Laboratory Investigation of the Influence of Geotextile on the Stress–Strain and Volumetric Change Behavior of Sand

This paper presents the results of triaxial tests conducted for the investigation of the influence of geotextile on both the stress–strain and volumetric change behavior of reinforced sands. Tests were carried out on loose sand. The experimental program includes drained compression tests on samples reinforced with different values of both geotextile layers (1 ≤ Ng ≤ 3) and confining pressure (\(\upsigma_{\text{c}}^{\prime }\)) varying from 50 to 200 kPa. Tests show that the contribution of geotextile is negligible until an axial strain threshold that range between 2.5% for a confining pressure of 50 kPa to lower than 1% for 100 and 200 kPa confining pressure. At higher values of ε_a, geotextile induces a quasi-linear increase in the stress deviator (q) and volume contraction in the reinforced sand. Tests show a negligible influence of the number of geotextile layers (Ng) on the contribution of geotextile to both stress–strain and volumetric change, when normalized with Ng. Tests also show that the contribution of geotextile to the stress–strain mobilization augments with the increase in the confining pressure, while its contribution to the volume contraction decreases with the increase in the confining pressure. The reinforced soil becomes contracting in the case of 2 and 3 geotextile layers.     

Compression Behaviour of Chlef Sand and Transition of Fines Content Using Pressure-Dependent Maximum Void Ratios of Sand

Geotechnical and Geological Engineering - This paper presents a study on Chlef sand to examine the effect of fines content (Fc), relative density (RD) and initial conditions on the compressibility...     

The Use of Fiber to Improve the Characteristics of Collapsible Soil Stabilized with Cement

Geotechnical and Geological Engineering - Urbanization and development in arid and semiarid have brought increased interest in the improvement of water sensitive soils susceptible to volume change....     

The comparison of discrete payment vehicle methods (dichotomous choice) in improving the quality of the environment

Using methods to estimate the value of environmental goods seems to be essential for economic planning and moving toward development. In this paper, using methods of discrete payment vehicle (dichotomous choice), i.e., single-bounded and Double-Bounded Dichotomous Choice, the value of air pollution in Tehran and households’ willingness to pay to improve air quality, in four selected regions (Shahr-e-Ray, Shoosh, Haft-e-Tir and Tajrish) is estimated and the corresponding results of these two techniques were compared. The results showed that the total value of air quality improvement, calculated through two techniques of Double-Bounded and Single-Bounded Dichotomous Choice were, respectively, 2,398,657,500 and 1,492,566,000 thousands Rials (1USD = 35,000R) in a year and weighted mean of each citizen’s willingness to pay to improve air quality, calculated through these two methods was estimated to be 282,192 and 175,596 Rials in a year, respectively. Considering the annual damage to health, for any 1% increase in pollutants and yearly cost of pollution reduction which are, respectively, 1,199,000,000 and 7,336,000,000 thousands Rials, it was determined that citizens’ willingness to pay through two methods includes 20 and 30% of the cost of pollution control, respectively, while 70% of pollution is due to mobile sources. However, citizens’ low willingness to pay is attributed to citizens’ distrust of government policies as well as their ignorance of the harmful effects of air pollution. In general, the results of this study, with regard to the cost of pollution from Single-Bounded Dichotomous Choice are closer to actual market conditions.     

Laboratory Study on the Hydraulic Conductivity and Pore Pressure of Sand-Silt Mixtures

The hydraulic conductivity plays a major role on the excess pore pressure generation during monotonic and cyclic loading of granular soils with fines. This paper aims to determine how much the hydraulic conductivity and pore pressure response of the sand-silt mixtures are affected by the percentage of fines and void ratio of the soil. The results of flexible wall permeameter and undrained monotonic triaxial tests performed on samples reconstituted from Chlef River sand with 0, 10, 20, 30, 40, and 50% nonplastic silt at an effective confining stress of 100 kPa and two relative densities (D_r = 20, and 91%) are presented and discussed. It was found that the pore pressure increases linearly with the increase of the fines content and logarithmically with the increase of the intergranular void ratio. The results obtained from this study reveal that the saturated hydraulic conductivity (k) of the sand mixed with 50% low plastic fines can be, on average, four orders of magnitude smaller than that of the clean sand. The results show also that the hydraulic conductivity decreases hyperbolically with the increase of the fines content and the intergranular void ratio.     

