Utilization of Lime for Stabilizing Soft Clay Soil of High Organic Content

This paper presents the results of geotechnical and mineralogical investigations on lime-treated soft clay soil from Idku City, Egypt, where high organic matters of about 14% exist. Lime was added in the order of 1%, 3%, 5% and 7% by weight and laboratory experiments after 7, 15, 30 and 60 days were conducted including the mineralogical and microstructural examinations, grain size analysis, plasticity limits, unconfined compressive tests, vane shear tests and oedometer tests. The results indicate that soft clay soil of high organic content of 14% can be stabilized satisfactorily with the addition of 7% lime. The results also demonstrate that the changes in the mineralogical contents and soil fabric of high organic lime-treated soft clay improve soil plasticity, strength and compressibility.     

Near-Real–Time GPS-Based Orbit Determination and Sea Surface Height Observations from the Jason-1 Mission Special Issue: Jason-1 Calibration/Validation

The Jason-1 Operational Sensor Data Record (OSDR) is intended as a wind and wave product that is aimed towards near-real–time (NRT) meteorological applications. However, the OSDR provides most of the information that is required to determine altimetric sea surface heights in NRT. The exceptions include a sufficiently accurate orbit altitude, and pressure fields to determine the dry troposphere path delay correction. An orbit altitude field is provided on the OSDR but has accuracies that range between 8–25 cm (RMS). However, tracking data from the on-board BlackJack GPS receiver are available with sufficiently short latency for use in the computation of NRT GPS-based orbit solutions. The orbit altitudes from these NRT orbit solutions have typical accuracies of < 3.0 cm (RMS) with a latency of 1–3 h, and < 2.5 cm (RMS) with a latency of 3–5 h. Meanwhile, forecast global pressure fields from the National Center for Environmental Prediction (NCEP) are available for the NRT computation of the dry troposphere correction. In combination, the Jason-1 OSDR, the NRT GPS-based orbit solutions, and the NCEP pressure fields can be used to compute sea surface height observations from the Jason-1 mission with typical latencies of 3–5 h, and have differences with those from the 2–3 day latency Interim Geophysical Data Records of < 5 cm (RMS). The NRT altimetric sea surface height observations are potentially of benefit to forecasting, tactical oceanography, and natural hazard monitoring.     

Nonlocal period parameters of frequency content characterization for near-fault ground motions

This paper focuses on the frequency property analysis of near-fault ground motions with and without distinct pulses, separately from the Chi-Chi and Northridge earthquakes. Ten scalar period parameters of ground motions, especially several nonlocal period parameters, are considered. Two new nonlocal parameters, namely the mean period of Hilbert marginal spectrum (T_mh) and the improved characteristic period (T_gi), are suggested. Moreover, comprehensive comparison and analysis indicate that T_mh, T_gi and T_avg (average spectral period) can distinguish the low-frequency components of near-fault ground motions; T_m (mean period of Fourier amplitude spectrum) and T_o (smoothed spectral predominant period) represent the moderate- and high-frequency components, respectively. The variance coefficient of predominant instantaneous frequency of Hilbert spectrum (H_cov) can be regarded as an alternative index to measure the non-stationary degree of near-fault ground motions. Finally, the velocity pulses and earthquake magnitude remarkably affect the frequency parameters of near-fault ground motions. Copyright © 2012 John Wiley & Sons, Ltd.     

Nonlinear seismic behaviour of wall-frame dual systems accounting for soil–structure interaction

