This paper presents parametric studies that assess the role of loading factors (i.e., number of cycles, frequency, and amplitude) on liquefaction-induced failure by performing numerical simulations. Most of the existing literature considers the effects of the soil properties on the development of excess pore pressure with few research endeavours focusing on the effects of the input motion itself. Numerical simulations are performed herein, via the advanced software platform OpenSees, to generate several finite element models that consider non-linear development of pore pressure inside the soil. Several sinusoidal inputs were considered to study the effects of the various loading factors and compare the responses. The main findings arise from evaluating the effects of several input motion parameters (number of cycles, frequency, and amplitude) on soil liquefaction through numerical simulations. This research study, based on state-of-the-art knowledge, may be applied to assess future seismic events and to update or propose new code provisions for soil liquefaction.

The interaction between a foundation and its supporting soil involves several different energy dissipation mechanisms. For example, sliding of a foundation element is a soil-structure interaction component that can alter the seismic demand on a foundation as well as its superstructure. Experimental data from tests with realistic boundary and stress conditions is required to characterize the frictional properties at the soil-foundation interfaces in order to model sliding of shallow foundations. To this end, a series of large-scale monotonic laboratory shear tests were performed to study the interface between a shallow concrete foundation element and Ottawa F-55 sand under varying normal pressures, shearing rates, and foundation surface roughnesses and textures. The soil-foundation interface behavior was evaluated through a combination of global measurements of force and displacement, as well as by capturing the localized effects around the interface. This article describes the dependency of the interface behavior on each of the aforementioned variables. The results indicate that when subrounded fine sand comes into contact with surfaces of varying roughness, it exhibits different shear resistance behaviors. The findings further reveal insights into the dependency of the interface frictional characteristics and shear failure zone on the real area of contact, which includes irregularities on the surface. The data further utilized to study the impact of adopting different interface friction assumptions on the finite element model’s interface shear response being subjected to monotonic loading. Using the internal friction angle, or a factored down value, as an estimation for interface friction may lead to an erroneous or unconservative prediction of the superstructure response.

The analysis of sands, and the foundation systems with which they interact, are largely dependent on macroscale behavioral parameters that represent the aggregated response of several microscale characteristics. This research paper examines the influence of surface texture, or smoothness, on the behavior of sands. The challenge of estimating or measuring smoothness, due to its microscale feature domain, is addressed through an examination of six artificially graded sand specimens. These specimens are evaluated both visually and numerically to characterize their surface smoothness. The first approach described is a simple visual method that uses a smoothness scale consistent with those of roundness and sphericity. This method, which can be performed with a tool as simple as a hand lens, evaluates a group of representative particles collectively. The second approach is also a visual evaluation, but it utilizes images obtained via scanning electronic microscopy, traditional optical microscopy, and newer low-cost digital microscopes that can be rapidly connected to a smartphone or laptop. To validate these visual estimates, a novel third approach is introduced. This approach is a more objective numerical analysis measurement technique that enables rapid and economic quantification of smoothness. This technique may assist both practitioners and academics in their understanding of the macroscale response of coarse-grained soils. In addition to the visual methods, this research also conducted several laboratory index tests to observe the mechanical behavior of the specimens, considering their particle shape and surface smoothness properties. The results indicate that angular sands have greater minimum and maximum void ratios, a larger difference between the minimum and maximum void ratios, greater critical state friction angles, and greater flow rates through an orifice of fixed size. When adjusted for surface smoothness using the proposed approach, the behavior of the sands—particularly the limit void ratio results—appears to be more predictable in some cases. These results provide additional evidence of particle smoothness contributing to the strength behavior of sand, which may be particularly useful in the domains of slope stability, land reclamation, soil–structure interaction, and soil dynamics.