Journal of Engineering Geology

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Introduction
The dispersivity phenomenon occurs due to the dissolution of some of the ions in clay soils or against the shear stress of normal water flow in cohesion-less soils. Water surface flows in low slopes cause surface erosion of dispersive soils. Dispersivity in the soil starts from a point and gradually expands; the starting point can be the holes from the activity of the animals, the existing cracks or the growth path of the roots of the plants. There is a lot of field evidence to recognize the dispersivity of the loess soils. In field investigations, soil dispersivity can be detected according to the following parameters: geological origin of the loess soil, mineralogical composition, gradation, drainage pattern, slaking of agglomerates, specific morphology, high permeability, geographical area (length and width relative to origin), soil color, relationship between slope and soil erosion, precipitation, erosion of column cracks, heeling, mud flowing runoff and the presence of salt crystals in loess soils. In terms of sedimentological characteristics and engineering geological properties, Golestan loesses have been dispersed in three areas 1, 2 and 3, which are consistent with the loesses of clay, silt, and sand types, respectively.
Material and methods
Loess soils in three regions of east and northeast of Golestan province were sampled. Sampling was conducted in two forms of wax-coated agglomerates and metallic cylindrical tubes. Depth of sampling follows the foundation of the buildings located on the Mehr Housing site and the Cheshme Lee village, varying from 0.5 to 2 meters. On the path of the Beqqeje Bala village, sampling was carried out from the path trench. After transferring to the laboratory, samples were subjected to gradation testing, Atterberg limits test to determine the unit weight of the volume and density.
The pinhole test was done on samples with the unit weight of normal volume (g_n) and maximum volume (g_dmax) and its rate of dispersion was determined. The research background, field evidence and the results of laboratory experiments indicate the dispersion of soil sampling areas. The results show that soil compaction reduces the severity of dispersion and decreases the flow rate, so that the flow rate has decreased in the Maravehtapeh sample by 38%, in the Cheshmeli sample by 13% and in the Beqqeje Bala sample by 43%. Compaction cannot eliminate the dispersion of soil. Adding nanoclay decreases the severity of soil dispersion and eliminates its dispersion properties in most cases.
In order to evaluate the effect of nanoclay on severity and to decrease the dispersion property of soil with ratios of 0.5, 1, 2, 3, 4 and 5 wt%, of Montmorillonite Nanoclay was added.
The nanoclay used in the present research was selected from the Sigma-Aldrich America Company called montmorillonite nanoclay and was purchased from its domestic representative, i.e. Iranian Nanomaterials Pioneers Company. The product has a density of 300 to 370 kilograms per cubic meter and a particle size of between 1 and 2 nm. The specific surface area of the nanoparticle is about 250 square meters per gram. Its color in normal light and in 1 to 2% moisture is yellow to yellowish buff.
Results and discussion
The rate of dispersion of samples with nanoclay was measured in Pinhole Test Apparatus. Also, the method of mixing nanoclay with dispersive soil shows different behaviors in severity of dispersion and its reduction. Given that the specific surface of nanoclay is high and this property can include the whole surface of soil grains as a sticky coating and increase soil cohesion, the mixing method is practically one of the most important steps in examining the effect of nanoclay on soil stabilization. At ratios of 0.5, 1, 2, 3, 4 and 5 wt% of nanoclay, nanoclay was mixed with soils of sampling regions by four methods:
In the method A, they were completely mixed with the preparation of a homogeneous mud from soil and nanoclay via an electric mixer.
In the method B, mixing of loess soil with nanoclay was performed in optimum water content.
In the method C, mixing of loess soil with nanoclay was conducted in the form of dough by hand mixer. In the method D, mixing of loess soil with nanoclay was carried out in the form of vibration dry by grading sieve shaker.
After mixing with nanoclay in the desired method (four methods A, B, C, D), the samples were first stored in sealed plastic containers for 24 hours. Then, the samples containing nanoclay were reconstructed in cylindrical mold of the pinhole device with the unit weight of maximum dry volume and moisture of two percent higher than the optimum moisture content and a hole was created in the middle of it. The samples remained in this position for 24 hours, and then the test was performed. Testing was carried out on each sample according to the standard D4647-93, and flow rate reading was done over a period of two minutes to 18 minutes.
Conclusion
The conclusion of this study shows that the three loess samples taken have a dispersivity potential and the flow rate is low in the unit weight of maximum volume, but the dispersivity potential does not eliminate. Adding nanoclay with any weight ratio reduces the flow rate and eliminates the soil dispersivity potential.
The results of this survey showed that 1% nanoclay weight ratio is technically and economically the most appropriate mixing ratio. With this weight ratio, the method of preparing homogeneous mud with an electric mixer (method A) produces the lowest flow rate, so that the flow rate from 1.3 ml per second in pure soil to 0.3 ml per second in the soil containing nanoclay is reduced by 50 mm. Therefore, it can be said that this method is more suitable, but it is not operationally efficient and the method B is more appropriate. In the method B, the flow rate reaches from 1.3 to 0.55 ml per second.

