Journal of Engineering Geology

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A new approach is suggested to determine the permanent deformation of slope under seismic loading based on the horizontal slices method and limit equilibrium analysis. A comparison of the analytical results obtained from the proposed method for 3 sample slopes with those of previous research results is performed. The analytical method presented can be used to calculate yield acceleration, seismic coefficient of horizontal acceleration, permanent deformation and angle of failure wedge for slopes. Also, the stability analysis can be performed by proposed method. It was concluded that the horizontal slices method by analytical procedure proposed reliably calculates the permanent deformation of slopes.

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Desiccation cracking commonly occurring in compacted clayey soils typically used as landfill liners can result in poor hydraulic performance of the liner. In this research, a simplified image processing technique was developed in order to characterize desiccation cracking intensity in compacted clayey soils. Three pairs of compacted clayey soils were studied in a relatively large scale experiment to evaluate the effect of geotextile cover on desiccation cracking under real-time atmospheric conditions. Digital images were taken from the surface of soils at certain time intervals for 10 months and were analyzed to determine crack intensity factor (CIF). The key parameter in identification of cracks as accurately as possible was found to be sensitivity. Calibration process was based on using %20 of the images with different crack intensities whose crack dimensions and therefore CIF values have been already measured to compare to program output. A calibration coefficient for sensitivity was accordingly determined based on the average difference between the sensitivity introduced by the program and the actual sensitivity calculated based on an overlaying process. Result of verification of this methodology indicated that it can be reliably used to determine CIF of compacted clay soils in a simple yet accurate manner.

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Determination of uniaxial compressive strength (UCS) of intact rock is an important mechanical parameter required for many engineering projects. In some engineering projects, for example, well drilling has been accomplished for petroleum. The requirement of deep well to take samples to obtain rock core sample for determination of UCS is a difficult task. On the other hand, determination of this parameter is essential in order to analyze well wall stability and well development program. Therefore, the idea of using drilling cuttings is proposed for determination of UCS. In this paper, in order to develop relationship between UCS and single compressive strength (SCS) 7 block sample of microcrystalline limestone from Asmari formation were used. Then UCS test was performed and uniaxial compressive strength was determined. Next, these samples were crushed and 420 single particles were prepared. Then SCS for each particle was determined. Since the shape of particles affects particle strength, shape of particles was modified.  The total particles used for determination of SCS were spherical. In order to study the effect size of particle, particles with diameters 2, 3 and 4 millimeters were prepared and the SCS for each particle has been determined. With the increase of diameter of particles, the SCS has been increased too. In order to eliminate the effect of size of particles, it is defined variable size and strength and proposed chart between them. Coefficient of correlation between SCS and UCS is more than 0.91 which indicates a high correlation between them.

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In this study using finite element procedure was used to simulate the dynamic behavior of reinforced soil walls, to evaluate their dynamic response on all types of deformation modes, different mechanisms of failure detection and identification of parameters in each of the modes and the mechanisms. Detailed numerical modeling, behavioral models and materials were described and Dynamic response of the physical model has been validated experimentally. Parametric study has been of the wall height of 5 meters by the effective parameters such as hardness, length to height ratio, the vertical reinforcement, wall height, and acceleration inputs. Three modes of deformation were observed. The study showed that occur bulging deformation mode while the use of flexible reinforcement and occur overturning deformation mode while the use of stiffness reinforcement. Stiffness reinforcements have the most effective in changing the type of deformation. Length to height ratio of reinforcements has the minimum effective in changing the type of deformation.

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Today the effects of grouting are usually confirmed by the results of permeability tests but this method is not enough to show the changes in mechanical properties of rock masses. Although many investigators use the in situ tests for evaluation of rock mass mechanical property improvement. But this tests are time consuming and expensive. Grouting reduces the permeability and improves the condition of joints and ultimately increases the rate of rock mass classification in rock engineering. So with measurement of rock mass quality index values (Q-value) in cores obtained from grouted boreholes, the efficiency and success in improving the mechanical properties of rock mass can be showed. This paper for first time introduces Q-logging as a simple method to assess the impact of grouting in improvement of the rock mass quality. Here in, the results of Q-Logging in trial injection panels in the Bakhtiary, Bazoft and Khersan II dams have been examined. The deformation modulus were calculated from the Q-Logging for before and after of grouting. Results show that there is a good agreement between calculated rock mass parameters based on the Q-Logging method and the measured from in-situ test in the studied site. This agreement confirms the efficiency and applicability of the Q- Logging method for assessment of grouting success as well as the estimation of the rock mass parameters in grouted areas. Also it has been shown that the deformation modulus in weak rock mass with low quality has been more improved than rock mass with beater quality.

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Evaluation of strong ground motion up beneath the construction is important in both geotechnical engineering (site effect) and earthquake engineering aspects (analysis of earth behavior). The common methods of microzonation in geotechnical engineering are based on one dimensional dynamic analysis, in which ground surface is assumed to be horizontal. However in many cases, because of variety of topography conditions, recorded responses are different on the top of hills and their corners. In this study, FLAC 2D software, as finite difference software, is used to analysis the trapezoidal hill with different shape ratios. These topography models are analyzed by far field earthquake records, and their dimensionless amplification ratios are compared with the obtained results of one dimensional analysis. Assessment of these two analyses methods in some points on the topography and around it, demonstrated considerable differences that show the necessity of two dimensional analysis in earthquake geotechnical engineering.

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This paper presents a case study of the instability mechanism, to verify and reinforcement method adopted construct collapsed zone of Sabzkuh water conveyance tunnel in southwest Iran. The instability problems were encountered during tunnel excavation due to the failure, changes in stress field lead to deformation causing dilation and increasing the permeability of sand and gravel layers, local fault gouge zones, landslide and in turn significant reduction in shear strength and collapse in tunnel. IPE Arch Support Technique (IAST) was, used for T1 part of Sabzkuh tunnel zone in order to reinforce the ground around tunnel and to cross the zone falling. In this study, Finite Element Method was employed for the quantitative reinforcement effect with deformation modulus of ground, IPE length and size. As a result, the settlement increases as length increases and decreases with the increase of the deformation modulus of ground and IPE size.  

