ENGINEERING GEOLOGY
Year:2018 | Volume:11 | Issue:1|Papers Count:7

Different methods have been introduced for estimating the performance of tunneling boring machines (TBMs) for each area; therefore, their use in other projects may lead to errors in different geological conditions. Therefore, it is necessary for each project to use models that have similar geological conditions with the project. In this paper, using the actual machine data in the Zagros Water conveyance Tunneling Project, the machine's performance has been predicted by conventional models. Then, the results obtained from the common models including the empirical models of NTNU, Palmestrom (1995) and the theoretical model of CSM compared with the results obtained from Hassnpour et al. (2009, 2011) model, which has been developed based on data from projects with similar geological conditions, and the differences between them are quantitatively explained. The results of this study indicate that the empirical model of Hassanpour et al., due to the compatibility of the database with internal projects, shows the results closer to reality than the other models. Then, empirical models of NTNU and RMi provide more reliable results than CSM model due to consideration of different geological parameters, especially rock masses.

The Dorud-Khorramabad Railway, with a length of 114 km, is under construction in 5 separate phases. In terms of geology, a large part of the route passes along the High Zagros and the Chaghalvandi Thrust in the form of tunnels and other structures. Phase 5, which is 26 kilometers long, from the 72nd kilometer to the 98th kilometer, between the Biran-Shahr Plain and the Deh-Pir region in North Khorramabad City, has two tunnels with a length of more than 7, 500 meters. Given the local climate and the ground water level (average depth of 10 meters) on this route, for the sealing of the tunnels, it is necessary to study the rock mass. For this purpose, it is necessary to understand the characteristics of Pliocene Conglomerate including the mechanical and the physical parameters of the tunnel. The present study tries to determine the permeability by means of the data of water pressure tests. The groutability in this rock unit, in turn, was determined based on the Secondary Permeability Index (SPI). The results show that the behavior of this rock mass is 19% in Class C, 67% in Class B, and 14% in Class A in terms of the SPI, and that 86% of the rock mass needs to improve by means of cement grouting operations. Totally, because of similar geological conditions in the railway route, all of the railway route needs to improve.

Engineering characteristics of different soil mixture are influenced by each of components. In this research the influence of nano bentonite on engineering behavior of nano bentonite-sand mixture (NBS) are investigated. An experimental study involving, compaction test, direct shear and permeability tests was carried out to investigate mechanical behavior and hydraulic conductivity of NBS. different nano bentonite-sand mixtures were prepared. The maximum dry unit weights and corresponding optimum water contents were obtained. According to the results of direct shear test, the highest cohesion (c) and highest internal friction angle (φ ) was selected and the permeability tests were performed in 4 states of compaction, include 90, 100, 110 and 120 % maximum dry unit weight. The results show that permeability decreases by increasing nano bentonite and compaction degree. The lowest permeability is related to sample with 9% nano-bentonite. The cohesion increases by increasing nano bentonite content till 5%, but after that the internal friction angle is increases. The effect of nano-particles is more than compaction on permeability.

The study area of this research is located in the geological zone of Sanandaj, Sirjan. In this area, numerous tectonic movements have caused a lot of faults, crushed zones and numerous fractures in the rock masses. In the Site studies of the 3rd and 4th tunnel sections of ghomroud, subplane studies have been limited and the findings from exploratory boreholes have not led to the identification of subsurface conditions in critical areas. The adverse geological conditions have caused TBM stops and long-delayed delays (about 600 days of complete stop) in the drilling process. Faults zones are main effective causes of the TBM stops. In this study, with a two-dimensional ainversion of resistivity data, , the potential of geophysical studies of the design for the identification of subsurface conditions in the drilling pathway has been investigated. Based on the results of two-dimensional analysis, the distribution of geological layers based on their specific resistance is presented. There are several zones with a very low specific resistance to the tunnel route, which is in accordance with the location of crushed and fault zones, as well as lithological changes in the drilling path. Two-dimensional processing of resistance data provides the possibility of obtaining relevant information on subterranean conditions that could be used in the stage of site studies (Locating of exploration borehole and. . . ) as well as in the implementation of the tunnel.

The proposed classification based on the combination of geological variables and geotechnical parameters provides the possibility of using geological knowledge in estimating the geotechnical parameters. The city of Tehran is one of the metropolises that founded on Quaternary alluvium. The alluvium is divided into four groups, A, B, C, and D, based on age and formation conditions. Some researchers have proposed a new classification using the combination of geological variables and geotechnical parameters for A and C Tehran's alluvia. The aim of this study is to sub-classification of unit B of Tehran alluvia based on combination of geological variables and geotechnical parameters. In this research, based on geological findings in 66 locations of Tehran's alluvia, the geological variables affecting the geotechnical parameters of the coarse-grained B alluvia including grain size, grain form, grain contact, cement between grain, homogeneity and layering were identified and based on these variables, unit B was divided into four units of Bn1, Bn2, Bn3 and Bn4. Using the results of 27 performed direct shear test and 70 plate loading tests in specified units, the geotechnical parameters of these four units, including the internal friction angle, cohesion, and modulus of deformability were determined. With combination of geological variables and geotechnical parameters, new classification of unite B was proposed that make it is possible to estimate the geotechnical parameters based on the geological variables for this alluvium.

The geophysical ground-penetrating radar (GPR) method is able to detect and identify shallow buried targets especially cylindrical type without any destruction of the medium. GPR method is based on sending the electromagnetic waves generally in the range of 1 MHz up to 1 GHz frequency into the earth and receiving reflected off various buried targets. In present research, this method has been used to identify geometrical parameters of buried cylindrical targets containing burial depth and radius. This task was done through the mathematical relationships between geometrical parameters of cylindrical targets with their GPR hyperbolic response using the particle swarm optimization algorithm (PSO). To achieve this goal first, forward modeling of GPR data by 2-D finite-difference time-domain (FDTD) method using GPRMAX was performed for several synthetic models corresponding to common targets in geotechnical applications and subsurface cylindrical installations. Also in the research, several field surveys were carried out over the well-known buried cylindrical targets in Isfahan University of Technology campus, moreover their GPR response was investigated after employing different processing sequences. In order to extract the geometrical parameters of the buried cylindrical targets in synthetic models and real surveys, the PSO algorithm was used in MATLAB environment. The algorithm performance for 7 produced synthetic models, including cylindrical targets made by different materials, radii and burial depth, as well as the real radargrams of GPR profiles in Isfahan University of Technology campus was verified leading to favorite and reasonable results for the synthetic models and real radargrams, respectively.

In this paper, initial microstructure effect of salt rock on its deformation behavior was investigated. Studied samples were taken from Deh Kuyeh salt diapir located at about 27 km NE of Lar city, Fars province. Initial microstructure of two samples from the top of the fountain and one sample from middle part of the diapiric stem were studied by electron backscatter diffraction at Otago University, New Zealand. A slight difference was observed between the initial microstructure of the samples. In the sample from the stem, most grains had been internally deformed, and the grain size is smaller and frequency of low angle boundaries is higher than those in the sample from top of the fountain. The uniaxial compressive strength, elastic modulus and tensile strength values of this sample are lower and its elastic strain, creep strain and creep rate under axial stress of 12 MPa are higher than those in the sample from top of the fountain which can be due to the higher percent of microscopic pores along its grain boundaries. In contrast, the dominant deformation mechanism in the samples from top of the fountain is the grain growth via grain boundary migration. This mechanism removes voids and defects within the grains and along the grain boundaries. Therefore, these samples have higher values of strength and elastic modulus and their grains more easily deformed plastically during mechanical tests.