Journal of Engineering Geology

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One of the geotechnical hazards in the tunnels under high overburden and high in situ stresses is the phenomenon of rock burst. Rock burst is a typical geologic phenomenon caused by excavation in rock masses. In this phenomenon, because of stress released and explosion in rock masses, they are broken as large and small pieces and are distributed, so that leads to damage of peoples or equipments. Therefore, familiar with this phenomenon and its mechanism of occurrence, is need to analyze this issue. The second part of water supply Karaj-Tehran tunnel with a length of 14 km and about 4.5 m diameter is located in Tehran province. Rock burst analysis has been carried out in the tunnel from kilometer 6 to 9.5 that is critical section because of high overburden (up to 800 m) and presence of faults and crushed zones. In this paper, for predicting rock burst in the critical section of second part of Karaj-Tehran tunnel, four criteria including, Strain energy, Rock brittleness, Seismic energy and Tangential stress criterion are used. Analysis results show that units with high overburden have high possibility of rock burst. 

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The study area is located in Jiroft district, Iran, and is a part of Sahand-Bazman volcanic zone. There are various landslide factors and the importance of each factor are identified qualitatively, based on previous studies and regional specifications. Three landslides were recognized in the study area using direct method (field work) and aerial photographs interpretation. One of these landslides is located in the vicinity of Mohammad Abad of Maskoon Village. The aim of this study is landslide hazard mapping using two integration methods that includes Fuzzy Logic and Hybrid Fuzzy-Weight of Evidence (Hybrid F-W of E). The obtained results of maps from both methods, show a good agreement especially in introducing  high hazard regions. The hybrid method is based on the occurred landslide points and is more rigorous, so hazard regions delineated by this method occupy smaller areas than the areas introduced by fuzzy model. Therefore, hazard maps resulted from Hybrid and Fuzzy methods, can be considered as minimum and maximum limits of landslide hazard in the area, respectively. 

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Evaluation of ground response is one of the most important issues that should be considered in seismic geotechnical engineering field. Alongside the earthquake path associated to regional soil, generally earth movement in places with soft soil is greater than the movement in places with harder soil. This paper is focused to identify local soil condition of Ardekan city which influences on earthquake wave shaking. Therefore after drilling boreholes, implementing geotechnical investigations and down hole geophysical tests, the soil layer characteristics and thicknesses have been obtained. Then shear wave velocity along with soil density have been determined. With using these data it is developed a shaking geotechnical models for different city regions. Finally the ground movement parameters have been determined by   the available data obtained such as density, wave velocity along with using the equivalent linear method employing EERA program. This work was prepared for the return period of 75, 475 and2475 years. It is found that northwest region of city has the most amplification in comparison to other regions.

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In this research, one of the new methods for seismic landslides hazard zonation (CAMEL) to predict the behavior of these types of landslides have been discussed.  It is also tried to eveluate this method with the proposed Mahdavifar method.  For achieving this result, the influence of  Sarein earthquake (1997), have been selected as a case study. In order to apply seismic hazard zonation, the methodology of Computing with Words (CW), an approach using fuzzy logic systems in which words are used in place of numbers for computing and reasoning is employed. First, the required information which includes disturbance distance, ground strength class, moisture content, shake intensity, slope angle, slope height, soil depth, terrain roughness, and vegetation have been collected using air photos, Landsat Satellite images, geological and topographic maps, and site investigation of the studied region. The data is digitized and weighted using Geological Information System (GIS). At the next step, the hazard rate and areal concentrations with respect to landslide types are calculated using CAMEL program and then, landslides hazard map produced by the above mentioned method is compared with landslides occurred as a result of Sarein earthquake. Finally, for evaluating on prediction of the earthquake-induced landslides, empirical comparison have been done between CAMEL and Mahdavifar methods.

