bluuebunny/crossref_metadata_2025 huggingface dataset:
Applying triaxial compression stiffness data to settlement prediction of shallow foundations on cohesionless soil
Authors: Lehane B. , Cosgrove E.
Published: November 2009

This paper proposes an expression for the triaxial compression stiffness of a siliceous sand and gravel based on the findings of recent research and on data from laboratory tests incorporating local small-strain instrumentation. The expression captures the strong, but variable, stress level and loading history dependence of stiffness in addition to the well-known effects of density and strain level. The formulation is applied to settlement records made in carefully controlled footing tests and is shown, when used in conjunction with additional simplifying design assumptions, to be suitable for the prediction of the settlement of shallow foundations on cohesionless soil at typical working loads.
Site investigation of soft tailings deposits using a hovercraft
Authors: Newson T. A. , Fahey M.
Published: November 2009

Large volumes of tailings are produced annually by the gold mining industry of Western Australia (WA). This material is hydraulically discharged into large storage facilities using sub-aerial deposition methods. A considerable proportion of the gold produced comes from highly weathered rock, resulting in tailings with significant clay contents. Consolidation of these materials can be very slow, particularly if occurring under the effects of self-weight alone. Therefore, disposal management strategies are particularly reliant upon allowing successive layers of tailings to dry sufficiently before the next layer is deposited. In order to investigate and therefore optimise the behaviour of these tailings storages, it is necessary to develop a method of gaining access to the tailings at all stages following deposition. For this purpose a small hovercraft has been modified and fitted with equipment to enable shear vane tests, piston samples, BAT water samples, CPT and spherical penetrometer tests to be conducted in locations that would otherwise be inaccessible. Results gained from a number of site investigations on active tailings storages have enabled full characterisation of these sites to be accomplished and have shown this to be a viable approach. Examples of typical data are shown from these investigations.
Geotechnical aspects of A331—Blackwater Valley route centre section
Authors: Stephen M.
Published: November 2009

The A331 is a new dual carriageway link between two major east–west routes; the A31 Winchester–Guildford road and the M3 London–Southampton motorway. Its route follows the valley of the River Blackwater on the Surrey–Hampshire border to the east of Aldershot and Farnborough. The road was designed and constructed in three sections, with the centre section being the last to be completed, in 1996. The horizontal and vertical alignments of this section were dictated by numerous constraints so that the very difficult ground and groundwater conditions present had to be overcome rather than avoided. This paper describes the ground and groundwater conditions, the problems that these presented and the solutions adopted.
A strategy for computer modelling in geotechnical design
Authors: Bond A. J. , MacLeod I. A.
Published: November 2009

This paper presents a strategy for modelling engineering structures, based on a systematic process that distinguishes between engineering, conceptual, and computational models. Acceptance criteria should be established during model development to ensure that effective tests of these models can be formulated. The software used to analyse computational models should be evaluated on the basis of internationally recognised characteristics and the integrity and reliability of hardware should not be taken for granted. The roles that people play in this process are identified and discussed.
Elsewhere in ICE Proceedings
Authors: Bond A.
Published: November 2009

The following are summaries of papers published in other parts of ICE Proceedings that readers of Geotechnical Engineering may find of interest.
Improved site characterisation of contaminated land using pump-and-treat data
Authors: Dyer M. , van Zutphen M. , Hetterschijt R.
Published: November 2009

This paper presents findings fromthe back-analysis of a pump-and-treat operation for a site polluted with trichloroethylene (TCE).The groundwater extraction system had been installed to remove the historic spillage from a housing estate in the southern Dutch City of Tilburg.The spillage originated from a textile factory formerly located at the site.Over a period of seven years, continuous pumping of groundwater had failed to reduce significantly the annual extraction of TCE. As a result, the City of Tilburg was faced with ongoing remediation costs combined with concern over the full extent of pollution at the site and the long-term commitment for groundwater pumping. Between 1989 and 1996, the pump-and-treat system extracted approximately 4400 kg of TCE, with 570 kg of TCE being extracted in aqueous solution alone in 1996. Stagnation of the pump-and-treat operation led the municipal authorities of Tilburg to commission a feasibility project that would interpret the seven years of groundwatermonitoring data and provide a better understanding of the nature and extent of pollution beneath the housing estate. A three-dimensional groundwater model was developed for the site using the two finite difference programmes MODFLOWand MODPATH.The model linked changes in the direction of the groundwater flow caused by variations in pumping rates with fluctuations in the aqueous concentration of TCE recorded from monitoring wells.This enabled the remediation strategy to be refocused by either limiting the extraction of groundwater to themain source of pollution or to enhance the recovery of the pollutant using steam injection.
The status of the global positioning system for dam surface monitoring
Authors: Stewart M. , Tsakiri M.
Published: November 2009

