Journal of Engineering Geology

Impact of Fiber Reinforcement on Deformation Characteristics of Cemented Sand-Gravel Mixtures

Amir Hamidi

This paper describes triaxial compression tests conducted to determine the effect of fiber inclusion on stiffness and deformation characteristics of sand-gravel mixtures. Tested soil was a mixture of Babolsar sand from the shores of the Caspian Sea and Karaj River gravel. Portland cement was used as the cementing agent and fibers 12mm in length and 0.023mm in diameter at 0%, 0.5% and 1.0% were added to the mixtures. Triaxial tests were performed on saturated samples in consolidated drained and undrained conditions at confining pressures of 100, 200 and 300 kPa. Deviatoric stress-axial strain, volumetric strain-axial strain, pore pressure-axial strain curves with deformation and stiffness characteristics were investigated. Tests results show that fiber addition increased peak and residual shear strength of the soil. Fiber addition resulted in an increase of the maximum positive and negative volumetric strains. In undrained condition, fiber inclusion caused increase in initial positive pore pressure and final suction. It has also been observed that fibers decreased initial tangent stiffness of the cemented sand-gravel mixture.

Evaluation of the Lineaments and Faults in the Alborz Province by Remote Sensing

Alireza FarrokhNia

The studied region in this research (Alborz province) is structurally located in Alborz poly_orogenic system of northern Iran. The purpose of this research is combining the remote sensing and geology sciences to show fault lineaments by analyzing satellite data in a vast region and also comparison between lineaments layer and recognized faults in geology maps. Firstly, two scenes of Landsat ETM+ satellite images with 164-35 and 165-35 numbers were mosaicked and also according to coordinates of research area (46^◦ 30´ to 48^◦ east longitude and 34^◦ to 35^◦ north latitude degree) have been crop. Then with remote sensing methods such as combination of bands, filtering, NDVI index to reconstruction the vegetation, principal components analysis (PCA) and band relativity in gray scale and color images have been analyzed the satellite images. Finally, by using the above mentioned methods, the map of fault lineaments and map of lineaments density for Alborz province have been prepared and compared with recognized faults.

Effect of Mineralogy on Durability and Strength of Hornfelsic Rocks under Acidic Rainfall in Urban Areas

Davood Fereidooni

In order to assess mineralogical composition influence on durability and strength of rocks, four samples of hornfelsic rocks were selected from southern and western parts of the city of Hamedan, west of Iran. These rock samples were subjected to mineralogical, physical and mechanical tests in the laboratory. Also, they were evaluated in 15 cycles of slake-durability testing in different pH of sulfuric acid solutions and XRD analysis. Based on the results, the type and amount of minerals, their density and hardness had an influence on the uniaxial compressive strength and the slake durability index of tested rocks. That means, presence of non-dissolved minerals such as graphite in studied rocks, decreases Unconfined Compressing Strength (UCS) but increases the slake durability index. The results of slake-durability test indicated that weight loss of the samples at initial cycles was found to be higher than the end cycles. Also, in these samples, initial minerals in the fresh samples were not exchanged by secondary minerals such as clay minerals. Therefore Hamedan hornfelsic rocks are approximately resistant when were put under accelerated chemical weathering and degradation in the laboratory and natural chemical weathering.

New Analytical Approach for Reservoir Stress Approximation Based on Acid Fracturing Data

M Asef

In this research attempts were made to estimate the in-situ stresses acting on a hydrocarbon reservoir based on routine activities of acid injection in oil reservoir. It was found that the relation between the re-opening pressure of fracture and principal in-situ stresses can be estimated using rock mechanics equations for the circular underground cavities. An appropriate relation between the maximum and minimum horizontal principal in-situ stresses and reservoir parameters such as permeability, reservoir pressure, Young’s modulus, acid viscosity, injection flow rate and etc., was developed by using the well-known Darcy equations for fluid flow in porous media. Accordingly, knowing the flow rate of acid injection during well operations and some other reservoir parameters, in-situ stresses may be estimated. The method was then successfully applied to a large carbonate reservoir as a case study in south-west of Iran. Maximum and minimum effective horizontal stresses were calculated by employing the presented method.

The Effect of Wetting-Drying Cycles and Plasticity Index on California Bearing Ratio of Lime Stabilized Clays

sahasan naeini

This paper aims to present an experimental and numerical study on the effect of wetting-drying cycles and plasticity index on the California Bearing Ratio (CBR) of lime stabilized clayey soils. The numerical analysis was carried out based on finite element method for comparison between results of experimental and numerical studies. Three clays with different plasticity indices were mixed with various amounts of hydrated lime and compacted at optimum water content. The CBR tests were conducted to the soils and admixtures after specified curing time and various numbers of wetting-drying cycles. The experimental results indicate that addition of lime content up to 4% causes significant increase in the CBR values. Based on the obtained results the CBR decreases during the wetting phase and increases during the drying phase of each cycle. After 3 cycles the CBR values of lime stabilized clayey soils are increased. Also, for stabilized clays by increasing the plasticity index, the CBR values resulted by increase of lime content are decreased. The comparison between numerical and experimental analyses indicates a good agreement between results.

Risky Pollution Index: An Integrated Approach Towards Determination of Metallic Pollution Risk in Sediments

T Nasrabadi

In contrast with Mobility Factor (MF) and Risk Assessment Code (RAC) indices, I_R attributes a risk share to metal species bound to reducible and oxidizable phases which are totally neglected in both of the two above-mentioned indices. In other words, besides the absolutely mobile fractions, the potentially mobile ones are also regarded in risk evaluation process elaborated by I_R. The different structure of the newly-developed index may prevent risk level underestimation especially in case where a remarkable percent of bulk concentration is accumulated within reducible and oxidizable phases. The independency of the index value to the bulk concentration makes it possible to discuss the potential risk in different levels of bulk concentration. Furthermore, the index capability in indication of risky pollution, regardless of the pollution source type, may prevent the probable misleading caused by distinct separation of bulk concentration into geopogenic and anthropogenic portion

Improving Physical Characteristics of Collapsible Soil (Case Study: Tehran-Semnan Railroad)

Reza Ziaie_moayed

Collapsible soils could widely be found in central part of Iran and has caused lots of problems for roads and railroads in that region. Appearance of wide cracks in the collapsible soil near the Tehran-Semnan railroad tracks has caused some worries regarding the safety and performance of the railroad. However, due to the high traffic of the railroad, it is impossible to block the road for remedy. Therefore using injection method was found the most suitable alternative to improve the soil along railroad. The results of field and laboratory tests revealed that the injection of lime has better effects on improving soil characteristics than the other materials. It will significantly decrease the collapsibility potential of soil in saturated condition and will cause an increase in loading capacity of soil. Lime injection was suggested as the most appropriate solution for projects with similar geological condition.