مجله زمین شناسی مهندسی
سال هفتم شماره 2 (پاییز و زمستان 1392)

Marl rocks are from weak rocks which cause some problems due to high swelling and efflorescence capability، low resistance and viability in implementation of engineering structures. creation of thease problems is due to inadequate recognition of engineering geology properties of these rocks. Hence، in this research،to determination the physical and mechanical parameters of marl rocks of safa dam site، experiments of eterberg limits، density، prosity and moisture percent،uniaxial pressure resistance experiment (UCS)، direct shear experiment، surrounded pressure resistance experiment (three axis) and X-ray diffraction (XRD) and X-ray fluorescence (XRF) experiments has performed on samples from excavation of bores. Results of experiments indicate that type and contents of minerals in marls particularly clay minerals are effective factors on engineering geology properties of these rocks.

In this research، the effect of water salinity on geotechnical properties of fine grained soil used in Korchay dam core have been studied. This dam is located in East of Tabriz. In order to the water samples were obtained from half saline water of Ajichay River and saline water of Korchay branch. In the laboratory، several tests such as Atterberg limits، compaction، permeability، compressive strength، direct shear، free swell and dispersion (cramb، double hydrometer and pinhole) were done with distilled، half saline and saline water. Since there are a few percent of active clay minerals in the soil، changes in geotechnical properties of the soil are not considerable. However the results showed the Atterberg limits decrease and permeability coefficient and shear strength parameters increase as pore water salinity increases. Water salinity has no effect on swell time and the soil primary swell finished after 180 minutes with three types of water. Swell percent decreased 32% and increased 23% with half saline water and saline water respectively. Since percent of divanlet cations in half saline water was more than saline water، swell pressure decreased with half saline water more than saline water. Although Na percent in half saline and saline water was high، but no dispersity behavior was observed with them. Most of obtained results have been attributed to increase attractive force between soil particles via salts in water and create flocculate structure in the soil

Tunneling in complex geological and geotecnical conditions is often inevitable، especially in urban areas. The stability analysis and the assessment of ground surface settlement of a shield tunneling are of major importance in real shield tunneling projects. The objective of this research is to determine the collapse pressure of a shallow circular tunnel driven by a Tunnel Boring Machine (TBM) of the Earth Pressure Balance (EPB) type. In this study، analytical methods and three-dimensional numerical modeling with ABAQUS software were implemented to examine the effect of face pressure on the behavior of tunnel. The parameters were calculated using data from Karaj subway- line 2 in a case study. The analytical method used in this study is: Leca-Dormiex which is based on limit analysis stress. The method is based on a translational multiblock failure mechanism. Also، elastic and Mohr-Colomb constitutive model have been used for soil behavior. The results of analytical method and numerical modeling were then compared. According to the findings of this study، face pressure assessed from the analytical method of Leca-Dormiex (upper bound) is the minimum pressure that can be implemented on the face tunnel. Also، analysis shows that with implemention of suggested pressure of analytical method، Karaj subway face tunnel is most probably stable and consequently execution of pre-consolidation methods in this section of the tunnel does not seem to be necessary.

Awareness of Morphological features of rivers is nessesary for recognition of river behavior and optimum aplication of rivers. Overall catchment Physiografy have important role for determination factors such as floods، erodible and sediment mutagenicity. In this study in order to understand behavior of Gamasiab river in the east of Kermanshah provice، geomorphologic features of this river has been considered. Study of engineering geomorphologic properties is done by using existing data from previous studies and according to visit site and field perceptions، study of geology and topography maps. Physiographic properties of catchment، chanels morphologic properties and geology conditions in this region has been studied. In this research، several parameters such as average width، environment، area، hydrogeologic coefficient، catchment form، maximom، minomom and mean higth، and longitudinal slope has calculated. Also status of drainage density of this river investigated and time to focus calculated. Finally this river review and classified according t various classifications for rivers.

A slope overlooking conveyor-belt system in Sungun copper mine complex has been downfall in 2006 and the buildings located on the upper part of the slope has been moved and destructed. Since the conveyor-belt system is an important part of the production process that transports excavated material from original stock to the rock-crusher equipment and to have continuous and firm production in the mining process، this slope must be stable during exploitation period safely. For this purpose، in this paper، first the structural and engineering geology of the area was studied and then the stability risk analysis is performed on the slope. According to the results of the stability analyses، the slope may be unstable against slip and probable instability may lead to damage or destroy conveyor-belt and its tunnel. Therefore، considering technical and cost conditions، slope geometry modification method with incorporation of the other methods are suggested to stabilization the part of slope above conveyer belt. In addition، in the part of slope under conveyor-belt it is suggested to use other slope stabilization methods

Determining the precise shear strength parameters of the fine grained soils is always a difficult task. In order to conduct the shear strength tests and determine the mechanical parameters of the soil، achieving an untreated high quality sample is a problem with a high degree of importance. Therefore، many researchers have attempted during the recent decades to provide relations between strength parameters and soil''s physical characteristics in a specific structure and so to provide the possibility of estimating the strength parameters based on these characteristics. The aim of this research is to estimate the shear strength parameters of a wide region of fine grained alluvial soil located in southern Tehran، Iran. In this regard، the geotechnical data including physical and shear strength parameters of 294 bore holes were firstly collected from the site. Then، the gained data were statistically and independently analyzed. Based on the results of analyzes، the soil''s geotechnical parameters were presented for various depths with an acceptable level of reliability. Moreover، they were considered as a basis for providing a nonlinear regression model to estimate the soil''s shear strength parameters and based on the index physical characteristics of the fine grained soil (water content and plasticity index). The developed model is capable to predict the soil''s drained shear strength parameters، also، other similar soils'' properties with a very good accuracy.

Determination of stress in earthfill dams is one of the most important parameters in dam safety studies. Stress monitoring can be done using total pressure cells which are typically installed during construction. The cell is installed with its sensitive surface in direct contact with the soil to measure total stress of soil and in combination with piezometers to measure pore-water pressure acting in the soil mass. Total pressure cells needs to be installed with care to get reasonable measurements. However، measurements are often incompatible with the theoretical predictions such that pressure cell results usually have some inaccuracies. There are several parameters effecting pressure cell errors however in the present paper it is only focused on the height of embankment and the duration of dam construction. For this purpose a case study، namely Alborz embankment dam located in north part of Iran has been considered. It is an earth dam with clay core with a height of 78 m. Using the monitoring data and considering the effect of embankment height and construction period parameters، a model has been presented to predict the pressure cells error with Gene Expression Programming (GEP) procedure by GeneXProTools 4. 0 software. The computed coefficient of correlation (R2) for the proposed model is 0. 98 showing a good agreement with the monitoring data. The obtained results indicate that the ratio of height difference to time difference for Alborz dam has a significant role in dam pressure cells errors.