bluuebunny/crossref_metadata_2025 huggingface dataset:
Practical implications of gas-water interactions in soils
Authors: Leroueil Serge  , Hight David W.  , Cabral Alexandre R.
Published: February 2025

Gas and water in soils interact through the physical laws of Boyle, Henry, Darcy and Fick and through the capillarity law; this interaction has a large number of practical implications and applications in geotechnical engineering. Those examined in this paper are: cavitation; implications of occluded gas; implications of gas exsolution on hydraulic conductivity, pore pressures and sampling; gas hydrate dissociation; saturation of soil samples; infiltrations in soils; capillary barriers; and transient pore pressures in earth dams.
TBM Performance, Prognosis and Risk Caused by Faulting
Authors: Barton Nick
Published: February 2025

World records for drill-and-blast tunnelling from Norwegian contractors, bear witness to numerous weeks of more than 100m, and an exceptional 5.8 km in 54 weeks, also from one face. Earlier hard-rock world records using high-powered TBM in Norway, but most frequently and more recently, the records with Robbins TBM through non-abrasive limestones in the USA, provide numbers in meters per day, per week, and per month, which are of course, even more remarkable. Unfortunately there are contrary and undesirable TBM records, which are occasionally recurring events so not records, which see TBM stopped for months or even years in fault zones, or permanently buried in mountains. The many orders of magnitude range of performance suggest the need for better investigations, better choice of TBM, and better facilities for improving the ground ahead of TBM, when probe-drilling indicates that this is essential. Control of water, and improved stand-up behaviour in significant weakness zones and faults may demand drainage, which can be unending, and pre-injection. Fortunately there are increasing signs that this is recognized by TBM manufacturers: more guide-holes for drilling pre-injection umbrellas are seen through front-shields nowadays. A little acknowledged fact is that when all hours are included, TBM will generally decelerate as tunnel length and time increases. This is usually seen after improved performance during the learning curve. Deceleration is also a general trend during world-record setting performances. This means that utilization U is equal to the ratio of actual advance rate and penetration rate, AR/PR, only for specified time intervals, because U is time-dependent. This is rarely quantified by designers, and is therefore a source of risk, by default. Another important item for correct prognosis is the recognition that reduced penetration rate PR can sometimes occur when thrust is increased by the TBM operator, due to exceptionally resistant rock mass formations. Each of the above, and PR sensitivity to a wide range of cutter forces, UCS and abrasiveness, are provided in the empirical QTBM method. This method explains variable progress in jointed rock, which is sometimes fast, and also quantifies the likely delays in untreated, or pre-injected, fault zones.
Undrained Failure of Fine-Grained Soils with Particular Reference to Shallow Slope Instability
Authors: Panta Anand  , Nishimura Satoshi
Published: February 2025

This paper discusses the undrained strength of heavily overconsolidated Izumi clay and a clay-sand mixed (C-S) soil at different states (i.e. intact, reconstituted, and compacted) in terms of the magnitude of strength and the degree of non-linearity of failure envelopes at low effective stress levels (5-20kPa), corresponding to the shallow slope failure expected at 1-2m of depth. A series of constant-volume direct shear (DS) tests supplemented by hollow cylinder (HC) simple shear tests was performed from low consolidation stresses. To express the non-linearity of failure envelopes at low stress ranges, a non-linear power law strength criterion was applied. The results suggest that the normalized strength and the degree of its non-linearity of Izumi clay at intact states were much higher than at equivalent reconstituted states, potentially due to true inter-particle cohesion. The compacted states led to slightly lower normalized strength than the reconstituted state in Izumi clay, while they did not result in significant difference in the C-S soil. Inclusion of coarser particle in a clayey soil seems to reduce the low stress level non-linearity of the strength envelopes at both states. All the above observations suggest that the low stress level strength characteristics and their dependence on states are significantly influenced by soil types; possibly by soil gradation.
Testing Tube Specimens from Soft Clay Deposits Containing Variable Amounts of Shells
Authors: Lim Guan T.  , Boukpeti Nathalie  , Carraro J. Antonio H.  , Pineda Jubert A.
Published: February 2025

This paper presents the results of an experimental program aimed at characterizing tube specimens from an estuarine soft clay deposit, which contains variable amounts of shells. The characterization of the natural clay involved two non-destructive techniques for assessing specimen quality, namely computed axial tomography (CAT) and shear wave propagation using bender elements, as well as one-dimensional consolidation tests for evaluating soil compressibility. Image analysis of CT scans was used to quantify the volumetric shell fraction and its influence on the compressibility parameters derived from one-dimensional compression tests. The experimental results show that both the compressibility and the small-strain stiffness of the natural soft clay are influenced by the volumetric shell fraction.
Capillary Rise in Corners of Rough Pores: Laboratory and Theoretical Analyses
Authors: Tang Shirley  , Vallejo Luis E.  , Caicedo Bernardo
Published: February 2025

