bluuebunny/crossref_metadata_2025 huggingface dataset:
Estimating hydraulic conductivity from piezocone soundings
Authors: CHAI J.C. , AGUNG P.M.A. , HINO T. , IGAYA Y. , CARTER J.P.
Published: November 2015

A method for estimating the hydraulic conductivity of soils from piezocone penetration tests is suggested in this paper. By invoking Darcy's law over the finite time required for an increment of cone penetration, it is argued that there will be some water movement through the soil around the cone, albeit very small if the soil is very fine grained. Based on this argument, and noting the comprehensive test data collected previously by Elsworth & Lee, a bi-linear relation between the dimensionless piezocone sounding metric BqQt and the dimensionless hydraulic conductivity index KD plotted on double logarithmic scales has been proposed for soils ranging from sands to clays. It is demonstrated that these revised relationships can be used to evaluate plausible values of hydraulic conductivity from piezocone sounding records taken at two different clay soil sites in Saga and Yokohama, Japan. The major significance of this work is in extending the range of application of the method first proposed by Elsworth & Lee for sands to almost all soil types. This was possible after appropriate modification of Elsworth and Lee's original method.
The complementary roles of physical and computational modelling
Authors: Randolph M. F. , House A. R.
Published: November 2015

Physical modelling in geotechnical engineering is used extensively, in spite of the high investment costs for experimental facilities and the contrasting decline in computing costs. The paper discusses why physical modelling is still needed, and the manner in which it may be used in conjunction with numerical analysis to develop the simple conceptual models that are used for the major part of design. Two example problems are discussed, one in relation to scale effects when dealing with interface shearing involving dilation, and one in the area of penetration testing. In both cases, physical modelling is shown to reveal limitations in analytical models. An approach for in situ determination of the consolidation coefficient, by means of variable rate penetration testing, is described.
Centrifuge model study on pile subject to lapses during installation in sand
Authors: Leung C. F. , Lee F. H. , Yet N. S.
Published: November 2015

A series of centrifuge model tests has been carried out to investigate the behaviour of pile subject to lapses during installation in sand. To simulate an installation lapse, an instrumented model pile is jacked to a desired depth in sand, then allowed to rest for a desired duration before being jacked deeper into the sand during centrifuge flight. The test results reveal that the pile experienced a reduction in penetration resistance between the end of initial installation and the beginning of reinstallation. The magnitude of reduction in pile penetration resistance is noticeable even for short lapse duration and increases with the duration of installation lapse. However, the rate of reduction in resistance attenuates rapidly with time. The changes in the soil and pile stresses observed from instruments installed in the sand and along the pile shaft reveal that stress reduction has taken place around the pile tip and along the lower pile shaft. To further examine the observations, modified one-dimensional compression tests were carried out to monitor the stress changes in sand that is not allowed to settle once the desired loading pressure is reached. The test data reveal that stress reduction in. sand around the pile tip and along the lower pile shaft is a cause for the reduction in pile penetration resistance during an installation lapse.
Development and performance of an active type shear box in a centrifuge
Authors: Takahashi A. , Takemura J. , Suzuki A. , Kusakabe O.
Published: November 2015

An active type shear box in a geotechnical centrifuge has been newly developed for investigating behaviour of structures subjected to large soil movement. This shear box was designed focusing on deformation of a pile due to lateral movement of soil during earthquake under quasi-static conditions, neglecting inertial effects of soil and pile. The apparatus consists of a laminar box and actuators. With the actuators mounted beside the laminar box, the deformation of the laminar box can be controlled and any ground displacement can be imposed. Even though the deformation of the soil in the box can be controlled as intended, the stress condition of the soil may be different from the ideal condition as in ground motion due to earthquake. Effects of geometry of the shear box and lamina-link mechanism on the deformation and stresses of the soil in the box are investigated with simple finite element analyses. Details of the system are described and the performance of the apparatus in preliminary tests is discussed.
Large-scale laminar shear box for lateral pile loading tests with ground displacements
Authors: Tsuchiya Tomio , Kakurai Masaaki , Yamashita Kiyoshi , Hamada Junji
Published: November 2015

Through a number of studies about the damage of pile foundations in the 1995 Hyogoken-Nambu earthquake, it is shown that damage to piles might be caused not only by horizontal inertial forces at the pile head but also kinematic forces acting on the piles due to shear deformation of soil deposits. To investigate the effect of lateral ground displacements on piles, the authors have developed a large-scale laminar shear box complete with loading system. In order to approximate the actual soil-pile interactive behaviour during big earthquakes, large-diameter model piles can be installed in the laminar shear box. The loading system is able to apply passive lateral pressures on a pile or pile groups embedded in the model ground by generating lateral displacements in the laminar shear box. In this paper, a general description of the large-scale laminar shear box and its loading system are presented. Lateral load tests were conducted on a model steel-pipe pile in this laminar shear box. The results of the loading tests indicated that the strain distribution on the pile is clearly affected by the profile of lateral ground displacements.
Sliding block analysis of lateral spreading based on centrifuge results
Authors: Sharp Michael K. , Dobry Ricardo
Published: November 2015

