bluuebunny/crossref_metadata_2025 huggingface dataset:
New household waste recycling centre in Blackpool, UK
Authors: Cunningham Lee S. , Conroy Andrew
Published: November 2015

This paper describes the design and construction of Blackpool Council’s new household waste recycling centre. The scheme demonstrates the incorporation of sustainability considerations through design, construction and commissioning. Seeking to reduce the amount of household waste sent to landfill sites, the provision of a high-quality facility for recycling will encourage increased sustainability awareness and participation within the community. As a means of delivering a quality scheme, the challenge of ensuring high durability in combination with aesthetic and environmental enhancement has been met with innovation. Use of polymer fibre reinforcement in the heavy-duty apron slabs provides high durability under aggressive service loads. Elsewhere, incorporation of subsurface skips facilitates spatial optimisation and allows significant noise attenuation with minimal visual impact. Where possible, materials won from the demolition of existing time-expired structures were incorporated in the new scheme or distributed for reuse elsewhere.
Nuclear fusion power: a bright long-term future
Authors: Smith Chris Llewellyn , Ward David
Published: November 2015

Nuclear fusion, the process that powers the sun and stars, could be a viable commercial power source within 40 years. The Joint European Torus, the world’s leading fusion facility in the UK, has produced 16 MW of fusion power. Fusion produces relatively very little waste, is intrinsically safe and has essentially limitless supplies of fuel. There has been substantial progress in recent decades, although significant challenges remain. This paper summarises the basics of nuclear fusion, describes the present state of technology development and outlines the remaining steps needed to develop fusion power as a commercial reality.
Solar photovoltaic energy: generation in the built environment
Authors: Bahaj AbuBakr
Published: November 2015

Compared to other renewable energy technologies, modular solar photovoltaic technologies that convert sunlight into electricity and can generate power from watts to megawatts are more versatile and can be integrated within building envelopes. The cornerstone of the technology is the solar cell, which is manufactured from various semiconductor materials including silicon. Conversion efficiencies and costs have improved significantly in recent years and there are now many national schemes and energy targets promoting the use of photovoltaic technology in the built environment. This paper describes the current state of solar photovoltaic technology and the approaches being considered for using it to generate electricity within buildings.
Safety and traffic management for PGA 2006 in Watford, UK
Authors: Hejazi Lara , Smith Andy
Published: November 2015

This paper sets out the safety and traffic management arrangements for one of the most prestigious events in the sports calendar, the PGA World Golf Championship, held for the first time in the UK in 2006. Hertfordshire Highways was responsible for ensuring that safety was maintained and gridlock avoided during the six-day event. This paper describes the meticulous planning arrangements prior to the event, as well as the coordination between the many organisations responsible for ensuring that traffic could enter and exit the various car parks and that plans were in place in the event of an emergency on site. The paper ends with lessons learned and considers what actions taken might be different if an event of this scale were to be held in Hertfordshire in the future.
0-1 Piecewise linearization approach for interval-parameter nonlinear programming: application to environmental management under uncertainty
Authors: Li Y.P. , Huang G.H. , Yang Z.F. , Nie S.L.
Published: November 2015

Interval-parameter nonlinear programming (INP) is an extension of conventional nonlinear optimization methods for handling both nonlinearities and uncertainties. However, challenges exist in its solution method, leading to difficulties in obtaining a global optimum. In this study, a 0-1 piecewise approximation approach is provided for solving the INP, through integration with an interactive algorithm for interval-parameter optimization problems. Thus, the INP model can be transformed into two deterministic submodels that correspond to the lower and upper bounds of the objective-function value. By solving the two submodels, interval solutions can be obtained, which are used for generating a range of decision options. The developed method is applied to a case of long-term municipal solid waste (MSW) management planning. Not only uncertainties expressed as interval values but also nonlinearities in the objective function can be tackled. Moreover, economies of scale (EOS) effects on waste-management cost can also be reflected. The results obtained can be used for generating decision alternatives and thus help waste managers to identify desired policies for MSW management and planning. Compared with the conventional interval-parameter linear and quadratic programs, the developed INP can better reflect system-cost variations and generate more robust solutions.
Melting temperatures of Al2O3 and MgO under pressure
Authors: Shuai Zhang , Hui Li
Published: November 2015

The melting temperature–pressure phase diagram for corundum (Al2O3) and magnesium oxide (MgO) are predicted through the Clapeyron equation in which the pressure-dependent volume difference is modeled by introducing the effect of surface stress–induced pressure. Al2O3 and MgO have been employed to test the reliability of the model.
Nutrient recovery from foam with microwave treatment
Authors: More Abhilasha , Srinivasan Asha , Liao Ping Huang , Koch Fred , Mavinic Donald S. , Lo Kwang Victor
Published: November 2015

