نشریه زمین شناسی مهندسی ایران
سال هفتم شماره 3 (پاییز و زمستان 1393)

Understanding geological factors affecting landslides in order to understand their mechanisms and methods of stabilization is of utmost importance. In this research using field checking 10 stations were identified and during laboratory tests the mineralogical composition, physical and mechanical properties of slide components were determined. Then, using slide ver5.014 (2004) software static and dynamic stability were analyzed. Slide forming soils are sediments transported along channels that have been diagnosed in seven layers. The seven layers of the soil based on Unified soil classification are four layers namely; SM-SP, SW, SC, SP-SM, and three layers of CL. Clay minerals in the clay layer (CL) are Illite, Kaolinite and Montmorillonite. The most important factors in the occurrence of slides are clay mineralogical composition, toe crusher gradient, active faults, material heterogeneity of slope, and creep. According to the analysis conducted, heterogeneous slopes are prone to rupture. Stations I and IV are the most heterogeneous which represent the minimum safety factors in static mode. Except for stations 5, 9, and 10 other stations have a safety factor of less than one in a dynamic mode.

Ultrabasic rocks constitute a major part of ophiolites in south of Mashhad. Due to increase in the price of property and development of this city in southern highlands and also increasing construction in this area, the study of ultrabasic rocks and their joint system, from the perspective of engineering properties assessment of the rock mass and its effect on the instability of trenches and slopes in this area, has been a matter of great importance. In this study, three different experimental methods have been used to calculate RQD and the results indicate a reasonable concordance. In addition to the determination RQD, the parameters such as the weighted joint density (Wjd) and the block volume (Vb) have been calculated that these methods offers higher specifications of block size. The block size is an important input data in many rock engineering calculations and can be measured using different experimental methods and modeling.

To understand the relationship between engineering characteristics and petrological features, eight samples of the Qom Formation conglomerates from Famenin region in North-east of Hamedan of province were collected. Samples were examined in the laboratory for determining the uniaxial compressive strength, point load strength index, modulus of elasticity, porosity, dry and saturation density. For determining the petrological features, textural and mineralogical parameters, thin sections of samples were studied. In this study, based on the results of statistical analysis, predictive relationships were developed to estimate physical and mechanical properties using petrological features. This study showed that the effects of texture properties on the engineering properties is more important than mineralogical composition. It also became clear that the packing proximity, packing density, grain shape, mean grain size, percentages of cement and matrix are textural features that have a significant impact on the physical and mechanical properties of studied conglomerates. In the present study, multiple linear regression (MLR) was used in four different steps including different combinations of petrological features as input variables for each engineering characteristic. Finally, the best relationships were developed to predict the engineering properties of Conglomerates.

Rock mass properties are one of the important factors affecting the results of the blasting. In this study, in regard to the importance of optimal fragmentation in mining tried to investigate the effect of these properties on the size distribution of fragmentation in the study area including Choghart, Chadormalu and Sechahun iron ore mines. To achieve this purpose, the properties of the rock mass along approximately 1961 meter scanlines and 1771 meter seismic profiles was evaluated in 51 blasting blocks. Also digital image processing technique was used in order to measure the blasting fragmentation. For this purpose with the processing of 1500 images taken from the surface of muck piles was obtained size distribution of fragmentation. Fragmentation changes according to the rock mass properties showed that with increasing of spacing, persistency, aperture, roughness and wavy surface of discontinuities, increasing of uniaxial compressive strength and longitudinal wave velocity in intact rocks and increasing of being close angle between discontinuities strike and free surface strike of blasting blocks to 90°, blasting material size are also increasing. The results indicate that the rock mass properties impact on the size of blasting materials.

