UNITRACC - Underground Infrastructure Training and Competence Center

Mathematical Simulation of Pipe Stresses for Difficult Jackings

CoJack

(Image: Presentation of a pipe jacking with an intermediate jacking station)

Jan 25, 2005

Mathematical Simulation of Pipe Stresses for Difficult Jackings

In this method, jacking pipes are jacked by pressing-in through the subsoil from a starting shaft to a target shaft with the aid of a jacking station as well as intermediate jacking stations.
Jacking in a straight or curved line path is made possible by means of a steerable shield machine positioned at the head of the first pipe. The spoil excavated at the working face is conveyed to the surface through the jacked pipe string.

(Image: View into …

Jan 25, 2005

Mathematical Simulation of Pipe Stresses for Difficult Jackings

Pipe jacking - technical components

(Image: Attention!)

With reference to the variant used to support the workface or to convey the excavated soil the technical components vary in pipe jacking.

(Image: Schematic presentation of a pipe jacking)

Jan 25, 2005

Mathematical Simulation of Pipe Stresses for Difficult Jackings

Advantages of trenchless technology

Advantages of trenchless technology compared to the open cut method:

Preventing break-up and replacement of road surface
Prevention of soil excavation masses
Minimizing groundwater retention measures
Little impairment to traffic flow especially in inner urban areas
Only short-term noise and emission pollution while excavating the starting and target shafts

(Image: Disadvantages of the open cut method for installing drains and sewers (Part 1) [GSTT])

Jan 25, 2005

Mathematical Simulation of Pipe Stresses for Difficult Jackings

Functions of the shield machine

The duties of the shield machine in pipe jacking are as follows [Scher77a] :

To protect the personnel,
To create the necessary cavity so that the following pipe string can be pressed in with a minimum degree of soil deformation and with the lowest possible skin friction,
To protect the cavity until the jacking pipes can finally carry all the loads and forces,
To secure the working face against collapsing soil and rock as well as groundwater, and

Jan 25, 2005

Mathematical Simulation of Pipe Stresses for Difficult Jackings

Shield machine types - overview

(Image: Overview of shield machine types)

Jan 25, 2005

Mathematical Simulation of Pipe Stresses for Difficult Jackings

Damages in pipe jacking

In jacking processes, extensive and irreparable damages are frequently observed, which is due to irregularities of the subsoil.

Although extensive subsoil investigations can reduce the subsoil risk, failures and damages cannot completely be excluded.

(Image: Attention!)

These are the consequences of damages during pipe jacking:

Insufficient quality of the construction execution
Delay
High costs
Environmental impacts

Jan 25, 2005

Mathematical Simulation of Pipe Stresses for Difficult Jackings

Damages in pipe jacking - statistics

(Image: Distribution of damages in pipe jacking in Germany (source: IFB, Hanover 1993))

Aug 23, 2005

Mathematical Simulation of Pipe Stresses for Difficult Jackings

Pipe jacking technique

Mar 07, 2014

Course

BE-21 Utility Tunnelling

This course includes tutorial services and a final examination.

The installation of supply and disposal lines is still mostly performed using the open cut method consisting of digging a trench, laying the pipe under the protection of shoring, and subsequently backfilling the trench. Given the many disadvantages associated with this method along with the growing environmental awareness of the population, it is imperative that trenchless technologies be taken more strongly into account in the planning and construction of pipelines and utility networks.

The learning module "Utility tunnelling" is divided into seven lessons, each focusing on a specific topic. The contents of the individual lessons are complemented with a link to more detailed literature. This literature is not relevant to the exam, but serves as a reference for a more in depth look.
The module "Utility Tunnelling" ends with a final examination, which references all of the modules content.

In order to complete the course successfully, and stress-free within four weeks, we recommend following the following agenda which distributes the different modules evenly over the entire period:

1st week: Module: Introduction, Fundamentals and geotechnical investigations, Pipe jacking (Part 1)
2nd week: Module: Pipe jacking (Part 2), Microtunnelling
3rd week: Module: Jacking pipes, Jacking steering
4th week: Module: Starting and target shafts, Final exam
This schedule is only a recommendation, as it is of course up to you when and how you work through the curriculum.