Phosphorus recovery and solids reduction potential from foam generated in the anoxic reactor of membrane-enhanced biological phosphorus removal system were studied using the microwave-enhanced advanced oxidation process (MW/H2O2-AOP). The MW/H2O2-AOP-treated foam at different experimental conditions showed significant improvement in solubilisation of orthophosphate, ammonia, volatile fatty acids and soluble chemical oxygen demand as well as settling and dewatering ability. The most significant factors maximising orthophosphate release in the order of most to least affecting were (i) microwave heating temperature, (ii) combined effect of microwave heating temperature and hydrogen peroxide addition and (iii) addition of sulfuric acid. At temperature 180°C, pH 3 and hydrogen peroxide dosage 0·5% v/v, nutrient solubilisation, settling, and dewatering properties were at their maximum with 67% of the total phosphate solubilised as orthophosphate.
Briefing: Laboratory permeability determinations for biosolids
Authors: O’Kelly Brendan C.
Published: November 2015

Biosolids/sewage sludge materials are the residue by-products of municipal wastewater treatment. Drainage of biosolids storage facilities is a critical aspect of their design. Laboratory permeability tests are widely performed for economical and practical reasons. Reported laboratory coefficient of permeability (k) values for these materials suggests very/extremely low permeability. However, limited field data reported for sewage sludge material would tend to suggest significantly greater k values. This briefing article explores issues related to the water permeability (filter size) of the porous media (discs) in contact with the specimen drainage boundaries during laboratory consolidation and permeability testing of biosolids/sewage sludge materials. These include clogging of their pores by fine soil particles and biogenic gas bubbles, bio-clogging, and the increase in viscosity of the pore liquid remaining within the test specimen due to filtering action. In applications where rates of flow (and consolidation) are measured, their effect can be to produce misleading results, potentially by many orders of magnitude. Recommendations on laboratory consolidation and permeability testing, including selection and verification of appropriate porous media, are presented. Issues relating to the analysis and interpretation of experimental consolidation data are discussed, with caution urged on the use of classical consolidation theory for these difficult and unconventional geomaterials.
Cycling infrastructure in London
Authors: Deegan Brian
Published: November 2015

The aims of this article are to demonstrate the successes and failures of the £100 million London Cycle Network plus project and to discuss the standard of the highway engineering schemes delivered, particularly in relation to their overall effect on ride quality as defined by the cycling level of service assessment set out in the 2014 London cycling design standards. By highlighting areas where changes could have been made to improve the delivery of the project, it is hoped that lessons can be learnt for future projects of this type. The design approaches of each of London’s 33 local authorities were cross-referenced against cycling growth and pedal cycle collisions. From the analysis, the project is shown to have had a positive impact on promoting cycling growth in central London but little identifiable impact on collisions. The article also shows how a reliance on shared-use footways as a design practice could reduce the propensity for people to cycle. As a conclusion, it is suggested that ride quality should be the primary measure of success even if, in reality, the cost of delivering this and the impact it may have on other road users may render the highest levels of service difficult to achieve at present. The paper is relevant to all those seeking to manage or set up major transport projects with time-constrained objectives. It will be of particular interest to those involved in the planning or delivery of cycling infrastructure.
Controlling indoor air temperature using bagasse ash bricks
Authors: Madurwar Mangesh V. , Ralegaonkar Rahul V.
Published: November 2015

To investigate the indoor temperature variations of buildings constructed with different masonry materials, the small scale modelling technique was used. Two small scale models were designed and built as per the standards (SP: 41), one with sugarcane bagasse ash (SBA) bricks and another with commercially available fly ash bricks. In order to assess the indoor temperature of the built model houses, the room temperature recordings were monitored for the period of a year over the study area (Nagpur, Maharashtra, India), which has a composite type of climatic condition. The thermal conduction of the exposed wall assembly was estimated by the surface temperature readings of the built houses. The techno-economic viability for the developed model houses was also carried out. The detailed analysis revealed that the developed SBA brick model house (M-1) was thermally more resistant and economic than the fly ash brick model house (M-2). The study revealed that the SBA bricks are novel, and were found to be a better thermally insulated masonry construction material than the commercially available fly ash bricks.
New climate change rainfall estimates for sustainable drainage
Authors: Dale Murray , Luck Barry , Fowler Hayley J. , Blenkinsop Stephen , Gill Elliot , Bennett Jemma , Kendon Elizabeth , Chan Steven
Published: November 2015

