Journal of Engineering Geology

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The development of large cities requires the use the underground networks for the construction of transportation infrastructures and facilities. Construction of tunnels in soft grounds induces generally soil movement, which could seriously affect the stability and integrity of existing structures. In order to reduce such movements, in particular in urban areas, contractors use more and more the tunnel boring machines (TBM) for the construction of tunnels. Hence in urban environment, Prediction of the ground movements caused by the tunnel excavation is a major engineering challenge. In this paper is used a three-dimensional numerical model and ABAQUS cod for the prediction of soil movements induced during tunnel construction in part of the line 3 of Tehran subway using EPB excavation machine. This investigation include most shield tunneling components such as face pressure, the grouting pressure, excavation machine and frictional contact with soil and shield. Observations of the results demonstrate that the maximum surface settlement in this section is 2.5 cm that is 0.5 cm more than the its allowable value. Simultaneously with surface settlements occur horizontal movements within soil mass, which have different forms in two horizontal directions, and with the expansion of depth they increasing.

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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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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.

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Consecutive impacts of pile driver hammer on a precast pile head for pile installation in the ground is called impact pile driving. Nowadays, the widespread use of impact pile driving in pile foundations construction is undeniable; As a result, pile driving is the most common source of construction vibrations among the sources of producing ground vibrations. The ground vibrations during pile driving is the most important factor of limiting the use of this method. Thus, to avoid structural damages, acceptable prediction of ground vibration before any project implementation is necessary. For this purpose, numerical modeling is undoubtedly the most accurate, economical and fastest way; but up to now, correct modeling of pile installation process has been the main problem in numerical modeling of pile driving. This study aims to achieve better match of ground vibrations with field results compared to the previous numerical results in terms of peak particle velocity by modeling impact pile driving operation through ABAQUS finite element software from ground surface to a desired depth without considering previous researchers assumptions and considering the details of practical works.