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Introduction
The main objective of this contribution is to focus on the portion of the comminution process which deals with the prediction of the energy consumption due to the comminution portion of the milling processes.
The comminution energy in mineral processing and cement industry is usually determined by empirical Bond Work Index (BWI), regardless of the mechanical properties of a rock. The BWI is a measure of ore resistance against grinding and is determined by using the Bond grindability test. Determining the BWI value is quite complicated and time consuming. Its value constitutes ore characteristic and is used for industrial commination plants designing and optimization. The BWI is defined as the calculated specific energy (kW h/t) applied in reducing material of infinite particle size to 80% passing 100 µm. The higher the value for BWI, the more energy is required to grind a material in a ball mill. The energy consumed in the process of comminution depends on both the mechanism of comminution and the mechanical properties of the materials being ground. It is interesting to study the effect of the essential ones of these properties on the energy efficiency of grinding process.
Material and methods
Several attempts have been made to obtain and optimize the comminution energy. An efficient Response Surface Method, (RSM)-based method for the BWI approximate value determination, which is based on physico-mechanical tests, is presented in this paper.
BWI and some physico-mechanical tests on 8 typical rock samples and its correlation are studied; it would be beneficial to examine this relation based on physical concept. The database including Uniaxial Compressive Strength (UCS), Abrasion (AT), Hardness (HT) and Modulus of Elasticity (ME) are assembled by collecting data from Haffez experiments.
Results and discussion
The determination of the BWI from RSM- based multivariate model is almost matched with measured Bond’s work index. As a result of analysis the best equation obtained from RSM-based model is formulized in Equation 1:
                                      (1)
Standard statistical evaluation criteria are used to evaluate the performances of predictive models.
Conclusion
The performance of the estimator models can be controlled by R², VAF, RMSE, MAPE, VARE and MEDAE. The RSM- based model with higher VAF as well as lower RMSE, MAPE, VARE, MEDAE shows better performance in comparison to the Haffez single-variable models. AT and ME have the greatest effect on the value of BWI; and also HT has the least impact../files/site1/files/134/6.pdf

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Because of the diversity in petrography, peridotites have variable physical and mechanical properties. For this reason, knowledge of resistance properties and their deformation will help with the prediction of engineering behavior of these rocks. Due to the large spread of igneous rocks, especially peridotite, in Zagros, northeastern and central Iran, special attention has been paid to their petrographic, physical and mechanical characteristics. The construction of the structure within or on the peridotites and the choice for the purpose of the stone borrow depends on the recognition of its engineering geology characteristics. In this paper, in addition to the field and laboratory study, the geological characteristics of peridotite engineering has been investigated.                                    
Material and methods                    
In order to study the geological characteristics of the peridotites of Harsin region, 15 suitable blocks were selected and transferred to the laboratory. Accordingly, from collected rock samples, 150 cylindrical cores of diameter 54 mm were prepared and physical and mechanical tests were performed according to (ISRM, 2007) and (ASTM, 2001) guidelines. In this research, after sampling of the study area and preparing the core for the lithological characteristics of the samples by providing thin sections of them with polarizing microscopy was studied.
Results and discussion
By considering the results of laboratory tests and analysis from Harsin peridotites in Kermanshah province, we can acclaim that with increasing the percentage of minerals in olivine and pyroxene in rock, the strength was decreased and the levels weaknesses, which is due to the weak structure of the mineral-olivine and pyroxene. According to the physical properties test and Anon classification, the porosity percentage in porosity percentage is low and as a result the amount of water absorption index is low. Based on the Gamble classification, all peridotites are very resistant to durability and based on the Franklin and Chandra classification, all samples are extremely resistant. The results of this study showed that the single axial compressive strength, elasticity modulus, point load index and tensile strength were decreased with an increase in humidity content of peridotite samples. This is due to the fact that with the increase of humidity pore pressure of water increases. According to the Anon classification, the peridotites are very high in terms of the length of the longitudinal passage through the rock. The highest compliance between the Brazilian Tensile strength test (BTS) and Schmidt hammer (SHV) was achieved in the dry condition and the determination coefficient (R²) equals to 0.95 was obtained. Also there is an acceptable relation between the Brazilian Tensile Strength Test (BTS) and the dry volume unit weight (γ_d) with the determination coefficient (R²) of 0.93. In addition, there is an admissible relationship between durability test and single-axial compressive strength, with a coefficient determination (R²) of 0.94. Regarding the obtained regressions in this study, the physical and mechanical properties show good agreement and most of the equations have an acceptable coefficient determination.

