bluuebunny/crossref_metadata_2025 huggingface dataset:
Modelling drag anchors in a drum centrifuge
Authors: O’Neill Michael , Randolph Mark
Published: November 2015

The design of large offshore drag anchors remains relatively primitive, relying on design charts that cover broad categories of soil type, and with no direct link to specific shear strength profiles at a given site. Physical modeling offers one way to improve the design framework, and the drum centrifuge, offering essentially unlimited drag distance, has obvious advantages. This paper describes a series of scale model drag anchor tests performed in the drum centrifuge at The University of Western Australia (UWA) in a soil sample comprising normally consolidated clay. A special loading arm was developed in order to circumvent problems in modelling the anchor chain in the curved g environment of the drum. Measurements of the vertical and horizontal components of load at the anchor pad-eye during installation allowed validation of the Neubecker-Randolph analytical approach for drag anchor embedment and holding capacity. The two design parameters needed for this approach were evaluated for model Vryhof Stevpris anchors in soft clay, and the resulting anchor performance was shown to be consistent with published design charts.
Compaction control of clay barriers by centrifugation
Authors: Mitchell R.J. , Knight M.A.
Published: November 2015

Although field compaction techniques and specifications for achieving a homogeneous clay barrier are well known, changes in borrow materials due to weathering or stratifications can lead to variability in the performance of such compacted barriers. Field density testing can give an indication of barrier quality but quality control should also incorporate hydraulic conductivity testing. Hydraulic conductivity testing on a daily basis is a difficult task. This paper outlines a methodology for barrier control testing by centrifugation and discusses why centrifuge testing is superior to bench testing with elevated gradients. The use of centrifugation for evaluating barrier diffusion and possible long-term change in hydraulic conductivity is also discussed.
Performance of piled raft foundations subjected to dynamic loading
Authors: Horikoshi Kenichi , Matsumoto Tatsunori , Hashizume Yoshinori , Watanabe Toru
Published: November 2015

A series of shaking table tests were conducted on piled raft foundations on sand by using a geotechnical centrifuge. The results were compared with those obtained from the static horizontal loading tests of the same models which have been reported by Horikoshi et al. (2003). Effects of the rigidity at pile head connection on the dynamic behavior were examined. Also shown are the results of the dynamic loading test of a free-standing pile group with the same number of piles to examine the contribution of the load transferred through the raft base.

Principal findings from the present study are: 1) The horizontal load-displacement relationships and the bending moment distributions agree well between the dynamic models and the static models. The proportion of the horizontal load carried by each component is highly dependent on the horizontal displacement of the piled raft system; 2) The horizontal stiffness of the piled raft with the hinged pile head connection was smaller than that of the piled raft with the rigid pile head connection; 3) The proportion of the vertical load carried by the piles remains largely unchanged during dynamic loading, while the proportion of horizontal load carried by the piles increases as the horizontal displacement increases; 4) The inclination of the piled raft during shaking is much smaller than that of the pile group due to the contribution of the soil resistance just beneath the raft.
Experimental and analytical study on behaviour of model piled rafts in sand subjected to horizontal and moment loading
Authors: Matsumoto Tatsunori , Fukumura Kazuyuki , Pastsakorn Kitiyodom , Horikoshi Kenichi , Oki Asuka
Published: November 2015

A series of static horizontal load tests were carried out on model piled rafts at 1-g gravitational field by using dry Toyoura sand. In order to examine the effects of confined stress on soil modulus and confirm the similitude for the present 1-g models, triaxial consolidated drained shear tests of the sand were conducted. Two experimental variables were considered, i.e. the height of the acting force, and the rigidity of the pile head connection. Also presented in this paper are the results of the simplified three-dimensional deformation analyses of the model tests, which shows the reasonable agreement with the experimental results in the initial elastic region. From the model tests and the analyses, it is shown that horizontal displacement and inclination of the raft, and bending moments of piles for a given horizontal load are increased as the height of horizontal loading point (i.e. moment load) is increased. It is also shown that horizontal displacement and inclination of the raft and bending moments of piles are reduced in the piled raft with hinged pile head connection compared to the piled raft with rigid pile head connection when subjected to horizontal load and the associated moment load.
The use of fly ash to alter the engineering properties of artificial “model” clay
Authors: Wartman Joseph , Riemer Michael F.
Published: November 2015

This article describes a procedure using fly ash to alter, for similitude purposes, the geotechnical engineering properties of artificial clay used in shaking table physical model studies. The fly ash used in this study acted as a chemically reactive material when mixed with an artificial kaolinite-bentonite model clay. When added to the model clay, the fly ash stiffened the soil (increased shear wave velocity) while lowering the soil’s undrained shear strength. To avoid increasing the strength of the model soil, the fly ash-clay mixture had to be thoroughly remolded at least several days after initial mixing. The article discusses an application of this model soil preparation procedure for a 1-g shaking table study of seismic soil-pile-superstructure interaction in a soft marine clay.
The behaviour of circular footings on sand subjected to combined vertical-torsion loading
Authors: Cassidy M.J. , Cheong J.
Published: November 2015

