The role of umbrella arch and face bolt as deformation preventing support system in preventing building damages

Ground settlement is the most significant environmental impact of the tunnels excavated in intensively urbanized regions. A Considerable amount of ground settlement occurs by pre-convergence, formed during the time of support setting followed by the excavation, and movement of tunnel face into the tunnel. The risk of damage on the buildings by the ground settlement can be catastrophically high. Therefore, rock engineers bear an important duty to prevent the potential damage on buildings by controlling the ground settlement while excavating the tunnels. This has been accomplished by applying umbrella arch with face bolt technique recently in various important areas. In this method, the ground settlements can substantially be decreased by limiting the tunnel face movement into the tunnel, by creating a pseudo shell around the tunnel face with umbrella arch and then increasing the stability with face bolts. In this study, as part of the 2nd phase of Izmir metro construction in densely populated Poligon district of Izmir the effects of umbrella arch-face bolt applications on ground settlements have been determined using numerical modeling and in situ measurements. Results indicated that the umbrella arch and face bolt applications have significantly diminished the risk of settlement damage on buildings by reducing the ground settlements and convergence as 69% and 57%, respectively.     

Numerical simulations examining the relationship between wall-roughness and fluid flow in rock fractures

Understanding how fracture wall-roughness affects fluid flow is important when modeling many subsurface transport problems. Computed tomography scanning provides a unique view of rock fractures, allowing the measurement of fracture wall-roughness, without destroying the initial rock sample. For this computational fluid dynamics study, we used several different methods to obtain three-dimensional meshes of a computed tomography scanned fracture in Berea sandstone. These volumetric meshes had different wall-roughnesses, which we characterized using the Joint Roughness Coefficient and the fractal dimension of the fracture profiles. We then related these macroscopic roughness parameters to the effective flow through the fractures, as determined from Navier–Stokes numerical models. Thus, we used our fracture meshes to develop relationships between the observed roughness properties of the fracture geometries and flow parameters that are of importance for modeling flow through fractures in field scale models. Fractures with high Joint Roughness Coefficients and fractal dimensions were shown to exhibit tortuous flow paths, be poorly characterized by the mean geometric aperture, and have a fracture transmissivity 35 times smaller than the smoother modeled fracture flows.     

Flexible magnetoinductive ring MRI detector: Design for invariant nearest-neighbour coupling

A flexible birdcage-type resonant RF detector for magnetic resonance imaging is described. The circuit consists of a polygonal ring of magnetically coupled L–C resonators, a periodic structure supporting backward magnetoinductive waves. The elements are mechanically linked to allow relative rotation, and the pivot point is optimised to hold the nearest-neighbour coupling coefficient invariant to small changes in the angle of an undistorted joint. Simple theory based on a parallel wire approximation to rectangular inductors is developed to allow the variation of the coupling coefficient with angle and radius to be estimated, and hence determine the location of the pivot. The optimised pivot is shown to reduce resonance splitting in octagonal rings. However, second-neighbour interactions degrade performance. The theory is verified experimentally using printed circuit board elements coupled by flexible hinges, and the invariance of the nearest-neighbour coupling coefficient is confirmed. Octagonal ring resonators are constructed for operation at 63.8 MHz frequency and the mode spectra of regular and distorted rings are measured. Magnetic resonance imaging properties are investigated using ¹H MRI of simple objects in a 1.5 T field. Images are obtained from undistorted and distorted resonators and the effect of distortion on SNR is quantified.     

Physical and mechanical properties of Gokceada: Imbros (NE Aegean Sea) Island andesites

The physical and mechanical properties of the andesite forming much of the island of Gökçeada (Imbros), Turkey, were investigated using 54 mm samples cores from 12 blocks obtained from a quarry. The results were evaluated using regression analysis and good empirical relationships were obtained.     