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Introduction
Drilling has various methods that from different aspects such as crushing mechanism, type of used energy etc., is divided to several types containing hand held drilling, percussive drilling, cable-tool drilling, rotary (or circular) drilling, percussive-rotary drilling and core drilling. Unlike the direct circulation drilling system (DC) in the reverse circulation drilling system (RC), the drilling fluid moves the annulus between borehole wall and the drilling pipe and comes back with the drilled pieces along inside the drilling pipe. The exploratory drilling system of RC by conducting powder samples with high purity and fast drilling rate, is a great help to the velocity and accurate of exploration of ore deposits. Samples produced in this method are in the form of soil and rock powdered and rock fragments of the drilled part, which may be dry or with little moisture. The air flow inside the cycle causes the collected powder sample to be often dry but sometimes is wet due to groundwater or drilling mud. Drilling is one of the most costly mining processes. Therefore, the most important goal in drilling engineering is to reduce costs, and the best possible decision to optimize the cost of drilling is to choose the best possible drilling method. Based on the field data, cost of drilling for each meter of a soft rock (e.g. travertine) by core drilling and direct drilling methods are about 3.3 and 1.2 times of the RC method, respectively. Also the cost of drilling, for each meter of a hard rock (e.g. granite) by core drilling and direct drilling methods are about 2.6 and 1.3 times of the RC method, respectively.
Materials and methods
In the present research, reverse circulation drilling (RC) has been compared with other important, common and practical drilling methods, such as direct circulation and core drilling methods in terms of various criteria containing drilling (time) rate, price (cost), type and quality of acquired samples and performance efficiency of drilling. Also, as a field study in this research, deep drilled boreholes with RC and core drilling methods in the gold mine of Khomein-Akhtarchi located in the Markazi province, were investigated and compared from different aspects. At the end, the ability to select the most appropriate drilling method among the variety of methods was studied. The study region is located at 25 km northeast of Khomein city in the Markazi province. This region consists of two exploration areas of Zarmadan-Akhtaran1 with the area of 13.21 square kilometers and Zarmadan-Akhtaran2 with the area of 2.85 square kilometers. Access to the Akhtarchi gold region is possible through the Khomein-Shahabiyeh (Goldsat)-Mahallat road. In the mining region, the Permian rock complexes include dolomite, dolomitic limestone from brown to dark gray, black Irony sandstone and white to milky limestone known as p^ds, p^dl and p^l units in the geological maps.
In the studied region, several deep boreholes, most of them by RC and some of them by core drilling methods have been drilled. In general, by now in the Akhtarchi gold zone in the Zarmadan-Akhtaran2 area 54 powder boreholes have been drilled through RC method called by RC1 to RC54. Also, there are 25 core drilling boreholes, 18 boreholes called by BH1 to BH18 in the Zarmadan-Akhtaran1 area and 5 boreholes called by BH1 to BH5 in the Zarmadan-Akhtaran2 area. During drilling operations, Permian and Cretaceous rock units have been encountered. The details of drilling via RC method for 4 boreholes with numbers 50, 51, 53 and 54 have been accurately taken. The measured drilling times were obtained from drilling personnel of the mine through the questionnaire which they were weighted mean if needed.
Results and discussion
The average drilling time for each meter of rock in boreholes 53 and 54 is 2:12 and 2:54 minutes, respectively. In both cases, the time duration is very short and this feature is one of the advantages of the RC drilling method. The longer average duration of drilling for each meter of rock in the borehole 54 than 53, is due to the depth of the borehole 54 and the hammer problem of the drilling machine during the drilling this borehole. In Table 1, the average duration of drilling operation per meter of rock in the Akhtarchi gold mine is given according to the type of rock (lithology) at definite depth intervals, on the basis of field studies. According to this table data, the duration of the drilling for each meter of rock in the greater depths increases that the reasons for increasing the duration of drilling for each meter of rock in greater depths are the difficulty of drilling due to the increasing length of rig, the reduction of transient energy to the bit, the probability of greater borehole declination, compaction increasing and as a result increasing the strength of rocks and more hydrostatic and lithostatic pressures in the great depths meanwhile at a great depth, the probability of capturing the drilling rig is too high. Also the cost (the time price) of drilling per meter of rock in this mine based on the dip and depth of drilling is about 1300 to 2000 thousand Rials by the RC method, against 2620 to 4250 thousand Rials by the core drilling method.
The results of the present research indicate that the RC drilling in comparison with other drilling methods, especially conventional and applied ones in terms of drilling costs and drilling rate (time) is highly desirable while is desirable regarding depth of drilling, the type and quality of the acquired samples and the overall efficiency of drilling performance. Although the core drilling method with the ability to drill very deep boreholes obtaining cores in terms of the type and quality of the acquired samples, as well as the depth of the drilling is the most desirable, but for exploration drilling (especially in the detailed exploration stages), deposits with low-grade and very little mineral indices (like gold mine of Khomein-Akhtarchi), and hence the large sample sizes are needed, employing RC drilling method having comparative advantages is economic.
Conclusion
Regarding the use of RC drilling method in the case study, the gold mine of Khomein-Akhtarchi, it was found that the RC method compared to the core drilling method, in terms of the duration of drilling operations or the speed of advance (the rate of penetration in the rock), drilling costs and efficiency of performance is desirable. Also, according to the type of mineral deposit (gold type), which is low-grade and the indices of the mineral are very low, therefore the large sample sizes are needed, thus, in terms of the type of obtained samples, employing RC drilling method in this case, is accounted a very important advantage related to the DC method (in terms of accuracy) and core drilling method (in terms of cost). The results of this research are useful for all users of drilling operations, including drilling engineers and technicians, engineering geology and geotechnical practitioners, mineral exploration engineers, groundwater aquifers and hydrocarbon reserves (oil and gas) to choose the optimal drilling method under different environmental and economic conditions based on criteria such as the purpose of drilling operations, costs, progress rate, type and quality of the yielded samples and the efficiency of drilling operation. Also, the use of RC drilling method has the advantages over the other drilling methods to be suggested for exploration of low-grade deposits such as gold, silver and copper, especially in the final stages such as detailed and mining exploration.
 