A number of lateral spreading centrifuge tests conducted at RPI at 50 g on fine Nevada sand are reviewed and used to produce a first order analytical model based on wave propagation theory which predicts well the measured patterns of permanent ground displacement. In-flight base shaking of a slightly inclined laminar box containing a homogeneous saturated sand deposit induces liquefaction and lateral spreading. Both water and a viscous fluid fifty times more viscous than water are used as pore fluid in the tests. The observed lateral displacement profiles during and at the end of shaking are very different: smooth and more or less parallel profiles in the “viscous fluid” tests, and profiles containing a concentrated straining zone in the “water” tests. Other differences include stabilization of the depth of liquefaction at an intermediate depth early in the shaking in the “water” tests, compared with downward propagation of the liquefaction front throughout the shaking accompanied by a closely related downward propagation of a deformation front in the “viscous fluid” tests. A close correspondence was observed in all tests between the liquefaction/nonliquefaction boundary and the zone of high soil straining controlling the lateral spreading phenomenon. These observations are used to produce the first order analytical model, which predicts that all permanent displacements are generated within a transition zone centered around the liquefaction front and bounded below by the deformation front. The analytical model predicts successfully the measured displacement patterns in both “viscous fluid” and “water” tests, by allowing the transition zone to propagate downward or remain stationary during the shaking, respectively. Approximating the transition zone by a sliding plane reduces the model to the popular rigid sliding block analysis with either a stationary or moving sliding plane.
Centrifugal simulation of wave propagation using a multiple ball dropping system
Authors: Itoh K. , Koda M. , Lee K. I. , Murata O. , Kusakabe O.
Published: November 2015

This paper describes the development of a multiple ball-dropping system to study wave generation and propagation from surface ground vibration sources in a centrifuge. This system can simulate not only point load, but also quasi-moving loads caused by high-speed trains running through a viaduct. The paper presents a set of physical data of wave propagation in the surrounding ground. The effectiveness of a range of wave barriers was investigated using various geometry and materials, and it was found that softer barriers are generally superior to stiffer barriers, and that the geometry of the barrier significantly affects the motion of the barrier. It was also suggested that the superimposition of the waves could be applicable to cases of moving load, provided that the factor of safety for bearing capacity of foundation is sufficiently high.
Modelling of seismically induced liquefaction under high confining stress
Authors: Gonzalez Lenart , Abdoun Tarek , Sharp Michael K.
Published: November 2015

Evaluation of seismically-induced liquefaction under high confining stress, such as might relate to the foundation soil under large earth dams, is based on the extrapolation of observed behavior and correlations at shallow depths. In practice, the behavior of saturated sand and other cohesionless soils under these conditions is not well understood.

Experiments were conducted, at the 100 g-ton RPI centrifuge facility, to investigate confining stress effects on liquefaction potential, under the boundary and loading conditions of a deep horizontal saturated sand deposit. Three level ground models, with either a homogeneous profile or a dense layer over a loose layer, were tested in a laminar box. In two of the models, a steel plate surcharge was placed on the soil to increase confinement. Recorded accelerations and pore pressures, vertical surface settlement, and shear strains and stresses derived from the accelerations using System Identification, were analyzed to study the effect of high confining stress on the development of soil liquefaction.
Modelling of pile foundations retrofitting strategies against seismically induced lateral spreading
Authors: Abdoun Tarek , Wang Yingjuan
Published: November 2015

Experience from earthquakes and centrifuge models have shown the great importance of the shallow nonliquefiable soil in increasing the forces and moments imposed on the pile cap and pile foundations subjected to liquefaction-induced lateral spreading. A series of centrifuge tests were conducted to study the great importance of the shallow nonliquefiable soil in increasing the bending response of the pile foundation. A promising rehabilitation approach of existing foundations is to replace the shallow soil in a trench around the pile and pile cap by a soft material that will yield under constant lateral soil forces. Seven centrifuge experiments are performed to study lateral spreading and its effect on single pile foundations. Retrofitted and non-retrofitted pile tests in three-layer soil systems, with and without a mass above the ground, are preformed. All centrifuge tests are conducted at the 100 g-ton RPI centrifuge, using the inclined laminar box and model piles as research tools. The specific objectives of this study are accomplished mainly through the centrifuge experiments and corresponding interpretations and comparisons.
Centrifugal simulation of vibration reduction generated by high-speed trains using rubber-modified asphalt foundation and EPS barrier
Authors: Itoh Kazuya , Zeng Xiangwu , Murata Osamu , Kusakabe Osamu
Published: November 2015