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./files/site1/files/1Extended_Abstract.pdfExtended Abstract
(Paper pages1-28)
Introduction
The earthquake is one of the most devastating natural disasters that always threats human societies in terms of health and financial issues. Iran is one of the most seismic prone countries of the world due to locating on Alpine- Himalayan Orogenic belt. On the other hand, growing population and increased construction of tall buildings, increases the damages caused by large earthquakes, especially in large cities. Karaj is one of the most populous cities in Iran which there has been considerable industrial and economic development in recent years. When an earthquake occurs, seismic waves radiate away from source and travel rapidly through the earth crust. When these waves reach the ground surface, they produce shaking that may last from several seconds to a few minutes. During earthquakes, different alluviums with different structures show various reactions. It is well-accepted that, besides the earthquake magnitude and fault distance, local geologic conditions, known as site effects, can also exert significant influences on characteristics of the seismic waves such as amplitude, frequency content and duration of strong ground motion at a given location. The seismic ground motion at any site is influenced by the type of soil in that region. Younger and softer soils usually amplify ground motion more than older soils or bedrocks .
There are theoretical and experimental methods to evaluate the site response. In the present study, the Nakamura's H/V spectral ratio method has been used to evaluate the resonance frequency in 37 locations at Karaj site. In addition, a preliminary 1-D site response modelling has been conducted using Deepsoil program according to downhole, array and geology data. Site frequencies obtained from modelling are presented and compared with site frequencies obtained through microtremor measurements.
Materials and Methods
Single station microtremor measurements at the Karaj site were carried out by the International Institute of Earthquake Engineering and Seismology (IIEES) in 2012 with a three-component broadband seismometer (Guralp CMG-6TD). In the present study, we have used 37 microtremor data along the north-southwest profile because at this profile, geological section was available and these stations contained geotechnical boreholes data. Dynamic range of sensor changes between 0.033 -50 Hz and has a natural period of 1 second. 24-bit analog-to-digital (A/D) converter digitized the recorded data. The recording system was operated continuously for about 30 minutes with sampling frequency of 100 Hz. The use of ambient vibrations for analysis of the local site effects has been studied in detail in the framework of the European research project SESAME (Site Effects Assessment Using Ambient Excitations). The recommended guidelines on the H/V spectral ratio technique are the result of the comprehensive and detailed analysis performed by the SESAME participants during three years of investigations (2001-2004).
H/V spectral ratio was carried out by the Geopsy software. The process starts by converting data from binary format to ASCII format. After DC offset removal, eighth order Butterworth band pass filter used within the range of 0.1 Hz to 50 Hz. The Anti-triggering algorithm STA/LTA has been selected to reject energetic transients from ambient vibration recordings, so STA and LTA were considered respectively 1 and 30 second. Minimum and maximum STA/LTA thresholds were selected between 0.2 and 2.5. For each station, the time-series of the record is divided into windows of 40 to 100 seconds in three components with an overlap of 50%. Also, a cosine taper with the length of 5% of the total window length was used at each end.
The amplitude spectra of each selected window is computed with a fast Fourier transform (FFT) and smoothed using the Konno-Ohmachi function (Bandwidth=40). Then, two horizontal components are merged by squared average. Finally, the H/V spectral ratio of Nakamura is applied for each individual window, and the final predominant frequency is obtained by averaging the H/V spectral ratio of all window. The presence of clear peak on H/V spectral ratio curve is indicative of the impedance contrast between the uppermost surface soil and the underlying hard rock, where large peak values are generally associated with sharp velocity contrasts, and is likely to amplify the ground motion. The H/V spectral ratio in some stations shows a clear peak and at the others might show two or multiple peaks which represents the geologically complex areas. Calculated dominant frequency changes between 0.4 and 2 Hz. These low values indicate the existence of basement at greater depths and large thickness of sediments on basement (Parolai et al., 2002).
Site modelling
The results of H/V spectral ratio are affected by the local geologic structure. Based on this assumption, we can produce theoretical H/V curve with knowledge of the geologic structure in the area. One-dimensional modelling is a suitable method to evaluation of the site response due to the local geology which requires geotechnical and geophysical data. In the one-dimensional modelling, it is assumed that all boundaries are horizontal in the infinite media and the response of a soil deposit is predominantly caused by SH-wave propagating vertically from the underlying bedrock. In this present study, one-dimensional modelling was carried out using Deepsoil software. Due to the very small deformations in soils by microtremor and producing a low levels of strain, we applied the linear method to evaluate the ground seismic response during mild earthquake shakes. In this software, homogeneous and isotropic soil profile is considered as N horizontal layers. The site response (transfer function) is evaluated by parameters such as layer thickness (m), density (ρ), shear modulus (G), and damping factor of layers (β), which are obtained from available geotechnical boreholes.
