Geotechnical & Tunnel Consultants

A consultant is a universal observer who can look at a problem outside the environment in which the problem came to be, thereby creating a solution that was never possible before.  Fernando Flores

nn nn nn
B-Type 1 or 2?
C-Jacked Pipe Failure
D-Top of Rock
E-PI Litigation Support
F-Geotech Assessment
G-Microtunneling Hard/Soft
H-Machine Failure
I-Boulders-Tunnel Boring
K-Plowing Utilities
L-Rock Socket Overrun
M-Bored Tunnel Inflow
N-Rock Comminution
O-Sub-Std TBM Performance
P-Bored Tunnel-Shear Zone
Q-Disputes Resolution
R-Problem Proj. Completion
S-Bored Tunnel Overbreak
T-Auger Sampling Problems
U-Bored Tunnel Delay
V-Hoe Ram - Failure to Rely
Peter J. Tarkoy
jacked, pipe, jacking, failures, Tarkoy

Pipe Failure 
--- on behalf of pipe manufacturer ---

We were engaged to investigate the cause of jacked pipe failures on behalf of the pipe manufacturer. Our investigation included test results of the pipe material, operational jacking forces, shift records, and critical spatial relationships.

It was found that:

  1. the pipe did not fail at the location of the highest stress at the jacking pit

  2. pipe failures occurred on Mondays

  3. other pipes failed on Tuesdays when Monday was a holiday

  4. failure occurred on multiple occasions where the soil/rock interface crossed the pipe envelope

  5. the concrete strength exceeded specifications and distributed jacking loads

The inevitable conclusion were:

  1. the jacked pipe was not lubricated properly

  2. the soil rock/interface was inadequately excavated & pipe traveled out of alignment over the rock

  3. the pipe continued to be out of alignment setting the stage for future failures

  4. point loads / stress concentrations as a result of out of alignment pipe were responsible for the failures