The drained behaviour of rigid circular footings when subjected to combined vertical and torsion loading on dense silica sand is described. An experimental programme has been developed to allow the interpretation of the results within strain-hardening plasticity theory. Emphasis is placed on investigating and establishing the size and shape of the combined vertical-torsion yield surface through the use of pure vertical-loading and vertical-torsion swipe tests. This allowed extension of an existing strain-hardening model for combined loading in three-degrees of freedom (vertical, moment and horizontal) to six-degrees of freedom (vertical, orthogonal moment and horizontal, and torsion). This modified extension is described and retrospective numerical simulation of a number of experimental tests outlined.
Centrifugal modelling of subway-induced vibration
Authors: Tsuno Kiwamu , Morimoto Wataru , Itoh Kazuya , Murata Osamu , Kusakabe Osamu
Published: November 2015

In a congested urban situation between subway lines and facilities requiring noise and vibration free conditions, it is necessary to estimate the propagated subway-induced vibration. The attenuation characteristics of subway-induced vibration in the ground may not be fully understood because of a number of influencing factors, and it is appropriate to investigate the attenuation under a clear ground condition with known boundary conditions. This paper describes the development of a centrifugal model test system, simulating the subway-induced vibration, experimental results, including contour of vibration acceleration level and comparisons between experimental observations and field measurements. It was found that the attenuation of subway-induced vibration in the ground becomes larger as frequency becomes higher. Bomitz’s formula is applied to estimate the attenuation and it was found that the values of material damping coefficient α are almost the same in the acceleration level of 15 to 62 g, which are consistent with those obtained by field measurements at 14 sites in and around the Tokyo area.
Role of input motion in excess pore pressure generation in dynamic centrifuge modelling
Authors: Madabhushi S.P.G. , Ghosh B. , Kutter B.L.
Published: November 2015

Dynamic centrifuge testing is widely used to model geotechnical earthquake engineering problems. This is especially helpful in generating data to validate numerical models or to understand failure mechanisms in a given boundary value problem. The input motions used in many of these tests to simulate the earthquake loading vary from simple sinusoidal motions at a single frequency to more realistic earthquake motions recorded in previous earthquakes. These realistic earthquakes normally contain different amplitude cycles as well as different frequency components. This paper investigates the effect of choice of input motion on the behaviour of loose, saturated soil layers in terms of excess pore pressure generation and settlement. It presents results from centrifuge tests carried out using specially designed input motions that are comparable, with either uniform or non-uniform amplitude cycles. It will be shown that both these types of motions resulted in very similar peak excess pore pressures. However non-uniform amplitude cycles resulted in large, dilation induced suction spikes that can have an effect on accumulated soil deformation. It is concluded that choice of input motion may depend on the type of problem being investigated and the purpose of centrifuge testing.
Twenty nine years of experience with physical modelling of geotechnical problems in port structures
Authors: Kitazume Masaki
Published: November 2015

At present, centrifuge model testing has become an important tool for investigation of complex geotechnical natures. In 1980, the Port and Harbour Research Institute (PHRI) constructed the Mark I geotechnical centrifuge, whose effective radius was 3.8 m. Since then, the PHRI carried out many tests on fundamental and practical research projects. Unfortunately, since 1989, undesirable vibrations of the concrete pit floor had frequently occurred during the operation of the Mark I centrifuge. Therefore the maximum operative acceleration had to be limited below 50 g for safety reason, which in fact led to serious limitations to research projects to be studied. Consequently, the PHRI had decided to construct a new centrifuge, namely the Mark II. Based on the statistical studies on the actual operation, the major dimensions and capacities of the new centrifuge was decided to be the same as the Mark I. In 1989, the PHRI had started the construction and completed in 1994. In 2001, the PHRI became an independent administrative institution in the administrative reorganization of Japanese Government, and the name of the institute was changed to the Port and Airport Research Institute (PARI). The PHRI and the PARI have conducted more than 1,300 centrifuge operations on various research subjects mainly regarding to ground improvements. Some of them were related to fundamental research topics, while the research subject also included practical research projects associated with specific prototypes. The test results have been applied and reflected to the constructions of various port, harbor and airport facilities in Japan and overseas. This report briefly reviews the summary of the Mark I and the Mark II geotechnical centrifuge facilities and the centrifuge operations experienced in 29 years. Some research subjects studied so far are reviewed to demonstrate usefulness of this modelling technique and the ability of the centrifuge facilities.
Drying of calcium-silicate-hydrates: regeneration of elastic modulus
Authors: Pourbeik P. , Beaudoin J. J. , Alizadeh R. , Raki L.
Published: November 2015