Usually, engineering bedrock is considered for the purpose of numerical modelling. According to TC4 (1994), the seismic bedrock was defined as a layer with a shear wave velocity of more than 600 m/s. Shima (1978) recommended that the upper crust with a shear wave velocity of about 3000 m/s, is adopted as bedrock when large scale structures with longer vibration period are being considered. International building code (ICC2000) has defined the seismic bedrock by a shear wave velocity of more than 760 m/s. According to Unified Building Code (UBC97), bedrock is defined into two groups: A (very hard rock with a speed of more than 1500 m/s) and B (rock with a speed of 760 to 1500 m/s). Therefore, the proposed values of the shear wave velocity are different for considering seismic bedrock. In order to consider the uncertainty of the shear wave velocity in the present one-dimensional modelling, three scenarios for the bedrock, were performed with three speeds of 760 m/s (based on engineering bedrock), 1300 m/s (bedrock geology), and 2500 m/s (corresponding to tuff-andesite of the Karaj basement) at different depths, according to the regional geological map. Then, three scenarios of the numerical modelling were compared with microtremor transfer function.
1. One-dimensional modelling at the Karaj site using downhole data for engineering bedrock (> 760 m/s)
In order to access the shear wave velocity profile for 1-D modelling, downhole data from 21 boreholes were used in nine sites which were available up to the maximum depth of 50 meters at 20 boreholes and 96 meters at A09 borehole. Low thickness of alluvium (about 17-85 meters) was considered with engineering bedrock (>760 m/s) for numerical modelling. The results represent higher frequency range compared with the microtremor data. In some previous studies where engineering bedrock had been defined by shear wave velocity values between 700 to 800 m/s in 1-D modelling, the results of the theoretical model is incompatible with experimental results. Thus, it seems that it is not suitable to consider the engineering bedrock in 1-D modelling.
2. One-dimensional modelling at Karaj site using microtremor array data for geology bedrock (> 1300 m/s)
By considering the seismic bedrock (>760 m/s) at depths of 17 to 85 meters and calculating the one-dimensional transfer function, the peaks in higher frequency compared with the experimental method is observed. According to reliability of experimental H/V results which has been proved by researchers around the world (Haghshenas et al., 2008), the difference between the transfer function results in experimental and theoretical methods indicates that two variables of shear wave velocity or depth of bedrock and alluvium thickness have not been properly modeled. It seems that in order to get better results, it’s necessary to analysis by considering the geology bedrock at greater depth. Tchalenko, et al., (1974) considered lower part of Plio-Quaternary sediments of Hezardareh Formation and Miocene marl-limestone of Upper Red Formation as the bedrock in the Karaj plain. Shafiee and Azadi (2006) computed shear wave velocity characteristics of these geological units throughout Tehran city. Therefore, a mean velocity of 1300 m/s was considered for the geology bedrock during the modelling.
In order to access the shear wave velocity profiles at greater depths, microtremor array stations were designed by seven seismometer with 100 m radius at A09 (site 8) borehole. As it can bee seen, a clear contrast at a depth of about 230 m is observed. Therefore, the modelling was carried out by taking 230 m alluvial thickness on geology bedrock according to lithology of the region. The result of this modelling has shown a peak at frequency range of 0.87 Hz that is compatible with the microtremor peaks at this site. In other site this modelling was performed using array and downhole data. The results indicated that the first effective contrast occurs at depth of 200 to 300 meters.
3. One-dimensional modelling at the Karaj site for basement (> 2500 m/s)
Transfer functions obtained from the previous model, did not cover low frequency peaks in the experimental methods. Therefore, the presence of other low-frequency peaks is either due to the geometry of the sedimentary basin or deep contrast. It seems that due to the geology of the region, tuff- andesite of the Karaj Formation as basement plays an important role in the creation of low-frequency peaks. Therefore, to obtain a better model, deep contrast was considered about 2 kilometers due to differences in the type of bedrock with a shear wave velocity of 2500 m/s. For this purpose, according to the properties of the Upper Red Formation, an average constant speed of 1400 (m/s) was considered in modelling and by changing the thickness of this layer, the modelling was continued in a trial and error manner until the numerical model is consistent with microtremor peaks. The modelling results in nine site indicate that there is basement at the depth of 2000 to 2250 meters.
Two-dimensional model of the Karaj site
Using the one-dimensional analysis and evaluation of the geological map of the area, two dimensional geological structure was rebuilt in studied profiles. Green and gray tuffs and igneous rocks of Karaj Formation outcrops in north of Karaj and constitute the Alborz Mountains. This Mountains eroded by the action of rivers and were deposited in the form of large alluvial fans. Coarse sandy sediments were deposited near mountains wherein energies of rivers and streams were extremely high (site 1 to 4). Furthermore, fine-grained sediments were deposited at far distances by decreasing in the energy of streams (site 5 to 9). Berberian et al (1985) divided B Formation in two parts: heterogeneous deposits of sand, gravel, rock and clay in north of Tehran (Q_bn) and silts and clays of Kahrizak (Q_bs) in south of Tehran. According to 1-D modelling, thickness of this layer is about 200 to 300 m which has been deposited on geology bedrock. As mentioned before, lower parts of Hezardareh Formation at the north of Karaj and Upper red Formation in the south west of Karaj are considered as geology bedrock. Upper Red Formation was deposited with unconformity on tuff-andesite of the Karaj basement at depths of 2000 to 2250 meters.
Conclusions
The use of empirical methods based on microtremor is an efficient way to estimate the site effects in Karaj city, although the use of earthquake records could provide better evidence of the depth and geometry of basement. One-dimensional modelling of shear wave velocity profiles obtained from downhole data and considering the engineering bedrock (> 760 m/s) at depths of 17 to 85 meters, is not a good way to estimate the dominant frequency of alluvium. By considering the greater depth of alluvium and using shear wave velocity profiles obtained from microtremor array, 1-D modelling was carried out for geology bedrock (1300 m/s). Therefore, peak frequency in transfer function at the range of 0.87 Hz has been associated with effective contrast at depths of 200 to 300 meters. It seems that Karaj basement (> 2500 m/s) with about 2 kilometers depth plays an important role in the production of low-frequency peaks in transfer function.
 

