Tunnel Performance under Extreme Environmental Effects

Environmental effects in strategic underground infrastructure, such as extreme water extraction, extreme floods, material deterioration due to water infiltration and ground movement under sustained and seismic loading, can significantly affect its short, medium, and long-term performance. Furthermore, these effects are critical in densely populated cities, where the overall safety of a particular structure can be jeopardized if those effects are ignored, and poor geotechnical conditions prevail, such as in Mexico City, where high plasticity and highly compressible clay is found. This paper presents a novel methodology based on a coupled field monitoring and numerical approach to assess the performance of strategic underground infrastructure under environmental effects. The method allows to establish, from a surrogate model derived from the analysis of several scenarios, an optimum range for the expected performance, establishing a lower and upper-efficiency curve as a function of the environmental parameters measured. The method is introduced through a case study corresponding to a 9.1 km long tunnel. Through the analysis of the results obtained, it was possible to evaluate the short to long-term behavior of a tunnel and eventually propose mitigation measures to enhance its expected performance.