Dynamic mechanical thermal analysis (DMTA) measurements for layered calcium silicate systems (1·4 nm tobermorite, jennite, synthetic calcium-silicate-hydrate and hydrated Portland cement paste) are reported. Elastic modulus results were obtained for samples initially conditioned to 11% relative humidity (RH) and dried during the DMTA test and for samples subjected to prolonged vacuum and thermal drying prior to a DMTA test. Decreases in elastic modulus relative to the 11% RH starting condition typically observed during a DMTA test were recovered subsequent to the prolonged thermal treatment. A possible ‘regeneration' mechanism for the elastic modulus is discussed. The ‘regeneration' occurs for all the calcium silicate systems studied. The results are consistent with the notions expressed for nanostructural models of calcium-silicate-hydrate in cement paste that comprise structural units based on 1·4 nm tobermorite and jennite.
Raman spectroscopy of the dehydration process of gypsums
Authors: Liu Fengjuan , Sun Zhihui , Qi Chengqing
Published: November 2015

In the present research, dehydration mechanisms of gypsums from different sources and grades are studied by Raman spectroscopy. Two temperature profiles, one aggressive and another at moderate temperatures, are used. It is found that Terra Alba gypsum dehydrates to form hemihydrate (CaSO4·0·5H2O) and an interstitial gypsum phase at 128°C. The interstitial phase formed contains less water than hemihydrate. Anhydrite (CaSO4) is produced at a temperature of 140°C or higher. The commercial rock gypsum studied generates both hemihydrate and anhydrite at 128°C, and its impurities do not dehydrate until the temperature is increased to 500°C. The dehydration process of a synthetic gypsum indicates that it has an interstitial gypsum phase dehydrating in a similar way to the interstitial phase found in the Terra Alba gypsum. For all these gypsums, anhydrite is the only dehydration product at 500°C. These findings are further confirmed by X-ray diffraction and thermogravimetric analyses.
On the hydration process of the slag–anhydrite–lime system: a discussion on the stoichiometry of hydrates and the development of strength
Authors: Iyoda Takeshi , Asaga Kiyoshi , Goto Seishi
Published: November 2015

To better understand the hydration of slag, various combinations of slag–anhydrite–lime were investigated, mainly by conduction calorimeter. Compressive and bending strength were also measured. The following conclusions were obtained: in the case of existing calcium hydroxide (Ca(OH)2), hydration products were calcium–silicate–hydrate (C–S–H) and aluminium-rich (Al, Si, Ca)OH gel. C–S–H had a calcium/silicate ratio of 1·4 and the aluminium-rich (Al, Si, Ca)OH gel was located on the surface of unreacted slag particles to hinder the hydration of slag. A mixture of slag and anhydrite (without lime) reacted to produce C–S–H and ettringite, but the initiation time of reaction was very long – as much as 400 h. In this case, the calcium oxide/silica (CaO/SiO2) ratio of the calcium-silicate-hydrate was considered as low as 0·6 to 0·8. Monosulfate (AFm(SO4)) was not produced from slag hydration, as the solubility of slag is lower than that of monosulfate. The compressive strength of mortar without gypsum was 25 N/mm2 at 91 d, whereas that containing gypsum of 15% by mass was 70–80 N/mm2 at 91 d. In the case of 2% calcium hydroxide, the compressive strengths with gypsum were all less than 15 N/mm2 at 91 d and they were lower than that without gypsum of 25 N/mm2 at 91 d. Reducing the addition of calcium hydroxide was very effective for mortar strength with gypsum but addition in excess of 2% retarded the hydration. The strength of mortar without formation of ettringite (slag–lime system) had lower bending/compressive strength ratio.
Thermodynamic of incongruent solubility of C–S–H
Authors: Dangla Patrick , Thiery Mickael , Morandeau Antoine
Published: November 2015

In most situations, the pore solution of cement-based materials is in thermodynamic equilibrium with the calcium silicate hydrates resulting from the hydration of (tri–di)calcium silicates. This equilibrium is, however, difficult to characterise, the solution phase being incongruent with respect to the calcium silicate hydrate phase. A thermodynamic description of this equilibrium is proposed and some new relationships are derived involving the saturation indexes of dissolved pure substances and the calcium/silicon ratio of the calcium silicate hydrate. These relationships can be understood as a generalisation of the law of mass action for incongruent chemical reactions. The validity of these relationships was checked using measurements reported in the literature.
Vibration attenuation performance of long-eared owl plumage
Authors: Gao Jiali , Chu Jinkui , Shang Haixin , Guan Le
Published: November 2015

A comparative study of vibration attenuation behaviour of primary remex with lateral branches from the long-eared owl (a silent flying bird), golden eagle and pigeon (two noisy flying birds) was conducted in order to investigate the damping ability of owl’s primary remex. Amplitude variation of the measurement points on the rachis with vane structures was measured by a laser displacement sensor, and vibration process of the observation point on the barb with lateral barbules was recorded by a high-speed camera. Amplitude–time analysis results indicate that loss factors of long-eared owl’s complete primary feathers and barbs are higher than those of the golden eagle and pigeon feathers. Thus, vibration amplitudes of the long-eared owl feathers and their barbs decay much faster, showing a superior vibration-damping characteristic. Consequently, mechanical noise caused by the relative motion of the owl primary feather structures during flight may be effectively suppressed. Vibration reduction principle of the long-eared owl primary feather was briefly discussed based on the damping-by-branching mechanism at last.
Hydrogen sulfide removal by bacteria from upflow anaerobic sludge blanket
Authors: Doungprasopsuk Walailuk , Suwanvitaya Patcharaporn
Published: November 2015

