bluuebunny/crossref_metadata_2025 huggingface dataset:
Experimental study on the cementation level in an artificial rock with crushable grains
Authors: Tudisco Erika  , Casini Francesca  , Viggiani Giulia M.B.
Published: February 2025

The results of an experimental investigation of the effects of the degree of cementation on the mechanical behaviour of a porous artificial rock with crushable grains are presented. The studied material is an analogue of real cemented granular materials, such as pyroclastic weak rocks, carbonate sands, calcarenites and compacted decomposed granite. The present study aims to clarify the role of the degree of cementation in the relative importance or the sequential nature of mechanisms in natural material, i.e., granular rearrangement and breakage are expected to appear after de-bonding of particles. Cemented samples with different cement content were investigated. To understand the influence of the cementation, uncemented samples were reconstituted from a mixture of crushable grains and cement (not hydrated) in the same percentage by weight as the cemented (hydrated) samples, in order to obtain the same fraction of fines. Preliminary results show that, for the same confining stress, the cemented sample are more compressible than uncemented ones during isotropic compression; while, during axial loading, the cemented samples show a more rigid behaviour and a lower resistance.
The Bearing Capacity of Debris Flows: Laboratory and Centrifuge Analyses
Authors: Vallejo Luis E.  , Yoo Hankyu  , Caicedo Bernardo
Published: February 2025

Debris flows are made of a cohesive muddy matrix in which large dispersed particles are in suspension. In this study the bearing capacity of muds is investigated using penetration and centrifuge tests. For the penetration tests, solid wooden balls attached to a bar were used. The resistance offered by the mud to the penetration by the balls was evaluated. This resistance was related to the undrained shear strength of the mud, cu , the diameter (D) of the balls, and the closeness of the balls. It was determined that the closer a set of balls were to each other, the lower was the resistance offered by the mud. To evaluate how cohesive muds developed their bearing capacity, centrifuge tests were carried out on cylinders embedded in a soft clay matrix. The cylinders used had a diameter equal to 7 mm and a length equal to 2.5 cm. The cylinders were embedded in a soft mass of kaolinite clay having a water content of 30%, and a cu = 6 kPa. The soft clay mass with the embedded cylinders were placed in a box with transparent walls that allowed the recording of the deformation experienced by the clay surrounding the cylinders during the centrifuge tests. The box with the clay and the cylinders was subjected to acceleration equal to 200g. The centrifuge tests revealed that the clay around the cylinders developed a zone of slip surfaces on which the cu of the mud was mobilized. The cylinders with the slip zones moved as one piece through the mud. The combined cylinder-slip line zone had a diameter equal to 1.9d, where d is the diameter of the cylinders. When the cylinders were close to each other, their individual slip line zones overlapped causing a decrease in the bearing capacity of the mud.
Simple vs Advanced Interface Model: A Comparison Using a Deterministic Quality Approach
Authors: Stutz H.  , Mortara G.  , Wuttke F.
Published: February 2025

Various constitutive models for the contact between soils and structural elements have been proposed in the past. These models are important for holistic modelling geo-structures like piles, anchors, retaining walls etc. Different soil-structure interface models using different mathematical formulation have been defined and some of these are analyzed in this publication using a deterministic model quality approach. Experimental data from the literature serves as validation and verification for the models used in this paper.
Numerical assessment of shear-induced particle interactions under different loading conditions by means of axial and torsional interface shear tests
Authors: Martinez Alejandro  , Frost J. David
Published: February 2025

During the past few decades, numerical particulate simulations have shown that the global and interface shear behavior of geotechnical systems is significantly impacted by the loading conditions applied and is reflective of a range of different localized shear behaviors. For instance, experimental and numerical studies over a longer period of time have shown that the effective friction angles obtained from triaxial compression, triaxial extension, plane strain compression, plane strain extension and direct shear are different from each other (e.g. [1]). This paper presents the results of a study that uses Discrete Element Method (DEM) simulations to investigate this non-uniqueness of shear behavior from a particle-to-particle interaction perspective. In particular, investigations of interface shear simulations in axial and torsional directions in terms of relative induced particle displacements and rotations, volume changes, principal stress rotations, coordination numbers and slipping contact fractions allow for the study of the soil response under different loading conditions. This numerical study is utilized to compare to the conditions present in bearing capacity failures of shallow foundations in granular soils, which can reflect compression, extension or direct shear depending on the exact location within the failure zone or surface.
Limitations of a Critical State Framework Applied to the Behaviour of Natural and “Transitional” Soils
Authors: Coop Matthew
Published: February 2025

