نشریه سد و نیروگاه برق آبی ایران
پیاپی 21 (تابستان 1398)

Soil nailing is a popular reinforcement method for stabilizing slopes, excavations, and retaining walls in many countries. The pullout capacity of the soil-nail interface is a critical parameter for the design and safety assessment of soil-nailed systems. In this paper, a three-dimensional (3D) finite element (FE) model is developed using the commercial program ABAQUS to simulate the pullout test of a soil nail in a soil-nail pullout box. The stress-strain behavior of the soil and soil-nail interface is described by a Mohr-coulomb model and coulomb friction model respectively. A novel temperature-based reduction of friction coefficient has been applied in order to reduce the roughness of soil-nail interface as the slip occurs. Validation of the FE model is carried out by comparing the results of numerical simulations with experimental data from a previous work. The comparisons between the modeling results and experimental data have demonstrated that the established FE model can simulate the pullout behavior of a soil nail in a soil mass properly. Based on this, the verified FE model has been used to investigate the effect of different nail diameters, soil elasticity moduli and pullout rates on the pullout behavior of the soil nail.

The design of relief wells includes determination of the distance of relief wells from each other, their distance from the dam upstream, the well diameter and discharge into each wells. This study tends to investigate these factors effect on uplift pressure in earth dams. For this purpose, finite elements method (FEM) was used for different configuration of relief wells in downstream of an earth dam. For validation, a comparison between analytical equation for simple condition and FEM showed good agreement for uplift pressure prediction. It was found that by increasing the diameter of pressure reducing wells, the seepage flow increases to each well. Reducing of the distance among relief wells or increasing of the wells diameters, resulted in uplift pressure reduction. Two-row arrangements of relief wells showed that zigzag type was superior than the non-zigzag type. Simple linear and nonlinear regression relations were presented for uplift pressure prediction with reasonable accuracy. For future researches, it is suggested to consider un-isotropic effect of soil

Gotvand olia dam is the highest embankment dam in Iran. this dam is the last dam  built on the Karun River before entering khuzestan plain in gotvand area.
the main worry of the analyst before the gotvand dam impoundment, has been the dissolution of the anbal salt in the reservoir of the dam and affected the karun water at the bottom of the dam. the aim of this study was checking the effects of gotvand dam impoundment on the water quality of karun river during the years 2001 to 2016 at the gotvand section. in this research, non-parametric tests of Mann-Kandal and Pettit were used to evaluate the trend and determine the break point and the SDI index was used to calculate the hydrological drought of time series. The results showed that in recent years the salinity of the karun river has increased. the main cause is the decrease of river flow from the water year 2007-2008 and continuation until now. Therefore, increasing salinity of the karun river has started three years before the dam impoundment. As a result, the dam impoundment has not changed the quality of water in the gotvand regulatory dam.

Morning Glory Spillways are an important type of flood evacuation systems. According to the specific hydraulic and structural conditions, the evaluation of the seismic behavior of these kinds of spillways could be more precise with considering the interaction of the solid-water-foundation system. In this research, a three dimensional modeling of the morning glory spillway was conducted, considering the reservoir, foundation and overflow tunnel system interactions. The analysis was performed with finite element method using ANSYS.16 software, in order to evaluate the effects of system components interaction on dynamic responses of spillway. ​To determine the effect of shaft geometry on the responses, Tabas earthquake accelerations in three directions applied on seven models with four different values for elevation and four different values of shaft diameter. Also displacements of spillway crest and principal stresses of the node connecting knee into the tunnel were extracted. Frequency Analysis shows that, the increase of the shaft height reduces the system frequencies, but the shaft diameter is not an effective parameter on the frequency of the system. Also the increase of the vertical shaft height, led to the maximum values of the vertical displacement of spillway crest and increase of principal stresses of the knee.

One of the main problems commonly encountered by the intakes of the power plants is the formation of vortex and turbulent flow at the intake of the reservoirs.Using the image processing method by using the PTV technique in a survey flow hydraulic of a horizontal intake with a trashrack by certain opening,under the submergence depths and different flow rates and comparing it with intakes without trashrack is the subject This paper addresses this issue.The used Trashrack has an opening percentage of about 64%, and these experiments were carried out on 6 Froude Number of 0.6,0.8, 1,1.2,1.4 and 1/6 and 5 ratios of the depth of submergence to intake diameter 1,1.5, 2,2.5 and 3.It should be noted that the diameter of the intake is 16 cm in the form of bell-shaped lips up to 21 centimeters.According to the results the best trashrack performance has been achieved in reducing the vortex strength in the 1 Froude number.On this Froude number,on average,about 56% of the vortex power reduction has been achieved by installing the trashrack.In general,it can be said that the greatest effect of the trashrack on the relative depths submergence is 2 and 1.5 and the Froude numbers are 1 and 1.4.

Increasing the pore water pressure in the body of dams will reduce the effective stress and thus reduce the shear strength of the body materials of the dam, which can lead to dangerous results and cause instability of earth dams. According to nonlinear behavior of earth dam, behavioral models of Mohr–Coulomb and hardening soil model are used to model the dam and body materials. In this study, using Plaxis and Geostudio finite element software, the results of instrumentation of the pore water pressure of the foundation and the core of the Sivand earth dam were calculated after the first dewatering period and compared with the results of the observational data. The study of hydraulic gradient variations and pore water pressure in Sivand dam showed that suitable permeability material was used in the construction of the dam. In addition, the results of evaluation of models with instrumentation data based on the root of the error and the relative standard error of more than 86 percent of the conformance show that the proper performance of the clay core and the cut off wall is due to changes in reservoir water level.

In recent years, a new type of dams namely CMD, has attracted so much attention. Different amounts of cement cause a type of behavior that be somewhere between those of embankment dams and conventional concrete dams. This behavior is not perfectly clarified and its analysis, especially under dynamical loading and in nonlinear region of the material, remains unclear. In this paper, Tobetsu dam has been choose for a case study and, by exerting seismic acceleration with different levels of maximum acceleration and using plasticity approach on concrete destruction in Abacus software, put to nonlinear dynamical analysis. The results show that in these dams cracking starts from the heels, and by increasing the exerted seismic acceleration most of the cracks take place at the dam's lowest third from foundation level on its upper- and lower-hand surface. This dam, due to high plasticity of its material, does not show fragile behavior and as exerted seismic acceleration increases, the dam's behavior remains soft so it does not suffer sudden wreck and does not lose the ability to preserve its own stability.