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The main objective of this research is to investigate the mechanism of cement-clay-heavy metal contaminant interaction from micro-structural point of view. To achieve this objective series of batch equilibrium and XRD experiments were performed. The results indicate that the addition of 10% cement not only stabilizes the soil, but also at 250 cmol/kg-soil of heavy metals causes 130% increase in heavy metal retention. Furthermore, the XRD analysis shows that in solidified samples with less than 10% cement, the main reason for reduction in peak intensity of clay fraction is due to the presence of heavy metals. However, as the percentage of cement increases, the clay solubility is the main reason for reduction in peak intensity of montmorillonite in XRD test

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Measuring of uniaxial compressive strength (UCS) of intact rocks is required in many engineering projects. In deep well drilling for petroleum production or exploration drilling in deep tunnels, because of depth of wells, obtaining suitable core samples for UCS test is too expensive and sometimes impossible. Therefore, indirect methods for determine UCS (for example using rock particles) are common. One of these methods is known as indentation test. In this test an indenter that is hard penetrates into rock particle which is surrounded by resin used. In this paper, 11 microcrystalline limestone block samples from carbonate Zagros formation outcrops were prepared and UCS test in laboratory was performed. Then cores are crushed and 720 rock particle samples with 2, 3 and 4 millimeter size was prepared. Indentation test with indenter 0.6, 0.8 and 1 millimeter diameter was done and critical transitional force (CTF) for each particles was determined. Empirical equation between UCS and CTF for different samples and has been provided. Based on the obtained results it is suggestedto utilize indenter with a R²&ge0.78. Using multiple regression general equation between UCS, CFT, particle size (D) indenter diameter (I), R²=0.85 is proposed. 135 indentation tests were performed on 3 microcrystalline limestone samples with the aim of verification of obtained empirical equations. Comparing measured UCS in laboratory and estimated UCS values showed 88% similarity

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Ground-Penetrating Radar (GPR) is a non-destructive and high-resolution geophysical method which uses high-frequency electromagnetic (EM) wave reflection off buried objects to detect them. In current research this method has been used to identify geometrical parameters of buried cylindrical targets such as tunnel structures. To achieve this aim, relationships between the geometrical parameters of cylindrical targets with the parameters of GPR hyperbolic response have been determined using two intelligent pattern recognition methods known as artificial neural network and template matching. To this goal GPR responses of synthetic cylindrical objects produced by 2D finite-difference method have been used as templates in the neural network and template matching algorithms. The structure of applied neural network has been designed based on extracting discriminant and unique features (eigenvalues and the norm of eigenvalues) from the GPR images and predicting all geometrical parameters of the targets, simultaneously. Also the template matching operation carried out using two diverse similarity approaches, spatial domain convolution and normalized cross correlation in 2D wave number domain. The results of the research show that both two employed intelligent methods can be applied for in situ, real-time, accurate and automatic interpretation of real GPR radargrams, however in general the neural network method has led to less error and better estimation than template matching to predict the geometrical parameters of the cylindrical tar

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Soil classification is one of the major parts of geotechnical studies. So assessment of existing methods for soil classification in different areas is important. For soil classification is used in situ and laboratory test results. Sampling and identification tests are laboratory methods for soil classification. CPTu test is in situ method for soil identification and classification, due to accuracy and speed, this test is used widely in geotechnical study today. Many researchers are proposed some charts for soil classifications based on the parameters measured in CPTu test. In this paper for evaluation the performance of these methods, 58 CPTu test results have been used. These tests are related to four areas in southern Iran. The soils are classified by CPTu methods and then they are compared with 372 laboratory soil classification. Research results show the chart proposed by Robertson (1990) which based on Qt, Ft and Bq variables has the best adaptation with the laboratory soil classification in these studied areas. Then according to data obtained from research, proposed a modified charts based on Rf, qt-u0/σ΄ v , that show 90% adaptation with laboratory soil classification.

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The Schmidt hammer provides a quick and inexpensive measure of surface hardness that is widely used for estimating the mechanical properties of rock material such as uniaxial compressive strength and Young’s modulus. On the other hand, Schmidt rebound hardness can be used for a variety of specific applications. In the mining industries, it is used to determine the quality of rock, which is common practice when constructing rock structures such as those found in long wall mining, room and pillar mining, open-pit mining, gate roadways, tunnels, dams, etc. However, a number of issues such as specimen dimensions, water content, hammer type, surface roughness, weathering, testing, data reduction and analysis procedures continue to influence the consistency and reliability of the Schmidt hammer test results. This paper presents: a) a critical review of these basic issues and b) avaluate the effect of temperature, moisture and uniaxial compressive stress on Schmidt hammer hardness. It was found that water content has a significant effect on the Schmidt rebound hardness (SRH) of rocks. So that increase of water content substantially reduced the SRH of samples. Temperature also had a considerable influence on the SRH. However, relationship between SRH decreases with increasing temperature for tested samples were linear. Also tests results showed that uniaxial loading of samples increases the SRH values.

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Tanks are structures for storing fluids that are made in different sizes, shapes and genera. Today using of tanks for water, petroleum products storage, and industrial wastes, has been developed significantly. The buried rectangular concrete tanks are used for water supply in most cities in our country. Soil-structure interaction is one of the most important issues in seismic behavior of buried tanks. With respects to code 123 that has suggested Mononobe-Okabe equation for dynamic pressure of earthquake excitation, the purpose of this research is to achieve the dynamic pressure of soil during earthquake. The obtained results have been compared to analytical and other experimental researches. Therefore, a series of small-scale experimental tests were conducted using 1g shaking table testing in the laboratory of physical modeling at University of Tehran. The results illustrate that dynamic force and pressure from Mononobe-Okabe and Wood equation are greater than experimental testing results. However Seed-Whitman equation is closer to experimental results.

