JOURNAL OF ENGINEERING GEOLOGY
Year:2020 | Volume:14 | Issue:2|Papers Count:7

Introduction: Rock masses have an enormous geometrical discontinuities such as void, notch, crack and flaw. These geometrical discontinuities which play as stress concentrator, cause to reduce the load bearing capacity of rock masses. In rock masses, the crack is the most important geometrical discontinuity assessed frequently by civil, mechanical and mining engineers and researcher. The fracture mechanics which is a branch of mechanical engineering science, has been often used for investigating the cracked rock samples. The fracture toughness is one of the important parameters in the fracture mechanics which describes the resistance of materials against the crack growth. On the other hand, since orientation of cracks relative to the loading directions can be arbitrary, brittle fracture in rocks may happen due to a combination of two major fracture modes, i. e. crack opening mode (mode I) and crack sliding mode without any opening or closing the crack flanks (mode II). In order to obtain the fracture toughness of rocks, several test configurations under pure mode I have been proposed...

Introduction: Soil dynamic properties are used to evaluate the dynamic response of soils at different strain levels in geotechnical engineering. The shear modulus (G) and damping ratio (D) are among the most important dynamic properties of soils. In general, the factors affecting the dynamic behavior of soils are divided into two categories: first; soil type and characteristics such as water content, void ratio and soil plasticity and second; parameters of loads applied on the soil such as the number of loading cycles, loading frequency and loading waveform. Therefore, it is widely believed that the dynamic response of soils partially depends on the characteristics of the load. In this paper, 1-g shaking table tests were employed to investigate the effect of loading waveform and frequency content on dynamic properties of dry sands. The response obtained from soil samples during loading with different frequencies, input accelerations and waveforms were used to generate hysteresis loops of tested samples at different strain amplitudes. Then, hysteresis loops were used to determine the damping ratio and shear modulus at different strain levels. Finally, the effects of loading frequency and waveform on the changes of each parameter (G and D) were investigated. Material and methods: A hydraulic shaking table with a single degree of freedom, designed and constructed at the Crisis Management Center of Urmia University, was used to conduct the experiments. Firoozkuh No. 161 sand was used in all the experiments. The Firoozkuh sand gradation curve is similar to that of Toyoura sand. In this study, accelerometers were used to measure the acceleration of the input to the sample as well as to record the acceleration caused by the input excitation at different depths of the soil sample. The displacement transducers (LVDT sensors) were also used to measure linear displacement. Each soil sample was constructed using dry Firoozkuh sand poured uniformly into the container from four equal heights of 150 mm to reach a total height of 600 mm. During the compaction process, the accelerometers A1, A2, and A3 were placed at a depth of 150, 300 and 450 mm with respect to the bottom of container. Also, one accelerometer, A0, was attached rigidly to the container base to measure base acceleration. A displacement transducer (L1) was placed on the soil surface at a height of 600 mm from the floor of the container to measure the vertical displacement of the surface of the soil. In this study, 42 shaking table tests were performed to study the effect of loading frequency and waveform on dynamic properties of dry sand. The test samples were subjected to rectangular, sinusoidal and triangular loading at frequencies of 0. 5 to 9 Hz and at input acceleration of 0. 1g and 0. 3 g. Results and discussion: Given the importance of G-γ and D-γ curves in dynamic analyses, the changes in shear modulus with shear strain has been studied. The results show that the shear modulus increases as the frequency increases in all cases, and this increase is observed at lower frequencies and increases with increasing frequency. On the other hand, the shear modulus decreases with increasing shear strain. At a constant testing frequency, soil samples subjected to the rectangular waveform exhibited the largest shear modulus while the samples subjected to the triangular waveform showed the least shear modulus. The shear modulus of the samples under the sinusoidal waveform is barely more than the shear modulus of samples under triangular waveform. Moreover, by increasing the shear strain, the shear modulus values of samples with different waveforms have become closer and the waveform effect is reduced. As for the effect of input acceleration on the shear modulus, increasing the input acceleration increases the shear strain and consequently, decreases the shear modulus in all states (the values of shear modulus in various frequencies and the waveforms under the input acceleration of 0. 1 g are larger than the shear modulus values under the input acceleration of 0. 3g). In the case of the damping ratio, the results show that, in all cases, damping ratio increases with shear strain. At low strain levels, the damping ratio values at various frequencies and waveforms are low and yet very close. At higher strain levels, the increase in frequency increases the damping ratio. This increase is more significant at higher frequencies. Also, the effect of waveform on the damping ratio is more apparent at larger shear strains, and at such shear strain levels, soil samples under rectangular loading exhibit the largest damping ratio. The damping ratio associated with the sinusoidal and triangular loading are also close to each other and it is a slightly larger for sinusoidal loading. On the other hand, the damping ratio increases with input acceleration. In addition, the effect of increased input acceleration on the increase in the damping ratio is more obvious at higher frequencies mainly due to the increase in shear strain. Conclusion: In the present study, the effects of loading frequency and waveform on the dynamic properties of dry sand were investigated using shaking table tests. The following conclusions were drawn: The shear modulus increases with frequency. The trend is more obvious at larger frequencies. The effect of loading frequency on the damping ratio of the soil at low levels of strain is negligible, and at relatively large strain levels, damping ratio increases with loading frequency. Soil samples exhibit the highest shear modulus and damping ratio under rectangular loading. Therefore, in all the tested frequencies and input accelerations, the values of G and D for the rectangular waveforms are greater than those of the sinusoidal and triangular waveforms. The shear modulus and damping ratio for the sinusoidal waveforms are marginally greater than those of triangular waveforms, yet one can consider them practically similar. In all cases, the shear strain increased by increasing the amplitude of the input acceleration, and as a result, the shear modulus decreased and the damping ratio increased.

