We propose a test procedure to quantify the response of dry sand to cyclic compressional loading under constrained conditions. The test procedure is designed to represent the response of sand layers to upward propagating P-waves during an earthquake event. Such P-waves are prominent within the vertical component of earthquake ground-motions, which is often ignored or simplified in common practice of seismic hazard analysis, despite its potential damaging effects. In the proposed method, the lateral deformation is restrained within a triaxial device, through variations of the cell pressure, thus maintaining pure compression while allowing moderate to large axial strains. Both dry and saturated samples are tested, and the compressive stiffness is computed from the full stress-strain loops. We show that as long as drained conditions are maintained and volume changes are allowed - the response of a saturated sample to slow cyclic loading is representative of the response of dry sand to seismic loading, despite the differences in saturation and in strain rates. Finally, we compare the proposed method to cyclic loading within a rigid cell and discuss the differences and limitations that the new proposed method overcomes.

Recycled tyre aggregates (soft particles) mixed with common granular material such as crushed rock (rigid particles) are considered effective solutions for a range of applications in transportation geotechnics in recent years. While extensive research has been conducted on the mechanical properties and behaviour of sand-rubber combinations as unbound soft-rigid mixtures, most studies on bound soft-rigid mixtures have focussed on utilizing brittle binders like Portland cement. On the other hand, there have been only a few studies in recent years exploring the behaviour of soft-rigid mixtures bonded with non-brittle binders. This study aims to enhance our understanding of the impact of binder elasticity and stiffness on the compressibility mechanism of soft-rigid granular mixtures. One-dimensional compression tests complemented with shear wave velocity measurements were conducted on bound samples, using different types of binders, to investigate how the characteristics of binders influence the fabric of the mixture and, consequently, its behaviour. The findings indicate a multiphase behaviour of bound mixtures, in contrast to the single-phase behaviour of unbound mixtures, particularly for higher contents of binder and for brittle and semi-flexible binders.

In recent years, there has been a growing recognition of the importance of vertical ground motions in the seismic design of engineering structures. A comprehensive understanding of the small-strain constrained modulus M 0 , which is a key input soil parameter, is essential for conducting a reliable analysis of vertical site response. Natural soils in engineering scenarios are often subjected to various anisotropic stress states, and the role of such loading on M0 0 is a critical concern that remains incompletely understood. This paper presents a systematic experimental program aimed at addressing this issue. Using a triaxial apparatus, sand specimens initially isotropically consolidated were subjected to various anisotropic stress states, including triaxial compression and triaxial extension. The evolutions of M0 0 at different stress states were captured by exciting elastic compression waves through embedded bender-extender elements. The specimens were tested under a wide range of states in terms of void ratio, axial stress, and radial stress. The study demonstrates that the impact of stress anisotropy is complex, depending on the magnitude of the stress ratio, the loading mode, and the initial state of the specimen. A practical model is suggested for the improved characterization of M0 0 under the anisotropic stress states. This model considers two primary mechanisms that are associated with the effects of stress anisotropy.

The modern development of urban areas is related to, among others, the location of industrial facilities on the outskirts of cities. More and more often, commercial buildings are founded on areas that have not been used for construction so far. Such areas include, among others: reclaimed lignite mine banks in the Konin region. The man-made soil is a chaotic mixture of fragments of glacial tills and Pliocene clays, often exceeding 20 m in thickness, which is naturally consolidated over time. Due to the method of formation of the embankment, despite the fact that banks are made of natural soil, their strength and deformation characteristics clearly differ from those characteristic of lithologically similar soils deposited as a result of geological processes. In this case, the use of a standard test approach may overestimate the strength and stiffness of the soil. Due to the complex structure of the bank in-situ tests were used for geotechnical exploration: CPTU and FVT, as well as laboratory tests in a triaxial apparatus and an oedometer. The results were compared with the results of studies conducted in similar naturally deposited soils. The obtained results provide valuable geotechnical characteristics of the embankment soil, which in its large fragments is built of natural soil clasts. The obtained results indicate a relatively small change in the geotechnical properties of the soils incorporated into the embankment within individual clasts of the natural soil (on a local scale) and a clear deterioration in the scale of the entire embankment, treated as the impact zone of building structures.