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./files/site1/files/2.pdfExtended Abstract
(Paper pages175-200)
Introduction
In weak soils with low bearing capacity, the load transfer is done using piles. Therefore, by creating an interposed layer separating the pile from the raft, reactions between raft and pile head will be reduced and the load-bearing role of shallow soil will be more than contact pile situation. Normally, the pile head and shallow soil have a settlement equal to the raft. Thus, the relative settlement of pile and soil in pile head is equal to zero and at the bottom is high and the body friction mobilizes upward. In addition, a portion of load is tolerated by shallow soil and the other portion is tolerated by the pile head, which would be transferred to deeper soil layers. In noncontact state, with the formation of a hard soil layer on which the raft is located, soil mechanical parameters will be improved; while in contact state, the settlement will be decreased by reducing the amount of transferred load to the shallow soil. The transferred load to the shallow soil increases vertical and horizontal stress around piles, so bearing capacity of piles is increased.
Methodology
In this study, a parametric study has been performed concerning contact and noncontact piles using finite element software namely, ABAQUS/CAE software version 6.13.1 and the obtained results were compared (with what? The sentence is incomplete). Thus, simulations are is done for states of 0, 1, 4 and 9 piles for each of the contact and noncontact piles (total of 8 simulations). In the present research two models were taken to investigate the optimum mesh sizes, 12 models for parametric studies on parameters of piles’ length, piles’ diameter, thickness of the raft and interposed layer and one model for verification study. Models in both contact and noncontact have been considered with a one meter interposed layer. Raft width and thickness were selected 7.5 and 1.6 m, respectively. Width and depth of the soil mass used in the model were 32 and 26 m, respectively, and the distance between the bottom of the pile and the soil mass was 13 m. In all cases, the diameter of piles was 0.5 m and distance between piles were 5 and 2.5 m in 4 and 9 states, respectively. The geotechnical parameters and model dimensions used, were selected according to the Fioravante & Girettis (2010) [1]. Sand and silica-sand with the defined properties were used for the soil mass and the interposed layer, respectively. Since Drucker-Prager criteria has better ability to express the behavior of coarse-grained soils, this criterion was used in the modeling [2]. The purpose of this study is to investigate the influence of interposed layer on bearing capacity and settlement of pile. Hence, because of simplifying the process of modeling, parameters of main soil and interposed layer are mostly similar. Piles and raft are made of concrete with an elasticity modulus of 21 GPa, Poisson's ratio of 0.2 and density of 2300 kg/m³. The crack growth analysis with the compressive stress-plastic strain was used to express the fracture behavior of concrete [2, 3 & 4]. In the present study, frictional and vertical contacts between surfaces were considered for conducting interactions between different materials. For frictional contact, the penalty formulation with the fixed friction coefficient of tanδ was used where δ is the angle of friction. The penalty formulations and hard contact were applied between two surfaces for the normal contact. Interactions were considered in the modeling including raft-soil mass, raft-interposed layer, pile-raft, interposed layer-soil mass, interposed layer-pile and the soil-pile [5 & 6]. Coefficient of soil lateral pressure used in this study corresponds to k₀=0.65 which is introduced in many geotechnical conditions [7]. A uniform distributed vertical load 500 kPa was applied on the raft. For getting results in every portion of loading time, this amount is applied in order of 5 kPa in each time interval. To accelerate the process of analysis and because of the symmetry of all models in two directions of X and Y, the quarter model technique was used, so that movements in the direction perpendicular to the sheet and rotation around perpendicular axes on the sheet were not allowed on the border of symmetry. The boundaries of the models due to the enough distance from the piles were considered in a way that lateral displacement and rotation around the vertical axis was not allowed. Furthermore, the bottom of the soil mass was considered as complete fix due to the enough distance from the pile foot.
Conclusion
In this research, a numerical – parametric study is performed on special kind of piles named noncontact piles and results are compared with contact piles. Results of this study can be summarized as follows:
1. By increasing the number of piles from 1 to 9, the settlement reduced more in a noncontact state showing more effectiveness of implementing 9 contactpiles and thus requiring more piles in this case.
2. Soil surface stress differences in noncontacts states from 4 to 9 piles was less than contact state (approximately 1/7) indicating that more piles is needed to conduct the contact state.
3. Stress changes in the soil under the pile in noncontact state by adding piles from 1 to 4 was higher than adding piles from 4 to 9 indicating the suitability of using 4 noncontact piles; while, in the contact state, the stress changes in the soil under the pile in both cases from 1 to 4 piles and from 4 to 9 piles was noteworthy showing the necessity of using the ninth pile.
4. Unlike the states of 4 and 9 piles, the negative friction in noncontact state and 1 pile was seen along the piles, which can be due to the fewer piles and the effect of interposed layer density as well as soil mass at greater depthsbecause of lesser effect of piles in load-bearing.
5. The ratio of heads load in the contact to the noncontact piles was about 2.5 to 4 reflecting the positive impact of using interposed layer on load reduction and smaller cross-layer design for piles. In addition, the ratio of heads load in the contact to the noncontact piles was higher for 4 piles than 9 piles that represented the suitability of using 4 piles.
6. Based on the results of geometric parametric studies it is found that:
(A) By resizing the elements from 0.25 to 0.5 m, the results had not changed and only time of analysis was increased.
(B) Among three values of 0.5, 1 and 1.5 m for interposed layer thicknesses, the thickness of 1 m was enough and had a good effect on the stress distribution and involving shallow soil in bearing vertical stress.
(C) The raft thickness of 1.6 m was appropriate so that with this thickness, the resultant effect of increasing vertical loads (raft weight) and increased rigidity due to increased raft thickness caused the stress and settlements remain in a reasonable range.
(D) Due to the increased friction by increasing in diameter, the optimal diameter of 0.5 m was achieved for piles which reduced the settlement by receiving more load.
(E) Among three pile lengths of 10, 19 and 25 m, the optimal length was 19 m; so that by further increase in the length, stresses and settlements were not noticeably changed.In total, noncontact piles had better performance compared to contact piles in similar conditions.
Reference
1. Fioravante V., Giretti D., "Contact versus noncontact piled raft foundations", Can. Geotech. J. 47 (2010) 1271-1287.
2. Saba H., "Verification of nonlinear condition of anchored walls in various loading", Thesis document of Amirkabir University of Tehran, Iran (2003).
3. Fioravante V., "Load transfer from a raft to a pile with an interposed layer", Geotechnique 61, No. 2 (2011) 121-132.
4. Dastani H., Shariati M., "Numerical and experimental analysis of controlling of crack propagation route in a plane under cyclic uniaxial loading by creating openness", Thesis document of Shahrood Industrial University of Shahrood, Iran (2014).
5. Randolph M. F., Wroth C. P., "Application of the failure state in undrained simple shear to the shaft capacity of driven piles", Geotechnique, Vol. 31, 1 (1981) 143-157.
6. Poulos H. G., Small J. C., Ta L. D., Sinha J., Chen L., "Comparison of some methods for analysis of piled rafts", Proc. 14th Int. Conf. Soil Mech. Found. Engng, Hamburg, Balkema, Rotterdam, Vol. 2 (1997) 1119-1124.
7. mottaghi A., "3D static and dynamic analysis of pile group with considering soil-pile interaction", 6th National Congress of Civil Engineering, Iran, Semnan (2012).