The aim of this paper is to study the effects of soil–structure interaction on the seismic response of coupled wall-frame structures on pile foundations designed according to modern seismic provisions. The analysis methodology based on the substructure method is recalled focusing on the modelling of pile group foundations. The nonlinear inertial interaction analysis is performed in the time domain by using a finite element model of the superstructure. Suitable lumped parameter models are implemented to reproduce the frequency-dependent compliance of the soil-foundation systems. The effects of soil–structure interaction are evaluated by considering a realistic case study consisting of a 6-storey 4-bay wall-frame structure founded on piles. Different two-layered soil deposits are investigated by varying the layer thicknesses and properties. Artificial earthquakes are employed to simulate the earthquake input. Comparisons of the results obtained considering compliant base and fixed base models are presented by addressing the effects of soil–structure interaction on displacements, base shears, and ductility demand. The evolution of dissipative mechanisms and the relevant redistribution of shear between the wall and the frame are investigated by considering earthquakes with increasing intensity. Effects on the foundations are also shown by pointing out the importance of both kinematic and inertial interaction. Finally, the response of the structure to some real near-fault records is studied. Copyright © 2012 John Wiley & Sons, Ltd.     

Mineral constituents in common chanterelles and soils collected from a high mountain and lowland sites in Poland

This paper reported the results of the determination of Ag, Al, Ba, Ca, Cd, Co, Cr, Cu, Fe, K, Mg, Mn, Na, Ni, P, Pb, Rb, Sr and Zn in Common Chanterelles (Cantharellus cibarius) Fr. and surface soil layer (0-10 cm) underneath the fruiting bodies. Mushrooms and soils were collected from a lowland site in the Hel Peninsula (Baltic Sea coast) and a high mountain site in the Tatra Mountains. The trace elements were determined using validated method and inductively coupled plasma - atomic emission spectroscopy (ICP-AES). Common Chanterelles that emerged at sites poor in mineral nutrients podzols of the Hel Peninsula forests efficiently bioconcentrated several essential trace elements (K, P, Co, Cu, Mn, Na, Zn), while the abundance of those elements in carpophores was around half less compared to specimens from Zakopane region and which emerged in soils much richer in minerals. Common Chanterelles collected at two spatially distant background areas in Poland were only weakly contaminated with metals such as Ag, Cd, Hg and Pb. The maximum tolerable Cd and Pb contents of certain cultivated mushrooms are regulated in the European Union by law and these hazardous metals in C. cibarius were far below tolerance limits set.     

Elemental (C,N, H and P) and stable isotope (δ<Superscript>15</Superscript>N and δ<Superscript>13</Superscript>C) signatures in sediments from Zeekoevlei,South Africa: a record of human intervention in the lake

We used elemental carbon, nitrogen, phosphorus and hydrogen ratios (C/N, N/P and H/C) with total organic carbon (TOC) and total phosphorus (TP) as well as stable carbon and nitrogen isotopes (δ¹³C and δ¹⁵N) to investigate the source and depositional conditions of organic matter in sediments from Zeekoevlei, the largest freshwater lake in South Africa. Typical C/N (10–12), H/C ratios (≥1.7) and δ¹³C_organic values (−22 to −19‰) together with the increase in TOC concentration indicate elevated primary productivity in lower middle (18–22 cm) and top (0–8 cm) sections of the sediment cores. Seepage of nutrients from a nearby waste water treatment plant, rapid urbanization and heavily fertilized farming in the catchments are responsible for the increased productivity. Consistent with this, measured δ¹⁵N_organic values (∼11‰) indicate increased raw sewage input towards the top-section of the core. Although cyanobacterial blooms are evident from the low δ¹⁵N values (∼3‰) in mid-section of the core, they did not outnumber the phytoplankton population. Low N/P ratio (∼0) and high TP (100–2,200 mg l⁻¹) support cyanobacterial growth under N limited condition, and insignificant input of macrophytes towards the organic matter pool. Dredging in 1983, caused sub-aerial exposure of the suspended and surface sediments, and affected organic matter preservation in the upper mid-section (12–14 cm) of the core.     

