Earth Fissures in Wadi Najran,Kingdom of Saudi Arabia

The formation of earth fissures due to groundwater depletion has been reported in many places in North America, Europe, and Asia. Najran Basin is in the southern part of the Kingdom of Saudi Arabia, and agricultural activities and other groundwater uses have caused significant groundwater depletion there. The basin recently experienced a sudden appearance of numerous earth fissures. An interdisciplinary study consisting of an evaluation of land-use changes, and hydrological, hydrogeological, and geophysical investigations was conducted to determine the reason for the formation of the earth fissures. The hydrological analysis strongly revealed that the groundwater level is decreasing with time. Groundwater depletion would lead to the accumulation of subsurface stress, causing soil hydro-consolidation which creates the ideal condition for the formation of earth fissures. Electrical resistivity, data indicated that there are anomalies in the profiles, which are most probably due to the presence of subsurface topography, another key factor for the formation of the earth fissures.     

Reliability Analyses at Ultimate and Serviceability Limit States of Obliquely Loaded Circular Foundations

This paper aims at determining the failure probability and the corresponding most predominant failure mode at both ultimate (ULS) and serviceability (SLS) limit states of a circular foundation resting on a (c, φ) soil and subjected to an inclined loading. The failure modes at ULS are the footing sliding and the soil punching while those at SLS are the exceedance of tolerable horizontal and vertical footing displacements. The probabilistic results based on the response surface methodology have shown that at both ULS and SLS, there is a load inclination where neither mode of failure is predominant. This inclination corresponds to the loading configurations situated on the line joining the origin and the maximal point of the interaction diagram. In a second stage, the results of a sensitivity analysis showing the effect of the different statistical parameters of the uncertain variables on the value of the failure probability were presented and discussed.     

Particle transport within water-saturated porous media: Effect of pore size on retention kinetics and size selection

The transport and filtration behaviour of fine particles (silt) in columns packed with sand was investigated under saturated conditions by using step-input injections. Three samples of different particle size distributions (coarse medium, fine medium and a mixture of both) were used in order to highlight the influence of the pore size distribution on particle retention and size selection of recovered particles. The main parameters of particle transport and deposition were derived from the adjustment of the experimental breakthrough curves by an analytical model. The higher particle retention occurs in the mixture medium, owing to its large pore size distribution, and the filtration coefficient decreases with increasing flow velocity. Particle size distribution of recovered particles shows a thorough size selection: (i) the first recovered particles are the coarser ones; (ii) the size of the recovered particles increases with increasing flow velocity and enlarger pore distribution of the medium.     

A spatial decision support system (SDSS) for sustainable tourism planning in Johor Ramsar sites, Malaysia

The need for a sustainable approach in tourism development is very often addressed among the academia, the authorities and the stakeholders, as well as the apparent need for tools, which will guide the decision environment in evaluation and planning. This research aims to identify conservation and compatible areas for tourism development in Johor Ramsar sites, using spatial modeling in geographic information system (GIS). The study describes a methodological approach based on the integrated use of GIS and multi criteria decision evaluation (MCE) to identify nature conservation and development priorities among the wetland areas. A set of criteria was defined to evaluate wetland biodiversity conservation and development. Having defined the criteria, the next step was selecting suitable indicators and variables to measure the selected criteria. Subsequently the criteria were evaluated from conservation and tourism development point of view. These criteria were then weighted using the pair wise comparison technique of MCE and the results were integrated into GIS. Several conservation scenarios were generated so as to simulate different evaluation perspectives. The scenarios were then compared to highlight the most feasible and to propose a conservation and development strategy for the wetland areas. The generation and comparison of conservation and development scenarios highlighted the critical issues of the decision problem. This study represents an important contribution to effective decision-making because it allows one to gradually narrow down a problem.     

Undrained behavior of silty sand: effect of the overconsolidation ratio

This experimental study deals with the effect of the overconsolidation ratio on the monotonic undrained shear behavior of silty sand. The study is based on the undrained monotonic triaxial tests for the overconsolidation ratios (OCR?=?1, 2, 4, and 8), with different silt contents ranging from 0% to 40%. The laboratory tests were carried out at an initial relative density of Dr?=?50%. The paper is composed of two parts. The first one presents the tested soils; the second one gives an analysis of the test results and discusses the influence of the overconsolidation ratio on the shear strength of the soil. The test results indicate that the shear strength of the soil increases with the increase of the overconsolidation ratio resulting in an increase of soil dilatancy. The increase in the amount of fines from 0% to 40% increases the phase of the contractancy and consequently reducing the phase of dilatancy of the tested material     

The boundary between stable and unstable shelf in Iraq as inferred from using ideal gravity to elevation ratio

The line of complete compensation, the ideal value for the ratio of gravity to elevation (?0.11 mGal/m) in Iraq, is obtained using gravity data derived from 477 stations. This line is found to separate the stable shelf from unstable shelf. It is also confirmed with the western limit of the basin as shown on the structural map that is constructed at the base of Al-Fath (L-Fars) formation (M. Miocene). The obtained line coincides with the thinnest crustal line shown on the crustal thickness map of Iraq. It is believed that this line may also define the thinnest sedimentary cover in Iraq. The obtained result can be a useful template for a tectonic view of Iraq.     

