UNITRACC - Underground Infrastructure Training and Competence Center

Pressure chamber

A pressure chamber

has the tasks to compensate the pressure difference between atmospheric pressure in the shaft and the external groundwater inside the subsoil without damage and
possesses two locks and an integrated gasketed opening seal

(Table: Functional principle of a pressure chamber [FI-Steina])

Sep 15, 2008

Closed pressure chamber - flanged or welded in the shaft

In this variant, a pressure resistant steel container is fastened to the inside wall of the shaft and this is closed to the inside wall of the shaft by means of a blind flange and at the outer side by means of a removable lining in the form of sheet piles or the special prepared lining region for traversal of the microtunnelling or shield machine in the region of the exit and entry opening.

Depending on the method of opening, the gasketed opening …

Sep 15, 2008

Pressure chamber - variants

Closed pressure chamber

flanged or welded to the inside of the shaft
integrated into the shaft wall

(Image: Exit lock in the form of a closed pressure chamber flanged to the starting shaft [Stein05a])

Open pressure chamber

welded inside the shaft
pre-shaft (trough desing)

(Image: Open pressure chamber welded to the inside of the shaft)

Sep 15, 2008

Closed pressure chamber - integrated in the shaft wall

A special solution for microtunnelling with nominal sizes of jacking pipes up to a maximum of DN/ID 800 is the closed pressure chamber. This closed pressure chamber is integrated into the shaft face from open sinking shafts, which are made of prefabricated reinforced concrete shaft rings, by the factory.

The actual sealing element consists of an elastomeric seal, which, depending on the function of the opening is arranged either inside (exit opening) …

Sep 15, 2008

Open pressure chamber - welded to the inside of the shaft

The pressure chamber is sealed to the inside of the shaft by means of a steel box open welded to the sheet pile wall and open at the top. The top edge of the steel box must be above the maximum level of groundwater to be expected. The opening of the pressure chamber to the subsoil is carried out after traversing the gasketed opening seal by means of pulling the interlocked sheet piles between the welded seams up to the top of the microtunnelling …

Sep 15, 2008

Open pressure chamber - pre-shaft (trough design)

For pipe jacking of larger diameters with a complicated machine technology, which is installed in several trailing shield segments (e.g. installation of pressure locks when jacking under compressed air, so-called watertight pre-shafts are often constructed in order to reduce the starting shaft dimensions and costs and these permit keeping the distance required for full installation of the machine technology free of water [Konra01].

(Image: Possibilities …

Sep 15, 2008

Compressed air chamber

a pressure-tight shut shaft functions as compressed air chamber to support the in-situ groundwater pressure when opening the exit and entry openings

The exit and entry openings are previously created during the construction of the reinforced concrete sinking shaft and made watertight for the sinking procedure.

(Image: Attention!)

Depending on the jacking technique at the shaft, the sealing of the exit and entry openings …

Sep 11, 2008

Entry and exit openings

Sep 15, 2008

Structural calculation

Design of the abutment - examples of lined shafts

(Image: Principle sketch of a jacking station for microtunnelling with auger spoil removal installed inside the starting shaft) (Image: Examples of abutment designs - Abutment in the form of a reinforced concrete plate and an in cast concrete block during pipe jacking [TUGraz01])

Sep 15, 2008

Structural calculation

Design of the abutment - examples of unlined shafts

(Image: Abutment design without shaft - Sketch [PJA83]) (Image: Abutment design without shaft - Of rammed sheet piles with filling and load distribution plate in front [FI-Zübli])

(Image: Abutment design without shaft - Plan view with backfilled intermediate spaces [FI-Zübli]) (Image: Abutment design without shaft - Front view [FI-Zübli])

Sep 11, 2008

Structural calculation

May 19, 2011

Utility Tunnelling - Starting and target shafts

This presentation is part of the series of presentations "Utility Tunnelling" and deals with the building of starting and target shafts and the design of exit and entry openings.

Feb 10, 2020

Utility Tunnelling - Geotechnical investigations

Introduction

Geotechnology

To the field of Geotechnology belong, amongst others, the following scientific disciplines:

Geological engineering: Science that incorporates the application and evalutation of geological know-how and consolidated findings when dealing with construction works.

