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.

The compaction success of vibratory roller compaction can be assessed by systems for continuous compaction control (CCC) or intelligent compaction (IC) which calculate soil stiffness-proportional quantities based on measurements of the motion behavior of the vibrating drum. However, state-of-the-art intelligent compaction meter values (ICMV) do not only depend on the stiffness of the soil but are also strongly influenced by machine and process parameters. In this paper, the methodology for determining an advanced ICMV is presented, in which the mechanical properties of the soil, the process parameters and geometric relationships in the contact area between the drum and the soil are directly included in the calculation. The methodology is explained on the example of measurement data from a compaction test conducted on sandy gravel with a heavy single-drum roller. The results of the novel ICMV are compared with those of the most widely used IC systems.

This paper investigates the liquefaction hazard in the Port Area of Pulau Baai, Bengkulu City, during the large subduction earthquake of 2007. The study was conducted systematically, commencing with a site investigation that included shear wave velocity measurements. Spectral matching and ground motion predictions, based on a relevant attenuation model, were performed to derive representative ground motions for the study sites. Ground response analysis was carried out to examine soil behaviour under seismic loading. Non-linear finite element analysis was utilised to assess dynamic soil characteristics such as excess pore water pressure, shear stress-strain response and stress paths. Additionally, an empirical evaluation was conducted to assess the liquefaction potential. The results indicate that liquefaction at shallow depths could occur, particularly in the first two sand layers. They also suggest that potential seismic damage could range from VII to IX on the Modified Mercalli Intensity (MMI) scale. Both numerical and empirical analyses demonstrated consistent trends and alignment. The comparison of excess pore pressure ratios and safety factors aligns with findings from previous studies. These results underscore the importance of implementing seismic hazard mitigation measures for the study area.

This study evaluates the vertical stress transmission through a sand-tire mixture layer under impact, focusing on this innovative blended material that can impact underground structures such as tunnels or pipelines. By conducting consolidated undrained triaxial tests, the friction angle (phi) of the sand-tire mixture was determined, ranging from 29 degrees for pure tire to 41 degrees for pure sand. The vertical stress factor (alpha), representing the ratio of response load to applied load, was found to decrease significantly with increased tire content, with a reduction of up to 50% for mixtures containing 20% tire. Additionally, the vertical stress response decreased from 35 kPa for pure sand to as low as 15 kPa for mixtures with a high tire content under a consistent applied load of 65 kPa. This study not only presents a methodological advancement in analyzing sand-tire mixtures under dynamic loads but also suggests a sustainable approach to utilizing waste tire material in civil engineering projects, thereby contributing to environmental conservation and improved material performance in geotechnical applications.

The distribution of total soil nitrogen (TSN) and total soil phosphorus (TSP) plays a pivotal role in shaping soil quality, fertility, agricultural practices, and environmental balance, especially in ecologically sensitive regions like the North-Western Himalayas (NWH). The primary objectives of this study were to contribute to clarify the impact and the rationale of various land uses on the spatial variation of TSN and TSP in the corresponding soils. This study aimed to explore the relation of TSN and TSP distribution in NWH soils with various factors like landscape physiography and soil physical and chemical properties using random sampling and geostatistical analyses. Employing random sampling, 300 soil surface samples (at a depth of 0-20 cm) were collected across various 500 m x 500 m grids from agriculture, horticulture, forest and fallow lands in the NWH region. The spatial land heterogeneity of TSN and TSP were systematically analyzed using standard statistical and geostatistical approaches (Gaussian, spherical, exponential, and linear). Results revealed a decreasing order of TSN and TSP levels i.e., horticulture (0.410 and 0.723 mg/kg) > agriculture (0.314 and 0.597 mg/kg) > forest (0.236 and 0.572 mg/kg) > fallow (0.275 and 0.342 mg/kg). Stepwise multiple regression results demonstrated a correlation between TSN and soil organic carbon (SOC), while TSP was correlated with soil organic carbon (SOC) and fine-grained soil particles. Nugget % values indicated the following spatial variability for TSN: agricultural (1.4) > horticultural (3.2) > forest (3.9) > fallow land (4.8) > mixed land (5.8), whereas the spatial variability of TSP showed a similar trend for all land uses. The optimized conceptual framework and isotropy models varied for TSN and TSP on dependence on land use type. The results of this study revealed the spatial patterns and land userelated variations and improved the prediction of nutrient distribution, so contributing an optimized conceptual framework for future studies. Finally, this study provided crucial insights to enhance soil quality, fertility, agricultural sustainability, and environmental equilibrium in the ecologically fragile NWH region, contributing to solve a significant research gap in the global understanding of soil dynamics.

We outline an extension of Biot's theory of dynamic wave propagation in fluid-saturated media, which can be used to model dynamic soil-structure interaction in frictionless conditions across a wide range of soil saturation levels. In this regard, we present a comprehensive analysis of experimental evidence, the thermodynamic, and the theoretical basis of using the degree of saturation as Bishop's parameter in unsaturated soils. The analysis highlights the limitations of using this parameter to accurately model unsaturated soil behaviour, particularly as the soil approaches dryness. Based on the analysis, a new definition of effective stress is proposed, and the associated work-conjugate pairs are identified. Recommendations are made for constitutive modelling using the new definition of effective stress. Finally, we introduce a fully coupled finite element contact model that utilises the new effective stress definition. Through numerical examples, we demonstrate the model's capability to control the vanishing capillary effect on soil-structure interaction as the soil dries.