partieular, it will be very clifEieult to fill the spaee
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clefinecl hy the :ElancJe on the spigot, the socket and -the
pl.pe with a .fi.ller wllile exhaus-ti.ng the air.
F,ven in the conven-tional constructiorl by pipe
jacki.ng, the cl:Lstance of pipe jacking may be shor-t, for
examp:Le, when just crossing a road or a railroad. The
re~uired jackincJ force can thus be very small. In -these
cases, it is not: always reasonable to provi.de a flange on
the spigo-t.
The present inven-tion seeks to solve the above
problems by providing an improved pipe of low load for
pipe jacking.
The invention provides a :Low .Load pipe for pipe
jacking, cornprising, a pipe body havi.ng an :internal
diame-ter and an external di.ame-ter, sa:id pipe bocly
includiny a socket sec-tion with a projec-ting annular rib
at an external edge of the socket defining an external
diameter, and a spigo-t section wi-th an outer periphery;
said socket section having an internal diameter and an
external diameter larger than the ex-ternal cliameter of
saicl pipe body, and said spigot section having a length
slightly longer -than the length of the socket sec-tion; and
an outer pipe having a smooth external surface and an
external diameter almost equal -to -the external diameter of
said projecting annular rib, and a plurality of projec-ting
outer rails projecting from its internal diameter,
said pipe body, with said socket section and said
spigot secti.on, defining a gap with said outer pipe which
is filled with a filler material which adheres to said
projec-ting rails, said filler mater:ial being retained in
said gap.
More speci:Eically it is preferable tha-t the filler be
a self-curing material. It is also preferable that either
an area in the vicinity of an end o:E -the outer pipe, on
the spigo-t of the in-ternal pipe or areas in the vicinity
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of both enclx thereof, are filled with a filler of sel-~-
cul-incJ material, and the remainir~g area filled with a
filler of non-self-curing Itlaterial. It is further
preferable that -the end of the ou-ter pipe on the spiyot
side of -the internal ~ipe is bent to contact the outer
periphery of -the internal pipe. It :LS yet fur-ther prefe-
rable that the inner periphery of the outer pipe be
provided with annular projecting rails.
Since it is sufficient for the pipe accorcling to the
present invention to meet the minimum requirements for
endurance -to low load as mentioned above, the
manufacturing thereof is simple ancl weight is reduced,
which iS advantageous in transportation and constructit>n.
As for the aclvantacJes in manueacturing and assemb:ling
the pipe, since -the spigot is not proviclecl with a flange
or rib, mounting of -the outer pipe on the inner pipe is
easy.
It is also advantageous that filler can be vertically
poured into an annular gap be-tween the ou-ter pipe and the
pipe body by erecting the pipe body with its socket down
on the ground and mounting the outer pipe on the ou-ter
periphery of the pipe body. This filler pouring method is
better than the conventional method of filling the closed
space with filler while the pipe is hori20ntal.
As for -the advantages in and after -the cons-truction
process, a pipe is joined -to a preceding pipe in a line
contact at the front end of the spigot section. This
differs from the face contact joint between a flange
portion on the socket end face and a flange fixed to the
spigot in the prior art. Thus some flexibility is given
by the line contact and allows the pipe to follow a
certain irregu:Larity in the forward movement of the pipes.
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IE :Lt. is necessary to fab.ricate a shor-ter pipe by
cutting a stanclarcl Lerlg-th pipe at the cons-truction site, a
flange and rib neecl no-t be attachecl to the spi.got sicle of
the shortened p:Lpe as irl the prior ar-t. Any sho:rter pipe
can be easily fab.ricatecl a-t the cons-truction site and the
equipment necessary for such fabrication can be
sirnplifiecl.
The invention ancl the prior ar-t a.re i]lustra-ted in
the draw1ngs, in which:
Figure 1 is a fron-t sectional view iilus-trating an
embocliment of the present invention;
Figures 2, 3 and 4 are front secti.onal views
illus-trating further emboclimen-ts of the invention;
Figures 5 A and B are a parti.ally sec-tiona:L front
view ancl a plan view to il].us-trate the inventi.on;
Figure 6 is a fron-t seetional view i:Llust.rati.ng the
prior art; and
Figure 7 A and B are sections illustrating the more
recent pipe line replacement method withou-t open cut.
Diseussing the prior part first, Fi.gure 6 illustrates
the recent prior art. This improved pipe has a spigot 4a
provided with an annular flange J.2 and reinforeed wi-th a
rib 13. There is an outer pipe 5a having a smoo-th
external surfaee fixed at the outer edge between the
spigot 4a and a soeke-t 3a in longituclinal direction. An
annular gap formed between the outer pipe and pipe body is
filled with a :Eiller 6a such as sand or foaming mortar.