This study investigated the biological removal of hydrogen sulfide (H2S) from biogas by anaerobic wastewater treatment processes. Heterotrophic and autotrophic bacteria were isolated from upflow anaerobic sludge blanket (UASB)-mixed liquor of fruit processing factory using nutrient broth and thiosulfate mineral salt medium, respectively. Hydrogen sulfide-removal activities were investigated using sterile UASB-mixed liquor and hydrogen sulfide as growth substrates. It was found that the growth rate of autotrophic bacteria (319 mg VSS l−1 day−1) was higher than that of the heterotrophic bacteria (267 mg VSS l−1 day−1). Hydrogen sulfide(g) was totally removed by absorption into liquid phase: 78·24% removal of aqueous sulfide (S2−(aq)) was achieved by autotrophs and 68·03% by heterotrophs. Molecular identification by polymerase chain reaction-denaturing gradient gel electrophoresis technique and DNA sequencing showed that heterotrophic consortium consisted of Pseudomonas fluorescens Pf0-1, P. aeruginosa PAO1, P. putida KT2440, Bacillus megaterium DSM319 and B. cereus ATCC14579. Autotrophic consortium consisted of Thiobacillus thioparus NZ, T. denitrificans ATCC25259 and Halothiobacillus neapolitanus c2.
Briefing: Engineering skills shortages in China—a personal view
Authors: Mills Geoff
Published: November 2015

Two challenges from history illustrate how to mobilise an industry to face a major challenge: the engineering infrastructure for the Normandy landings and the establishment of the UK’s motorway network. China has already applied the lessons learned from these challenges to undergraduate education, but the focus is now moving to professional development. A group of leading firms, academics and ICE are cooperating to tackle this problem. This is a small step on an arduous journey but to those who judge Chinese engineers only by where they are today and not where they have come from it would be worth remembering the following Zhuang Zi quotation from the 5th century BC. ‘When Heaven is about to place a great responsibility on a man, it always first frustrates his spirit and will, exhausts his muscles and bones, exposes him to starvation and poverty, harasses him by troubles and setbacks so as to stimulate his spirit, toughen his nature and enhance his abilities.’
GPS measurements on the London Millennium Bridge
Authors: Roberts Gethin W. , Meng Xiaolin , Brown Christopher J. , Dallard Pat
Published: November 2015

Trials conducted on the London Millennium Footbridge in 2000 monitored movements using three GPS receivers. After initial processing, the results gave plausible vertical and lateral (sideways) displacements, but also described implausible longitudinal movements along the axis of the bridge. Digital signal processing techniques applied to the data are reported. Due to the satellite constellation in the UK, a large void exists from the zenith to the horizon in a northerly direction. This lack of GPS satellites results in poor satellite geometry in the north-south direction, and hence poor north-south precision, explaining the unsatisfactory element of the Millennium Bridge results. More importantly a technique to overcome the issues is described. Notwithstanding this, the lateral vibration frequencies obtained from the GPS data agree extremely well with those found in the modal surveys carried out by Arup, even when displacement amplitudes are small.
Gateshead Millennium Bridge, UK: fabrication, assembly and erection
Authors: Butterworth Kevan , David Carr , Kassabian Paul
Published: November 2015

On 20 November 2000 the Gateshead Millennium Bridge was lifted into place, in one, over the UK’s River Tyne. The spectacular nature of the bridge design—the world’s first vertically rotating bridge—and the audacity of the erection scheme attracted large crowds and significant publicity. The bridge currently takes its place as part of the regeneration of the Gateshead Quayside. This paper describes the fabrication and erection of the bridge structure by Watson Steel.
Reducing differential settlements of approach embankments
Authors: Shen Shui-Long , Hong Zhen-Shun , Xu Ye-Shuang
Published: November 2015

This paper presents a case history of an approach road remediation project on a low embankment over soft Ariake clay, located in the coastal Saga Plain of Japan. After the road had been opened to traffic for two-and-a-half years, large settlements were observed, and there was significant differential settlement between piled structures and approach road embankments on soft clay. This differential settlement had a significant impact on vehicle ride quality, and necessitated a remediation programme. In the remediation project, a new method called the column approach (CA) method was adopted to support a transitional zone at the interfaces of piled structures and road embankment. With the CA method a transitional zone was designed at these interfaces to be supported by soil-cement columns of varying lengths to smooth out the settlement profile within these zones. Field monitoring was conducted following completion of remediation. The CA method was also compared with two other Japanese code-designated methods: overlaying a new pavement on the existing pavement at a certain time interval, and constructing a concrete cushion slab under the road pavement. Both practical and economic aspects are examined in the case study presented. This study shows that, when the differential settlement is over 0·3 m, overlay remediation is not economic, and the approach cushion method does not perform well. The CA method not only reduces the differential settlement effectively, but also reduces the total construction cost, although the initial investment is relatively high.
The microstructure, tensile response and fracture behavior of a high-performance structural steel: influence of orientation
Authors: Gowda Sunil , Hotz Carl , Patnaik Anil , Manigandan Kannan , Srivatsan Tirumalai S.
Published: November 2015