Critical state soil mechanics has provided an invaluable framework, essential for a proper understanding of the mechanics of many soils, both reconstituted and natural, at both small and larger strains. A limitation in its applicability results from robust forms of fabric in natural and reconstituted soils that mean that the critical states that can be defined in conventional tests do not correspond to a unique fabric. “Transitional” behaviour, in which the initial soil density plays a major role, seems also to result from robust fabrics. A number of examples of transitional behaviour are explored, emphasising that this type of behaviour does not threaten the applicability of critical state soil mechanics, but only the definition of intrinsic behaviour, such as we might require to examine the effects of structure. A range of behaviour appears from the examples, from very little convergence of specific volumes during compression or shear to a slow but gradual convergence. Even slow convergence, however, may still preclude the definition of normal compression and critical state lines that are independent of initial density within a useful stress range.
Interpretations of measurements for both rigid and flexible retaining system in cohesive cemented sandy soils in Lebanon
Authors: Kazan Youssam
Published: February 2025

In this present paper we present deflection measurements of rigid and flexible, anchored and not anchored retaining walls of a deep excavation in cemented sands located in the north east suburb of Beirut. Qualitative interpretation of these data shows specific phenomena for this kind of middle size projects. It leads us to proceed in a specific modeling more developed than simple back analysis in order to simulate the corresponding curves. As reminder, we make here also a general back view on the approaches adopted by engineers in order to rectify and define the good approach of geotechnical practices in such materials.
Small Strain Modulus of Bio-Cemented Sand
Authors: Duraisamy Youventharan  , Airey David
Published: February 2025

There is growing interest in using microbially induced calcite precipitation (MICP) for ground improvement. As part of a study to assess the performance of ex-situ mixed bio-cemented sand columns, a series of triaxial tests has been conducted to quantify the effects of the bio-cementation. Bender elements mounted in the end platens of a triaxial cell have been used to monitor the shear wave velocity throughout the cementation process and then during application of stress in the triaxial shearing tests. The results of tests on the bio-cemented sand are compared with tests on gypsum cemented and uncemented specimens. To assess the bio-cemented specimens a series of standard drained triaxial tests with bender elements were performed on Sydney sand which was mixed with urea contents in the range of 5 to 20% by weight, urea to calcium chloride in a 1:1 molar ratio, and a bacterial broth containing Bacillus Megaterium. Bacillus Megaterium is a ureolytic bacterium which hydrolyses urea to precipitate calcium carbonate (calcite). After curing the samples were subjected to various levels of mean effective pressure. The results show a good correlation between the amounts of urea and calcite precipitated and between the calcite precipitated and the degree of cementation achieved. For a given amount of cementation higher moduli and strengths were measured for the bio-cemented specimens than when using gypsum. Creating the bio-cementation by mixing produces homogeneous specimens with similar strengths and stiffnesses to the commonly used flushing technique.
Relationship Between Undrained Shear Strength And Shear Wave Velocity For Clays
Authors: Agaiby Shehab S.  , Mayne Paul W.
Published: February 2025

The interrelationship between undrained shear strength (su) and downhole shear wave velocity (VsVH) of normally consolidated (NC) and lightly overconsolidated (LOC: OCR < 2) to overconsolidated (OC) to highly overconsolidated (HOC: OCR > 10) clays is investigated in the presented study. The main objective of this research program is to develop a worldwide database of high quality in-situ geophysical and laboratory strength data from thirty seven well-documented geotechnical sites from locations in Australia, Brazil, Canada, China, Italy, Japan, South Korea, North Sea, Norway, Singapore, Sweden, Thailand, United Kingdom, USA, and Vietnam. The study includes undrained shear strength measurements on undisturbed samples of normally to lightly overconsolidated intact to overconsolidated and fissured clays using anisotropically-consolidated triaxial compression tests (CAUC). Shear wave velocities were measured in the field by downhole tests (DHT), in many cases via seismic piezocones (SCPTu). Analyses of the compiled database found approximate trends between undrained shear strength and shear wave velocity. Tentative correlations are explored by including other various parameters such as Atterberg limits, void ratio, overconsolidation ratio (OCR), and effective vertical stresses. The correlative trends may aid geotechnical engineers in helping to assess suprofiles in clay deposits in preliminary investigations and as an independent method in collaboration with sampling, lab testing, and other field data.
Frequency domain method in bender element testing – experimental observations
Authors: Camacho-Tauta Javier  , Ali Hassan  , Cascante Giovanni  , Viana da Fonseca António
Published: February 2025

In bender element (BE) testing, shear-wave velocities are measured using two main methods: time (pulse excitation) and frequency (sine sweep excitation) domain analysis. The time domain analysis is simple but requires subjective judgment for the non-automatic determination of the arrival time. Conversely, the frequency domain analysis can be performed automatically. However, its results show high variability because they are affected by the selection of different variables such as the frequency content of the excitation, the resonant frequency of the BE system, and the resolution of the frequency domain analysis. The reliability of the frequency domain method is studied in this paper by using experimental results from bender element and resonant column tests. Laboratory results show that amplification peaks in the transfer function of the BE system can significantly affect the shear wave velocity measurements (up to 300%). In addition, the high correlations coefficients typically observed at high frequencies are finally explained. A modified frequency domain analysis is proposed to enhance the reliability of the method using a high frequency narrowband excitation outside the resonant peaks of the BE system. Results from the modified frequency domain analysis tests show less than 10% error in the measurement of the shear wave velocity with respect to the RC results.
Observing breakage in sand under triaxial and oedometric loading in 3D
Authors: Karatza Zeynep  , Andò Edward  , Papanicolopulos Stefanos-Aldo  , Ooi Jin Y.  , Viggiani Gioacchino
Published: February 2025

