Back analysis for tunnelling induced ground movements and stress redistribution

Analysing tunnelling process in 2D plane strain conditions is widely used method to calculate tunnelling induced settlement profiles as well as soil structure interactions. Possibility of damage to the surface and/or underground structures can be estimated using powerful finite difference method (FDM) and finite element method (FEM) of analysis. However, setting up a realistic model that would be able to achieve this goal is rather difficult. In this paper, 2D FDM analysis has been conducted to assess tunnelling induced settlement, stress redistribution phenomena along with movements around shallow soft ground tunnels excavated in accordance with the New Austrian Tunnelling Method. Measurements recorded during construction of the Heathrow Express Trial Tunnel in London Clay were compared with the predicted values to validate numerical estimations. As a soil model, the Mohr–Coulomb plasticity model has been used in the FDM analysis. Results obtained from 2D FEM are also included in this paper for comparison purposes to evaluate performance of both numerical analysis procedures. Predictions from both FDM and FEM analyses proved to be procedures used within this work can be a tool in practical engineering applications to simulate tunnelling operations.     

Refractories: Controlled microstructure composites for extreme environments

Techniques for the examination of refractories microstructures are described with particular emphasis on the need to use a range of techniques from TEM, FEGSEM, SEM to optical microscopy and macroscale to cover all magnification scales. The grain and bond and composite nature of most powder processed refractories is emphasised and illustrated with examples of microstructural evolution on firing and in service and corrosion when in contact with silicate slags. In particular the use of cathodoluminescence in conjunction with reflected light microscopy for rapid and broad scale phase recognition is highlighted.     

Effects of different tunnel face advance excavation on the settlement by FEM

The excavation process for a tunnel changes in terms of its service requirements, ground conditions and the stability of surface buildings in urban areas. When a tunnel is excavated, there will be settlement, which may cause damage to surface structures. To control and limit the settlement caused by tunnelling operations, there have been many tunnelling techniques proposed. Thus, in this paper, a number of Finite Element Method analyses were conducted to investigate the effects of different patterns for advancing the tunnel face on the settlement. The Heathrow Express Trial tunnel was constructed in accordance with the principles of the New Austrian Tunnelling Method (NATM). The settlement measurements taken during its construction were used to validate the results from the analyses undertaken. Three different face advance techniques were used during the construction of the Heathrow Express Trial tunnel viz. Twin sidewall excavation (TS1), single sidewall excavation (TS2), and Crown, Bench and Invert excavation (TS3). As the trial work proved that TS2 produced the minimum settlement above tunnel centreline, only TS2 was subjected to the FEM analysis in this research. In order to simulate TS2 correctly three types of excavation models were devised and the results compared to field measurements of TS2. For the FEM analysis the Hypothetical Modulus of Elasticity (HME) soft lining approach was used and a practical method to estimate HME is proposed for when it is used for different face advance sequences. Results proved that when the excavation pattern was changed, the HME value was also changed and settlement over the tunnel centreline changed in terms of the face advance pattern adopted.     

Numerical simulations of the failure process of anaclinal slope physical model and control mechanism of negative Poisson’s ratio cable

Bulletin of Engineering Geology and the Environment - Occurrence of toppling failure has been prominent due to the increasing of infrastructure construction, such as road slopes, dams, and...     

Raw material homogenization production plan in multiple quarries—slope stability assessment: Cement raw material clay pit sample

Up-to-date solution algorithms, which are used to determine optimum production sequences and ultimate pit limits are discussed. These private solutions for quarries might be inadequate for different mining areas. Optimization solutions that are offered for quarries in raw material preparation process within constraints, which are determined by mixing raw material that were produced from different quarries such as cement production, fall short, instead these are replaced by trial and error methods that are made for main constraints. In this study, production sequence homogenization study for limestone that belongs to a cement factory and clinker production from two clay pits were presented, slope stability assessment was also made. As a result of these studies, a planning process based on production amounts, distances, chemical content of clinker and slope safety constraints was developed.     

Renovating the excitation circuit of a conventional welding converter

This paper presents two different new excitation current supplies based on power electronics for an existing conventional welding converter. The proposed circuits are simulated using Lab-VIEW 1200 AI and a PC based system. In the expressions for winding currents the dynamic inductances are used to take into account the saturation in the core of the winding. The experimental circuits are implemented and tested. The percentage peak-to-peak ripple currents are calculated for both simulation and experimental results and for both circuit configurations. The results are summarized in two tables for comparison.     

Synthesis,characterization and in vitro antibacterial assessments of a novel modified poly[maleic anhydride-alt-acrylic acid]/acriflavine conjugate

Water-soluble maleic anhydride-containing poly[maleic anhydride-alt-acrylic acid] (poly(MA-alt-AA) or MAAA) copolymer was synthesized by free-radical chain polymerization reaction, in 1,4-dioxane in the presence of benzoyl peroxide, 0.1 %, as the radical initiator at 70 °C under a nitrogen atmosphere. The purified copolymer was then modified with an anti-external fungal and anti-cancer active agent, acriflavine (AF). The modification reaction was performed 48 h at 70 °C in dimethylformamide organic media, using triethylamine (TEA or Et₃N) as the catalyst. The modified or conjugated copolymer/drug couple was named as MAAA/AF. Detailed structural characterization of the copolymer (MAAA) and modified product (MAAA/AF) was carried out by Fourier Transform Infrared (FTIR) and Nuclear Magnetic Resonance (¹H-NMR and ¹³C-NMR). The obtained FTIR, ¹H-NMR, and ¹³C-NMR spectra confirmed that AF was successfully bound to the MAAA copolymer backbone by ring-opening reaction. Antimicrobial susceptibility of the MAAA, AF, and MAAA/AF was evaluated by Kirby Bauer Disc Diffusion method on Mueller–Hinton Agar using Enterecoccus faecium, Enterohaemorrhagic Escherichia coli (EHEC), Staphylococcus aureus and Listeria monocytogenes. Results obtained indicated that MAAA/AF had antibacterial activity on EHEC and S. aureus at 50, 40, and 30 µg. A mechanism for MAAA and AF was then also suggested for the conjugation reaction.