Deformations

Monitoring ground and structural deformation is crucial for the serviceability of any structure in an alpine environment. The observational method approach and adaptation strategies rely on these measurements. Depending on the structure and situation, different deformation techniques can be used. Ground based surveying is the easiest way to measure surface deformations. Automatic total stations can be used for continuous monitoring in remote areas. Additional surface monitoring methods include photogrammetry, InSAR or LiDAR technologies (Kaab, 2008; Metternicht et al., 2005; Roer et al., 2005; Strozzi et al., 2004).

Borehole deformation measurements help to understand complex deformation profiles (e.g. Arenson et al., 2002; Haeberli et al., 1998). Horizontal deformations can be measured using slope inclinometers and vertical deformations with extensometers. Borehole inclinometers should cover the whole thickness of the permafrost layer and be fixed into non-moving ground, e.g. bedrock. In addition, the top of the borehole should be included into the terrestrial survey as a control point and to identify movements if the bottom is not fixed.

Time domain reflectometry (TDR) can also be used to measure ground deformations with depth (O'Connor and Dowding, 1999). TDR cables should only be used if distinct shear zones are present (Arenson, 2002). In contrast to inclinometers and extensometers, TDR deformation measurements have a much finer resolution in terms of the depth of a particular shear zone, however, the actual direction and extension of the deformation can only be estimated.

Various additional deformation monitoring instruments exist that may be suitable for particular projects, including tiltmeters, crackmeters, strain gauges, or pressure cells.

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