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Long-term heave of basement slabs is a significant problem in cities with overconsolidated clay, such as London. There is a dearth of data to calibrate the methods commonly used by designers to predict heave displacement and swell pressure. This paper presents results from two centrifuge tests aimed at reproducing the phenomenon of long-term basement heave. Reduced scale models of rectangular basements with different slab thicknesses underlain by overconsolidated clay were tested, to investigate the effect of base slab stiffness on heave behaviour. The centrifuge tests provided measurements of the profiles of vertical displacement, bending moments in the slab and contact pressure at the slab–soil interface. This is the first geotechnical centrifuge study to provide simultaneous measurements of vertical displacement and swell pressures during long-term basement heave. Whereas the flexible basement underwent significant differential heave and almost complete relaxation of swell pressures, the stiff basement generated large swell pressures and consequently large bending stresses. These results confirm that the prediction of high heave pressures is a self-fulfilling prophecy: a basement slab with high stiffness will beget large swell pressures. The experimental measurements of swell pressure and heave were compared to predictions by a simplified non-linear method of heave calculation. The simplified non-linear method produced acceptable predictions of total heave. [ABSTRACT FROM AUTHOR]

The paper investigates the effect of hydrated lime on shear strength properties and behaviour of London clay, triaxial. Unconsolidated undrained tests were performed to identify the effect of lime dosage, compaction water content and curing time on the shear strength and stress–strain behaviour of the treated soil. The mineralogical and physicochemical transformations occurring during the curing of the soil were also monitored. The results showed that strength gain was strongly influenced by lime content and the curing period, whereas compaction water content was less influential. It was found that the strength evolution is likely to continue over long periods of time and result in very considerable strength gains on the hardening of pozzolanic reaction products. It was also shown that adequate early strength gains can be obtained with reduced material consumption, thus further increasing the sustainability of the treatment processes. The paper also highlighted the importance for engineering design of considering the brittle stress–strain response of the lime-treated soil, and the benefit of using lower amounts of lime to alleviate this undesirable effect. The implications of various aspects of soil brittleness in different situations merit further attention and should be explored by way of modelling in future work. [ABSTRACT FROM AUTHOR]

Climate projections suggest that the UK will be increasingly affected by climate-induced hazards in the future, exacerbating the potential for multihazard events to occur. This paper explores the extent to which climate resilience is being embedded in current and future rail transport infrastructure projects in London through use of a multihazard approach. It concludes that a multihazard approach is a relatively new concept and is therefore not currently being considered widely. However, opportunities for decision makers to explore its value to mitigate climate risks through collaborative working and further research exist – this paper recommends that two main stages are required to achieve this. Route 1 requires climate/hazard experts to identify and characterise the different hazard interactions that could occur, including their impact on the UK/London. Following this, route 2 involves the creation of multidisciplinary workshops to identify any multihazard vulnerabilities associated with different rail assets – potentially highlighting areas where further research is required. The paper concludes that although a London rail context has been adopted in order to understand the relevance of a multihazard approach, there is opportunity for it to be considered across many different sectors in the UK and the wider civil engineering industry. [ABSTRACT FROM AUTHOR]

This paper describes the interaction of the Crossrail project to deliver London's new Elizabeth line in the UK with a building situated directly over the machine-bored tunnels, close to Paddington station. The initial scheme called for the demolition of the existing building at 4–18 Bishop's Bridge Road, including extraction of existing piles, which would have had a considerable impact on the local area. Changes in the design of the Elizabeth line station at Paddington allowed a revised strategy to be considered, whereby the building could be kept, reducing construction costs to the project considerably. A combination of desk study and ground investigation works was used to identify the likely extent of the piling under the building, and to predict the risk of clashes with the tunnels. The results of analyses considering the impact of construction works on the building, and associated monitoring results are presented. The decision not to demolish produced numerous benefits aside from the reduction in cost, including a considerably reduced impact on those using the building and adjacent areas. [ABSTRACT FROM AUTHOR]

The energy pile test at Lambeth College, London was first reported just over 10 years ago; however, the original appraisal of the test only looked at the thermal response at the end of extended cooling and heating stages, and did not examine the transient response within these stages or in the daily cyclic thermal loading stage that followed. This paper revisits the earlier results, allowing for concrete creep under sustained load and using a revised strain-dependent pile modulus. The strong influence of the latter and the possible importance of stiffness changes during load reversal is highlighted. Detailed evaluation of the long-term transient results suggests that within a given thermal loading interval the thermal effects are similar, but there is some further discrepancy in the results, possibly due to an underestimation of the concrete creep. This re-evaluation has mitigated pile head displacement and increased thermal stress in the cooling phase, with the reverse occurring in the heating phase, and appears to be in better agreement with back-analysis reported by others. The transient response within the thermal loading stages illustrates that the development of the thermal stress–displacement response is related to the time for heat to diffuse through the pile body – around 3 days in this case. [ABSTRACT FROM AUTHOR]

