Analysis of Rigid Short Caisson with Granular Core Incorporating Nonlinear Interface and Base Responses

It is difficult to construct a conventional shallow foundation in alluvial lowlands because of soft soils and high ground water table. A rigid short caisson foundation with granular core is being proposed for alluvial lowlands. The proposed foundation is analyzed using non-linear hyperbolic stress–displacement responses of homogeneous alluvial deposits. Extensive parametric studies are carried out to study the effects of length ratio (L/d₀), diameter ratio (d/d₀) of granular core with respect to casing, relative stiffness of shaft (α_τ), relative casing base stiffness (α_b), and friction angle of granular material (ϕ_gp) on the load sharing and the settlement of the proposed foundation.     

Precipitation induced stream flow: An event based chemical and isotopic study of a small stream in the Great Plains region of the USA

A small stream in the Great Plains of USA was sampled to understand the streamflow components following intense precipitation and the influence of water storage structures in the drainage basin. Precipitation, stream, ponds, ground-water and soil moisture were sampled for determination of isotopic (D, ¹⁸O) and chemical (Cl, SO₄) composition before and after two intense rain events. Following the first storm event, flow at the downstream locations was generated primarily through shallow subsurface flow and runoff whereas in the headwaters region – where a pond is located in the stream channel – shallow ground-water and pond outflow contributed to the flow. The distinct isotopic signatures of precipitation and the evaporated pond water allowed separation of the event water from the other sources that contributed to the flow. Similarly, variations in the Cl and SO₄ concentrations helped identify the relative contributions of ground-water and soil moisture to the streamflow. The relationship between deuterium excess and Cl or SO₄ content reveals that the early contributions from a rain event to streamflow depend upon the antecedent climatic conditions and the position along the stream channel within the watershed. The design of this study, in which data from several locations within a watershed were collected, shows that in small streams changes in relative contributions from ground water and soil moisture complicate hydrograph separation, with surface-water bodies providing additional complexity. It also demonstrates the usefulness of combined chemical and isotopic methods in hydrologic investigations, especially the utility of the deuterium excess parameter in quantifying the relative contributions of various source components to the stream flow.     

Shallow groundwater in a middle mountain catchment of Nepal: quantity and quality issues

The use of shallow groundwater in middle mountain catchments of Nepal is a recent development. It was only in early 1998 that a number of dug wells had been constructed in the Jhikhu Khola catchment. But their numbers are rapidly increasing. While it seems to be a good way of accessing additional water resources both for domestic (current) and agricultural purposes (future), it is very important that the groundwater resources are not overexploited. Current dug wells are used to abstract groundwater, which is seasonally being recharged by the abundant monsoon rainfall. The water levels responded rapidly to the rainfall and differed according to the location of the well. The water quality parameters indicated that the water of most of the wells was not suitable for drinking purposes without prior treatment. Microbiological contamination is of particular concern, in addition to the high nitrate and phosphate levels. Some wells show elevated turbidity levels, indicating that there is an interaction between the muddy surface water and the water in the well.     

A new model for geosynthetic reinforced soil

It is common to use geosynthetics to reinforce soft-soils or peat with a view to improve their load — settlement response. A new foundation model element — the rough membrane, is proposed to represent the response of the geofabric. Combining this element with Winkler springs and Pasternak shear layers to model respectively the soft soil and the granular fills, a new foundation model is presented for the geosynthetic — granular fill — soft soil system. Analysis of results at small displacement indicates the effect of granular fill to be more and significant than that of the membrane thus confirming large scale model test results of Jarrett and results based on F.E.M. (Boutrup and Holtz). The effect of the membrane increases with the load or decreasing soil stiffness.     

HF transionospheric long range propagation from satellite observed at Florence

Results are presented of a statistical analysis of experimental data on the long range HF transionospheric propagation obtained by using the radio signals emitted by the 1970-34 A satellite, and received at the Florence station, Italy.The satellite emission was generated above the F2 h_max region. The signal, which penetrates the ionosphere and propagates to remote distances, has frequently been received on Earth's surface with low attenuation. Ray-tracing techniques were employed to verify the consistency of the partially-guided low-loss paths.An analysis of the signal amplitude received is presented. An improvement over free-space propagation losses up to 6 dB over ranges of 12,000 km, and up to 8 dB for nearly antipodal satellite passes have been observed, confirming the existence and the importance of guided propagation for long-range communications between satellites and ground terminals, and also for transionospheric links.The role played by horizontal gradients in the ionospheric electron distribution, which are notably present in the sunrise and sunset regions, was investigated. These allow satellite-to-ground long range propagation, as also confirmed by ray-tracing analysis.Experimental observations are presented of the reception occurrence, path-losses and signal amplitude statistics as a function of the geometry of the link and the ionospheric situation; the propagation mechanisms involved are investigated.     