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%.

Introduction: The discussion of modeling the interaction of soil-pile groups due to a large number of parameters involved is one of the complex topics and it has been one of the interests to researchers in recent years and has been dealt with in various approaches. In recent years, the artificial neural network method has been used in many issues related to geotechnical engineering, including piles. In this study, firstly it was tried to explain the importance of soil-structure interaction in calculating the dynamic response of bridges. Then, the effect of different effective parameters in calculating the interaction stiffness of the pile-soil group using artificial neural network was studied. For this purpose, Sadr Bridge (the intersection of Modarress and Kaveh Boulevard as a case study due to the presence of tallest piers ) in the transverse direction, with and without considering the effect of soil-structure interaction was analyzed. The analysis was carried out in which the substructure soil was replaced with a set of springs and dashpots along the piles. Considering the fact that many factors are involved in determining the equivalent stiffness of springs, in the second stage, the effect of different factors on the stiffness of spring equations using artificial neural network was investigated. Finally, the artificial neural network method was used as a suitable method in order to estimate the equivalent stiffness values, the equivalent stiffness of the pile-soil group was introduced for different input values. Equivalent stiffness of the substructure soil using the artificial neural network, has not been used by researchers yet, so estimation of the optimal length and diameter of piles used in constructions and estimation of the seismic performance of the bridge system during its operation could be effective. Material and methods: In this paper, spring-dashpot method is proposed to the non-uniform analysis of single-pier bridges which led to a 5-degree freedom model in the case of Sadr bridge. This study is also focused on the SSI effect in dynamic analysis of bridges. This method is based on the traditional spring-dashpot method but in this method, non-linear stiffness is used along the piles, instead of linear stiffness and upgraded shape functions and coefficients are applied to make more precise mass, stiffness and damping matrices. Then the seismic responses of Sadr bridge are compared in different conditions including or excluding the SSI effects. In the present study in order to calculate the stiffness of the soil-pile group at depth, due to the effect of soil-structure interaction, the recommended method by API is used. The study of neural network analysis was used and the effect of different parameters used to determine the complexity of the soil-pile group system has been evaluated. The multi-layer feeder network, which has the most application in engineering problems, has an input layer, an output layer and one or more layers of hidden content, has been used for this purpose. The appropriate model of the neural network with a topology of 1-20-6 was provided using the hyperbolic sigmoid activation function, and the Levenberg Marquardt model and the training cycle 84, which had the least error mean square and the best regression coefficient. The effect of internal friction angle, soil density, pile diameter and the resistance per unit length has been evaluated with this method. Results and discussion: In this study, the importance of considering the effect of soil-structure interaction on the dynamic response of the Sadr bridge was studied. Dynamic stiffness of the soil around the pile group was calculated based on the equivalent linear method and using the p-y springs. Therefore, the effect of substructure soil was considered in dynamic analysis of the system. The artificial neural network was used to predict the stiffness of the soil-pile group, based on various input parameters and the stiffness sensitivity analysis of the calculated output values was conducted. In hard soils, the stiffness of the pile-soil group increases with increasing the diameter of the pile in the range of 1 to 1. 5 m. However, in the range of 0. 5 to 1 m of diameter, the diameter of the pile does not have much effect on the stiffness of the system and also stiffness decreases in the range of 1. 5 to 2 m in diameter by increasing the pile diameter. Soil specific weight and angle of internal friction can change the system stiffness but the effect of the soil specific density is much greater on the stiffness of the soil-pile group system. Generally, the specific density in the range of 1000 to 2300 kg/m3 will increase the stiffness of the system. In general, the ultimate strength of the soil between100 to 550 (kN/m) affects the system stiffness. This effect within the ultimate strength between 100 and 220 (kN/m) causes an increase in the interaction stiffness value of the system and in the range of 220 to 550 (kN/m) yields to reduce the stiffness of the system. The ultimate strength values in a unit of length outside of the above range have little effect on the system interference stiffness. Despite the fact that the problem of calculating the soil-pile interaction stiffness is a direct solution, the use of the proposed neural network model can help in predicting optimal values of diameter and length of the pile to achieve maximum soil-pile stiffness and especially for long bridges it will have a significant impact on reducing cost and seismic design of the bridge. Conclusion: The results of this study are as follows: The results showed that considering the interaction effect, although it increases the relative displacement of the deck, reduces the maximum base shear and moment. This suggests that considering the maximum base shear and moment in the interaction conditions may not lead to a seismic design for certainty, although closer to reality. Artificial neural network is an efficient way and new method to predict the stiffness of the soil-pile group system based on different input values that have not been used yet. Such that with the physical and mechanical properties of the soil as well as the geometric properties of the piles, it is possible to predict the interaction stiffness values with the proper precision. According to the results and diagrams obtained from the neural network model, which are mainly sinusoidal, the optimal values of the interaction stiffness can be obtained by obtaining the pile diameter, specific gravity, the internal soil friction soil to achieve optimal interaction strength. It is also possible for each site to estimate the depth of the piles in order to achieve optimal hardness.

