JOURNAL OF ENGINEERING GEOLOGY
Year:2016 | Volume:10 | Issue:2 |Papers Count:8

Due to the increasing importance of geomorphologic conditions on the seismic ground response، in this paper the details about the effect of liquefiable soils on seismic ground surface response are discussed. At first، the equivalent linear analysis based on total stress model in the frequency domain are carried out and then the nonlinear analysis based on total stress، effective stress model by the pore water pressure development in time domain are done in order to evaluate the differences between the several types of ground response analysis methods. DEEPSOIL. V5 software is used based on the latest achievements and various techniques in both solution domains. LNG port project in Assaluyeh، situated in south of Iran، is considered as a case study. Due to lack of the real data recorded near-field fault at the project site، the simulated method is used in order to create the artificial earthquake. Also three far-field earthquakes have been selected based on conventional seismic hazard studies for the seismic ground response analysis. Then، in order to the better understanding of the obtained responses، the resulted responses spectra are compared with the acceleration design spectra provided in the some valid codes. The result of this study indicates that the pulse effect in the horizontal component of acceleration perpendicular to the fault plane direction، affects severely the surface ground response of the near-field earthquake. The obtained results of the nonlinear modeling of the soil with excess pore water pressure build-up in the time-domain are extremely different from those of frequency-domain responses established based on the equivalent linear method. In addition، because of the inherent linearity of equivalent linear analysis which can lead to spurious resonances in ground responses، the peak ground acceleration in the time-domain is lower than the frequency-domain.

Because most part of Iran country is located in a dry climate، construction of water conveyance tunnels is inevitable. One of the major challenges in the building of these tunnels is inflow of water into the tunnel during the construction and operation phase. The Rozieh water conveyance tunnel whose length is 3200 meters is a part of water conveyance project to the Semnan city and it is located 30 Kilometers NE of the Semnan city. In accordance with the drilled boreholes، the tunnel route has been classified into eight zones from a geotechnical view. Then the permeability coefficients of host rock were calculated using back analysis approach done on the basis of numerical simulation results and water inflow quantity during the construction phase. In following، a parametric study was done on the lining and cement injection zone permeability and the thickness of cement injection zone. According to this study، the effect of injection zone thickness variation on the water inflow quantity is negligible. So with the assumption of 3 meters thickness for the injection zone، the permeability coefficient of host rock after injection were evaluated. Dependent on the initial rock permeability، cement injection could reduce the rock permeability 10 to 1000 times. In addition، the water inflow into the tunnel was calculated using hydro-mechanical coupling analysis. According to this analysis، the water inflow calculated by the hydro-mechanical coupling analysis is 50 to 70 percent less than the hydraulic analysis.

With investigation 60 meters from 7 exploratory boreholes Q، RMR، RSR and RQD classification systems calculated and compared Studies show that some categories do not apply marl rocks. Whether or not the marlstone with a quality category limit. There is exponential، linear and logarithmic equations differences between the classification systems in marlstones with what is established other rocks. The result needs marlstone to other engineering rock mass classification systems. RQD classification alone cannot describe the quality Marlstone. As the applied stress due to the behavior of ductile rocks، marlstones are category also hard stones and resistant. RMR classification changes under the normal curve is symmetrical closer and marlstones are classified into two categories Q extremely weak and very weak، and therefore is more suitable than the other classification systems. Key words: Engineering classification of rock masses، marlstones، geological engineering، Doosti dam، Abtalkh formation. Key words: Engineering classification of rock masses، marlstones، geological engineering، Doosti dam، Abtalkh formation.

The aim of conducting this study is to investigate and assess the risks Paverood Dam causes in its constructions stage. After collecting and studying the information related to the environmental conditions of the under-study area and the technical conditions of the dam construction، a list of the possible risk factors were prepared as a questionnaire and it was presented to a group of professionals including elites and the professors teaching majors relevant to environment and dam civil engineering to be evaluated. The number of the questionnaires was determined on the basis of Cochran’ s formula. First the experts group participating in the study was asked to score the questionnaire in order to analyze the obtained questionnaires and the risks present in the area in the framework of the Likert scale. After analyzing the given scores through using the findings of PHA method، TOPSIS method was used to prioritize the identified risks of Paverood. After prioritizing the risk factors، the RAM-D method was used to assess the risks and the effect on Sorkh Abad conservatory with score 9، erosion with a score of 6and working in heights and earthquake taking with a score of 3 were identified as the most crucial risks of Paverood Dam. Environmental management plans are essential in order to decrease the effects of the dam’ s risks it its construction phase therefore the risk decreasing options are suggested at the end for the purposes of dealing with the identified risks.