When constructing a high-speed railway route in urban areas, the reduction of ground vibration and noise generated by the passage of a high-speed train is of vital importance for environmental considerations. This paper describes the results of a laboratory study on ground vibration caused by high-speed trains, using a series of centrifuge model tests to investigate the effect of a vibration reduction method which uses a crumb rubber-modified asphalt (CRMA) layer at the vibration source and an EPS barrier at the transmission path. It was found through centrifuge tests that CRMA, which is a material with high shear stiffness and damping ratio, can reduce the vibration away from the source especially when working together with EPS barrier. Therefore, CRMA has great potential as a foundation material for high-speed railway trackbed.
Centrifuge modelling for seismic retrofit design of an immersed tube tunnel
Authors: Adalier K. , Abdoun T. , Dobry R. , Phillips R. , Yang D. , Naesgaard E.
Published: November 2015

A centrifuge testing program was conducted to assess the earthquake performance of countermeasure retrofit techniques for an existing concrete tunnel embedded in a liquefiable sandy deposit. In a series of three separate heavily instrumented model tests, a tunnel section-foundation system was studied first without retrofitting, and then with a densified-wall and a gravel-wall liquefaction countermeasure techniques. The test results provided valuable insights into the underlying mechanism and effectiveness of each countermeasure and served as basis for calibration and validation of computational modelling of the George Massey Tunnel seismic retrofit design. Test results showed that the implemented countermeasures significantly reduced the tunnel movements. The gravel-wall technique was found to be particularly effective in reducing the extent of liquefaction as well as reinforcing the tunnel-foundation system against earthquake induced deformations. The centrifuge test results and the calibrated numerical model studies led to a final ground improvement scheme that included both stone column densification and seismic gravel drains.
Performance of piled raft foundations subjected to static horizontal loads
Authors: Horikoshi Kenichi , Matsumoto Tatsunori , Hashizume Yoshinori , Watanabe Toru , Fukuyama Hideki
Published: November 2015

A series of static loading tests were conducted vertically and horizontally on piled raft models and their components (single piles and rafts alone) on sand by using a geotechnical centrifuge. Much focus was placed on the load-displacement relationship and the load sharing between the piles and the raft in the piled raft system. Effects of the rigidity at pile head connection on the piled raft behavior were also examined. This paper provides basic information on the performance of piled raft foundations subjected to horizontal loads. Principal findings from the present study are: 1) The stiffness and the resistance of the single pile in piled raft foundations are different from those observed in the isolated single piles of the same size, due to the difference in the confining stress condition around the piles; 2) Piles play important roles in increasing horizontal ultimate resistance of piled raft foundations; 3) The initial horizontal stiffness of a piled raft is not always higher than that of a raft (alone) as the piles reduce the contact pressure between raft and soil, and hence the stiffness of the upper soils; 4) Higher horizontal load is transferred to the piles in the piled raft with rigid pile head connection, which leads to higher initial horizontal stiffness compared with that in the piled raft with hinged pile head connection; 5) The proportion of vertical load carried by the piles in a piled raft remains largely unchanged during horizontal loading, while the proportion of horizontal load carried by the piles increases as the horizontal displacement increases.
Selective pore pressure transducers for use in model tests to study two-phase flow in porous media
Authors: Oung O. , Bezuijen A.
Published: November 2015

Measurements of selective Pore Pressure Transducers (PPTs) have been validated in element tests. These sensors were originally designed for model tests to investigate two-phase flow in a porous medium. By separately measuring pressures in each phase (wetting and non-wetting) of two immiscible phase liquids in sand, capillary pressure can be obtained in model tests under 1 - or N-g conditions. A calibration was carried out by imposing stationary DNAPL head pressures. The relationship between capillary pressure and water saturations “Pc-S” of a two-phase fluid/sand system was determined using the selective PPTs mounted in direct contact with the soil model. For comparison, the classical method consisting of pressure a measurements outside the soil model, with fluid contact only, was also applied to obtain the Pc-S relationship. The resulting Pc-S curves of the classical method were compared to those of the selective PPTs. These results validate the new measuring technique. Practical experiences on the use of the selective PPTs in model tests are also discussed.
Displacement fields induced by penetrometer installation in an artificial soil
Authors: Lehane B. M. , Gill D.R.
Published: November 2015

This paper presents results from a laboratory experiment, which was devised to provide accurate measurements of the soil displacement paths followed during undrained installation of a penetrometer. The experiment combined the use of a precision video camera and a transparent soil with properties similar to those of a natural soft clay. The measured displacement paths are compared with an existing database of measurements and with predictions derived using the Shallow Strain Path Method. These comparisons reveal characteristics of penetrometer installation that will be of assistance to the advancement of currently developing numerical simulations of the installation process.
Physical modelling of a cantilever wall
Authors: Gaudin Christophe , Garnier Jacques , Thorel Luc
Published: November 2015

