UNITRACC - Underground Infrastructure Training and Competence Center

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Jan 25, 2005

Modules

Mathematical Simulation of Pipe Stresses for Difficult Jackings

Forces during pipe jacking

Hardening of the pressure transfer ring

(Video: Calculation in the direction of the pipe axis: deformation at the pressure transfer ring during pipe jacking)

Aug 23, 2005

Modules

Mathematical Simulation of Pipe Stresses for Difficult Jackings

Forces during pipe jacking

Jan 25, 2005

Modules

Mathematical Simulation of Pipe Stresses for Difficult Jackings

Calculation method

Current structural calculation of jacking pipes

Calculation of the permissible jacking force (statical snap-shot of the pipe joint):

One single loading
Linear run of the stress
Fixed (chosen) value of the bending
No consideration of the hardening of the pressure transfer ring, fixed modulus of elasticity
No consideration of the alignment

(Image: Stress development of a circular cross section in dependence on the proportion z/da [ATVA161])

Jan 25, 2005

Modules

Mathematical Simulation of Pipe Stresses for Difficult Jackings

Calculation method

Outer spalling of the concrete

The presented problem of the hardening of the pressure transfer ring is often the main cause for damages or destructions that occur during jacking process. This is frequently due to spallings at the outer end faces of the pipe, which are often not visible from the inside and remain unnoticed at the final inspection of the construction work.

(Image: Example of a reinforced concrete spalling of exceeding the concrete compressive strength at the pipe …

Jan 25, 2005

Modules

Mathematical Simulation of Pipe Stresses for Difficult Jackings

Calculation method

CoJack

(Image: CoJack - Logo)	Computing and Controlling Pipe-Jacking
The calculation program "CoJack" developed by Prof. Dr.-Ing. Stein & Partner GmbH serves as a practical and powerfull instrument to increase the safety and economic effiency of pipe jackings.

Jan 25, 2005

Modules

Mathematical Simulation of Pipe Stresses for Difficult Jackings

Calculation method

CoJack - important additional features

CoJack takes the following aspects into account:

Non-linear stiffness behaviour of the pressure transfer ring by separation of the elastic and plastic deformation parts.
The loading history of the pressure transfer ring for each observed point of time.
Changes in the stiffness and the geometry of the pressure transfer ring in the course of jacking.
Time development of the longitudinal force.
Time progression of lining.

(Image: Electronic measuring …

Jan 25, 2005

Modules

Mathematical Simulation of Pipe Stresses for Difficult Jackings

Calculation method

Additional characteristics of CoJack

Important additional input of CoJack (input parameters in addition to the calculation methods currently taken into consideration are presented in bold letters):

pipe geometry including tolerances
concrete strength
geometry of the pressure transfer ring
real stress-strain behaviour of the pressure transfer ring
alignment
incorrect steering within the jacking

(Image: Attention!)

Conclusion:
Simulative jacking along the alignment with the required …

Jan 25, 2005

Modules

Mathematical Simulation of Pipe Stresses for Difficult Jackings

Calculation method

CoJack - cross-sectional geometry

The starting point for the mathematical realisation is the listing of the functional description of the cross-sectional geometry.	(Image: Function of cross section with reference to the z-coordinates of the calculation example)
(Image: Formula for calculating the load transfer ring width of the cross section B(z) for a circular cross section)