The capillary rise in pores forming part of soils and rocks is usually obtained assuming the pores are smooth circular capillary tubes. The water rises in these tubes to a height called the height of capillary rise. This height is easily calculated using the surface tension and the unit weight of the water, the contact angle, and the diameter of the circular tube. However, pores in soils and rocks are not circular nor smooth but rough. This study presents the results of laboratory and theoretical analyses designed to calculate the height of capillary rise in tubes with rough walls. To obtain this height, laboratory experiments were conducted on the height of capillary rise experienced by two glass surfaces meeting each other at a corner and making a wedge. The wedge represents the sharp corners of a rough pore. The angle between the two surfaces making the wedge was varied between 1° and 30°. The height of capillary rise was obtained at various distances from the corner of the wedge. It was found that the height of capillary rise increases as the distance from the corner of the wedge decreases. Also, as the angle of the wedge increases, the height of capillary rise decreases in the wedge. These findings were used to interpret the way capillary water moves in the rough pore system of soils and rocks (shales). The profile of the pore walls in soils and shales were obtained from thin sections of soil and rock samples. Using the way capillary water moves in the sharp corners of rock voids, the non-slaking of shales was explained.
Primary Consolidation Settlement of Embankments Constructed on Young Bay Mud of San Francisco Bay
Authors: Bathe Abhijit  , McCabe W. Martin  , Bryson L. Sebastian  , Lobedan Frank  , Won Samuel
Published: February 2025

Active Airports are complex environments for geo-construction. Construction activities must not interfere with takeoff and landing operations and the final earthwork must provide adequate bearing support for the aircraft and support equipment. This case study discusses challenges faced in the design and construction of two 5 to 6 ft (1.52 to 1.83 m) high embankments for new taxiways at Oakland International Airport in Oakland, CA. The taxiway embankments were constructed partly on a manmade wetland located on top of Quaternary Young Bay Mud (YBM). YBM is a thick deposit of soft, saturated, unconsolidated silty clay in the San Francisco Bay area which exhibits low shear strength, high compressibility and low permeability, making it a very problematic foundation material. A ground improvement program was undertaken to expedite approximately 90 percent of estimated primary consolidation settlement to meet the construction schedule. The ground improvement program consisted of using a maximum permitted surcharge near the operating runway and Prefabricated Vertical Drains (PVD). The settlement of both surcharged embankments was monitored using settlement plates. In addition, soil parameters were updated using ongoing measurements to revise the estimated final settlement and time required to achieve geotechnical stabilization. This case study discusses the parameters used for acceptable geotechnical stabilization, compares the estimated and actual magnitude and duration of settlement with and without ground improvement, and comments on conventionally used soil parameters for the Bay Mud.
Influence of Initial Stress/Strain State on the Coefficient of Earth Pressure at Rest
Authors: Eliadorani Ali Akbar  , Vaid Yoginder
Published: February 2025

An experimental technique for the K0, the coefficient of earth pressure at rest, is presented. The technique consists of drained vertical compression of a triaxial specimen using the strain path control, in which a positive control of the strain increments rather than the conventional stress increments is exercised. The method does not require the use of any lateral strain sensors as used in previous studies and is free from any side friction affects, typical of oedometer testing. A detailed series of tests on three (3) sands are presented to illustrate the capabilities of the proposed technique. Possible influence of stress/strain history the soil inevitably experiences during sampling or reconstitution together with the initial state of stress prior to initiating zero lateral strain loading on the measured K0 are critically reviewed and evaluated. It is shown that the requirement of absolute zero lateral strain may not be essential for obtaining credible estimates of K0 as long as the ratio of radial to axial strain during vertical compression does not exceed about 3 to 5 %.
Disk Transducer for stiffness measurement on granular materials
Authors: Suwal Laxmi P.  , Kuwano Reiko
Published: February 2025

Small-strain stiffness is one of the prominent characteristics of geo-materials on analysis of deformation behavior. Elastic wave measurement technique is becoming stronger non-destructive tool than other technique. In this paper, authors have focused on the application of the flat surfaced transducer ‘Disk transducer’, enabling to measure both compression and shear wave on triaxial specimen. Disk transducer was built the University of Tokyo using piezo- ceramic element and encapsulated in the top cap and pedestal of small scaled triaxial apparatus then performed the tests. This paper presents the results of three sorts of granular materials, fine, medium and coarse sand, were investigated statically and dynamically at isotropic and anisotropic stress states in the laboratory. The elastic parameters obtained on the granular materials; Young's modulus (E) and shear modulus (G), obtained by statically and by means of disk transducer method were examined and compared. It was observed, the statically and dynamically obtained results are mutually comparable and in agreement with previous studies. It is also confirmed the elastic parameters are to be a unique function of stress states with experimental evidence.
Experimental evaluation of liquefaction resistance of unsaturated sandy soils
Authors: Wang Hailong  , Koseki Junichi  , Sato Takeshi  , Tan Tian Jaylord
Published: February 2025