Dam monitoring relies on the long-term measurement of small structural changes at regular intervals. Traditional surveying techniques and geotechnical instrumentation can effectively monitor one- or two-dimensional modes of motion. However, spatial distribution of geotechnical instrumentation is usually limited to the locations that the instruments can be installed during dam construction, while surface monitoring by traditional surveying techniques is a relatively slow process which restricts the number of points that can be regularly monitored. As a supplement to existing geotechnical instrumentation, the Global Positioning System (GPS) offers a reliable and efficient method for three-dimensional monitoring. To date, GPS technology has been successfully applied to a variety of deformation monitoring applications. This is due to its ease of use, and capability of very high accuracy when the appropriate hardware, software and field procedures are implemented. This paper reviews current GPS technology in the context of its application to dam deformation monitoring and the advantages and disadvantages of using GPS for this type of activity are discussed.
Experimental investigations of air sparging to control contaminated groundwater
Authors: Catney S. F. , Lynch R. J.
Published: November 2009

This paper investigates the feasibility of using air trapped in the pores of soil to reduce soil permeability and hence form a barrier to groundwater flow. The laboratory experiments carried out investigated: (a) how to inject air into the soil in such a way that contaminated water is discouraged from entering the air-injected (sparged) region; (b) what factors affect the airflow; and (c) whether the sparged region can deflect a plume of contaminant. It was found that this application of air sparging can be used to form a barrier to groundwater flow in laboratory scale experiments.
Briefing: Some observations on the influence of recent climate change on the subsidence of shallow foundations
Authors: Pugh R. S.
Published: November 2009

Since the introduction by UK insurers of cover for subsidence of the foundations to domestic properties in the early 1970s there has been a considerable rise in both the number of subsidence claims per annum and in the occurrence of claims surges related to clay shrinkage and periods of dry weather. The cost to date of the associated remedial works to shallow foundations runs to billions of pounds. The incidence of subsidence claims and claims surges over the previous three decades has been reviewed in relation to rainfall data from which it is concluded that both phenomena are closely linked to both rainfall deficits and to climate change. It is further concluded, on the basis of the historical data, that surges in subsidence claims can occur with little or no warning, irrespective of the antecedent soil moisture conditions. If current climate changes continue, the pattern of subsidence claims and surges is likely to continue. Whether or not recent events represent permanent climate change or normal variation is still very much open to debate.
Investigation of corroded stainless steel reinforcing elements in spent oil shale backfill
Authors: Winter M. G. , Butler A. M. , Brady K. C. , Stewart W. A.
Published: November 2009

Excavations for a new service installation in Lindsay Road, Edinburgh, revealed that the ferritic stainless steel reinforcements of the supporting reinforced earth retaining wall were, in parts, severely corroded. This paper presents the findings of an investigation into the cause of the deterioration of the wall. The results of chemical tests undertaken on the backfill indicate that the material was most likely unsuitable for the construction of reinforced earth structures with any of the types of metallic, reinforcement that are, or have been, commonly used. Ferritic stainless steels are now generally considered to be unsuitable for use in reinforced earth structures regardless of backfill type. Indeed, the use of the materials for reinforcements ceased within a few years of the construction of the wall at Lindsay Road. Surveys of the alignments of the wall have also been conducted. The surveys of the wall indicated that there was no measurable movement prior to demolition.
The use of compensation grouting in tunnelling: a case study
Authors: Lee S.-W.
Published: November 2009

At the London Docklands Light Railway Lewisham Extension (DLR-LWE) twin tunnelling project, compensation grouting was carried out beneath sensitive structures to prevent excessive settlement due to tunnelling. However, excessive grout injections might exert extra loads on the tunnels underneath. This issue has become a major concern for tunnelling and grouting contractors after a report by the UK's Health and Safety Executive in 2000, which listed grouting force as one of the possible factors that might have caused the collapse of the London Heathrow Express tunnels in 1994. This paper presents the extensive field monitoring data compiled by the tunnelling contractor on surface and building settlements as well as tunnel lining deformations caused by compensation grouting. It will be shown that the final corrected building settlements, incorporating compensation grouting, were about 5 mm. In the case of greenfield settlement the maximum observed settlement was less than 15 mm, a criterion specified by London Underground Ltd. The settlement trough parameters were found to deviate slightly from the proposed ones, probably because of the layered ground conditions. Field monitoring data revealed that the ground disturbance caused by the first tunnel construction had resulted in more ground settlement during the construction of the second tunnel. It was difficult to understand the observed modes of tunnel lining deformations caused by compensation grouting, owing to the monitoring techniques used and the layered ground conditions. Nevertheless, the maximum observed tunnel diameter change was only 8 mm, less than 1% of tunnel diameter change. In conclusion, the surface and building settlements as well as the tunnel lining deformations were all within the criteria specified by London Underground Ltd. This indicates that the tunnelling contractor had carried out good tunnelling work.
Foundation design for the refloat of the Maureen steel gravity platform
Authors: Broughton P. , Davies R. L. , Aldridge T. , Carrington T.
Published: November 2009