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Introduction
Dispersive soils are problematic and they cause a great many of local damages and destructions in hydraulic structures such as dikes and irrigation channels. The correct identification and recognition of divergence are fundamental measures taken in line with preventing the early destruction of the hydraulic structures. The soil improvement using lime, especially in clayey soils (CL), brings about an increase in the optimum moisture percentage, reduction of the maximum dry unit weight, reduction of swelling potential, increase in the strength and elasticity module. The effect of lime on soil can be classified into two groups, namely short and long-term stabilization. Raise of the soil’s workability is counted amongst the short-term modification measures and it is the most important factor in the early improvement stages. The increase in the strength and stability can be considered as the lime utilization on long-term results occurring during curing and afterwards. Also, according to the reports, swelling and damages occur in the lime-stabilized soil containing sulfate. The effective role of the iron furnace slag has been well recognized in increasing the strength against sulfates and corrosive environment conditions of the mortar containing lime and sulfates.
Material and methods
Adding the slag products of the melting furnaces and lime is a method used to stabilize dispersive soils. The present study makes use of a mixture of clay featuring low plasticity with 1% and 2% lime and slag, for 0.5%, 1%, 3% and 5% of the weight, to improve dispersivity, shear strength and plasticity. The samples were kept in constant temperature and humidity for a day and then were subjected to direct shear, uniaxial strength and pinhole tests.
Results and discussion
It was observed based on pinhole experiment of the initial dispersive soil sample, denoted as D1, that the sample, shown by ND2, containing lime, for 2% of the weight, and slag, for 5% of the weight, turned out to have become non-divergent. The results of the direct shear test showed that the adhesion coefficient of the slag-free samples stabilized using 1% lime has been increased from 0.238 kg/cm² to, respectively, 0.251 kg/cm², 0.373 kg/cm², 0.41 kg/cm² and 0.48 kg/cm²  per every 0.5%, 1%, 3% and 5% slag added. The adhesion of the samples stabilized using 2% lime as determined in the direct shear experiment were 0.615 kg/cm², 0.671 kg/cm², 0.724kg/cm² and 0.757kg/cm² per every 0.5%, 1%, 3% and 5% slag added. Also, the internal friction angle of the samples stabilized using 1% lime was found an increase from 14.3° for slag-free samples to 18.11°, 21.3°, 21.86° and 21.92° per every 0.5%, 1%, 3% and 5% added slag. As for the samples stabilized using 2% lime, the internal friction angles were found in direct shear test equal to 23.15°, 23.53°, 23.76° and 24.12° per every 0.5%, 1%, 3% and 5% slag added. The uniaxial strength of the slag-free samples stabilized using 1% lime was found an increase  from 1.0014 kg/cm² to, respectively, 1.0616 kg/cm², 1.0782 kg/cm², 1.2127 kg/cm² and 1.2246 kg/cm² per every 0.5%, 1%, 3% and 5% slag added. The uniaxial strength rates has been determined in the direct shear test of the samples stabilized using 2% lime were 1.1367 kg/cm², 1.1885 kg/cm², 1.2322 kg/cm² and 1.2872 kg/cm² per every 0.5%, 1%, 3% and 5% slag added. The amount of axial strain of the slag free samples stabilized using 1% lime was found decreased from 9.6842% to, respectively, 9.3333%, 9.2683%, 9.6364% and 8.4444% per every 0.5%, 1%, 3% and 5% slag added. Moreover, the axial strain amounts obtained for the samples stabilized using 2% lime were 7.7333 kg/cm², 7.6316 kg/cm², 7.1517 kg/cm² and 4.7619 kg/cm² per every 0.5%, 1%, 3% and 5% slag added.
The study results indicate that slag and lime have the capacity of improving the studied soil’s dispersivity. Furthermore, it was figured out that adding slag to the soil causes an increase in the soil strength and improves the shear strength parameters. It can be stated according to the observed results that the use of slag, a byproduct of iron smelting industry, as a substitute for a given percentage of lime is effective on the reduction of the clay soil’s divergence potential. The results of the experiments carried out to determine Atterberg limits are suggestive of the idea that the increase in the slag and lime fractions brings about a decrease in the liquid limit and plasticity and improves the plasticity properties of the soil. The reason why the soil plasticity has been reduced after being mixed with lime and slag is the cationic exchange and coarsening of the soil texture. Addition of lime to the soil causes an increase in the plasticity limit and a reduction in the liquid limit. Therefore, the plasticity index is decreased and the plasticity characteristics of the soil are improved. Adding 1% lime to the dispersive soil leads to small reduction of the liquid limit from 32.43% to 31.73%, a small increase in the plasticity limit from 13.42% to 14.66% and a insignificant decrease in the plasticity index from 19.01% to 17.07%.