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./files/site1/files/5.pdfExtended Abstract
(Paper pages 247-276)
Intro

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 Introduction
Recently, several studies on buried pipelines have been conducted to determine their uplift behavior as a function of burial depth, type of soil, and degree of compaction, using mathematical, numerical and experimental modeling.
One of the geosynthetics applications is the construction of a reinforced soil foundation to increase the bearing capacity of shallow spread footings. Recently, a new reinforcement element to improve the bearing capacity of soils has been introduced and numerically studied by Hatef et al.  The main idea behind the new system is adding anchors to ordinary geogrid. This system has been named as Grid-Anchor (it is not a trade name yet). In this system, a foundation that is supported by the soil reinforced with Grid-Anchor is used; the anchors are made from 10×10×10 mm cubic elements. The obtained results indicate that the Grid-Anchor system of reinforcing can increase the bearing capacity 2.74 times greater than that for ordinary geogrid and 4.43 times greater than for non-reinforced sand...../files/site1/files/0Extended_Abstract6.pdf
 

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Extended Abstract
Introduction
Dimension stones market is considered as an important and profitable sector of mineral deposit business due to their share in national economic performance. There exist a number of technical reports highlighting a lack of rock quality control in the sequence of quarrying and dimension stones production procedures, which has lowered the production efficiency and consequently the profitability of this strategic mineral industry in Iran. The quality of dimension stones depends on several factors which fractures, joints, voids and fine beddings are the most important factors that down-grade the quality. Therefore, foremost the quality and desirability of the building stone must be precisely determined by sampling, compressive strength testing and preparing microscopic sections. All of the mentioned evaluation methods are destructive. Moreover, sampling and performing multiple tests on all parts of a quarry or on all quarried stone blocks, is not possible. Detection of fractures hidden into the dimension stone blocks is achievable using fast, low-cost, accurate and non-destructive ground-penetrating radar (GPR) method. GPR is a high-resolution geophysical method which uses electromagnetic waves with high-frequency in order to map structures and detect buried objects in subsurface without coring or any destruction of the medium.
 
 
Materials and methods
In current research, GPR method has been applied to evaluate the quality of quarried travertine blocks at Haji-Abad quarry complex in Mahallat district, Markazi province, before starting any processing operation. To achieve this goal, the 2-D GPR responses of synthetic models resembling cubic dimension stone blocks containing fine layering and discontinuities, were primarily simulated using a modified 2-D finite-difference forward modeling program in the frequency-domain coded in MATLAB. Among the variety of available numerical methods, the finite-difference time-domain (FDTD) method has paid more attention due to having the simple understanding of the concepts, flexibility, simulation and modeling of complex environments and the acceptability of its responses in the applied cases. In this research, the simulation has been implemented for both calcareous and dolomitic rocks (including travertine and marbles) and granites. In the study area, the GPR data acquisition was carried out using a GPR system equipped with shielded 250 MHz central frequency antenna, 0.5 m antenna distance and 2 cm sampling intervals by monostatic common-offset reflection profiling method. In order to process, analyze and interpretation of data, Ground Vision and Radexplorer software were employed. The most important pre-processing and processing operations applied to the data to provide the final sections, comprising time-zero correction, dewowing (removing very low frequency components from the data), DC shift removal, Butterworth filtering, running average, background removal and types of amplitude gain.
Results and Conclusion
The results of the forward modeling show that the GPR response of fine beddings interfaces and major discontinuities hidden in the volume of dimension stone blocks are clearly detectable. Interpretation of the actual radargrams taken from a real GPR case study (Haji-Abad quarry complex) after employing various B-scan pre-processing and filtering procedures, indicates that GPR method is highly capable to detect fine beddings and discontinuities in order to evaluate the quality of dimension stone before starting any quarrying process. Validation of the obtained results of the present research was carried out on one of the blocks with a predicted large oblique joint while the existence of the large joint was proven under the cutting saw in the stone processing plant. However, it should be noted that due to the existence of inherent heterogeneity encompassing fine beddings, in addition to noises from different sources and their associated multiple reflections in real radargrams, the response of shallow major discontinuities may mask the response of minor ones located underneath or deeper, so as a result may not be detectable with routing GPR radargrams../files/site1/files/121/Ahmadi_Abstract.pdf
 