Sewer flooding, urban surface water flooding and wet weather pollution are recognised as significant problems in the UK and elsewhere in the world, and changes in extreme rainfall arising as a consequence of climate change are likely to exacerbate these problems. This paper reports on new approaches to estimate potential future rainfall intensity changes over the UK at temporal and spatial scales that impact on urban drainage systems. The research (part of UK Water Industry Research’s programme of climate change related projects) has produced estimates of rainfall intensity change over different parts of the UK using a climate analogue approach and a very high-resolution (1·5 km) climate model developed by the UK Met Office. The new estimates produced are, in general, higher than existing UK climate change allowances for rainfall intensity. Sewer flooding volumes, flooding frequency and frequency of pollution events are also investigated for one location; indicating that these incidents and flood volumes are also likely to increase in the future.
Pullout response of geogrids after installation
Authors: Pinho-Lopes M. , Paula A. M. , Lopes M. L.
Published: November 2015

ABSTRACT: Damage of geosynthetics during installation processes can affect their performance, so they are typically represented in design by applying reduction factors to their tensile strength measured in the laboratory. This paper contributes to better understanding whether this is representative of the pullout response of geogrids when confined in soil. The effects of installation damage induced in field trials of two extruded geogrids and one composite with a grid structure were studied. Pullout tests were used to characterise the impact of installation damage on the soil–geosynthetic interface interaction. The coefficients of interaction were analysed to assess the impact of different parameters, including the nominal strength of the geogrids and compaction energy applied. The coefficient of interaction was affected differently by installation, depending on both the geosynthetic and the soil in contact with it. Confinement in a soil with higher friction angle was more effective in mobilising the interface strength, for both undamaged and damaged samples. The type of soil in contact with the geosynthetics was more relevant for the interface strength than the normal stresses applied in the tests. The main lesson learned from this study is that the use of results from tensile strength of damaged materials to estimate the corresponding effects on their pullout response can lead to very conservative solutions.
Frictional behaviour of three critical geosynthetic interfaces
Authors: Bacas B. M. , Cañizal J. , Konietzky H.
Published: November 2015

ABSTRACT: This paper's scope is the shear interaction mechanisms of three critical geosynthetic interfaces (geotextile/geomembrane; drainage geocomposite/geomembrane and soil/geomembrane) typically used for lined containment facilities such as landfills. A large direct shear machine was used to carry out 159 geosynthetic interface tests. The results showed strain softening behaviour, a very small dilatancy, 0.1–1 mm, and non-linear failure envelopes at normal stress range of 25–500 kPa. The three types of interfaces present the same main interaction mechanisms: interlocking and friction. For geotextile/geomembrane and drainage geocomposite/geomembrane interfaces, the higher the asperity height, the higher the interface shear strength. Whereas for soil/geomembrane interfaces, the higher the soil shear strength, the higher the interface shear strength. The drainage geocomposite/geomembrane interface showed the lowest friction angles, followed by the geotextile/geomembrane and the soil/geomembrane interfaces.
Model tests on methods to improve dewatering efficiency for sludge-inflated geotextile tubes
Authors: Guo W. , Chu J. , Zhou B.
Published: November 2015

ABSTRACT: Geotextile tubes made of woven geotextile materials have been widely applied to dewater waste sludge such as digested bio-solids, sewage sludge, dredged materials, industrial solid wastes, fly ash and coal slurry. However, the dewatering process of single geotextile tubes is time consuming. Two methods to accelerate the dewatering process of slurry in geosynthetic tubes were studied using laboratory model tests. The first method was to stack one tube on top of another and use the weight of the top tube to preload the bottom one. The second method was the vacuum method proposed in this paper to use vacuum pressure to consolidate the slurry in the geosynthetic tube. A 2.0-mm-thick woven polypropylene geosynthetic sheet was selected for the geotextile tubes. The deformation, pore water pressure and tensile forces monitored during the model tests against time are presented and analysed in this paper. The properties of the soil after consolidation were also measured and compared. The model test data showed that the vacuum method resulted in a lower water content and higher deformation rate than the two-layer stacking geotextile tube method. Compared with the stacking method, the vacuum method could reduce the risk to the geotextile sheet from explosion.
Infiltration into unsaturated reinforced slopes with nonwoven geotextile drains sandwiched in sand layers
Authors: Thuo J. N. , Yang K. H. , Huang C. C.
Published: November 2015