The Maureen Oil Field, located in the UK sector of the North Sea, was developed in the early 1980s, with the installation of the world's largest steel gravity platform, together with the installation of an export pipeline to an offshore concrete articulated loading column. Production in the field ceased in October 1999, and the facilities at the Maureen location were removed in the summer of 2001 as part of the decommissioning process. The largest element for removal and decommissioning was the steel gravity platform of about 1100 MN (110 000 t). This paper describes all the geotechnical engineering works, associated with the hydraulic skirt extraction/jacking of the gravity platform from the seabed, which were executed prior to the refloat and tow of the platform to deep water inshore moorings, together with a summary of results from the actual skirt extraction/jacking process, which was executed in June 2001.
Briefing: Geotechnical engineering and building research: the early days of soil mechanics at BRS—Part 4, 1948–1957
Authors: Penman A. D. M.
Published: November 2009

An essay on the foremost British government soil mechanics laboratory from earliest times to 1957.
Briefing: Excavations in gassy soils
Authors: Rowe R. K. , Goveas L. , Dittrich J. P.
Published: November 2009

Gassy soils are soils that contain gases under positive pressure. They can have a significant impact on the stability of excavations. This briefing note summarises two cases in southern Ontario, Canada, that highlight the importance of continued research into the behaviour of gassy soils.
A comparison between tube-à-manchette and lance grouting to assist tunnel excavation through chalk
Authors: Newman T. G. , Ingle J. L.
Published: November 2009

A road tunnel 13·5 m in diameter and 800 m long has recently been constructed, through chalk, as part of the Ramsgate Harbour Approach Road Scheme. For the first time in the United Kingdom tunnelling has involved primary support being provided by a system of prevaults followed by the installation of an unreinforced concrete lining. This paper describes how an iterative grouting solution was evolved in response to unstable ground conditions during the early phases of tunnelling. As the tunnel drive progressed, and greater knowledge of the engineering behaviour of the chalk was gained, decisions were made to carry out trial injections using the tube-àmanchette and lance methods. These were installed from the surface in areas where it was perceived that future problems might occur. A comparison is drawn between the efficiency and relevance of the two systems in the ground conditions encountered on site.
Recently in Canadian Geotechnical Journal
Authors: Driscoll R.
Published: November 2009

Published bi-monthly by the National Research Council of Cananda, Ottawa; circa 275 pages per issue. Current overseas, personal subscription: $246US, including airmail delivery. ISSN 0 008 367 4.

The Canadian Geotechinical Journal generally has a pleasing mixture of practical and theoretical papers covering soil and rock mechanics and engineering. The reader will not be surprised to find the occasional paper in French; the generous number of papers published in each issue will amply compensate the non-Francophone. Papers on soil behaviour tend to form the majority, while, as for many international Journals, there is a stated desire to publish case histories of practical application that is frequently fulfilled. Not suprisingly given the number of papers, there tends to be a voluminous Discussion section at the end. The following brief selection from the February and April 2002 issues gives a flavour of the Journal.
Briefing: Retaining walls built with scrap tyres
Authors: Sayão A. S. F. J. , Medeiros L. V. , Sieira A. C. C. F. , Gerscovich D. M. S. , Garga V. K.
Published: November 2009

A technique for building gravity retaining walls using scrap tyres is presented. This technique has been used successfully for stabilising natural slopes in Brazil. Experience with a 60 m long, 4 m high soil–tyre retaining wall in Rio de Janeiro is documented. The wall was built in horizontal layers, with scrap tyres tied together with rope or wire and filled with available local soil. Construction was monitored by displacement gauges and pressure cells in four cross-sections with different materials or dimensions for the wall. A 2 m soil surcharge was placed on the backfill, and the displacement responses at the four sections were compared. It is shown that the soil–tyre wall can be considered as an attractive alternative for slope stabilisation, because it combines the mechanical strength of tyres with the low cost of building materials such as local soil and scrap tyres.
Observations of ground and structure movements during site redevelopment in Dublin
Authors: Long M.
Published: November 2009

