Fundamental response of pore-water pressure to microfabric and permeability characteristics: Eckernförde Bay

Ambient and dynamic in situ pore pressures were measured, and microfabric was examined in finegrained, shallow-water sediment in Eckernförde Bay, Germany. In situ permeabilities were calculated from piezometer data. Pore-water pressure decay times in sediments 0.5–1.0 m subbottom are indicative of clayey materials. Shallower sediments, although of similar classical grain size as the deeper sediments, have quicker decay times typical of silty marine sediment. Pore pressure response is a function of the microfabric, porometry, and sediment permeability. Aggregates (composed of fine-grained material, biota, and extracellular polymers) produce large pores and complex microstructure, resulting in effective permeabilities characteristic of silts.     

Numerical investigation of pile-head load effects on the negative skin friction development of a single pile in consolidating ground

This study conducted parametric analyses to investigate the influence of structural loading (pile-head loading) on the development of negative skin friction in friction single piles and friction-end-bearing single piles in consolidating ground. Numerical effective stress-based mechanical-flow analysis models were built in ABAQUS software. The appropriateness of the modeling approach was verified by applying it to simulate a field model test described in the literature. For small surcharges, pile-head loading considerably reduces the depth of the neutral plane and therefore drag load for the friction pile. Under the same pile-head loads, the reduction in total drag load for the friction-end-bearing pile is smaller than that for the friction pile. However, when the friction-end-bearing pile is subjected to larger pile-head loads, the degree of total drag load reduction is comparable to that of the friction pile. Considerable pile-head displacement occurs under the combined action of pile-head and surcharge loadings. In contrast to the friction pile, the friction-end-bearing pile, because of the greater stiffness and strength of its bearing stratum, exhibits a significant reduction in negative skin friction, no bearing failure, and a smaller pile-head displacement when it is subjected to large pile-head loading.

     

Microbial population structures in activated sludge before and after the application of synthetic polymer

Since Juang (2005) has found that the sludge settleability became much worse and the flocs displayed as pin flocs in only a few days after the addition of synthetic polymer was halted, it is hypothesized that the shift of microbial population in activated sludge before and after the addition of synthetic polymer might have occurred. Therefore, the identification of microbial population in the activated sludge of a lab-scaled continuous-flow type of treatment reactor was conducted at different phases of this study. The results of this study showed that the presence of synthetic polymer inhibited the growth of dominant bacteria and floc-formers in activated sludge, but gave a competitive advantage of growth to some other bacteria. The addition of synthetic polymer has caused the shift of microbial population and affected the growth of floc-formers in activated sludge. It took more than one month for the population structure of predominant microorganisms in activated sludge to return more closely to the initial population structure.     

Regional variations in the crustal structure of Northern Canada from surface wave dispersion

Rayleigh and Love wave group velocities in the Arctic islands and adjacent mainland of northern Canada exhibit large regional variations which can be attributed to variations in crustal structure. The shield and platform regions, the eastern Sverdrup basin, and the western Sverdrup basin are characterized by progressively slower velocities. Inversions of the regionalized group velocity data lead to three distinct shear-velocity models. The shield and platform model is similar to earlier models obtained for the Canadian shield. The Sverdrup basin models have low near-surface velocities which may correspond to thick accumulations of sediment. A sediment thickness of about 12 km obtained for the eastern basin corresponds to the maximum thickness inferred from earlier geological studies. An even thicker zone of low velocities occurs in the upper crust of the western basin. This zone may represent the true thickness of a very deep basin or slow velocities in basement rock may underlie the shallower sediments. A third alternative is that low apparent velocities for the western Sverdrup basin result from systematic errors in group velocity determinations produced by epicentral mislocations or origin time errors of the earthquakes used, but such mislocation or errors would have to be quite large to explain the observations. It is not possible to explain the group velocities across the basin areas by simply adding sediments to the shield and platform model. The resulting discrepancies with the data suggest an altogether different crustal structure beneath the basin than that beneath the shield and platform areas.     

A multi-criteria decision-making approach for evaluating carbon performance of suppliers in the electronics industry

Although interest in addressing environmental perspectives in supplier management is rising, incorporating the issue of carbon management into supplier selection in green supply chain is still considerably scarce. This study presents a model for evaluating carbon performance of suppliers by utilizing multiple-criteria decision-making. Through literature reviews and expert opinions, 13 criteria within carbon performance are identified for evaluating suppliers. Subsequently, the analytic network process is utilized to determine the relative weights of each criterion. Finally, the VlseKriterijumska Optimizacija I Kompromisno Resenje technique is employed to evaluate carbon performance of suppliers and compromise solution under each of the evaluation criteria. An illustrative example in an electronics company is presented to demonstrate how to select the most appropriate supplier in accordance with carbon management. To be effective in mitigating carbon risk across the supply chain, the proposed hybrid model can help firms evaluate carbon performance of suppliers for facilitating low carbon supply chain.     

