Analysis of long-term fluctuations in stream flow time series: An application to Litani River, Lebanon

Litani River is the largest river in Lebanon and has been affected by several physical and anthropogenic factors that influenced its flow dynamics. By means of the Singular Spectrum Analysis (SSA), the time dynamics of the stream flow of seven sites along the course of Litani River was investigated, extracting for each site the long-term trend. A clear decreasing trend characterizes all the long-term trends of the stream flow. Furthermore, several peaks were identified, consistent with the rainfall rate and snow cover variability.     

Experimental study on the phase transformation point of crushable and noncrushable soils

Two marine calcareous deposits as crushable soils and a siliceous sand as a noncrushable soil were used in this study to compare their monotonic response. Undrained monotonic triaxial tests were conducted on samples, which were prepared in different relative densities and consolidated under various confining pressures. The location of phase transformation point in undrained response of the sands in different initial conditions was evaluated. The effect of important parameters including relative density, confining pressure, particle shape, and particle breakage on phase transformation point was assessed. The input energy applied per unit volume of the soils was used to interpret the shearing response of crushable and noncrushable soils. The results showed that calcareous sands have more tendencies in contraction. Particle shape and breakage play a key role in engineering behavior of crushable soils.     

The dilative intake of poroelastic inclusions an alternative to the Mandel–Cryer effect

This study examines the time-dependent poromechanics behavior of a fluid-saturated spherical inclusion embedded inside a fluid-saturated porous medium with different poroelastic properties. Both media comprise compressible constituents with distinctively defined poroelastic parameters. It is assumed that the inclusion is subjected to a fluid source at the center. The problem is formulated and solved using Biot theory of poromechanics. The contrasts in inclusion and the medium matrix stiffnesses and their respective hydraulic conductivities can be recognized as two competing factors, which affect the inclusion’s rate of expansion during fluid injection. Findings show a certain type of behavior that the inclusion exhibits at the onset of fluid injection when having greater stiffness than the medium matrix, where the inclusion experiences some decrease in the pore pressure. Compared to what announced as the stress redistribution due the Mandel–Cryer effect in earlier researches on dilation of free spheres, this study shows that the associated phenomenon would be likewise attributed to the coupled nature of pressures and deformations in the theory of poroelasticity. However, it is a consequence of the inclusion-matrix stiffness contrast where a dilating free sphere can be regarded as a special case of this new problem. The asymptotic expansions of pressure terms verify the existence of such an effect. The results of this study would put forward very good insight in some engineering applications.     

Origin and geochemistry of Pan-African granitoid rocks in the Gabal Um Shomer area,Southwestern Sinai,Egypt

Geological, petrological and geochemical studies indicated that there are two distinct types of granitoid rocks: older quartz diorites to granodiorite assemblage and younger granitoids, the latter occurring in two phases. The older granitoids have a meta-aluminous chemistry and a calc-alkaline character, with high MgO, Fe2O3, TiO2, CaO, P2O5, Sr and low SiO2, K2O, and Rb. Their major and trace elements data, together with low 87Sr/ 86Sr ratios (0.7029±0.0008) are indicative of I-type affinities. The second-...     

234Th/238U activity ratios in Pacific Ocean bottom waters

The²³⁴Th/²³⁸U activity ratios in the near-bottom waters at a station in the South Pacific have been measured. The activity ratios are close to the secular equilibrium value, ranging between 0.9 and 1.13 (± 8%), suggesting that the rate of removal of²³⁴Th by bottom-water scavenging processes at this station is slow compared to its rate of radioactive decay. The mean²³⁴U/²³⁸U activity ratios in these waters is 1.14 ± 0.02, the same as the reported values for the world oceans.     

Study of surface runoff using physical models

. The profiles of overland water flow as a function of space and time obtained by applying kinematic wave approximations combined with the Darcy-Weisbach resistance formula to laminar flow are presented. Rainfall-excess is assumed to remain constant during a certain period of time. Runoff from surfaces of constant slope, with uniform surface texture, and the effects of different parameters on overland flow have been studied. Comparisons of runoff using Darcy-Weisbach, Manning, and Chezy resistance formulas have been made. It was found that the lower the rainfall-excess rates, the longer the surface runoff starting time, peak time, and smaller the peak runoff value at any distance. It was also found that the overland flow increases rapidly to the peak value, followed by a rapid decline which begins at the moment the rainfall-excess ceases, and then approaches zero slowly. Comparison of the theoretical calculations of runoff with the measured data of the Los Angeles field tests on concrete-paved surface shows good agreement.     

Use of remote sensing and GIS to determine recharge potential zones: the case of Occidental Lebanon

Water recharge from land surfaces into subsurface media is an essential element in the hydrologic cycle. For a small-scale assessment, experimental approaches are usually followed, however, on a regional scale, this assessment needs to be made into a comprehensive picture where spatial data of the different contributing factors are treated. The case of Occidental Lebanon, with an area of around 5,000 km², was studied by the integration of all factors influencing this hydrologic process. Contributing factors are: lineaments and drainage frequency density, lithologic character, karstic domains and land cover/land use. The determination of these factors was carried out mainly by the application of remote sensing. Satellite images (Landsat 7 ETM &; SPOT) and aerial photos were subjected to several treatment processes using a miscellany of software, mainly ERDAS Imagine and ESRI’s Arc View software. Furthermore, exogenetic data, such as topographic and geologic maps, were utilized. The extracted information for these factors was plotted on maps. The integration of the maps in a GIS allowed deciding their interactive effects. However, each factor had its own degree of effect, i.e., weight, which was also determined in this study. This study is an approach to better estimate and provide qualitative assessments of recharge potential (RP). The resultant map shows the highest recharge potentials towards the elevated regions where karstification is well development. It was found that around 57% of the study area is terrain with very high to high recharge rate values, which a considerable amount of precipitated water is allowed to percolate into subsurface rocks.     

Precursors of instability in a natural slope due to rainfall: a full-scale experiment

A full-scale landslide-triggering experiment was conducted on a natural sandy slope subjected to an artificial rainfall event, which resulted in mobilisation of 130 m³ of soil mass. Novel slope deformation sensors (SDSs) were applied to monitor the subsurface pre-failure movements and the precursors of the artificially triggered landslide. These fully automated sensors are more flexible than the conventional inclinometers by several orders of magnitude and therefore are able to detect fine movements (<?1 mm) of the soil mass reliably. Data from high-frequency measurements of the external bending work, indicating the transmitted energy from the surrounding soil to these sensors, pore water pressure at various depths, horizontal soil pressure and advanced surface monitoring techniques, contributed to an integrated analysis of the processes that led to triggering of the landslide. Precursors of movements were detected before the failure using the horizontal earth pressure measurements, as well as surface and subsurface movement records. The measurements showed accelerating increases of the horizontal earth pressure in the compression zone of the unstable area and external bending work applied to the slope deformation sensors. These data are compared to the pore water pressure and volumetric water content changes leading to failure.