The use of nonwoven geotextile drains in geosynthetic-reinforced soil (GRS) structures has been suggested to facilitate the dissipation of pore water pressure. It has also been recognised that the nonwoven geotextile may retard water penetration due to the capillary barrier effect under unsaturated soil conditions and can function as a drainage material only once the soil immediately above it is nearly saturated. In this study, numerical models of unsaturated slopes with nonwoven geotextile drains, subjected to rainfall infiltration were developed to investigate the unsaturated hydraulic behaviour and stability of slopes constructed with nonwoven geotextile drains in thin layers of highly permeable sand (i.e. sand cushions). The numerical models were first validated for their suitability for modelling water flow and the capillary barrier effect within unsaturated soils using the experimental results from a one-dimensional soil column infiltration test and full-scale infiltration tests. Next, a series of numerical simulations of unsaturated slopes with and without sand cushions and under different infiltration conditions were performed. The numerical results indicated that the sand cushions reduced the development of the capillary barrier effect by acting as an intermediate material between the backfill and the nonwoven geotextile, which bridged the gap between two materials with very different unsaturated hydraulic characteristics. The reduction of the development of the capillary barrier effect led to the accumulation of pore water pressure above the nonwoven geotextile being effectively dissipated downward. The sand cushions also acted as additional drain layers to facilitate the drainage of water within the slope system. Thus, the inclusion of sand cushions enhanced the local slope stability for soils above the top geotextile layer. Based on the numerical results, methods for determining the occurrence of the capillary barrier effect are identified from the literature and discussed.
Ultimate bearing capacity of saturated reinforced horizontal ground
Authors: Huang C.-C.
Published: November 2015

The effects of soil saturation on the ultimate bearing capacity characteristics of reinforced and unreinforced horizontal sandy ground were investigated using a 100-mm-wide rigid strip footing. The test results revealed that saturation of the soil influenced the ultimate bearing capacity characteristics of unreinforced and reinforced ground in two ways: a reduced effective self-weight of the soil and an apparent cohesion induced by negative excess pore pressures. Ground saturation had a major influence on the footing settlement at peak footing load (Sp) partially due to the existence of negative excess pore water pressures. Values of Sp for the saturated ground were 100–200% larger than those for the dry one, regardless of the reinforcement state. For both saturated and dry reinforced ground, the moment of peak footing load was consistent with that of the maximum reinforcement force, revealing the effectiveness of geosynthetic reinforcement for enhancing the ultimate bearing capacity of the footing. An equation extended from that proposed in an earlier publication by the author and a colleague was used to simulate the effects of reinforcement and apparent cohesion of the saturated ground. The calculated values of bearing capacity ratio agreed well with the measured values.
Slope stabilisation using EPS block geofoam with internal drainage system
Authors: Akay O.
Published: November 2015

Lightweight expanded polystyrene (EPS) geofoam (geofoam block) is used in slope remediation works as a soil substitute fill to reduce driving forces that can lead to global instability. On the other hand, the presence of seepage flow requires special attention because geofoam block slope systems are vulnerable to seepage-induced lateral forces. In this study, the effect of an internal drainage system on the alleviation of piezometric pressures within the back-slope of a geofoam block slope system was investigated. For this purpose, laboratory experiments were conducted using a small-scale lysimeter with dimensions of 60 cm height, 20 cm width, and 200 cm length. The slope was compacted with sand to obtain an overall dry unit weight of 14 kN/m3. The constant piezometric head boundary conditions of 25, 38 and 50 cm generated the necessary hydraulic energy gradient for the seepage flow directed from the water reservoir of the lysimeter to the 45° angle slope face. The slopes were remediated by using geofoam blocks assembled in an embankment-type configuration at the toe of the slope. The internal drainage system consisted of grooved geofoam blocks that formed the 10, 15 and 22.5 cm high embankments. Deep-seated failures of the non-remediated slope were prevented except for the experiments with 10 and 15 cm high embankments under 50 cm pressure head boundary conditions. In general, the internal drainage system alleviated the piezometric pressure conditions within the back-slope by lowering the phreatic surface using the active drainage channels observed during laboratory experiments. These drainage channels provided a convenient passageway for seepage flow. The coupled numerical variably saturated flow modelling and slope stability modelling predicted the factor of safety for global stability which confirmed the observed physical conditions in the laboratory. The use of the internal drainage system increased the factor of safety of the geofoam block slope system under seepage conditions.
Behaviour of anchored geosynthetic-reinforced slopes subjected to seepage in a geotechnical centrifuge
Authors: Rajabian A. , Viswanadham B. V. S.
Published: November 2015

An anchored geosynthetic system (AGS) is an in situ reinforcing system that can be utilised to improve the stability of earth slopes. In this study, performance of AGS slopes under seepage conditions was investigated through a series of centrifuge model tests. These tests were conducted at an acceleration of 50g on silty sand slopes having 2V:1H and 1V:1H inclinations and reinforced with AGS in a large beam centrifuge located at the Indian Institute of Technology Bombay, India. Seepage was induced through a seepage simulator system to raise the water table within the reinforced slopes. The stability and seepage analysis was carried out for AGS slope models and the results were compared with those obtained from the centrifuge model tests. The results indicated that the location of the predicted failure surface in AGS slopes depended on the type of AGS load used for the analysis. The results of seepage analyses indicate that when the phreatic line was close to the physically observed phreatic line it nevertheless exits the face at higher elevation than physically observed in the centrifuge.
Shear-induced changes in smooth geomembrane surface topography at different ambient temperatures
Authors: Frost J. D. , Karademir T.
Published: November 2015

