Slow landslides of any type and dimensions show variable displacements with periods of acceleration following episodes of very limited movements. In order to know the detailed behaviour of the considered unstable masses in time it is thus necessary to obtain a continuous recording of displacements. Such an information is essential to identify the possible causes of critical phases or to design warning systems.
Slow landslides of any type and dimensions show variable displacements with periods of acceleration following episodes of very limited movements. In order to know the detailed behaviour of the considered unstable masses in time it is thus necessary to obtain a continuous recording of displacements. Such an information is essential to identify the possible causes of critical phases or to design warning systems.
More than l0 years ago the Soil Mechanics Laboratory of EPFL developped mechanical devices lor the continuous measurement of surface displacements of landslides by invar wire extensometers [ENGEL, 1986]. Different types of recording systems were installed at several landslides showing sometimes interesting results. However these systems were not quite fit for the recording of large distances exceeding 200 mand the effects of climatic conditions (wind, rime) could seriously affect the reliability of the recorded data.
A new electrooptical system has therefore been developped by our laboratory including a cheap manual distance measurement device (distancemeter) recently produced by Leica, called Disto, emitting a laser ray reflected by a smooth surface or a prism. This device could be adapted to the specific needs of an open air continuous measurement as it was recently provided with a RS 232 output allowing its driving by computer. The first results obtained at La Lécherette Landslide are presented and commented in order to appreciate the interest of such a device.
Slow landslides of any …
AUTORI: Bonnard C., Steinnmann G. RIG ANNO: 1996 NUMERO: 2 Numero di pagina: 8
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