Rocks subjected to cyclic weathering processes such as freeze – thaw and salt crystallization may lose their integrity and be deteriorated during time. By increasing in cycle numbers and their intensity, the rate of deterioration will be increased; however, this rate is not the same for different rocks. In this study long term durability of upper red formation sandstones against freeze – thaw and salt crystallization were evaluated using decay function model. By using this model it is possible to obtain some meaningful parameters and determine deterioration characteristics of rocks. For this purpose, 9 specimens of sandstones (specified by A, B, C, CG, S, S1, Tr, Min and Sh) were collected from different parts of the studied area, then their physical and mechanical characteristics including unit weight, effective porosity, water absorption, P-wave velocity, Brazilian tensile strength and point load strength were determined. In order to assess the effect of freeze – thaw and salt crystallization on physical and mechanical characteristics of sandstones, 60 cycles of freeze-thaw test and 20 cycles of salt crystallization test were performed. Then their effects on tensile strength and point load strength were recorded in different cycles. Also, decay constant and half – life of these parameters were calculated. In addition, slake durability index test was performed in three different cases such as standard (wet state), freeze – thaw (performing test on samples subjected to freeze – thaw action) and salt crystallization (performing test on samples subjected to salt crystallization action). Obtained slake durability index from different cases were used to estimate decay constant and half-life parameters. Bye using these parameters (tensile strength, point load strength and slake durability index test) and applying decay function model, long term durability of sandstones against freeze – thaw and salt crystallization were evaluated. Results show that decay constant and half – life can be used in engineering practice for determining long term durability without consuming more cost and time. Also this model indicates that the disintegration rate of sandstones is different and the half-lives obtained from three parameters are different for each sandstone.

In this paper, the seismicity models in Karkheh and Karoun III dam sites before and after impounding are investigated. The results show that location of earthquake epicenters, focal depths and the other seismic parameters around the reservoirs, after filling of reservoir of dams were changed. Also, a good matching has seen between water level and earthquake frequency in both dams. The only difference between the induced seismicity of two dams is the longer delay time of earthquakes response to rising of water level in Karoun III relative to Karkheh; because the permeability of bedrock around the Karoun III is higher than the Karkheh.

The study of the effect of underground cavities on site seismic response have been mainly carried out by analytical methods. The main weakness of these methods are extra simplification in terms of geometry and material properties. Therefore, the need to comprehensive studies in this field, using numerical modeling and experimental methods, particularly considering the real case underground cavities is essential. In the present study, a real case of a subway tunnel, belong the underconstruction subway network of the Karaj city (Iran) was considered. 4 sites along the line 2 of this subway, for which experimatal measurment of ambiant noise have been perfomed, were selected and for them numerical modeling by finite element method were carried out. Results of the numerical modeling are compared with the experimental spectral ratios obtained by Kazemeini et al (2014). The result show that the presence of underground cavities, affect the site seismic response significantly and leeds to apperance of amplification in low and high frequency ranges that increase with increment of tunnel dimention and decrement of the distance to the tunnel axis.

Safe operation of dam has been based on three factors of structural integrity of dam, monitoring of dam and emergency preparedness. Instrumentation and data acquisition by instruments installed in different parts of the structure is one of the methods of monitoring. Jiroft Dam is an arch dam, that its extensometers data set has been used in order to understand the behavior of dam foundation during 20 years period of operation. The dam is 40km north-east of the city of Jirof, has been constructed on the Oligomiocene limestone. Jiroft Dam’s extensometers are from multi-rode type and have a maximum depth of 40m. The extensometers have been installed in the both side of upstream and downstream. Foundation displacements are affected from the reservoir loading and its water level. Foundation uplift in upstream and foundation subsidence in downstream are proportional to the reservoir water level variation. Moving average function used in order to eliminate short-term effects of annual changes in the water level. The highest values of uplift in upstream and subsidence in downstream occurred in the middle block and are about 8 and 3 mm, respectively. Downstream side of some blocks show a subsidence with constant small rate of about 0.1 mm/year. It is necessary to regularly dam monitoring considering continues constant rate of subsidence in mentioned blocks.