Optimization and design of a continuous biosorption process using brown algae and chitosan/PVA nano-fiber membrane for removal of nickel by a new biosorbent

In this study, nickel ions adsorption from zinc ingot factory wastewater by brown algae (Sargassum glaucescens) and chitosan/polyvinyl alcohol nano-fiber membrane at continuous system was studied. The continuous process included a biosorption reactor and fixed-bed reactor that were optimized by predicting two batch steps with response surface modeling, based on the Box–Behnken in the novel approach. Nano-biosorbent characterized by scanning electron microscopy, Brunauer–Emmett–Teller and Fourier transform infrared spectrometer analysis. Maximum biosorption in this continuous system was at pH 6, biosorbent doses 8 g L^?1 S. glaucescens and 0.48 g L^?1 nano-fiber. The study of the reaction rate showed kinetic data best fitted by pseudo-first-order model with R ² > 0.95 than pseudo-second-order and intraparticle diffusion models. Biosorption equilibrium data were performed using Langmuir isotherm and Freundlich isotherm, Langmuir isotherm fit better with equilibrium data.     

Late Quaternary glaciation in the Nun‐Kun massif,northwestern India

The late Quaternary glacial history of the Nun‐Kun massif, located on the boundary between the Greater Himalaya and the Zanskar range in northwestern India, was reconstructed. On the basis of morphostratigraphy and ¹⁰Be dating of glacial landforms (moraines and glacial trimlines), five glacial stages were recognized and defined, namely: (i) the Achambur glacial stage dated to Marine Oxygen Isotope Stage 3 to 4 (38.7–62.7 ka); (ii) the Tongul glacial stage dated to the early part of the Lateglacial (16.7–17.4 ka); (iii) the Amantick glacial stage dated to the later part of the Lateglacial (14.3 ka, 11.7–12.4 ka); (iv) the Lomp glacial stage dated to the Little Ice Age; and (v) the Tanak glacial stage, which has the youngest moraines, probably dating to the last few decades or so. Present and former equilibrium‐line altitudes (ELAs) were calculated using the standard area accumulation ratio method. The average present‐day ELA of ～4790 m above sea level in the Greater Himalaya is lower than those in the Ladakh and Zanskar ranges, namely 5380 and ～5900 m a.s.l., respectively. The ELA in the Zanskar range is higher than in the Ladakh range, possibly due to the higher peaks in the Ladakh range that are able to more effectively capture and store snow and ice. ELA depressions decrease towards the Ladakh range (i.e. inner Plateau). Peat beds interbedded with aeolian deposits that cap the terminal moraine of Tarangoz Glacier suggest millennial‐time‐scale climate change throughout the Holocene, with soil formation times at c. 1.5, c. 3.4 and c. 5.2 ka, probably coinciding with Holocene abrupt climate change events. Given the style and timing of glaciation in the study area, it is likely that climate in the Nun‐Kun region is linked to Northern Hemisphere climate oscillations with teleconnections via the mid‐latitude westerlies.     

Reconstruction of the eruptive activity on the NE sector of Stromboli volcano: timing of flank eruptions since 15 ka

A multidisciplinary geological and compositional investigation allowed us to reconstruct the occurrence of flank eruptions on the lower NE flank of Stromboli volcano since 15 ka. The oldest flank eruption recognised is Roisa, which occurred at ~15 ka during the Vancori period, and has transitional compositional characteristics between the Vancori and Neostromboli phases. Roisa was followed by the San Vincenzo eruption that took place at ~12 ka during the early stage of Neostromboli period. The eruptive fissure of San Vincenzo gave rise to a large scoria cone located below the village of Stromboli, and generated a lava flow, most of which lies below sea level. Most of the flank eruptions outside the barren Sciara del Fuoco occurred in a short time, between ~9 and 7 ka during the Neostromboli period, when six eruptive events produced scoria cones, spatter ramparts and lava flows. The Neostromboli products belong to a potassic series (KS), and cluster in two differently evolved groups. After an eruptive pause of ~5,000 years, the most recent flank eruption involving the NE sector of the island occurred during the Recent Stromboli period with the formation of the large, highly K calc-alkaline lava flow field, named San Bartolo. The trend of eruptive fissures since 15 ka ranges from N30°E to N55°E, and corresponds to the magma intrusions radiating from the main feeding system of the volcano.