m. hajiazizi

Road slope stabilization is one of the most common issues in reducing financial and life risks. Use of efficient and cost effective approaches for stabilizing earth slopes is a crucial matter. Due to Road growth, stabilizing of endanger slopes and insuring its safety is one of the basic concerns for engineers. With regard to regional condition, site importance, economical status, and many other factors, using common methods of stabilizing are diverse. One of these appropriate approaches for reinforcing earth slopes is the use of stone columns. Using stone columns, which, besides its simplicity and comfort implementation, is also very economical. The object of this research is presentation of experimentally and numerically investigates stone column stabilization of earth slopes, and investigates case studies about using stone columns in road slopes stabilization.

Earth slope stability is one of the main issues on which researchers all around the world focus on and various methods proposed in order to reinforce slopes (both natural and man-made). There are lots of approaches for stabilization of slopes, among which using a row of stone columns (or piles) is the most effective and economical method in order to stabilize and reinforce earth slopes and road embankments. Researchers have used different numerical and analytical methods for optimal locationing of stone columns or piles for stability enhancements of earth slopes or road embankments, which were resulted in different outcomes. This issue brings the question that, where is the optimal location for inserting these structural elements? It seems that laboratory analysis and modeling in this issue is missing. In this paper, the problem is examined by laboratory modeling and optimal location of stone columns and piles as reinforcing elements in earth slopes and road embankments investigated and the results are compared.

The use of stone columns is one of the effective ways to increase the bearing capacity of soils. An alternative system that can provide sufficient lateral confinement to support stone columns and increase bearing capacity is geosynthetic encased stone columns. These methods have been well utilized in Europe and South America. If the soil bed requires excessive confinement, the use of geotextile and geogrid encase around the stone columns is one way to improve the performance of these load-bearing members. This study aims to compare the behavior of geotextile and geogrid layers in reinforcing stone columns in standard Ottawa sand. In this study, a series of triaxial experiments in the undrained state was used. In the lowest confining pressure case, the load-bearing capacity for the geotextile reinforced column will be 1.18 times higher. Whereas for the geogrid-reinforced stone column, the load-bearing capacity is 1.31 times higher. In this study, standard Ottawa sand, gravel with a unit weight of 17 kN/m3 and a friction angle of 47.8°, geotextile and geogrid layers, and triaxial test apparatus are used. Triaxial specimens were 10 cm in diameter and 20 cm in height. Stone column dimensions of 2 cm in diameter and 20 cm in height are selected, respectively. Due to the limitations in the laboratory and the simulation of natural conditions, the unit weight of sand samples and stone columns made in triaxial test molds were selected as 15 and 17 kN/m3, respectively. Precipitation is used to fabricate cylindrical sand samples for triaxial testing. In this method, firstly attach the membrane to the underside of the triaxial apparatus and fasten the detachable bifurcation mold to the membrane and attach the membrane to the detachable mold walls by suction pumping about 2 bars. The aim is to create a homogeneous sample with uniform rainfall velocity to obtain a sample with evenly possible porosity. The method of precipitation depends on two parameters, one is the intensity of rainfall (amount of sand poured in a given volume at a specified time), and the other is the height of the sand fall, which is the distance between the sand outlet from the precipitation tank to the sand bed. The important point is that to achieve the same porosity, and this distance must be kept constant throughout the precipitation process. After construction, the test is performed according to ASTM D7181-11. Triaxial CU experiments on Ottawa sand were carried out in three cases: unreinforced, reinforced using geotextile encased stone column and reinforced using geogrid encased stone column. In triaxial experiments, three confining pressures of 200, 300, and 400 kPa were used.

Among the methods used to design the tunnel, the Q-system is a comprehensive method that has attracted the attention of many researchers today. However, the limitations of the Q-system make it impossible to access all the required parameters as well as the time and cost of them,  which has made it impossible to classify the rock mass using the Q-system. This paper attempts to predict the value of Q by parameters that have the highest coefficient of importance in the value of Q, using the Gene Expression Programming (GEP) technique. The most effective parameters involved in the Q value have been identified using Pearson correlation analysis (PCA), and then three different input models have been used to obtain Q value so that they are more closely related to experimental values. A total number of 159 experimental data were used for training and testing of the models, respectively. The innovation of this paper is that instead of 6 parameters, only three influential ones were used for determining the value of Q. Using the three parameters RQD, Jn and Ja, which have been determined as the most effective parameters and applying Pearson correlation analysis method, the value of Q can be determined with an acceptable approximation. In the suggested relation, the coefficients of determination (R2), root mean square error (RMSE), BIAS and the scatter index (SI) obtained were 0.917, 2.31, 1.74 and 0.43, respectively that show the new equation presented by GEP, can be undoubtedly used to predict the value of Q.