The importance of the relationship between scale and process in understanding long-term DOC dynamics

Concentrations of dissolved organic carbon have increased in many, but not all, surface waters across acid impacted areas of Europe and North America over the last two decades. Over the last eight years several hypotheses have been put forward to explain these increases, but none are yet accepted universally. Research in this area appears to have reached a stalemate between those favouring declining atmospheric deposition, climate change or land management as the key driver of long-term DOC trends. While it is clear that many of these factors influence DOC dynamics in soil and stream waters, their effect varies over different temporal and spatial scales. We argue that regional differences in acid deposition loading may account for the apparent discrepancies between studies. DOC has shown strong monotonic increases in areas which have experienced strong downward trends in pollutant sulphur and/or seasalt deposition. Elsewhere climatic factors, that strongly influence seasonality, have also dominated inter-annual variability, and here long-term monotonic DOC trends are often difficult to detect. Furthermore, in areas receiving similar acid loadings, different catchment characteristics could have affected the site specific sensitivity to changes in acidity and therefore the magnitude of DOC release in response to changes in sulphur deposition. We suggest that confusion over these temporal and spatial scales of investigation has contributed unnecessarily to the disagreement over the main regional driver(s) of DOC trends, and that the data behind the majority of these studies is more compatible than is often conveyed.     

Thermal sensation of Hong Kong people with increased air speed,temperature and humidity in air-conditioned environment

In the warm and humid climate zone, air-conditioning (AC) is usually provided at working places to enhance human thermal comfort and work productivity. From the building sustainability point of view, to achieve acceptable thermal sensation with the minimum use of energy can be desirable. A new AC design tactic is then to increase the air movement so that the summer temperature setting can be raised. A laboratory-based thermal comfort survey was conducted in Hong Kong with around 300 educated Chinese subjects. Their thermal sensation votes were gathered for a range of controlled thermal environment. The result analysis shows that, like in many other Asian cities, the thermal sensation of the Hong Kong people is sensitive to air temperature and speed, but not much to humidity. With bodily air speed at 0.1–0.2 m/s, clothing level 0.55 clo and metabolic rate 1 met, the neutral temperature was found around 25.4 °C for sedentary working environment. Then recommendations are given to the appropriate controlled AC environment in Hong Kong with higher airflow speeds.     

Correction to: Comparative analysis of limit equilibrium and numerical methods for prediction of a landslide

Bulletin of Engineering Geology and the Environment - Landslides that occur due to the rapid motion of a rock-mass are a primary risk in mountainous terrains and are a danger to human life and...     

Water Purification of Dyes and Hardness Salts by Ceramic Membranes Modified with Silica and Pyrocarbon

Modification of ceramic membranes was conducted with silica, obtained from liquid glass, and pyrocarbon from carbonized polyisocyanate and sucrose at 800°C. Water from Ca²⁺ and direct scarlet dye was purified by a pressure-driven method at 0.7 and 1.1–1.2 MPa. The retention coefficient of Ca²⁺ and specific productivity of the modified membranes depending on filtration time decreased respectively from 63 to 8% and from 150 to 4.7 dm3/(m².h). For direct scarlet dye, the retention factor constitutes 99.0 and 99.9% at the specific productivity respectively 27 and 1.8 dm3(m².h).     

Hypoplastic model for crushable sand

A constitutive model for granular materials which considers grain crushing effects is developed in the framework of hypoplasticity. As grain crushing occurs the behaviour of granular material can usually be significantly affected. Several empirical relations between peak strength, uniformity coefficient and stiffness of sand depending on stress level or amount of grain crushing have been derived in the past. In this paper, such relations are employed to improve a basic hypoplastic constitutive model based on the changes of stress level or grain size distribution. In the proposed modified hypoplastic model only two additional physical parameters, namely uniformity coefficient and mean grain size are incorporated. The validation of the modified model for three different sands under triaxial test response with cell pressures up to 30?MPa is presented and shows a significantly better correspondence with regard to the original basic hypoplastic model.     

Finite element parametric study of the performance of a deep excavation

Deep excavations are widely used for the development of underground space. The structural performance of any deep excavation is influenced by details of the soil behaviour, the form of the retaining and support structures that are employed and also the sequence of construction. Finite element analysis is potentially an effective tool for considering both the geotechnical and structural aspects of the design of deep excavations. To capture the main features of the excavation behaviour, a finite element model is required that is able to represent the principal deformation and structural mechanisms at an appropriate level of detail. The current paper explores the various modelling assumptions that need to be considered when developing detailed 3D finite element models for the design of deep excavations. A parametric study is described, based on an idealised square excavation, to investigate the influence that certain key features of the model can have on the quality of the computed results. The study includes the choice of element type to model the structural components, the selection of appropriate material parameters, the choice of procedures to model post-cure shrinkage of the concrete elements and the choice of procedure to model the soil/structure interfaces. The results of this parametric study provide guidance for the development of finite element models for practical design purposes.