Influence of Cyclic Wetting Drying on Collapse Behaviour of Compacted Residual Soil

The climatic zones where residual soils occur are often characterized by alternate wet and dry seasons. Laboratory studies of earlier workers have established that the alternate wetting and drying process affects the swell-shrink potentials, water content, void ratio and particle cementation of expansive soils. The influence of cyclic wetting and drying on the collapse behaviour of residual soils has not been examined. This paper examines the influence of alternate wetting and drying on the collapse behaviour of compacted residual soil specimens from Bangalore District. Results of such a study are useful in anticipating changes in collapse behaviour of compacted residual soil fills. Experimental results indicated that the cyclic wetting and drying process increased the degree of expansiveness of the residual soils and reduced their collapse tendency. Changes in the swell/collapse behaviour of compacted residual soil specimens from wetting drying effects are attributed to reduction in water content, void ratio and possible growth of cementation bonds.     

Three dimensional numerical simulation of residential building on shrink–swell soils in response to climatic conditions

Shrink–swell soils can cause distresses in buildings, and every year, the economic loss associated with this problem is huge. This paper presents a comprehensive system for simulating the soil–foundation–building system and its response to daily weather conditions. Weather data include rainfall, solar radiation, air temperature, relative humidity, and wind speed, all of which are readily available from a local weather station or the Internet. These data are used to determine simulation flux boundary conditions. Different methods are proposed to simulate different boundary conditions: bare soil, trees, and vegetation. A coupled hydro‐mechanical stress analysis is used to simulate the volume change of shrink–swell soils due to both mechanical stress and water content variations. Coupled hydro‐mechanical stress‐jointed elements are used to simulate the interaction between the soil and the slab, and general shell elements are used to simulate structural behavior. All the models are combined into one finite element program to predict the entire system's behavior. This paper first described the theory for the simulations. A site in Arlington, Texas, is then selected to demonstrate the application of the proposed system. Simulation results are shown, and a comparison between measured and predicted movements for four footings in Arlington, Texas, over a 2‐year period is presented. Finally, a three‐dimensional simulation is made for a virtual residential building on shrink–swell soils to identify the influence of various factors. Copyright © 2015 John Wiley & Sons, Ltd.     

Shape of pinch and swell structures as a viscosity indicator: Application to lower crustal polyphase rocks

Pinch and swell structures occur where a more competent layer in a weaker matrix is subjected to layer-parallel extension. In this contribution, we use numerical models to explore the use of pinch and swell structure shape symmetry and asymmetry as a determinant of relative viscosity between layers. Maximum asymmetry is attained when the matrix viscosity on one side is subtly weaker than the competent layer, while the other side is significantly weaker.Our numerical results are directly applied to asymmetrically developed pinch and swell structures in exposed lower continental crust. Here, shape geometries observed in a shear zone comprised of plagioclase-dominated, garnet-dominated and mixed amphibole-plagioclase-dominated bands, reveals that the plagioclase-dominated band is the most competent band and is marginally stronger (2×) and significantly stronger (10–40×) than the fine grained garnet-dominated and mixed amphibole-plagioclase-dominated band, respectively. Based on the experimentally determined viscosity of a plagioclase-dominated material and quantitative microstructural analysis, the viscosity range of the natural rock bands is 2.8 × 10¹⁵ to 1.1 × 10¹⁷ Pa s. Consequently, the assumption that the experimentally-derived plagioclase flow law is an appropriate proxy for the middle to lower continental crust may lead to a viscosity over-estimation by up to forty times.     

大洋涌浪耗散研究及模式应用的进展及主要问题

大洋中涌浪普遍存在且对大气-海洋之间的物理过程有较大影响,但目前对涌浪的耗散过程研究尚不充分。总结了关于涌浪传播和耗散的观测事实,着重指出利用遥感数据推进相关研究的可能性;同时分析可能的物理机制,并论述其在海浪模式中的应用及不足。通过梳理大洋涌浪耗散的研究进展,为今后开展涌浪相关研究提供依据。     

Numerical simulation and preliminary analysis of typhoon waves during three typhoons in the Yellow Sea and East China Sea

In this study,typhoon waves generated during three typhoons(Damrey(1210),Fung-wong(1416),and Chan-hom(1509))in the Yellow Sea and East China Sea were simulated in a simulating waves nearshore(SWAN)model,and the wind forcing was constructed by combining reanalyzed wind data with a Holland typhoon wind model.Various parameters,such as the Holland fitting parameter(B)and the maximum wind radius?,were investigated in sensitivity experiments in the Holland model that affect the wind field construction.Six different formulations were considered and the parameters determined by comparing the simulated wind results with in-situ wind measurements.The key factors affecting wave growth and dissipation processes from deep to shallow waters were studied,including wind input,whitecapping,and bottom friction.Comparison with in-situ wave measurements suggested that the KOMEN scheme(wind input exponential growth and whitecapping energy dissipation)and the JONSWAP scheme(dissipation of bottom friction)resulted in good reproduction of the significant wave height of typhoon waves.A preliminary analysis of the wave characteristics in terms of wind-sea and swell wave revealed that swell waves dominated with the distance of R to the eye of the typhoon,while wind-sea prevailed in the outer region up to six to eight times the R values despite a clear misalignment between wind and waves.The results support the hypothesis that nonlinear wave-wave interactions may play a key role in the formation of wave characteristics.     