The tunnel overburden height has considerable effect on stability or instability of surface tunnels. In this research, effects of overburden surface tunnel in strong rocks in both static and pseudo-static states investigated. In this paper, the results of pseudo-static analysis comparing to static state analysis are outstanding. Due to superficiality of tunnel, the water table line considered lower than tunnel bottom. The static analysis performed by Finite Element Method (FEM) and Finite Difference Method (FDM) and both results are close and acceptable. Results of static analysis indicated that by increasing in overburden height, horizontal displacement in sidewalls of tunnel and vertical deformation of tunnel crest would decrease. The stress amounts in sidewalls and crest of tunnel in pseudo-static state are higher than static condition.

In recent years, the number of waste tires around the world is increasing rapidly and has become an environmental and economic problem. Today, accumulation of waste tires in the environment is one of the biggest problems to the environment and recycling waste tires is the best strategy to solve this problem. The use of waste tires in construction and geotechnical projects is one of the effective strategies in this regard. In this paper, experimental tests of earth slope reinforced with waste tires based on horizontal displacement (25 experiments) has been performed. During incremental loading, digital images were taken from the models and the particle image velocity (PIV) method was used. Parameters such as tire layer length, number of layers and tire layer position are considered as variable. The results show that the use of tire reinforcement has a significant effect on reducing horizontal displacement under the foundation and slope surface. Horizontal tire rows are the best reinforcement location in terms of improved bearing capacity and lateral displacement. When four layers of 60 cm long reinforcement tire are placed in the upper half of the slope, the bearing capacity increases 3 times and the lateral displacement under the foundation decreases by 3.1 times. When three layers of tires with a length of 60 cm are placed in the upper third of the slope, the bearing capacity increases by 2.3 times and the lateral displacement under the foundation increases by 1.3 times. When six, eight, and nine layers of reinforcing tires with a length of 60 cm are placed into the slope, lateral displacement under the foundation is reduced more than 3.5 times. In Iran, eight largest tire factories produce 13.5 million tires in a year. It also imports 4 million tires a year. Therefore, 17.5 million tires are the annual consumption of the country. More than 100,000 tires are the product of factory production line waste, as well as used tires. Waste tires have been used to strength retaining walls, foundations, improve soil properties, embankments and etc. Therefore it is believed that soil reinforced with waste tires become a wider application in the future, especially in countries with low worker costs. In this paper, the test was performed in a box with length, width and height of 2, 1, 1 m, respectively. The test material used in this study is sand in the dry state. The maximum and minimum dry sand densities are 19.43 and 16.36 kN/m, respectively. Internal friction angle and cohesion were measured by direct shear test at 38 degree and about 0 kPa, respectively. Digital images taken from the front of the test box during the experiment. Images were processed using GeoPIV software developed at the University of Cambridge. The results of this study are as follows:1. The best position in terms of bearing capacity and lateral displacement is to use four layers of reinforcing tire in the upper half of the slope.2. As the length of the reinforcement layer increases, the bearing capacity increases significantly and the lateral displacement decreases. Especially when the length of the reinforcement tire is 60 cm and the length of the reinforcement passes through the rupture wedge, the improvement in bearing capacity and lateral displacement of the foundation is noticeable.3. The best position in the three layers of reinforcement tire on the slope in terms of bearing capacity and lateral displacement is one-third of the upper slope.4. The presence of a tire in the lower third of the slope has little effect on improving the bearing capacity, lateral displacement of the foundation and the slope surface compared to the slope without reinforcement.

Utilization of numerical and analytical methods to stabilize earth slopes applying piles or stone columns is subject commonly discussed by numerous researchers. Various researchers have practiced optimization of the location of pile or stone column, to stabilize earth slope through numerical and analytical approaches. Their efforts have led to various results raising the question of what the optimal place for installation of a pile or stone column is. It is look like that no experimental studies are conducted in this regard; the point which is discussed in this article. Experimental study conducted in this article is new topic and it can solve the problem caused by varying and sometimes contradictory results of numerical analyses to find the optimal pile (or stone column) location. In this article, an experimental study is conducted for two-layer sand earth slope, which is saturated through precipitation and failure after saturation over time. Installing stone columns in different locations and saturating the earth slope through precipitation, rational acceptable results were obtained that can appropriately assist designers. All of the experimental models were modeled and compared using the 3D finite difference method (3D FDM), which are compliant with each other.