Introduction: Solid waste is one of the unavoidable products of every society that necessitates the establishment of municipal solid waste management system. Because of variability in quantity and composition of municipal solid wastes, several management scenarios are considered. Assessing the environmental impacts of the life cycle of these scenarios will have a significant role in reducing and resolving urban service management problems. The aim of this study was to compare different scenarios of municipal solid waste management in Sirjan city using life cycle assessment (LCA) approach. LCA methodology is used to evaluate the environmental performance of the waste management of Sirjan for different scenarios, according to the ISO standards 14040 series 2006...

Introduction: Landslide is known as one of major natural hazards. Landslide susceptibility mapping is known as efficient approach to mitigate the future hazard and reduce the impact of landslide hazards. The main objective of this research is to apply GIS spatial decision making systems for landslide hazard mapping in the 5th segment of Ardebil-Mianeh railroad. Evaluation of the landslide criteria mapping and their relevancy for landslide hazard can be also considered. To achieve the research objectives, an integrated approach of Fuzzy-Analytic Hierarchy Process (AHP), Fooler Hierarchical Triangle and Fuzzy logic methods were employed in GIS Environment. Material and methods: Within this research, we also aimed to apply GIS spatial decision making systems and in particular GIS multi criteria decision analysis which are available in Arc GIS and Idrisi softwares. We have identified 8 casual factors (including: density of vegetation, land use, faults desistance, distance from rivers, distance from roads, slope, aspect, geology) based on literature review. Accordingly, these layers were prepared in GIS dataset by means of applying all GIS ready, editing and topology steps. The criterion weighting was established based F-AHP approach. The criteria weights was derived and rank of each criterion was obtained. Accordingly, the landslide susceptible zones were identified using GIS-MCDA approaches. Results and discussion: Finally the functionality of each method was validated against known landslide locations. This step was applied to identify most efficient method for landslide mapping. According to the results and based on the values derived from Qs, P, and AUC, the accuracy of fuzzy method was accordingly about 0. 33, 0. 74 and 0. 76, respectively. In context of Fuzz-AHP the accuracy of 1. 08, 0. 88 and 0. 94 were obtained. While, the accuracy of Fooler Hierarchical Triangle were obtained 0. 78, 0. 84 and 0. 91, accordingly. Conclusion: As results indicated integration of Fuzzy-AHP represented more accurate results. Results of this research are great of important for future research in context of methodological issues for GIScience by means of identifying most efficient methods and techniques for variety of applications such landslide mapping, suitability assessment, site selection and in all for any GIS-MCDA application.

