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

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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
very, hard, rock, comminution, cominution, bored, tunnel, differing, site, condition

DSC-Difficult Rock Comminution
---on behalf of contractor---

Very difficult boring is measured in terms of the Field Penetration Index (kg/mm of penetration / revolution).
The soft mica schists had released the mountain building stresses inherent in the uplift of the Andes. The harder and more brittle granitic rocks, especially the quartz rich granites (indicated by the red lines), retained the in-situ stresses. These stresses acted to make rock comminution more difficult, thereby slowing penetration and increasing tool wear exponentially.
The FPI is illustrated below.

Tool wear is consistent with difficult rock comminution.