The Sharbyan River is located in the Sharbyan Village، Sarab، East Azarbaijan province. This river alluvials are supplied from rock units belonging to Oligomiocene and Miocene، including conglomerate، sandy lime، limestone، marl and shale. These deposits are used as raw materials for producing hot asphalt in two asphalt plants that have been built in the vicinity of this river، and the produced asphalt is used mainly in the neighbor provinces that have rather cold climate. Combined analysis of the sediments indicate high level of silica، around 60 percent، for which the prepared asphalt is prone to stripping phenomenon in the cold seasons. During this process، the moisture penetration in aggregates and asphalt mixtures، cause weakening bitumen-asphalt materials bounding and finally asphalt demolition. This study is based on conventional sedimentology methods، different standards of ASTM، AASHTO and Roads and Urban Development Ministry. In this study، the combined effects of hydrated lime (lime filler) and natural filter materials with different proportions was used to deal with the stripping phenomenon، and the parameters of strength، softness، indirect tensile strength have been appraised، as a criteria for evaluating the quality and durability of asphalt due to stripping process. The results show that، the mentioned parameters are affective and improved by these additives in various proportions. Therefore، the produced asphalt will have better quality and durability than previous methods without these additives. The results illustrate، with 3% lime، as the maximum ratio، stripping has the best score of 1، and is disappeared with improvement of other parameters.

This paper presents landslide assessment and landslide hazard zonation of the Polroud Dam area. Polroud Dam is one of the large dams that are in construction 29 km south of Roudsar in Gilan Province. Considering to geomorphology and geological conditions of the area، the site is susceptible to landslide hazard. Field survey shows many evidences of the instabilities especially in the slopes overlooking to the dam and the reservoir. The historical record also demonstrates high potential of the region to slope instabilities. A large landslide that occurred in 1996 discern that the frequency of the hazard in the region. Therefore، Identification of the landslide potential hazard is vital before watering of the reservoir. In this study، we investigated landslide hazard in the site and we have prepared landslide hazard zonation map using the main parameters. These parameters including slope percent، slope aspect، lithology، fault، roads، drainage catchment، elevation، vegetation and precipitation amount. Analytic Hierarchical Process (AHP) has been used to prepare and to crossing the maps. The results show that about 26 percent of the slopes are situated in highly hazard zones. It was determined also that lithology and slope aspects play main role in occurring of the landslides in the study area.

Subsurface flow contributes considerably to river flow and plays an important role in river sediment loads. This research has been focused on investigation of soil properties and bankstream slope on seepage erosion. For this purpose، a series of lysimetric experiments were performed for four different bank angles by varying the soil grain sizes. The soil and hydraulic conditions controlling seepage erosion were investigated. The obtained results indicate that Reynolds number in porous medium plays an effective role in depth of scour hole in noncohesive layer. It was also observed that the elapsed time from the beginning of experiments to which the incipient motion of sediment occur decreases with an increase in the soil grain size. In addition results showed that bank slope affects on scour hole length and calculated Reynolds number considerably. formation. By applying non linear regression method، one relation is proposed for predicting bank scour hole length by seepage.

Soil nailing is a prevalent method for temporary or permanent stabilization of excavations which, if it is used for permanent purposes, the seismic study of these structures is important. There are a few physical models, with limited information available, for the study of behavior of soil nailed walls under earthquake loading. Numerical methods may be used for the study of effects of various parameters on the performance of soil nailed walls, and this technique has been used in the current paper. In this research, the effects of various parameters such as the spacing, configuration, and lengths of nails, and the height of wall on seismic displacement of soil nailed walls under the various earthquake excitations were studied. To investigate the effects of the configuration and the lengths of nails on the performance of these structures, two configurations of uniform and variable lengths of nails have been used. To study the effects of the spacing between nails and the height of the wall the spacings of 2 and 1. 5 meters and the heights of 14, 20, and 26 meters have been considered. The seismic analysis has been carried out using the finite element software Plaxis 2D. To analyze the lengths' of nails, it was assumed that the safety factors of stability of different models are constant, and the limit equilibrium software GeoSlope was used. After specification of the lengths of nails based on constant safety factor of stability, the deformations of the models under several earthquakes records were analyzed, and recommendations were made on minimizing the deformations of soil nailed walls under seismic loading.