In this paper, the microstructure, hardness, tensile deformation and fracture behavior of a structural steel (ASTM A572-Grade 50) is presented and discussed. Specifically, the influence of test specimen orientation on microstructure of the as-provided material and resultant influence of microstructure on hardness, tensile properties and final fracture behavior are examined. Aspects related to the macroscopic mode and the governing intrinsic microscopic features that result from fracture of the steel specimens machined from the two orientations, longitudinal and transverse, are also examined. The microscopic mechanisms governing quasi-static deformation and final fracture behavior of this structural steel are discussed in light of the conjoint influence of test specimen orientation, intrinsic microstructural effects and nature of loading.
Preparation and characterization of ZnIn2S4 thin film
Authors: Sampath Hemalatha , Jayaraj Tamil Illakkiya , Oommen Rachel , Parthasarathy Usha Rajalakshmi
Published: November 2015

ZnIn2S4 (ZIS) crystalline thin film was prepared by novel spray pyrolysis technique. The as-deposited ZIS film was characterized by X-ray diffraction technique, ultraviolet–visible–near infrared spectroscopy, field emission scanning electron microscopy and energy dispersive analysis by X-rays. X-ray diffraction pattern revealed the crystalline nature of the material. Absorption edge was found to be 471 nm. Direct band gap of the film was calculated and found to be 2·68 eV. The absorption coefficient of the ZIS film exhibits the maximum value of 5·3 × 106 cm−1. The as-deposited ZIS composition was nearly stoichiometric.
Impact of conservatory as a passive solar design of UK dwellings
Authors: Amoako-Attah Joseph , B-Jahromi Ali
Published: November 2015

The prime goal of professionals in the built environment is to build cost-effective, environmentally sustainable buildings. This work focuses on the viability of passive solar design strategies of conservatories in the UK in mitigating the impact of future climate change. It further shows that passive solar energy utilisation in building design can contribute to the reduction of dwelling energy consumption and enhancement of indoor thermal comfort. Synergetic passive design strategies that optimise solar energy gains through thermal simulation analyses of varying future climatic conditions, occupant behaviour, building orientation, thermal mass, advance glazing, appropriate ventilation and shading, which influence the potential thermal performance of the conservatory, are devised. The balanced energy benefits of reduction in energy consumption through the application of passive solar design principles for space heating in winter and the challenge of reducing excessive solar gains in summer are analysed using the Cibse TM52 adaptive thermal comfort criteria. The results show that judicious integration of passive solar design strategies in conservatories, with increasing conservatory size in elongated south-facing orientation with an aspect ratio of at least 1·67, could decrease energy consumption, enhance thermal comfort and help to mitigate the impact of climate change when the conservatory is neither heated nor air conditioned.
Reuse of redundant gravels and phyto-conditioned sewage sludge
Authors: Chan May S. M. , Wolsey Iain
Published: November 2015

Blackburn Meadows is one of the largest waste water treatment works and landfills under Yorkshire Water’s operation. The site treats sewage from over 450 000 people and produces more than 20 000 t of sludge annually, which requires disposal. The sewage sludge is disposed of by means of a number of methods, including incineration followed by landfilling of the ash and direct disposal to landfill. Between 2010 and 2014, the construction and restoration of landfills on the site required approximately 6000 m3 of gravels and 18 000 m3 of topsoil. This paper describes two sustainable examples of material recycling – redundant filter bed gravels from another local site were crushed for reuse in landfill construction and sewage sludge after in situ phyto-conditioning was reused for landfill restoration. Atkins designed the requirements for the reused materials to achieve the most cost-effective specification, which resulted in cost savings of more than 48% for the basal leachate drainage blanket and more than 79% for the restoration layer. Phyto-conditioned sewage sludge is demonstrated to be supporting vegetation on the restored landfills. The construction and restoration of landfills at Blackburn Meadows provided an outlet for approximately 24 000 m3 of materials that would otherwise require disposal by other means.
Evaluation of a calculation method for embankments reinforced with geocells over soft soils using finite-element analysis
Authors: Avesani Neto J. O. , Bueno B. S. , Futai M. M.
Published: November 2015

This study addressed the analysis of geocells as basal reinforcement for embankments on soft soils. The equation proposed for this application is based on a previously developed method for predicting the bearing capacity of geocell-reinforced soils, which considers the characteristics of the founding strata, geocell in-fill soil, geometry of the geocell mattress, the slope angle and load from the embankment. The proposed method considers the factor of safety of the unreinforced system calculated by two methods, to which a term that is dependent on the geocell reinforcement is added to obtain the factor of safety for the reinforced system. The application of the method is demonstrated by an example using two different analytical methods for determining the factor of safety of the unreinforced system. The results thus obtained were compared with those from a three-dimensional finite element computer analysis for both unreinforced and reinforced cases.
An analytical solution for contaminant extraction in a radial flow field using PVD-enhanced system
Authors: Wang H.-Y. , Tang X.-W. , Tang Q. , Wang Y. , Gan P.-L.
Published: November 2015