太平洋东边界波浪输运

通过计算2000年涌浪指标(swell index)的全球分布,发现太平洋东边界赤道附近区域存在涌浪池.利用ECMWF再分析波浪资料,计算出2000年全球月平均波浪体积输运.比较2000年全球月平均波浪体积输运和2000年QUICKSCAT月平均风场,发现在赤道太平洋东边界涌浪池区域内的波浪输运方向和风向存在很大的差别,两者方向相差大约90°.这进一步验证了该地区涌浪池存在的真实性.研究发现,赤道太平洋东边界涌浪主要来源于北太平洋和南太平洋的西风带对应的海区.在涌浪池区域内分别在2.5°S和2.5°N取两条边界(边界起点为125°W,终点为美洲大陆西边界),计算通过这两条边界进入赤道区域涌浪的Stokes体积净输运量.结果表明,不同月份通过南、北两条边界波浪的净输运量与当月南、北太平洋西风带的风浪强度密切相关.同时指出了,涌浪的体积输运将会对大洋环流系统产生潜在的重要影响.     

利用海底地震仪数据分析台风对海底环境噪音的影响

在海底布设的海底地震仪（OBS）能比较清晰地记录到海底的环境噪音,而台风可以直接或间接的产生在海底传播的弹性波,从而影响海底的环境噪音,并在较大程度上影响OBS的数据记录。本文通过分析台风对工作区的整个影响过程中OBS记录数据的振幅变化,再选择合适的滤波方式,首次发现台风产生的风浪及涌浪在短周期海底地震仪的记录数据上有良好的表现特征,指出了台风对海底环境噪音的另一种可能的影响方式,并由此得出：1）台风产生的风浪和涌浪对海底环境噪音的影响模式不同;2）风浪和涌浪所加强的海底环境噪音的范围和程度不同;3）短周期OBS可以比较清晰的记录涌浪信息,其周期主要是6—8 s,且能量稳定（简称“8秒现象”）。这三点结论为后期的海洋地震研究和海洋学其他研究提供经验与借鉴。     

Effects of wind waves of the Pacific westerly on the eastern Pacific wave transport

There exists a tongueshaped swelldominance pool known as Swell Pool (SP) in the Eastern Pacific region. The monthlymean wave transports (WT) for each month of 2000 is computed using the wave products of ECMWF reanalysis data. By comparing the 2000 monthlymean WT and monthlymean wind field from QUICKSCAT, large differences are found between the wave transport direction and the wind direction over the Eastern Pacific. This may serve as an evidence for the existence of the SP in this region. The work done in this study indicates that the sources of swell in the Tropical Eastern Pacific (TEP) are in the westerly regions of the Southern and Northern Pacific.     

Improvement of calcareous expansive soils in semi-arid environments

The semi-arid climate and geology of Cyprus have caused the formation of calcareous expansive soils on the island. In some areas, swelling has caused serious foundation problems. The industrial by-product Soma fly ash has been used to improve the engineering properties of the soil. Fly ash treatment has shown tremendous potential as an economical method for the stabilization of the soil. Significant reduction in the swell potential and an increase in the hydraulic conductivity values are obtained. Use of fly ash with a small percentage of lime produces even more dramatic results. Cation exchange capacity (CEC) values substantiate the formation of the new pozzolanic reaction minerals which result in more stable silt-sand like structures.     

Swelling Behaviour of Expansive Shales from the Middle Region of Saudi Arabia

Severe and widespread damage in residential buildings, sidewalks and pavements in various parts of the middle region of Saudi Arabia is caused by the development of heave and swelling pressure in the expansive shales in the region. This paper presents the problems and the geotechnical and physicochemical properties of the tested shales. The swelling potential was determined using various methods. Swell tests were conducted under different loading conditions and following different procedures to quantify the amount of vertical swell and swelling pressure. The conventional one-dimensional oedometer swell tests were performed using three different procedures, namely, free swell, constant volume swell and swell overburden. In addition, swell tests were performed in the stress path triaxial apparatus. Tests under different vertical stresses and confinements were conducted. Vertical swell and swelling pressure obtained from the various methods were compared. The reliability of the different methods for estimation of swelling potential is discussed.