نشریه زمین شناسی مهندسی ایران
سال پنجم شماره 1 (بهار و تابستان 1391)

The abundance of granitic rocks and their frequent use as ornamental stones and Malones has made the recognition of their engineering geological properties important. Recognizing the diverse lithological, physical and mechanical properties of these rocks is also of importance because they are used in the construction of dams, and foundations of residential and commercial structures in different regions of the country. In this research, based on field studies in the north and north- east Boroujerd, appropriate Boroujerd granite mass crops were identified and sampled. Through studying thin sections taken from 7 mines the textual, mineralogical and geological characteristics of granites were determined. According to the results, Boroujerd granite masses composed of granodiorite, monzogranite, white granite and tonalite. Also petrological studies show the microscopic fractures caused by the active tectonic zone. In this study, using standard tests, the physical and mechanical properties of 224 samples of granite were determined. According to Anon's classification the density of Boroujerd granites are medium to high. Water absorption in most samples is less than 1 percent. Their maximum hardness is 53 and at least 39. The highest and lowest tensile strength when dry is 3.6 and 12 MPa. Based on maximum uniaxial compressive strength and elasticity ratio, and according to the engineering classification of intact rocks Boroujerd granites are classified in the categories of CL and BL. The obtained relations between lithological, physical and mechanincal properties and proper correlation coefficient can be used in geological studies and civil engineering projects of the area.

The site for Sardasht dam and its hydraulic power plant contains metamorphic slate rock masses with distinguished cleavage surface characteristics leading to reduced rock mass strength. Hence, stability analysis of the surrounding structures, underground spaces and slopes, is of great importance. Stability analysis of the slope, adjacent to the dam, was carried out for the three conditions of without cleavage, considering cleavage and inclusion of fractures zones, based on limit equilibrium and finite difference methods using SLIDE and FLACSLOPE 2D codes, respectively. The results indicate that the slope slide was not found safe in the presence of cleavage and fractured zones. For assurance, further statistical analysis was also carried out on the slope stability. The accumulative distribution function indicated that the confidence coefficient for 68% of the data was found to be less than 1.7, which confirms the extreme influence of cleavage on the slate rock mass strength. Therefore, the 1:6 slope presented in the drilling map preliminary report is unstable.

Collapsible soils, when saturated, without any change in applied stress or any vibration, undergo large settlements. This will cause damages to the building foundations, roads, rail road, dams, pipelines which may lead to fracturing and collapsing. Collapsible soils are scattered all over the world. In Iran they can be found in central and eastern part of the country. In the present research, the North Eastern of Mashhad has been studied in order to identify the collapsibility potential of soil in this area. This was necessary since new buildings construction such as subway of underground transportation system is in process. These buildings are commonly affected by vibration forces transmitted from this system. Physical and mechanical parameters of the collapsible soil in this area have been evaluated and various collapsibility criteria are compared. The laboratory test results indicate the collapsibility of the soil potential. Also field tests were performed to evaluate the mechanical properties and collapsibility potential of soils. The results have confirmed the possible collapsibility of sub-soil in this area, which may lead to unavoidable damages to the buildings and rail way system.

Soil abrasivity and TBM component wear issues is one of the most important factor in success of this type of projects. Despite of rocks there are very few test methods to describe the abrasive characteristic of soils. It can be mentioned that impossibility of reliable estimation of soil abrasivity on mechanical tunneling is one of the engineering geology science gaps in tunneling and drilling industry. In this paper the influence of some important parameter on soil abrasivity (soil particle size, equivalent quartz content and water content) are studied by use of LCPC standard and the abrasiveness of Tabriz metro line 1 soil are estimated. The results indicate by increasing of soil particle size the abrasivity trend to be increased. The influence of water content on abrasivity was not the same in all of the samples. The presence of water in some samples cause to increase and in the other sample cause to decrease of abrasivity. With increasing the equivalent quartz content (EQC), the abrasivity of soil depends on grain size has trend to increase with power relation. Evaluation of Tabriz metro line 1 soil samples shown it is very abrasive and medium abrasive in dry and saturated condition respectively.