Centrifuge modelling is henceforth a recognized experimental technique. Its use for study of retaining wall was until now slowed down by the necessity to carry out in-flight excavation in order to model correctly the stress history in the structure. A new experimental study was then carried out in the Laboratoire Central des Ponts et Chaussées to validate the use of a new robot to simulate excavation process in front of retaining structures and to perform complementary operation related to the behaviour of the wall. For this purpose, the behaviour of a 10 m high cantilever wall, embedded in dry Fontainebleau sand, was studied as well as the interaction between the cantilever wall and a strip footing placed close to the wall. Both experimental devices and procedure are presented in details. The data recording device gives access to both displacements of the wall and the strip footing and to the bending moments in the wall. Experimental results are presented and commented and show the validity of the procedure and the potentiality of this device to study more complex or realistic problems involving retaining structures.
Group pile behavior under lateral loading in centrifuge model tests
Authors: Tobita Tetsuo , Iai Susumu , Rollins K.M.
Published: November 2015

Response of a group pile under static and dynamic lateral load is studied using a geotechnical centrifuge with an arm length of 2.5 m. The group pile consists of 9 piles in a 3 × 3 pattern with a spacing of three times a pile diameter center to center. The study is at an initial phase where an overview of the behavior of group pile is obtained through model tests as a basis for further study. In particular, the study aims to answer the question whether the group pile effects and a p-y curve or a coefficient of subgrade reaction for seismic design can be evaluated based on the data from the static tests.

A total of seven model tests are performed. Three are static tests of a single and group pile in dry sand deposit. Four are dynamic tests of a single and group pile in dry and saturated deposits using a shake table mounted on the centrifuge. The results obtained through the model tests are: (1) group pile effects are observed in both static and dynamic tests, including those tests where liquefaction occurs; (2) residual pile displacements mobilized are larger in dynamic tests than in static tests for the same load applied at pile head. These results trigger the need to evaluate the following issues through more refined model test programs: (1) difference in p-multiplier (i.e. a ratio of the load for each pile in group pile over the load for single pile at the same displacement) in the static and dynamic conditions; (2) difference in p-y curve or coefficient of subgrade reaction for use in design in the static and dynamic conditions; (3) difference in the mechanism of lateral loading in the static and dynamic conditions, including the effects of inertial and kinematic interaction.
Experimental design, instrumentation and interpretation of reinforced soil wall response using a shaking table
Authors: El-Emam Magdi M. , Bathurst Richard J.
Published: November 2015

A series of dynamic shaking table experiments were performed at the Royal Military College of Canada (RMC) to investigate the seismic performance of reduced-scale reinforced soil walls constructed with different toe boundary conditions, facing panel configurations and reinforcement layouts. The models were 1 m high by 1.4 m wide by 2.4 m long and were constructed with a full-height rigid panel facing, a uniform sand backfill and multiple layers of polymeric geogrid reinforcement. The wall toe was constructed to simulate a perfectly hinged toe (i.e. the toe allowed to rotate only) in one series of models and an idealised sliding toe (i.e. the toe allowed to rotate and slide horizontally) in the other series. The model walls were instrumented to measure facing panel and soil backfill lateral displacement, reinforcement strains, horizontal and vertical toe loads, and both facing and backfill acceleration response. All the models were subjected to a horizontal stepped-amplitude sinusoidal base acceleration input. The paper is focused on the experimental design, material properties, instrumentation and the interpretation of results. Selected test results are presented to illustrate typical model response features. Finally, some implications to current seismic design practice are identified with respect to magnitude and distribution of reinforcement-facing connection loads and the influence of a structural facing and restrained toe boundary condition on wall response during base excitation.
Application of particle imaging velocimetry (PIV) in centrifuge testing of uniform clay
Authors: Zhang Y.D. , Tan T.S. , Leung C.F.
Published: November 2015

The Particle Imaging Velocimetry (PIV) technique is being used as an alternative tracking of centroids of markers placed in a regular grid to measure soil displacements. PIV has been used for many years in fluid mechanics; but for physical modelling in geotechnical engineering, this technique is still relatively new. The use of PIV is feasible provided the surface contains sufficient texture. A Cambridge group has shown that natural sand contains enough texture for applying PIV. But when homogeneous clay is used, there is not enough texture on the surface for PIV to be used. Thus to use PIV, a texture has to be marked on the clay surface. This paper addresses specifically the issue of PIV on clay model which does not have natural texture. Two different methods of marking this texture were examined. Then, through a series of calibration tests, errors under 1g and 100g conditions using the PIV method are assessed. Some factors influencing the accuracy of the PIV method were also examined. The results confirmed that without adequate texture, PIV cannot be applied to clay. The calibration exercise shows that the precision of PIV under 1g condition is about 0.008 mm while the precision at 100g condition is about 0.01 mm. It is also shown in this paper that increasing the density of particles per window beyond a threshold value will not contribute significantly to improved accuracy. However, using smaller size markers is desirable, for improved accuracy as well as being able to get more displacement vectors from the same imaging area.
Centrifuge modelling of tunnelling close to a diaphragm wall
Authors: Bilotta E. , Taylor R.N.
Published: November 2015

The experimental set-up and some results of a series of centrifuge tests which were performed at City University are shown and discussed. Tests were carried out on a circular model tunnel in a clay ground and in undrained conditions. The basic idea being tested was whether or not a diaphragm wall embedded at different locations close to a shallow tunnel could reduce movements in the ground extending beyond the wall and further away from the tunnel. The length of the embedded diaphragm wall was varied, as well as its thickness. The influence of the soil-wall interface was also studied. An image processing system was used to measure displacement fields in the models.

