نشریه سد و نیروگاه برق آبی ایران
پیاپی 32 (بهار 1401)

In this study, using Modis images and wets pass model, the value of evapotranspiration for the northern Karun basin was estimated monthly from 2000 to 2014. The value of correlation coefficient for the obtained evaporations was R2 = 0.72. This model was calibrated and verified for different regions with different parameters. Data from 2000 to 2009 were used for calibration and data from 2010 to 2014 were used for validation of the model. The value calculated 0.54. In this study, with a review of climatic parameters of temperature, precipitation, evaporation during the period before the dam construction and after that, the effects on the microclimate of the area is investigated. Finally, to study the changes caused arising from the creation of a dam on the amount of evapotranspiration using the monthly images of Modis during the studied statistical period, the classification of images was done and the amount of changes were calculated. The results showed that the amount of evapotranspiration in the basin after the construction increased and its changes with distance from the dam in some months also has been increased.

In this laboratory research, a mixing plan was made of ordinary concrete containing Portland cement type 2 with a grade of 500 kg / m3. Compressive strength, tensile strength and modulus of elasticity tests of concrete were performed on concrete samples at 90 days of processing age at 21 °C and 600 ° C. In order to further evaluate and validate the results, SEM and XRD tests were performed on concrete samples at 90 days of processing age. Application of heat in concrete samples caused a decrease in test results in this study. In this regard, in the concrete compressive strength test, the strength decreased from 64.92 to 37.45 MPa, which included a decrease of 42.31%. In the concrete tensile strength test, the strength decreased from 5.22 to 2.27 MPa, which included a decrease of 56.51%, and in the concrete modulus of elasticity test, the modulus of elasticity decreased from 33.73 to 12.24 gPa Which decreased by 63.71 percent. The results of SEM and XRD tests at 21 °C and high temperature, while coordinating with each other, overlapped with the results of other tests in this article.

In this paper, copulas and Archimediean copulas (especially with hyperbolic generator) are investigated and it is shown how to use this type of functions in the stochastic frontier analysis. Then we study the efficiency of hydropower plants located on prominent dams in Iran, and based on their performance in 1399 we use data envelopment analysis and stochastic frontier analysis and copulas functions to rank them. In the present study, among the 58 mentioned dams, the dams with an average practical production capacity of at least 10 MW are evaluated. The number of these dams is 29. The calculations show that Gotvand Dam is in the first place and the Mulla Sadra dam has the last rank.

The study of seismic behavior of concrete dams has been considered by many researchers due to the importance of dam safety during earthquakes. Because the destruction of these structures by earthquakes can have adverse economic and social effects. On the other hand, predicting the behavior of concrete dams during an earthquake is one of the most complex and difficult issues in structural dynamics. In the present study, the effects of compressive force (uplift) and its distribution as a variable on the nonlinear dynamic response of a weighted concrete dam under earthquakes near and far from the fault have been studied using a numerical model. The results showed that the waves generated by the earthquake in the reservoir of the dam prevent the return of the dam to the reservoir and at the same time help to move downstream of the dam, therefore the lateral displacement of the dam is generally inclined downstream. The results also showed that the cavity water pressure fluctuates very strongly during the earthquake but with a small amplitude, therefore it has little effect on lateral and vertical displacements of the structure.

Considering the high seismic potential in most parts of Iran, the importance of studying the behavior of earth dams under earthquake loading, especially in the southern regions, is very important due to the number of these dams and seismicity of the Zagros mountain range. In recent years, many studies have been performed on the effects of earthquakes on earth dams, but these structures exhibit seismic response and different dynamic behavior in earthquakes under different geometric conditions and properties of different materials.In this study, the Shamil earth dam located in Hormozgan province has been investigated due to the importance of its application by means of numerical methods using the critical linear equation method. Dynamic behavior and seismic response of the dam and its following in terms of strains, tensions, acceleration and displacement distribution have been studied and the areas which susceptible to fracture were identified based on the relevant criteria. The results show that the upper part of the dam has a potential to crack and the maximum displacement is very small and occurred in less than one percent of the height of the dam, which indicates the stability of the dam during and after earthquakes.

In some situations, dams need to be built on non-rock alluvial grounds such as sand and sand-silt deposits. Therefore, undrained behavior and strength of silty sands are of great importance. One of the critical factors in studying the behavior of sand-silt mixtures is inherent anisotropy, a natural soil characteristic that depends on its texture and is independent of the soil's initial stress state. This type of anisotropy causes the soil behaves differently under the rotation of the principal stress angle concerning the vertical direction. In this study, the effect of inherent anisotropy is studied in sand-silt mixtures using triaxial compression and extension tests. The results show that adding 30 percent of silt to the sand significantly reduces the effect of inherent anisotropy. However, adding more silt increases the inherent anisotropy effect again. Furthermore, the dilative and contractive specimen behaviors at different silt contents and their peak strength values differ in compression and extension tests. The peak strength in pure silt is larger than in specimens containing 50 and 70 percent of silt.

Dynamic cone penetration (DCP) test is used more in pavement design and construction, and less for subsurface geotechnical investigation and clay core dam. In the present article, evaluating geotechnical parameters of Sanandaj’s clay in the western region of Iran using the DCP test was taken into account. Accordingly, 6 trial pits with maximum depths of 15 m were excavated manually in various sites of Sanandaj on clay soils (CL). During the excavation process, 3 series of DCP tests were carried out and repeated in the pits after excavating every one meter. The soil samples for the selected sites were also obtained for the laboratory tests including water content, grain size, Atterberg limits, and triaxial compression tests. Based on the results of the experiments, the DCP test was repeatable (CoV<30%). The relationships between Dynamic Penetration Index (DPI), liquid index (LI), undrained shear strength (Cu) and dry density (gd) of the clay soil were also obtained with a high coefficient of determination (R2>83%). Using the DCP test, geotechnical properties of the clay (CL) can be investigated rapidly and inexpensively