Stabilization of clayey soils with Tunisian phosphogypsum: effect on geotechnical properties

Phosphogypsum and cement have been reported to improve the physicochemical properties of clayey soils. The present study aimed to investigate the behavior of various soils with different particle sizes and chemical and mineralogical compositions in the presence of phosphogypsum and cement mixed at various proportions. These hydraulic binders were assayed on three different soil samples, and their effects were examined using a battery of standardized tests, including the Atterberg limit, uniaxial compressive strength, Californian Bearing Rate (CBR) test, thermogravimetric analysis (TGA), microstructure observation (SEM), and X-ray diffraction tests. The results revealed a significant effect associated with the variation of phosphogypsum content in the soils. Keeping the cement content constant in the mixture, the continuous addition of phosphogypsum was noted to allow shifting the domain of plasticity to the highest water contents, which reduces the sensitivity of the soil to water and to increase the strength of soil. An increase of CBR index with the addition of phosphogypsum and cement is obtained. This treatment could have positively influenced the optimum moisture content and the maximal dry density. The mixture of soil-phosphogypsum and cement could give new forms such as ettringite and hydrate indicators of the improvement of the mechanical properties of the soil. This improvement varies from one soil to another, depending on its granularity and its mineralogy. The mineralogical composition of the soil, particularly kaolinite, amount, and size grading, have direct effects on the physical and mechanical properties of the soils under investigation.     

Improving Scatterometry Retrievals of Wind in Hurricanes Using Non-Simultaneous Passive Microwave Estimates of Precipitation and a Split-Step Advection/Convection Model

One of the current problems in the accurate estimation of over-ocean wind from scatterometry observations is the proper accounting for precipitation. Specific cases such as hurricanes are particularly difficult, because precipitation in the eye wall and rain bands can be quite heavy, and therefore, affect the scatterometer signatures so drastically that a category-4 hurricane can appear, to the scatterometer, to have category-1 winds. We have developed an approach to infer and account for the signature of the precipitation from non-simultaneous passive-microwave measurements of rain, with the help of geostationary IR measurements. In this note, we describe the basic approach, and the results of applying it to the data taken by the Tropical Rainfall Measurement Mission Microwave Imager measurements several hours before and after the QuikSCAT observation of Hurricane Rita in September 2005. We also describe how we are enhancing the approach with more realism in the assimilation of the IR information.     

Determination of the initial firing conditions of Ayyubid/Mamluk painted pottery excavated from northern Jordan

A combination of different scientific techniques has been utilized to estimate the initial firing temperature and kiln atmosphere of a collection of Islamic painted sherds excavated from an archaeological site in northern Jordan. Scanning electron microscope investigation of samples refired at different temperatures proves that the pottery was fired at around 750°C in an oxidizing atmosphere. Similar results were obtained by the thermal analysis study using thermogravometric, differential thermogravemetric and differential thermal analysis and by the temperature-minerological scale analysis. The obtained results shed light on the manufacturing techniques adopted by the Islamic potter of the period. © 1999 John Wiley & Sons, Inc.     

Predicting the geotechnical performance of Lisan Marl using finite element analysis,Dead Sea area

This paper investigates the changes in Lisan Marl properties upon leaching the soluble minerals and collapse potential. Finite element method was used to model dike construction and the relationships between soil parameters. To validate the chosen model and obtain the required input data, one dimensional oedometer and drained direct shear tests were carried out. The models were further validated by comparing the results with available published data. The results proved that the chosen model is efficient in assessing the geotechnical behavior of the studied soil.     

Modified DRASTIC assessment for intrinsic vulnerability mapping of karst aquifers: a case study

Groundwater in karstic aquifers can be dangerously sensitive to contamination. In this paper, DRASTIC assessment was modified and applied, for the first time, to address the intrinsic vulnerability for karst aquifers. The theoretical weights of two of DRASTIC’s parameters (aquifer media and hydraulic conductivity) were modified through sensitivity analysis. Two tests of sensitivity analyses were carried out: the map removal and the single parameter sensitivity analyses. The modified assessment was applied for the karst aquifers underlying Ramallah District (Palestine) as a case study. The aquifer vulnerability map indicated that the case study area is under low, moderate and high vulnerability of groundwater to contamination. The vulnerability index can assist in the implementation of groundwater management strategies to prevent degradation of groundwater quality. The modified DRASTIC assessment has proven to be effective because it is relatively straightforward, use data that are commonly available or estimated and produces an end product that is easily interpreted.     

Monitoring of Dead Sea water surface variation using multi-temporal satellite data and GIS

Remote sensing (RS) and geographic information systems (GIS) are very useful for environmental-related studies, particularly in the field of surface water studies such as monitoring of lakes. The Dead Sea is exposed to very high evaporating process with considerable scarcity of water sources, thus leading to a remarkable shrinkage in its water surface area. The lake suffers from dry out due to the negative balance of water cycle during the previous four decades. This paper discusses the application of RS, GIS, and Global Positioning System to estimate the lowering and the shrinkage of Dead Sea water surface over the period 1810–2005. A set of multi-temporal remote sensing images were collected and processed to show the lakes aerial extend shrinkage from 1973 up to 2004. Remote sensing data were used to extract spatial information and to compute the surface areas for Dead Sea for various years. The current study aims at estimating the fluctuation of Dead Sea level over the study period with special emphasis on the environmental impact assessment that includes the degradation level of the Dead Sea. The results indicated that there is a decrease of 20 m in the level of the Dead Sea that has occurred during the study period. Further, the results showed that the water surface area of the Dead Sea has shrunk from 934.26 km² in 1973 to 640.62 km² in 2004.     

A site-testing campaign at the Calar Alto Observatory with GSM and DIMM instruments

The main atmospheric optical parameters have been measured at the Calar Alto Observatory simultaneously using the Generalized Seeing Monitor (GSM) and a Differential Image Motion Monitor (DIMM) during several nights in 2002 May. The temporal evolution of the seeing, the outer scale, the isoplanatic angle and the coherence time have been analysed. There is excellent agreement between the seeing measurements provided by the two instruments, particularly when the turbulence is slow. Indeed, the GSM measurements are corrected from the exposure time when the DIMM data were recorded for at least 5 ms. From almost three years of DIMM (at 5 m height above ground) data, a seeing of 0.92 arcsec with a standard deviation of 0.31 arcsec has been obtained for this site. The outer scale     , the isoplanatic angle  θ₀  and the coherence time  τ₀  measured with the GSM are well fitted with log-normal distributions with median values of 22.9 m, 2.27 arcsec and 3.7 ms, respectively.