New developments on the interpretation of inclinometer field data

Abstract

One of the instruments that is commonly used to control geotechnical stability problems is the inclinometer since it provides sub-surface horizontal deformation data which allows to estimate the location of a potential failure surface and the evolution of the displacements in that particular location. Recent instability cases studied by LNEC researchers outstand the need to improve the current procedures of inclinometer data interpretation. ln fact these procedures can not quantify how close to failure are the soils located in the potential failure surface. A new procedure is presented to estimate the distribution in depth of the horizontal shear strain, yh, from inclinometer data. Once yi, is known is possible to estimate the correspondent maximum shear strain, y, using the geometry of the failure surface. This new procedure has been used to study the instability of the slopes of a major access highway to Lisbon. The values of y estimated from the new procedure indicate that there was a situation of eminent rupture at the site and that the shear resistance to use in the design should be the residual shear resistance.