جستجوی مقالات مرتبط با کلیدواژه « پایداری شیروانی » در نشریات گروه « عمران »

This paper demonstrates the use of the response surface method (RSM) to carry out probabilistic assessment of the bearing capacity of shallow footings seated near naturally occurring heterogeneous slopes. The method substantially reduces the number of Monte Carlo simulations required to carry out cumbersome probabilistic slope stability analyses. A finite element limit analysis model based on the lower bound theorem is developed. The soil behaviour in this model has been assumed to follow the associated plastic flow rule by conforming to the perfectly plastic Mohr-Coulomb failure criterion. The model then used to generate a large synthetic database of numerical results for the bearing capacity of shallow foundations resting on inherently variable natural slopes. To this end, a permutation of the key parameters is formed and lower bound FELA-based limit loads are sought through optimization in MATLAB. A closed-form solution is formulated using RSM-based polynomials. The response surface method equations, which are acquired from least squares regression analyses, are used to carry out probabilistic Monte Carlo simulations. The results of the current study clearly show that the earth slope angle of 75o would give rise to the diminished factor of safety, or in other words, the substantially augmented probability of failure compared to the other two slope angles considered. On the other hand, the slope angle of 45o renders higher factor of safety and lower probability failure as compared to the slope angle of 60o. Moreover, it is observed that constructing the foundation at a farther distance relative to the slope would cause the probability of failure to substantially diminish while leading the reliability index to enhance for the majority of the safety factor scenarios considered. Indeed, targeting a particular probability of failure or a specific reliability index would demand smaller factor of safety for greater soil-footing distances.

in the present study, the slope stability coefficient of Namrood dam as a case study was calculated for different load conditions, including permanent leakage and completion of construction by using deteministic and probabilistic methods. Geo-studio software package and Monte Carlo simulation techniques were used for analysis. The effect of earthquake load on the stability of the dam structure was also investigated. The results showed that in the present conditions of the dam, the failure probability of the critical sections of Namrood dam was negligible, so that the maximum probability of failure was calculated as 0.00007. Then, sensitivity analysis were carried out on the value and type of distribution of effective input parameters. Results showed that with the increase in the earthquake load by 15%, the probability of dam failure increased by about 100%. The results also showed that the type of effective parameters distributions including cohesion of soil (c), soil friction angle (φ) and unit weight (γ) have little effect on the probability of dam failure.

Nowadays, with increasing population and the severe shortage of space, the general preference is to construct buildings with deep and semi-deep excavations. However, changing the material from a soil to the rock, the stability conditions and its analysis are noticeably affected. In a rock slopes, there are weak levels with different direction and density which form different patterns of failure. In this paper, the case study on the static and dynamic stability of the rock slope caused by excavation up to the depth of 15meters have been investigated with considering the structural anisotropy effects due to the presence of stone joints, blocks and the pore water pressure.The main challenge is the existence of rocky jointed materials with water seepage through them. In order to collect data for some single joints, the structural geology analysis has been carried out by using the Streo net grid strategy in DIPS and statistical software. Finally, static, dynamic and hydrostatic analysis has performed using UDEC software based on discrete element method. The results show that the rock slope in the static and dynamic state of stability has been unstable due to the application of hydraulic flow.

One of the important issues in the slope stabilization especially in urban spaces, roads etc. is the technical, economic, environmental and space constraints, which impose particular conditions on any project. Undoubtedly, seismic evaluation is one of the most important issues in this field, and the study of dynamic stability and reinforcement of slopes against earthquake hazards can prevent many mortal and financial losses. In this paper, the stability of the slopes in the northwest of Tehran located at the Islamic Azad University Science and Research Branch, which is adjacent to access roads and structures, has been investigated in static and dynamic conditions using the ABAQUS software based on finite element method. In addition, by using four methods of stabilization including soil nailing, anchor, reinforced retaining wall with geogrid and gabion, the slope stability has been analyzed by investigating and comparing the coefficient of safety factor and reliability, deformation and failure mechanism and also, the economic analysis of construction in two cases without and with stabilization. Based on the obtained results, it can be concluded that in addition to the soil resistance parameters, slope geometry and stabilization method have a significant role in the dynamic responses and among the technically and economically investigated methods, the stabilization using reinforced retaining wall with geogrid, increases the reliability and safety factor and provides sufficient sustainability which led to reasonable execution costs.

Various techniques have been adopted to enhance the stability of embankments constructed over soft soils. One of the most appropriate methods for this purpose is the application of stone columns. In this study, nite element analyses were carried out using PLAXIS 2D to consider the stability of sandy embankments over a soft clay bed reinforced with stone columns. To estimate the factor of safety (FS) against the deep-seated failure of the embankments, both common approaches of equivalent strip and equivalent area methods were used as a comparative investigation. The numerical analyses were focused on the eects of parameters on embankment stability, such as the diameter as well as the spacing of stone columns, the friction angle of the stone columns, the cohesion of the clay bed, slope height and friction angle. The analyses results show that the enhancement values of the embankment safety factor, due to an increase in the stone friction angle and the cohesive strength of the clay, were more pronounced in comparison to the effects of other parameters. Thus, an increase of 12kPa in the cohesive strength of the clay bed caused 34.2% and 15.8% enhancement in the safety factor of the embankment, respectively, through the equivalent strip and area methods. As modeling equivalent strips is a tedious task, especially when the number of columns is high, geotechnical designers prefer to use the equivalent area method. Hence, a reduction factor was proposed here to apply to the safety factor of the equivalent area method. The analyses results show that the reduction factor varies between 0.74 and 0.99. The FS values obtained from the equivalent area method may be adjusted using such reduction factors.

1. Soil slope stability depends on different parameters such as layers geometry, types of layers, layers condition (saturated, wet or dry), underground water level, static and seismic loads and also many other parameters. There are many solutions to stabilize the soil slopes; e.g. nailing method, using drainage, changing the slope’s geometry, and using a retaining wall. One of the newest methods is using geosynthetics. In this research, geo-fabric is used to stabilize the soil slope and the static and pseudo slope stability analyses are performed. Since the tensile strength of soil is not usually acceptable, geo-fabric can increase the tensile strength of soil and hence the safety factor of slope stability increases. Low and Tang developed a limit equilibrium method for the analysis of soft soil slope stability [1]. Ghazavi and Amel Sakhi used the 30*30 direct shear tests to evaluate the internal soil-rubber friction angle [2]. 2. Experimental study:In this research, the Geo-Slope software is used for soil slope stability analyses. Different pseudo static earthquake factors are selected. Slope’s height is 15 m constant, the slopes are 1V:1.75H, and the foundation’s depth is 3 m. There are two different layers in foundation, soft and stiff, and their combinations are varied in different analyses. The analyses are static and pseudo static. The slope and its foundation are analyzed in dry condition, so the water table level is ignored in this research. The Mohr-Coulomb model is used in all static and pseudo analyses.3. Results and discussion3.1. Static numerical In Fig.1, an example of static analysis results are presented. In Fig.2, the result is concerned with the soft layer on top of the stiff layer in foundation. It can be seen that the safety factor increases as the number of geo-fabric layers increases. The obtained results show that the Janbu method gives the minimum safety factors in comparison with other slope stability methods used in this research. 4. Obtained results in this research show that in both static and pseudo static slope stability analyses, as the number of geo-fabric layers increases, the safety factor increases in all different slope stability methods. The safety factor increases in all different methods as the spacing between the geo-fabric layers decreases. The results show that when the strong layer of foundation is located on top of the weak layer of the foundation, the safety factors are greater. The Janbu method gives the lowest safety factor against the other methods studied in this research.