A series of undrained cyclic loading tests of three types of saturated and unsaturated soils were conducted on a triaxial apparatus. To overcome the difficulties of this type of test, cell pressure control system to maintain constant p, membrane filter technique to measure pore water pressure and double cell system to measure volumetric strain (ϵv) were introduced to the apparatus. Test results shown that the cell pressure control system reduced more than 60% variation of p which would be induced by applying vertical cyclic loading. The membrane filter technique could measure negative pore water pressure in a prompt manner and as a result suction of the unsaturated specimens was well monitored under the 0.1 Hz cyclic loading. The time delay problem of electric transducer employed in the ϵvmeasurement system, which may bring significant system error, was recognized and the measurement error of ϵvwas discussed. Regarding the resistance against liquefaction of the unsaturated soils, the test results shown increase in resistance with reduction in degree of saturation and the p-constant condition was necessary to correctly evaluate the resistance for the unsaturated soils.
Development of Stacked-Ring Shear Apparatus for Multiple Liquefactions Tests
Authors: Wahyudi Seto  , Takeshi Sato  , Koseki Junichi  , Aoyagi Yudai
Published: February 2025

Multiple liquefactions phenomenon gained much attention in the Geotechnical Engineering field after the 2011 Off the Pacific Coast of Tohoku Earthquake in Japan and Christchurch Earthquakes in New Zealand. It was found that not just liquefaction can appear twice, but also can appear multiple times at the same sites. In addition, the damage caused by the multiple liquefactions were often more severe than the damage caused by the single liquefaction. This issue raises great concern on the reoccurrence of liquefaction in the future great earthquakes.
In Situ and Laboratory Mechanical Characterization Using High-Resolution Fiber Optic Distributed Sensing
Authors: Klar Assaf  , Uchida Shun  , Levenberg Eyal
Published: February 2025

This paper explores the potential use of high-resolution fiber optic distributed sensing technology for in situ moduli profiling and in laboratory element testing. In recent times, strain measurement using fiber optics has been employed in innovative civil engineering applications such as in the health monitoring of ageing infrastructures. Through recent developments, in particular Rayleigh backscatter optical frequency domain reflectometry technique, the fiber optic sensing technology is nowadays capable of providing continuous distributed strain measurement with a higher spatial resolution of the order of millimeters. As a result, the technology can potentially serve as a viable alternative to conventional strain gauges (i.e. high-spatial resolution yet localized measurement devices) or seismic geophysical measurement (i.e. distributed yet low-spatial resolution). This paper provides two examples of its applicability to both in situ and laboratory mechanical characterization.
Influence of grading and mineralogy on the behaviour of saprolites
Authors: Rocchi Irene  , Todisco M. Cristina  , Coop Matthew R.
Published: February 2025

Soils originating from chemical decomposition do not undergo any sorting in their grading resulting in a well-graded material. Their composition may be influenced by weathering in one or more aspects, e.g. particle size, particle size distribution, mineralogy or particle morphology. Each of these aspects and their effects on the mechanical behaviour have been studied separately in the past. To identify the dominant parameters a series of standard oedometer tests was carried out to investigate the influences of the grading and mineralogy on the Normal Compression Line (NCL) separately. This was achieved taking the most and least decomposed granite sampled at a same location and reconstituting them to the same grading to study the influence of mineralogy or reconstituting one of them to both the gradings to study that of grading. In the first case, the NCLs were practically coincident, while in the second they were further apart, showing that the grading has greater importance in determining the mechanical behaviour in compression.
Influence of volumetric and shear strains on the destructuration of saprolitic soils
Authors: Rocchi Irene  , Coop Matthew R.
Published: February 2025

Based on a review of numerical models it would appear that debate is still open as to which combination of volumetric and shear strains is responsible for destructuration of intact soils. Direct experimental evidence is rather limited and mostly related to sedimentary clays. A saprolitic soil from Hong Kong that had been block sampled was tested to investigate the effects of sample disturbance and more in general of destructuration. The amount of destructuration was quantified by measuring the elastic shear stiffness by means of bender elements mounted axially in triaxial cells. The tests were designed to investigate separately the effects of volumetric and shear strains, by way of loading cycles reaching increasingly larger strains. The loading cycles were carried out under isotropic conditions and at constant mean effective stress for the volumetric and shear strains, respectively. In addition, the results obtained were compared with those from a test on a reconstituted specimen that was carried out in a similar fashion. In general, a reduction in shear stiffness was observed for the intact specimens, while a slight increase was measured for the reconstituted specimen at the same strain levels. The same held true also after normalising for void ratio, which was necessary as this changed as a result of straining hence having an effect on the shear stiffness. The reduction in stiffness observed for the intact specimens, which indicates loss of structure, was observed for both test types. However, at a given strain threshold, the reduction was larger for the specimen that underwent cycles of volumetric strains.
1D creep and delayed rebound during unloading and reloading of clay and its model simulation
Authors: Kawabe Shohei  , Tatsuoka Fumio
Published: February 2025