The mechanisms involved in grain crushing/particle breakage are a common research topic in several fields including geomechanics, geoscience and particle technology. This topic is of interest to disciplines including material processing, minerals and mining engineering, geology and geophysics, since changes in the microstructure can lead to significant changes in the macroscopic bulk behaviour of a material. The main goal of this research is to develop a new understanding of the particle breakage mechanisms in a particulate system under specific loading regimes. This is achieved by studying the microscopic changes that an assembly of grains undergoes while being loaded/deformed. The possibility to study and visualise the 3D volume of a specimen during loading is given by x-ray computed tomography. The material under study is a sand (Caicos ooids) which consists of very rounded particles that grow from fragments of corals (Aragonite) with a D50of approximately 350μm. This material has been subjected to triaxial and oedometric loading, in order to compare the response of the material under different loading regimes. The acquisition of 3D images enables the study of the deformation of the microstructure and especially the evolution of grain breakage at different loading increments. The high resolution of the images enable the authors to clearly observe and perform algorithmic measurements of broken grains in small fragments. The image processing involves the creation of algorithms to track each individual grain, match the fragments to the intact labeled grains, in order to precisely describe the deformation throughout the loading process. The comparison between the oedometric and triaxial loading shows a clear difference in the distribution of damage. In the first case a dispersed pattern of breakage can be observed, indicating that breakage originates predominantly from the boundary conditions (especially the moving boundary – loading platten) and transmission of normal forces between particles, whereas in the second case a very clear strain localisation has been observed, which indicates breakage is mainly due to the deviatoric loading and observed mostly in a narrow shear band.
Description and Calibration of Triaxial tests with internal measurement of displacement on artificially cemented lateritic soil
Authors: Coutinho Roberto Q.  , Santos Jr. Olavo F.  , Severo Ricardo N.F.
Published: February 2025

This work is part of a larger study that was conducted in order to identify the instability mechanisms of a cliff in northeastern Brazil. Previous studies indicated that the stability of cliffs in this region is guaranteed by natural cementation between soil particles. A comprehensive study of the effects of cementation on the mechanical behavior of the soil was carried out in the doctoral thesis of Severo (2011) in a joint research UFPE-UFRN. Drained triaxial tests on artificially cemented samples were performed. The purpose of this article is to describe the equipment, the methodology developed to analyze the influence of cementation on soil behavior, and also to demonstrate the effects of using internal sensors to measure displacements. Pressure cells were used at the base and at the confining pressure line of the triaxial cell. Expansion and contraction of the samples were recorded by means of an electronic device to measure the volume variation. A load cell was used to measure the axial load on the sample. Displacement external sensors were coupled on the top of a triaxial cell, and internal sensors were attached to the sample. Internal instrumentation consisted of Hall Effect sensors, which allowed us to measure radial and axial displacement of the samples. Test results are presented in the form of deviator stress versus axial strain and volumetric strain versus axial strain curves. The results showed that the use of external sensors do not reflect the initial behavior of the soil under small strains. This initial behavior can only be observed with the use of equipment for measuring small displacements. This aspect is particularly important to measure the initial stiffness. For large strain conditions, the external measure proves to be more appropriate.
Local deformation measurement using image analysis technique in hollow cylindrical torsional shear test
Authors: Fauzi Usama Juniansyah  , Koseki Junichi  , Miyashita Yukika  , Hoshino Ryoichiro  , Nawir Hasbullah
Published: February 2025

A special image analysis technique is presented to improve local deformation measurement of sand specimen in hollow cylindrical torsional shear test. This technique involves the use of a latex membrane with dots marked in a grid pattern with approximately 5 mm spacing. These dots are tracked using a digital camera that synchronously shoots the membrane surface at desired time intervals. The dots on the membrane surface are tracked in terms of their center of mass using an image processing software with the accuracy of about 0.01 mm. By comparing image data at two different time intervals, the displacement of each dot during that time interval is obtained. The coordinate correction is performed on the pictures to cancel the distortion of an image by the effects of cylindrical shape of specimen, the camera lenses, and refraction from lighting through water in the cell. The high degree of polynomial equations with two variables are used to transform apparent coordinates to real coordinates. Strains are calculated based on the displacement vectors defined by the shape function matrix and the deformation matrix of the four nodes using two-dimensional linear isoparametric rectangular elements. In order to study liquefaction behavior, undrained cyclic loadings are conducted on Toyoura sand prepared by air pluviation and Katori sand prepared by moist tamping and water sedimentation. It is found that this image analysis technique and coordinate correction are powerful tool in measuring the local deformation. It is also found that the local deformations of specimens are different with the global one for both moist tamping and water sedimentation specimens.
Comparison between conventional and large scale triaxial compression tests on peat
Authors: Zwanenburg Cor  , Van M.A.
Published: February 2025

