UNITRACC - Underground Infrastructure Training and Competence Center

Utility Tunnelling - Jacking steering, measurement and monitoring

CoJack - Computing and Controlling Pipe-Jacking Projects

(Image: CoJack - Logo)

CoJack (Computing and Controlling Pipe-Jacking) is a comprehensive instrument for planning, monitoring and quality assurance of jacking projects.

It reduces the risk factor of an overstraining of the pipes during jacking and thus decisively increases the safety and economic efficiency of jacking projects.

CoJack allows for a continuous updating of the structural calculation by means of a correction of the permissible jacking …

Sep 10, 2008

Utility Tunnelling - Jacking steering, measurement and monitoring

CoJack - Particularities

CoJack takes the most important input parameters, which have a great influence on the pipe load and which have been neglected in current calculation methods, into account:

non-linear stiffness behaviour (elastic and plastic deformation proportions) of the pressure transfer ring, which can be determined individually for any jacking project in a lab test
load history of the pressure transfer ring at any point in time of the jacking project
changes …

Sep 10, 2008

Utility Tunnelling - Jacking steering, measurement and monitoring

CoJack - Range of services

(Image: Planning)

Before the construction works (planning):

check of the structural calculations of the jacking pipes
determination of the safety level under the given circumstances (planning data)
optimised dimensioning of the jacking pipes
configuration of the jacking works

(Image: Construction site)

Construction works:

prevention of damages
ensuring of a smooth construction process

(Image: Inspection)

Construction approval:…

Feb 01, 2005

Utility Tunnelling - Jacking steering, measurement and monitoring

CoJack - Sequence diagramm of simulation

(Image: CoJack - sequence diagramm of simulation)

Sep 10, 2008

Utility Tunnelling - Jacking steering, measurement and monitoring

CoJack - Prerequisites

(Image: Attention!)

In the monitoring of the running jacking works, CoJack requires precise and up-to-date measuring values from the construction site.

(Image: Procedure of the online-simulation of pipe jacking - NEU)

(Table: Areas of application for a monitoring / supervision of a pipe jacking project)

For this purpose a Gap Measurement System (GMS) has been developed especially according to CoJack's requirements, whose sensors continuously and automatically …

Sep 10, 2008

Utility Tunnelling - Jacking steering, measurement and monitoring

CoJack - Gap Measurement System

The measurement system works completely independent from the installed steering guidance system and can thus be installed at any construction site directly after the start of the jacking works.

Usually the sensors consist of:

distance meters to measure the joint gap
pressure sensors to measure the pressure at the jacking station
distance meters to measure the extension of the jacking station
measuring wheel to determine the covered jacking distance

Sep 10, 2008

Utility Tunnelling - Jacking steering, measurement and monitoring

CoJack - Transmission of the measuring data

All measurement data are transmitted to the system computer via data cable and Controller Unit and are displayed there. The system creates a data base, in which the single sensor values and/or the openings of the recorded gaps and the present jacking forces generated by the jacking station and interjacks are consistently documented including the corresponding extensions.

Via an on-line connection CoJack is supplied with these up-to-date measuring …

Sep 10, 2008

Utility Tunnelling - Jacking steering, measurement and monitoring

CoJack - Gap Measurement System (Process)

The functional principle and application of CoJack is shown in the diagram (right).

The interaction with the construction site is made possible by signal light concept. The 'signal light' represents a practical, simplified illustration of the results. Basically, jacking measures simulated via CoJack can be categorised in 4 case groups according to Table below.

(Image: Functional principle and application of CoJack)

(Table: Case groups of the simulation …

Sep 10, 2008

Utility Tunnelling - Jacking steering, measurement and monitoring

CoJack - Advantages

(Image: Pros and cons)

CoJack allows for

greater jacking distances,
tighter curve radii and
higher jacking speeds.

This leads to immense savings, e.g. by:

saving of jacking shafts
saving of otherwise geometrically required shafts and
reduction of the construction time.

Sep 09, 2008

Utility Tunnelling - Jacking steering, measurement and monitoring

CoJack

Jan 25, 2005

Utility Tunnelling - Pipe jacking - Part 2

Errors and consequences of damage

Calculation of jacking pipes - relevance

(Image: Attention!)

The jacking pipe is the weakest link in the jacking chain.

(Image: Spallings on a jacking pipe)

In any case of technical problems or failures during jacking, the risk of damaging the pipes by overload is very high due to incorrect steering movements or the introduction of increasing jacking forces.