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Introduction
Pavement layers as a part of road structure play an important role and provide a flat and secure surface. Subgrade layer could act as a compacted embankment, natural or stabilized ground. Subgrade is a foundation of pavement layers, and it withstands all of loads due to vehicles that are transferred from upper layers (i.e., subbase, base and asphalt layers).Therefore, constructing pavements with bearing capability, high durability, quality, and maintenance in proper operating conditions is very important. However, suitable materials for constructing pavement layers are not available, and improvement techniques should be employed for them. Generally, different methods such as mechanical or chemical are available for improvement. Nowadays, geosynthetic materials such as geotextile and geogrid are used to optimize and enhance the bearing capacity of pavement layers. The present study is aimed to investigate the effects of geotextile applications on bearing capacity of clay-gravel mixtures in pavement layers.
Material and Methods
In this research, materials were prepared from Barandouz area. Clayey soil was mixed with gravel in 25, 50 and 75 percentages (by weight). Geotextile was woven and made of polypropylene (with commercial name Fibertex-F-32). Geotextile effects in mixture were evaluated in two conditions. Position number one indicates the arrangement of geotextile.  This means, at first, one geotextile layer was embedded in the middle of materials. Then, two and three geotextile layers in equal depths from each other were used in soil mixtures. Position number two shows the mixing pieces randomly. This means that geotextile pieces in 1×1 and 5×5 cm² were prepared and were randomly mixed with materials in 1, 2 and 3 percentages (by weight). For evaluating geotechnical behavior of improved clay-gravel mixtures, compaction and California bearing ratio test (CBR) (in dry and saturate conditions) based on ASTM were performed.        
It should be noted CBR test in dry and saturate conditions were carried out in three different compaction energies (i.e. 10, 25 and 56 blow count for per layer). Moreover, CBR was evaluated for piston penetration at 2.5 and 5 cm in the specimen.
Results and discussion
The findings of this study could be summarized as:
1. Results of compaction test showed that, in the unimproved position, with increasing gravel content in clay, maximum dry unit weight (γd_max) has been increased, while simultaneous optimum water content (w_opt) decreased.
In the improved position, in the first mode, when a geotextile layer was embedded in the middle of the specimens, γd_max reached to its upper value, whereas w_opt reached to its minimum value. On the other hand, with an increase in the number of geotextile layers in clay-gravel mixtures, dry density has been decreased, but optimum water content increased. Furthermore, in the second mode, when geotextile pieces with 1×1 and 5×5 cm² were randomly mixed in the specimens, the findings revealed that geotextile pieces with 1 cm² areas and 1% by weight in clay-gravel mixtures increases γd_max and reduces w_opt.
2. In dry and saturate conditions, California bearing ratio (CBR) test result displayed that in the unimproved condition, with an increase in gravel content in the clay, CBR value has been increased. In the improved situation, in the first mode, when a geotextile layer was embedded in the samples, CBR had a maximum value in all of the compaction energies even though it is reduced as the number of layers increased. In the second mode, when geotextile pieces in 1×1 cm dimensions with 1% (by weight) were randomly mixed with the specimens, CBR value reached at high.  In contrast, with increasing dimensions of pieces and percentages in the presence of geotextile in clay-gravel mixtures, CBR values declined.  Therefore, it can be concluded that, according to Code 234 (Iran Highway Asphalt Paving Code), the application of one geotextile sheet in the middle of materials or geotextile pieces in 1×1 cm dimensions with 1% (by weight) random mixing  is suitable for subbase and base layers in pavement design.
3. CBR test results in the saturate condition in clay-gravel mixtures illustrated that, in the non-reinforced condition, with an increase in clay content in specimens, swelling value keeps rising sharply. On the contrary, in the reinforced position with embedding a geotextile layer in the middle sector of samples or through adding geotextile pieces (1 cm²) with 1 % content  (by weight) to the specimens, the rate of swelling significantly decreased.   
Conclusion
To sum up, the main objective of the present study was to investigate the impact of geotextile applications on bearing capacity of clay-gravel mixtures in pavement layers. The findings demonstrated that when geotextile as a layer was embedded in the middle part of specimens or as pieces with 1×1 cm dimensions and 1% content (by weight) was randomly mixed with the mid materials, the bearing capacity of the reinforced specimens was enhanced.  In contrast, in the saturate condition, swelling potential significantly was reduced. It is noteworthy to mention that 1 cm² pieces of geotextile is more effective than the layers. This is due to the fact these pieces make aggregates closer to each other. Thereby, minimum void ratio (e_min) reaches its least value, the structure of grading improves, and the contacts between particles and geotextile pieces rise. As a suggestion for further research, it looks promising to evaluate the dynamic properties and the behavior of the improved materials with other geosyntheticses.
 

