Abstract. Quick-clay landslides are common geohazards in Nordic countries
and Canada. The presence of potential quick clays is confirmed using
geotechnical investigations, but near-surface geophysical methods, such as
seismic and resistivity surveys, can also help identify coarse-grained
materials associated with the development of quick clays. We present the
results of reflection seismic investigations on land and in part of the
Göta River in Sweden, along which many quick-clay landslide scars exist.
This is the first time that such a large-scale reflection seismic
investigation has been carried out to study the subsurface structures
associated with quick-clay landslides. The results also show a reasonable
correlation with radio magnetotelluric and travel-time tomography models of
the subsurface. Other ground geophysical data, such as high magnetic values,
suggest a positive correlation with an increased thickness of the
coarse-grained layer and shallower depths to the top of the bedrock and the top of
the coarse-grained layer. The morphology of the river bottom and riverbanks,
e.g. subaquatic landslide deposits, is shown by side-scan sonar and
bathymetric data. Undulating bedrock, covered by subhorizontal sedimentary
glacial and postglacial deposits, is clearly revealed. An extensive
coarse-grained layer (P-wave velocity mostly between 1500 and 2500 m s−1 and
resistivity from approximately 80 to 100 Ωm) exists within the
sediments and is interpreted and modelled in a regional context. Several
fracture zones are identified within the bedrock. Hydrological modelling of
the coarse-grained layer confirms its potential for transporting fresh water
infiltrated in fractures and nearby outcrops located in the central part of
the study area. The modelled groundwater flow in this layer promotes
the leaching of marine salts from the overlying clays by seasonal inflow–outflow
cycles and/or diffusion, which contributes to the formation of potential
quick clays.
Settlements of spread footing foundations on quick clay stabilized with lime and cement
