  Retaining walls are often built to prevent excessive lateral movements of the
ground surrounding an excavation site. During an excavation, failure of
retaining walls could cause catastrophic accidents and hence their lateral
deformations are monitored regularly. Laser scanning can rapidly acquire the
spatial data of a relatively large area at fine spatial resolutions, which is
ideal for monitoring retaining walls' deformations. This paper attempts to
apply laser scanning to measurements of the lateral deformations of a soil
mixing retaining wall at an ongoing excavation site. Reference measurements by
total station and inclinometer were also conducted to verify those from the
laser scanning. The deformations derived using laser scanning data were
consistent with the reference measurements at the top part of the retaining
wall (i.e., mainly the ring beam of the wall). This research also shows that
the multi-scale-model-to-model method was the most accurate deformation
estimation method on the research data.