The shear strength of particulate material–smooth geomembrane interfaces results predominantly from ploughing and/or sliding of the particles at the interface. The relative contribution of particle sliding and ploughing for a given smooth geomembrane surface is principally a function of relative material hardness, particle angularity, and normal stress. The relative material hardness is ambient temperature dependent since the geomembrane is polymer based. When ploughing occurs at any temperature, the geomembrane surface wears, resulting in altered surface topography and different interface strength. This paper summarises the results of a study that quantified changes in the surface roughness of geomembranes as a function of ambient temperature, normal stress, and particle angularity. Surface roughness measurements were made on both virgin and post-shear smooth geomembrane specimens using a stylus profilometer to quantify the extent of wear resulting from shearing against different counterface materials at different temperatures under different normal stresses. Increased ambient temperature and particle angularity significantly increased the geomembrane surface roughness and provided quantitative insight into the wear mechanisms at granular material–smooth geomembrane interfaces.
On the size-dependent compressive resistance of bonded granules
Authors: Liu F. , Jiang M. , Sun C. , Deng G.
Published: November 2015

Peculiar properties of cemented geomaterials are endowed by inter-particle bonds, of which the contact behaviour has recently been found to be size dependent. This study uses the distinct-element method to investigate the size effect on the compressive resistance of an inter-particle bond, which is modelled as an assemblage of tiny bonded particles. The model parameters are carefully calibrated according to laboratory observation of a realistic reference material. The simulations demonstrate that the compressive resistance of the bond largely depends on bond slenderness and boundary curvature as well as the bond contact area. The combined effect of three size parameters can be captured in a single formula. Given the bond contact area in common, a thin bond between large particles tends to fail at higher compressive force than a thick bond between small particles because the coalescence of micro-cracks inside the bond is hindered more effectively in the thin case, resulting in ultimate failure due to compressive crushing rather than tensile cracking. A full consideration of the size effect on the bond contact strength may change the picture of progressive bond breakage in cemented geomaterials, which deserves further investigation once a size-dependent bond contact law is obtained.
Effects of temperature and suction on secant shear modulus of unsaturated soil
Authors: Zhou C. , Xu J. , Ng C. W. W.
Published: November 2015

Understanding of the secant shear modulus (G) of soil at small strains (lower than 1%) is essential to predict the performance of many earth structures in working conditions. Furthermore, soils at shallow depth are often unsaturated and subjected to variations of suction and temperature. Yet the effects of suction and temperature on G of unsaturated soils at small strains are often neglected and not fully understood. In this study, the secant shear modulus of an unsaturated silt was measured at various suctions and temperatures using a suction- and temperature-controlled triaxial apparatus with local strain measurement. The experimental results confirm that the shear modulus of unsaturated soil at small strains considerably increases with increasing suction under isothermal conditions, due to increases in the average skeleton stress and the stabilisation effects on the soil skeleton induced by meniscus water. On the other hand, at constant suction, G decreases as temperature increases. This is likely due to a reduction of the air–water surface tension with an increase in soil temperature, leading to a reduced influence of suction on G values.
Numerical study of one-dimensional compression in granular materials
Authors: Lopera Perez J. C. , Kwok C. Y. , O'Sullivan C. , Huang X. , Hanley K. J.
Published: November 2015

The discrete element method has been employed to simulate vertical one-dimensional compression of an idealised soil. Direct measurement of the full stress tensor was possible and the results show that K0 (the ratio of horizontal to vertical effective stresses) increases with void ratio, which is consistent with previous experimental studies. The anisotropic fabric induced during compression was quantified by considering the orientations and magnitudes of the normal contact forces. For the denser samples there was a definite bias towards more vertically oriented contacts, resulting in lower stresses being transmitted in the horizontal direction for a given vertical stress. In contrast, the contacts were oriented more isotropically in the looser samples, allowing more similar stresses to be transmitted in the horizontal and vertical directions.
Numerical evaluation of clay disturbance during blade penetration in the flat dilatometer test
Authors: Kouretzis G. P. , Ansari Y. , Pineda J. , Kelly R. , Sheng D.
Published: November 2015

This paper presents a study on the amplification of horizontal soil stresses during flat dilatometer test (DMT) blade penetration based on three-dimensional total and effective stress numerical analyses, while considering stress–flow coupling and large deformations. The focus here is on saturated clays, and the effect of soil stress history on the horizontal stress index is discussed in detail. The obtained results appear to be in good agreement with published and new field data, leading to the proposal of two new expressions for estimating the overconsolidation ratio and the earth pressure coefficient at rest directly from flat dilatometer tests in estuarine clays.
Ageing effects on the small-strain stiffness of a bio-treated compacted soil
Authors: Morales L. , Romero E. , Jommi C. , Garzón E. , Giménez A.
Published: November 2015