Keywords: Dimension stone Blocks (cubes); dimension stones production; Ground Penetrating Radar (GPR); Forward modeling; Quality control; Haji-Abad mining complex in Mahallat
 

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Introduction
     Ground-penetrating radar (GPR) method is a pretty new, non-destructive and high-resolution geophysical method that is widely used to identify the thickness of snow and ice layers and glaciers bed, because snow and ice are transparent for electromagnetic (EM) waves. Therefore, this method has been used to determine the thickness and basement topography of Alam-kooh glacier. In this research, only the GPR acquired data using unshielded antenna with central frequency of 25 MHz along one line in Alam-kuh glacier, Kelardasht- Mazandaran, have been processed and interpreted. The GPR data acquisition has been done by using common offset method, and transmitter-receiver separation of 6 meters. The final real radargram related to one of the surveyed GPR profiles in this region has been prepared after applying various processing operations containing signal saturation correction, amplitude gain, f-k migration filtering and static (topography) correction on the raw data. After applying processing sequences on the acquired data, the EM waves reflection off the interfaces of different layers including the reflections from the glacier basement have been detected, and by assigning a suitable EM wave velocity in the ice (0.16 m/ns), the thickness of 50 m for the ice layer laid under the survey line has been estimated. Also, in present research, forward and inverse modeling of GPR data have been performed to employ for snow, ice and glaciological investigations in the AlamKooh region of Mazandaran. To achieve this goal, GPR response of synthetic model corresponding to the real radargram was simulated first, by 2-D finite-difference time domain (FDTD) method. Afterward the inversion method by solving an optimization problem was employed to validate the interpretation of real GPR data.
Methodology and Approaches
     Based on the nature, physical and geometric properties of the subsurface target in the field data, their synthetic model have been built and their two-dimensional GPR responses forward modeling using ReflexW software and finite difference algorithms improved in the frequency domain, have been obtained. Also, it has been used an effective algorithm, coded in GUI environment of MATLAB programming software and as a result, a reliable and accurate inverse modeling has been carried out. In the present study, to simulate the behavior of the propagation of EM waves in GPR method, two-dimensional finite difference method has been used. The main advantage of this method is its comparative simplicity of the concept, high accuracy and simple implementation for complex and arbitrary models as well as easily adjusting the antenna when applied. In this study, acquisition of GPR field data and synthetic data modeling have been carried out in TM mode. The radargrams of the GPR data have been demonstrated using ReflexW software after performing necessary processing sequences.
Results and Conclusions
     The obtained results reveal that moraine materials covering the surface of the area are mainly fine-grained granite. The bed-rock or basement in the area is also granite. The polarity representing ice-bed rock is clearly seen on the GPR profiles. The topography of the glacier basement has successfully been detectable using just by GPR method. The electrical resistive nature of the glacier has caused large penetration depth of GPR pulses in this research. Furthermore, the results of the research for presented profiles on the basis of forward and inverse modeling output of GPR data in comparison with real GPR radargrams in the region validated the accuracy of GPR investigations in the area. Although with a quick glance, the error obtained by the inverse modeling for real GPR data seems unexpected and unacceptable, absolutely the high rate of error depends on many factors influencing on the real earth models containing various limitations existing in all forward modeling algorithms and software packages, impossibility of making forward modeling exactly according to the real models (due to the complex nature of the ground), taking into account the homogeneity and uniform host environment and targets in the modeling process unlike the diversity, the presence of different types of noises and so on. Therefore, making a controlled geophysical test site and trying performance of inverse modeling algorithm for field GPR data in this site, as well as determining the important physical parameters such as dielectric permittivity and electrical conductivity by experimental method through sampling from different depths for complex geological environments are suggested../files/site1/files/124/1ahmadpur%DA%86%DA%A9%DB%8C%D8%AF%D9%87.pdf