Large sized triaxial compression tests, diameter 40 cm and height 80 cm, are conducted on peat samples. The aim is twofold. First, heterogeneity of peat causes variation in parameters obtained from conventional laboratory testing. However, heterogeneity in peat is found at any level from microscopic to macroscopic. When considering stability of embankments on a peat foundation, variation in parameters at a scale which is smaller than the dimensions of the potential sliding plane will be (partly) averaged. So, the variation found in conventional laboratory tests might overestimate the variation in parameters relevant for the stability of embankments. Second, conventional tests on peat samples show some peculiar behaviour compared to tests on clay and sands, which might be explained by presence of fibres with a length equivalent to sample dimensions. Results of the large triaxial tests show that variation in parameters obtained from large tests is significantly smaller than found from conventional sized tests. The large tests on peat samples show the same behaviour as found for conventional tests, except that failure is found in large tests, which is usually not found in conventional tests.
Assessment of parameters of compressibility and strength of sedimentary clays found in the northeast region of Venezuela
Authors: Guevara C. Mariajosé
Published: February 2025

The objective of the present study is to assess strength and compressibility properties of sedimentary clays found offshore in the Gulf of Paria in Venezuela. The clays subject of study are normally consolidated to lightly “over consolidated” and are located in the Orinoco Delta, in sites where structures bore by piles will be placed. The soil samples were obtained using 3" thin-walled Shelby tubes in three boreholes of 120 meters depth. The parameters obtained are those corresponding to the reconstituted clay at 1.2-1.5 wL(intrinsic parameters). These were assessed by interpreting the results of one-dimensional consolidation tests. The intrinsic compression line and the compression curves were plotted for the reconstituted and the undisturbed clay, respectively. From these curves the ΔIvyparameter was obtained. This parameter is used in the pile design method of the Imperial College, to determine the value of the Kcratio. This ratio affects the local radial effective stress calculated. A different approach is to determine Kcusing the sensitivity of the clay obtained by undisturbed and remoulded triaxial UU tests. The value of Kcobtained by the compressibility curves method was compared to the correlation obtained by the UU sensitivities, for the clay between 0 and 64m depth.
Stress strain behavior of a desaturated loessian lightly cemented soil under triaxial compression test
Authors: Capdevila Julio A.  , Rinaldi Víctor A.
Published: February 2025

The upper most modern loess deposits of the central area of Argentina are characterized by an open structure made of fine sand and volcanic silt particles weakly bonded and usually in unsaturated conditions. Heterogeneity in loess is usually present and arises mainly from the non-homogeneous cementation of the soil mass. As saturation increases, the structure of loess collapses even under geostatic pressures. In this work, some results of triaxial compression test performed in loess are presented. Specimens were tested in saturated condition. Testing results allows analyzing the stress-strain behavior of loess in a wide range of strain levels, taking into consideration the influence of structure and confining pressure. Below the yielding stress (collapse), the soil behaves almost as linear elastic and stiffness is governed by degree of cementation. At higher stresses, the collapse potential of the soil skeleton is governed by a complex interplay between applied external pressure and internal forces due to cementation, and probably others attraction-repulsion forces developed at particles of colloidal size. Cementation causes an increase in stiffness, yielding stress and shear strength.
Micromechanical insight into the undrained instability of granular materials
Authors: Barreto Daniel  , Prada-Sarmiento Luis Felipe  , Ramos-Cañón Alfonso Mariano
Published: February 2025

There is no agreement between experimental researchers whether the point where a granular material responds with a large change of stresses, strains or excess pore water pressure given a prescribed small input of some of the same variables defines a straight line or a curve in the stress space. This line, known as the instability line, may also vary in shape and position if the onset of instability is measured from drained or undrained triaxial tests.
Effects of entrapped air bubbles on the mechanical behaviour of quasi-saturated soils
Authors: Lai B.T.  , Fabbri A.  , Wong H.  , Branque D.
Published: February 2025

This paper presents a model on the hydromechanical behavior of quasi-saturated soils containing entrapped air bubbles, constituting a discontinuous gaseous phase. These air bubbles reduce the compressibility of pore fluid hence impact on the mechanical behavior, while the liquid-gas interface gives rise to menisci and hence possibly suction effects on the soil skeleton. In parallel, air can dissolve in water and then migrate through the porous space by water flow and by diffusion. In practical situations, different parts of a soil mass can be at different degrees of saturation; transition through different saturation regimes relative both to space and time is possibly. The presentation of a theoretical model recently developed by the authors, capable of simulating such continuous transition relative to space and time, is the objective of this paper. A limited numerical study will also be presented to show the consistency of this model.
Calibration of rotational hardening model for clays based on dilatancy
Authors: Belokas Georgios  , Dafalias Yannis F.
Published: February 2025