An extensive monitoring system was installed to provide data on the behaviour of some retained masonry façades and on ground movements, resulting from basement excavation, during the redevelopment of a prestigious site in Dublin. Observations made by electrolevel beam sensors have implications for future façade retention system design. They revealed a thermally induced daily cyclic movement of the retained façades, which was partially irrecoverable. This resulted in permanent total deformations of up to 100 mm. An extended archaeological dig exacerbated the situation. The masonry was subjected to angular distortions of up to 1 in 125—values that are close to the tolerable limit. These movements ceased only when the façades were tied into the new structure. The retaining wall and temporary works support system for the new basement proved extremely stiff and watertight. Lateral wall movements were at most 1 mm and were significantly less than those predicted before the works. Back-analysis of the performance of the retaining system suggests that the stiffness of the Dublin glacial deposits was underestimated. Level surveys showed little ground settlement, but only a relatively poor accuracy of ±3 mm was achieved. Only minor variations in groundwater level were recorded. Some minor effects, in the form of opening of cracks, were recorded on two sensitive adjacent buildings. Post-construction repair works easily overcame these.
The importance of visualisation of results from slope stability analysis
Authors: Renaud J.-P. , Anderson M. G. , Wilkinson P. L. , Lloyd D. M. , Muir Wood D.
Published: November 2009

Limit equilibrium methods are widely used for slope design applications, dynamically coupled hydrological-slope stability models and geomorphological investigations of long-term stability. Typically, computer codes generate a single minimum factor of safety and associated slip surface. Although this is attractive in that a single statement of stability is generated, such an approach ignores the many other slip surfaces that have been analysed, some of which may be capable of providing important additional information on the stability of the slope. In this paper the authors show that it is necessary to retain and visualise all slip surface information to determine the full extent of potential slope instability.
Electronic data transfer systems for field monitoring
Authors: Richards D. J. , Chandler R. J. , Lock A. C.
Published: November 2009

It is now recognised that modifying design procedures during the active construction phase of a project in response to the measured performance of key structural elements or ground movements can yield significant productivity and cost benefits. Site monitoring schemes implemented to record these measurements often generate a large volume of data, however the processing and dissemination of which are often complicated by incompatible systems or formatting conflicts between users. This paper describes the development and use of a data format protocol for the electronic transfer of processed site data, and of a web-based data visualisation system to test the robustness of the data transfer protocol.
Briefing: Geotechnical engineering practice and research in Hong Kong
Authors: Ng C. W. W. , Kong C. K. M.
Published: November 2009

In this briefing, the authors highlight some recent developments and research in slope and deep foundation engineering and in the university education system in Hong Kong.
Chalk anchorages: exhumation load transfer mechanism and design guidelines
Authors: Barley T. , Mothersille D. , Weerasinghe R.
Published: November 2009

An anchorage test programme carried out on the site of a deep basement construction in Norwich, UK, allowed the determination of anchorage capacities and creep characteristic data, and the exhumation of several anchor bodies in chalk. This paper reports on the performance of the chalk-based anchorages, the observation of exhumed grout body shapes and sizes, the extent of grout penetration into dissolution cavities, pressure-grouted fissures, and the formation of grout cake around the grout body periphery. Knowledge of construction techniques utilised for drilling, flushing, pregrouting, redrilling, pressure grouting and the general methods of control implemented to prevent dissolution cavity collapse has been related to the characteristics of the exhumed anchor bodies. Analysis of these grout bodies has allowed the proposal of a failure mechanism, comprising shaft resistance and shear of grouted fissures. Tests were carried out on both conventional and singlebore multiple anchors (SBMAs). Using short, fixed-length capacities with recently developed efficiency factors allowed accurate evaluation of the ultimate capacity of a typical 10 m fixed-length conventional anchorage. This design approach confirms that the SBMA system mobilised double the capacity of a conventional 10 m fixed anchor. Advancements in SMBA technology have enabled designs of 20 m fixed lengths, safely supporting working loads of 3000 kN.
Groundwater and ground movement around deep excavation
Authors: Pickles A. R. , Lee S. W. , Norcliffe B. A. W.
Published: November 2009

The Tsuen Wan West Station of Kowloon Canton Railway Corporation was constructed on both previously and recently reclaimed land. The project comprised approximately 600 m of cut-and-cover approach tunnels and a 400 m long station structure constructed in a 20 m deep excavation. Extensive instrumentation monitoring was carried out to monitor groundwater levels, ground movements and displacement of adjacent structures during the course of construction. This paper presents background information on the construction site and the monitoring results. It was found that the groundwater regime on the seaward side was strongly influenced by tidal movements throughout the monitoring period, whereas the landward groundwater regime showed a diminished tidal influence soon after construction of the diaphragm wall. Rock grouting carried out beneath the diaphragm wall was effective in mitigating drawdown of piezometric level outside the wall. The magnitude of the drawdown was found to be a function of diaphragm wall depth. Data on ground settlement, diaphragm wall deflection and groundwater were interactively discussed as the construction progressed. Finally subsurface settlement data were reviewed to highlight the adverse effect of pre-trenching for diaphragm wall construction and excessive drawdown in the weak rock layer.
Settlement prevision of piles under vertical load
Authors: Castelli F. , Motta E.
Published: November 2009

