Apparatus for centrifuge modelling of top down basement construction with heave reducing piles

The construction of deep basements in urban areas is associated with many risks and problems among which is the possible damage to existing structures and services resulting from settlements near the excavation. A number of methods are routinely employed to attempt to control these movements (e.g. top-down construction, use of stiff diaphragm walls). This paper discusses the methodology and practicalities of a series of centrifuge model tests designed to investigate the effect of deep basement construction. Two sets of experimental apparatus are described in detail and their effectiveness in terms of robustness and generation of repeatable data are assessed. It is shown that using relatively simple techniques and equipment it is possible to model many of the features associated with top-down construction

Influence of geometry on the bearing capacity of sheet piled foundations

Bored concrete piles are commonly used to support moderate loads from buildings in urban areas. At the end of their 25-30 year lifespan these structures are decommissioned but their foundations are left in place. These cannot be inspected hence the bearing capacity cannot be accurately verified. A hybrid foun- dation comprising sheet piles and a pilecap to mobilise shaft friction and end bearing was demonstrated to be a feasible and sustainable alternative to cast in-situ concrete piles. This research investigated the influence of sheet pile geometry on ultimate bearing capacity. A centrifuge test at 50 g was performed in over- consolidated clay where a square hybrid sheet pile group was ax ially loaded and vertical settlements recorded. Results indicated a square sheet pile group offers 70% greater capacity than a circular sheet pile group of similar surface area and 24% improved performance over the solid p ile loaded in the same test. Analysis of results suggested that the ultimate bearing capacity of the square sheet pile group compared with a solid pile of equivalent base area were within 0.2%, emphasising the importance of shape on capacity and the feasibility of the hybrid system as a viable foundation solution

Plate bearing tests for working platforms

During piling and other construction works, a working platform is often constructed across the site. These platforms comprise aggregate material placed and compacted to a designed thickness. Satisfactory performance of the platform may be confirmed by a plate bearing test. Current guidance given on plate bearing testing of granular soils suggests that the plate be at least five times the nominal size of the coarsest material. For a working platform this may be large and the reaction load required from plant and resources to carry out the bearing test may become excessively high. The aim of the research presented in this paper was to investigate the effect of particle to plate size ratios to establish if the use of a smaller plate would still allow a reliable test to be performed on site. Plate bearing tests were carried out in a centrifuge using a large, coarse grained limestone. The limestone was graded to a scale representation of 6F2 material, a commonly specified particle size distribution for working platforms. The size of plate was varied and the load displacement response recorded. The measured bearing capacity was correlated with the ratio of particle to plate size

Bearing Capacity of Sheet Piled Foundations

Bored concrete piles have been used widely on commercial developments in London for about the last 50 years. The life of a commercial building is between 25 – 30 years and, as each building is demolished and rebuilt, the piles from the previous buildings remain in the ground causing obstructions to the new foundations. This paper describes a preliminary study to explore the viability of sheet piled foundations as a genuine alternative to cast in situ concrete piles and all of the complications inherent in their construction and the obstruction they create to subsequent foundations. If it is possible to use steel piles as foundations they can be easily removed, recycled and will not cause obstructions for future developments. However, individual sheet piles have relatively low capacity when axially loaded and it is therefore necessary to consider a sheet pile group in conjunction with a pilecap, which can be considered a hybrid foundation; a combination of shallow (pilecap) and deep (sheet pile). A short series of centrifuge tests is reported in which model sheet pile groups in over-consolidated clay were loaded axially whilst vertical displacements were measured. Equivalent cast in place piles were similarly tested alongside the sheet pile groups by way of comparison

Test development for the investigation of soil disaggregation during slurry tunnelling

Slurry tunnelling uses a water based slurry to aid in tunnel face support and transportation of the excavated material. Unlike other tunnelling methods this requires expensive surface separation plant to remove the excavated ground from the slurry. Incorrect specification of this plant can lead to significant delays and added cost to a tunnel drive. Due to the tight budgets and space constraints this can cause contracts to become unprofitable, in particular where small diameter slurry tunnels are excavated by pipe jacking. For this reason accurate prediction of the size distribution of the soil particles and lumps in the disaggregating slurry is required. This research concerns the development of test procedures and methods of soil classification that will enable improved predictions of the degree to which soils/weak rocks will disaggregate during the slurry tunnelling process

Design and development of a large shear box for testing working platform material