Empirical relationships between earthquake magnitude and frequency of occurrence, e.g. Gutenberg - Richter’s relationship, have been presented for a special region using limited historical data. These relationships usually involve many sources of uncertainty (frequency of occurrence, magnitude, etc.). Therefore, it is necessary to use probabilistic simulation for determination of earthquake occurrence frequency instead of the deterministic one. In the present, Monte Carlo simulation, as the most preferred approach for probabilistic simulation, is used to evaluate seismic potential of Iran provinces. On the basis of probabilistic analyses, the frequency of earthquake occurrence by assuming a normal distribution of magnitudes and different occurrence probability are determined for 20 seismotectonic provinces of Iran. Furthermore, it can be concluded that the province situated in southwest of Iran (i.e. region number 12) is the most seismically active region and province number 16 (situated in the northwest of Iran) is the least seismically active region of Iran.

Beheshtabad water conveyance tunnel, which is 65 kilometers in length and 6 m in final diameter, is studied to convey water from Karun river to central part of Iran. In this study the first 17 km of the tunnel is examined to select the most efficient excavation method. This interval of the tunnel was divided into three zones based on geological and geomechanical conditions, these three zones are from 0 to 5450, 5450to7800 and 7800 to17000 meters.
Selection of the optimal excavation method was a complicated decision to make since it required many factors to take into account. In this paper, a model was first constructed using Fuzzy Analytical Hierarchy Process (FAHP). Three excavation methods of drill and blast, road header and TBM were investigated based on the foregoing model, in which geological, geomechanical, economical, operational and environmental conditions as well as geometry of the tunnel and management factors were considered. Results showed that TBM scored the most point in all three zones. It is therefore, recommended a TBM to be used.

Dust storm events carry a huge amount of aerosols to the atmosphere. These particles reduce air quality and can cause breathing, allergic, cordial problems. This environmental disaster increasingly outbreaks in arid and semiarid areas (e.g. Middle East) in recent years. Monitoring from space using remote sensing is one of the most effective and extensive techniques for dust storm detection. Terra MODerate resolution Imaging Spectroradiometer (MODIS) data have been utilized in this study for dust detection and classification in the Middle East. Dust particles emissivity differences in thermal infrared signals can discriminate the dusty from non-dusty pixels. D-parameter is calculated by combination of visible reflectance properties and Brightness Temperature Difference (BTD) between 11 and 12 µm channels. D-parameter is examined were using 28 satellite images (expanded in 2008 to 2009) and showed that it is very effective approach for dust area detection. Relation between D parameter and visibility (obtained from 41 synoptic stations) was investigated. The results showed that there is an exponential relation with R=0.68 between them. This relationship can retrieved the visibility from D parameter with Mean Percent Absolute Error=45.6%. According to the complicacy of problem and vast study region, R=0.68 and MPAE=45.6% seems very good. Hence we utilized this developed exponential relationship to retrieved visibility maps in Middle East from D-parameter maps. Then these generated visibility maps were classified to the different dust storm classes. This classification method was developed using the combination of different dust classification methods according to the visibility values. In this classification method, the dust storms were classified to 5 different classes (Sever Dust Storm¡ Medium Dust Storm¡ Light Dust Storm¡ Blowing Dust and Dust in Suspension).

The deformation modulus of rock mass (Em) is the most representative parameter of the pre-failure mechanical behavior of the rock material and of the rock mass .Due to the high cost and measurement difficulties of in situ tests, the predictive models using regression based statistical methods, back propagation neural networks (BPN) and fuzzy systems are recently employed for the indirect estimation of the modulus .Among these methods, the BPN has been reported to be very useful in modeling the rock material behavior, such as Em, by many researchers .Despite its extensive applications, design and structural optimization of BPN are still done via a time-consuming reiterative trial-and-error approach . However, in this research, the genetic algorithm (GA) is utilized to find the optimal parameters of BPN, such as the optimal number of neurons in hidden layer, learning rates and momentum coefficients of hidden and output layers of network. Then, the result is compared with that of trial-and-error procedure . For the purpose, a data base including118 data sets was employed from six dam sites locations in Zagros Mountains of Iran. According to the results, the GA -ANN model has higher accuracy than the trial-and-error model in the estimation of Em.