Introduction: The use of various additives to improve the properties of soils from past years have been studied by different researchers. Such additives are lime, cement, fly ash and fiber which have been used frequently in combination with soil. Lime is one of the oldest additives that it is utilized with different types of soils. Lime has positive impact on geotechnical properties of soil that alter some of the soil characteristics. Adding lime causes to reduce plasticity ranges, enhanced efficiency, strength and shrinkage of the soil. Extensive researches in the field of sustainability of clay with lime indicate that the optimum percentage of lime in the soil modification is between 1 to 3% by weight of the soil. But some researchers believe 8% by weight of lime are effective for soil stabilization. The presence of lime in clay soil yiels to occur some reaction, that it improves the soil properties. Reactions are included cation exchange flocculation, carbonation and pozzolanic reactions. Cation exchange between the clay cations and calcium cations takes place in lime. Cation exchange causes clay particles to get closer to each other creating complex structures in the clay soil and this improves the clay soil features. In recent years the use of nanoparticles is considered in civil engineering field. The investigations have demonstrated that the use of nanomaterial increases cement reactivity and also improves density because it is filled with particles. Recent research has shown that the use of montmorillonite nano-clay soils to control swelling and to reduce failure potential in the soil. A number of researchers have expressed the use of nanoparticles causes to decrease the hydraulic conductivity of soils. In this paper, the effect of nano-clay and lime on the important soil parameters is evaluated. For this purpose, lime at 2 and 4 percentage and nano-clay at 0. 5, 1 and 2 percentages have been added to clay soil and their impact on parameters such as optimized moisture, Atterberg limits, unconfined compressive strength and self-healing properties of soil is evaluated. Self-healing properties is one of the features, to repair damages due to internal erosion in the clay which is very efficient and important. Materials and experimental methods: In the present research, the effect of lime and montmorillonite nano– clay to soil strength is evaluated. For this purpose, samples of clay soil (CL) has been used. In the experimental study, the percentages of additives mixed with the dry soil and then the optimum moisture and maximum specific weight of soil are determined with different percentages of additives. Soil Atterberg limits based on the ASTM D4318 standard have been determined. Dry samples have been mixed together and then the water is added and mixed well with each other. Then the sample has been prepared in the form of a steel cylinder (cylindrical specimens) with a diameter of 50 mm and a height of 100 mm. Specimens were molded immediately and the weight and dimensions were carefully measured and then placed in plastic to prevent moisture loss and put them at 20 ° c and 90% moisture curing room. Results and discussion: In this study, the percentage of lime is between 0, 2, 4 percent by weight and nanomaterials percentage is between 0. 5 and 1 and 2 percent that can be varied in order to analyze the effect of various additives on the properties of the soil samples. The results indicate that increasing the nano-clay and lime percentage can enhance the optimum specific gravity of soil. The optimum moisture content of sample without any additive is equal to 19. 5%. However, samples contain 2% nano-clay and 4% lime, the optimum moisture content increases to 23. 5%. But the presence of lime reduces the maximum dry density of soil while adding nano-clay increases this amount. In samples with 4% lime and with no nano-clay, maximum dry density is 17 but in case of lime with 4% and nano-clay with 2% it is increased to 17. 5. In addition, adding lime without the presence of nano-clay only increases strength of soil. When 2 percent of lime is added, the strength of soil increases about 39 percent. As mentioned before, the effect of lime and nano-clay on increasing of unconfined compressive strength is almost the same which means by adding 2% of lime or nano-clay the strength of the soil increases about 40 percent. Using both lime and clay nanoparticles simultaneously (each 2%), a significant increase in strength of soil occurs in approximately 77 percent. Conclusion: The use of nano-clay and lime improves soil strength parameters. But economically lime is more affordable than nano-clay. Therefore, if you need to increase only unconfined compressive strength, then the nano-clay is not recommended. When it comes to self-healing in clay, the nano-clay can improve resistance rupture of the soil. By adding 2% of nano-clay in soil, healing of soil resistance after the break and after 24 hours can reach up to 60% of the ultimate strength of the soil. This property can be used to repair of locations that are subjected to internal erosion and scouring.