As cities work to reduce their total greenhouse gas (GHG) emissions, the transportation sector is lagging, accounting for a growing percentage of total emissions in many cities. The provision of public transit, and specifically urban rail transit, is widely seen as a useful tool for reducing urban transportation GHG emissions. More research, however, is needed to understand the net impact of new metro rail infrastructure on urban emissions and guide efforts to maximise the GHG savings through rail investments. This paper examines the net GHG emissions of the Jubilee line extension (JLE) in London, UK. The GHG emissions associated with construction, operation, ridership and changes in urban density associated with the provision of the new metro rail infrastructure are assessed. These components are then combined and compared to calculate the net GHG impact across the study period, which extends from opening in 1999 through 2011. The capital GHG emissions from construction of the JLE are calculated as 530 kilotonnes carbon dioxide equivalent (CO2e). The initial mode shift from other rail lines and long-term mode change from automobiles result in yearly GHG savings from riders on the JLE. A quasi-experimental analysis of land-use change near the JLE finds no calculable GHG saving from increased residential density. The GHG payback period is calculated between 13 and 19 years. [ABSTRACT FROM AUTHOR]

Office buildings require a significant amount of energy for heating and cooling purposes. A possible strategy for reducing this energy in order to reduce carbon dioxide emissions and operational costs is to specify high-performance facades. However, their benefits remain unclear for UK conditions with mild winters and cool summers. This paper reports on an investigation on the energy demand of offices in London, UK, incorporating facades with U-values between 1·2 and 2·6 W/(m2 K) and g-values between 0·3 and 0·5 using the dynamic simulation tool Tas. Other variables considered included climate change (using the Chartered Institution of Building Services Engineers' future weather data files), low internal gains, long working hours and office orientation. It was found that, apart from the case when internal gains are low, cooling is overwhelmingly necessary and energy usage increases with decreasing U-value and decreases with decreasing g-value. Low-U-value facades act to reduce conduction heat losses, thereby increasing energy use. Conversely, low-g-value facades act to reduce solar heat gains, thereby reducing the energy required for cooling. The results are used to highlight deficiencies in The Building Regulations 2010 and where more advice would be of benefit. The paper also discusses the merits of a number of strategies for reducing energy use in office buildings. [ABSTRACT FROM AUTHOR]

This paper describes the redevelopment of Calder's Wharf, London, a four-storey block of residential units. As part of this redevelopment a detailed finite-element and ground movement analysis was undertaken to establish the potential impact of the proposed structure on two Docklands Light Railway (DLR) tunnels that run directly below the site and beneath the footprint of the proposed development. The case study presents the as-constructed displacements within the tunnel lining and compares these real-time measurements with the predictive models used in the engineering design. The analysis indicated that stress changes over the long term on the tunnel linings were of the order of 5 kPa maximum. This is equivalent to an increase in depth of the tunnel of 0.25 m and was not considered to be material to the tunnel. [ABSTRACT FROM AUTHOR]

This paper describes a case history associated with the design of a building scheme at a site in Mayfair, London situated directly above the existing London Underground's Victoria Line tunnels. It confirms how this important constraint of the presence of the tunnels, influenced the design and how the railway protection measures were agreed and implemented. It explains the development of the feasibility scheme, the detailed design of a raft foundation solution, the retained façade scheme and the requirement to limit settlement, thus restricting the effect on the existing tunnels. It shows that predictions of heave due to demolition, and settlement due to construction, were assessed as realistic and compared favourably against actual monitoring results obtained during the works. The paper suggests 'best practice' when achieving railway protection measures for building structure design and provides recommendations for future projects above existing tunnels. [ABSTRACT FROM AUTHOR]