The influence of the tunnel support pressure on the displacement field is discussed. Also, the influence of the walls edge and of the embedding technique is shown. In particular two different ways of achieving a rough interface are compared.

A significant influence of the wall self-weight and of the interface roughness on the model stability was observed during the tests. Two kinematically admissible collapse mechanisms are analysed in order to understand these experimental findings.
Development of a model jack-up unit for the study of soil-structure interaction on clay
Authors: Vlahos George , Martin Christopher M. , Prior Michael S. , Cassidy Mark J.
Published: November 2015

The behaviour of spudcan footings under combined vertical, moment and horizontal loading is a critical aspect of the site-specific assessment of offshore jack-up platforms. In recent years, experiments on single footings have helped describe the non-linear load-displacement behaviour of spudcans on various soil types, and this behaviour has in turn been encapsulated numerically, typically in the form of semi-empirical models based on strain-hardening plasticity theory. There is cause for concern, however, that the application of these models in predicting the behaviour of a complete jack-up unit with multiple footings has yet to be verified experimentally. To achieve this, and to gain an improved understanding of the overall system behaviour under various loading regimes, a 1:250 scaled model of a representative jack-up unit has been designed, built and calibrated at The University of Western Australia (UWA). The model can be used to perform sophisticated 1-g pushover tests (both monotonic and cyclic) in which all key forces, moments and movements of the jack-up unit, including spudcan loads and displacements, are continuously monitored. Initial testing has been performed on reconstituted samples of soft overconsolidated kaolin. This paper discusses the design and development of the apparatus, its calibration and verification, the procedures used during a test, and the methods used to prepare and characterise the kaolin samples. General experimental aims are discussed, and aspects of the structural and geotechnical scaling are considered in detail. Some example results from a monotonic pushover test are presented to illustrate the capabilities of the system.
An image-based deformation measurement system for the geotechnical centrifuge
Authors: White Dave , Randolph Mark , Thompson Bart
Published: November 2015

New techniques of image capture and analysis have been recently applied to geotechnical centrifuge modelling. These techniques improve the utility of the geotechnical centrifuge by increasing the detail and precision of deformation measurements. This paper describes the use of a simple image-based deformation measurement system on a drum centrifuge. Precise deformation fields comprising many thousands of measurement points can be evaluated from images of plane strain tests using small soil models typically comprising 2 litres of soil. Digital still photography is used to capture high resolution images. A weighted shutter allows a continuous sequence of images to be captured without the need for an onboard PC or communication with the camera via sliprings. Particle Image Velocimetry (PIV) and close range photogrammetry are used to process the resulting images. Target markers are not needed since PIV operates on the spatial variation in image brightness to measure displacement. Close range photogrammetry allows image distortion to be corrected. Distortion leads to a 5% variation in image scale (or pixel size) for this test geometry. An example test of a skirted strip foundation under eccentric vertical load is analysed. The instantaneous velocity field at failure is manipulated to allow the realism of simple upper bound failure mechanisms to be examined. It is interesting to note that although the measured failure load matches almost exactly the optimal upper bound solution, the observed deformation mechanism differs significantly.
Ground settlement and wall deformation from a large scale model test on a single strutted sheet pile wall in sand
Authors: Tefera T. H. , Nordal S. , Grande L. , Sandven R. , Emdal A.
Published: November 2015

The ground settlement and wall deformation of a sheet pile wall during different stages of excavation have been studied using a large scale model test in a bin with dry sand at the Norwegian University of Science and Technology, NTNU. The model sheet pile wall was built prior to raining in the sand in a bin (4 m × 4 m in plan and 3 m deep). This paper deals with results from tests on a relatively loose sand with 43.2% porosity. Strain gauges, load cells and potentiometers were used to monitor the wall movement, the bending moments in the wall, the strut loads and the ground settlements. The large scale model test results were compared with finite element simulations based on an elastoplastic soil model calibrated only against conventional oedometer and triaxial test results performed on the sand used in the model tests. Discrepancies between the physical model test results and the simulations are discussed trying to identify the cause of the discrepancy when a discrepancy may have been observed and suggest improved procedures for parameter determination. However, in conclusion, the comparison generally shows good agreement, and illustrates how a finite element analysis can be used to predict the behaviour of a supporting wall.
Centrifuge model tests on behavior of double sheet pile wall cofferdam on clay
Authors: Khan M. Ruhul Amin , Takemura Jiro , Kusakabe Osamu
Published: November 2015