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Introduction
Drill-bit selection is one of the most important aspects of well planning due to the bearing it can have on the overall cost of the well. Bit selection in conventional and slightly inclined wells is a very delicate and complex process. In high angle and horizontal wells it is even more difficult. Historically, drilling engineers have selected bits on the basis of what has been worked well in the area and what has been determined to have the lowest cost run from offset bit records. Often the best bit records were not available for evaluation, because the best bit may not yet have been run, may have been run by a competitor or the engineer was new to the area. As a result the bit program was generally developed by trial and error and at significant additional costs for a large number of wells. In most cases the optimum program was never reached because there was nothing to predict that a bit selection change could further reduce the cost of the well. In this study, an alternative solution approaches using the concept of the power of data mining algorithms to solve the optimum bit program for a given field is proposed.
Material and methods
It has been considered an offset well to be drilled outside the known boundaries of a known field. For this purpose, the seventh well (X-7) of the same field was used as a verification point. The data was trained using the well log and rock bit data of six wells located in the field and the real well log data of well 7 was input as unknown data. These depths are selected based on reported rock bit program. When compared to the real data, it could be observed that the models (adaptive neuro fuzzy inference system, K-nearest neighbors, decision tree, Bayesian classification theory and association rules) estimates the formation hardness accurately. This minor discrepancy was also present with the company’s suggested rock bit program, which was based on the previous wells’ rock bit data.
Results and discussion
In this paper, data mining algorithms for optimum rock bit program estimation is proposed. The accuracy and efficiency of the developed data mining algorithms (adaptive neuro fuzzy inference system, K-nearest neighbors, decision tree, Bayesian classification theory and association rules) that requires sonic and neutron log data input was tested for several real and synthetic cases. In the case of a development? well to be drilled outside the known boundaries of a field the model estimated rock bits with properties that consider the formation hardness correctly but slightly underestimated further rock bit details. The models also produced reasonable rock bit programs for an advance well to be drilled within the known boundaries of a field and a wildcat well drilled in a nearby field with similar rock properties to the training field. Thus it was concluded that the developed adaptive neuro fuzzy inference system is suitable as a front-end system for rock bit selection that could help engineers in decision-making analysis.
Conclusion
Optimum bit selection is one of the important issues in drilling engineering. Usually, optimum bit selection is determined by the lowest cost per foot and is a function of bit cost and performance as well as penetration rate. Conventional optimum rock bit selection program involves development of computer programs created from mathematical models along with information from previously drilled wells in the same area. Based on the data gathered on a daily basis for each well drilled, the optimum drilling program may be modified and revised as unexpected problems arose. The approaches in this study uses the power of data mining algorithms to solve the optimum bit selection problem. In order to achieve this goal, adaptive neuro fuzzy inference system, K-nearest neighbors, decision tree, Bayesian classification theory and association rules were developed by training the models using real rock bit data for several wells in a carbonated field. The training of the basic models involved use of both gamma ray and sonic log data. After that the models were tested using various drilling scenarios in different lithologic units. It was observed that the adaptive neuro fuzzy inference system model has provided satisfactory results.
 