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Wave velocity and attenuation are among the most important attributes of stress waves that propagate through geomaterials. Utilizing these attributes, it is possible to acquire useful information about porous geomaterials such as soil and rock and also the fluids that saturate the pores of geomaterials. The key point in order to gain this information is to establish an accurate link between field measurements of wave attributes and physical properties of geomaterials’ skeleton and pore fluid. The pore fluids and their inhomogeneous distribution fluid are among factors that affect wave velocity and attenuation to a considerable extent. Patchy saturation of pores which occurs on the scale larger than grains size but smaller than wavelength is one of the reasons that causes inhomogeneity in pore fluid distribution. The influence of such inhomogeneity is studied in present paper. Two different attenuation mechanisms including relative movement of fluid with respect to solid phase and also attenuation caused by grain to grain contact are implemented to fully assess wave attenuation. It is observed that the former attenuation is more dominant at higher frequencies compared to the latter attenuation.

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One of the major challenges in tunneling is the excavation in regions with high potential of squeezing and in the case of application of full face boring machines evaluation of the required thrust in these regions is inevitable. The Beheshtabad water conveyance tunnel with 65 km in length is considered for transferring one billion cubic meter of water annually to the central part of Iran.  According to geological investigation there is a high potential of squeezing in the 19^th section of tunnel. In this article, the thrust evaluation methods are investigated and the required penetration force is calculated. Then the numerical procedure applicable to thrust evaluation in the 19^th section is discussed and the results are analyzed.  In addition, the required thrust to overcome shield skin frictional resistance using Ramoni's method (2010) is computed and the outputs are compared to numerical ones. As a result of numerical simulation, in order to utilize double shield TBM for the sections of 29030-31600 km and 34900-37490 km, it is required to overcut 3 cm for the favorable geomechanical locations and 10 cm for the unfavorable geomechanical conditions. Decision on the application of full face boring machines in the section of 31600-34900 km could be made providing long term parameters of host rock were determined via performing additional in situ tests in the exploration gallery.  

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Various types of numerical analyses such as   Finite Element Method, Boundary Element Method and Distinct Element Method, are used in rock mechanics and in engineering practices for designing rock structures such as tunnels, underground caverns, slopes, dam foundations and so on. In this paper, the results of back analysis of Koohin tunnel which is located in the first section of Qazvin-Rasht railway have been presented. The main purpose of this paper is to perform the back analysis of the mentioned tunnel with the use of numerical models. For modeling the tunnel, two different sections of 30+150 km and 30+900 km are analyzed with FLAC 2D software.  To perform back analysis the suitable interval of geomechanical parameters according to the tests which were performed on the core drillings has been determined. With the use of direct method in back analysis, the errors of models have been corrected in several steps and finally the geomechanical parameters in 30+150 km station (Elastic Modulus = 0.3 GPa, Cohesion = 0.21 MPa and Internal Angle of Friction = 34^°) and in 30+900 km station (Elastic Modulus = 0.3 GPa, Cohesion = 0.21 MPa and Internal Angle of Friction = 35°) have been achieved. The geomechanical parameters which obtained from back analysis are completely in the chosen interval and compliance with the results of tests which performed on core drillings. On the basis of  geomechanical parameters obtained from back analysis with the parameters which used in the design of the tunnel, the tunnel design and the structure method were confirmed.  

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Marl rocks are from weak rocks which cause some problems due to high swelling and efflorescence capability, low resistance and durability in construction of engineering structures. Creation of these problems is due to inadequate recognition of engineering geology properties of these rocks. Hence, in this research for determination of the physical and mechanical parameters of marl rocks of Safa dam site, Aterberg limits, density, porosity and moisture percent, uniaxial compressive strength (UCS), direct shear, swelling and three axial compressive strength tests and X-ray diffraction (XRD) and X-ray fluorescence (XRF) analyses were performed on available samples from excavated bores. Results of experiments indicate that the type and contents of minerals and percentage of calcium carbonate in marl rocks, especially clay minerals are effective factors on engineering geology properties of these rocks