This paper presents a simplified non-linear method to predict the behaviour of a single pile and/or a pile group under vertical loads. The evaluation of the non-linear settlement is based on an incremental procedure taking into account the decrease of the stiffness parameters with increase of the applied load. The solution, derived first for a single pile, was extended to the case of a pile group, introducing an equivalent pier interacting with the surrounding soil by means of hyperbolic load transfer functions. To take into account group action in the soil–pile interaction, the stiffness of the equivalent pier has been modified and linked to that of the single pile, and a simple expression is also proposed. The numerical results obtained by the proposed method were compared with measurements derived from fullscale load tests on single piles and pile groups, and it has been shown that this procedure can be used successfully for prediction of non-linear pile group settlement. As the method can be easily coded or solved with the aid of a computer spreadsheet, reasonable predictions can be made without expensive and time-consuming analyses.
Geotechnical analysis of a retaining wall in weak rock
Authors: Richards D. J. , Clayton C. R. I. , Powrie W. , Hayward T.
Published: November 2009

The determination of realistic values of stiffness and in-situ horizontal stress is challenging in softer materials, but in weak rocks where discontinuities are typically present it is particularly difficult. Such difficulties were encountered during the site investigation for the construction of the A444 Coventry North–South road retaining structures, where the in-situ lateral stress and stiffness profiles of the weathered sandstones and mudstone were determined using a range of investigation techniques. A section of retaining wall incorporating a stabilising base was monitored during construction, and further investigation of the weak rock was undertaken using geophysical techniques. Aspects of the observed performance of the retaining wall during construction were analysed using a continuum finite-element method to provide a computed stiffness and initial horizontal stress profile. The results from these analyses are compared with the site characterisation data.
Briefing: Slope stability of earthfill dams: a case study of Kızılca dam
Authors: Keskin S. N. , Cavus U. S. , Yıldırım H.
Published: November 2009

It is well known that the construction of a wider impervious core for earthfill dams provides greater piping resistance and a greater resistance to earthquakes, which can cause internal cracks within the core. Also, designing a wide core can minimise construction defects. However, the core width and its location in earth or rockfill dams are actually determined by consideration of factors such as the type of material, piping resistance, geological features, cracking, earthquake considerations and stability requirements. In this study the influence of thickness of the impervious core and the magnitude of the earthquake coefficient on the stability of both upstream and downstream slopes of the Kızılca dam are presented. Because the clay core will be a compacted fill and the characteristics of the clay core material are very good, with high dry unit weights and permeabilities less than 10−10 m/s, hopefully there will be no problems of piping. There will be no seepage or stability problems with the geology of the Kızılca dam site; therefore the problem is only to determine the ultimate choice of the impervious core slopes from the point of view of maintaining the optimum stability of the Kızılca dam's outer slopes, to construct an economical impervious fill, and to determine whether or not the alluvium under the dam has to be removed. That is why, using conventional sliding surface methods, the stability analysis for sudden drawdown and full impounded water-level cases was performed for different core slopes with IV : IH and IV : 0·5H.
Interpretation of load tests on minipiles
Authors: Jeon S.-S.
Published: November 2009

This paper examines the results of 21 full-scale field tests on minipiles and synthesises the results into a convenient design procedure that incorporates both estimated axial displacements and soil properties. Both cohesive and cohesionless soils are included in this evaluation. For all practical purposes, the developed load–displacement relationship and the geotechnical soil properties for each minipile and soil type can be used to represent the available data well through normalised average values and empirical correlations.
Wastewater flow transfer tunnel: design and construction
Authors: Machon A. , Stevens S.
Published: November 2009

This paper discusses the design and construction of a 10·5 km long, segmentally lined, flow transfer tunnel. It covers the detailed lining and shaft designs, selection criteria for the tunnelling machines, shaft and tunnel construction methods, and specialist ground treatment. The paper discusses several construction problems encountered with shaft sinking and tunnelling, and describes how these were resolved. Particular note is made of caisson sinking of shafts and the design of the tunnel entry and exit portal eyes. Jet grouting in the varying ground strata around these portals and on other areas of the contract is considered.
Passive groundwater control system for a motorway
Authors: Farrell E. R. , Coppinger J.
Published: November 2009