Air quality and elemental enrichment factors of aerosol particulate matter in Riyadh City, Saudi Arabia

Air particulate matter (PM) samples were collected from June 2006 to May 2007 for determination of chemical elements. PM samples were taken in two size fractions (PM_2.5 and PM₁₀) with MiniVolume air samplers on rooftops of various buildings (15–25 m above ground) in the city of Riyadh. The samples were subjected to X-ray fluorescence analysis to measure major (Na, Mg, Al, K, Ca, Si, P, S, and Fe) and trace elements (Mn, Ni, Cu, Zn, and Ba). The results showed that the PM concentrations were higher for PM₁₀ compared to PM_2.5, indicating that the major PM source was local dust. Also the spatial distribution with high PM concentrations was observed in the south and southeast of the city and the lowest levels were in the center and northeast of the city. This spatial distribution was attributed to different factors such as wind direction and velocity, emission from cement factories, and the presence of buildings, trees, and paved streets that reduce the amount of dust resuspended into the atmosphere. The air quality of the city was found to range from good to hazardous based on PM_2.5, and from good to very hazardous based on PM₁₀. The element-enrichment factors revealed two element groups according to their changing spatial behavior. The first group showed no significant spatial changes indicating they have the same common source. The second group (mainly S and Ni) exhibited significant changes as expected from anthropogenic inputs. The origin of S is possibly a combination of minerals (CaSO₄) and fossil fuel combustion. The source of Ni is probably from fossil fuel combustion.     

Hydrochemistry and pollution probability of selected sites along the Euphrates River, Western Iraq

The hydrochemistry of Euphrates River in the study area which extended from Hit to Al-Saqlawia was studied in order to determine the physical, chemical, and biological properties in addition to the radiation level. Thirty-one stations along the Euphrates River were chosen, 17 of them represented the Euphrates River itself, whereas the other stations are considered as point pollution sources which all empty their load directly in the Euphrates River with an average total discharge of 32 m³/s. Twenty-eight samples of the Euphrates water of both high- and low-flow periods were analyzed for cations (Ca²⁺, Mg²⁺, Na⁺, and K⁺), anions (SO ₄ ⁼ , Cl^?, CO ₃ ⁼ , HCO ₃ ^? , NO ₃ ^? , PO ₄ ^?3 ), H₂S boron, dissolved oxygen, biological oxygen demand, bacteriological tests, radiation levels in addition to physical parameters such as hydrogen number (pH), total dissolved solid, electrical conductivity, total suspended solid, and temperature. This study showed that the cations and anions during periods of high and low flows are within acceptable limit with exceptional Cl^?. Hydrochemical formula during the high flow was Na-Ca-Mg-Cl-SO₄, then it changed into Na-Ca-Mg-HCO3-SO₄-Cl during the low-flow period. The average output cations and anions at downstream (Saqlawiya area) was relatively higher than those of input at upstream (Hit area); this attributed to the natural and anthropogenic activities originated mainly from agricultural activity and population communities around the river. Radiation level for ²¹²Pb, ²¹⁴Pb, ⁴⁰k, ²²⁰Ac, and ²¹⁴Bi showed that the higher level of radiation is concentrated within sediment rather than in water, but the radiation in both is within acceptable limit.     

Dust fallout characteristics within global dust storm major trajectories

Satellite images from 2000 to 2010 were used to identify major dust trajectories within seven major deserts in the world. The fallen dust from these trajectories were collected and analyzed. The fallen dust rates tend to be lower downwind. The average samples of the world's fallen dust are negatively skewed trimodal with dominancy of silt size fractions (61 %). Most of the fallen dust within major dust trajectories is fining downwind. The fallen dust from the eastern zones (Taklimakan, Gobi, and Australian deserts) are characterized by higher percentages of feldspars and clay minerals, low carbonate content, and grain surface area in comparison to the Western zones (Sahara and Arabian deserts). The Western Sahara Desert dust is differentiated by the highest depositional rates and average quartz percentage (66 %). The dust samples in this zone contain low carbonates and grain surface area compared to dust from the Eastern Sahara Desert. The dust samples within Northern Arabia and Ethiopian-south Arabia zones show the highest average of carbonate amounts and grain surface area.