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 IExtended Abstract
 Introduction
The Iranian plateau is situated in the Alpine-Himalayan orogeny between the Eurasian plate in the north and the Arabian plate in the south. It is being shortened by the northward movement of the Arabian plate, which causes the most parts of Iran to be active and dynamic in terms of tectonic movements. The recent tectonic activity in the southern edge of central Alborz causes both development and deformation of the tectonically active landforms. Seismic records indicate a high frequency of earthquakes of relatively small magnitude (<4) and infrequent large earthquakes (>5.1) in the Alborz. The studied area is located in the southern central Alborz and at the edge of northwestern central Iran between seismic faults of Ipak (with approximately E-W trend) and Avaj (with NW-SE trend) that includes significant earthquakes. Generally, the dominant tectonic structures of the study area involve thrust faults. The Ipak fault is one of the major fault systems in the area, located about 120 km west of Tehran, and caused the 1962 Buin Zahra earthquake of Ms 7.2 (Mw 7.0). The earthquake was associated with 95 km surface rupture along the Ipak reverse fault with average throw of 140 cm and left-lateral displacement of 60 cm. This investigation has evaluated the active tectonics and the acceleration zoning of the region in order to analyze and measure the recent tectonic activities.
Material and methods
To assess the acceleration zoning of this region, seismic data, Kijko software, PSHA software and reduction equations were used; consequently, minimum and maximum acceleration for useful life of 75-year and 475-year building were estimated. In order to assess the relative tectonic activity through the study area, sub-basins and stream network were extracted by using Arc Hydro Tools software based on the DEM and in turn, 134 sub-basins have been resulted. The six geomorphologic indices were used as follow: Stream length–gradient index (SL), mountain front Sinuosity (Smf), Ratio of valley floor width to valley height (Vf), Asymmetric factor (Af), Hypsometric integral (Hi) and drainage Basin shape (Bs). Eventually, after calculating the relative tectonic activity index (Iat), the studied area was classified into four tectonic activity classes in ArcGIS10.1 as very high, high, medium and low.
Stream Length–Gradient Index (SL): The SL index indicates an equation between erosive processing as streams and rivers flow and active tectonics. The SL is defined by Eq. (1) 
SL= (∆H/∆Lr) Lsc                                        (1)
where ΔH is change in altitude, ΔLr is the length of a reach, and Lsc is the horizontal length from the watershed divide to midpoint of the reach. The SL index can be used to evaluate relative tectonic activity.  The quantities of the SL index were computed along the streams for all sub-basins.
Index of Mountain Front Sinuosity (Smf):  Index of mountain front sinuosity is defined by Equation (2). 
Smf = Lmf ⁄ Ls                                             (2)
where Lmf is the length of the mountain front along the foot of the mountain in which a change in slope from the mountain to the piedmont occurs; and Ls is the straight line length of the mountain front. Smf represents a balance between erosive processes tending to erode a mountain front, making it more sinuous through streams that cut laterally and into the front and active vertical tectonics that tends to produce straight mountain fronts, often coincidental with active faults or folds.
Ratio of Valley Floor Width to Valley Height (Vf): Vf is defined as the ratio of the width of the valley floor to its average height and is computed by Equation (3).
Vf = Vfw/ [(Ald-Asc) + (Ard-Asc) /2)]                            (3)
where Vfw is the width of the valley floor, and A_ld, A_rd, and A_sc are the altitudes of the left and right divides (looking downstream) and the stream channel, respectively. A significant relationship exists between the rate of mountain front activity and the Vf index. Consequently, the high Vf values conform to low uplift rates (Keller and Pinter 2002). The shape of a valley can also represent the Vf amount and uplift rate. Therefore, U-shaped valleys accommodate low Vf and high uplift.
Asymmetric Factor (Af): The asymmetric factor (Af) is a way to evaluate the existence of tectonic tilting at the scale of a drainage basin. The method may be applied over a relatively large area. Af is defined by Equation (4).
Af= 100(Ar/At)                                                   (4)
where Ar is the area of the basin to the right (facing downstream) of the trunk stream and At is the total area of the drainage basin. If the value of this factor is close to 50, the basin has a stable condition with little or tilting; while values above or below 50 may result from basin tilting, resulting from tectonic activity or other geological conditions such as lithological structure.
Hypsometric integral (Hi): The hypsometric integral is an index that describes the distribution of the elevation of a given area or a landscape. The Hi is independent of basin area. This index is defined as the area below the hypsometric curve and thus expresses the volume of a basin that has not been eroded. A simple equation that may be used to calculate the index is defined by Equation (5).
Hi = (average elevation - min. elev.) / (max. elev. - min. elev.)  (5)
Then Hi values were grouped into three classes with respect to the convexity or concavity of the hypsometric curve: Class 1 with convex hypsometric curves (Hi≥0.5); Class 3 with concave hypsometric curves (Hi<0.4); and Class 2 with concave–convex hypsometric curves (0.4≤Hi<0.5).
Index of Drainage Basin Shape (Bs): Horizontal projection of basin shape may be described by the elongation ratio, Bs, expressed by Eqation (6):
Bs = Bl/Bw                                        (6)
where Bl is the length of the basin measured from the headwaters to the mouth, and Bw is the width of the basin measured at its widest point. High values of Bs are associated with elongated basins, generally related to relatively higher tectonic activity. Low values of Bs indicate a more circular-shaped basin, generally associated with low tectonic activity.
Evaluation of Relative Tectonic Activity (Iat): The average of the six measured geomorphic indices (Iat) was used to evaluate the distribution of relative tectonic activity in the study area. The values of the index were divided into four classes to define the degree of active tectonics.
Results and discussions
Results of probabilistic seismic hazard analysis have shown that the minimum and the maximum acceleration for useful life of 75-year building is estimated as 0.33g and 0.45g and for 475-year one are 0.46g and 0.60g, respectively. These values are indicative of high risk in the studied area. Acquired values from geomorphologic indices and also acceleration zoning of the realm are indicative of high recent tectonic activities near Ipak, Hasanabad, Soltaniyeh and Avaj faults; they are extremely concordant with the obtained evidences and geomorphologic characteristics of the field samples. In this study, considering the diversity of the morphotectonic features, six morphometric indices relevant to the river channels, drainage basins, and mountain fronts were computed for every catchment, and consequently, a single index (Iat) was calculated from the these indices for each of 134 subbasins to define the degree of active tectonics. Finally, the Index of the Active Tectonic (Iat) was calculated through which the study area is classified into four tectonic activity classes, from very high to low; 1—very high (1.0≤Iat<1.5); 2—high (1.5≤Iat<2.0); 3—moderate (2.0≤Iat<2.5); and 4—low (2.5≤Iat). The distribution of the four classes of Iat has been presented in a well classified map. The indices have represented a quantitative approach to differential geomorphic analysis related to erosion and depositional processes which include the river channel and valley morphology as well as tectonically derived features, such as fault scarps. We also evaluated the outputs of the morphometric analyses based on field-based geomorphological observations. Thus, these results are proved to be extremely beneficial to evaluate relative rates of active tectonics of this region.
The values of Af show widespread drainage basin asymmetry related to tectonic tilting, particularly associated with Ipak fault. The values of Smf suggest that mountain fronts are tectonically active, and the values of Vf show that some valleys are narrow and deep, suggesting a high rate of incision. The parts with class 1 and 2 of the relative tectonic activity are located along the main faults of the region, such as Soltaniyeh, Avaj, Hasanabad and Ipak faults and show high correlation with observed landforms during the field investigations such as the direct mountain fronts, fault gorges, fault scarps, and deep v-shaped valleys. Besides, the high amount of the relative active tectonic index shows a good consistency with the recent tectonic activity, namely tilting and deformation of the Quaternary units, which is the indicative of the effect of compressive stresses, affecting the region.
Conclusion
In this study, according to the current tectonic activity using the Iat index, it was found that the study region represents a high current tectonic activity along the fault zones. The values of SL, Hi, and Bs were found to be high along Soltaniyeh, Avaj, Hasanabad and Ipak faults segments.
According to the earthquakes and probabilistic seismic hazard analysis in the study area, it can be said is worthy to note that some basins which are located among active faults, are seismically dangerous.  However, they show low relative active tectonic index (Iat)../files/site1/files/121/AleeiAbstract(1).pdf

