نشریه مهندسی عمران و محیط زیست دانشگاه تبریز
سال پنجاهم شماره 2 (پیاپی 99، تابستان 1399)

Electrokinetics is one of the important methods for soil remediation. Due to workability of this method, it has widely being used for contaminant removal from fine grain soils. On the other hand, the presence of carbonate in clayey soils causes a reduction in the efficiency of electrokinetics method. On the fundamental of microstructural aspects of this method, there are only limited researches. Therefore, the main objective of this research is to investigate the impact of carbonate and carbonate elimination on the efficiency of Pb removal from carbonated kaolinite in electrokinetics process with special attention to the XRD analysis. In electrokinetics experiments, natural kaolinite samples were air dried and passed through number #10 sieve. Then, kaolinite samples were mixed in 1:10 soil: electrolyte ratio with 10 cmol/kg-soil lead nitrate. Samples were kept for a week to achieve equilibrium. Then, they were compacted on the electrokinetics cell in 5 layers with similar density of 1.7 g/cm3. Finally, the electrokinetics experiments were performed. At the end of electrokinetics experiments, soil sample was removed from cell and was sliced in 5 sections. Each section was dried separately and was analyzed by AA and XRD experiments. The results of this research show that for decarbonated kaolinite sample, a 162% increase in electrokinetics efficiency was observed. Base on the results of this research the efficiency of the electrokinetics method for heavy metal contaminant removal is a function of three factors which include heavy metal transformation towards cathode compartment, pH variations, and soil water content.

In this paper, the feasibility of using piles to stabilize layered and homogenous earth slopes were studied. A set of physical modeling of foundations was performed adjacent to homogenous and layered slopes. The deformation pattern and shear strains of soil near slope and below surcharge load were studied. The effect of pile and soft soil layer locations on improvement ratio (safety factor of stabilized slope with pile / safety factor of the slope stability without piles), soil element displacement, slope stability and slip surface shape in homogenous and layered slope were investigated. The experimental and numerical results show, existence of thin layer of soft soil layer, has considerable effects on failure mechanism and stability of slope. Based on research results, it was found, the optimum location of pile for increasing slope stability was in middle of slope the test results showed that, for layered slopes, optimum location of pile for increasing bearing capacity of foundation which is located on slope crest is near slope crest. For homogenous slope optimum location of pile for increasing foundation bearing capacity was found between middle of slope and crest. Comparing piled and no piled slopes, showed in piled slope slip surface depth below the surcharge load are larger than no piled slope. Studies on soft soil layer effects on slope stability shows; Existence of soft soil layer has significant effect on slope stability, and critical failure surface obviously controlled by soft bound layer.

Shallow footings are usually located above the ground water table and the soil under footings is in unsaturated condition. Therefore, the bearing capacity of Shallow footings should be influenced by the capillary stresses due to unsaturated soil conditions. In this research, the effect of soil unsaturation has been investigated on the bearing capacity of square and rectangular surface footings located on dense sand with different ground water table, in laboratory scale. The results of the experiments show that by lowering the ground water table and consequently by increasing the soil suction due to capillarity, by changing the matric suction from 0.5 to 4.5 kPa, the ultimate bearing capacity in unsaturated conditions increase nonlinearly 2.3 to 4.3 times the ultimate bearing capacity of the saturated condition. furthermore, at matric suction close to the residual suction and passing through the desaturation zone, the increasing rate of bearing capacity decreases and By increasing the length to width ratio of the footing, the increasing rate of bearing capacity increases.

Cavitation is one of the hydraulic phenomena that its occurrence caucus destroying the hydraulic structures. Chute spillway is an example of hydraulic structures that cavitation may be occurred. In this work, cavitation in chute spillway of Surk dam, which it have a rapidly change slope in chute path, has been studied using physical modeling. The physical model was made by plexiglass with scale of 1:50 and dynamic similarity between the model and the prototype was considered based on Froude number. The experiments were conducted in 5 different flow rates and pressure, velocity and flow depth were measured in the central axis and side of the wall. In this study, Falvey criterion (1990) was used for commenting of cavitation index. The results showed that the calculated cavitation index was in range of 0.25 to 1.8. In this range Falvey recommended to prevent the risk of cavitation, it is required the concrete surface of the chute spillway should be lining with a smooth materials.