Soil and rock mechanics (geomechanics): Science with the objectives…
- To investigate the subsoil,
- To describe and classify the soil,
- To determine the strength and deformation behaviour of …

Sep 22, 2008

Utility Tunnelling - Geotechnical investigations

Introduction

Jan 01, 1900

Content

Today, supply and discharge lines are still predominantly installed by using the open-cut method: a trench is dug, the lines are installed. Under the protection of an embankment or sheeting and the trench is filled afterwards.

In the face of the numerous disadvantages as well as the citizens' growing environmental consciousness in the future it is urgently necessary to take trenchless technology into account much stronger than until today as an alternative …

Aug 15, 2006

Microtunnelling with auger spoil removal - description

Method of operation and sequence

Microtunnelling with auger spoil removal is characterized by the jacking of pipes in soils with simultaneous excavation of the working face using a cutting head and by continuous removal of the spoil with a spiral conveyor or auger, which is guided inside a spiral conveyor guide pipe, towards the starting shaft.

(Image: Technical components for microtunnelling with auger spoil removal in single phase jacking) (Image: …

Aug 04, 2008

Microtunnelling with auger spoil removal - starting shaft

(Image: Equipment, possible arrangement of the components on the construction site and space requirement (approximately L × W = 22.0 × 4.0 m) in microtunnelling with auger spoil removal - top view (on the model of the jacking of pipes DN/ID 600, pipe length 2.0 m))

The dimensions of the starting shaft are determined by the type of machine and the selected size and length of the jacking pipes. Today, use is made mostly of prefabricated reinforced concrete …

Aug 04, 2008

Removal of the spoil

The spoil loosened at the working face with the aid of the cutting head is transported to the starting shaft by the spiral conveyor and is there collected in a spoil bucket. Using lifting tackle, this is lifted to the surface when full at determined intervals, usually after jacking a pipe piece. The pressure at the working face is mechanically balanced by the cutting head or by means of the soil plug that is formed in the front section of the conveyor …

Aug 15, 2006

Drive variants of the cutting head

(Image: Microtunnelling with auger spoil removal in single phase jacking - Variant: driving the cutting head with the spiral conveyor)

(Image: Microtunnelling with auger spoil removal in single phase jacking - Variant: direct driving of the cutting head and separately driven spiral conveyor)

Drive variants of the cutting head:

Variant A: driving the cutting head with the spiral conveyor
The spiral conveyors (auger rods) and cutting head are fixed together …

Aug 04, 2008

Design of the cutting head

Driving the cutting head with the spiral conveyor

The maximum capacity of the auger regarding particle size (usually < 1/3 of the auger's diameter) must not be exceeded.

This is achieved by limiting the entry opening at the transition of the cutting head to the spiral conveyor guide pipe at the periphery of the scraper cutting head or by means of correspondingly dimensioned soil entry openings in the scraper cutting head itself.

Direct driving of …

Aug 04, 2008

Design of the cutting head - examples

(Image: Example of cutting head driven with the spiral conveyor [Becke96]) (Image: Example of cutting head driven with the spiral conveyor [FI-Herreb]) (Image: Example of cutting head driven with the spiral conveyor [FI-Wirthb]) (Image: Example of cutting head driven with the spiral conveyor [FI-Schrö])

Aug 04, 2008

Drive of the cutting head with the spiral conveyor - evaluation

(Image: Pros and cons)

Advantage of driving the cutting head with the spiral conveyor:

smaller nominal pipe sizes possible

(Image: Pros and cons)

Disadvantages of driving the cutting head with the spiral conveyor:

stones or boulders inside the soil cannot be destroyed
control of the supporting pressure at the work face is hard to adapt to the subsoil situation since no separate control of the excavation and removal volumes is possible

Aug 04, 2008

Direct drive of the cutting head - evaluation

(Image: Pros and cons)

In contrast to driving the cutting head with the spiral conveyor, the direct drive of the cutting head has the following advantages:

More sensitive adaptation and control of the supporting pressure at the working face due to separate regulation of the excavation and conveying quantities
By combining the cutting head with a crusher, the range of applications is extended to soils with cobble inclusions
Increase of jacking …

Aug 04, 2008

Application in groundwater-bearing soil

Possible measures for the application in groundwater-bearing soil:

Combination of a rotary vane lock at the end of the spiral conveyor or a rotating feed apparatus with a longitudinally displaceable cutting head
Arrangement of a ring-shaped inflatable elastomeric sealing system ("compressed air valve") in the spiral conveyor guide pipe
Combination of a compressed air valve in the spiral conveyor guide pipe with a longitudinally displaceable cutting …

Aug 04, 2008