Most of the previous studies on the creep behaviour of soft clay focused on the one during otherwise primary loading under normally consolidated conditions associated with fill construction, pumping of ground water and so on. Despite strong geotechnical engineering needs, the study on the creep behaiour under general loading conditions including not only primary loading but also unloading and reloading has been very limited. In this study, a series of one-dimensional compression tests were performed along complicated loading histories and the creep strain during general loading history was studied. The test results are simulated successfully by an elasto-viscoplatic non-linear three-component model.
Creep and Stress Relaxation of Granular Materials Simulated by Non-linear Three-Component Model
Authors: Tatsuoka Fumio  , Duttine Antoine  , Salotti Alice  , Ezaoui Alan
Published: February 2025

Creep deformation and stress relaxation during otherwise monotonic loading drained direct shear (DS) at a fixed shear displacement rate of three types of clean sand and a gravel having different particle shapes and exhibiting different viscous property types are simulated by the non-linear three component model. Elastic body represents the hypo-elastic property, plastic body represents the plastic properties exhibiting a non-linear inviscid stress – irreversible strain relation and viscous body represents the viscous properties as a function of irreversible strain and its rate with or without control of loading history. It is shown that the trends of rate-dependent behavior observed in the DS tests, particularly creep and stress relaxation and their relationship, can be successfully simulated in the consistent manner by the non-linear three-component model.
Strain-Dependent Damping Ratio of Compacted Gravel
Authors: Liao Tianfei  , McHood Michael  , Massoudi Nasser  , Stokoe Kenneth H.  , Jung MinJae
Published: February 2025

Compacted gravel is often used as engineered fill to provide required bearing capacity for structures. The dynamic properties of the gravel fill, such as strain-dependent shear modulus and material damping ratio, are required in seismic analyses of these systems. Strain-dependent damping ratio as a function of cyclic shear strain were obtained from a series of combined Resonant Column and Torsional Shear (RCTS) tests on two types of crushed gravel fill. The material damping ratio curves are presented and compared to empirical relationships in the literature that have been proposed for gravelly soils.
Experimental assessment of the influence of load-induced deformation on interparticle contacts
Authors: Otsubo Masahide  , Sim Way Way  , O'Sullivan Catherine
Published: February 2025

A comprehensive understanding of soil response to applied loads and deformations requires an understanding of the particle-scale interactions. The overall stiffness can be related to the mean number of particle-particle contacts (mean coordination number, NC), the void ratio (e), the particle characteristics and the confining pressure. While most of these parameters can be measured, it is difficult to determine the mean coordination number directly from a laboratory test. The influence of the confining pressure on particle-particle contacts and therefore the e−NCrelationship is poorly understood. This paper presents experiments using ink to visualize particle contact points and to relate the mean coordination number to the void ratio (e−NCrelationship) under different vertical stresses.
A study of the micro-mechanics of sand particle breakage using a high-speed microscope camera
Authors: Wang Wanying  , Coop Matthew
Published: February 2025

Single particle uniaxial compression tests are widely used to study the micro-mechanical properties of particles. In recent years, much research studying the micro-mechanisms of sand particle breakage has been carried out using this method. However, the breakage mechanisms are still not well known, partly because of the rapid brittle failure of the particles. In this study, a high-speed camera was used in single particle uniaxial compression tests to capture the breakage process. The equipment enabled a maximum of about 2000 frames to be obtained per second, which could identify the crushing process in detail. In this paper, two modes of single particle breakage are proposed for Leighton Buzzard sand. Firstly splitting caused by cracks slowly propagating from one contact surface to the opposite one and secondly catastrophic explosion associated with very rapid crack propagation from the interior of the particle outwards. Single particles immersed in water were also compressed uniaxially to find if the breakage mode and characteristic strength would be affected by water. Immersion in water reduced the compression strength slightly and affected the single particle crushing mode.
Behavioural features of fissured clays: experimental evidence and modelling
Authors: Cotecchia Federica  , Vitone Claudia
Published: February 2025

Fissured clays are widespread all over the world and they are often catalysts of several and unexpected in-situ problems. In the last decade, a research started at the Technical University of Bari aiming to interpret the influence of fissuring on the clay behaviour. According to the approach adopted, a Fissuring IDentity (F-ID) has been associated to each clay being studied, as extracted from a general fissuring characterisation chart. Hence, the analysis of the fissured clay behaviour has benefited from systematically coupling the micro- to meso- features (i.e., F-ID charts) and processes, and the observations of the macro-response. The comprehensive experimental programme carried out on several Italian fissured clays has allowed to recognise that they can be still modelled as single geotechnical class which follows an extended sensitivity framework of behaviour. Moreover, for clays of specific F-IDs, most recent developments of the research have put in evidence discrepant behavioural facets induced by scale effects.
Selection of Design Friction Angle Based on Soil and Project Characteristics
Authors: Sancak Emirhan  , Cinicioglu Ozer
Published: February 2025