The effect of ageing on the small-strain shear stiffness of compacted silty-clayey sand following a ‘soft’ biological treatment is discussed. Samples were prepared by static compaction, adding urea-degrading bacteria to the compaction water. No nutrients were artificially added, relying on the natural availability of urea and calcium ions (Ca2 +) in the humic soil and in the compaction water for the bacteria to precipitate calcium carbonate. After compaction, to replicate different environmental boundary conditions, some of the samples were cured in a system open to vapour transfer and some were cured in a closed system. The small-strain shear stiffness was periodically tracked with bender elements during the ageing period. Tests were run in parallel to investigate the unconfined compression strength, the water retention properties and soil pore size distribution changes during ageing. The test results revealed a small but consistent increase in the small-strain shear stiffness during the ageing period due to the microbiological treatment, in both the closed and open systems. In the latter case, the contribution of the microbiological treatment to the increase in stiffness could be estimated after correcting the data for the suction increase due to evaporation.
Modelling granular soil behaviour using a physics engine
Authors: Pytlos M. , Gilbert M. , Smith C. C.
Published: November 2015

A physics engine is a software library used in the film and computer games industries to realistically animate a physical system. In this paper it is shown that particulate media can be faithfully modelled using a rigid body physics engine, thereby providing a viable alternative to the discrete element method codes currently used in the field of geomechanics. An overview of the simulation method implemented in the widely used Box2D physics engine is provided, and it is shown that this tool can successfully capture the critical state response of granular media, using particles modelled as randomly shaped polygons.
Wettability of crushed air-dried minerals
Authors: Lourenço S. D. N. , Woche S. K. , Bachmann J. , Saulick Y.
Published: November 2015

The importance of soil particle wettability has been recognised in mining engineering, soil science and geomorphology but to a lesser extent in geotechnical engineering, perhaps due to the assumption that soils, or in general most common minerals, are always wettable. From the soil science and geomorphology literature, changes in soil wettability are known to influence soil processes such as infiltration, erosion and post-wildfire debris flows. Organic matter has been identified as one of the most important factors controlling the wettability of natural soils. However, its occurrence is very shallow and often shallower than the depth of interest for geotechnical processes. Therefore, it becomes essential to determine the wettability of minerals, in particular because it can be linked to processes that involve crushing or abrasion of soil particles. This paper examines the wettability of 21 common, freshly crushed minerals (sulfides, oxides and silicates) by measuring wettability via contact angles with the sessile drop method and the Wilhelmy plate method, including particle attributes such as aspect ratio and sphericity. The results revealed a wide range of contact angles for the uncoated minerals, with the sulfides showing strong water-repellent behaviour and the silicates remaining very wettable. Higher contact angles are associated with mineral particles that converge to the shape of a sphere and for those that have a larger aspect ratio.
Tensile strengths of flocculated compacted unsaturated soils
Authors: Beckett C. T. S. , Smith J. C. , Ciancio D. , Augarde C. E.
Published: November 2015

Flocculating agents can be introduced to soils through a number of natural or anthropogenic processes. This paper investigates the effect of flocculant addition (aqueous calcium chloride (CaCl2)) on the tensile strengths of two soils of differing flocculation susceptibility. Tensile strengths were found using the Brazilian (direct splitting) test for a range of suction values. A decrease in tensile strength was found for a soil with high clay content, which was consistent with previous findings in the literature. However, the strength of the soil with lower clay content unexpectedly increased. Results were interpreted using the extended Mohr–Coulomb (EMC) yield criterion fitted to data above the residual suction value. Changes in EMC parameters were used to infer changes in material behaviour on calcium chloride addition. Results have important implications for the design of geotechnical structures, for example engineered cover systems, exposed to flocculating conditions.
Strength characteristics of polymer-bonded sands
Authors: Garcia N. F. , Valdes J. R. , Cortes D. D.
Published: November 2015

This article documents an experimental study conducted to examine the tensile and shear strength behaviour of uniform sands cemented artificially by heat treatment of added polyethylene fines. The results show that, like other cemented sands, the strength of polymer-bonded sands (PBS) is dependent on cement content, grain size and mineralogy, yet the tensile and shear strengths of PBS are significantly larger than those of other artificially cemented sands. Microscopy observations reveal that the strength of the bond shared by the polymer and the mineral surface gives rise to the cementation strength. Acoustic emissions complement the shear strength data by confirming the transition between a cementation-controlled regime at low confinement and a friction-controlled regime at high confinement.
Three-dimensional experimental granular mechanics
Authors: Hall S. A. , Wright J.
Published: November 2015

