MicroTunneling Differing Site Conditions
---on behalf of several contractors---
On a number of projects, micro-tunneling machines embarked into material having
extremes of soft hard material interfaces. Line & grade were
impossible to maintain. There are solutions to this problem, however, each works
within a very limited range of conditions.
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1. A microtunnelling alignment was underneath a swamp, however, the soil sampling was performed
by the geotechnical engineer from a causeway over the swamp. The soil properties under the
causeway were far better because the material had been consolidated.
The microtunneling could not maintain line & grade without considerable expense for ground treatment.
CONTRACTOR PREVAILED
2. On Waikiki Beach a micro-tunneling excavation ran into part of the original wood bridge when crossing a buried valley near Waikiki Beach)
The archive files of the area revealed that here had been a wooden bridge located at the site of the obstruction of the pipe jacking operation.
OUTCOME
After long negotiations, the city of Honolulu settled with the contracter based
on our analyses showing the obstruction and hard/soft layers representing tidal
and coral deposits. |
GeoConSol