The aim of this study is to develop a method that would aid design engineers in the selection of project based design friction angles for cohesionless soils. In this context, design friction angle is defined as either one of peak or critical state friction angles. In line with this objective, shear strain at which peak friction angle is mobilized, is quantified as a function of soil properties. Then, it is necessary to relate allowable structural deformations to magnitudes of possible shear strains through numerical modelling and make an assessment on which friction angle to be used for the design involved. To develop this approach, data from triaxial compression tests under drained conditions conducted on 8 different sands are investigated. These data were used to construct relationships between peak dilatancy angle and shear strain at which these peak dilatancy angles are measured. Obtained relationships are combined with a novel equation that relates dilatancy angle to soil's state. Then the results were evaluated using the results from 1 g small scale retaining wall model tests that were conducted on a completely different sand.
Laboratory test and numerical study of cyclic behavior of unsaturated liquefiable sandy soil
Authors: Matsumaru Takaki  , Uzuoka Ryosuke  , Kiguchi Mineo  , Nishimura Tomoyoshi
Published: February 2025

To investigate the cyclic behavior of unsaturated soil, a series of cyclic triaxial tests and numerical simulations were performed. The tests results indicated that the liquefaction would occur if the suction value before cyclic loading was small. This tendency was well reproduced by the numerical simulations using the conventional elasto-plastic constitutive model proposed for unsaturated soil.
Understanding the Disintegration of Sensitive Clays using Remolding Energy
Authors: Thakur Vikas  , Degago Samson Abate
Published: February 2025

Sensitive clay materials are found in several areas of the world including Alaska, Canada, Norway and Sweden. Studies by various researchers suggest that a knowledge about the complete stress-strain curves help in the assessment of the flow slide potential of sensitive clays. The post-peak stress-stain behaviour of sensitive clays particularly indicates the disintegration process in the material as well as helps in the estimation of the energy involved in the disintegration process. The energy concept is a subject of current study by several researchers working on investigation of flow slides on sensitive clays. Several terms such as degradation energy, strain energy or remolding energy have been used to indicate the energy available for disintegration of sensitive clays; this is referred to as remolding energy (RE) in this work and is simply defined as the strain energy involved in the disintegration or remolding of a material. A closer examination of the concept of RE provides an understanding of the overall mechanical behavior of sensitive clays during flow slides. In this paper, concept of RE analytically proposed by the authors is elaborated in light of laboratory tests conducted to determine RE of sensitive clays.
Rockfill Mechanics. Experimental Observations and DEM Modelling
Authors: Alonso E.E.  , Tapias M.
Published: February 2025

Particle breakage explains the specific features of rockfill behaviour. Relevant features concern the dilatant behaviour under increasing confining stress, the long term deformations (creep) and the response under changes in relative humidity (RH). RH effects on deformation are well known in practice and result in marked collapse behaviour of rockfill structures as a consequence of full or partial saturation. The lecture will first present an ordered set of experimental results. The following aspects will be introduced: Suction effects on compressibility and yielding of compacted gravel specimens of different nature and grain size distribution, delayed creep deformations under isotropic conditions, deviatoric behaviour, dilatancy and the evolution of grain size distribution. These results sets the ground for the presentation and discussion of a Distinct Element model developed in an attempt to create a “numerical” laboratory capable of predicting real behaviour. The model includes particle shapes which reproduce, in a reasonable manner, the irregular shape of real rock fragments. Particle breakage is introduced as a fundamental deformation mechanism. Unlike other approximations reported in the literature, particle breakage was approached from the perspective offered by fracture mechanics. Particle breakage is the consequence of the propagation of pre-existing cracks. Crack propagation velocity of each individual particle is approximated by means of analytical solutions. Delayed deformations are a natural consequence of the model and the effect of RH can also be introduced in a simple manner. The process of parameter determination will be discussed with specific reference to large diameter oedometer and triaxial tests.
Evaluation of Heterogeneities in Reconstituted Samples using X-Ray tomography
Authors: Leguizamón Barreto Luis Carlos  , Flórez Valencia Leonardo  , Ramos Cañón Alfonso  , Prada Sarmiento Luis Felipe  , Tique Alviar Daniel Oswaldo
Published: February 2025