One of the weakness of concentric braces is lower ductility and early buckling under compressive loading. One method to improve the ductility is to use energy-dissipater members situated at the intersection of the braces. Regarding this, the usage of steel rings made of steel pipes as an energy dissipater has been considered for solving weakness of ductility. Following this, the main objective of this study is to assess evaluate experimentally the dynamic behavior of steel ring filled with compressive plastic (S.R.P.) situated at the intersection of the braces. In addition, this connection was modeled by means of finite element (FE) method employing ABAQUS software. The accuracy of the FE models is confirmed using outputs of experimental studies where the nonlinear behavior of this connection was investigated both experimentally and numerically. Results indicate that the S.R.P. constructed from steel plates and plastic has a suitable performance relative to the pipe ring and exhibits good ductility and energy dissipation. In addition, this connection can enhance ductility of concentric braces in seismic loads. Concerning this matter, the brace with the S.R.P. ring shows a steady and wide hysteresis curve where tensile ductility factor of 2.77 was achieved. Another matter is that the maximum stress of this connection was obtained numerically in failure zone as indicated in experimental results. Furthermore, the maximum tensile load and corresponding vertical displacement were 99.48 kN, 16.01 mm, respectively, and also the maximum compressive load and corresponding vertical displacement were 101.55 kN and 11.5 mm, respectively.

Thermo-mechanical behavior of clays has been investigated in the past two decades because of increased interest in using clay as a buffer material in nuclear waste barriers. Many of researchers studied the thermo-mechanical behavior of clays to estimate their performance as buffers for nuclear waste containers [1-4].At present, sand-bentonite mixture is expected to be the most appropriate as a buffer material of high-level radioactive waste products when they are disposed in the deep ground resting place [5]. The dry density of pure clays can be as low as 1.3 Mg/m3 when compacted in situ; however, by mixing sand with the clay, the attainable dry density can be increased. Additions of sand can also be expected to decrease the creep potential of the material, increase the thermal conductivity and improve soil strength properties. Moreover, compacted clay-sand mixtures may possess lower hydraulic conductivities [6].The soil around nuclear waste repositories are subjected to elevated temperatures and their features change in long time. So response of the soil to coupled effect of pressure and temperature has been studied with more accuracy in last decades. This research tries to check the thermo-mechanical behavior of saturated sand-bentonite mixture in different temperatures and confining stresses during triaxial tests.

This paper carried out experimental investigation on the behavior of RC beams containing corroded reinforcement. Results from earlier studies demonstrate a consistent association between corrosion level of reinforcements and carrying capacity of beams under static loading test (Dong et al., 2011, Wang et al., 2015). So far, however, there has been little discussion about the simultaneous effect of stirrup spacing and corrosion level of reinforcements on crack patterns at failure and failure mode. Therefore, the main aim of this study is to investigate the behavior of corroded beams with different stirrups spacing in several corrosion levels. Evaluation of the corroded beams was carried out the crack pattern due to loading, residual ultimate strength, and the failure mode of the beams. 20 beams with different distances of stirrup were made and cured under lab conditions. all samples were under accelerated conditions until test time. the behavior of beams under failure load were measured and compared to each other.

In this paper, effects of torsional irregularity and seismic resistance level of structures with steel special moment resisting frame system, which were deigned based on valid codes, have been evaluated. Structures were 3, 6 and 9 story buildings and sites had high, average and low seismicity levels. Also, buildings had different levels of torsional irregularity. Buildings were selected in a manner that had equal seismic mass and base shear. Gravity and seismic loading were applied regarding ASCE 7-05 code and structures were designed in accordance with AISC 2010. In order to perform progressive collapse analysis, the nonlinear dynamic analysis procedure regarding GSA 2013 code was selected. Results show that buildings with greater torsional irregularity have higher strength against progressive collapse failure. Moreover, buildings in region with higher seismicity level have higher strength against progressive collapse failure. A damage index was defined that related to building height, seismicity level of site, and level of torsional irregularity.