Prefabricated vertical drains (PVDs) are a widely used in situ remediation technology for contaminated fine-grained soil. The current analytical solution that considers the infinite extraction boundary is not suitable for describing the short distance between the injection PVD (IPVD) and the extraction PVDs (EPVDs). The Dirichlet injection boundary proposed by the existing solution cannot meet the requirements for mass conservation. An analytical solution is developed based on the proposed simplified axisymmetric model. Vertical dispersion is considered in the model, and the initial concentration is exponentially distributed along the depth of the drain. The good agreement between the results obtained using the analytical solution and those obtained using the finite-element method validates the proposed solution and indicates that the simplified model can provide a simple and efficient solution to the prediction of the soil flushing process using a PVD-enhanced system. The model with the Dirichlet injection boundary can lead to significantly lower estimated flushing times for cleaning up a contaminant zone. The results show that the flux-type extraction boundary was better than the infinite extraction boundary. The dispersion can significantly affect soil flushing because the contaminant migrates from the highly contaminated zone to the low-contaminant-concentration zone.
Monitoring and numerical modelling of an instrumented mechanically stabilised earth wall
Authors: Cristelo N. , Félix C. , Lopes M. L. , Dias M.
Published: November 2015

The use of mechanically stabilised earth (MSE) structures is becoming widespread, especially for transportation-related infrastructure. The present study is a contribution to a better understanding of MSE wall structural performance, through the analysis of measurements obtained during the construction of a MSE wall for the A4 Portuguese highway, between Amarante and Vila Real – and the development of a numerical model based on the finite-element method. The monitoring programme and equipment are described. The numerical model was developed using a commercially available finite-element software package together with the Mohr–Coulomb elastoplastic constitutive model for the soils. The numerical model was calibrated against measured data. Finally, a parametric analysis was performed to quantify some of the most significant parameters that influence the general behaviour of the wall.
Laboratory study on the use of EPS-block geofoam for embankment widening
Authors: Özer A. T.
Published: November 2015

The use of expanded polystyrene geofoam (geofoam block) has been gaining momentum in roadway expansion projects. They are traditionally placed along the slope face of the existing roadway embankment as a side-hill fill. However, previous studies have shown the detrimental effects of seepage forces on the side-hill fill type of geofoam block configurations. In order to improve the performance of traditional embankment-widening configuration under seepage forces, an alternative geofoam block assembly is proposed. For this purpose, a lysimeter with dimensions of 60 cm high, 20 cm wide, and 200 cm long was constructed in the laboratory. A water reservoir located at the end of the lysimeter provided three different constant pressure heads (25 cm-, 38 cm-, and 50 cm-H2O pressure) during the tests. An embankment-widening geofoam block assembly was placed along the slope face of marginally stable sandy embankment to investigate the effects of seepage on the stability of geofoam block assembly. The dimensions of the geofoam blocks used to construct the embankment-widening sections were 2.5 cm high, 5 cm wide, and 15 cm long. In addition to the laboratory physical testing, factors of safety against global stability and hydrostatic sliding failures were studied through coupled numerical modelling. Stability modelling comprised fully coupled variably saturated flow and conventional limit equilibrium analysis to quantify the performance of the lysimeter test against global stability failure. Factor of safety against hydrostatic sliding was quantified using fully coupled variably saturated flow and stress-deformation modelling. Both laboratory and numerical models showed that the proposed geofoam block configuration significantly improved the performance of traditional side-hill fill embankment-widening technique under seepage forces.
Water vapour adsorption and desorption in GCLs
Authors: Rouf M. A. , Bouazza A. , Singh R. M. , Gates W. P. , Rowe R. K.
Published: November 2015

Super-saturated salt solutions are used to control relative humidity (RH) and to infer the hydration (water uptake and loss) behaviour of three needle-punched geosynthetic clay liners (GCLs) with respect to time under conditions of both free swell and 20 kPa applied stress. It is shown that RH and applied stress play a key role in the hydration behaviour with time when GCL specimens were in equilibrium with water vapour. It was also observed that water uptake and loss was affected by the bentonite form (powdered or granular) and mineralogy of the bentonite. However, the effect of GCL structure (i.e. difference in geotextiles and bonding of needle-punched fibres to the carrier geotextile) on their hydration behaviour for GCLs with similar form of bentonite was not significant for RH ≤ 97.7%. The effect of GCL structure became more apparent at 100% RH (for all GCLs). The results presented in this study can be used to better assess the hydration of GCLs in field applications such as waste containment liners and cover systems at different RH and overburden stress conditions.
Cyclic and post-cyclic behaviour from sand–geogrid interface large-scale direct shear tests
Authors: Liu F.-Y. , Wang P. , Geng X. , Wang J. , Lin X.
Published: November 2015

