Effect of temperature induced excess porewater pressures on the shaft bearing capacity of geothermal piles

Changes in temperature in clays of low permeability typically induce excess porewater pressures. In the context of geothermal piles this effect has typically been overlooked since most installations have occurred in soils with higher values of permeability. A parametric study is presented that solves the governing differential equations one dimensionally in a pile to study the influence of the various parameters: temperature of the fluid, permeability and soil compressibility. A new shaft resistance reduction ratio has been also defined to illustrate the loss of bearing capacity. The study shows that when the value of permeability is 1E-11 m/s or lower, combined with a soil compressibility in excess of 20,000 MPa, the developed excess porewater pressures can potentially reduce the effective stress locally to very low values. The solution applied to the case of the Lambeth College, London, also provides a plausible explanation to the observed loss of shaft friction of the tested pile

Lessons learnt from a deep excavation for future application of the observational method

This paper draws lessons learnt from a comprehensive case study in overconsolidated clay. Apart from the introduction of the case study, including field measurements, the paper draws on the observations and a three-dimensional (3D) numerical analysis to discuss the implications of observations in the application of the observational method (OM) in the context of the requirements of EUROCODE 7 (EC7). In particular, we focus on corner effects and time-dependent movements and provide initial guidance on how these could be considered. Additionally, we present the validation of a new set of parameters to check that it provides a satisfactory compliance with EC7 as a set of design parameters. All these findings and recommendations are particularly important for those who want to use the OM in similar future projects

Creating high fidelity 360° virtual reality with high dynamic range spherical panorama images

This research explores the development of a novel method and apparatus for creating spherical panoramas enhanced with high dynamic range (HDR) for high fidelity Virtual Reality 360 degree (VR360) user experiences. A VR360 interactive panorama presentation using spherical panoramas can provide virtual interactivity and wider viewing coverage; with three degrees of freedom, users can look around in multiple directions within the VR360 experiences, gaining the sense of being in control of their own engagement. This degree of freedom is facilitated by the use of mobile displays or head-mount-devices. However, in terms of image reproduction, the exposure range can be a major difficulty in reproducing a high contrast real-world scene. Imaging variables caused by difficulties and obstacles can occur during the production process of spherical panorama facilitated with HDR. This may result in inaccurate image reproduction for location-based subjects, which will in turn result in a poor VR360 user experience. In this article we describe a HDR spherical panorama reproduction approach (workflow and best practice) which can shorten the production processes, and reduce imaging variables, and technical obstacles and issues to a minimum. This leads to improved photographic image reproduction with fewer visual abnormalities for VR360 experiences, which can be adaptable into a wide range of interactive design applications. We describe the process in detail and also report on a user study that shows the proposed approach creates images which viewers prefer, on the whole, to those created using more complicated HDR methods, or to those created without the use of HDR at all