Bridge D70 is a single-span steel plate girder bridge dating from the 1930s. It carries four tracks of London Underground's District and Piccadilly lines, the latter being one of the capital's main rail links to Heathrow Airport. Situated next to Chiswick Park tube station the bridge spans over a busy traffic route. This paper describes the project as part of the public private partnership contract to modernise the London Underground system. The paper describes the reasons why upgrading of the existing structure was chosen over complete renewal. The primary aims during the works were to avoid unnecessary closure of the railway line, to minimise the risk of unplanned disruption and to protect the safety of the travelling public. The paper explains the method of construction and the constraints on carrying out work to an existing bridge while in service to passenger trains. This required the extensive use of temporary works to support the tracks. It also describes the challenges in refurbishing a bridge in a residential area in terms of access to the site and reducing the environmental impact of the work. The designer and project manager was Metronet Rail SSL, and the main contractor was Edmund Nuttall (BAM Nuttall). [ABSTRACT FROM AUTHOR]

Due consideration of non-linear soil stiffness is one of the essential requisites in many geotechnical applications. A considerable amount of the geotechnical literature, as well as numerous recent studies, have been directed towards enhancing our ability to formulate mathematical relationships expressing the stiffness non-linearity of fine-grained soils and to determine the controlling parameters of such relationships. At present, the parameters of the non-linear clay stiffness formulations are commonly correlated to Atterberg's plasticity index (PI), even though this is obtained from testing remoulded samples, whereas the looked-for parameters are distinctly related to the undisturbed clay condition. In this paper, a new approach is proposed to establish the link between the non-linear stiffness parameters and the undrained rigidity index, as a more pertinent factor for the undisturbed compressibility of clays than the PI. The proposed approach was used to predict the undrained non-linear behaviour of several well-reported formations (London Clay, San Francisco Bay Mud, Skå-Edeby Clay and Hachirougata Clay). Good agreement between the predicted and the measured non-linear stiffnesses was found, implying that the presented methodology can be broadly applicable to different clay formations. [ABSTRACT FROM AUTHOR]

Historically, maintenance of the surface water track drainage system serving the London Underground (LU) was limited to discrete like-for-like repairs in response to deteriorating asset condition. The use of modelling software to gain an accurate understanding of the hydraulic performance of the system has been limited by incomplete and often inaccurate data, due to the fact that the railway was constructed in parts over many decades and contains numerous peculiarities. This paper uses the LU track drainage modelling project (encompassing the Central, Circle, District, Hammersmith and City and Metropolitan lines) as a case study to demonstrate how seemingly unmanageable quantities of disparate data can be brought together to produce hydraulic models that provide significant benefit in informing maintenance activities and asset renewal programmes. [ABSTRACT FROM AUTHOR]

Many clay railway embankments in the UK are well over 100 years old, and now suffer from a range of stability and serviceability problems. A common means of remediating earthworks that have either suffered, or are assessed as being at risk of, deep-seated slope failure is to install a row of discrete piles along the mid-slope. This paper presents field data from a 9 m high, pile-stabilised embankment at Mill Hill, north London. Initial pore water pressure measurements had shown that the trees present on the earthwork maintained low pore water pressures during winter; thus the trees were left in place after piling to aid stability. The piles initially bent upslope, as a result of inward shrinkage of the embankment over a period of dry weather, before then being loaded by shallower downslope movements of the clay. Later cycles of seasonal movement caused a small but gradual ratcheting upward of pile bending moments. The largest bending moments measured over 6 years of monitoring were those resulting from the initial inward shrinkage of embankment, which reached about 25% of the design capacity of the piles. At the end of the monitoring period, the measured bending moments resulting from shallower downslope ground movements were about 20% of the pile design capacity. [ABSTRACT FROM AUTHOR]

Encouraging children to walk to school has become an important issue. Government agencies are therefore keen to reduce child pedestrian casualties associated with the school journey. One way forward is to provide each catchment area with a system of designated routes that minimise road accident risk for pupils on foot. However, there is no accepted modelling procedure for identifying safe routes. This paper reviews the obstacles and assesses the potential for ad hoc solution methods, using the road network surrounding a primary school in north London as a test bed. Solutions close to the optimum were obtained by transforming the network to a simpler form and by modifying the objective function, which effectively linearised the problem. This paper assesses the sensitivity of the results to various assumptions and uncertainties in the data, and concludes with a brief comment on the prospects of finding safe routes on a routine basis at local authority level. [ABSTRACT FROM AUTHOR]

