Seismic risk assessment for oil and gas pipelines - Seismic Risk Analysis and Management of Civil Infrastructure Systems - page 699

25.4 Ground densifi cation using vibro-replacement at a river bank
in Vancouver, British Columbia, Canada, to reduce the risk of
liquefaction-induced lateral ground displacements (Wijewickreme
et al. , 2005).
clearly dependent on geotechnical risks that are to be mitigated, and these
confi gurations essentially fall into one of the following two categories: (i)
in-ground densifi ed barrier(s) aligned perpendicular to the direction of
ground movement to reduce liquefaction induced lateral spreading; and (ii)
densifi cation of wide-area footprints beneath and/or around foundation
footprints to improve bearing capacity and to reduce the impacts from
lateral spreading.
Verifi cation testing for quality control forms a key component in under-
taking ground improvement works. Evaluation of the treated soil type,
method of ground improvement, and site constraints are required in select-
ing the parameters and testing tools to assess the conformance of ground
improvement to specifi ed criteria. In addition, effects from parameters that
affect the soil behavior (e.g., aging and pore pressure dissipation) can have
signifi cant infl uence on the observations from verifi cation testing, and they
should be carefully evaluated in determining the acceptability of a given
ground improvement.
The need to protect adjacent existing pipelines/structures is often a key
consideration during ground improvement. Thus systematic monitoring of
existing facilities during ground improvement is essential. Furthermore,
structural evaluation of the performance of structures based on data from
monitoring as well as modifi cation of ground improvement methodology
and confi gurations to meet the constraints are generally required.