Seismic response of adjacent dense and loose saturated sand columns     

K. Adalier  A. -W. Elgamal 《Soil Dynamics and Earthquake Engineering》2002,22(2)

Compaction or densification of loose saturated soils has been the most popular method of reducing earthquake related liquefaction potential. Such compaction of a foundation soil is only economical when limited in extent, leading to a case of an ‘island’ of improved ground (surrounded by unimproved ground). The behavior of the densified sand surrounded by liquefied loose sand during and following earthquakes is of great importance in order to design the compacted area rationally and optimize both safety and economy. This problem is studied herein by means of dynamic centrifuge model tests. The results of three heavily-instrumented dynamic centrifuge tests on saturated models of side-by-side loose and dense sand profiles are discussed. The test results suggest the following concerns as relates to ‘islands’ of densified soil: (1) there is a potential strength degradation in the densified zone as a result of pore pressure increase due to migration of pore fluid into the island from the adjacent loose liquefied ground; (2) there is a potential for lateral deformation (sliding) within the densified island as the surrounding loose soil liquefies.  相似文献   

Improving sub-salt imaging using 3D basin model derived velocities     

R. Stephan Petmecky  Martin L. Albertin  Nick Burke 《Marine and Petroleum Geology》2009

The quality of depth imaging is directly related to the accuracy of the underlying velocity model. In most sub-salt settings, lack of angular illumination severely degrades the resolution and accuracy of velocity information derived from the seismic data itself. A standard approach for building a starting velocity model uses more reliable velocity information outboard of salt which is subsequently extrapolated to populate the sub-salt regions. The shortcoming of this method lies in the assumption that the effective stress observed outboard of salt can be extrapolated beneath salt solely as a function of depth below mudline.  相似文献   

米箭沟尾矿坝料动力特性试验研究     

贺汇文  龙建辉  吕远强 《工程地质学报》2007,15(6):817-822

本文对米箭沟尾矿坝料的组成、结构特征和物理力学性质进行分析,运用振动三轴试验确定尾矿坝料的动力特性参数,分析研究动力特性指标模型,得出动应力、动模量、阻尼比、动剪切摸量随动应变的变化规律,以及动应力与破坏振次,孔压比与振次比的变化规律,并提出符合试验结果的孔压模型,对该尾矿坝的地震动力分析及抗震稳定性评价提供一定科学依据和技术指导。  相似文献   

Water level fluctuations due to earthquakes in Koyna-Warna region,India     

D. V. Ramana  R. K. Chadha  Chandrani Singh  M. Shekar 《Natural Hazards》2007,40(3):585-592

Earthquakes cause a variety of hydrological phenomena, including changes in the ground water levels in bore wells. The Koyna region in the peninsular shield of India, hitherto considered stable in terms of seismic activity, has been active since 1967. More recently, the earthquakes have been localized to the newly impounded Warna reservoir, which is located south of Koyna, where a burst of seismicity occurred in 1993. The region continues to remain seismically active even after four decades. Twenty-one bore wells were drilled around the seismic source volume in the region to observe water level changes resulting from earthquake phenomena. Our studies have shown coseismic anomalous water level changes to be associated with the moderate earthquakes of April 25, 1997 and February 11, 1998. Our results show that changes in the ground water level in bore wells are correlated with micro-earthquake activity, both preceding and following moderately sized earthquakes. The results have implications in enhancing our understanding of earthquake mechanisms.  相似文献   

