Environmental Geotechnical Problems in the Taiwan Strait Area

This article presents general information on environmental geotechnical problems along the Taiwan Strait Tunnel (TST) route including sea-floor characteristics. The term apparent sea-floor is introduced. This layer is due to land erosion washing down and settling in the Taiwan Strait. The depth of ocean water along the Taiwan Strait is estimated. Various soil, and rock types and marine sediments along the coastline of mainland, Taiwan Strait, and Taiwan Islands are presented. Foundation problems under adverse marine environments are discussed.     

Modeling of the Turbulence in the Water Column under Breaking Wind Waves

Past studies have shown that there is a wave-enhanced, near-surface mixed-layer in which the dissipation rate is greater than that derived from the “law of the wall”. In this study, turbulence in water columns under wind breaking waves is investigated numerically and analytically. Improved estimations of dissipation rate are parameterized as surface source of turbulent kinetic energy (TKE) for a more accurate modelling of vertical profile of velocity and TKE in the water column. The simulation results have been compared with the experimental results obtained by Cheung and Street (1988) and Kitaigorodskii et al. (1983), with good agreement. The results show that the numerical full model can well simulate the near-surface wave-enhanced layer and suggest that the vertical diffusive coefficients are highly empirical and related to the TKE diffusion, the shear production and the dissipation. Analytical solutions of TKE are also derived for near surface layer and in deep water respectively. Near the surface layer, the dissipation rate is assumed to be balanced by the TKE diffusion to obtain the analytical solution; however, the balance between the dissipation and the shear production is applied at the deep layer. The analytical results in various layers are compared with that of the full numerical model, which confirms that the wave-enhanced layer near the surface is a diffusion-dominated region. The influence of the wave energy factor is also examined, which increases the surface TKE flux with the wave development. Under this region, the water behavior transits to satisfy the classic law of the wall. Below the transition depth, the shear production dominantly balances the dissipation. This revised version was published online in August 2006 with corrections to the Cover Date.     

Weathering damage evaluation of rock properties in the Bunhwangsa temple stone pagoda,Gyeongju, Republic of Korea

The stone pagoda of the Bunhwangsa temple in Republic of Korea was made of piling small brick-shaped stones. The majority of stone bricks are andesitic rocks with variable geneses. Rock properties of the pagoda roof suffer partial significant deterioration, such as multiple peel-offs, exfoliation, onion-peel-like decomposition, cracks forming round lines and falling-off stone pieces. The stylobates and tabernacles at the four corners are composed of granitic rocks, which are heavily contaminated by lichens and mosses. Some of these contamination marks show dark black or yellowish brown colors by inorganic secondary hydrates. The four tabernacles and northern face of the pagoda body have been exposed to relatively high humidity, which causes light gray efflorescence as stalactites between the northern and western sides of the body. The efflorescences are composed of calcite, gypsum and clay minerals. The stone lion statues at the southeast and northeast corners are made of alkali granite, while the others are lithic tuff. Total rock properties of the pagoda consist of 9,708 stone bricks. Among them, 11.0% are fractured, 6.7% are fallen off, and 7.0% show considerable surface efflorescence, which shows that the pagoda has been highly deteriorated by physical, chemical and biological weathering. The authors strongly suggest long-term monitoring and comprehensive conservation researches.     

Distribution of convection associated with tropical cyclones making landfall along the South China coast

Summary This study examines the convection distribution associated with 18 TCs that made landfall along the South China coast during 1995 and 2005. Cloud-top temperatures from high-resolution satellite imageries of the Geosynchronous Meteorological Satellite 5 are used as proxy of strong convection. It is found that convection tends to be enhanced on the western side of the TC as it makes landfall in 10 of the cases, in agreement with the conclusion of some previous studies. Four cases have stronger convection on the eastern side. This “deviation” from the general rule appears to be related to the TCs being more slow-moving or their interaction of the TC with another land surface prior to its making landfall along the South China coast. For the remaining cases in which no significant asymmetries in convection can be identified, the vertical wind shear appears to enhance convection on the east side.     

