Khorasan Razavi province is one of the areas with many chains of Qanat and Mashhad city in the center of this province has developed on areas with Qanat in the west direction. Loads caused by tall buildings and structures that built on old Qanats can make Qanats unstable and consequently Qanat collapse can lead to ground settlement. This paper deals with identifying the exact locations of Qanat chains by aerial photographs and evaluating the main factors that cause Qanat collapsing. Moreover the stability of Qanat was evaluated in numerical modeling by Plaxis Software. The geotechnical data, Qanat depth, Qanat lining system and vertical load was used in modeling and after that, the extension of plastic zone around the Qanat underground tunnel was analyzed. The results of this research show that the rate of plastic zone extension and the influence of lining in Qanat stability decreases by increasing in the Qanat depth. As it is estimated while Qanat depth increases as much as one meter, it can tolerate more pressure as much as loads induced by a one-storey building.

Modeling of Kaboodval Dam using Plaxis Software has been used for the Mouher-Columb behavior model. The effect of two continuities of embankment and watering operations on the meeting was considered. The body structure of the dam was increased from the side of the faces to the middle sections, and the maximum seating was recorded at 25-25 and at about 2200 mm. By examining at different intervals, the largest meeting was in the range of 180 to 185. That is, the level of the embankment was found to be critical in these numbers. Most concerns were regarding the middle of the dam, which had a weaker position. According to the analysis of different parts of Kaboudvall Dam, the materials forming the right wing of the dam in the middle and left wings of the dam were better. In the case of the 19th Module, besides the Mouher-Columb model, the dam could be modeled with hardening and hardening models. Here, the hardening model created a better fit. The hardening model, as it could get more data from the soil, is likely to better model the behavior of the soil dams. Due to the fact that, during the construction, the first sessions usually occur, the hardening model can have a better performance.

High ground watertable is one of the main problems that can disrupt the tunnel construction. The prediction of groundwater infiltration into the tunnel is very important subject for preventing problems during drilling and designing drainage system. Therefore, it is necessary to consider the amount of water flow and drainage model in the design, thus, it is necessary to forecast quantity of water flow and the drainage model and consider them in design stage. For this purpose, to present a dewatering design in the eastern part of Tehran Metro tunnel Line 7, the cross-section of 4+ 500 + 4 +600 Kilometers, two drainage galleries with a length of 14 meters were used. Modeling and estimating the entering water into the tunnel requires detailed and accurate information about soil hydrodynamic properties. Also, the accuracy of modeling and numerical analysis and comparison with actual conditions for optimization of the design is very important. One of the best methods for evaluating these parameters in ground mass scale is back analysis according to experimental results. Ground water infiltration into two galleries was calculated for the whole length of the tunnel in steady state, using from finite element and finite difference methods in Plaxis® and FLAC® Softwares. Then, from the data obtained from the Lefranc test, the value of the soil hydrodynamic parameters were estimated by the method of back analysis. The obtained results indicate the value of the method of return analysis compared to the Levfran method for measuring permeability with the same data. The measured value of groundwater infiltration in field tests was 600 cubic of meters per day and the error of the finite element and finite difference methods is equal to 12 and 4/8 percent, respectively, which are in a good agreement with the field measurements. The optimum value of permeability parameter obtained from back analysis equal to 4. 5  10-5 and 3. 6  10-5 meters per second was set for this area as well as optimum transmissivity equal to 117 and 214 meters per day.

One of the important parameters of soil properties for application in the Plaxis, to analyse the behavior of earth structures and their failure mechanisms, is shear modulus of elasticity. An intensive geotechnical survey, field and laboratory tests were executed to estimate the values of this parameter and other soil properties in the body of dike and polder. To determine this parameter, 9 different methods were used. Because of large differences among the given values, characteristic values for each layers of soil, were calculated by using a statistical procedure. Then, calibration of stresses and strains were used to verify the characteristic values and appropriate soil test. Both of the calibrations resulted in values more than characteristic values of shear modulus which were close together. The comparison of results of calibrations with foregoing methods showed that the characteristic values were not reliable because of the shortage of data and utilization of triaxial test to determine the shear modulus was better than others.