The understanding of cyclic and post-cyclic behaviours of the soil–geosynthetic interface is essential for the design of geosynthetic- reinforced soil structures under repeated loads, such as those induced by traffic, earthquakes and compaction. In this paper, a series of monotonic direct shear tests and cyclic direct shear integrating monotonic direct shear tests were conducted by using a large-scale direct shear testing device. The effect of normal stresses, cyclic shear amplitude and cycle number on the post-cyclic behaviour of the interface are investigated. In addition, the influence of cyclic shear on interface direct shear behaviour was discussed in detail. The test results indicated that both the peak and residual shear stresses of the interface during the post-cyclic shear phase increased linearly with normal stress and the number of cycles. The volume contraction, which was induced by the direct shear, decreased with the increase in normal stress. The interface apparent adhesion and friction angle increased with the cyclic shear.
Discussion: On the distinct phenomena of suffusion and suffosion
Authors: Fannin R. J. , Slangen P. , Mehdizadeh A. , Disfani M. M. , Arulrajah A. , Evans R.
Published: November 2015

A valuable conceptual framework for the characterisation of seepage-induced internal instability was provided in the article under discussion, particularly for the ‘suffusion and suffosion’ phenomena. A few modifications are suggested here to clarify the definitions in the original paper.
Anisotropic stress and shear wave velocity: DEM studies of a crystalline granular material
Authors: O'Donovan J. , O'Sullivan C. , Marketos G. , Muir Wood D.
Published: November 2015

Discrete element modelling (DEM) of a face-centred cubic assembly of spherical particles has been used to study the influence of anisotropic stress states on the shear wave velocity of a granular material. The shear waves were generated and detected in a way equivalent to the use of bender elements in laboratory testing. Comparisons are presented between the discrete element simulations and analytical and empirically derived methods of relating stiffness to the degree of confining stress anisotropy. The results confirm previous empirical observations that wave velocity is strongly influenced by the stresses in the direction of propagation and in the direction of oscillation of the shear wave. The wave velocity is, however, largely independent of the stress orthogonal to the plane containing the wave motion.
Physical and numerical modelling of the thermally induced wedging mechanism
Authors: Pasten C. , García M. , Cortes D. D.
Published: November 2015

Field observations and laboratory experiments show that temperature cycles can lead to wedging and accumulation of permanent displacements in several geosystems. The magnitude of these displacements depends on the geometric configuration of the components, the thermo-mechanical properties of the materials and interfaces, and the signature of the temperature signal. A physical model of a geometry susceptible to thermally induced wedging is analysed both experimentally and numerically in this article. The model consists of a driving wedge and a resisting block that rests on a rigid L-shaped base. The geometrical conditions required for the mechanism to manifest itself are found using equilibrium analysis of sliding and toppling. These conditions are reproduced in a physical model that is instrumented to measure changes in displacement and temperature in response to a cyclic temperature input. A numerical model was also developed to simulate the thermo-mechanical behaviour of the geometry. The numerical results and experimental measurements show that the accumulation of plastic displacement induced by temperature cycling is proportional to the period and amplitude of the input temperature signal.
Interpretation of piezoball dissipation testing in clay
Authors: Mahmoodzadeh H. , Wang D. , Randolph M. F.
Published: November 2015

Full-flow penetrometers such as the cylindrical T-bar and spherical ball are now being used widely in soft seabed sediments due to their advantages of larger projected area and minimal correction for overburden pressure. A ball penetrometer fitted with one or more pore pressure transducers (piezoball) is of special interest as it can provide information on the soil consolidation properties by means of dissipation tests. Although analytical and numerical solutions have been developed to evaluate the undrained resistance factor for the ball, the absence of a similar theoretical basis has limited the use of piezoball dissipation testing. This paper provides the results of numerical analyses undertaken to model the excess pore pressure field generated during penetration of a piezoball, including its shaft, and the decay of pore pressure during a subsequent dissipation test. The analyses used a coupled large deformation finite-element (LDFE) method incorporating the modified Cam-Clay model. The robustness and validity of the LDFE analyses were verified by comparison with analytical and alternative numerical solutions of ball penetration and with experimental data from centrifuge model dissipation tests. The effects of soil properties and shaft–ball geometry on the dissipation response at two locations on the ball were studied. A normalised time factor for excess pore pressure dissipation, together with benchmark dissipation curves, are proposed for generic interpretation of the dissipation response around a piezoball.
Stresses in soil–bentonite slurry trench cut-off walls
Authors: Li Y.-C. , Cleall P. J. , Wen Y.-D. , Chen Y.-M. , Pan Q.
Published: November 2015