Spectral responses of water level in tidal river and groundwater

The water level of five river stages and seven groundwater wells in the Taipei Basin were analysed by spectral analysis in the frequency domain. The diurnal, semi‐diurnal and quarter‐diurnal tidal components of the Tanshui River appear to relate closely to astronomical tides as K₁, M₂ and M₄, respectively. It is also found that the diurnal component reveals a reversed phase angle in the middle section of the Tanshui River; the phase of the quarter‐diurnal component is also found to be reversed at stations upstream in the Tanshui River and Hsintien Stream. It is believed that these phenomena could be caused by local variation in the river channel topography. The autospectrum and cross‐spectrum between groundwater elevation and nearby river stage were observed to correlate highly with the frequency of the astronomical tides K₁, M₂ and M₄. From the study of the phase shift and time lag of water level fluctuations at river stages and groundwater wells, it was found that the tidal effects of diurnal, semi‐diurnal, and quarter‐diurnal components were significantly different. The relationships between phase and the fluctuated range of atmospheric pressure and water level imply that change in atmospheric pressure does not affect water level fluctuation in the river stage and groundwater well. Copyright © 1999 John Wiley & Sons, Ltd.     

Developing fragility curves for a pile-supported wharf

This study proposes a procedure for developing seismic fragility curves for a pile-supported wharf. A typical pile-supported wharf, as commonly used in the ports of Taiwan, is chosen for demonstration. For a structural model of the wharf, the deck is modeled by shell elements and the Winkler model is used for the pile–soil system, in which the piles and soils are represented by beam elements and springs, respectively. A pushover analysis with lateral loads distributed according to the fundamental modal shape of the wharf structure is conducted to deduce the capacity curve of the wharf. The procedure for developing fragility curves can be explicitly performed using the spreadsheet platform in Microsoft EXCEL. First, quantitative criteria for damage states are established from the sequence of development of plastic zones. Then a nonlinear static procedure called the Spectrum Capacity Method (CSM) is used to efficiently construct a response matrix of the wharf to 24 earthquake events with differing levels of peak ground acceleration (PGA). Based on the damage criteria and the response matrix, the fragility curves of the wharf can be thus constructed through simple statistical analysis. Shifted lognormal cumulative distribution functions are also employed to better approximate the fragility curves for practical applications.     

The concept of “representative tides” in morphodynamic numerical modelling

Process-based numerical modelling of coastal morphodynamics involves model and data reduction schemes in order to cope with computational limitations. Model reduction, on the one hand, may involve the discretisation of an interactive multidimensional, diverse natural system into a reduced set of coupled process-simulation modules. Data reduction schemes, on the other hand, are used to parameterise processes. The use of schematised open-boundary conditions, which are considered as representative in terms of their cumulative morphological effect, is based on the concept of “morphological” or “representative” boundary conditions. Recent model applications show realistic tendencies in terms of depositional and erosional areas. By contrast, the reproduction of characteristic changes in morphology such as the migration of bars, banks and channels is only occasionally achieved. Using field data on observed morphological impact of a single storm event and numerical model data, it is demonstrated that the concept of representative tides may lead to simulations of morphological development lacking natural dynamics. It is proposed that rather than being based on “representative” single tides, morphodynamic models should be applied with open-boundary conditions which take variations in longer-term tidal and meteorological forcing into account.     

Boundary element analysis of Biot consolidation in layered elastic soils

Biot's linear consolidation analysis of three-dimensional fluid saturated layered soils is investigated. The time marching method, uncoupled boundary element method, and successive stiffness method are applied for the numerical modelling of this study. Settlement induced by surface loading and land subsidence due to pumping is studied. The results show that settlement induced by surface loading is mainly influenced by the properties of the soil layer, and that the settlement is larger for soil layers with smaller stiffness and greater thicknesses. The land subsidence induced by pumping is influenced by the properties of the soil layer as well as by the permeability of the pumped layer and the conditions at the top and bottom boundaries. The land subsidence is larger for soil layers with a smaller stiffness, lower permeability of the pumped layer, deeper pumping depth, larger pumping rate and an impervious top surface.