On large construction projects where deep foundations are to be installed, a working platform is placed across the entire site. This is comprised of a layer of aggregate (often crushed construction waste) usually with a particle size ranging from 120 mm downwards. Deep foundations are installed using heavy and tall drilling rigs and the working platform is thus safety critical to reduce the risk of machinery sinking and/or toppling which would lead to accidents and often serious injury to workers. Currently available design guidance is felt to result in conservative designs and there are many benefits to be gained from a greater understanding of the behaviour of working platform material. The design of these platforms is primarily governed by the angle of friction of the platform material. The measurement of friction angle for geomaterials that have large particle sizes is problematic (due to reasons of scale) and is often addressed by scaling down the material's grading curve prior to testing in small to medium size direct shear apparatus. The work presented here details the design of and the rationale for a large scale direct shear apparatus suitable for testing geomaterials with particle size distributions of the type that would be utilised in working platforms

Characterization of Coal Particles in the Soil of a Former Rail Yard and Urban Brownfield: Liberty State Park, Jersey City (NJ), USA

From the 1850\u27s until the 1960\u27s, the Central Railroad of New Jersey was among several major railways shipping anthracite and bituminous coal to the New York City area, transferring coal from railcar to barge at its extensive rail yard and port facility in Jersey City. The 490 ha Liberty State Park was developed on the site after the rail yard closed, but a ca. 100 ha brownfield zone within the park remains off limits to visitors pending future remediation. As part of an environmental forensic and industrial archeological investigation of this zone, the present study characterizes anthracite and bituminous coal particles present in abundance in the soil by scanning electron microscopy (SEM) and pyrolysis-gas chromatography-mass spectrometry (Py-GC-MS). A simple pretreatment procedure employing density separation improved the analytical results. This detailed information about the nature of contaminants at the site will help to inform the remediation effort in the public interest

Mapping urban infrastructure interdependencies and fuzzy risks

This is the final version of the article. Available from Elsevier via the DOI in this record.In this study, we considered the relationships between different types of CI and services to simulate possible cascading effects during extreme hazard conditions brought on by climate change and how to analyse impacts with limited data resources. An area in central Bristol, UK, was used as the case study to investigate the interdependencies among select assets and services. A wide range of plausible scenarios caused by pipe bursts in the area were simulated using the CADDIES 2D modelling framework, to identify the hotspots with high risk. The impact on CI, including water supply, electricity, wastewater, solid waste, transportation, telecommunication, and emergency services were assessed by the HAZUR tool. The analysis demonstrated that with limited data resources the dynamics of the interdependencies between CI networks can be highlighted and a basis of risk quantification can be established. The same procedure can be repeated to evaluate the impact of other types of hazards, or the compound hazard scenarios to provide a holistic assessment. Therefore, urban planners and managers can further explore options of interventions for setting up strategies to strengthen city resilience.This study is supported by the RESCCUE (RESilience to cope with Climate Change in Urban arEas) project, funded by the European Union Horizon 2020 research and innovation programme (Grant Agreement No. 700174)

Sheet pile groups as an alternative foundation solution to cast in-situ concrete piles

Concrete piles have become a common high load bearing foundation solutions providing end bearing and frictional resistance along the shaft. They are typically used for founding commercial or residential blocks with a design life of approximately 50 years. Following this the superstructure is decommissioned and may be demolished. However, piles are difficult to remove and therefore future developers can incur significant expense and programme delays in preparing the site to avoid obstructions. If removed, concrete piles are required to be broken down which is a slow and laborious process. However, a foundation solution has been developed that allows foundations to be installed and extracted with relative ease whilst still achieving a similar, if not improved capacity. This solution has been defined as a hybrid foundation comprising deep sheet piles for shaft resistance and a pile cap as a shallow foundation. The hybrid pile offers significant advantages over concrete piles include ease of installation, extraction, reuse and economy. Axial capacity of individual sheet piles is low, however geometrically arranging sheet piles; was shown to offer comparable or improved capacity over conventional concrete piles. The results from a series of centrifuge tests are presented in this paper

Lack of aggression and apparent altruism towards intruders in a primitive termite

This is the author accepted manuscript. The final version is available from Royal Society via the DOI in this record.In eusocial insects, the ability to discriminate nestmates from non-nestmates is widespread and ensures that altruistic actions are directed towards kin and agonistic actions are directed towards non-relatives. Most tests of nestmate recognition have focused on hymenopterans, and suggest that cooperation typically evolves in tandem with strong antagonism towards non-nestmates. Here we present evidence from a phylogenetically and behaviourally basal termite species that workers discriminate members of foreign colonies. However, contrary to our expectations, foreign intruders were the recipients of more rather than less cooperative behaviour, and were not subjected to elevated aggression. We suggest that relations between groups may be much more peaceable in basal termites compared to eusocial hymenoptera, owing to energetic and temporal constraints on colony growth, and the reduced incentive that totipotent workers (who may inherit breeding status) have to contribute to self-sacrificial intergroup conflict.The research was supported by a Royal Society University Research Fellowship (to MAC)