In the present study, shear displacements were calculated for all failure surface slices in earth slopes using the limit equilibrium method. To this end, the hyperbolic shear stress-strain constitutive law was applied. Local factors of safety were determined for the slices based on stress and displacement values. In order to calculate the displacement of earth slopes using the proposed method, a numerical model was developed satisfying the equilibrium of forces by a trial and error approach. A comparison between shear displacements obtained from this study in examples 1 and 2, with those obtained from FEM analysis which has yielded the normal errors of about 1.066% and 0.52%, respectively. Eventually, the effects of failure ratio ( ), and hyperbolic stiffness parameters (n and k) on displacement of earth slopes were examined.

In recent years, the need to make greater use of urban spaces on the one hand and the lack of these spaces in comparison with the ever- increasing demand of urban society are reasons for optimum utilization of available spaces with underground constructions such as tunnels. Most of these excavations with large volume of drilling are located at shallow depths and close to surface which cause displacements in the groundand effect of these movements can be seen as surface settlements in the soil. Surface settlements can be very influential in surface structures such as buildings and facilities that are located in densely populated urban areas and the vicinity of the excavated tunnels. The control of these settlements in order to protect surface structures during tunnel excavation, is the most important issue considered by design engineers. Analytical, experimental, and numerical methods for estimating these settlements were studied and presented by several researchers. However, experimental and semi-experimental methods are not able to include all parameters; so they cannot perform detailed calculation in complex problems. For this reason, the use of numerical methods was developed in order to accelerate and increase the accuracy of calculations, beside methods was developed.In the present work, the effect of tunnel support on surface settlement has been studied by using finite- element method after verification of the model results made with ABAQUS software along with the experimental results and observations of sections s5-28 of the Milan underground line1. As the thickness and length of the concrete lining as geometric parameters that affect the support system stiffness, they can affect the surface settlements caused by tunnel excavation. Therefore, it is important that the support have the optimum size to have the greatest effect on reducing the settlements. Finally, in the present work, the effect of thickness and length of concrete segments installed with EPB-TBM ,has been studied. Keywords: settlement, EPB-TBM, concrete segment, tunnel, finite element.

Slope stability analysis is used in a wide variety of geotechnical engineering problems such as embankments, road cuts, open-pit mining, excavations, canals, landfills, etc. The limit equilibrium method is the most popular approach in slope stability analyses. In this study, a new limit equilibrium method is proposed that can satisfy the forces and moment without any assumptions. In this method, circular or non-circular slip surface has been considered and slices are intended along the radius of the slip surface. Innovation of this research is in the form of slices in circle sector which could eliminate the common simplifying assumptions in the equilibrium equations. The forces and moment equilibrium equations have been applied without any simplifying assumptions and expected that this method can achieve lower error in determining the safety factor. In order to calculate the safety factor using the proposed method, a numerical model has been developed. In this model, the soil slope characteristics such as slope geometry, soil strength properties, seismic coefficient and also water level are considered as input. Then sliding wedge is introduced and on the basis of number of divisions that the user defines, sliding wedge is discretized. In the next step, the coordinates of each node of these slices are determined. To compute the safety factor, a process should be taken that satisfies the force and moment equilibrium equations simultaneously. To achieve this goal, the iterative method (trial and error) is used in this study. In order to evaluate the proposed method and the efficiency of the developed model, several tests with different conditions are solved. The mentioned test results are in good agreement with the results of other methods that satisfy all of the equilibrium equations.

To obtain the displacements of a tunnel is one of the major issues in the tunnel. In this paper, using the finite difference and finite element methods and measurements data, new relationships are presented between the 2-D and 3-D deformation of a tunnel. This comparison was performed between competent rock and jointed rock mass where different results are considerable. Empirical, numerical and analytical methods are regarded as different tools for design of tunnel. Nowadays, due to the advancement of technology, limitation on surface spaces, and political and security issues, many developed and developing countries focus on constructing underground structures for civil and military applications. Underground road and highways, tunnels, urban subway networks, power plants, nuclear waste repositories, oil reservoirs, shelters, and warehouses are structures which are rapidly under construction in different countries. It should be noted that these achievements have been made over a long time, accompanied by different problems. In order to predict the displacement of a tunnel with regard to its 2-D deformation, the new equations are proposed in this paper in 3-D case that can be employed. Due to the fact that in many numerical analyses, modeling is done in 2-D case, the relationships presented in this article can be real results. According to the results of the various analyses of intact rock mass, displacement of tunnel in 3-D is less than that in the 2-D case. But, in the jointed rock mass the displacement of tunnel in 2-D is less than that in the 3-D case. The results of this research have been verified by tunnel of Gavoshan's dam. After comparing and analyzing the results, relationships have been proposed for the coloration between 2-D and 3-D in intact rock mass and jointed rock mass. The solved examples give reasonable and acceptable results.