Ground penetrating radar study of a railwat tunnel

We have carried out a GPR study of an old railway tunnel. A high degree of detail having been obtained, we feeI interesting to show apart of the work. Now, the use of GPR for the study of tunnels is common, mainly for ascertaining the conditions of constructive eIements. In old tunnels, these conditions depend mainly on host materials. In our case we have obtained very good resolution in the determination of conditions of both elements. In the study of railway tunnel of La ParadiIIa (Madrid-Á vila Line) had as main ends: - Determination of the damage degree of coating. - Determination of condition of extrados, specialIy thickness, voids, etc. - Determination of host rock conditions, namely weathered and/or altered areas, fractured zones, etc. The exploration was carried out in an area of the tunnel which have convexities and moistures; it was important to know the invisible areas and the origin of such damages. It were carried out 12 longitudinal lines, with 1 m separation, covering the sides and the keystone. We show here two of these lines. The remainder are very simiIar. In order to know the accuracy of GPR studies, several drilling were effected in problematic and normal points. The consistency of its resuIts with the interpretations was very good.