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Tunneling in complex geological and geotechnical 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 the tunnel. The parameters were calculated using data from Karaj subway-line 2 as a case study. The analytical method used in this study is Leca-Dormiex which is based on limit analysis theory.  The method is based on a translational multiblock failure mechanism.  Also, elastic and Mohr-Coulomb constitutive model have been used for soil behavior. The results of analytical method and numerical modeling were then compared. Based on the obtained results, face pressure assessed from the analytical method of Leca-Dormiex (upper bound) is the minimum pressure that can be implemented on the face tunnel. It also indicates that with implementation of suggested pressure of analytical method, Karaj subway face tunnel is stable and consequently execution of pre-consolidation methods in this section of the tunnel does not seem to be necessary

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River bank erosion is a mechanism initiated by soil particles movement due to subsurface flow. This may occur in a soil texture at a critical hydraulic gradient. With regard to the complexity of river bank erosion processes and limited research in this field, it is of significance to investigate and to identify the effective parameters. In the present study, a physical model of a river bank was developed to achieve in-depth understanding of the effects of bank material particle sizes on porous media under various hydraulic gradients. It is concluded that the length of scour hole caused by seepage erosion may depend on the hydraulic gradients as well as Reynolds number. Further, two empirical relationships are derived on the basis of observed experimental results to estimate scour hole length resulted from river bank erosion for laminar and turbulent conditions

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In the recent years there was a great improvement in the development of underground structures. Due to the increase in the costs of constructions and the importance of the safety in transportation, attention has been focused on the hazards of earthquakes. In this paper, the effect of earthquakes and the importance of seismic analysis are described. The analysis method is presented briefly, and then the simplified analysis of Hashash et al. (2001) is used. Two metro station structures under two different seismic hazardlevels were analyzed. Pushover analysis method is also used which is a simple and static non-linear method in seismic analysis and design of structures.  In this non-linear analysis, the target displacement is computed by the simplified frame analysis model. The finding of this study showed that the structure behavior was remained elastically to a large extent of displacement using this method. Hence, the design of the structures based on the performance level or reduction of the moment extracted from the Hashash et al. (2001) method is recommended.

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Comprehensive laboratory tests were performed to assess fatigue behavior of Alvand monzogranite rock subjected to uniaxial cyclic loading. A series of static loading tests was done to obtain the required data for the fatigue tests. Three maximum load levels (85, 90, 95% uniaxial compressive strength (&sigmac)) at amplitudes 70% were used with 1Hz cyclic loading frequency. The results indicated that maximum stress level significantly influenced fatigue behavior of this rock. It was found that fatigue life decreases in a power function with increasing maximum stress level. Accumulative fatigue damage process shows three stages of behavior including crack initiation phase, uniform velocity phase and acceleration phase. Fatigue damage process were analyzed according to axial and lateral maximum and minimum strain, tangent and second modulus, toughness and hysteresis energy in both loading and unloading conditions. Among these parameters, lateral strain, axial strain and second modulus show the best three-stage fatigue damage behavior. Also, it should be noted that most of the cracks generated in parallel to loading direction and lateral strain are affected by more than axial strain.  

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This paper presented the feasibility of developing and using artificial neural networks (ANNs) for modeling the monotonic large scale triaxial tests over angular, rounded rockfill and materials contained various percentages of fines as a construction material in some dams in Iran. The deviator stress/excess pore water pressure versus axial strain behaviors were firstly simulated by employing the ANNs. Reasonable agreements between the simulation results and the tests results were observed, indicating that the ANN is capable of capturing the behavior of gravely materials. The database used for development of the models comprises a series of 52 rows of pattern of strain-controlled triaxial tests for different conditions. A feed forward model using multi-layer perceptron (MLP), for predicting undrained behavior of gravely soils was developed in MATLAB environment and the optimal ANN architecture (hidden nodes, transfer functions and training) is obtained by a trial-and-error approach in accordance to error indexes and real data. The results indicate that the ANNs models are able to accurately predict the behavior of gravely soil in CU monotonic condition. Then, the ability of ANNs to prediction of the maximum internal friction angle, maximum and residual deviator stresses and the excess pore water pressures at the corresponding strain level were investigated. Meanwhile, the artificial neural network generalization capability was also used to check the effects of items not tested, such as density and percentage smaller of 0.2 mm.