The behavior of double sheet pile wall cofferdam on a thick clay deposit subjected to a flash flood was studied through a series of centrifuge model tests. In a rectangular container a thick layer of kaolin clay was placed on a layer of fine silica sand. The clay layer was prepared with a defined stress history. The model cofferdam consisted of two aluminum sheet pile walls, with tie rods at the top and ground level. After driving the sheet pile walls to the sand layer, the inside of the sheet pile walls was excavated and filled with the same silica sand as used in preparing the bottom sand layer. Under 70 g centrifugal acceleration, the clay deposit was consolidated under the load from the fill to a certain degree and then water was fed upstream of the cofferdam to simulate high floodwater until the water level reached nearly to the top of the cofferdam or large deflection of the cofferdam was observed. Various factors affecting stability of the cofferdam and mechanism of failure were examined. Stability of the double sheet pile wall cofferdam on a thick clay deposit was also compared with a cofferdam on the sand deposit. Test results implied that: (i) shear deformation of the fill dominates the failure mechanism of the cofferdam, (ii) as the width of the cofferdam increases, the water height at failure increases, (iii) the resistance against high water does not always increase with increasing the embedment depth, (iv) the degree of consolidation of the clay foundation affects the stability of the cofferdam, though degree of consolidation was simulated after construction of the cofferdam, (v) performance with respect to the mechanical behavior of a cofferdam in a sand deposit is better than that in a clay deposit, and (vi) both the upstream and downstream sheet pile walls in a clay foundation are subjected to almost the same flexural stress compared to the larger flexural stress in the downstream sheet pile wall in a sand foundation.
Centrifuge modelling on performance of natural clay barrier with piles
Authors: Amatya B.L. , Takemura J. , Khan M.R.A. , Kusakabe O.
Published: November 2015

In this paper, the performance of natural clay barrier subjected to massive pile constructions is investigated using laboratory scale models on centrifuge. Model grounds comprising mainly either thick barrier of soft clay or stiff clay were made and pile construction, pile lateral loading were simulated besides conducting advective-diffusive transport modelling for very long prototype design period. Two types of pile namely opened end and close end steel piles were used as model piles. Deformation of the ground due to pile deflection under lateral loading and its impact on leakage, resistivity change in a pile vicinity ground due to contaminant movement were also monitored. Assessment of flow and transport around pilling area and pile free area was done on completion of centrifuge test by thorough model excavation, sampling and chemical analysis. Test results reveal that soft ground is strong enough to prevent its deterioration irrespective of the types of pile and their stiffness but stiff ground is susceptible to some amount of deterioration. However the degree of damage can be reduced by using OE piles for stiff ground under appropriate gravitational field. So the stiffness of the ground and its thickness are very important parameters to be considered for safety against possible environmental deterioration due to the mentioned activities.
Butanol effect on consolidated clay
Authors: Sentenac P. , Taylor R.N. , Lynch R.J. , Bolton M.D.
Published: November 2015

Clay is often used in the liners of landfill repositories to contain waste organic solvents or as a hydraulic barrier against pollutant migration. Some alcohols play a significant role in changing the hydraulic conductivity of clay by inducing the collapse of the clay’s pores through desiccation, with water being absorbed by the alcohol. Such desiccation can lead to cracking. Furthermore, gasoline compounds could be more easily transported in the alcohol rich pore fluid. A particular alcohol, Butanol, has been used in centrifuge experiments to attack a simulated consolidated Kaolinite clay layer. The experiments were conducted using a geotechnical centrifuge and a compacted clay model corresponding to an equivalent prototype clay layer that was 2 metres thick according to conventional scaling laws. Pore pressure transducers located in the clay layer monitored changes in suction caused by Butanol attack. The results of the experiments show that the influence of fluids with different surface tension on the air pressure in the clay, is an important factor to consider in addition to the hydraulic pressure and evaporation at every boundary. The results also confirmed the potential cracking effect of Butanol on Clay.
A cone pressuremeter for soil characterisation in the centrifuge
Authors: Thorel L. , Gaudin C. , Rault G. , Garnier J. , Favraud C.
Published: November 2015

A cone pressuremeter for use in the geotechnical centrifuge has been developed by the Laboratoire Central des Ponts et Chaussées (LCPC) based on the in-situ Ménard pressuremeter. It includes a pressuremeter probe, 20 mm long, mounted on a 10 mm diameter metallic shaft. Sensors measure the pressure inside the probe and the volume injected, leading to the determination of the limit pressure PL and the pressuremeter modulus EP, using a procedure similar to the one used for the in-situ Ménard pressuremeter. The technical aspects of the device are presented in detail as well as the testing procedure and the corrections required by the apparatus. Some preliminary results for tests performed in Fontainebleau sand and comparisons with cone penetrometer results are also presented. The correlation between the tip resistance and the limit pressure is conclusive, demonstrating the feasibility of such tests and the validity of the results.
Physical modelling of low-energy dynamic compaction
Authors: Hajialilue-Bonab M. , Rezaei A.H.
Published: November 2015