Rotational hardening (RH) is a specific characteristic of clay plasticity constitutive modeling describing the rotation of the yield surface (YS) in stress space during plastic loading. RH reflects macroscopically the anisotropic fabric evolution at the microstructural level of particle mechanics. For calibration purposes of RH the determination of the evolving YS in stress space under fixed stress ratio loading, is a tedious and elusive process. On the other hand, the execution of radial stress path tests (e.g. isotropic and 1D compression) while measuring the corresponding stress–dilatancy relationship, is feasible even in common commercial laboratory practice. This paper presents a methodology for the calibration of the RH based on such simple laboratory tests and on an empirical stress – dilatancy relationship.
Integration Scheme For A Thermo-Elasto-Plastic Model With Unconventional Yield Surfaces
Authors: Zhou Annan  , Zhang Yue
Published: February 2025

An adaptive substepping explicit integration scheme with a novel loading-unloading decision method is developed here for the non-isothermal unified hardening (UH) model. The non-isothermal UH model includes a convex subloading surface in the p-q plane and a nonconvex subloading surface in the p-T plane. Because of the convex/nonconvex subloading surfaces, the conventional loading-unloading decision method used in stress integration schemes may lead to incorrect elasticity/elastoplasticity judgments. In addition, the conventional loading-unloading decision method is unable to determine the division point that separates the elastic segment from the elastoplastic segment. A simple but robust method, the Double Cosine (DC) method, is proposed in this paper to solve loading-unloading decision problems. The proposed DC method is then embedded into an adaptive substepping explicit integration scheme to implement the non-isothermal UH model. The accuracy and efficiency of the DC method are discussed by comparing the method with the conventional loading-unloading decision method (the CV method) and the root-finding loading-unloading decision method (the RF method).
Observation on Trace of Sand Boiling Erupted from Liquefied Sandy Ground and its Simulation by Laboratory Model Test
Authors: Horiuchi Yuki  , Anh Ngo Ngoc  , Kuwano Reiko  , Kuwano Jiro
Published: February 2025

A fine sand ground below filled soil and silt layers appeared to liquefy at Great East Japan earthquake. Undisturbed soil samples were taken from the sand and silt layers of about 2 to 3 m deep. There were some traces of boiled sand which elevated along cracks in the silt layer. X ray CT scanning was conducted for the undisturbed specimens to observe the micro structure of liquefied soil. The image obtained from X ray CT indicated the path of boiled sand erupted from liquefied sand layer. The overall structure of liquefied layer is mostly disturbed in contrast with laminar structures observed in a non-liquefied layer. A series of model tests was conducted to simulate the phenomenon of sand eruption. A model sand layer was prepared in the small soil chamber and the surface was covered by an acrylic lid with a slit opening. Water penetrated into the model sand ground from bottom to top. When the hydraulic gradient well exceeded critical hydraulic gradient, sand eruption has started. Horizontal movement of sand grains at the surface of liquefied layer was observed in the early stage of sand boiling. When larger hydraulic gradient was applied, vertical movement of sand occurred. Similar phenomenon was observed when the model sand ground was liquefied by the vibration.
Inherent Anisotropy of an Undisturbed and Compacted Loess Soil
Authors: Covassi Pedro A.  , Rinaldi Victor A.
Published: February 2025

This work discusses the result of an experimental study on inherent anisotropy of the loess soil found at Córdoba, Argentina. A cubical true triaxial device provided with flexible boundaries was used and the samples were subjected to an isotropic compression stress path. A brief description of the true triaxial device as well as the procedure for its assemblage and testing procedure is presented. Tests were performed on undisturbed and compacted samples. Undisturbed block type samples were recovered from open trenches. Compacted samples were made either by tamping or static compaction. The effect of compaction method on structural anisotropy was evaluated. Samples were prepared at dry of optimum, optimum and wet of optimum. Isotropic compression tests show that inherent structural anisotropy is found in both undisturbed and compacted specimens. Undisturbed samples are less compressible and develop higher degree of strain anisotropy respect the compacted samples at the same dry unit weight.
Influence of volcanic fly ash on the stress-strain-strength behaviour of loessial soils
Authors: Adami Agustin  , Rinaldi Victor A.
Published: February 2025