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Introduction
Contaminants can be categorized into organic and inorganic groups. Organic contaminants are carbon based, and their presence in waste forms may be as a single contaminant associated with inorganic contaminants, or a suite of complex mixtures which may be toxic at very low concentrations. Organics of greatest environmental concern are usually refined petroleum products, chlorinated and non-chlorinated solvents, manufactured biocides, organic sledges and substances from manufacturing processes. Most contamination due to organics are associated with accidental spills and leaks, originating from equipment cleaning, maintenance, storage tanks, residue from used containers and outdated material (Yong and Mulligan, 2004). Transport and fate of organic contaminants are important. Organic contamination migrations are due to advection (by fluid flow through soil) and diffusion, but other forms of transport e.g. infiltration may also contribute to migration (Environment Agency, 2002). The response of the soil to a contaminant depends upon the type of soil and the nature of the contaminant. The sensitivity of soil to contaminants depends upon the type of soil (such as particle size, mineral structure, bonding characteristics between particles and ion exchange capacity) and the nature of contaminants. Fang (1997) defined a sensitivity index (ranging from 0 to 1) to different types of soil. Sensitivity of sand and gravel (0.01 to 0.1) is much lower than clay particles (0.6-0.9). There are a number of techniques for remediation of contaminated land. These include physical (washing, flushing, thermal, vacuum extraction, solvent extraction), chemical (stabilization and solidification) and bioremediation techniques. However, the applicability and feasibility of different methods for remediation are dependent on many factors such as soil characteristics (soil type, degree of compaction and saturation), site geology, depth of contamination, extent of contaminant in lateral direction, topography, surface and ground water and the type and amount of contaminants. Thermal treatment and using surfactants are the most popular methods for remediating the soil contaminated with petroleum compounds. In this research remediation of a soil contaminated with different percentages of gasoline was studied through physical techniques in laboratory. The applied physical techniques were thermal technique and use of two different kinds of surfactants. The obtained results were compared with each other and discussion was performed.
Material and methods
Soil, gasoline and surfactant are the basic materials that were used in this work. The soil that was used in this testing program was a clayey soil. Two different types of ionic and nonionic surfactant, namely Tween 80 and SDS, were used in this work for remediating soil, contaminated with gasoline. Contaminated soil was prepared by adding 5 and 10 % weight (to air dried soil) of gasoline. 6 kg air dried soil was selected and the desired amount of gasoline was weighted, then it was sprayed on the soil and thoroughly mixed by hand for about 2 hours. The prepared mixture was kept inside a covered container for a week in order to come to equilibrium with the soil. For thermal remediation the contaminated soil with a specific percent of gasoline was kept inside a constant convection oven at 50, 100, and 150^oC for about one week to desorb the contaminating compound. Tween 80 and SDS were used for remediation of the contaminated soil. The amount of used Tween 80 was 25% weight of contaminating compound and selection of SDS amount was based on 50% weight of contaminating matter. The samples for the main tests were prepared by static compaction according to the optimum water content and maximum dry unit weight that were obtained from standard compaction tests. Atterberg limits, grain size distribution, compaction and unconfined compression tests were performed on samples of natural, contaminated and remediated soil according to the ASTM standard.
Results and discussion
The results of Atterberg limits (LL, PL and PI) for the contaminated soil (with 5 and 10 % gasoline) indicated that the values of them are increased with increasing the percent of gasoline. These values are nearly the same as natural soil after remediation with thermal method and surfactants. The grain size distribution curves were determined for the natural soil, contaminated soil with 5% and10% gasoline and soil remediated by thermal and surfactant techniques. The results showed that by using thermal technique the percent of clay is decreased and the percent of sand and particularly silt is increased by increasing temperature. The results of grain size distribution for the soils remediated by SDS and Tween 80 showed that the percent of clay is reduced but the percent of silt and sand are increased. Comparing the results of the two surfactants shows that the effect of Tween 80 in reduction of the percent of clay is more than SDS. The results showed that after thermal treatment, the maximum dry unit weight decreases and the optimum water content increases. For the contaminated soil with gasoline a reduction in maximum dry unit weight is observed compared with natural soil. The effect of SDS and Tween 80 on soil remediation is reduction in maximum dry unit weight and optimum water content. The results of compression strength showed that adding gasoline to soil causes a reduction in final strength and this reduction is a function of gasoline percent. The results also indicated that the strength of remediated soil by thermal or surfactant techniques, is reached nearly to the strength of natural soil. Scanning electron microscopy (SEM) tests were performed on the samples in order to observe the microstructure of the samples in different conditions (natural and contaminated with different percent of gasoline). The results of SEM showed that the structure of soil is changed by contamination to gasoline. It can be said that the gasoline causes reduction in the thickness of DDL because of low dielectric constant and hence a flocculated structure is formed. In the flocculated structure due to attractive forces, the fine particles paste to each other and form coarse particles. Therefore, variations in the Atterberg limits and compaction parameters can be resulted from forming new structure by adding gasoline. These results of compression strength are not in agreement with the theory of diffuse double layer (DDL). The reduction in dielectric constant would cause a flocculated structure in soil and the strength of the contaminated soil should be increased in comparison with the natural soil. It can be said the viscosity of gasoline cause reduction in the strength of contaminated soil.
Conclusion
In this experimental work a cohesive soil was contaminated with 5% and 10% of gasoline. The experimental tests showed that the properties of contaminated soil are different from natural soil and the change in the properties is a function of gasoline percent. The contaminated soil, was remediated by thermal treatment and also using two surfactants. The results also showed that using surfactants is more effective than using thermal method in soil remediation, and can treat the soil nearly to its original condition.
-Base on the SEM analysis results, adding gasoline to the soil, will change the soil micro structure to a flocculated one.  
-The gradation curves show that adding gasoline to the soil will change the gradation from finer to coarser.
- Contamination to gasoline will change the compaction parameters of the soil, and will reduce the soil final strength significantly.
- The results show that using thermal method and surfactants is effective in remediating the soil, but it is more effective to use surfactants. 
References
Yong, R.N., Mulligan,. “Natural attenuation of the contaminants in soil”, CRC press, Boca Raton, FL (2004).
Fang, M.Y. “Introduction to Environmental Geotechnology”, CRC Press,FL.USA, (1997).