基于孔隙网络模型的非水溶相液体运移实验研究进展   总被引：1，自引：0，他引：1  

陈家军  杨建  田亮 《地球科学进展》2007,22(10):997-1004

进行多孔介质中非水溶相液体（Non Aqueous Phase Liquids，NAPLs）运移的微观机理研究，微观孔隙网络模型实验是目前应用比较广泛且行之有效的方法。通过网络模型实验，获得对NAPLs在多孔介质中运移更深入的认识。从多孔介质孔隙结构测量、孔隙网络模型制作、NAPLs运移网络模型实验和数值模拟4个方面评述了该方向的研究进展，结果显示测量孔隙结构方法、图像刻蚀技术、可视化测量实验数据方法等有力地促进了本实验研究的发展。分析了孔隙网络模型实验存在的问题以及未来的发展趋势，对开展孔隙网络模型实验研究有一定的启发作用。  相似文献   

Problems in predicting the mobility of slow-moving landslides   总被引：4，自引：0，他引：4  

Th.W.J. van Asch  L.P.H. Van Beek  T.A. Bogaard 《Engineering Geology》2007,91(1):46-55

This paper discusses problems in predicting the mobility of slow-moving landslides. Three case studies are presented here where research has been carried out by the Utrecht University: The La Valette landslide complex in the French Alps, the La Mure landslide in the French pre-Alps near Grenoble and the Hau landslide in Switzerland.To predict field velocities of these slow-moving landslides the viscosity parameters of the material of these landslides were determined by strain-controlled tests in a ring shear apparatus based on Bishop's design at Utrecht University. The viscosity parameters from the laboratory proved to be 10 to 1000 times lower than viscosities obtained from back analyses on the observed velocities in the field. This discrepancy may be explained by the development of negative pore pressures when the plastic material slides over a rigid, wavy slip surface and/or by convergent flow effects. The associated gain in strength results in a higher apparent viscosity.A more detailed analysis is made for the movements of the La Valette landslide. Observed velocities at the La Valette landslide are difficult to describe by one parameter set as the response to a change in groundwater level is not the same during a rise or fall in the piezometric level. This deviation may be explained by rapid changes in total stresses and consequently changes in pore pressure under (partly) undrained conditions. The emerging hysteresis with local and temporal variations in pore pressure makes it difficult to predict in detail the moving pattern of landslides.  相似文献   

Toxicity identification evaluation (TIE) of pore water of contaminated marine sediments collected from Hong Kong waters   总被引：2，自引：0，他引：2  

Kwok YC  Hsieh DP  Wong PK 《Marine pollution bulletin》2005,51(8-12):1085-1091

Marine sediment can function both as a source and as a sink of marine chemical contaminants. The toxicity of contaminated marine sediment can be assessed by toxic evaluation of its pore water, the inter-particle water of sediment, because toxicants in the pore water may be bioavailable to marine organisms. In this study, the toxicity identification evaluation (TIE) was performed to identify the major toxicants in the pore water of marine sediment collected in Hong Kong waters. In Phase 1 TIE, the suspected toxicants were characterized as anions or organic compounds that are either oxidizable or filterable in alkaline medium. In Phase 2 TIE, the suspected toxicants were identified as sulfide (S²⁻) based on the reduction of toxicity due to lowering of sulfide concentrations by experimental manipulations. The mass balance and spiking analyses in Phase 3 confirmed that S²⁻ was one of the major toxicants and that some non-toxic unknown compounds measured by LC–MS, which was removed by C18 solid phase extraction, enhanced the toxicity of S²⁻ in the pore water samples.  相似文献   

基于GIS的孔隙含水层系统三维空间离散方法研究     

贾锦生  陈锁忠 《江苏地质》2005,29(1):5-9

分析了目前孔隙地下水流三维有限差分数值模拟中对含水层系统三维空间离散存在的问题，针对自然界孔隙含水层与隔水层空间分布的不连续性与厚度的不均匀性，研究了基于GIS的孔隙含水层系统三维空间离散实现的技术路线，提出了基于GIS与不规则六面体元的孔隙含水层系统的三维空间离散方法，最大限度地保证了离散体元中含水层类型的单一性，提高了孔隙地下水流模拟模型三维空间离散的精度。  相似文献   

Mechanisms of pore water organic matter adsorption to montmorillonite   总被引：2，自引：0，他引：2  