An integrated GPS–accelerometer data processing technique for structural deformation monitoring

Global Positioning System (GPS) is being actively applied to measure static and dynamic displacement responses of large civil engineering structures under winds. However, multipath effects and low sampling frequencies affect the accuracy of GPS for displacement measurement. On the other hand, accelerometers cannot reliably measure static and low-frequency structural responses, but can accurately measure high-frequency structural responses. Therefore, this paper explores the possibility of integrating GPS-measured signals with accelerometer-measured signals to enhance the measurement accuracy of total (static plus dynamic) displacement response of a structure. Integrated data processing techniques using both empirical mode decomposition (EMD) and an adaptive filter are presented. A series of motion simulation table tests are then performed at a site using three GPS receivers, one accelerometer, and one motion simulation table that can simulate various types of motion defined by input wave time histories around a pre-defined static position. The proposed data processing techniques are applied to the recorded GPS and accelerometer data to find both static and dynamic displacements. These results are compared with the actual displacement motions generated by the motion simulation table. The comparative results demonstrate that the proposed technique can significantly enhance the measurement accuracy of the total displacement of a structure.     

Environmental impact and geochemistry of old tailing pile from the Sanggok mine creek, Republic of Korea

This study evaluates the pollution load on a creek based on the physicochemical and mineralogical properties of old tailings. The Sanggok mine is one of the largest lead–zinc producers in the Hwanggangri mining district, Republic of Korea. The vertical profile of the old tailings in the mine area can be divided into three units based on color change, and mineralogical and textural variations, as well as physical and chemical properties. Unit I (surface accumulation and oxidized heterogeneous tailing soil) has lower pH and higher Eh than unit II (originally unoxidized dumped tailing soil) and unit III (pebble-bearing bottom soil). The conductivity data indicates that unit I and II have very high values compared to unit III and basement. The mine area consists mainly of carbonate rocks; however, mineral constituents of tailing soil and sediments near the mine were mainly composed of quartz, mica, feldspar, amphibole, calcite, dolomite, magnesite, and clay minerals. Units I and II are characterized by high abundances of siderite, locally pyrite, and dolomite. Precipitates in the mining drainage mainly included: smectite, illite, berthierine, quartz, siderite, hexahydrite, and Ca-ferrate. Among the separated metallic minerals, tailing soils and sediments of highly concentrated toxic metals are found: some pyrite, arsenopyrite, chalcopyrite, sphalerite, galena, malachite, goethite, various hydroxide, and uncertain secondary minerals. Units I and II are characterized by relatively high concentrations of Ca, Fe, Mn and low contents of Al, Mg, K, Na, Ti, rare earth elements (REEs) that correlated with the proportion of secondary minerals. Potentially toxic elements such as Ag, As, Cd, Cu, Pb, Sb, and Zn are highly enriched in the upper two units. This metal concentration can be influenced by changes in the depth because of oxic and suboxic zonal distribution. The removal zone (unit I) has probably migrated below the elevation of the maximum enrichment layer due to deepening of the oxic/suboxic boundary. In most of the materials, the enrichment index is higher than 3.62. The highest value of 42.55 is found in the oxidation surface soils of the tailing pile. An average enrichment index of the profiles and precipitates are 27.62 and 22.62, respectively. Rocky basement soils have an average enrichment index of 6.63, which is influenced by overlying the tailing pile. The water quality and habitat of the Sanggok creek are severely polluted. Polluted surface water may also negatively impact the agricultural soil and groundwater.     

Characteristics of the asymmetric circulation associated with tropical cyclone motion

