In Chile, since the beginning of the 20'h century, about 40 cases of mechanical instability of the tailing dams have been reported mainly due to liquefaction, slipping of banks or settlement. In order to solve this problem, a scientific and technological cooperation has been established in 2001 between the geotechnical of groups at the Catholic University of Valparaiso (Chile) and Blaise Pascal University Clermont-Ferrand (France) whit the support of two companies, Sol-Solution in France and GeotecniaAmbiental in Chile. This article presents the main results that have allowed to propose a methodology for control and diagnosing of tailing dams and its application in the medium mining sector. It is based on in-situ determination of geomechanical parameters (internal friction angle and density index) using the Panda lightweigh penetrometer in order to characterize the constituent materials, the variability of these materials and their implementation in the works. Finally, this methodology allows taking into account this variability in the study of stability and the risk of liquefaction of these structures in a probabilistic approach.