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Introduction
Local site conditions considerably influence all characteristics of the ground strong motion including the domain, frequency content, and duration. The level of such an effect could be considered as a function of geometry, properties of the materials embedded in the underlying layers, the site topography, and properties of excitement. Site effect fall into two categories: a) the effect of the surface soft layers triggered by the shear velocity differences between the soil layers and b) the surface and subsurface topography effects that lead to the wave reflection and refraction based on the site geometry, and subsequently enhance the level of amplification.
Since most cities have been constructed in the vicinity of or on sedimentary basins, geotechnical earthquake engineering devotes particular attention to effects of the sedimentary basins. Basin edge curvature deposited with soft soils are capable to trap the body waves and generated surface waves within the deposit layers. Such waves could create stronger and lengthier vibrations than those estimated in a 1D analysis that assumes the shear waves to be vertically propagated.
Although critically important, the 2D effect of the site has not been included in seismic codes and standards of the world. This might be due to the fact that the site effect depends on a number of parameters such as the site geometry, the type of wave excitement, properties of the materials, etc. that in return make it almost out of the question to make predictions about the effect. This study was an effort to compare the responses of four sedimentary basins with hypothetical geometries of rectangular, trapezoidal, elliptical, and triangular shapes in order to examine the effect of the geometrical shape of the basin on its responses and the extent of the response sensitivity to the excitation frequency of the wave. The study assumed the edge to depth proportion to be both constant and equal in all four basins so that the effect of the geometrical shape could be equally examined and compared in all four basins.      
Material and methods
In order to validate the results of the sedimentary basin modeling, firstly, ABAQUS finite element software was used to create a free field motion of a semi-circular alluvium valley in accordance with Kamalian et al. (2006) and Moassesian and Darvinsky (1987).  Then, the results from the model were compared with those from the above mentioned studies. The following descriptions are to present the model in details.
To evaluate the geometrical effect of the sedimentary basin on its response, the authors relied on the software to examine four sedimentary basins with the fundamental frequency (2.04 Hz). The basins enjoyed rectangular, trapezoidal, elliptical, and triangular geometrical shapes with a constant edge to depth proportion (49m to 300m respectively). The implicit method was also applied to perform the dynamic analysis. The materials were all viscoelastic and homogeneous. The soil behavior/treatment model was considered to be of a linear nature.  The Rayleigh damping model was used to specify the damping level. The soil element was a plane strain and SV waves (the Ricker wavelet) were used for seismic loadings in a vertical dispersion. The side boundaries (right and left) of the model were of a combinational type (viscous and free field boundaries); the down side boundary was composed of viscous. To achieve higher levels of wave absorptions, heavy columns were used as the free filed columns.
Next, it was the time to conduct the 1D analysis of the site. Three waves were in use in order to examine the effect of the frequency content of the excitation load on the basin response: 1) a wave with the dominant frequency of 1Hz that was out of the frequency range of all basins (2.04 Hz), a second wave with the dominant frequency of 2Hz that was close to the fundamental frequency of all basins, and a third wave with the dominant frequency of 4Hz. The waves were applied to a 2Dmodel. The results were compared with those obtained from a 1Dmodel in terms of the timing.
Then, the basin responses to all three waves (1, 2, and 4 Hz) were subjected to an individual analysis in order to examine the sensitivity of each basin response to its geometrical shape. Results indicated that while the responses of the rectangular and trapezoidal basins were significantly more sensitive to the excitation frequencies, the elliptical and triangular basins showed more stable behaviors to such frequencies. The final stage of the study was dedicated to examine the site 2D effect during the ground motion.
Results and Conclusions
According to the results of the present study, it could be suggested that the geometrical shape of the sedimentary basin has a significant effect on the responses of the field of seismic waves and that it could result in so different responses from the ones attained after a 1D analysis of the site. In addition, the pattern of the seismic waves’ responses is highly dependent on the geometrical shape and the frequency content of the seismic load. Also, the location where the maximum horizontal acceleration occurs along with the sedimentary basin depends on the excitation wave and varies accordingly. Further, it could be suggested that the site 2D effect results in both considerable amplification and an increase in the length of ground motion.
The results of the 2D analysis showed remarkable differences with their 1D counterparts: a 1.45 larger response for the rectangular basin, a 1.28 larger response for the trapezoidal basin, a 1.22 larger response for the elliptical basin, and a 1.19 larger response for the triangular basin.
With the frequency of 1 Hz where the excitation frequency is out of the basin range (i.e. the excitation frequency is below the lowest frequency of basin), the sedimentary basin did not show any signs of amplification and chaos (unlike two other frequencies); instead, it was a cause for de-amplification.
The frequency of 2 Hz that is subject to resonance resulted in amplifications (absent in 1D analysis) and there are traces of a reduction in the acceleration responses near to the edges of the basins. The proportion of the amplification (in the center of the basins) in 2D to 1D analysis was 1.4 for the rectangular basin, 1.28 for the trapezoidal basin, 1.22 for the elliptical basin, and 1.15 for the triangular basin.
 

