Ureolytic activities of a urease-producing bacterium and purified urease enzyme in the anoxic condition: Implication for subseafloor sand production control by microbially induced carbonate precipitation (MICP)

Microbially induced carbonate precipitation (MICP) involves the hydrolysis of urea by indigenous or introduced urease-producing bacteria, which induces carbonate precipitation. By allowing this process to occur in the pores of unconsolidated sand, sand particles bond together, creating a sandstone like material. Although MICP has been explored recently for possible applications in civil and construction engineering, this study examines its application to sand production control during hydrate gas exploitation from subseafloor sediments. The major uncertainty is the ureolytic activities of bacteria and associated enzyme under the subseafloor condition. The main aim of this study was to quantify the ureolytic efficiency of a urease-producing bacterium and purified urease enzyme in the oxic and anoxic conditions. The purified urease enzyme and B. megaterium were subject to bench shaking ureolyic activity tests in both conditions. Biochemical parameters including urea concentration, electric conductivity (EC), pH, and optical density at 600 nm (OD_600) of the solution at different time intervals were measured. As a quality control procedure, dissolved oxygen concentration (DO) of the final solutions was also measured. Results show that the effect of oxygen availability on ureolytic efficiency of purified urease enzyme is marginal. However, anoxic ureolytic performance of B. megaterium is better than its oxic counterpart. It is also found that higher concentration of urease and multi-amendment of bacteria help raise ureolytic efficiency. In order to sustain ureolytic efficiency and facilitate its up-scaled field application, several practice measures can be implemented including growing bacteria aerobically to exponential stage before implemented into the subseafloor sites, injecting larger bacteria cell number, and repeatedly supplying fresh bacteria cells.This study was a part of the program of the Research Consortium for Methane Hydrate Resources in Japan (MH21 Research Consortium) and was supported by a grant from the Japan Oil, Gas and Metals National Corporation (JOGMEC). Special thanks are extended to Institute for Geo-Resource and Environment, National Institute of Advanced Industrial Science and Technology (AIST), Japan for providing all experimental facilities. The first author also extends thanks to China Scholarship Council (CSC) and Cambridge Commonwealth, European and International Trust for their financial support in the PhD studentship.This is the author accepted manuscript. The final version is available from Elsevier via http://dx.doi.org/10.1016/j.ecoleng.2016.01.073

Performance monitoring of a secant piled wall using distributed fiber optic strain sensing

An optical fiber strain sensing technique, based on Brillouin Optical Time Domain Reflectometry (BOTDR), was used to monitor the performance of a secant pile wall subjected to multiple props during construction of an adjacent basement in London. Details of the installation of sensors as well as data processing are described. Distributed strain profiles were obtained by deriving strain measurements from optical fibers installed on opposite sides of the pile to allow monitoring of both axial and lateral movements along the pile. Methods for analyzing the thermal strain and temperature compensation are also presented. Measurements obtained from the BOTDR were found to be in good agreement with inclinometer data from the adjacent piles. The relative merits of the two different techniques are discussed

Re-thinking uk transport emissions – Getting to the 2050 targets

Transport is a complex system, integral to national and international structure and without which society cannot function. At the same time, transport is a significant contributor to global greenhouse gas emissions. In the UK a step change is required in the transport sector to achieve the legally binding reduction targets of the Climate Change Act 2008. Following the UK government’s 2013 review of carbon dioxide emissions from infrastructure, this paper looks at the country’s present and projected transport emissions in the context of the transport status quo and plans for growth. It argues there is an urgent need to rebalance the transport modal mix, with all modes integrated into a seamless transport system with smart interfacing between them. Drivers for behavioural change are also essential.Engineering and Physical Sciences Research CouncilThis is the final version of the article. It first appeared from ICE Publishing via https://doi.org/10.1680/jcien.15.0007

