Electrochemical strengthening of clayey sandy soils

Most previous studies and applications of electrochemical stabilization of soils through electroosmosis have been made on clayey soils. The object of this investigation was to find out if relatively small amounts of clay (1.5%–3.5%, by weight) present in a sandy soil would be enough for stabilization and strengthening to be possible. The results indicate increases of cohesion of the order of 100–200 lb./sq.ft. X-ray analyses of treated soils indicate that sheet structures of clays are reduced and silicates destroyed upon treatment by electroosmosis. Newly-formed minerals also cement the soil. These neoformations include gibbsite, limonite, calcite, hydrohematite, hydrogoethite (hydrolepidocrocite), hisingerite, allophane, allophanoid, gypsum, hematite, magnetite, nontronite, trona and natron (Na₂ CO₃, 10H₂O). The process seems to be irreversible.     

An experimental study of phase equilibria in the systems H2O–CO2–CaCl2 and H2O–CO2–NaCl at high pressures and temperatures (500–800?°C, 0.5–0.9?GPa): geological and geophysical applications

Phase equilibria in the ternary systems H₂O–CO₂–NaCl and H₂O–CO₂–CaCl₂ have been determined from the study of synthetic fluid inclusions in quartz at 500 and 800 °C, 0.5 and 0.9 GPa. The crystallographic control on rates of quartz overgrowth on synthetic quartz crystals was exploited to prevent trapping of fluid inclusions prior to attainment of run conditions. Two types of fluid inclusion were found with different density or CO₂ homogenisation temperature (T_h(CO₂)): a CO₂-rich phase with low T_h(CO₂), and a brine with relatively high T_h(CO₂). The density of CO₂ was calibrated using inclusions in the binary system H₂O–CO₂. Mass balance calculations constrain tie lines and the miscibility gap between brines and CO₂-rich fluids in the H₂O–CO₂–NaCl and H₂O–CO₂–CaCl₂ systems at 500 and 800 °C, and 0.5 and 0.9 GPa. The miscibility gap in the CaCl₂ system is larger than in the NaCl system, and solubilities of CO₂ are smaller. CaCl₂ demonstrates a larger salting-out effect than NaCl at the same P–T conditions. In ternary systems, homogeneous fluids are H₂O-rich and of extremely low salinity, but at medium to high concentrations of salts and non-polar gases fluids are unlikely to be homogeneous. The two-phase state of crustal fluids should be common. For low fluid-rock ratios the cation compositions of crustal fluids are buffered by major crustal minerals: feldspars and micas in pelites and granitic rocks, calcite (dolomite) in carbonates, and pyroxenes and amphiboles in metabasites. Fluids in pelitic and granitic rocks are Na-K rich, while for carbonate and metabasic rocks fluids are Ca-Mg-Fe rich. On lithological boundaries between silicate and carbonate rocks, or between pelites and metabasites, diffusive cation exchange of the salt components of the fluid will cause the surfaces of immiscibility to intersect, leading to unmixing in the fluid phase. Dispersion of acoustic energy at critical conditions of the fluid may amplify seismic reflections that result from different fluid densities on lithological boundaries.Editorial responsibility: I. Parsons     

Evaluation of risk concepts in partial duration series

Conventional design practice aims at obtaining optimal estimates of floods with specified exceedance probabilities. Such estimates are, however, known on the average to be exceeded more frequently than expected. Alternatively, methods focusing on the expected exceedance probability can be used. Two different methods are considered here; the first is based on the sample distribution of true exceedance probabilities. The second is a Bayesian analogue using the likelihood function and a noninformative prior to describe the variability of exceedance probabilities. Appropriate analytical solutions are presented in both cases using the partial duration series approach.     

3-D rheologic model of earthquake preparation (I)—Displacement field

Introduction The rock medium shows mainly elastic character under low-temperature, low-pressure and external force for short duration, yet it shows rheologic property under high-temperature, high-pressure and long-time external force. It is reasonable that the rapid earthquake generating process lasted for tens seconds is analyzed by the elastic theory. As for the earthquake generating process for hundreds or thousand years, nevertheless, the rheologic property of rock must be taken into accou…     

Melting and undercooled crystallisation of felsic xenoliths from minor intrusions (Jebilet massif, Morocco)

Granitic and gneissic xenoliths within microdiorite dykes from the Palaeozoic Jebilet massif (Morocco) contain up to 40% of granophyric intergrowths that occur as films along quartz-feldspar contacts and form an interconnected grain boundary network. The composition of the feldspar megacrysts — i.e. large embayed crystals surrounded by the granophyric intergrowths — implies high-temperature crystallisation (T >900 °C) and the sievetexture (or finger-print texture) indicates that these crystals underwent incipient melting. Moreover, the microstructural position and bulk composition of the granophyre are similar to that of glass in partly molten felsic xenoliths from lavas or pyroclastics. It is argued that the granophyre originated after partial melting of the xenoliths when incorporated into the dioritic magma. Crystallisation of that melt resulted in most cases in the formation of vermicular and/or cuneiform granophyre, which testifies to moderate degrees of undercooling. A few occurrences of plumose granophyre i.e. very thin intergrowths that are close to quartz-bearing spherulites, indicate that some xenoliths crystallised at higher degrees of undercooling.

Together with granophyric xenoliths, a number of microgranular inclusions also occur. These are characterized by phenocrysts of quartz and feldspar in a microgranular groundmass. Finger-print texture in feldspar suggests that these inclusions, like the granophyric xenoliths, underwent ultra-metamorphism and melting. The microgranular groundmass is most probably indicative of crystallisation at lower degrees of undercooling, but the relationships between the two types of xenoliths still remain to be explored in detail.     

岫岩-海城5.4级地震前小震震源机制解与记录特征分析

采用Pn、Pg初始波初动符号，利用乌尔夫网上半球投影，用作图方法求解了岫岩－海城震区（1999年1月－1999年11月29日）主震前辽宁数字地震台网记录（ML≥2.5)的41个小震的震源机制参数。结合前震记录的某些特征，对主震前应力方向的时空变化，震源错动性质进行分析和讨论。     

Spatial probabilistic modeling of slope failure using an integrated GIS Monte Carlo simulation approach

Spatial probabilistic modeling of slope failure using a combined Geographic Information System (GIS), infinite-slope stability model and Monte Carlo simulation approach is proposed and applied in the landslide-prone area of Sasebo city, southern Japan. A digital elevation model (DEM) for the study area has been created at a scale of 1/2500. Calculated results of slope angle and slope aspect derived from the DEM are discussed. Through the spatial interpolation of the identified stream network, the thickness distribution of the colluvium above Tertiary strata is determined with precision. Finally, by integrating an infinite-slope stability model and Monte Carlo simulation with GIS, and applying spatial processing, a slope failure probability distribution map is obtained for the case of both low and high water levels.