Soil conditioning under London

The CTRL Contract 220 covered 7.5km twin-bore tunnels excavated between late 2002 and early 2004 from Stratford Box to St Pancras station in Central London. To ensure efficient machine operation as well as the transport and disposal of soil, soil conditioning treatments were applied. Specifically, the foam injection ratio (FIR) and the polymer injection ratio (PIR) (injected volume of foam and polymer solution expressed as a percentage of the excavated soil volume) were employed. It was found that carefully selected soil conditioning allowed chamber pressures of 200kPa or more to be accurately controlled in the stiff London Clay and to an extent, in the very stiff clays of the Lambeth Group. Average FIRs of 50% and PIRs of 7 and 9% were used in the Thanet Sand and in the Lambeth Group Clays. In contrast, much lower quantities of foam were used in the London Clay.

Value roadmapping: A structured approach for early stage technology investment decisions

Deciding to invest in early stage technologies is one of the most important tasks of technology management and arguably also the most uncertain. It assumes a particular significance in the rise of technology companies in emerging economies, which have to make appropriate investment decisions. Technology managers already have a wide range of methods and tools at their disposal, but these are mostly focussed on quantitative measures such as discounted cash flow and real options techniques. However, in the early stages of technology development there seems to be a lot of dissatisfaction with these techniques as there appears to be a lack of accuracy with respect to the underlying assumptions that these models require. In order to complement these models this paper will discuss an alternative approach that we call value road-mapping. By adapting roadmapping techniques the potential value streams of early stages technologies can be plotted and hence a clearer consensus based picture of the future potential of new technologies emerges. Roadmapping is a workshop-based process bringing together multifunctional perspectives, and supporting communication in particular between technical and commercial groups. The study is work in progress and is based on a growing number of cases. (c) 2006 PICMET.

An ecodesign model based on industry experience

With the increase in environmental legislation facing many industrial sectors organisations are now looking for ways to improve their environmental performance. To a large extent organisations have tended to concentrate on their operations inside the "factory gates" with little regard to the environmental performance of the products they produce. However, this is now changing and some organisations are beginning to take a close look at their products and their effects on the environment during its use phase as well as during the manufacture and disposal phases. At Cranfield University we have carried out a 3 year survey of US, Central European and UK companies claiming to practice ecodesign has been undertaken. Thirty electrical and electronic manufacturers were studied, some through in-depth observation of design programmes, most through semi-structured interviews. The survey and action research sought to understand the way in which these companies practised ecodesign and how they .had implemented ecodesign. A common pattern emerged from the data which suggests that companies successfully implementing ecodesign have many similar experiences. The resulting ecodesign model is presented and discussed, and the factors critical to successful implementation at various stages are explored. The factors cover a range of topics including design management, motivation, design tools, design phases, communication and the designers perspective.

Characterisation and fluidisation of synthetic pit latrine sludge

Half of the world’s urban population will live in informal settlements or “slums” by 2030. Affordable urban sanitation presents a unique set of challenges as the lack of space and resources to construct new latrines makes the de-sludging of existing pits necessary and is something that is currently done manually with significant associated health risks. Therefore various mechanised technologies have been developed to facilitate pit emptying, with the majority using a vacuum system to remove material from the top of the pit. However, this results in the gradual accumulation of unpumpable sludge in the pit, which eventually fills the latrine and forces it to be abandoned. This study has developed a method for fluidising unpumpable pit latrine sludge, based on laboratory experiments using a harmless synthetic sludge. Such a sludge consisting of clay and compost was developed to replicate the physical characteristics of pit latrine sludges characterised in Botswana during the 1980s. Undrained shear strength and density are identified as the critical parameters in controlling pumpability and a method of sludge characterisation based on these parameters is reported. In a series of fluidisation tests using a one fifth scale pit emptying device the reduction in sludge shear strength was found to be caused by i) dilution, which increases water content, and ii) remoulding, which involves mechanical agitation to break down the structure of the material. The tests demonstrated that even the strongest of sludges could be rendered “pumpable” by sufficient dilution. Additionally, air injection alone produced a three-fold decrease in strength of consolidated samples as a result of remoulding at constant water content. The implications for sludge treatment and disposal are discussed, and the classification of sludges according to the equipment required to remove them from the latrine is proposed. Possible field tests to estimate sludge density and shear strength are suggested. The feasibility of using low cost vacuum cleaners to replace expensive vane pumps is demonstrated. This offers great potential for the development of affordable pit emptying technologies that can remove significantly stronger sludges than current devices through fluidising the wastes at the bottom of the pit before emptying

Deformation and fracture of impulsively loaded sandwich panels

Light metal sandwich panel structures with cellular cores have attracted interest for multifunctional applications which exploit their high bend strength and impact energy absorption. This concept has been explored here using a model 6061-T6 aluminum alloy system fabricated by friction stir weld joining extruded sandwich panels with a triangular corrugated core. Micro-hardness and miniature tensile coupon testing revealed that friction stir welding reduced the strength and ductility in the welds and a narrow heat affected zone on either side of the weld by approximately 30%. Square, edge clamped sandwich panels and solid plates of equal mass per unit area were subjected to localized impulsive loading by the impact of explosively accelerated, water saturated, sand shells. The hydrodynamic load and impulse applied by the sand were gradually increased by reducing the stand-off distance between the test charge and panel surfaces. The sandwich panels suffered global bending and stretching, and localized core crushing. As the pressure applied by the sand increased, face sheet fracture by a combination of tensile stretching and shear-off occurred first at the two clamped edges of the panels that were parallel with the corrugation and weld direction. The plane of these fractures always lay within the heat affected zone of the longitudinal welds. For the most intensively loaded panels additional cracks occurred at the other clamped boundaries and in the center of the panel. To investigate the dynamic deformation and fracture processes, a particle-based method has been used to simulate the impulsive loading of the panels. This has been combined with a finite element analysis utilizing a modified Johnson-Cook constitutive relation and a Cockcroft-Latham fracture criterion that accounted for local variation in material properties. The fully coupled simulation approach enabled the relationships between the soil-explosive test charge design, panel geometry, spatially varying material properties and the panel's deformation and dynamic failure responses to be explored. This comprehensive study reveals the existence of a strong instability in the loading that results from changes in sand particle reflection during dynamic evolution of the panel's surface topology. Significant fluid-structure interaction effects are also discovered at the sample sides and corners due to changes of the sand reflection angle by the edge clamping system. © 2012 Elsevier Ltd. All rights reserved.