Considerable public discussion was generated during the planning stages of a rural motorway in Ireland regarding the possible effects of the road drainage system on an ecologically important fen, which was about 5 km distant. To overcome this potential problem, a passive groundwater level control system was devised to limit the drawdown by maintaining the water levels 1·75 m above the road surface. This groundwater level corresponded approximately to the seasonal low water levels recorded in the aquifer prior to the construction of the motorway. This is achieved by constructing the motorway within a sealed cross-section with a permeable layer beneath this section, called the underdrainage system, which is connected to drains that outflow at the higher level. This underdrainage system controls the water pressures and flows beneath the sealed section. This paper presents the concept of the passive groundwater control system in a non-homogeneous glacial aquifer, and analyses the effects of this control system on the groundwater around the motorway. The selection of the design criteria and site control methods for the material within the sealed section is also discussed. The results of site monitoring that show the successful performance of the system in operation are also given.
Incorporating a fly-ash stabilised layer into pavement design
Authors: Bin-Shafique S. , Edil T. B. , Benson C. H. , Senol A.
Published: November 2009

This paper describes a case history where the structural support afforded by a fly-ash stabilised layer was accounted for explicitly during the design of two flexible pavements. Pavements were designed and constructed at two sites in southern Wisconsin employing a layer stabilised in situ with fly ash. One pavement is for a residential subdivision. The other is a test section located in a secondary highway that was recently reconstructed. A control test section employing a conventional cut-and-fill approach was also constructed in the secondary highway. Fly ash was used to increase the strength and stiffness of the fine-grained subgrade at both sites, which was soft prior to stabilisation. Pavements at both sites were designed using the 1993 American Association of State Highway and Transportation Officials (AASHTO) method for flexible pavements so that their structural number would be equivalent to that of the conventional pavement originally called for in the design. Measurements of California Bearing Ratio (CBR) and resilient modulus (Mr) were used with the correlation charts for granular sub-base materials in the AASHTO manual to define layer coefficients for the stabilised layers. Tests were also conducted on specimens collected during construction to verify that the in situ mixture had similar properties to those anticipated during design. The pavement at these sites is being monitored seasonally using a falling weight deflectometer and pavement distress surveys. The monitoring programme has indicated that the pavements constructed with fly-ash stabilised layers provide comparable stiffness to conventional pavements employing a cut-and-fill approach. No signs of distress have been observed in the pavements constructed with a stabilised layer. Thus, assigning layer coefficients for fly-ash stabilised soils based on correlations for granular sub-base materials appears reasonable until layer coefficients specific to fly-ash stabilised soils become available.
Cliff-top stabilisation of the Military Road, Isle of Wight
Authors: Wood H. J. , Fort D. S. , Clark A. R. , Robertson M.
Published: November 2009

This paper describes the development of the design for an innovative retaining structure built to support an existing highway on the Isle of Wight. At Afton Down on the south-west coast of the island the A3055 Military Road passes above high chalk cliffs. Continuing erosion at the toe of the cliffs led to the cliff edge receding to within 15 m of the highway. As a result options to maintain the road were investigated. A public inquiry ruled out realignment inland onto the adjacent downland, whilst measures to prevent erosion at the toe of the cliffs were unacceptable for environmental whilstcoastal management reasons. Consequently the road was kept open, with instrumentation installed to warn against failure of the cliff, and work began on the design of a scheme to maintain the road along its existing alignment. An environmental assessment was carried out to address the potential impacts of schemes on the adjacent downland, with the resulting arrangement of a tied retaining wall aiming to minimise these. Furthermore, outline methods for decommissioning the structure when it reaches the end of its serviceable life were identified. Planning permission was granted in 2002, and following a series of trials the scheme was constructed in 2003 and the road reopened to the public.
Assessment of suction measurements in saturated clays
Authors: Navaneethan T. , Sivakumar V. , Wheeler S. J. , Doran I. G.
Published: November 2009

Three laboratory methods of suction measurement were investigated: the pressure plate technique; measurement of positive pore water pressure after undrained isotropic loading in a triaxial cell; and the filter paper technique. Tests were performed on reconstituted and undisturbed saturated samples of four different clays. For these clays, the pressure plate method appeared to give the most reliable and consistent results. In the case of reconstituted samples, where the stress history was known, pressure plate measurements gave values of suction that were similar to, but slightly higher than, theoretically predicted values, suggesting slight compression of the water within the apparatus during application of the axis-translation technique. Values of suction measured by undrained loading in a triaxial cell were generally higher than measured in the pressure plate apparatus, suggesting a B value less than 1 (B is the pore water pressure parameter), and that use of a pressure plate is preferable even with ostensibly saturated samples. Filter paper measurements of suction were highly dependent on the calibration curve employed, emphasising the importance of deriving an appropriate calibration curve for the particular batch of filter papers being used. Using an appropriate calibration curve, filter paper measurements of suction on reconstituted samples showed good agreement with theoretically predicted values and were generally consistent with pressure plate measurements (although the variability was greater). Filter paper measurements of suction on undisturbed samples, however, were dramatically different from the other methods and often indicated impossibly high values of suction.
Ground conditions around an old tunnel in London Clay
Authors: Gourvenec S. M. , Mair R. J. , Bolton M. D. , Soga K.
Published: November 2009