A physical modelling of low-energy dynamic compaction (DC) on fine, dry loose sand based on image processing (PIV method) was undertaken. Tamping was executed by rising and dropping semi-cylindrical steel tampers of known diameters and weights on the surface of sand deposit. The effective factors of DC and the deformation pattern of sand after tamper drops were investigated using the PIV method. The displacement field of soil mass was investigated. Strain elements were obtained from displacement patches in the ground. The changes in relative density due to impacts at different depths were evaluated using total volumetric strains. A normalized relation between the influence depth and DC parameters was presented for low-energy DC design. This relation may be used to predict the influence depth of improvement. By deriving crater depth versus drop number curves, the influence value of each impact on the increase of improvement depth was defined.
Soil deformation pattern around laterally loaded piles
Authors: Hajialilue-Bonab Masoud , Azarnya-Shahgoli Habin , Sojoudi Yones
Published: November 2015

In the analysis of soil–pile interaction under lateral load, the behaviour of soil around a pile is an important parameter which has a great influence on the results. In this paper the three-dimensional deformation pattern of soil around laterally loaded piles was studied on small-scale physical models in the laboratory using the particle image velocimetry method. In each step of loading two digital cameras were used to capture the deformed piles and soil, one above and the other on the side. One of the cameras was placed vertically in front of the test box and the other horizontally on top of it. Image processing was undertaken to evaluate the three-dimensional behaviour of deformed soil. Particle image velocimetry analysis was undertaken to obtain the displacement. The deformation pattern and shear strains of soil around laterally loaded single pile and pile groups were studied. The effects of pile length, stiffness and diameter on the soil deformation pattern were investigated. The group effect and interaction between piles in pile groups were also studied. Experimental results showed that a conical passive zone is established in front of laterally loaded piles.
A study on mechanical properties of cement paste using magnetite-silica nano-composites
Authors: Bolhassani Mohammad , Sayyahmanesh Maryam
Published: November 2015

Micro- and nano-siliceous particles have been employed as one of major components of Portland cement composites because of their filling effect and pozzolanic reaction. Enhancing the mechanical properties of Portland cement composites using nano-particles without workability reduction and dispersion difficulties is one of the challenges in the cement field of research. In order to overcome disadvantages of nano-particles in cement, a new method was investigated in this study. Magnetite-silica core-shell nano-composites (MS), which have been widely used in biological fields, were employed here as fillers and reinforcements in cement pastes. These nano-composite particles consist of nano-magnetite (NM) cluster and nano-amorphous silica shell. Different types of analysis such as X-ray diffraction, transmission electron microscopy and vibrating sample magnetometer were conducted on these particles to investigate their properties. MS particles were synthesised by coating nano-magnetite particles with tetraethyl orthosilicate (TEOS) as a source of silica. MS particles were used as an additive material in cement paste mixes with cement replacement ratios of 0·05, 0·1 and 0·2%. Additional samples were also made with the same cement replacement ratio of NM and nano-silica (NS). Experimental results indicated that the compressive strength of cement paste can be increased up to 14%. This is mainly attributable to the pozzolanic effect of silica shell in combination with the filler and nuclei effect of these particles. It was also found that the MS does not change the workability of mixes considerably. Additionally, the microstructure of cement pastes was characterised using scanning electron microscopy to evaluate the effect of NM, NS and MS particles on the microstructure of cement pastes.
How to evaluate pozzolanic activity of sulfate-rich fly ash
Authors: Qian Jueshi , Qin Jihui , Zhang Zhiwei , Shen Yan , Ye Ziqi , Hou Pengkun
Published: November 2015

The Frattini test and strength activity index (SAI) test have been commonly used methods to assess the pozzolanic activity of pozzolan by measuring its reaction extent, which would be affected by the sulfate content in pozzolan and the cement used. This study investigates the effect of sulfate content in sulfate-rich fly ash on the test results regarding pozzolanic activity by means of the Frattini test and SAI test; three fly ashes with different sulfate contents are used and their sulfate contents are further increased by adding calcined gypsums. There is significant correlation between the test results of the pozzolanic activity and the sulfur trioxide content of the cement–fly ash system, no matter whether the sulfates came from cement or fly ash. However, current methods may confound the test results regarding the pozzolanic activity of sulfate-rich fly ash. It is suggested that the sulfur trioxide content of the cement–fly ash system should be kept constant when the Frattini test and SAI test are selected to evaluate the pozzolanic activity of sulfate-rich fly ash or to compare with other fly ashes and pozzolans.
Measuring the distribution of sulfate phases in cement
Authors: Ma Ying , Qian Jueshi , Yang Sha , Deng Lingxi
Published: November 2015