The front-shunt tunnel was the first tunnel of the Terminal 5 project at Heathrow to be constructed, and was the first section of sprayed-concrete-lined (SCL) tunnel to be constructed using the method known as LaserShell. This innovation represented a significant deviation from the methods previously used in SCL construction. Therefore it was subjected to a careful examination before and during construction using sophisticated 3D numerical modelling and monitoring during construction. The paper presents typical results from surface settlement levelling, inclinometers and extensometers, pressure cells and tunnel lining displacement measurements, and comments on the performance of the methods and instruments used. The paper then presents the methodology and typical results of the numerical modelling, and shows that the predictions of displacements and stresses compared well with the field measurements. In terms of the control of ground deformations and structural safety the tunnel performed well. [ABSTRACT FROM AUTHOR]

The Thames Tideway tunnel is a large sewer running up to 66 m below the tidal river Thames in London, UK. Its construction, started in 2016, was urgently needed to protect the tidal Thames from pollution due to the combined sewer overflows of untreated sewage that every year are spilled into the river. This paper reports on an exercise for evaluating the environmental impact associated with the construction process of the east section of the tunnel quantified by means of a life-cycle assessment, which not only primarily considered carbon dioxide emissions, but also took into account a wider series of impact categories. Operational and decommissioning impacts were not included. The results indicated the processes with the greatest effects on the environmental performance of the east sector construction and hence where alternatives on the design or materials used needed to be considered. [ABSTRACT FROM AUTHOR]

Building monitoring and protection are important components of underground projects in urban areas. Typically the procedures applied for the assessment of settlement-induced damage to buildings are based on simplified assumptions that do not take into account soil–structure interaction. Assessment methods based on the relative stiffness between the structure and the soil exist, but they are rarely applied in practice due to concerns about the accuracy and reliability. The primary aim of this work is to use the large amount of monitoring data provided by the Crossrail project in London to improve understanding of building performance and existing damage assessment methods. The paper gives an initial overview of the available monitoring data by presenting four representative case studies for load-bearing masonry buildings on shallow foundations. Structural data are then used to evaluate the consistency of predictions produced by different relative stiffness formulations. The results show the effect of building stiffness on the soil surface settlements and clarify the effects of various assumptions made during prediction. The conclusions highlight opportunities to improve prediction procedures and the need for more detailed monitoring data for future tunnelling projects. [ABSTRACT FROM AUTHOR]

The planning of major sporting events now requires serious consideration to be given to legacy. This paper examines the nature of legacy planning and how its importance is now recognised by both bidding teams and event planning bodies. The concept of legacy is shown to be broad, encompassing economic, social, cultural, environmental, sporting and political impacts. Several examples of good and less good practice in respect of legacy planning are examined and a detailed review of how London's 2012 organisers are learning the lessons of past major sporting events is presented. To maximise the impact of legacy for major events, this paper suggests it is critical that the legacy vision—a clear articulation of legacy benefits—is in place well in advance of the event. Six ways in which legacy benefits can be secured for major sporting events are recommended: articulating the vision for legacy development as early as possible; legacy business case evaluation; attracting private sector funding for legacy development; the delivery of venues that meet the legacy aspirations of all stakeholders; coordinated venue management and operation; and rigorous evaluation of the wider socio-economic legacy. [ABSTRACT FROM AUTHOR]

This paper describes the nature of ground movement observed during construction of the Jubilee Line Extension at St James's Park and beneath Elizabeth House for different stages of tunnelling in London Clay, using open-face shield construction and sprayed concrete linings respectively. Volume loss is defined as the volume of ground loss as a proportion of the final tunnel volume and is measured in the plane of the tunnel. Volume losses corresponding to different phases of tunnelling at St James's Park and beneath Elizabeth House are identified in the paper. A companion paper presents a new approach to estimating volume losses for each phase of open-face tunnelling in London Clay. [ABSTRACT FROM AUTHOR]

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

During bridge design and assessment, effects of thermal actions are accounted for by means of a uniform temperature variation and temperature difference components. The uniform temperature variations cause changes in length and width of the structure, whereas the temperature difference components primarily cause curvatures and internal stresses. The effects of these strains on the superstructure depend on the structure's articulation and restraint. Design profiles used to model the temperature difference components vary between design codes, which can have a significant effect on the induced curvatures. Thermal data findings obtained from a comprehensive, year-long monitoring programme on Waterloo Bridge in London are examined, which allows comparison of these various models with performance data. The design thermal model in BS EN 1991-1-5 is examined, supplemented by the models from the Aashto and New Zealand codes. The measured uniform bridge temperature generally fell within the stipulated limits of BS EN 1991-1-5; however, at low temperatures the minimum deck temperature may be lower than the design relationship provided. The resultant moments implied from the measured vertical profiles: significantly exceed the worst-case values predicted by the UK model; exceed the Aashto model at different bridge sections; and do not exceed the New Zealand model. [ABSTRACT FROM AUTHOR]

