ENGINEERING GEOLOGY
Year:2014 | Volume:7 | Issue:1-2|Papers Count:9

The purpose of this study is to produce the landslide susceptibility zonation map for Poulrood earth fill dam reservoir with using AHP/Fuzzy method. To obtain the Fuzzy relations for producing the susceptibility map, a landslide inventory database is obtained by both field surveys and desk studies. To produce susceptibility map with user define and Gaussian functions then landslide related factors such as litology, distance from faults, distance from drainage, slope angle, slope aspect, slope curvature, distance from road, NDVI, earth quick horizontal acceleration and Precipitation were used in the landslide susceptibility analysis. The results obtained in this study showed that the frequency ratio can be used as a simple tool in assessment of landslide susceptibility when a sufficient number of data were obtained. According to landslide susceptibility index for different factors, it was found that the aspect, lithology and drainage system are the most effective factors in the study area. The prediction performance of the susceptibility map is checked by considering quality sum amount. With investigation get amount of quality sum index for two types function in Fuzzy multi criteria decision analysis and attention to good work of operator Gamma in landslide susceptibility mapping, is produced map with user define function and Gamma0.95 operator having topmost quality. The results obtained also showed that the user define function is more reliable then Gaussian function in the study area.

Rainfall induced landslides result in economical losses and casualties all over the world anualy. The main triggering factor of shallow landslides and debris flows in the rainy Province of Mazandaran (northern Iran) is the rainfall events. This study investigates the landslides triggered by rainfall throughout the watersheds of Tajan and Nekarud rivers. Twenty three recorded rain events occurred during the October 2012 to March 2013 in the eastern Mazandaran. Out of the 23 rainfall events during this 6-month period, 15 short to middle rainfall resulted in slope failures. Intensity-duration (I-D) of the rainfall events which induced landslides and debris flows were plotted in logarithmic scale. The threshold of I-D was determined for those rainfall events that induced landslides. This threshold is acquired by statistical analysis of quantile regression via plotting fifth percentile regression line to the lower bound of data of rainfall events that inducing landslides. The 5th percentile equation of the regression line is defined as I=0.51´D-0.60, where I is the intensity (mm/h) and D is the duration (h). Comparing this threshold with the global thresholds obtained through other researches indicates a lower local threshold in this area. The results shows that the rainfall events with shorter duration and higher intensity caused more landslides compare to those with longer duration and thus lower intensity. This might be due to the high drainage potential of the soil mass, and the highly fractured bedrock of marl and marly limestone.

Gotvand-Olya Dam is located near Gotvand City, 25 km north of Shoosh tar city in Khozestan province. The present research aimed at investigation on the influence of outcrop formations in the reservoir on the water quality (concentration of anions and cations, TDS, EC, and concentration of heavy metal strontium) at three levels of 150, 200, and 250 m. The results showed that Gachsaran and Mishan formations release the highest concentrations of anions and cations to the water in all three levels respectively. Concentration of strontium was especially high in the Gachsaran formation which is justified by the significant correlation between strontium and basic and sulfate environments. According to the effect of solubility rate of the Gachsaran formation in the levels of 150 and 200 m on the water quality after filling the dam, EC of water was estimated to be 36632 and 28872 S/cm respectively which is classified as very high saline water. The results have also shown that the salinity drops significantly at the level of 250 m and the water at this level is classified as high saline water. In the case of the effect of the Mishan formation, the classification of water in the three levels are the same as Gachsaran formation, only EC at the level of 200 m is more than the two other levels.

Infiltration of oil materials into the soils has environmental impacts and changes engineering geological properties of soils. This paper has investigated the engineering geological behaviour of contaminated soils from the Tabriz Oil Refinery. The oil materials contaminations were alkenes hydrocarbon that had more than 14 carbon atoms (C14) and is classified in the solid – phase. Based on the results of particle size analysis, there were two types of contaminated soils including silty sand (SM) and lean clay (CL). The results of Atterberg test on CL sample show that the plasticity index (PI) decreased for more contamination and all of SM samples were none plastic. In standard compaction tests, the samples with more contamination was reached to maximum dry unite weight in lower optimum water content. Also, the CBR test results show that with increase of contamination, the CBR was decreased and the reduction for CL sample was more than the SM sample. Based on obtained data from direct shear and consolidation tests, the shear strength parameters (cohesion and internal friction angle) were decreased and the consolidation settlement was increased, respectively.

Evaluation of rock strength is key information on design and construction of infrastructures such as tunnels and dams. Brittle fault zones in which mechanical properties of rocks reduces can be considered as bimrock. The bimrocks consists of large rock fragments with greater strength within fine grained texture with lesser strength. The volume proportion of the fragments with respect to texture affects the strength of bimrocks within the fault zones. In this paper, fault rocks from the Purkan and Namrak faults with different reverse and strike-slip mechanisms, respectively, located in south Alborz range are studied in detail. The volume proportion and uniaxial strength of fault rocks across these fault zones are investigated. The results showed that the volume proportion and distribution of fragment block sizes vary across the fault zone. The volume proportion and uniaxial strength of fault rocks blocks across the Purkan fault zone doesn’t show regular changes while in the Namrak Fault zone these changes have a specific order from inside to outside of the fault zone. This is interpreted to indicate that is related mainly with the amount of fault displacement, width of the fault zone and the presence of micro faults as well as different rock units across the fault zones.

Rock Salt belongs to the group of inorganic chemical sedimentary rocks, which is mainly composed of halite. Salt domes are considered as one of the most important oil traps. Drilling in the salt regions is associated with many problems. Challenging problems in drilling include trapping of the drill pipe string and reducing diameter of the wellbore. Convergence of wellbore’s wall in rock salts is mainly attributable to creep phenomenon. Creep is a time dependent phenomenon that occurs under constant stress. In this research, the effect of confining pressure, deviator stress, and strain rate on creep behavior of rock salt was studied. Furthermore, a mathematical equation was developed to estimate the strain rate in various stress fields. The results revealed that strain rate increases by increasing the deviatoric stress and confining pressure.

Stability analysis of the support systems in tunnels is an important designing issue. Convergence-confinement method is used to estimate the applied load to the installed support system. The behavior of encountered jointed rock mass (which reduces the strength) could be studied, having established the degree of their convergence. Carranza-Torres and Fairhurst having used the latest version of Hoek-Brown correlation presented an analytical method to determine the relationship between factors describing the rock mass strength and mechanical reflections concerning the cylindrical underground spaces. In this article, using similar approach, the ground reaction curve was obtained for Sardasht long tunnel. Having compared the results with those prepared from a numerical method using FLAC 3D, it was clear that the above approach could be used for this tunnel where a safety factor of 3.14 was obtained for the stability of the segmented lining in the face of the applied loads.

The adhesion of clay minerals to metal surfaces leads to clogging of equipment during mechanized tunneling through clay-bearing formations. Among proposed methods to measure adhesion and evaluate clogging potential, Piston Separation Device is found practical and capable to be developed. The Device was designed based on literature and built in this study. Performance of test device was investigated by natural and synthetic materials (water, honey, stick and clayey soil). Statistical study confirmed accuracy and reproducibility of test results. Study of wetness effect in adhesion of Montmorillonite showed adhesion increases with decrease in moisture to twice as much Plasticity Limit (w=2PL). Also it is perceived that clogging will occur in wetness much than twice as much Plasticity Limit but in less not.