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The Sabzkouh water conveyance tunnel, with a length of approximately 11 Km to transferred 90 million cubic meters of water per year from the Sabzkouh area to Choghakhor Dam, about 80 Km south of Shahrekord in Chahar Mahal-e Bakhtiari province is under study. Because of the long length of this tunnel and also low rate excavation by traditional tunneling methods, the Tunnel Boring Machine has been a priority. Due to limitations of TBMs in complex and unfavorable geological conditions, based on the  precise study performed, the machine was selected. The geological features and the geomechanical properties of rock masses play an important role to selection of proper TBM. In this paper, by estimation of the most important geomechanical properties and geological conditions of the rock masses, with the interpretations of geotechnical logs and the laboratory test results combined with field observations, the rock mass of the Sabzkouh tunnel, based on the three common engineering systems of RMR, Q and GSI was classified. According to classification systems, the rock masses are divided into three geotechnical zones. Based on the uniaxial strength of intact rock, the properties of discontinuities, fault thickness and shear zones, the underground water level and the squeezing intensity the performance of hard rock TBMs was performed. Finally, double shield TBM for the excavation of Sabzkouh tunnel is proposed

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One of the most important issues in the design and implementation of engineering structures is to evaluate and investigate their durability against processes of consecutive wear, wet and dry. The durability of rock is resistance against chemical and physical weathering, the shape, size and status of the initial appearance in a long time and environmental conditions prevailing in the rock, hence it is important to evaluate the durability of rock. Since the device of standard durability (Franklin & Chandra, 1972) designed to evaluate and investigate durability of soft and argillites rocks. So, appears to be essential to design a durability device, which can evaluate hard rocks. For this purpose, Researchers of the Department of Geological Engineering, Tarbiat Modares University, durability device as "large-scale durability device " was designed and built which the length and diameter of the device, is 6 and 4.3 times standard durability device, respectively, and needs 10 samples with weight of 400 to 600 g. In order to investigation the applicability of this device for hard rocks durability, we selected 17 building rocks samples of the igneous, sedimentary, metamorphic and pyroclastic rocks. Then their mineralogical, physical and mechanical properties were investigated. More, experiments of standard and large-scale durability up to 15 cycles were performed and data obtained were analyzed. The results show that, the large-scale durability device than standard durability, have more applicability for evaluating the durability of hard rocks.

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One of the tests that is used for the characterization of soil abrasivity, is LCPC test. LCPC test device is designed for measuring the wear particles as small as pebbles (4-6.3 mm). In this study, some of the most important abrasive minerals were collected from different parts of Iran for analyzing the effect of the geological parameters on the ability of abrasive minerals. Firstly, amount of index minerals abrasivity is measured according to three standards of AFNOR P18-553, AFNOR P18-579 and AFNOR P18-560 that are the preparation of samples for testing, procedure of laboratory tests and analysis of grain size with laboratory sieves. The effect of geological parameters affecting the wear rate of the sample, including five parameters of shape, size, angularity and saturation rate of the environment, has been studied. The effectiveness of these parameters on the abrasivity of samples are studied according to NF ISO 5725 relating to usage of statistics, the accuracy of test method, the repeatability and the ability to reproduce a standard way of testing within laboratory (based on classification index X 06-041). Finally, after ensuring significant effect of these parameters on the abrasivity of minerals by help of SPSS, abrasivity rates for types of minerals that have the hardness below 7 in the Mohs hardness scale, have been predicted.