Harmonic moments and an inverse problem for the heat equation

In the paper, we study an inverse problem for the heat equation. We introduce a class of bilinear forms on the space of harmonic polynomials ( called harmonic moments), which are represented by the Dirichlet-to-Neumann map. We investigate the uniqueness, stability, and reconstruction of the inverse problem. The inverse data are given in the terms of the bilinear forms and can be exchanged into the data of the Dirichlet-to-Neumann map. The reconstruction ( of the density) is accomplished in two different ways: one is due to the idea of the mollifier and the other to the representation by the Carleman kernel in the complex analysis. The error terms are estimated depending on the degree of the harmonic polynomials. We estimates norms of the data on an arbitrary time interval by the norms on some fixed interval (e.g., 0 < t < 2)

Greenhouse gas considerations in rail infrastructure in the UK

Transportation-related greenhouse gas (GHG) emissions account for an increasing proportion of total emissions in the UK and globally. The provision of rail transit is popularly proposed to reduce transport GHG emissions, but the provision of new infrastructure is itself GHG intensive. Understanding of the GHG emissions impact of rail projects is limited and very few longitudinal studies have been carried out. Existing assessments are often limited both in their scope and the factors considered. A holistic understanding of GHG impacts must include an assessment of capital GHG emissions, operational energy and maintenance as well as an assessment of ridership mode shift and mode share impacts and the relationship between transit infrastructure and land use. This paper explores rail infrastructure projects and their associated GHG emissions. Guidance is given on the aspects of rail planning, design and construction that must be considered to more fully understand the associated GHG impacts.The authors would like to thank The Commonwealth Scholarship Commission in the UK for the scholarship funding that facilitated this work

Distributed fibre optic sensors for measuring strain and temperature of cast-in-situ concrete test piles

In this paper we present the use of distributed fibre optic sensor (DFOS) technology to measure the temperature and strain of reinforced concrete test piles during construction and during static load tests. Eight test piles were recently instrumented with DFOS, on three construction sites in London, by the Cambridge Centre for Smart Infrastructure and Construction (CSIC), in collaboration with Ove Arup & Partners Ltd. The concrete curing temperature profiles of the piles were used to detect the presence of significant defects in the piles. The load test strain profiles along the length of the piles were used to determine the load capacity of the piles and estimate the design parameters of the various soil strata, as well as the internal relative displacement of the piles under various loads. Being distributed in nature, DFOS give a much more detailed picture of the performance of a test pile, as compared to traditional embedded point sensors, such as vibrating wire strain gauges and extensometers. This is demonstrated with a sample of data obtained from one of the instrumented test piles.This is the author accepted manuscript. It is currently under an indefinite embargo pending publication by ICE Publishing

An implicit high-order material point method.

The material point method (MPM) is a version of the particle-in-cell (PIC) which has substantial advantages over pure Lagrangian or Eulerian methods in numerical simulations of problems involving large deformations. The MPM helps to avoid mesh distortion and tangling problems related to Lagrangian methods and as well as the advection errors associated with Eulerian methods. Despite the MPM being promoted for its ability to solve large deformation problems the method suffers from instabilities when material points cross between elements. These instabilities are due to the lack of smoothness of the grid basis functions used for mapping information between the material points and the background grid. In this paper a novel high-order MPM is developed to eliminate the cell-crossing instability and improve the accuracy of the MPM method

Gradient elasto-plasticity with the generalised interpolation material point method.

The modelling of geomechanics problems can require a method that allows large deformations and non-linear material behaviour, in this respect the Generalised Material Point Method (GIMPM) is ideal. A fully implicit version of GIMPM has recently been developed for geomechanics problems and some aspects of its implementation are described here. An area that has received less attention in material point methods is that conventional analysis techniques constructed in terms of stress and strain are unable to resolve structural instabilities such as shear banding. This is because they do not contain any measure of the length of the microstructure of the material analysed, such as molecule size or grain structure. Gradient theories provide extensions of the classical equations with additional higher-order terms. The use of length scales makes it possible to model a finite thickness shear band which is not possible with traditional methods. Much work has been done on using gradient theories to include the effect of microstructure in the finite element method (and other numerical analysis techniques) however this yet to be combined with material point methods. In this paper the key equations that are required to extend the implicit GIMPM method to include gradient elasto-plasticity are detailed