In the process of characterization and modeling of the mechanical behavior of geomaterials assumptions are adopted related to the theory of continuous medium, such as homogeneity and isotropy condition derived from the stress-strain response. Thus the development of element tests on undisturbed samples or reconstituted in laboratory the actual evaluation of discretization and heterogeneity of the environment are not considered, and their impact on the response of shear strength, this fact extends to the numerical implementation of different constitutive models through the application of finite element methods and discrete elements. Among the methods for the reconstitution of sand samples in a laboratory we have compaction, pluviation and moist tamping to determine the density levels achieved in the manufacture of loose or dense homogeneous samples. These samples are used in stregth tests such as the triaxial resistance without taking into account the definition of an indicator to establish the real state of heterogeneity of the same. The progress of prospecting techniques in medicine such as X-ray computed tomography has transcended to other fields such as the quality assessment of materials engineering. A proposal for assessing the condition of heterogeneity of sand samples considering the main building techniques shown in this paper, based on the development of tomographic images and the subsequent treatment of the Hounsfield [HU] information density readings with the initial application of image segmentation techniques that allows to obtain baseline data points and the subsequent statistical analysis of variability considering different volumetric groupings. So a reconstitution evaluation measure is reached of soil samples that could be generalized to the analysis of undisturbed samples, allowing analysis of relationship structure - mechanical response characterization tests and shear strength. The results of this study show a high influence of the boundary conditions in the heterogeneous spatial distribution of the density in reconstituted samples with the methods considered, also allows to think about the use of this methodology as a tool for reviewing and adjusting of such methods and its application to the study of undisturbed samples.
Cyclic behavior of an over-consolidated remoulded clay
Authors: Dano Christophe  , Han Jian  , Hicher Pierre-Yves
Published: February 2025

The cyclic behavior of highly over-consolidated stiff clays has not been examined so much in the literature. Here, we experimentally studied the behavior of a remoulded clay submitted to cyclic loadings. The remoulded samples were prepared from natural specimens retrieved in the north of France. First, the shear strength characteristics along monotonic triaxial stress paths were identified. Then load control cyclic tests were conducted in fully saturated and undrained conditions. Small cyclic deviatoric stresses were applied in order to investigate more particularly the behavior under a very large number of cycles (more than one million). It was shown than even after 106cycles, failure did not necessarily occurred in most of the samples unless the cyclic stress level was greater than a critical value. Moreover, for those over-consolidated samples, an unusual pore pressure evolution, compared to normally consolidated specimens, was observed. Additional creep tests showed that two processes were simultaneously acting in a competitive manner: increase of the pore pressure due to the cyclic loading, decrease of the pore pressure because of creep.
Creep in clay during the first few years after construction
Authors: Grimstad Gustav  , Mehli Magne  , Degago Samson Abate
Published: February 2025

Currently there exist different assumptions and approaches, along with various parameter interpretation procedures, that are used in the deformation and consolidation analysis of soils. In this article the importance of correct implementation of creep formulation in settlement analysis, during the first few years after construction, is discussed. The significance of using an objective interpretation of secondary compression index is also illustrated. The Onsøy test fill, which was monitored for a three year period after construction, is used as an example. Measurements include vertical and horizontal settlement along with pore pressure profiles. The Onsøy test fill is of particular interest because of the availability of good quality tests on block sampled Onsøy clay along with well-documented field measurements. The analyses show that disregarding creep in the first 3 years period can underestimate the settlement by as much as 70% or more, when the block samples are used as a basis for the interpretation of soil parameters.
Comparison of two sample quality assessment methods applied to oedometer test results
Authors: Amundsen Helene Alexandra  , Thakur Vikas  , Emdal Arnfinn
Published: February 2025

The issue of sample quality is important in regards to determining reliable and representative soil parameters for fine-grained soils. In the literature, there exist several assessment criteria that can be used to assign a degree of confidence to laboratory parameters, such as the strength and stiffness. In this paper, two commonly used methods for assessment of oedometer tests are compared in light of laboratory results for a low plastic Norwegian sensitive clay. The results show that the conclusions drawn from these two methods differ significantly from each other. Possible reasons for discrepancies between the methods of the sample quality assessment are discussed.
Physical Protection Systems (PPS) for Nuclear Facilities
Authors: Majeed Tareq
Published: February 2025

In this article, a very brief description of the importance of physical protection systems for nuclear facilities will be discussed. Asystematic and measurable approach to the implementation of a PPS will be described in a comprehensive manner. For this purpose, the design objectives of PPS will be discussed. Various deterrence measures will be described with the caution or not to depend on deterrence measures for protection of assets and must be supplemented by detection. It will also briefly introduce the main PPS functions, detection, delay and response along with the relationship of these functions. It will emphasize the function of detection, followed by delay and response. Specific performance measures of various functions of a PPS will be described, along with how these measures are combined to support a cost–benefit analysis. The process stresses the use of integrated systems combining people, procedures, and equipment to meet protection objectives.
Hybrid Parallelization of Hyper-Dimensional Vlasov Code with OpenMP Loop Collapse Directive
Authors: Umeda Takayuki  , Fukazawa Keiichiro
Published: February 2025

