A Second Order Finite Volume Technique for Simulating Transport in Anisotropic Media

An existing two-dimensional finite volume technique is modified by introducing a correction term to increase the accuracy of the method to second order. It is well known that the accuracy of the finite volume method strongly depends on the order of the approximation of the flux term at the control volume (CV) faces. For highly orthotropic and anisotropic media, first order approximations produce inaccurate simulation results, which motivates the need for better estimates of the flux expression. In this article, a new approach to approximate the flux term at the CV face is presented. The discretisation involves a decomposition of the flux and an improved least squares approximation technique to calculate the derivatives of the dependent function on the CV faces for estimating both the cross diffusion term and a correction for the primary flux term. The advantage of this method is that any arbitrary unstructured mesh can be used to implement the technique without considering the shapes of the mesh elements. It was found that the numerical results well matched the available exact solution for a representative transport equation in highly orthotropic media and the benchmark solutions obtained on a fine mesh for anisotropic media. Previously proposed CV techniques are compared with the new method to highlight its accuracy for different unstructured meshes

Effect of soil parameter uncertainty on seismic response of buried segmented pipeline

Pipelines are important lifeline facilities spread over a large area and they generally encounter a range of seismic hazards and different soil conditions. The seismic response of a buried segmented pipe depends on various parameters such as the type of buried pipe material and joints, end restraint conditions, soil characteristics, burial depths, and earthquake ground motion, etc. This study highlights the effect of the variation of geotechnical properties of the surrounding soil on seismic response of a buried pipeline. The variations of the properties of the surrounding soil along the pipe are described by sampling them from predefined probability distribution. The soil-pipe interaction model is developed in OpenSEES. Nonlinear earthquake time-history analysis is performed to study the effect of soil parameters variability on the response of pipeline. Based on the results, it is found that uncertainty in soil parameters may result in significant response variability of the pipeline

The reliability of rock mass classification systems as underground excavation support design tools

This thesis examines the reliability of rock mass classification systems available for underground excavation support design. These methods are sometimes preferred to rational methods of support design particularly if detailed information required for the latter mentioned methods is lacking. The classification approach requires no analysis of any specific failure mechanisms or the forces required to stabilise unstable rocks, yet, the support measures thus designed are considered to deal with all possible failure mechanisms in a rock mass.Amongst the several rock mass classification methods developed for application in underground excavation engineering, two have stood out. These are known as rock mass rating (RMR) and tunnelling quality index (Q), introduced by Bieniawski (1973) and Barton et al. (1974), respectively. Over the years, the two methods have been revised and updated so as to improve their reliability as support design tools, yet the two methods are know to have limitations and their reliability has long been a subject of considerable debate. Nevertheless, attempts to assess their reliability in a systematic manner have been limited. Further, some practitioners in the field of rock engineering continue to use these methods as the sole methods of support design for underground rock excavations. The objective of thesis, therefore, is to contribute to a better understanding of the reliability of the two classification methods.This study considered that the reliability of the RMR and Q methods can be assessed by comparing their support predictions with those derived by other applicable methods and also with the actual support installed. Such an assessment can best be carried out during excavation of an underground opening because representative data can be collected by direct observation of the as-excavated ground conditions and monitoring the performance of the support installed. In this context, the geotechnical data obtained during the construction of several case tunnels were reviewed and the two classification methods were applied. The effectiveness of their support predictions was then evaluated against the potential failures that can be predicted by some of the applicable rational methods. Since the rock masses intersected in the case tunnels are jointed, mostly the structurally controlled failure modes were analysed. The support measures predicted by the two methods were compared with each other and with the actual support installed in the case tunnels. Further, the RMR and Q vales assigned to the case tunnels were correlated to observe any relationship between the two.The study showed that the RMR and Q predicted support measures are not always compatible. In some circumstances, the two methods can either overestimate or under estimate support requirements

Globalization and the Nation State

15 pages

Probabilistic and Scenario Based Projections of Mean And Extreme Sea Levels Under Climate Change

Source: ICHE Conference Archive - https://mdi-de.baw.de/icheArchiv

The United Nations and Civil Society

7 pages

Response Fibre Bragg Grating (FBG) strain sensors embedded at different locations through the thickness around a delamination in a composite lamina

A few FBG strain sensors were embedded at a vicinity of delamination of a laminated composite plate. Reflected spectra of FBG sensors which located in the same layer as the delamination and one layer above the delamination were investigated in order to understand the change of the reflected spectra due to stress concentrations at the delamination. The reflected waveforms of sensors were broadened with the increase of loading, as expected. A considerable difference in the response of two sensors was observed during both uniaxial and flexural loading. These differences show that the FBG sensors are capable of capturing the precise nature of the delamination under various loading conditions. Further, these observations provide evidence of the feasibility of using FBG sensor responses obtained from various locations allows the location of the delamination to be determined. This paper details some new and interesting findings of the use of spectral shapes and strain measurements from embedded FBG sensors in damage detection

The United Nations and Civil Society

7 pages