Results are presented from a new method for experimental analysis of the mechanics of real granular materials in three dimensions. The method involves a combination of X-ray tomography and three-dimensional (3D) X-ray diffraction to provide the grain-scale structural evolution (grain positions and kinematics, grain-contact distributions and grain–grain contact fracture) simultaneously with the tensor strains of each of the individual grains, while performing mechanical testing on a granular assembly. Using this approach, force chains can be identified in three dimensions as continuous lines of load-carrying (strained) grains. Furthermore, the identified load distribution can be considered as a separation and organisation of ‘carriers’ (grains experiencing significant strain) and ‘non-carriers’ (grains carrying little or no load), which is characterised by the use of the Gini coefficient, borrowed from economic statistics. Correspondences are thus identified between the macroscopic stiffness of the granular assembly and both the evolution of granular strains and the distribution of the main load carriers.
Modelling the seismic performance of rooted slopes from individual root–soil interaction to global slope behaviour
Authors: Liang T. , Knappett J. A. , Duckett N.
Published: November 2015

Many natural and man-made slopes are planted with vegetation, and it is known that this can increase the stability of slopes under static conditions. There is anecdotal evidence that vegetated slopes also perform better than fallow slopes during earthquakes. However, the study of the dynamic behaviour of slopes planted with species having dichotomous (‘woody’) roots is relatively rare owing to the extreme expense and difficulty involved in conducting full-scale dynamic testing on shrubs and trees. In this paper, dynamic centrifuge testing and supporting numerical modelling have been conducted to study this problem. In the centrifuge modelling, ABS plastic rods are used to simulate repeatably the mechanical properties of real roots. The numerical modelling work consisted of two parts. First, a computationally-efficient beam-on-non-linear-Winkler-foundation (BNWF) model using existing p–y formulations from piling engineering was employed to produce a macro-element describing the individual root and soil interaction both pre- and post-failure. By adding contributions from the different root analogues of different diameters, smeared continuum properties were derived that could be included in a fully dynamic, plane-strain continuum, finite-element model in a straightforward way. The BNWF approach was validated against large direct shear tests having stress conditions simulating those in the centrifuge at different potential slip plane depths. The conversion to smeared properties for global time-history analysis of the slope was validated by comparing the continuum finite-element results with the centrifuge test data in terms of both the dynamic response and permanent deformations at the crest, and these demonstrated good agreement. Owing to the simplicity of the BNWF approach and its ability to consider variable root geometries and properties, along with variation of soil properties with depth, it is suggested that the validated approach described will be useful in linking individual root–soil interaction characteristics (root strength and stiffness, diameter variation, root spacing and so on) to global slope behaviour.
Modelling landslide liquefaction, mobility bifurcation and the dynamics of the 2014 Oso disaster
Authors: Iverson R. M. , George D. L.
Published: November 2015

Some landslides move slowly or intermittently downslope, but others liquefy during the early stages of motion, leading to runaway acceleration and high-speed runout across low-relief terrain. Mechanisms responsible for this disparate behaviour are represented in a two-phase, depth-integrated, landslide dynamics model that melds principles from soil mechanics, granular mechanics and fluid mechanics. The model assumes that gradually increasing pore-water pressure causes slope failure to nucleate at the weakest point on a basal slip surface in a statically balanced mass. Failure then spreads to adjacent regions as a result of momentum exchange. Liquefaction is contingent on pore-pressure feedback that depends on the initial soil state. The importance of this feedback is illustrated by using the model to study the dynamics of a disastrous landslide that occurred near Oso, Washington, USA, on 22 March 2014. Alternative simulations of the event reveal the pronounced effects of a landslide mobility bifurcation that occurs if the initial void ratio of water-saturated soil equals the lithostatic, critical-state void ratio. They also show that the tendency for bifurcation increases as the soil permeability decreases. The bifurcation implies that it can be difficult to discriminate conditions that favour slow landsliding from those that favour liquefaction and long runout.
Trends in large-deformation analysis of landslide mass movements with particular emphasis on the material point method
Authors: Soga K. , Alonso E. , Yerro A. , Kumar K. , Bandara S.
Published: November 2015

Traditional geotechnical analyses for landslides involve failure prediction (i.e. onset of failure) and the design of structures that can safely withstand the applied loads. The analyses provide limited information on the post-failure behaviour. Modern numerical methods are able to simulate large mass movements and there is an opportunity to utilise such methods to evaluate the risks of catastrophic damage if a landslide occurs. In this paper, various large-deformation analysis methods are introduced and their applicability for solving landslide problems is discussed. Since catastrophic landslides often involve seepage forces, consideration of the coupled behaviour of soil and pore fluid is essential. Two approaches to model soil–pore fluid coupling in large-deformation analysis using the material point method (MPM) are introduced. An example simulation is presented for each approach; one on a model levee failure and the other on a natural cut slope failure (the Selborne experiment conducted by Cooper and co-workers in 1998). In the levee failure case, MPM simulation was able to capture a complex failure mechanism including the development of successive shear bands. The simulation was also able to predict excess pore pressure generation during the failure propagation and the subsequent consolidation stage. The simulations demonstrated the importance of the dilation characteristics of soil as well as changes in geometry for the post-failure behaviour. In the Selborne case, MPM was able to simulate the progressive failure of brittle, overconsolidated clay. The evolution of shear stresses along the failure surface was also captured by the MPM. The changes in the pore pressure and the actual shape of the failure surface were simulated by the MPM. The importance of accurately modelling the shear band within the MPM framework is highlighted.
Effects of preloading and consolidation on the uplift capacity of skirted foundations
Authors: Li X. , Gaudin C. , Tian Y. , Cassidy M. J.
Published: November 2015