Space plasma is a collisionless, multi-scale, and highly nonlinear medium. Computer simulations with the first-principle kinetic equation are essential for space plasma studies. In the present study, a hyper-dimensional Vlasov (collisionless Boltzmann) simulation code, which is a first-principle method for collisionless space plasma, is parallelized with two-level hybrid MPI and OpenMP and is benchmarked on massively-parallel supercomputer systems. The benchmark result shows that the loop “collapse” directive option of the OpenMP reduces threading overhead of multiple loops. It is also shown that the hybrid parallelism with MPI and OpenMP is useful to reduce the communication time of MPI collective communication subroutines.
Efficient Parallel Linked List Processing
Authors: Tousimojarad Ashkan  , Vanderbauwhede Wim
Published: February 2025

OpenMP is a very popular and successful parallel programming API, but efficient parallel traversal of a list (of possibly unknown size) of items linked by pointers is a challenging task: solving the problem with OpenMP worksharing constructs requires either transforming the list into an array for the traversal or for all threads to traverse each of the elements and compete to execute them. Both techniques are inefficient. OpenMP 3.0 allows to addresses the problem using pointer chasing by a master thread and creating a task for each element of the list. These tasks can be processed by any thread in the team. In this study, we propose a more efficient cutoff-based linked list traversal using our task-based parallel programming model, GPRM. We compare the performance of this technique in both GPRM and OpenMP implementations with the conventional OpenMP implementation, which we call Task-Per-Element (TPE).
Pipeline Template for Streaming Applications on Heterogeneous Chips
Authors: Rodríguez Andrés  , Navarro Angeles  , Asenjo Rafael  , Corbera Francisco  , Vilches Antonio  , Garzarán María
Published: February 2025

We address the problem of providing support for executing single streaming applications implemented as a pipeline of stages that run on heterogeneous chips comprised of several cores and one on-chip GPU. In this paper, we mainly focus on the API that allows the user to specify the type of parallelism exploited by each pipeline stage running on the multicore CPU, the mapping of the pipeline stages to the devices (GPU or CPU), and the number of active threads. We use a real streaming application as a case of study to illustrate the experimental results that can be obtained with this API. With this example, we evaluate how the different parameter values affect the performance and energy efficiency of a heterogenous on-chip processor (Exynos 5 Octa) that has three different computational cores: a GPU, an ARM Cortex-A15 quad-core, and an ARM Cortex-A7 quad-core.
Efficient and scalable distributed-memory hierarchization algorithms for the sparse grid combination technique
Authors: Heene Mario  , Pflüger Dirk
Published: February 2025

Finding solutions to higher dimensional problems, such as the simulation of plasma turbulence in a fusion device as described by the five-dimensional gyrokinetic equations, is a grand challenge facing current and future high performance computing (HPC). The sparse grid combination technique is a promising approach to the solution of these problems on large scale distributed memory systems. The combination technique numerically decomposes a single large problem into multiple moderately sized partial problems that can be computed in parallel, independently and asynchronously of each other. The ability to efficiently combine the individual partial solutions to a common sparse grid solution is a key consideration to the overall performance of large scale computations with the combination technique. This requires a transfer of each partial solution from the nodal basis representation into the hierarchical basis representation by hierarchization. In this work we will present a new, efficient and scalable algorithm for the hierarchization of partial solutions that are distributed over multiple process groups of an HPC system.
High Performance Eigenvalue Solver in Exact-diagonalization Method for Hubbard Model on CUDA GPU
Authors: Yamada Susumu  , Imamura Toshiyuki  , Machida Masahiko
Published: February 2025

The graphics processing unit (GPU) is an excellent accelerator and it can realize speedup with appropriate tuning. In this paper, we present a tuning technique for the exact diagonalization method, which is widely used as a numerical tool to obtain the ground state (the smallest eigenvalue and the corresponding eigenvector) of the Hamiltonian derived from the Hubbard model, on the GPU architecture. Since the Hamiltonian is a sparse matrix, an iteration method is used for solving the eigenvalue problems. We mainly tune the code for the multiplication of the Hamiltonian and a vector, which is the most time-consuming operation in the iteration method. The numerical test shows that the tuned code is faster than the one with using the routine “cusparseDcsrmm” of cuSPARSE library. Moreover, the tuned method on NVIDIA Tesla M2075 achieves about 3× speedup as compared with the thread-parallelized code on six threads of Intel Xeon 5650 for the multiplication.
Simulation of external aerodynamics of the DrivAer model with the LBM on GPGPUs
Authors: Pasquali Andrea  , Schönherr Martin  , Geier Martin  , Krafczyk Manfred
Published: February 2025