The long-term performance of soil–bentonite slurry trench cut-off walls is highly dependent on the hydraulic conductivity of the soil–bentonite backfill, which according to laboratory tests can decrease significantly as consolidation pressure increases due to corresponding reductions in void ratio. Consequently a reliable estimate of the hydraulic conductivity of backfill in the field requires proper calculation of effective stresses. A model is proposed to predict the steady-state horizontal and vertical effective stresses in the backfill after consolidation. The arching effect is considered by way of force equilibrium, and the lateral squeezing effect of inward displacement of the trench side walls is considered by assuming the cut-off wall is surrounded by soil, which is represented by a Winkler idealisation. The proposed model is applied to consider a soil–bentonite slurry trench cut-off wall in New South Wales, Australia, and the predicted stress profile is in good agreement with that calculated from cone penetration test data. Compared to those predicted by geostatics and other alternative models, the proposed method offers a significant improvement in the prediction of stress in soil–bentonite slurry trench walls. The obtained stresses are then used to estimate the hydraulic conductivity in the backfill. It is found that the hydraulic conductivity is relatively high in the shallow region owing to the low state of effective stresses, which requires consideration in cut-off wall design, and decreases slightly with the depth in the deeper region. Finally a parametric study identifies the side wall friction and the modulus of horizontal subgrade reaction of surrounding soil as having the most significant impact on the estimated stresses.
Finite-element analysis of a deep excavation case history
Authors: Dong Y. P. , Burd H. J. , Houlsby G. T.
Published: November 2015

The design of deep excavations requires careful consideration of the influence of various soil/structure interaction mechanisms and detailed issues relating to the construction processes and the mechanics of the soil. Finite-element analysis provides a useful design tool for deep excavations, but care needs to be taken to ensure that an appropriate level of detail is included in the model. This paper describes a three-dimensional finite-element analysis of a deep excavation supported by a diaphragm wall, recently constructed in Shanghai. The principal purpose of the study is to investigate the level of detail that is required in the finite-element model to obtain results that provide a realistic representation of the wall and ground movements measured during the construction process. Studies are conducted on (a) the influence of the soil constitutive model on the quality of the results; (b) procedures to model the effect of post-cure shrinkage in the concrete floor slabs; (c) procedures to model the construction joints in the diaphragm wall; (d) the relative merits of using shell and solid elements to model the diaphragm wall; and (e) the sensitivity of the analysis to the assumed initial horizontal stresses in the soil.
Effect of spatial variation of strength and modulus on the lateral compression response of cement-admixed clay slab
Authors: Liu Y. , Lee F.-H. , Quek S.-T. , Chen E. J. , Yi J.-T.
Published: November 2015

In deep excavation construction, improved soil layers consisting of overlapping cement-admixed columns formed by deep mixing method or jet grouting are often used to stabilise an excavation in soft soils. The purpose of such soil layers is to resist lateral compression generated by movement of the retaining wall. Cement-admixed soils are well known to have high heterogeneity in strength. In this paper, the heterogeneity in strength and Young's modulus are studied using random finite-element analyses, considering three sources of variation: namely, a deterministic radial trend in strength and Young's modulus; a stochastic fluctuation component due to non-uniform mixing; and positioning errors arising from off-verticality of the mixing shafts. The results show that positioning errors have the largest effect on the strength of the slab as a whole, whereas the radial trend has the smallest effect, when normalised by the volume-average strength. Based on the results obtained, methods are proposed which allow equivalent homogeneous mass strength and modulus of the improved slab to be determined for a chosen percentile of exceedance or reliability index, which can be used in deterministic finite-element analyses.
A simple equation for obtaining finite strain solutions from small strain analyses of tunnels with very large convergences
Authors: Vrakas A. , Anagnostou G.
Published: November 2015

This paper presents a novel, very simple, accurate, theoretically well-founded and widely applicable relationship expressing the tunnel convergences obtained from large strain elasto-plastic analyses as a hyperbolic function solely of the corresponding small strain convergences. It can thus be used for ‘self-correcting’ small strain solutions, removing the need for large strain elasto-plastic analyses at least at the preliminary design stage and quantifying a hitherto unknown error caused by disregarding the geometric non-linearity. The proposed relationship can be proved rigorously for the plane strain rotationally symmetric ground response problem with a general elasto-plastic constitutive law with or without dilatancy and hardening. Numerical analyses of characteristic two- and three-dimensional excavation problems show that this relationship is generally applicable, irrespective of the in situ stress state and the tunnel geometry. It is therefore very useful from an engineering point of view for the design of tunnels crossing heavily squeezing ground, where the convergences may be so large (sometimes well in excess of 10% of the tunnel radius) that the usual small strain elasto-plastic analyses are deficient.
Synthesis of cardanol oil building blocks for polymer synthesis
Authors: Jaillet Fanny , Darroman Emilie , Ratsimihety Amédée , Boutevin Bernard , Caillol Sylvain
Published: November 2015

This review proposes a platform approach for the synthesis of various building blocks from cardanol in one- or two-steps syntheses. Cardanol, which is a natural phenol, is issued from cashew nutshell liquid, a non-edible renewable resource, co-produced from the cashew industry in large commercial volumes. Cardanol is non-toxic and particularly suitable for the addition of aromatic renewable resources in polymers and materials. Various routes were used for the synthesis of di- and poly-functional building blocks used thereafter in polymer syntheses. Phenolation was used to dimerize/oligomerize cardanol in order to increase its functionality. Thio-ene was used to synthesize new reactive amines. Epoxidation and (meth)acrylation were also used to insert oxirane or (meth)acrylate groups in order to synthesize polymers and materials.