This paper reports the findings of a field study of the ground conditions around an old tunnel in London Clay at a greenfield site in Kennington, South London. Ground conditions were identified from a borehole investigation incorporating a programme of in situ pore water pressure monitoring, geotechnical testing and sampling. Additionally, laboratory classification of the samples and a suite of high-quality triaxial tests were carried out. The results of this investigation are presented and discussed in conjunction with published London Clay data. The presence of a tunnel beneath the site allowed the investigation of its influence on the local soil and groundwater conditions.
Comparing CPT and pile base resistance in sand
Authors: White D. J. , Bolton M. D.
Published: November 2009

The comprehensive database of load tests on closed-ended piles in sand has been re-examined to study the relationship between CPT resistance, qc, and ultimate base capacity, qb. The aim is to establish the origin of low reported values of qb/qc which contrast with continuum models that suggest qb = qc for steady deep penetration. Partial embedment of the pile tip into a hard layer underlying weak material has been accounted for by weighting qc. Partial mobilisation has been accounted for by defining failure according to a plunging criterion. When these two mechanisms are considered, the resulting values of qb/qc have a mean value of 0·90 and show no trend with pile diameter. The remaining slight underprediction of the ‘continuum’ model (qb = qc) could be attributed to the underestimation of plunging load in pile tests for which steady penetration is not reached. This exercise makes two contributions: first, it is suggested that any reduction of qc when estimating the end bearing capacity of closed-ended piles in sand should be linked to partial embedment and partial mobilisation, rather than absolute diameter; second, the dearth of high-quality pile load test data in the public domain is highlighted.
Evaluating permissible subgrade rut depth in pavement design
Authors: Hau K. W. , McDowell G. R.
Published: November 2009

In the design of a pavement, the permissible rut depth and permissible resilient vertical strain at the top of the subgrade at the end of the construction stage (i.e. before the placing of the bituminous layer) are used to select the appropriate thickness of granular material. However, usually the only available data for the subgrade is the resilient modulus, which is estimated from the California Bearing Ratio. This paper examines the application of a new three-surface kinematic hardening model for the subgrade in a finite-element analysis to evaluate the rut depth and resilient vertical strain at the top of the subgrade at the end of the construction stage. The resilient modulus for the subgrade is determined by examining the stress changes at different depths in the subgrade, for different thicknesses of granular material, and applying such stress changes to simulated triaxial samples for 50 cycles to compute the resilient modulus at different depths for input to a layered elastic analysis, in order to compute the resilient strain at the top of the subgrade. This is used to estimate the required thickness of granular layer based on the allowable subgrade strain, and it is found that a realistic thickness is obtained. The new three-surface kinematic hardening model is also used to calculate the rut depth at the end of construction for different thicknesses of granular material, and the permissible rut depth criterion is used to select the required thickness of granular material. A realistic thickness is also obtained using this criterion, so that, by using the new kinematic hardening model, the permissible rut depth and subgrade strain criteria are seen to be consistent. The model is then applied to a thinly surfaced pavement to investigate the effect of the thickness of granular material and asphalt on the predicted rut depth.
Ground movement monitoring at King's Cross Station, London
Authors: Beth M. , Obre X.
Published: November 2009

The redevelopment of King's Cross Station in central London includes the construction of a new Northern Ticket Hall and tunnelled connections to existing infrastructure. These works are to be carried out beneath a congested site including Grade I and II listed buildings, and heavy rail and road traffic both above and below ground (three London Underground lines). Arup and Soldata were required to design and implement a monitoring solution that would assist with the management of the risks. A direct and unique contract from the client to the instrumentation specialist was set up in order to keep a tight control on the data quality, and to ensure an optimal distribution of the results. A real-time system, based on an automated total station network combined with standard monitoring methods (inclinometers, precise levelling, etc.), was chosen. The detailed design and optimisation of such a system involves estimating the precision based on site-specific information. Since installation on site, the site monitoring data have shown the adequacy of the design, with the estimated field precision easily attained, and in some cases well exceeded. The main conclusion is that, with adequate care, the design and implementation of a large monitoring system can lead to fruitful results that are reliable, rapid and accurate.
Yielding mechanisms in a rectangular trench
Authors: Lei G. H.
Published: November 2009