 

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Introduction
 Analysis of time, location and magnitude of foreshocks and aftershocks has been one of the most important cases for experts in various scientific fields such as: seismology, structural engineering and crisis management, and other interrelated fields. Since this analysis and the result of studies on seismotectonic and cases of earthquakes help us identify the foreshocks and aftershocks with the goal of decreasing losses and nervious stress of the injured community in quake-stricken areas and skilled crisis management. The cause fault of earthquake plays the important role in foreshocks and aftershocks of the earthquake. So, study on fault behaviour is a suitable method for analyzing and routing the basic parameters of foreshocks and aftershocks. Also, foreshocks and aftershock are important parts of any earthquake in a seismic area. The analysis of the basic parameters of the foreshocks is one of the most practical researches for reducing the risk of earthquakes. The identification of behavioral pattern of foreshocks can help researchers detect the active fault conditions for the occurrence of earthquakes in different areas. The present study is concerned with the study of behavioral patterns earthquakes, foreshocks, and aftershock of Zohan earthquake. Experience of large aftershocks in different parts of the world indicates that, following earthquakes and depending on seismic-tectonic conditions, large aftershocks are likely to occur in the earthquake-effected zone, which will aggravate the damage caused by earthquakes (Omi et al., 2013). The main factor contributing to the worsening of damage caused by aftershocks is the performance of structures that are weakened but not destroyed by main earthquakes and are, thus, highly likely to be destroyed by large aftershocks (Saket and Fatemi Aghda, 2006).
Material and methods
The present paper makes use of data collected in a real earthquake and similar expriences in other earthquakes for presenting a practical pattern for predicting primary earthquake patterns, determining the location, magnitude, and time of aftershocks. The target of this case is decreasing the effects of earthquake. To this end, we used the results from studies on basic parameters of foreshocks and aftershocks of Zohan earthquake, and 2012 earthquake in South Khorasan province. The rationale for selecting the aforementioned studies is: location of event, the Zohan earthquake, had been identificated as an area with high risk for the occurrence of earthquakes, although there has been no wide-scale earthquake in this area in the last two decades. These conditions are important causes for more concentrated studies on this area because there is a high chance for wide-scale earthquakes striking this area.
Result and Discussion
In this part of research, we conduct a study on the location, magnitude and depth of foeshocks. Some of the world-wide research suggested that these data can help to predict the time of  mainshocks. Studies conducted on the variations of frequency in foreshocks can follow this goal.
In this paper, the available statistical data such as periodical variations of seismicity in the weeks leading up to the main shock can be used as a tool for estimating the approximate time of a future important earthquake. The weekly variations of seismicity before Zohan earthquake indicate a relative increase and then decrease within a 100 km radius around the epicenter of the main shock.
 
