Forensic analysis of the failure of the foundations of a tunnel built to channel the course of a river

Abstract

This paper presents the results of a forensic analysis of a tunnel above which an embankment was built that served as a roadbed. The joint tunnel–embankment structure is located on the outskirts of the town of Piedrafita in northwestern Spain. The tunnel channels the course of the River Vilela in its crossing of the aforementioned road. This article presents a detailed report of the problem, including the damage caused to the structure of the tunnel and the embankment, and it presents the measurements taken and the determination of the origin of the problem. For this determination, a numerical simulation of the joint tunnel–embankment–ground structure was conducted on the basis of the data obtained from tests carried out both in situ and in the laboratory. The study was complemented by an analysis performed using classical methods that confirmed that the movements detected in the overall structure were caused by the collapse of the foundations. The uniqueness of the study presented in this paper lies in the combination of very simple analytical calculations to evaluate the stresses transmitted by the foundations to the ground with a numerical model that enables us to evaluate the stress and deformational state of the study area in a highly detailed way.