We studied the external aerodynamics of a car employing CFD numerical simulations with the cumulant LBM on GPUs. We performed the analysis for different grid resolutions and for single- and multi-GPU simulations. In order to evaluate the performance of our implementation, we also carried out numerical simulations with the FVM on a CPU cluster using OpenFOAM®. The results showed a good agreement to experimental data and the cumulant LBM computation was substantially faster than the FVM. The cumulant LBM multi-GPU implementation demonstrated also high parallel efficiency. Our work shows that the cumulant LBM on GPU is a valid alternative to FVM on CPUs to perform accurate and efficient CFD simulations of complex engineering problems.
CPU performance analysis using Score-P on PRIMEHPC FX100 Supercomputer
Authors: Nakamura Tomotake
Published: February 2025

Performance tuning tools are required to reach a high level of performance in a large-scale parallel system. There are many open source software (OSS) tools that can assist programmers with the performance analysis. Score-P is an efficient OSS tool for analyzing MPI communication and tuning performance. A problem is that it only uses hardware counters to analyze CPU operating states. We developed an interface between Score-P and Fujitsu's advanced profiler (FAPP), which has more functions for analyzing CPU operating states. The key benefit of our interface is that users can find the cost balance among threads in a CPU and investigate the causes of the performance problem by using there individual favorite performance tool. We demonstrated this interface's ability in tuning the CCS quantum chromodynamics (QCD) benchmark program.
How to Keep a Geographic Map Up-To-Date
Authors: Grebe Marco  , Lacko Tilman  , Loogen Rita
Published: February 2025

Nowadays, data for digital maps are collected using a small fleet of specialised expensive vehicles. This approach is not sufficient for daily updates of all roads. Daily or even faster updates, needed for modern driver assistance systems, can be made by combining the, individually less accurate, sensor data of standard cars. In this paper we propose a framework which comprises a parallel system to apply use case specific iterative algorithms to incoming data. Fast adaptation to changed situations is achieved by using a graph structure for representing sequences of groups of detected objects. A case study on maintaining a map of traffic signs has been performed to prove the capabilities of the framework.
Static and Dynamic Big Data Partitioning on Apache Spark
Authors: Bertolucci Massimiliano  , Carlini Emanuele  , Dazzi Patrizio  , Lulli Alessandro  , Ricci Laura
Published: February 2025

Many of today's large datasets are organized as a graph. Due to their size it is often infeasible to process these graphs using a single machine. Therefore, many software frameworks and tools have been proposed to process graph on top of distributed infrastructures. This software is often bundled with generic data decomposition strategies that are not optimised for specific algorithms. In this paper we study how a specific data partitioning strategy affects the performances of graph algorithms executing on Apache Spark. To this end, we implemented different graph algorithms and we compared their performances using a naive partitioning solution against more elaborate strategies, both static and dynamic.
FPGAs as Components in Heterogeneous High-Performance Computing Systems: Raising the Abstraction Level
Authors: Vanderbauwhede Wim  , Nabi Syed Waqar
Published: February 2025

We present an overview of the evolution of programming techniques for Field-Programmable Gate Arrays (FPGAs), with a particular focus on High-Level Synthesis (HLS) and Heterogeneous Computing (HC), and we argue that, in the context of High-Performance Computing (HPC), FPGAs should be treated as components of a larger heterogeneous compute platform. Consequently, HLS and HC tools become compilation targets rather than high-level development tools. Compiler technology has to evolve to automatically create the best compiled program variant by transforming a given original program. We describe our methodology based on type transformations and cost models, which allows to automatically generate correct-by-construction program variants and accurately estimate their performance, so that an optimal program can be constructed by the compilation system.
Leveraging FPGA clusters for SAT computations
Authors: Kouril Michal
Published: February 2025

Field Programmable Gate Arrays (FPGAs) can be an important computational tool for increasing the efficiency of SAT solvers. We have developed an efficient SAT solver for computing van der Waerden numbers using a cluster of over 200 Xilinx Spartan XC6SLX150 FPGAs that were originally dedicated to Bitcoin mining. This cluster should compute W(5,3) in 6–9 months with modest power and cooling requirements. We discuss the challenges of building and operating this computational system. Finally, we report the values of four new off-diagonal van der Waerden numbers.
On Efficient Time Stepping using the Discontinuous Galerkin Method for Numerical Weather Prediction
Authors: Dedner Andreas  , Klöfkorn Robert
Published: February 2025

We present a preconditioned matrix-free Newton Krylov method for solving meteorological problems with an implicit Runge-Kutta Discontinuous Galerkin scheme. First we report on an explicit version of the scheme, briefly studying serial and parallel efficiency of our code and present a comparison of our scheme with the dynamical core COSMO developed at the German Weather Service. On isotropic grids our code is shown to be competitive, while on grids with smaller spacing in the vertical than horizontal, the stability restrictions on the time step make this approach unsuitable. We then present new work on an implicit version which is shown to bring the run time back within the range of COSMO on the anisotropic grids more normally used in numerical weather prediction.