In geotechnical engineering, stability of the openings formed by excavation is of much concern in controlling the design feasibility and construction workability of underground structures. Analysis of the stability of the excavated openings and the corresponding measures against instability inevitably necessitate a good understanding of the yielding and failure mechanisms of the openings. This paper proposes a mechanism of potential yielding across an excavated rectangular diaphragm wall panel trench. By using an elastic analytical solution to the problem of horizontal stress changes and displacements induced during the installation of a rectangular diaphragm wall panel, two extreme cases (panel trenches with dimensions 1 m × 1 m and 6 m × 1 m) have been analysed to investigate the distribution of the principal stress change of the soils around the trenches due to excavation. It has been found that, when the elastic limit is reached, soils with different consolidation histories will exhibit different yielding modes—either active yielding around the faces of the excavated trench for normally consolidated soils or passive yielding around the ends of the excavated trench for overconsolidated soils. The proposed mechanism has been supported by some reported experimental results.
A field investigation of vertical footing response on sand
Authors: Gavin K. , Adekunte A. , O'Kelly B.
Published: November 2009

This paper presents the results from an experimental programme that studied the factors affecting the bearing resistance of shallow footings in sand. In particular, the tests considered the effects of the footing width and embedment depth on the pressure–settlement response. By comparing the results with field tests on full-scale footings, simple correlations between the bearing pressure mobilised at normalised settlement levels of 5% and 10% of the footing width and the cone penetration test qc value were studied. These correlations were found to be independent of footing size, embedment depth and sand state, although they were affected by creep. The rate of mobilisation of the footing resistance at low settlements was found to be strongly dependent on the initial soil state and the previous loading history. A simple non-linear elastic soil model was found to adequately predict this response.
Seismic design factor for sliding of waterfront retaining wall
Authors: Ahmad S. M. , Choudhury D.
Published: November 2009

A detailed methodology is presented for obtaining seismic design factors for sliding of a waterfront retaining wall using the pseudodynamic approach, which considers the effects of period of lateral shaking, shear and primary wave velocities, time, and seismic accelerations. Water is considered on both the upstream and downstream sides of the wall. Results are presented in terms of design factors for sliding: thrust factor FTwet, inertia factor FIwet, and the combined dynamic factor FWwet. Using FWwet, the weight of the wall needed to maintain stability against sliding under seismic conditions is obtained. The variation in upstream and downstream water heights seriously challenges the sliding stability of the wall. Variation in the horizontal and vertical seismic acceleration coefficients, soil and wall friction angles, and period of lateral shaking have a significant effect on the stability design factors, whereas the effect of pore pressure ratio was found to be a minimum. The weight of the wall needed for a kh of 0·3 is almost double what would be needed if kh were zero. Comparison of results shows a good match with an existing methodology, but for the dry backfill case with no upstream water. Results for the wet case are claimed to be unique.
Effect of filling materials on physical and mechanical properties of travertine
Authors: Karaca Z.
Published: November 2009

The experimental work presented in this paper was aimed at studying the influence of different filling materials on the physical and mechanical properties of Classic Travertine, from Denizli in Turkey. Unfilled core specimens, and specimens filled with cement, mastic, polyester or epoxy, were used as test samples. All samples were tested under uniaxial and triaxial loading to determine their compressive strength, Young's modulus, Poisson's ratio, cohesion, and internal friction angle. It was observed that different types of filling material improved the physical and mechanical properties of the unfilled travertine at different rates.
Improvement of granular soils by high-energy impact
Authors: Chow Y. K. , Yong D. M. , Yong K. Y. , Lee S. L.
Published: November 2009

A recently developed wave equation model for analysing the improvement of granular soils by high-energy impact is used to perform a parametric study to investigate the ground response during dynamic compaction. The important parameters investigated include the pounder base area, pounder weight, drop height, number of drops and initial soil properties within the practical range in a dynamic compaction project. This study provides a better understanding of the influence of the various parameters studied on the ground response during high-energy impact. The characteristic curves developed will enable a design engineer to determine the crater depth, and level and depth of soil improvement that will facilitate the selection of operational parameters.

On utilise un modèle d'équation d'onde mis au point récemment pour l'analyse de l'optimisation de sols granulaires par impact à é nergie é levée, pour effectuer une é tude paramétrique afin d'établir la réponse du sol au cours du compactage dynamique. Parmi les paramètres importants qui sont examinés, on indiquera la surface de base du bocardage, le poids du marteau à bocarder, la hauteur de chute, le nombre de chutes et les propriétés initiales du sol dans les limites de la plage utile d'un project de compactage dynamique. Cette é tude permet de mieux comprendre l'influence des différents paramètres é tudiés sur la réponse du sol aux impacts à é nergie é levée. Les courbes caractéristiques tracées permettent au concepteur de déterminer la profondeur du cratère ainsi que le niveau et la profondeur de l'optimisation du sol qui permettra de faciliter la sélection de paramètres d'exploitation.