: The aclvantages achieved include reduetion in frietional
xesistance between the outer surfaee of the pipe and the
ear-th, enabling the pipe to be easily moved forward by
- pipe jaeking, preven-tion of loss of the eement mortar and
; simplifieation of manufaeture and earryi.ng of the pipe.
s indicated above, although the prececling improved
pipe overeomes -the clisadvantages of -the known and
cus-tomary pipe coated with cement mor-tar, progress in the
131D00413
f:Lelcl o~ pipe laylnl has introduced several cond:itions
(-Iifferent from t,hf~ conventioncll pipe jacking. liowever,
accordincl to even more recen-t development, when old pipe
line become obso:Lete, it is replaced with new pipe wh:ile
crushing and removing the o:Ld p,ipe. Figures 7A, 7s StlOW
an exdmp:le o the new pipe replacemen-t method. In Figure
7 A, a mole 15 moves forward into àn old pipe line 14 and
crushes i-t. Temporary pipes 16 are connec-t,ed to the rear
of the mole ànd follow the mole to be placed where the old
pipes have been crushed. As illus-trated in Figure 7B,
after completing replacement of the old pipe line wi-th
temporary pipe~, new pipes lb are insertecl one by one from
a launch pit 17 and -the rear parts of pipes lb are pushed
Eorward by a hydraulic Jack l8. The first temporary pipe
16 is p~lshecl out to an reCept;Lon pit 19 to be removed
to outside. These steps are repeated un-til complete
replacement of the temporary pipes by a new pipe line is
completed. The disadvantages of this procedure are
described generally above. Figure 1 shows an ernbodiment
of the present invention. A pipe 1 for pipe jacking
comprises a straigh-t pipe body ~ and a socket 3 having
internal and external diameters both larger than those of
-the pipe body 2. Ano-ther end of the pipe body 2 as a
spigot 4 to be inserted and joined into the socket of the
preceding pipe.
The outer periphery o:E the pipe l is covered wi-th an
outer pipe 5 having a smooth external surface and an
external diameter almost equal -to the maximum external
diameter R of the socket in such a manner -that the spigot
section 4 may be a little longer than the enlarged portion
L of the inner diameter of -the socket. A gap between -the
outer pipe 5 and the ou-ter periphery of the pipe body 2 is
filled with a filler 6.
A preceding pipe lA comes in contact with a
succeeding pipe lB receiving a pressing force from the
rear at the deepest part of the socket of the preceding
~L3~0048
pipe IA. The press:Lng ~orce is -transmitted Erorn a
c:Lrcurnference ~ormed of the front end 7 of the ~pigo-t 4 of
-the succeeding pipe ls to the ci.rcumference of -the deepest
part of the socket sec-tion of -the preceding p1pe 1~. In
the low load pipe jacking method like Ihis embodiment, -the
-transmission of pressing force tangen-tially between -the
front end of the spigot secti.on and the deepest par-t of
the socket section is quite suf:Eicient for the required
performance. It is also sa-tisfac-tory ~or additional parts
(outer pipe and filler) of the outer periphery to absorb
increasing resistance during the forward movemen-t by the
pipe producecl as a result of enlargement of the diameter
of the socket, especially with reduction of resistance by
their smoo-th surfaces.
Since the addl-tions to the pe.riphery of the pipe are
not required the internal section of the outer pipe 5,
which may be as a spiral duc-t having a smooth surface or a
liner of vinyl chloride, can be easily filled with a
filler, ancl retention of the filler is the only
requirement. To meet this requirement, it is customary to
use self-curing materials, for example cement mortar,
resin mortar and foaming cemen-t. It is also preferable
that, as illustrated in Figure 2, the socket side 6A be
filled with mortar, the in-termediate section 6B with sand,
and the spigot 6C with mortar, respectively. It is
further preferable that only the spigot side 6c be filled
: with mortar and the remaining parts wi-th sand.
Figure 3 shows an embodiment in which the end of the
outer pipe 5 on the spigot side of -the pipe 4 is ben-t
toward its axis to form a flange 8 in contact with the
outer periphery of the pipe 4. Filler is confined inside
this flange. In this embodiment, it is necessary to
provide a hole 9 through which air i.nside is exhausted and
fille.r can enter.
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FicJure 4 shows a further embodiment in which projec-
ting rails lO are annular]y provided on the inner
periphery of the outer pipe 5. As in Fig l, the SpicJot
section 4 may be sligh-tly longer -than -~he enLarged portion
Ll, and the gap between the outer pipe 5 and -the outer
periphery of -the pipe body 2 is filled with a filler 6
which is retained. The annular rails 10 provide good
adherence of the outer pipe 5 -to the filler 6. This
proves helpful when it is considered that -the o~ter
surface of the outer pipe S enyages the surrounding soil
during the jacking process. Also, iE a detachment of -the
outer pipe S did occur with respect to the filler 6, the
ribs 10 would prevent relative movement of -the two.
The invention has the foLlowing advantages: In the
embodiment of Figure 2, as the intermedia-te par-t is fillecl
with sancl for joining a branch pipe to the pipe boss only
cutting the outer pipe and removal of the sand from inside
is required. When lifting a pipe to carry it, the thin
outer pipe is prevented from deformation due to deacl
weight by putting a wire round the mortared part.
In the embodiment shown in Figure 3, positioning is
easily carried out just by engaging the outer pipe on the
pipe, which results in easy manufact-ure ancl assembly.
In the embodiment shown in Figure 4, as the retaining
function between -the outer pipe 5 and the filler 6 is
increasedj there is no disadvantage such as displacement
or burring of the outer pipe due to frictional resistance
in construction process.
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