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Introduction
In general, landslides, in particular, earthquake-induced landslides, are among the phenomena that have caused great damages in recent years in Iran and the world. Although many studies have been done on the identification and description of landslides in general, the study of landslides caused by the earthquake, especially in Iran, is at the beginning stages. In a few studies, some landslides and some of their characteristics have been introduced. A magnitude 7.7 earthquake occurred in the Guilan Province was occurred on May 31, 1990. This earthquake is one of the most important earthquakes in Iran history due to its magnitude and occurrence of landslides. In various studies, the most important landslides have been listed. The development of quantitative and qualitative studies on earthquakes that have caused many landslides (such as the Manjil, Avaj, Firoozabad, Kojur, Sarein and Ahar and Varzaghan earthquakes) increase our understanding of natural disasters and, consequently, the management of the dangers resulting from them. The purpose of this research is to identify the factors affecting the occurrence of landslides caused by earthquakes, to determine the impact of each on the occurrence of this phenomenon, and also to prepare a map of earthquake hazard zonation hazard by utilizing the methods used in this research. In this study, hierarchical analysis method has been used to prioritize the factors affecting the occurrence of landslide and also the zoning of earthquake landslide hazard in the study area.
Research Methodology
The study area is located between 49˚ 30ꞌ and 49 ꞌ45˚ and latitudes 36º 00 ꞌ 45" and 36º 30ꞌ 52" with a surface area of ​​309.30 km². In this research, in order to zoning the earthquake-induced landslides hazard, in addition to providing a map of landslides, seven factors influencing the occurrence of this phenomenon were identified and examined. These factors included elevation, slope, arias intensity, friction angle, adhesion, curvature of the slope and aspect. In this research, Analytic Hierarchy Process (AHP) method, one of the multi-criteria decision making models, was used with two approaches to using expert knowledge and data and expert knowledge together to prioritize the factors influencing the occurrence of landslide. Finally, two landslide hazard zonation maps were prepared. In a hierarchical analysis method related to the expert judgment, it was used to determine the priority of different criteria and sub-criteria and convert them into small amounts of oral judgments (expert opinion) based on the pair comparison, in which the decision maker preferred the factor in relation to other factors using the relevant tables, these judgments are converted into small amounts. In the method of using data and expert judgment simultaneously, first, in order to determine the priority of criteria from oral judgments (collection of expert opinions), we used to determine the importance or weight (W_i) of each sub-criterion (R) is also used to link the landslide area to each class and landslide area in the region.
Results
The results obtained from the paired comparison of the effective factors in the occurrence of landslide show that the relative preference of the factors include the factor of arias intensity, friction angle, slope, adhesion, aspect, height and curvature of the amplitude. The greatest influence on the sub-criteria for the sub-criteria is 10-11.54, which is related to the arias factor and also the lowest effect for the sub-standard of the domain curvature factor. Also, according to the zoning maps, in the first model, 73% and in the second model, 57% of the surface area are very high and very high risk areas, which indicates the high sensitivity of the study area to the earthquake-induced earthquake phenomenon.
According to the results obtained from the verification and evaluation of the models and comparison of the mapped data with the hierarchical analysis method (using expert knowledge and data) and a method that uses only expert knowledge, the map is derived from a method where bundles of knowledge and data are used simultaneously, in order to weigh the parameters, it is more in line with the map of the landing list of the region.
Conclusion
According to the results obtained from the review and evaluation of the two models in a method in which knowledge and data were used together, the Q_S value was 0.40 and the accuracy of the method (P) was 0.016. However, in a method in which only the expert judgment used to weigh the criteria and sub-criteria, the sum of the quality and accuracy of the method were calculated to be 0.37 and 0.006, respectively. Hierarchical analysis method, in which the benchmarks and sub-criteria of benchmark knowledge and data are used together, have a better performance than the other model, and the results are closer to reality. In addition, it also works better in distinguishing between high and high risk areas../files/site1/files/124/5rajabi%DA%86%DA%A9%DB%8C%D8%AF%D9%87.pdf