High-quality rotary core samples of natural London Clay were taken during installation of subsurface instrumentation to monitor the ground response at Hyde Park, London, to the construction of Crossrail tunnels. An extensive programme of advanced triaxial tests was performed on specimens from London Clay divisions A3 to C. Detailed analysis of their response to undrained shearing in compression from their estimated in situ stress state provides new insights into the magnitude of and changes in stiffness at small- and medium-strain levels. A consistent trend in the variation of small-strain stiffness with depth and lithological division is established for the Hyde Park research site. Differences between the stiffness magnitudes from this investigation and those reported earlier by others are shown to be a result of the conditions before and during undrained shearing, particularly the ratio of shearing axial strain rate to the preceding creep strain rate. This provides an explanation for significant discrepancies in small-strain stiffness values reported in recent years, which have led to uncertainties regarding which values to adopt, particularly for numerical analysis applications. Understanding the relevance of the axial shearing to creep rate ratio allows for improved triaxial testing techniques and the subsequent interpretation of the test data. [ABSTRACT FROM AUTHOR]

A part of the 'current trends in municipal engineering' feature, this paper is a case study concerning the site assembly and comprehensive redevelopment of contaminated land. The site is in fragmented ownership and comprises mainly run-down commercial premises, many vacant or derelict, that have seen little investment for many years and is severed by six east-west public roads along its length. Because the site, in East London, aligns with one of the Mayor's strategic objectives there is a strong case for enabling development owing to its proximity to a public transport interchange. Through the intervention of the London Development Agency and a design brief for the site a compulsory purchase order was brought about comprising approximately 2?4 ha. There is a considerable body of policy support for the regeneration of urban areas in decline, emanating from national government policy cascading down to local level. There is a compelling case for the regeneration of the compulsory purchase order land and common consent that the compulsory purchase order site is in a state of severe decay and continuing decline. It has a seriously adverse impact on the immediate area for a combination of reasons. [ABSTRACT FROM AUTHOR]

Copyright of Géotechnique is the property of Thomas Telford Ltd and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Géotechnique is the property of Thomas Telford Ltd and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

A modification to the load factor approach to estimating undrained volume loss for open-face tunnelling in London Clay is proposed. The modified approach is based on the nature of ground movement observed during construction of the Jubilee Line Extension at St James's Park and Elizabeth House for different stages of open-face shield tunnel construction and tunnelling using sprayed concrete linings, described in a companion paper. The new approach is shown to provide good estimates of the volume loss observed for open-face shield tunnelling in London Clay at Green Park and Regents Park. [ABSTRACT FROM AUTHOR]

To meet Government targets for the building of infrastructure and new homes, particularly in London and the South East, redundant brownfield sites will need to be rapidly brought into use. This paper describes the challenges surrounding these aspirations, specifically the problems that accompany brownfield developments. These are outlined by reference to specific building projects undertaken by St George during its 17 years of developing in London, on brownfield sites. The paper also describes the company's areas of research and concludes by making recommendations for the future. [ABSTRACT FROM AUTHOR]

Copyright of Géotechnique is the property of Thomas Telford Ltd and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

For several forthcoming tunnelling projects circular shafts will need to be constructed in London. Better understanding of their behaviour could result in more reliable movement predictions and efficient designs. A previous large-scale monitoring scheme of Thames Water's Abbey Mills shaft provided measurements of diaphragm wall deflections and bending moments. In this paper, the results of a parametric study in Flac2D are compared with the field data to understand the shaft's performance during construction. Very small wall movements are calculated and are confirmed by the inclinometer data. Previous researchers have proposed that the joints between the diaphragm wall panels reduce the circumferential wall stiffness. Out of several simulations with reduced hoop stiffness, the results obtained from the isotropic wall, that is, with strong joints, give closest agreement with the field measurements. In the initial design, the Chalk was allowed to yield below excavation level, but the field data indicate elastic behaviour. The elastic Chalk caused the wall to bend more sharply at the excavation level and hence bending moments exceeded the design predictions. Further simulations show that the wished-in-place assumption with a of 1·0 in the Chalk was appropriate, and that, when the wall installation is modelled, the applied bentonite and wet concrete pressures during the construction process govern the performance of the shaft wall. These findings provide valuable information for the construction of future shafts in a similar geological setting. [ABSTRACT FROM AUTHOR]