Laboratory Investigation on the Effects of Overconsolidation and Saturation on Undrained Monotonic Shear Behavior of Granular Material

In order to study pore water response and static liquefaction characteristics of silty sand, which has previously experienced liquefaction, two series of monotonic triaxial tests were run on medium dense sand specimens (RD = 50%) at confining pressure of 100 kPa. In the first test series, the influence of the soil saturation under undrained static loading has been studied. It summarizes results of monotonic tests performed on Chlef sand at various values of the Skempton's pore pressure coefficient. Analysis of experimental results gives valuable insights on the effect of soil saturation on sand response to undrained monotonic paths. In the second series of tests, the overconsolidation influence on the resistance to the sands liquefaction has been realized on samples at various values of overconsolidation ratios (OCR). It was found that the increase of overconsolidation ratio (OCR) increases the resistance of sands to liquefaction.     

Experimental Study of Undrained Shear Strength of Silty Sand: Effect of Fines and Gradation

Two strong earthquakes occurred in the region of Chlef (north western part of Algeria) during the last century. From the geological context, there were several great masses of sandy soil ejections on to the ground surface level and severe damages to civil and hydraulic structures. These damages were due to the soil liquefaction phenomenon. The objective of this laboratory investigation is to study the effect of low plastic fines and gradation characteristics on the undrained shear strength (liquefaction resistance) response of sand-silt mixture samples. For this purpose, a series of undrained monotonic triaxial tests were carried out on reconstituted saturated silty sand samples with different fines content ranging from 0 to 50?% at two initial relative densities (D_r?=?20 and 91?%). The initial confining pressure was kept at 100?kPa. The evaluation of the data indicates that the undrained shear strength at the peak (q_peak) can be correlated to the undrained residual strength (S_us), the excess pore pressure (Δu), the fines content (F_c) and the intergranular void ratio (e_s). The test results indicate also that the undrained shear strength at the peak decreases with the increment of the coefficient of uniformity and fines content as well as with the decrement of the mean grain size in the range of 0–50?% fines content for both relative densities (D_r?=?20 and 91?%).     

Modeling the Global Solar Radiation Under Cloudy Sky Using Meteosat Second Generation High Resolution Visible Raw Data

This paper presents an improved model for mapping both hourly and daily values of the global radiation reaching the earth’s surface from satellite data over Algeria. An empirical model with a large spectral band using Linke atmospheric turbidity was chosen to modeling the clear-sky global radiation. The extinction of the solar radiation (absorption plus scattering) is described by an exponential decay function of the cloud albedo and cloud index. To compute these two parameter, we resolve the sun-pixel-satellite radiative model equation using the following hypothesizes. The first one supposes the total transmittance of the atmospheric in the pixel-satellite direction as the ratio of the direct radiation in real sky to the same quantity in case of a very clean sky. The second one estimates that the noise energy reflected back towards the radiometer by molecules of gases in the upper levels of the atmosphere represents about 5 % of the energy measured by the radiometer. The model performance was validated for five radiometric stations across the country for three selected months in 2013 and satisfactory results were obtained and discussed.     

Compounding effects of human activities and climatic changes on surface water availability in Iran

Climatic Change - By combining long-term ground-based data on water withdrawal with climate model projections, this study quantifies the compounding effects of human activities and climate change...     

Semial ophiolite veins of United Arab Emirates―A fluid inclusions study

Calcite and quartz veins in the gabbroic and dunite rocks of the Semial ophiolite (UAE) were selected for fluid inclusion analysis. The inclusions contain both aqueous low-salinity and hydrocarbon-dominated fluids. Mi-crothermometry data indicate that the aqueous fluids contain 0.22 to 1.45 equivalent wt% NaCl and occasionally contain traces of hydrocarbons. Homogenization to liquid occurred between 91 and 152℃. Modeling based on these fluid inclusion observations indicates that the trapping conditions of t...