Thorarinn S. Arnarson  Richard G. Keil 《Marine Chemistry》2000,71(3-4)

The extent and mechanisms of adsorption of marine pore water organic matter to montmorillonite were studied in a series of batch and sequential adsorption experiments. Pore water natural organic matter (pNOM) and easily extracted natural organic matter (eNOM) were collected from Liberty Bay (Puget Sound, WA, USA) sediments. The pNOM and eNOM were each divided into two size fractions using a 1000 D ultrafilter. Batch adsorption isotherms were approximately linear, and the >1000 D fractions of both pNOM and eNOM had larger partition coefficients (K_d) than the <1000 D fractions. A two-component fit of the sequential adsorption data indicated that pNOM and eNOM contained a similar amount of NOM (30%) that was not surface reactive toward montmorillonite. After correcting the batch adsorption K_ds for the non-reactive components, the K_ds estimated by batch and sequential adsorption were identical (2.7 l/kg for >1000 D pNOM and eNOM, and 1.6 l/kg for <1000 D pNOM and eNOM). Mechanisms of adsorption were investigated by systematically changing conditions (pH, temperature and ionic composition) of >1000 D fractions during batch isotherm experiments. Adsorption of NOM was found to decrease with increased temperature, suggesting that hydrophobic effects were not the dominant adsorption mechanisms in this system. Ion exchange was also not an important adsorption mechanism because adsorption increased with ionic strength. The observed enhancement in adsorption with ionic strength indicated that van der Waals interactions were important in the adsorption of NOM. Ligand exchange was found to be a significant mechanism since the presence of SO₄²⁻ in solution reduced the amount of NOM adsorbed. Ca²⁺ enhanced adsorption slightly more than Na⁺, suggesting that cation bridging was involved. The relative contributions of van der Waals interactions, ligand exchange and cation bridging were estimated to be approximately 60%, 35% and 5%, respectively, for adsorption of NOM in a CaCl₂ solution.  相似文献   

A comparative study of representative 2D microstructures in Shaly and Sandy facies of Opalinus Clay (Mont Terri,Switzerland) inferred form BIB-SEM and MIP methods     

《Marine and Petroleum Geology》2014

A combination of Broad-Ion-Beam (BIB) polishing and Scanning Electron Microscopy (SEM) has been used to study qualitatively and quantitatively the microstructure of Opalinus Clay in 2D. High quality 2D cross-sections (ca. 1 mm²), belonging to the Shaly and Sandy facies of Opalinus Clay, were investigated down to the nanometre scale. In addition Mercury Intrusion Porosimetry (MIP) and X-Ray powder Diffraction experiments have been used to extend characterization of the microstructure to the mm–cm scale on bulk volume sample material. Interestingly, both end-member samples of the Opalinus Clay show qualitatively similar mineralogy and pore characteristics as well as a comparable pore size distribution and pore morphology within the different mineral phases and mineral aggregates. Differences between the facies are mainly due to variations in mineral size and mineral amount present in the alternating layers of the different facies. Six different porous mineral phases have been identified and the pores have been subdivided into ten different pore types. Pores visible in the SEM images are most abundant in the clay matrix and these seem to follow a power law distribution with a power law exponent of ca. 2.25 independent of the sample location. Furthermore, all common mineral grains show characteristic porosity, pore shape and pore size distribution in 2D and are proposed to be considered as elementary building blocks for Opalinus Clay. Combined these homogeneous elementary building blocks make up the heterogeneous fabric of the different facies of Opalinus Clay. Based on extrapolation of the power law size distribution in the clay matrix below SEM resolution results in a porosity of 10–25% for clay rich layers (60–90% of clay matrix), whereas sand and carbonate layers show an extrapolated porosity of 6–14%. These extrapolated porosities are in agreement with water-loss and physical porosity measurements performed on bulk material of comparable samples.  相似文献