Assessment of nutrient sources and paleoproductivity during the past century in Longgan Lake,middle reaches of the Yangtze River,China

Total organic carbon (TOC), total nitrogen (TN) and total phosphorus (TP) were determined in combination with stable isotope ratios of carbon and nitrogen (δ¹³C_Org, δ¹⁵N) in a 63 cm sediment core from Longgan Lake, located in the middle reaches of the Yangtze River, China. These geochemical and isotopic records provide a continuous history of lake productivity and trophic state of Longgan Lake since 1890. Variations of δ¹³C_Org, TOC, TN and TP indicate that primary productivity of Longgan Lake increased continuously during the last century and that the trophic state of the lake shifted from oligotrophic to mestrotrophic conditions accordingly. Anthropogenic sources of organic carbon (OC), nitrogen (N) and phosphorus (P) were distinguished from their natural background in the sediments using mass accumulation rates. Element mass accumulation rates suggested increased human activities in the lake’s catchment since 1950s, were especially the utilization of artificial fertilizers amplified the anthropogenic input of N and P into the lake. In the course of the improved availability of dissolved nutrients also primary productivity of Longgan Lake increased, resulting in an increase of the Suess-effect corrected organic carbon isotope ratios. δ¹⁵N of bulk sediments show a marked shift towards lower values around 1950 that has been attributed to the input of nitrogen from chemical fertilizers characterized by relatively depleted isotopic signatures into the lake.     

Biomarker-based paleo-record of environmental change for an eutrophic,tropical freshwater lake,Lake Valencia,Venezuela

The lipids in a sediment core from Lake Valencia, a hypereutrophic freshwater lake in Venezuela, are examined to understand environmental changes over the last ∼13,000 years. From the latest Pleistocene to the earliest Holocene, total organic carbon (TOC) substantially increased from 2.2 to 10%, while total organic carbon over total nitrogen (TOC/TN) decreased from as high as 34 to as low as 10. Correspondingly, the concentration of terrestrially derived triterpenoids markedly decreased, and the dominant n-alkane shifted from C₃₁ to C₂₃ or C₂₅. During the same period, algal biomarkers such as botryococcenes, dinosterol, isoarborinol, C₂₀ HBIs and 1,15C₃₂ keto-ol markedly increased in abundance. These changes suggested a greater contribution of algal organic matter at the onset of the Holocene, which was concurrent with increasing rainfall and the formation of a permanent lake (Lake Valencia) in the Aragua Valley, Venezuela. The age profile of Paq, a n-alkane based proxy, showed large oscillations (0.20–0.81), reflecting historical variations in source strength of submerged/floating vs. terrestrial/emergent OM inputs. An abrupt increase in tetrahymanol abundance at ∼7,260 cal years BP suggests the establishment of an oxic–anoxic boundary in the lake’s water column. After reaching its maximum abundance at ∼2,100 cal year BP, botryococcenes, a biomarker of Botryococcus braunii, gradually decreased to below the detection limit in the uppermost sediments, while different algal/microbial biomarkers such as diploptene, dinosterol and isoarborinol substantially increased. These different historical profiles of algal/microbial biomarkers reflect different responses of source organisms to environmental changes throughout this period. The δ¹³C determinations presented exceptionally enriched values for botryococcene isomers (−7.7 to −15.1‰), indicating the utilization of bicarbonate as carbon sources in an extremely productive ecosystem.     

An experiment on temperature variations in sandstone during biaxial loading

The temperature response to stress–strain variations in rock is useful in developing an understanding of the thermodynamic property of crust. In this study, the temperature of sandstone during loading was investigated using laboratory biaxial testing. By changing the loading patterns, the deformation of a specimen was controlled to produce two distinct modes of strain: volume strain only and shear strain only. These strain modes were produced separately such that the temperature variation associated with the different deformation modes could be analysed. Experimental results indicate that temperature, as a scalar quantity, is notably sensitive to rock deformation. In the case of the volume strain, the temperature variation is positively correlated with the variation in the bulk stress. The temperature rises with the increase in hydrostatic pressure, and vice versa. In the case of the shear strain, experimental results repeatedly show two characteristics: firstly, there appears obvious increase in temperature in the area of pure shear strain, which is most likely related to local plastic deformation; secondly, the temperature drops in the area of tension during loading, whereas the temperature rises within the area of compression. This is to say, the state of crustal stress–strain should be obtained through the measurement of rock temperature.