V. Santiago Quinteros

Bio: V. Santiago Quinteros is an academic researcher from Norwegian Geotechnical Institute. The author has contributed to research in topics: Slurry & Fluvial. The author has an hindex of 1, co-authored 3 publications receiving 1 citations. Previous affiliations of V. Santiago Quinteros include Imperial College London.

The initial fabric of undisturbed and reconstituted fluvial sand

Abstract: High-quality undisturbed samples of fluvial sand were obtained from the field using the ground freezing technique. In the laboratory, the in situ void ratio of these high-quality undisturbed frozen...

Quality assessment of a new in-mould slurry deposition method for triaxial specimen reconstitution of clean and silty sands

Abstract: An innovative specimen reconstitution technique for sandy and silty soils that simulates underwater deposition is presented and evaluated. The technique is an upgraded version for triaxial testing of the well-established slurry deposition method. This novel setup integrates the reconstitution mould and the mixing tube into a single unit to avoid transferring the sample from the mixing tube to the mould. This subtle, but critical, modification enables reconstitution of very loose specimens as sample transfer disturbance, which can be significant, is eliminated. The quality of specimens prepared by the new reconstitution method was assessed by experiments on a clean sand from the UK (Ham River sand) and a silty sand from Norway (Oysand). The method, as any slurry-based procedure, is capable of producing homogeneous specimens with high initial degree of saturation, even in the absence of back pressure. The procedure is shown to be suitable for sands with or without fines. Moreover, the new method is able to achieve a wide range of initial void ratios, from very loose to very dense, without imposing any particle crushing in the latter case.

Characterisation of sand-steel interface shearing behaviour for the interpretation of driven pile behaviour in sands

Abstract: The installation and loading of steel piles driven in sands modifies both the piles' surface topography and the characteristics of the granular materials present adjacent to the pile shaft. Large-displacement ring shear interface tests incorporating pre-conditioning stages are capable of reproducing such physical processes in the laboratory and can generate case-specific interface design parameters. This paper summarises laboratory research that characterised the interface shearing behaviour of three natural sandy soils retrieved from field test sites (Dunkirk, France; Blessington, Ireland; Larvik, SE Norway) where extensive piling studies on micro and industrial scale driven piles have been carried out. The programme examined the influences of soil characteristics (physical properties and chemical compositions), interface type (mild steel or stainless steel) and surface roughness, and highlighted the significant effects of normal effective stress level and ageing time duration. Remarkable trends of increasing interface friction angles with elevated normal effective stress levels and prolonged ageing were observed. The results from supplementary small-displacement direct shear interface tests and triaxial tests are also reported. The experiments are interpreted with reference to earlier studies to develop an overview of interface shearing characteristics between steels and sandy soils and provide important insights into the mechanisms of axial capacity increases applying to steel piles driven in sands.

Suggested Method of Specimen Preparation for Triaxial Tests on Partially Saturated Sand

Abstract: In geotechnical engineering, triaxial testing is widely adopted to evaluate the mechanical behavior of sand. Methods of specimen preparation for triaxial tests on dry and completely saturated sand are well established in the literature, whereas very little guidance exists on the preparation of partially saturated sand at relatively high degrees of saturation (typically Sr > 80 %). The purpose of this study is to elucidate the suitable method of specimen preparation for partially saturated sand using sodium percarbonate and investigate the effects of partial saturation on the undrained cyclic behavior of sand. Loosely and densely packed specimens are prepared in a dynamic triaxial apparatus through dry pluviation and tamping of sand. For tests on fully saturated sand, dry specimens are flushed with carbon dioxide and deaired water and saturated applying back pressure. For tests on partially saturated sand, sodium percarbonate is used in either fine powder or aqueous solution form to create oxygen bubbles in the voids, reducing the degree of saturation of specimens. The results suggest that not only the degree of saturation but also the way partially saturated specimens are prepared affects the liquefaction resistance. At the same level of saturation and principal stress difference, specimens prepared with the aqueous solution exhibit higher liquefaction resistance than those prepared with the powder. The solution of sodium percarbonate proves to be a more reliable and repeatable technique for preparing partially saturated triaxial specimens with relatively high degrees of saturation.