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Introduction
Improving the mechanical behavior of clay soil by stabilization agents is a mean of fulfilling geotechnical design criteria. The method of stabilization can be divided into chemical, mechanical, or a combination of both methods. Chemical stabilization is performed by adding chemical agents such as cement, lime or fly ash to the soil (Bahar et al., 2004). Soil reinforcement is one of the mechanical methods that is used for improving the behavior of soils (Tang et al., 2007). Reinforcement of soil achieved by either inclusion of strips, bars, grids and etc. within a soil mass in a preferred direction or mixing discrete fibers randomly with a soil mass.
Mixing of cement with soil is made a production that is called soil-cement and results in chemical reaction between soil, cement, and water. The compressive strength of soil-cement is increased by increasing the cement content and this leads to brittle behavior or sudden failure. On the other hand, by increasing the cement to soil ratio for cohesive soils, shrinkage micro-cracks may develop in the soil as a result of the loss of water content during drying or hydration of cement. Therefore, if the tensile strength of these materials is not sufficient cracks will develop under loading and damage will be resulted (Khattak and Alrashidi, 2006). Consoli et al. (2003) and Tang et al. (2007) indicated that adding the fiber to soil can prevent from occurrence of these cracks and increases the tensile strength of the soil.
The focus of this paper is on the statistical analysis of the results and development of regression models. Regression relationships are developed based on the experimental results that were presented by Estabragh et al. (2017). These relationships relate the compressive and tensile strengths of the soil to percent of used fiber, cement and curing time.
Material and methods of testing
Unconfined compression and tensile strength tests were carried on unreinforced and reinforced soil, soil cement according to ASTM standards. Samples of soil-cement were made by mixing a clay soil and two different weight percent of cement (8 and 10%). Reinforced soil samples were also prepared by mixing 0.5 and 1 weight percent of Polypropylene fibers with 10, 15, 20 and 25 mm lengths. The dry unit weight and water content of prepared samples were the same as optimum water content and maximum dry unit weight that were resulted from standard compaction test. The compressive and tensile strength tests were conducted on the samples by considering the curing time according to ASTM standards until the failure of the sample is achieved.
Results and discussion
The experimental tests showed that reinforcement of the soil and soil cement increase the peak compressive and tensile strength. The peak compressive strength of reinforced soil is increased by increasing the fiber content at a constant length of the fiber. It can be said that by increasing the percent of fiber, the number of fibers in the sample is increased and contact between soil particle and fibers is increased which result in increase in the strength (Maher 1994). However, by increasing the length of the constant fiber inclusion there will be no significant increase in strength because the number of shorter fiber is more than longer fiber in a specific sample (Ahmad et al., 2010). Inclusion of fibers can greatly increase the tensile strength of clay soil. In addition to reinforcement of soil cement showed the same trend. When fiber is added to soil cement, the surface of fiber adheres to the hydration products of cement and some clay particle. Therefore, this combination increases the efficiency of load transfer from the composition to the fibers which increase the peak strength (Tang et al., 2007). In addition, the tensile strength shows the same trend.
Based on the experimental data on the behavior of a randomly reinforced clay soil and soil cement multiple regression models (linear and non-linear) were developed for calculating the peak compressive and tensile strength (dependent variables) based on the value of the coefficient of determination (R²). The proposed regression models were functions of independent variables including weight percent of fiber, length of fiber (length/diameter of fiber), weight percent of cement, and curing time. Finally, the comparison is made between the predicted results from proposed models and experimental results. In order to investigate the model accuracy, the Root Mean Square Error (RMSE) and Normalized Root Mean Square Error (NRMSE) are used.
 The Multiple Linear Regression models (MLR) was very suitable for the study of the effect of independent variables on the quantitative analytic dependent variable. The NRSME for peak compressive and tensile strength is was 3.59% and 5.11% respectively for these models. Also, the Multiple Nonlinear Regression models (MNLR) had a much lower error than the linear model because of the quadratic equation, the equation will be able to predict the increase and decrease of the output variable in terms of the increase of the independent input variable. Therefore, The NRMSE for peak compressive and tensile strength was 1.02% and 4.04% for MNLR models respectively.
Conclusion
The following conclusions can be drawn from this study:
- The strength of reinforced soil and soil cement is increased by increasing the fiber content.
- Increasing the length of the fibers in the soil and soil cement has no significant effect on increasing the peak compressive strength, but it will be effective in increasing the tensile strength.
- The Multiple Nonlinear Regression models (MNLR) have more accuracy for prediction of output variable (peak strength) because of lower normalized root mean square error../files/site1/files/131/7Extended_Abstract.pdf


 

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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