\n

GeoConSol
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

spacer
nn nn nn
nn
A-Misrepresentations
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
J-Boulders-Microtunneling
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
boulders, tunnel, boring, differing, site, conditions, Tarkoy, GeoConSol

Boulders in Tunnel Boring - Alleged DSC 
---on behalf of owner---

Contractor claimed having encountered unanticipated boulders, one of which is illustrated below:

 

An examination of the anticipated and encountered conditions revealed that the contractor actually encountered a shorter length of tunnel containing boulders than indicated in the geotechnical information and experienced on a previous section of the project as illustrated here:

Furthermore, the contractor actually made better progress when excavating in tunnel sections with boulders as illustrated below.

In fact, most of the delays suffered by the contractor were associated with replacing broken lagging as a result of rib spacing beyond the capacity of the lagging used as show below.  A membrane behind the lagging reduced the skin friction between lagging and soil, thereby placing the TBM's forward thrust force into the lagging, forcing it to act as a beam in compression.

CONTRACTOR WITHDREW CLAIM FOR TUNNEL BOULDERS AND SETTLED FOR ORIGINAL OFFER FOR SHAFT BOULDERS

 

nn
nn