Pipe jacking specialist in Cyprus
Pipe jacking specialist in Cyprus
حفاری-به-سبک-پایپ-جکینگ
Ku kuma pipe jacking drilling, tihlanganisi na hina eka 00989012040741
Pipe jacking i endlelo ra xiyimo xale henhla ro veka tiphayiphi ta le hansi ka misava, ti ducts na ti conduits ta gezi na vuhlanganisi bya riqingho.
Araz Technical, khontraka ya ku bora ya tiphayiphi leyi rhangelaka
LUBRICATION
The pipe jack shield or machine
is designed to produce a small
overbreak to the external diameter of
the pipeline. By injecting a lubricant,
for example bentonite, into this
annulus the pipeline can, in theory, be
jacked freely through a fluid medium.
In practice, however, fluid losses may
occur into the surrounding ground.
Providing these can be controlled,
the technique results in considerable
reductions in jacking forces and
therefore longer jacking lengths.
JACKING LOADS
Loads required to jack the pipeline
forward are mainly a function of
frictional forces built up around the
pipeline. These forces depend on the
type of ground and, in particular, its
arching characteristics, friction angle,
the depth of overburden, the depth of
the ground water and any surcharge
load, the length and diameter of the
pipe being jacked and the time taken
for the operation.
Whilst it is difficult to accurately assess
these forces using soil mechanics
theory, pipe jacking contractors
have, after years of experience,
derived empirical values. As a guide,
frictional forces fall between 0.5
and 2.5 tonnes per square metre of
external circumferential area. The use
of sophisticated lubricant injection
techniques can reduce frictional forces
to as little as 0.1 tonnes per square
metre.
Frictional forces on the pipeline
may be reduced by applying a
suitable lubricant, under a nominal
pressure above that of the ground
water pressure present. If high
frictional resistance is anticipated, it
is recommended that intermediate
jacking stations are placed at regular
intervals in the pipeline.
These jacking loads must be resisted
by a jacking reaction built up within
the thrust shaft. This is normally
achieved by the construction of a
thrust wall at the back of the thrust pit
designed to withstand the anticipated
jacking load and to suitably transfer
such loading through the shaft
structure to the surrounding ground.
