Rapid changes in geotechnical and geological ground conditions lead to significant ground motion variability. This condition mainly occurs at the so-called basin edges, where there is an abrupt transition between soft highly compressible soils and stiffer materials. This problem becomes more relevant in areas where ground subsidence drastically changes the dynamic response of high plasticity clay deposits, such as those found in Mexico City, due to fundamental site period evolution with time. This paper presents site response analyses at an abrupt transition area in the southeast Mexico City region, along the edges of the Xochimilco-Chalco lakes. Considerable damage associated with three-dimensional wave propagation effects was observed in this zone during the September 2017 Puebla-Mexico earthquake. A series of three-dimensional finite difference numerical models of the basin edge were developed to evaluate ground motion variability, considering topographic effects and soil non-linearities. Good agreement between the computed response and the observed damage during the 2017 Puebla-Mexico earthquake reconnaissance was found. In addition, several normal and subduction events with a return period of 250 years were considered to evaluate the effect that frequency content, and strong ground motion duration have on the soil response variability. From the results gathered here, it was established the relevance of accounting for three-dimensional wave propagation fields to assess site effects at basin-edge zones properly and to be able to implement proper risk mitigation measurements at these zones.

Seismic soil-structure interaction performance evaluations of projects located in deep soft clay deposits warrant special attention, particularly when designing strategic infrastructure that must remain operating after a major earthquake. The development of numerical analytical platforms in recent decades, along with faster computing tools, have made possible to include in the state of practice quite sophisticated solution techniques aimed at better representing the physics of the problem at hand. This paper presents the application of a 3-D finite difference model for evaluating the static and dynamic response of a 118 by 100 m cellular-raft foundation to be built in soft clay. The raft foundation is a 2.5 m high box-type foundation embedded 1 m and supported by a grid of peripheral and internal walls, 2.5 m long and 0.40 m thick, which integrates a cellular structure. The model is used to obtain first the static behavior exhibited by the foundation for the construction stages, including long term consolidation, and then the design earthquake is considered and the equation of motion is solved in time domain.

The ballast consists of angular particles whose main function is to transmit and distribute train loads to the soil. However, under repeated loads, these particles wear down and break, causing permanent settlement, reducing track stability, and increasing maintenance. Characterizing stresses and deformations under monotonic and cyclic loading is essential to predict short- and long-term performance of railway systems. This numerical study evaluates the behavior of improved ballast materials, considering particle breakage. A hybrid Finite Difference and Discrete Element model was used to simulate the multiscale response of the track system under realistic loading conditions. The model was calibrated using data from laboratory tests conducted by various researchers. The performance of conventional ballast was compared with alternative mixtures, analyzing vertical displacements, stress distribution, safety factor, and particle breakage rates. Results show that the basalt-rubber composite significantly enhances ballast performance by reducing settlements and subgrade stresses while improving resistance to particle breakage. The FDM-DEM coupled approach effectively captures micromechanical interactions and breakage mechanisms, offering valuable insights for optimizing track design based on quantifiable performance criteria. Overall, the findings indicate the hybrid model and breakage–contact criteria approximated system behavior, while alternative ballast compositions improved durability, reduced maintenance, and supported resilient railway solutions.

The construction of tunnels excavated by the conventional method in densely populated urban environments requires an adequate characterization of the loads acting on the primary lining during the excavation process, to ensure that the ground is deformed and stresses around the tunnel are relieved, simultaneously complying with the failure and serviceability limits of international standards while minimizing damage to nearby structures. In this paper, common lining design criteria are revisited, through the numerical simulation of an instrumented tunnel section which is part of a 4.5 km long metro line currently under construction in Mexico City. Key needs for improvement in current design approaches are identified. The tunnel was instrumented with load cells, extensometers, and topographical references for convergences and divergences. A three-dimensional finite difference model of the instrumented section was developed, and the load transfer mechanisms between the excavated soil and the primary lining were analyzed. Then, the numerical simulation of the contribution of the secondary lining in the overall stability for sustained load was established, along with the expected ground settlements, which can significantly affect nearby structures. Results gathered from this research are key for updating lining design criteria for urban tunnels built in stiff brittle soils.