Table 1: Variations of frequency of foreshock based magnitude before Zohan earthquake

Week before main shock	Frequency of foreshock in the Radius of 100Km from main shock	Frequency of foreshock(with M>2.5) in the Radius of 100Km from main shock
6	0	0
5	1	1
4	1	0
3	2	0
2	5	3
1	2	0

 
Studies on numerous earthquakes in Iran and other regions in the world show that the distribution of aftershocks can be related to fault type or the direction of principal stress (Saket and Fatemi Aghda, 2006) and (King et al., 1994). Whereas maximum Coulomb stress change is related to maximum principal stress in earthquakes, the concentration of aftershocks can coincide with the direction of maximum principal stress (σ₁) of the causative fault in mainshock. Considering the direction of maximum principal stress and its adaptation to the scattering of aftershocks, the above hypothesis is confirmed.
Also studies on frequency changes and seismic quiescence of small aftershocks help us in predicting future aftershocks. The results the of presented research by Itawa (2008) on the World earthquake catalogue suggest that seismic quiescence theory is true for different regions of the world. Based on the results of the  study mentioned above, this case can be used as a tool for predicting large aftershocks in Zohan earthquake.

Fig 1. Adaptation of direction of maximum principal stress with scatering of the aftershocks of Zohan earthquake. a: direction of maximum principal stress (σ₁) of the causative fault in mainshock. b- scaterring of the aftershocks
Table 2: Seismic sequience versus magnitude of aftershocks

Row	Seismic Quiescence for aftershocks	Aftershock Magnitude	Data and Time of aftershocks
1	13	3.0	2012/12/05 17:21:03
2	36	3.4	2012/12/05 17:57:03
3	161	3.1	2012/12/05 20:38:09
4	3906	3.9	2012/12/08 13:44:19

In addation, frequency of aftershocks and certain time distance (seismic quiescence) between their can use precursors for detecting the time of large aftershocks. The relevant analysis in this study showed that methods such as: time series beside seismic quiescence can help in conducting a more accurate time forecast of large aftershocks.
Conclusion

• The results of this research suggest that we can identify some of the charactristics of the main shock by focusing on location, magnitude and depth of foeshocks.
• In Zohan earthquake, the direction of maximum principal stress is adpated to the scattering of aftershocks, and this case suggests that there is a specific relationship between them.
• The relevant analysis in this study showed that the methods such as: time series beside seismic quiescence can help conduct a more accurate time forecast of large aftershocks../files/site1/files/144/saket.pdf

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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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Existence of sodium elements in fine-grained of some soils causes dispersive phenomenon in them.  Failure to accurately identify dispersive clays leads to damage because dispersive clay soil particles disperse under certain conditions and wash away quickly. This research assesses dispersive degree of outcropped soils in southeast of Yazd. Finally, the modification of soil dispersive potential was investigated by using nanocellulose.  After performing a series of physical, chemical and mechanical tests, characterization/ specification of the studied soils were determined. Then dispersive degree was specified by conducting chemical, pin hole, crumb and double hydrometer tests. Finally, soil dispersivity stabilization was performed using sample preparation with 0.5, 1 and 1.5% nanocellulose. The results showed that the studied soils have moderate dispersive in borehole A and extreme to slightly dispersive in borehole B. Therefore, it can be concluded that the closer we get to the center of the plain, the greater the dispersibility. The results of the dispersibility stabilization soil tests indicate that the optimum moisture content and dry specific gravity increases and decreases. Uniaxial strength and CBR increases. Also, it shows that the increase in nanocellulose has a positive effect on the modified samples and improves the soil dispersibility in this area../files/site1/files/152/%D8%B2%D8%A7%D8%B1%D8%B9.pdf
 

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Extended Abstract

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