There are in nature a large number of soils formations that exhibit increments in stiffness and strength properties after deposition or even with aging after remolding and compaction. Post depositional diagenetic processes in the former case and various thyxotropic mechanisms in the second are usually postulated to explain the observed behavior. Argentinean loess at Cordoba city is normally a highly unstable soil which collapse when moistened. However, some specific horizons, shows very high shear strength properties in nature despite high water content, and even showing aging effects after remolding. Samples of this second type of loess were studied in this work to evaluate such behaviour, either in undisturbed and remoulded conditions. A set of mechanical test show that the increment in strength and stifness is time dependent and measured values reach almost a 70 % of that corresponding to undisturbed specimens after 28 days of aging. Effective stress tests and suction control during aging confirms that the regain in strength is due to a real cementation process and not to suction increasing as is usually assumed. Mineralogical and chemical tests confirm the presence of amorphous silica which in a high alkaline medium is showed here that generate a cementation reaction, bonding particles together and developing a stiffer structure.
Evaluation of Consolidation Behavior under Horizontal Drainage Condition Using Digital Image Analysis
Authors: Kim Joon-Young  , Chung Choong-Ki
Published: February 2025

Analytical solutions to predict the consolidation behavior of soft soils with vertical drains generally assume that soils are compressed only in the vertical direction. During consolidation, however, soils deform not only vertically but also radially in cases of radial drainage conditions, even though it is assumed that overall radial deformation is not occurred. Radial deformation may influence the consolidation response and also results in unexpected non-uniform soil conditions during and after consolidation. A new consolidation apparatus, which enables the deformation of a specimen to be visually observed, and the total vertical stress as well as the pore water pressure to be measured at several locations, was developed. Consolidation test using the developed apparatus was performed for reconstituted kaolinite specimen under horizontal drainage condition. Digital image analysis technique was adopted to analyze the consolidation deformation of the specimen. Horizontal deformation as well as vertical deformation developed during the consolidation process were obtained and the local consolidation behaviors were evaluated. The results show that consolidation behaviors are distinctive according to the distance from the drainage surface and the ground surface.
Effects of Initial Conditions on Strength of Acrylamide Grouted Sands
Authors: Bryson L. Sebastian  , Ortiz Ryan
Published: February 2025

Chemical grouts have long been used as soil stabilizers to reduce groundwater infiltration into underground structures and to inhibit seepage through earth dams and other impoundments. Among the chemical grouts, acrylamide grouts have shown increased usage within the last decade. Although these grouts are intended for water control rather than for strength, mechanical properties must be considered if there is a potential for movement of the grouted soil mass, such as deformations in the form of ground subsidence. In this study, the effects of initial soil conditions, such as moisture content and unit weight, on the strength of acrylamide grouted sands were investigated. This study found that the compressive strength of grouted sand was significantly influenced by the initial moisture content and dry unit weight of the sand material. The results show that linear relationships can be directly developed between strength, moisture content, and void ratio parameters.
Deformation of Microbial Induced Calcite Bonded Sands: A Micro-scale Investigation
Authors: Montoya Brina  , Feng Kai
Published: February 2025

Microbial induced calcite precipitation (MICP) is a novel ground improvement method that increases the strength and stiffness of sand using natural biogeochemical processes. This study investigates the mechanics of how microbial induced calcite bonds deform during loading. Surface energy measurements are conducted on silica and calcite substrates in order to assess whether the bonds experience a cohesive or adhesive failure. The results from the surface energy assessment indicate that calcite-calcite cohesion tends to be the weakest within the system and where the MICP bonded sands will likely fail. These findings are supported by particle contact loading tests, where two silica particles are bonded together through the MICP process, and the deformation of the silica particles and the calcite cement is monitored during shearing and axial loading. These results indicate the bond fails within the calcite phase. The results of the micro-scale study are then translated to the shear bands of a triaxial specimen of MICP sand. A triaxial specimen is cemented to a moderate level of MICP cementation, using shear wave velocity measurements as a process monitoring technique. The cementation degradation is monitored using shear wave velocity during drained shear and the thickness of the shear band is estimated. Scanning electron microscopy (SEM) is also used to evaluate the MICP bonded sand grains within and outside the shear band. The SEM results agree with the micro-scale investigation that cohesive failure appears to dominate during shearing.
Nuclear Security at State Level
Authors: Chetaine Abdelwahed  , Saidi Abdelmajid
Published: February 2025

The international community's involvement in, and awareness of, nuclear security has grown significantly in the past fifteen years. In the wake of the terrorist attacks on the United States of 11 September 2001, governments acknowledged the need to increase nuclear security. Although the September 2001 attacks were not nuclear or radiological in nature, there was a fear that future attacks might be, especially if non-state actors were able to access nuclear material. Growing numbers of both potential threats and nuclear facilities around the world led the international community to seek greater security measures and ensure that states are equipped to implement those measures. Since the beginning of the nuclear age, the term ‘nuclear security’ has evolved significantly in both how it is defined and how states respond to it. At present, the International Atomic Energy Agency (IAEA) defines nuclear security as, ‘the prevention and detection of, and response to, theft, sabotage, unauthorised access, illegal transfer or other malicious acts involving nuclear material, other radioactive substances or their associated facilities [1].
The Human Dimension of Nuclear Security
Authors: Padoani Franca
Published: February 2025