Nov 24, 2004

Technical Books

Rehabilitation and Maintenance of Drains and Sewers

Replacement by the Trenchless Method

Pipe Jacking (Manned Techniques)

(Image: Microtunnel construction - View of the start shaft with main jacking station and reinforced concrete jacking pipe [FI-FBS])

Hydraulic pipe jacking (see ATV-A 125E or DVGW-W 304 [ATVA125:1996]) [Stein85a] [Conra84b] [Hornu89] [Scher77b] [Stein85e] has been available since the turn of the 20th Century as an alternative to the gallery techniques (heading) and the shield tunnelling with segment lining. This method for the case under consideration …

May 18, 2020

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 …

May 18, 2020

(Image: Simple hand shield - working face with natural support)

Hand shields are non-mechanised open shield machines in which the soil at the working face is loosened by hand using auxiliary tools (pickaxe, spades, shovels or pneumatic hammer). The removal of the spoil is carried out with the aid of conveyor belts, transport carts or tracked conveying buckets (dump trucks).

Examples:

(Image: Hand shield (external diameter 4672) with working …

May 18, 2020

Shield machines with partial excavation by hand - classification

(Table: Classification of hand shields according to the type of working face support)

May 18, 2020

SM-T1 - working face with natural support

(Image: Attention!)

Natural support of the working face is always applicable when the existing subsoil is free of groundwater and the working face is a priori stable (working face without support) or is sufficiently supported by a self-forming earth wedge with a natural slope angle.

(Image: Simple hand shield - working face with natural support) (Image: Handshield - working face with natural support)

May 18, 2020

SM-T2 - working face with partial support

(Image: Attention!)With partial support, the surface of the working face is divided into sections and is either supported by means of natural partial support on bench plates (bench (plate) or platform shields) and/or by means of mechanical partial support using breast plates.

(Image: Hand shield with breast plates - working face with mechanical partial support) (Image: Hand shield with benches (Bench shield) - working face with natural partial support) (…

May 18, 2020

Shield machines with partial excavation by hand - area of application

(Image: Attention!)

Shield machines with partial excavation by hand are predominantly used for:

short jacking distances under 50 m
crossings of traffic ways
jacking of an extraordinary cross-section
groundwater-free soil or rock

May 18, 2020

Area of application for soil classes according to DIN 18319

SM-T1 - areas of application:

stable, cohesive soil, i.e. firm-stiff and very stiff cohesive soil (soil class LBM 2 and 3 and/or LBO 2 and 3 according to DIN 18319) with a compressive strength of approx. 1.0 N/mm²
Rock with uniaxial compressive strength ≥ 5 N/mm² (classes FD 2 to 4 and/or FZ 2 to 4)

SM-T2 - areas of application:

loose to densely compacted non-cohesive soil (classes LNE 1 to 3 and/or LNW 1 to 3) with a particle size concentration < …

May 18, 2020

Shield machines with partial excavation by hand

May 18, 2020

(Image: Shield with fixed intalled excavation machine - working face with natural support (SM-T1))

The shield machines with mechanical partial excavation correspond in concept to the design of the hand shield. They feature a mechanized open (SM-T1 or SM-T2) or closed (SM-T3 or SM-T4) shield with a fixed installed excavator for partial excavation of the soil or rock at the working face.

Examples:

(Image: Principles of support for open shield …

May 18, 2020

Shield machines with mechanically partial excavation - classification

(Table: Classification of shield machines with mechanically partial excavation according to their type of work face support )

May 18, 2020

SM-T3 - working face supported by compressed air

Shield machines with compressed air support (SM-T3) are closed shields based on shield types SM-T1 and SM-T2 in which the working face is pressurized with the flow off compressed air, e.g. "air with a positive pressure of more than 0.1 bar (10 kPa, 1.5 psi) above atmospheric" [ [DINEN12110:2014]] in order that the working chamber (defined in EN 12110 [ [DINEN12110:2014]] as "space in which work is carried out in compressed air") can be kept free …

May 18, 2020

Defintion of compressed air support according to DIN EN 12110

Working chamber:
Space in which work in compressed air is carried out.
[ [DINEN12110:2014]]

Air lock:
Pressure vessel with one or more chambers with access doors, which can be sealed and pressurized with compressed air.
[ [DINEN12110:2014]]

Material lock:
Air lock through which only material or equipment goes into or out of the working chamber.
[ [DINEN12110:2014]]

Personnel lock:
Air lock through which only persons go into or out of the working chamber.

May 18, 2020

Working face supported by compressed air - air locks

(Image: Attention!)

When pipe jacking under air pressure, the working chamber e.g. the region from the working face to the air lock must be made airtight by means of a pressure bulkhead ("equipment which separates spaces with different pressure levels" [ [DINEN12110:2014]]) from the ambient atmosphere.

Types of air locks:

material lock
personnel lock
combined lock

(Image: Longitudinal section of an air lock system in the trailing shield segment with …

May 18, 2020