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In the mechanized boring method, the factors affecting ground surface settlement can be mainly divided into five categories: geometric, geomechanic, boring machines working, operating and management parameters. In urban tunnels bored mainly in shallow soil bed, face pressure can be one of the factors preventing ground settlement. The Line A tunnel in Qom metro project is bored with an EPB (Earth Balance Pressure) mechanized boring machine. The effect of face pressure on ground surface settlement was analyzed in the present study according to five sections of the tunnel. These five sections were selected in different kilometers of the tunnel where settlement gauges were installed and the results could be validated. To investigate the effect of face pressure on maximum ground surface settlement, four pressure levels of 100 kPa, 150 kPa, 200 kPa, and 400 kPa were taken into consideration. These were 1, 1.5, 2, and 4 times of the initial face pressure level, respectively. The ground surface settlement was assessed at four pressure levels using the finite element software, PLAXIS 3D TUNNEL. The results were validated using ground-level instrumentation (settlement gauges) on all sections. The validation showed that the modeling results are in good agreement with the results obtained from settlement gauges.  Comparison of the results indicated that a 4-fold increase in the face pressure led to a maximum decrease of 4.45 mm in the maximum settlement. Therefore, an increase in the face pressure can reduce settlement, although quite minimally. It was also found that an over-increased face pressure (face pressure over 200kPa) not only did not reduce the maximum ground surface settlement but also may lead to passive failure or uplift of ground surface ahead of the shield. 
 

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Introduction
Ground-penetrating radar (GPR) is a high-resolution geophysical method which uses electromagnetic waves with high-frequency in order to map structures and objects buried in subsurface without any destruction of the medium. In present research, choice of optimum parameters of real data acquisition for this method has been studied. The governed behavior on the GPR fields can be simulated by solving the Maxwell’s equations and the appropriate boundary conditions that form the basis of electromagnetic theory. Among the variety of available numerical methods, the finite-difference time-domain (FDTD) method has paid more attention due to having the simple understanding of the concepts, flexibility, simulation and modeling of complex environments and the acceptability of its responses in the applied cases. The purpose of this study is to identify what reasonable information can be obtained from field data under different environmental conditions and different survey parameters.
 
Materials and methods
To achieve the goal, first forward modeling of GPR data has been carried out for several synthetic models corresponding to common targets in subsurface installations, using 2-D finite-difference time-domain method by means of GPRMAX, ReflexW and Radexplorer softwares. The main purpose of the simulations is investigation of the effect of survey parameters such as spatial sampling intervals (trace interspacing) and temporal sampling frequency on the GPR response of targets with various physical and geometrical parameters. Also to select and design the most appropriate conditions and survey parameters for real GPR data, numerous field traverses were performed in Isfahan University of Technology campus over the pre-known buried cylindrical targets containing power cable, petro-gas pipe, water pipeline and waste water pipeline with diverse host media. In this operation due to having one monostatic GPR system equipped by shielded antenna with central frequency of 250 MHz, some of the survey parameters containing central frequency, antenna separation and antenna directivity are invariant. The most important investigated survey parameters are temporal sampling frequency, spatial sampling distance (trace intervals), time window and number of stacked traces.
 
Results and discussion
Regarding carried out investigations through field data acquisition, in only one case the GPR system failed to detect any understated targets which this mode is related to choice a sampling distance of 1 cm and a sampling frequency of 504 MHz. The sampling frequency of 504 MHz is just capable to detect the surface water pipeline (due to its low burial depth). Also only in three cases the GPR system is capable to detect all subsurface targets so that the first mode of the trace interval is 2 cm and the sampling frequency is 1954 MHz, whereas in the latter two, the trace interval is 1 cm and the sampling frequencies have been selected 1563 and 1954 MHz. At the end success or failure of the targets detection was investigated on the basis of selected survey parameters and the probability of successful target detection was determined depending on the temporal and spatial sampling frequency so that the maximum probability of target detection is regarding to temporal sampling frequency of 1954 MHz and trace interval of 1 cm. Regarding GPR field data acquisition, considering the relations between the central frequency of GPR measurement systems, the depth of penetration and resolution, the diversity of materials and various components of the host media of targets and their surface overburdens a range of dierse equipments with a variety of frequencies is needed, which all of them are not generally available.
 
