Aplicación de técnicas de Geo-Radar para el estudio del tapón de jet-grouting inyectado en los túneles del metro

Abstract

Several kilometers o f tunnel have been excavated to extend a metropolitan underground system. In some places, where the subsurface is mainly composed by gravel and sands, water can easly penetrate causing problems to the tunnel and the stations. In order to avoid such problems, a jet-grouting injection was carried out. To check the continuity of the jet-grouting a Ground Penetrating Radar analysis was applied. The radar used is a SIR 10 of Geophysical Survey Systems Inc., with a center frecuency antenna of 100 Mz, prepared for urban jobs. A good determination of the variantion of the thickness of the jet-grouting layer was obtained, although several difficulties, specially the irregular topography, were to be solved. Three boreholes to determine the quality and thickness of the jet-grouting in three different places provided the right calibration of the involved radargrams. During the processing of the data, several filters had to be applied to discriminate the radar signals from noise, coming mainly from the electrical system of the tunnel