Jan 25, 2005

Utility Tunnelling - Pipe jacking - Part 2

Errors and consequences of damage

Calculation of jacking pipes

The calculation and continuous monitoring of the jacking process is an important tool for the prevention of damages in order to secure:

accurately planning including adequate structure design
current quality control
final quality control

(Image: Crack formation as a consequence of splitting tensile stresses due to unbalanced load introduction into the pipe faces)

Aug 05, 2008

Utility Tunnelling: Pipe Jacking - Part 1

Lubrication of the annular space

Definition overcut

Overcut:
The annular gap around the pipe deliberately created by using a cutting head or shield of a greater dimension than the outside dimension of the pipe [DINEN12889:2000].

Overcut:
Half of the difference resulting from borehole diameter and outer pipe diameter (ideally an even annular gap around the pipeline).

(Image: Annular space fluid supported)

Jun 20, 2006

Utility Tunnelling - Introduction

Introduction

Infrastructures in the urban underground

(Image: Infrastructures in the urban underground [FI-Steina])

Jun 21, 2006

Utility Tunnelling - Introduction

Introduction

Piping documentation

(Image: Documentation)

Piping documentation conforming to reality is usually not available, even the owners of the pipe network often have no accurate knowledge of the position of their pipelines.

This means that one cannot assume the existence of a distribution according to the standards in the underground construction space.

(Image: Underground pipelines in New York about 1916 [Boegl69])

(Image: Unprofessional installed cables and pipelines […

Jul 31, 2008

Utility Tunnelling - Introduction

Introduction

Possibilities for the new construction of pipelines

Open-cut method of construction

(Image: Open cut method)

(Image: Sheeted trench for the installation by open-cut method of construction)

(Image: Urban installation of pipelines)

Trenchless method of construction

(Image: Geschlossene Bauweise)

(Image: Accessible city centre area in spite of construction works)

Jan 01, 1900

Mathematical Simulation of Pipe Stresses for Difficult Jackings

Content

CoJack is a new efficient method for the static calculation of jacking pipes for loads in the direction of the pipe axis. By means of algorithms especially developed by company Stein & Partner, it has for the first time been possible to accurately determine the constantly varying pipe stress during jacking processes. The rough simplifications of the currently used calculation methods are eliminated in order to optimise the safety and economic efficiency …

Jan 25, 2005

Mathematical Simulation of Pipe Stresses for Difficult Jackings

Pipe jacking technique

Calculation of jacking pipes - relevance

(Image: Attention!)

The jacking pipe is the weakest link in the jacking chain.

(Image: Spallings on a jacking pipe)

Jan 25, 2005

Mathematical Simulation of Pipe Stresses for Difficult Jackings

Pipe jacking technique

Calculation of jacking pipes

The calculation and continuous monitoring of the jacking process is an important tool for the prevention of damages in order to secure:

accurately planning including adequate structure design
current quality control
final quality control

(Image: Crack formation as a consequence of splitting tensile stresses due to unbalanced load introduction into the pipe faces)

Jan 25, 2005

Mathematical Simulation of Pipe Stresses for Difficult Jackings

Jacking resistances - composition

The jacking resistances consist of:

Jacking resistance due to point resistance at the working face with and without the influence of groundwater (loses importance with growing jacking length).
Resistance due to friction between the outer surface and the subsoil (skin friction).
Additional, radially directed guiding forces between the pipe and the subsoil due to curved jacking and steering errors.

(Image: Penetration resistance and jacking force)

Jan 25, 2005

Mathematical Simulation of Pipe Stresses for Difficult Jackings

Jacking resistances - skin friction

Skin friction is determined by:

the radial stress of the pipe due to earth pressure
the coefficient of friction

The skin friction resistance, which is usually decisive for the dimensioning of the jacking station and the pipes, can essentially be influenced by the overcut and the filling of the overcut with a lubricant- and support medium.

(Image: T.B.K. system [FI-TBKa] - Injection medium (Polymer drilling fluid consisting of polymer and water))

Jan 25, 2005

Mathematical Simulation of Pipe Stresses for Difficult Jackings

Jacking resistances - additional, radially directed guiding forces

Curved jackings and steering errors frequently induce additional, radially directed guiding forces between the pipe and the subsoil. These forces increase the frictional resistance.

Since this resistance is dependent on the longitudinal force in the pipe string, it increase in the course of the jacking.

The effect of repeated steering errors is particularly disadvantageous, because the single resistances do not sum up, but lead to an disproportionate …

Jan 25, 2005

Mathematical Simulation of Pipe Stresses for Difficult Jackings

Jacking resistances

(Video: Operating forces during pipe jacking)

Jan 25, 2005

Mathematical Simulation of Pipe Stresses for Difficult Jackings

Required jacking force

(Video: Arrangement and development of the forces of intermediate jacking stations during pipe jacking)

Jan 25, 2005

Mathematical Simulation of Pipe Stresses for Difficult Jackings