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The world financial crisis has drastically raised the costs of hydrocarbon materials. This simply manifests the strategic significance of crude oil storage. Regarding the special rank of the oil in Iran’s economy, storage industry development can be one of the solutions to control such a crisis. Underground storage of crude oil in synthetic structures (rock caverns, salt caverns, and obsolete mines) and natural structures (depleted fields of oil and gas, underground water resources, and natural caves) is possible. Among these possibilities more adaptable to the environment is the most appropriate. Due to the existence of many caves in Iran, crude oils storage in natural caves is a proper option. It is clear that if natural caves are used instead of caverns, much can be saved. The present article intends to choose a proper cave for crude oil storage through studying the natural caves based on a combination of fuzzy analytical hierarchy process (FAHP) and technique for order performance by similarity to idea solution (TOPSIS). The likely option is chosen. Roudafshan Cave is considered appropriate for crude oil underground storage based on several qualitative and quantitative criteria including tourism and environment protection regulations, capacity, distance from both main pipes of crude oil transfer and country's major petroleum factories. It should be noted that these criteria are ranked by an experienced team. This cave is located in the north east of Tehran in Firoozkooh and has three passageways which are among the largest ones in the country. Generally, its capacity is estimated to be about 250,000 square meters

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Khorasan Razavi province is one of the areas with many chains of Qanat and Mashhad city in the center of this province has developed on areas with Qanat in the west direction. Loads caused by tall buildings and structures that built on old Qanats can make Qanats unstable and consequently Qanat collapse can lead to ground settlement. This paper deals with identifying the exact locations of Qanat chains by aerial photographs and evaluating the main factors that cause Qanat collapsing. Moreover the stability of Qanat was evaluated in numerical modeling by Plaxis software. The geotechnical data, Qanat depth, Qanat lining system and vertical load was used in modeling and after that, the extension of plastic zone around the Qanat underground tunnel was analyzed. The results of this research show that the rate of plastic zone extension and the influence of lining in Qanat stability decreases by increasing in the Qanat depth. As it is estimated while Qanat depth increases as much as one meter, it can tolerate more pressure as much as loads induced by a one-storey building.

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In the present study, landslides occurred during 1997 Sarein, Iran earthquake are discussed and evaluated. In order to meet the objectives, the Computing with Words (CW), an approach using fuzzy logic systems in which words are used in place of numbers for computing and reasoning is applied. Firstly, the necessary information which include disturbance distance, ground class, moisture, shaking intensity, slope angle, slope height, soil depth, terrain roughness, and land-use have been collected using air photos, LANDSAT satellite images, geological and topographic maps, and site investigation of the studied region. The data is digitized and weighted using ARCGIS software. At the next step, the hazard rate and predicted areal concentrations of landslides with respect to their types are calculated using CAMEL software (Miles & Keefer, 2007). CAMEL provides an integrated framework for modeling all types of earthquake-induced landslides using geographical information system(GIS). Finally, landslides hazard map is compared to landslides triggered by Sarein earthquake.

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Subsurface dams is accordant with nature structure which is useful for water resources management, especially for preventing unused underground water. Regarding to reservoir alluvium, geological and geotechnical characteristics of this type of dam is important. Therefore, in present study, characteristics of the underground reservoir alluvium in Mastbandy area (South of Ardestan-North East of Isfahan) has been investigated. In this regard physical and mechanical properties of reservoir alluvium has been determined, using in situ and laboratory tests. Test results show that the type of alluvium is mostly non uniform dense granular soils without plasticity. Also its permeability is medium to high. Due to the porosity obtained from tests and the depth of the reservoir sediments (5 to 12 meters), in the case of subsurface dam construction, its volume would be about 200000 cubic meters. In general, due to full and empty of reservoir, loading and unloading cause the settlement. Since almost reservoir sediment are gravel and sand, the settlement is mainly immediate settlement. Due to obtained mechanical parameters, the amout of immediate settlement is equal to 16 milimeter