Conclusion
As a general conclusion of this study, in order to reduce the risk in GPR data acquisition operation, optimal survey parameters are suggested as follows:
The sampling frequency should be about 7 to 8 times the central frequency of the employed system (should not be less than this value in order to avoid aliasing and on the other hand, due to reduction in the amount of data and thus the memory needed for storage and processing), trace interspacing equal to 1 cm (in order to detect all buried targets especially targets with small size), the number of stacked traces equal to 16 (to reduce the amount of computer memory required for processing and storing data) and time window according to the computational-empirical relation (1).
                                                                                                                                                                (1)
Where W is time window, D is the maximum depth and V is the minimum velocity.
The results of this research are not restricted to the investigated case, but in practice are applicable for cases with similar host environments, especially in urban areas (which application of non-destructive methods such as GPR is necessary)../files/site1/files/131/6Extended_Abstract(1).pdf

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Introduction
Unsystematic execution of blasting process may result in serious damages. Blasting is a very complex process and almost all of blast designs are made based on empirical relations resulting from trial and error. In recent decades, considerable development of numerical methods has been made possible to achieve high accuracy study of blast effects on surface and subsurface structures. Among these methods are boundary element method, finite difference method and finite element method. It should be mentioned that there is currently no software which might be able to completely simulate blast process. But the UDEC software is able to simulate different aspects of this phenomenon through simplification and focusing on each aspect.  Therefore, the UDEC software was selected. In the present study, the modeling  has been performed for Ghareh Changool ramp of Zehabad Zinc and Lead Mine against blast loads.
Material and methods
Zehabad Ore deposit is located around 2 km south of  Zehabad Village of Tarom Sofla County, 56 km to northwest of Qazvin at 49˚ 25' east longitude and 36˚ 28' north latitude.
The formation surrounding the ore deposit is generally made up of pyroclastics, lavas and sedimentary rocks of Eocene age (Karaj Formation) which have been divided into 22 stratigraphic units. Lithological composition of the tuff units are often rhyolithic to dacitic and the lava units are consisted of rhyolite, dacite and andesite.
To  accomplish this study, we took rock blocks from Ghareh Changool ramp. Then, the blocks were cored in the laboratory to provide cylindrical samples for doing uniaxial compressive, triaxial, Brazilian and direct shear tests. Physical and mechanical properties of the tuff samples were determined according to ISRM standards. 
In the present study, field studies were done to calculate strength parameters and properties of the joints.  Based on these studies, three major joint sets were determined. In order to obtain the shear strength parameters of the joints, the cylindrical samples of andesitic tuff were molded by concrete and direct shear test was done on all of the joints according to ASTM D 4554.
Results and discussion
To simulate the complex conditions of blast process, we used the discrete element software of UDEC for numerical modeling considering the discontinuity of the medium. To do a dynamic analysis, first the model should come to equilibrium in the static state. The space considered to be modeled in the study was a horse-shoe-shaped ramp with 4 m base, 4 m height and 1.5 m arc radius which was located in rocky medium consisting of tuff.  The height of overburden above the roof of the ramp was about 190 m. The dimensions of the model in UDEC was 20*20 m². The behavioral model considered for the rock blocks and discontinuities were the elastic isotropic and surface contact of the joint (elasto-plastic) associated with Coulomb sliding failure, respectively. After defining the absorbing boundary conditions, the dynamic loads were applied to the model based on the defined time period. In mines stability and blasting process, the dynamic load resulting from the blast is often applied to a model as a pulse. By application of dynamic load and considering the other mentioned variations with respect of static analysis, the dynamic response of underground space could be estimated under vibration load of blast or earthquake. To do this, the blast impact wave was applied to the left side of the model as exponential pulse with maximum pressure of 4.41 MPa and time width of 0.7 to 7 msec. The results of the numerical modeling in static analysis indicated that no block would fall (Fig. 1). After application of the blast load, the results showed that there was no falling around the ramp (Fig. 2).
Conclusion
1. In static condition, after initial equilibrium no block was fallen into the ramp, regarding the blocks’ magnification plots, as a result the ramp was stable in the static loading.
2. In dynamic loading case, considering the displacement plots  around the ramp and the low values of these displacements, as well as, magnification plot of  the blocks 40 msec after the blast it can be said that no block was fallen into the ramp. Therefore the ramp was stable in the dynamic loading case and there was no need to install support system. ./files/site1/files/133/1Extended_Abstracts.pdf