Summary This paper examines the characteristics of the asymmetric flow associated with tropical cyclone (TC) motion using the Final Analysis dataset produced after the Tropical Cyclone Motion Experiment (TCM-90). The wind data vertically-integrated between 850 and 300 hPa around a TC are first separated into an environment flow and a vortex circulation using the filtering algorithm of Kurihara et al. (1995). The latter is then Fourier-decomposed azimuthally to obtain the symmetric and asymmetric components. Nine TCs that occurred during the TCM-90 Experiment are examined.For generally westward-moving TCs, the wavenumber-1 (WN-1) component is found to dominate the asymmetric flow. However, its pattern does not always exhibit a pair of counterrotating gyres as would be expected from previous modelling results (Fiorino and Elsberry, 1989). Further, the ventilation flow associated with WN-1 does not necessarily point towards the northwest. For a TC undergoing recurvature, the WN-2 flow becomes significant, and even has a larger magnitude than the WN-1 component, starting from about one day before recurvature. Consistent with the modelling results of Williams and Chan (1994), the WN-2 component also rotates counter-clockwise with time.The growth and decay of the asymmetric components result from the interaction between the environmental flow and the symmetric flow of the TC through an energy exchange, in addition to such exchanges between the asymmetric components. Energy generally flows from the environment and the symmetric circulation of the TC to the WN-1 component during intensification but vice versa when the TC is weakening. The growth of the WN-2 component in recurving TCs is due to a transfer of energy from the environment, the symmetric circulation and the WN-1 flow. It is for this reason that the WN-1 flow becomes weaker than the WN-2 flow in such cases. The WN-1 component of fast-moving TCs is found to extract energy from the WN-2 component, in addition to those from the environment and the symmetric flow.With 15 Figures     

Elastic and inelastic drift performance optimization for reinforced concrete buildings under earthquake loads

This paper presents an effective optimization technique for the elastic and inelastic drift performance design of reinforced concrete buildings under response spectrum loading and pushover loading. Attempts have been made to develop an automatic optimal elastic and inelastic drift design of concrete framework structures. The entire optimization procedure can be divided into elastic design optimization and inelastic design optimization. Using the principle of virtual work, the elastic drift response generated by the response spectrum loading and the inelastic drift response produced by the non‐linear pushover loading can be explicitly expressed in terms of element sizing design variables. The optimization methodology for the solution of the explicit design problem of buildings is fundamentally based on the Optimality Criteria approach. One ten‐story, two‐bay building frame example is presented to illustrate the effectiveness and practicality of the proposed optimal design method. While rapid convergence in a few design cycles is found in the elastic optimization process, relatively slow but steady and smooth convergence of the optimal performance‐based design is found in the inelastic optimization process. Copyright © 2004 John Wiley & Sons, Ltd.     

The relationship between administrative hierarchy position and city size development in China

China's urbanization process in the past 20 years has drawn much academic attention, and as a result, many attempts to explain the uniqueness of China's urbanization have emerged. Some argued that Tolley's model (1987), the well known theory explaining global urbanization, or the `Murray-Szelenyi' thesis (1984), which focus on the investigation of urbanization in socialist countries, can be applied in China. Most western literature, however, claimed either a `rural-bias' or an `urban-bias' from the state took place in China's urbanization process. This paper suggests another perspective in the analysis of this process, as it argues that it was the state bias for the allocation of production and human resources in the cities of higher hierarchical ranking that is behind China's urbanization. The objective of the paper is to test it through two hypotheses. The first hypothesis suggests that the higher the city is in the urban hierarchy, the more population it has; and the second argues the higher administrative position a city has, the better social and economic performance it will show. Using statistical data to validate these two hypotheses, this paper attempts to justify the role of `state-bias' of resources allocation and the dominance of the administrative hierarchy in China's urbanization process. Lastly, the paper argues, the state itself is a major factor or source for China's urbanization development.     

Similarity functions D for water vapor in the unstable atmospheric boundary layer

An analysis was performed of experimental data obtained at fixed ship stations during AMTEX 1974 and 1975. This allowed the calculation of the bulk transfer relationships for water vapor and sensible heat in the atmospheric boundary layer for different interpretations of the thickness scale of the boundary layer. It was found that scaling based on the observed thickness, which herein was taken as the height of the lowest value in the potential temperature profile under unstable conditions, produces least scatter in the calculations. The results obtained for the similarity function c( _i ) of the bulk heat transfer coefficient are in good agreement with the results of previous studies. As observed earlier (Brutsaert and Mawdsley, 1976; Mawdsley and Brutsaert, 1977), under unstable conditions the similarity functions D() of the bulk water vapor transfer coefficient are smaller than the corresponding C() functions for sensible heat. In the case of inversion height scaling, the results can be represented by d( _i ) = 0.65 c( _i ).