Centrifuge tests investigating the effect of compressive preloading and consolidation on the subsequent uplift capacity of shallow skirted foundations that rest on lightly over-consolidated kaolin clay are reported. The uplift resistance, total and pore pressures at the foundation invert were monitored during the installation, consolidation and uplift. The results show that uplift performed immediately after the preloading generates a lower capacity due to the remoulding of the clay and reduction in soil strengths that result from the application of preloading. The soil strength can be recovered and eventually enhanced by the subsequent consolidation process. A theoretical framework, where the variation of the soil operative strength with preloading and consolidation is interpreted using the critical state concept, is proposed to explain and justify the experimental observations. The framework is validated through retrospective prediction of the uplift resistance of the centrifuge model tests with good agreement for a wide range of levels of preloading and degrees of consolidation demonstrated.
Behaviour of laterally loaded pile groups embedded in oil-contaminated sand
Authors: Nasr A. M. A. , Krishna Rao S. V.
Published: November 2015

Soil contamination with oil is not only harmful for the environment, but is also detrimental to associated buildings and foundations. Thus, the main aim of this study is to discover the influence of oil-contaminated sand on the lateral behaviour of pile groups. Single pile tests were also performed for comparison purposes. Small-scale model tests and a numerical study using finite-element analysis were performed on single piles and pile groups. The investigations were carried out by varying the percentage of oil content, the thickness of the contaminated layer and the pile group configurations. To fit the field conditions, contaminated sand layers were prepared by mixing the sand with oil content of 0–6% with regard to dry soil. The results indicated that the friction angle was reduced with increasing oil content. Thus, there is a significant decrease in the lateral resistance of the pile groups caused by oil contamination. The lateral resistance is decreased and the lateral deflection of the piles is increased with an increase in the thickness of the contaminated sand layer and percentage of oil content. For the middle pile in the lead row in the group, the maximum bending moment increased by about 40% at an oil content of 2% over that in clean sand. The agreement between observed and computed results is found to be reasonably good in terms of lateral resistance capacity and group efficiency.
Soil water retention curves representing two tropical clay soils from Sudan
Authors: Al Haj K. M. A. , Standing J. R.
Published: November 2015

Soil water retention curves (SWRCs) form an essential component of frameworks coupling the hydromechanical behaviour of unsaturated soils. The curves describe how suction changes with variables such as degree of saturation. SWRCs can be determined from incrementally drying initially saturated reconstituted samples to a final residual state, thus developing the primary drying curve (PDC). The primary wetting curve (PWC) is established from subsequent incremental wetting and is hysteretic compared with the PDC. SWRCs for two reconstituted, high-plasticity, tropical clays from Sudan have been determined using the filter paper technique, for which the maximum measurable suction is 30 MPa. At this suction the degree of saturation for both soils was greater than 40% and did not reduce much further on full drying under ambient laboratory conditions. Thus the primary SWRCs did not develop into the usual sigmoidal shape expected. The development of SWRCs under various subsequent cycles of wetting and drying are presented and discussed along with details concerning volumetric changes and cracking during drying. In order to investigate the uniqueness of the PDC and PWC and the effect of initial void ratio, SWRCs were determined for samples formed by dynamic and static compaction under different applied energy levels and also for intact samples. These were found to be located to the left of the PDC and often the PWC too.
Soil–pile thermal interactions in energy foundations
Authors: Bourne-Webb P. J. , Bodas Freitas T. M. , Freitas Assunção R. M.
Published: November 2015

In this technical note, the results of a set of simplified numerical analyses are presented. The analyses were undertaken in order to examine the validity of a descriptive framework that was previously proposed to illustrate the behaviour of thermally activated piles and to highlight the potential limitations of some analytical methods that are being applied to their study and design. Working on the premise that some soils, specifically moderately to highly over-consolidated clays, may experience thermally induced volume changes larger than concrete elements inserted into the ground, the results of the study highlight that analyses that do not account for the initial temperature field and boundary conditions, and the response of the ground to temperature changes, may yield erroneous conclusions with respect to the performance of operational thermally activated piles used to support temperature-controlled structures.