Stress-strain behavior of two different soil specimens subjected to cyclic compressive loading are studied herein, the goal being to present a simple dynamic uniaxial mem-modeling approach that aids physical insight and enables system identification. In this paper, mem stands for memory, i.e., hysteresis. Mem-models are hysteresis models transferred from electrical engineering using physical analogies. Connected in series, a mem-dashpot and mem-spring are employed to model inter-cycle strain ratcheting and intra-cycle gradual densification of the two soil specimens. Measured time histories of stress and strain are first decomposed so that the two modeling components, mem-dashpot and mem-spring, can be identified separately. This paper focuses on the mem-dashpot, a nonlinear generalization of a linear viscous damper. A mem-spring model is also devised built on an extended Masing model. Nonlinear dynamic simulations (with inertia) employing the identified mem-dashpot and mem-spring demonstrate how well the identified mem-models reproduce the measured early-time data (first 200 cycles of loading). Choices of state variables inherited from bond graph theory, the root of mem-models, are introduced, while MATLAB time integrators (i.e., ode solvers) are used throughout this study to explore a range of contrasting damper and spring models. Stiff solver and the state event location algorithm are employed to solve the equations of motion involving piecewise-defined restoring forces (when applicable). Computational details and results are relegated to the appendices. This is the first study to use single-degree-of-freedom (SDOF) system dynamic simulations to explore the consistency of mem-models identified from real-world data.

In this paper, a novel numerical simulation approach based on the finite element method for dynamically modeling the excavation process of shield tunneling is proposed, with the shield-ground interactions well captured. This method is capable of mimicking the alternating modes of advancing and stopping of a shield boring machine during underground construction, with the important effects of the cutterhead rotation and slurry support pressure considered. Under the cutting action, the soil at the excavation face would experience irreversible deformation and damage, such that additional support needs to be provided by the cutterhead blades and slurry to maintain stability. The impacts of key construction parameters are examined, including cutterhead rotary speed, advance rate, and slurry support pressure, on shield tunneling operations and ground responses. The numerical model is rigorously validated against physical model experiments. This work provides useful insights into the mechanistic processes in the stratum during shield tunneling, including the spatiotemporal evolution of ground deformation patterns and stress redistributions. The results offer valuable guidance for optimizing shield tunneling operations and enhancing tunneling safety and efficiency.