Incorrect designing of earth and rockfill dams with untrue safety factors causes internal scouring, downstream pitched roof submerged and break dam in torrential times. Breakage of earth and rockfill dams and also too much volume of torrential flow can destroy catchment areas and fen beds. Furthermore, correct designing of dams and obtaining suitable safety factors will prevent of these damages. In this study, first of all, series of geotechnical tests have been performed on the soil samples of the Chitgar earth dam to determine the soil strength parameters and material characteristics. The achieved parameters have been used as input parameters for Plaxis which is a finite element geometrical program for analysis of deformation and stability of soil structures. Based on different layers of foundation and dam body, four homogeneous and non-homogeneous models on coarse and fine foundations have been simulated and the results have been compared. These comparisons revealed that during construction of earth dams, which are situated on fine clay foundation, if the water level is high, there would be lots of pore water pressure which will cause the dam foundation to be destroyed. Therefore, dam must be constructed using step-by-step method so excess pore water pressure can have enough time to be lessened. The analysis, which carried out on non-homogeneous earth dams with clay cores, discovered that if dam construction is simultaneous with water filling, there would be high pore water pressure in the earth dam’s core which will reduce the safety factor of the dam. Therefore, it will be better if the non-homogeneous earth dams are filled after the construction period. Finally, sometimes in loose foundation, safety factor was found 1.45 for homogeneous dams in the stepped construction. The safety factor was estimated 1.14 non-homogeneous dams in the same conditions. Therefore, homogeneous dam can play better role than non-homogeneous dams in loose foundation.

Mass movements are complex phenomena. Recognizing the surface of rupture in landslides, is one of the most important prerequisites for studying the causes of instabilities and making the right decision for stabilization, which unfortunately faces a lot of uncertainty. The main object is to optimize the field study methods by combining stratigraphic studies, geotechnical and geoelectrical field surveys with the aim of determining the depth of the landslide surface with the lowest cost. This research was carried out in the Afsarabad village landslide in the west of Chaharmahal and Bakhtiari province and includes data collection and analysis of geological and stratigraphic features drilling and soil mechanics tests as well as geoelectrical surveys and the depth of rupture surface, has been extracted using geoelectric surveys with a dipole-dipole array and then compared with Software geotechnical analysis. The satety factor for the Afsarabad landslide was calculated using the finite element method (Plaxis Software) at different levels of underground water. Based on the obtained results, the slope is unstable, so that the safety coefficient in the dry and wet season is (0.77) and (0.6), respectively, and the depth of the rupture surface is 28 meters. Geoelectric surveys have shown an average depth of 25 meters for the rupture surface, which is in agreement with the Software analysis. Therefore, the geoelectric method with dipole-dipole array can replace a significant part of conventional drilling at a low cost.

One of the important parameters in design of coastal dykes is reinforcement of slope of body and base of dyke. In this paper, with pointing on two customary reinforcement methods of coastal dykes, the reinforcement of hendijan coastal dyke (with 40 kilometers length at Khozestan province) has investigated. In first method, geo-textile materials situated inside the slopes of dyke body horizontally. The length of geo-textile reinforcement materials and the spacing between layers have been investigated in more details. In second method, reinforce the dyke foundation by utilize a geo-textile layer over the foundation bed. In this method the effect of using reinforcement material in prevention the failure of dyke bed have been investigated. The results of these two methods has compared with each others. The First method is reinforcement by utilize geo-textile filaments in parallel layers in dyke body. The second method, utilize a layer of geo-textile in the bed of dyke. Presented analyzes simulated by Plaxis FEM model (Developed by Delft University of Netherlands). Utilized different material parameters have used as for available materials at project site in south coasts of Iran. In this paper, decrease of lateral slope of dyke as for suitable stability, is most cared. The results of analysis indicate better efficiency and economic profit by utilize a layer of geo-textile in the bed of dyke. Because of poor soil layer material in dyke bed layer, the results show that using reinforce material in bed has more effect in final strength and endurance of the dyke.