The human dimension, encompassing the security culture and human resources development, is the foundation of a sustainable security regime. On the one hand, the origin of any event with radiological consequences can ultimately be tracked down to the human factor; on the other hand, nuclear security culture and adequate human resources at all levels (including regulators, law enforcement agencies and industrial actors) are essential components of an effective security regime and its sustainability.
Automatic Tuning of Task Scheduling Policies on Multicore Architectures
Authors: Bhat Akshatha  , Lenharth Andrew  , Nguyen Donald  , Yi Qing  , Pingali Keshav
Published: February 2025

The performance of multi-threaded applications depends on efficient scheduling of parallel tasks. Manually selecting schedulers is difficult because the best scheduler depends on the application, machine and input. We present a frame-work that automatically selects the best scheduler based on empirical tuning results. We applied our framework to tune eleven applications parallelized using OpenMP, TBB or the Galois system. Depending on the application and machine, we observed up to 4X performance improvement over the default scheduler. We were also able to prune the search space by an order of magnitude while still achieving performance within 16% of the best scheduler.
Portable Parallelization of the EDGE CFD Application for GPU-based Systems using the SkePU Skeleton Programming Library
Authors: Sjöström Oskar  , Ko Soon-Heum  , Dastgeer Usman  , Li Lu  , Kessler Christoph W.
Published: February 2025

EDGE is a complex application for computational fluid dynamics used e.g. for aerodynamic simulations in avionics industry. In this work we present the portable, high-level parallelization of EDGE for execution on multicore CPU and GPU based systems by using the multi-backend skeleton programming library SkePU. We first expose the challenges of applying portable high-level parallelization to a complex scientific application for a heterogeneous (GPU-based) system using (SkePU) skeletons and discuss the encountered flexibility problems that usually do not show up in skeleton toy programs. We then identify and implement necessary improvements in SkePU to become applicable for applications containing computations on complex data structures and with irregular data access. In particular, we improve the MapArray skeleton and provide a new MultiVector container for operand data that can be used with unstructured grid data structures. Although there is no SkePU skeleton specifically dedicated to handling computations on unstructured grids and its data structures, we still obtain portable speedup of EDGE with both multicore CPU and GPU execution by using the improved MapArray skeleton of SkePU.
Structured parallel implementation of Tree Echo State Network model selection
Authors: Danelutto Marco  , Gallicchio Claudio  , Micheli Alessio  , Torquati Massimo  , Virgilio Daniele
Published: February 2025

In this work we discuss the parallelization of the model selection process for Tree Echo State Networks. We consider two different “structured” parallelization strategies: one based on functional replication of the computations needed to evaluate the different steps in the model selection process, and the other one exposing and exploiting the dependency graph in the aggregate selection process computations. Both parallelizations have been implemented using FastFlow. Experimental results on state-of-the-art multicore architectures are discussed in detail that demonstrate the feasibility and the efficiency of the parallelizations.
Java Implementation of Data Parallel Skeletons on GPUs
Authors: Ernsting Steffen  , Kuchen Herbert
Published: February 2025

Multi-core processors with up to 8 cores and more as well as GPUs with thousands of cores are omnipresent. In order to fully exploit their parallel computing capability, programmers have to deal with low-level concepts of parallel programming. These low-level concepts constitute a high barrier to efficient development of parallel applications. A higher level of abstraction would be desirable.
Evaluation of 3-D Stencil Codes on the Intel Xeon Phi Coprocessor
Authors: Hernández Mario  , Cebrián Juan M.  , Cecilia José M.  , García José M.
Published: February 2025

Accelerators like the Intel Xeon Phi aim to fulfill the computational requirements of modern applications, including stencil computations. Stencils are finite-difference algorithms used in many scientific and engineering applications for solving large-scale and high-dimension partial differential equations. However, programmability on such massively parallel architectures is still a challenge for inexperienced developers.
Algorithmic scheme for hybrid computing with CPU, Xeon-Phi/MIC and GPU devices on a single machine
Authors: Contassot-Vivier Sylvain  , Vialle Stephane
Published: February 2025

In this paper, we address the problem of the efficient parallel exploitation of different types of computing devices inside a single machine, to solve a scientific problem. As a first step, we apply our scheme to the Jacobi relaxation. Despite its simplicity, it is a good example of iterative process for scientific simulation. Then, we evaluate and analyze the performance of our parallel implementation on two configurations of hybrid machine.
Active Resource Management for Multi-Core Runtime Systems Serving Malleable Applications
Authors: Grelck Clemens
Published: February 2025

Malleable applications are programs that may run with varying numbers of threads and thus on varying numbers of cores because the exact number of threads/cores used is irrelevant for the program logic and typically determined at program startup.
A general tridiagonal solver for coprocessors: Adapting g-Spike for the Intel Xeon Phi
Authors: Venetis Ioannis E.  , Sobczyk Alexandros  , Kouris Alexandros  , Nakos Alexandros  , Nikoloutsakos Nikolaos  , Gallopoulos Efstratios
Published: February 2025