The initial fabric of undisturbed and reconstituted fluvial sand

Abstract: High-quality undisturbed samples of fluvial sand were obtained from the field using the ground freezing technique. In the laboratory, the in situ void ratio of these high-quality undisturbed frozen...

Use of Combined Static and Dynamic Testing to Quantify the Participation of Particles in Stress Transmission

Abstract: A number of research studies have recognized that not all particles in a sand specimen are active in stress transmission, particularly in the case of gap-graded soils. This has implications for the use of the global void ratio (e), and variables/parameters that depend upon e, to predict the influence of the state on the mechanical behavior of gap-graded soils. This study explores the possibility of comparing the shear stiffness determined in dynamic wave propagation tests (Gdyn) with stiffness values determined in small-strain probes (Gsta) to assess the extent to which all the particles in a specimen are actively engaged in stress transmission. The idea is initially developed using three-dimensional discrete element method simulations and considering ideal specimens. The practical application of this approach is then tested in a series of drained triaxial compression tests. The numerical studies considered both specimens with continuous, linear particle size distributions as well as gap-graded soils. The results show that the ratio Gsta/Gdyn may be associated with the ratio between the bulk density calculated considering only the stress transmitting particles, ρm, and the bulk density calculated considering all particles, ρ. The ratio ρm/ρ is determined by the proportion of inactive particles, which varies with the proportion by mass of finer particles in the soil (Ffiner) for gap-graded soils. The relationship between Gsta/Gdyn(e) and Ffiner enables a qualitative assessment of the proportion of inactive particles. The corresponding experimental test results show a similar but weaker correlation between the ratio of Gsta/Gdyn and Ffiner, this weaker correlation may be attributed to the differences between the simulations and the experimental conditions. However, despite the challenges with experimental implementation, the data presented here support the idea that it may be possible to qualitatively estimate the proportion by volume/mass of inactive particles in physical samples by comparing the stiffness results of static and dynamic testing.

The initial fabric of undisturbed and reconstituted fluvial sand

Abstract: High-quality undisturbed samples of fluvial sand were obtained from the field using the ground freezing technique. In the laboratory, the in situ void ratio of these high-quality undisturbed frozen samples was replicated using four different reconstitution methods: dry deposition, moist tamping, water sedimentation (by spooning) and slurry deposition. The initial fabric of the specimens was evaluated using X-ray micro-computed tomography and advanced image analysis. Initial fabric features were assessed in terms of the particle orientation, anisotropy, void ratio distribution and particle sizes within the specimens. Fabric analysis results suggest that none of the laboratory reconstitution techniques used captures the true three-dimensional initial fabric of undisturbed fluvial sand. However, the slurry deposition method managed to reproduce the inherent particle orientation, anisotropy and the variations of void ratio and particle sizes of the undisturbed fluvial sand. This observation explains why previous rigorous studies on the macro-mechanical behaviour of sands deposited under water have systematically demonstrated that slurry deposition is the most suitable method to reconstitute in the laboratory natural sands deposited under water. This has major implications for geotechnical testing and analyses of liquefaction of sands deposited under water such as fluvial, offshore and tailings sands.

Description of sand–metal friction behavior based on subloading-friction model

Abstract: Abstract A subloading-friction model is formulated to describe the smooth transient variation from static friction to kinetic friction, the recovery to static friction after the sliding velocity decreases, and the accumulation of sliding displacement under the cyclic loading of contact stress. In the past relevant studies, however, the model formulation used for simulations is limited to the hypoelastic-based plasticity framework, and the validation of the model is limited to simulations of the test data for metal-to-metal friction. In this study, the formulation of the subloading-friction model based on a hyperelastic-based plasticity framework is adopted. In the fields of civil, geotechnical, agricultural engineering, and terramechanics, the interaction between soils and metals is critical, as reflected in construction and agricultural machinery, foundation piles, and retaining walls. The validity of the model for describing the friction between various sands and metals is verified by simulations of the experimental data under monotonic and cyclic loadings.