Sulfate is present as various phases in Portland cement and these phases have distinct effects on the hydration and hardening of cement-based materials. A set of sulfate phases, with dissolution behaviour to easily soluble sulfates and gypsum, could be studied as a whole. Two chemical extraction methods, the 50% ethanol method and the saturated soda method, are initially proposed and described to study the quantitative distribution of easily soluble sulfates and gypsum in Portland cements. The ethanol method proposed can selectively dissolve easily soluble sulfates in cements and clinkers in a 1·5–2·5 min extraction process; and is more efficient than 1·5–2·5 min water extraction. The determination of gypsum depends on completely extracting the gypsum in a 2 h extraction with saturated soda solution at 300:1 (ml:g) of liquid–solid ratio. The gypsum determined is an overall phase, which would include anhydrite, semihydrate, dihydrate and other calcium sulfate in Portland cements.
Influence of paraffin wax as a self-curing compound in self-compacting concretes
Authors: Sri Rama Chand Madduru , Rathish Kumar Pancharathi , Swamy Naga Ratna Giri Pallapothu , Rajesh Kumar Garje , Krishna Rao Mupparisetty V.
Published: November 2015

Internal curing can be adopted to ensure the availability of water for the hydration of cement, mitigating the adverse effect of water loss to surroundings. The use of self-curing compounds is increasing in the context of the widespread use of self-compacting concrete (SCC) owing to its superior performance in both fresh and hardened states. This paper addresses the effect of using paraffin wax as a self-curing compound in SCC mixes. The variable parameters of the study include curing type, concrete grade (mix proportions), molecular weight and dosage of paraffin wax. Water retention, sorptivity and compressive strength tests were conducted on hardened concretes. The weight loss after 90 d was found to be less in specimens with a self-curing agent than in specimens without. The compressive strengths of the self-cured specimens closely matched those of conventional water-cured specimens. The optimum dosages of light and heavy molecular weight liquid paraffin wax were determined to be 0·1% and 1·0% by weight of cement respectively. It is this concluded that the use of self-curing compounds in SCC facilitates better hydration and thus enhancements in strength and durability properties.
Properties of ion leaching of alkali-activated blast furnace slag at early hydration
Authors: Kang Seungmin , Bak Sol-A , Kim Kyungnam , Song Myongshin
Published: November 2015

Efforts are being made to reduce carbon dioxide formation in the cement industry, and studies continue to show the effectiveness of blast furnace slag (BFS) as a cement substitute. BFS is well known for its hardening mechanism in ordinary Portland cement or for alkali activation owing to its latent hydraulic property. This study accurately analyses the mechanism of initial hydration delay caused by the latent hydraulic property of BFS, with the aim of establishing a basic theory to extend the use of BFS based on this initial hydration delay mechanism analysis. The concentrations of sodium hydroxide (NaOH) solution, used as an alkali actuator, are 0, 0·01, 0·1, and 1·0 M. To understand the early hydration, the leaching concentrations of calcium, aluminium and silicon ions are measured by inductively coupled plasma atomic emission spectroscopy. To confirm the hydration products formed by the leached ions, X-ray diffraction, Fourier transform infrared spectroscopy and thermogravimetric differential thermal analyses are conducted. For the BFS, calcium ions are leached in very high amounts when the sodium hydroxide concentration is ≤ 0·1 M. At sodium hydroxide concentration > 1·0 M, the leaching of calcium ions decreases noticeably, and aluminium and silicon ions begin to leach. Ettringite and calcium–silicate–hydrates (C-S-H) are confirmed as reaction products.
From bioinspired multifunctionality to mimumes
Authors: Lakhtakia Akhlesh
Published: November 2015

The methodologies of bioinspiration, biomimetics and bioreplication are inevitably pointing to the incorporation of multifunctionality in engineered materials when designing ever more complex systems. Optimal multifunctionality is one of the defining characteristics of metamaterials. As fibrous materials are commonly manufactured from a variety of source materials, mimumes – that is, microfibrous multifunctional metamaterials – are industrially viable even today, as exemplified by mimumes of parylene C. The microfibrous morphology of mimumes enhances surface-dominated effects in comparison to those evinced by bulk materials.
Computer analysis: avoiding the ‘black box’ syndrome
Authors: Lamb Anthony R.
Published: November 2015

Recent rapid advances in computer software and hardware have provided civil and structural engineers with increasingly powerful means of processing, storing, retrieving and displaying data. Most engineering consultancy firms now rely heavily on computers and software design packages to provide a competitive edge. However, there is a real danger of blind dependence on automated ‘black box’ techniques, the results of which may not be checked against engineering experience and intuition. This paper shows how this can happen and proposes a hierarchy of computer-aided design supervision to avoid potentially fatal errors resulting from flawed computer analysis.