Manycores like the Intel Xeon Phi and graphics processing units like the NVIDIA Tesla series are prime examples of systems for accelerating applications that run on current CPU multicores. It is therefore of interest to build fast, reliable linear system solvers targeting these architectures. Moreover, it is of interest to conduct cross comparisons between algorithmic implementations in order to organize the types of optimizations and transformations that are necessary when porting in order to succeed in obtaining performance portability. In this work we aim to present a detailed study of the adaptation and implementation of g-Spike for the Xeon Phi. g-Spike was originally developed to solve general tridiagonal systems on GPUs, on which it returns high performance while also solving systems for which other state-of-the-art general tridiagonal GPU solvers do not succeed. The solver is based on the Spike framework, using QR factorization without pivoting implemented via Givens rotations. We show the necessary adaptations on the Xeon Phi because of the significant differences in the programming models and the underlying architectures as well as the relative performance differences for data access and processing operations.
A Parallel Algorithm for Decomposition of Finite Languages
Authors: Jastrząb Tomasz  , Czech Zbigniew J.  , Wieczorek Wojciech
Published: February 2025

The paper deals with the problem of finite languages decomposition, which is believed to be computationally hard. Our objective is to propose an improved parallel algorithm finding all non-trivial decompositions of a finite language L, provided that they exist. The paper introduces a novel method of pruning a solution space by defining locally significant states of an automaton A accepting language L. It also proposes an adaptive way for adjusting the algorithm parameters, which has not been studied yet in the past. The performance of the algorithm is experimentally verified on a set of large languages and the results are reported. The algorithm proves to be successful in finding the decompositions of selected languages in a reasonable amount of time.
Workload distribution and balancing in FPGAs and CPUs with OpenCL and TBB
Authors: Asenjo Rafael  , Navarro Angeles  , Rodriguez Andres  , Nunez-Yanez Jose
Published: February 2025

In this paper we evaluate the performance and energy effectiveness of FPGA and CPU devices for a kind of parallel computing applications in which the workload can be distributed in a way that enables simultaneous computing in addition to simple off loading. The FPGA device is programmed via OpenCL using the recent availability of commercial tools and hardware while Threading Building Blocks (TBB) is used to orchestrate the load distribution and balancing between FPGA and the multicore CPU. We focus on streaming applications that can be implemented as a pipeline of stages. We present an approach that allows the user to specify the mapping of the pipeline stages to the devices (FPGA, GPU or CPU) and the number of active threads. Using as a case study a real streaming application, we evaluate how these parameters affect the performance and energy efficiency using as reference a heterogeneous system that includes four different types of computational resources: a quad-core Intel Haswell CPU, an embedded Intel HD6000 GPU, a discrete NVIDIA GPU and an Altera FPGA.
A Run-Time System for Partially Reconfigurable FPGAs: The case of STMicroelectronics SPEAr board
Authors: Charitopoulos George  , Pnevmatikatos Dionisios  , Santambrogio Marco D.  , Papadimitriou Kyprianos  , Pau Danillo
Published: February 2025

During recent years much research focused on making Partial Reconfiguration (PR) more widespread. The FASTER project aimed at realizing an integrated toolchain that assists the designer in the steps of the design flow that are necessary to port a given application onto an FPGA device. The novelty of the framework lies in the use of partial dynamic reconfiguration seen as a first class citizen throughout the entire design flow in order to exploit FPGA device potential.
Exploring Automatically Generated Platforms in High Performance FPGAs
Authors: Skrimponis Panagiotis  , Zindros Georgios  , Parnassos Ioannis  , Owaida Muhsen  , Bellas Nikolaos  , Ienne Paolo
Published: February 2025

Incorporating FPGA-based acceleration in high performance systems demands efficient generation of complete system architecture with multiple accelerators, memory hierarchies, bus structures and interfaces. In this work we explore a set of heuristics for complete system generation, with the objective of developing automatable methodology for system level architectural exploration and generation. Our experimental analysis on two test cases demonstrates that applying a set of system optimization heuristics incrementally on a baseline system configuration, we can converge to efficient system designs and reach target performance.
Experiences Porting Production Codes to Xeon Phi Processors
Authors: Farsarakis Emmanouil  , Jackson Adrian  , Reid Fiona  , Scott David  , Weiland Michèle
Published: February 2025

This paper outlines our experiences with porting a number of production simulation codes to the Xeon Phi co-processor. Large scale production simulation codes present a challenge for optimisation on any platform, and can be even more problematic for accelerator hardware as the codes contain language operations or functionality that are hard to get good performance from on novel hardware. We present the challenges we have experienced porting two large FORTRAN production codes: GS2 and CP2K. We discuss the strategies, which have proven useful or otherwise, for obtaining good performance on Xeon Phi. We also discuss the reasons why achieving good performance for large-scale codes is problematic.