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In recent years, with the growing use of the nailing method for stabilizing excavation walls, there has been a need for a comprehensive investigation of the behavior of this method. In the  previous studies, the behavior of nailed walls has been investigated in static and dynamic states and under different conditions. However, due to the different feature of near-field ground motions, it is  necessary to study the effect of these motions on the behavior of the nailed walls. Near-fault ground motion is significantly affected by the earthquake record direction and the rupture mechanism. So, in this study, to compare the effects of near-field and far-field ground motions, a two-dimensional (2D) soil- nailed wall was considered. PLAXIS 2D was used for the modeling of the soil-nailed wall system. An excavation with a dimension of 10 meters in height was taken into the account. In this study, 10 records (Five fault-normal near-field ground motion records and five far-field ground motion records), were recorded  on the rock and  applied to the model. These ground motion records were derived from the near-fault ground motion record set used by Baker. These records were scaled to the Peak Ground Acceleration (PGA) of 0.35g and then applied to the bottom of the finite element models. Mohr-Coulomb model was then used to describe the soil behavior, and Elasto-plastic model was employed for the nails. A damping ratio of 0.05 was considered at the fundamental periods of the soil layer. The results showed that the  generated values of bending moment, shear force and axial force in nails under the effect of the near-fault ground motions were  more than those in the far-ault ground motions. These values were  almost equal to 23% for the maximum bending moment, 30% for the  shear force,  and 22% for the axial force. The created displacement under the effect of near-fault ground motions was  more than that in the far-fault since a higher energy was  applied to the model in the near-field ground motions during a short time (pulse-like ground motions). In contrast, in the far-fault ground motions, due to the more uniform distribution of energy during the record, such pulse-like displacements were not observed in the system response. Increasing in nail length and soil densification, decreases the displacement of the soil-nailed wall but does not change the general behavior of the soil under the effect of near-field ground motions. Based on the obtained results, for a constant PGA, there were  positive correlations between the values of the  maximum displacement on the top of the wall and  the PGV values of near-fault ground motion records. However, the mentioned correlations were  not observed in the case of far-fault ground motions.

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In Yazd Darreh-Zereshk copper deposit geophysical data containing magnetic, resistivity and induced polarization have been surveyed and 25 boreholes have been drilled in the area. In the present research, inversion and processing of geophysical data as well as their qualitative and quantitative accordance with boreholes assay data have been carried out. To achieve the goal first, total magnetic intensity map after applying necessary filters and processing, was mapped to identify surface and deep expansion of anomalies on it. Drawing the anomaly profile of magnetic stations surveyed along 4 geoelectric profiles shows that most of the magnetic anomaly zones have high chargeability and low resistivity that indicates the qualitative compatibility of magnetic and geoelectric data, as a result increasing the probability of mineralization in the area. Afterward  on the basis of qualitative interpretation of geoelectrical sections, optimal locations of drilling on the each profile were proposed. Plotting mineral deposit cross-section along the geoelectrical profiles using the boreholes assay data, revealed that drilling of some boreholes located on the geophysical profiles haven’t been based on the results of geophysical operation, carried out without any right logic, purpose and design. In general, the qualitative accordance of the results of geoelectrical operation with the boreholes assay data showed a pretty good qualitative accordance. Also investigation of linear correlation coefficient value between inverted geophysical data and borehole assay in a specific same range after a same definite gridding and interpolation of their values, overall indicated a relatively good quantitative accordance (between 0.4 and 0.7)../files/site1/files/151/1.pdf

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Chahar-Gonbad region of Kerman province is geologically located in the southern part of central Iran zone, dominantly in Uromieh-Dokhtar volcanic belt. In this region, many high potential prospects, specially Cu-Au mineralization, have been detected during large scale exploration and reconnaissance phases. In this paper, remote sensing and field geophysics were used for alteration mapping on the surface and ore body delineation on the subsurface, respectively. To this end, we used an ASTER satellite image and different maps were generated by spectral technics such as false color composites and spectral ratios. Results showed argillic (and phillic) alteration in Bab-Zangoeie area is surrounded by propylitic alteration, which could be a promising evidence for Cu mineralization. Integrating these results with previous exploration studies led to selecting target area selection for ground study and field geophysics. We used both induced polarization (IP) and resistivity (RS) methods as two powerful geoelectrical methods by a pole-dipole array along four profiles. After preprocessing analysis, forward and inverse models were constructed in 2D section and 3D overlay model of joint IP/RS anomalies were constructed. Based on the obtained results, the deposit in depth where we proposed drilling targets. Further drilling operation have proved the mineralization in our proposed targets../files/site1/files/152/%D9%86%D8%B8%D8%B1%DB%8C.pdf
 

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