In recent decades, the growth of infrastructure in urban and metropolitan areas has led to a significant increase in the value of land and the lack of suitable places for development. These factors cause the construction industry to look for cheap land for construction; As a result, the building is run on the loose ground against the previous tendency. One of the methods that have been used in recent years in loose deposits and fine soils is stone columns, which are widely used to reduce subsidence and increase the soil bearing capacity of structures such as fluid storage tanks. Embankments, broad foundations, and light structures are used. The use of rock columns as a soil improvement method has been the subject of research by many researchers for the past 40 years. Numerous analytical methods, numerical analyze, and laboratory tests have been performed to investigate the effect of different soil and rock column parameters on the bearing capacity and subsidence of rock columns. One of the most significant research achievements in this field is the idea of reinforcing stone columns with geosynthetic cover, which was proposed more than 25 years ago. During this period, relations have been provided for designing these reinforced stone columns and considering the effect of geosynthetic cover. This paper presents the results of researchers' research on the effect of various parameters on the bearing capacity and subsidence of stone columns.In recent decades, the growth of infrastructure in urban and metropolitan areas has led to a significant increase in the value of land and the lack of suitable places for development. These factors cause the construction industry to look for cheap land for construction; As a result, the building is run on the loose ground against the previous tendency. One of the methods that have been used in recent years in loose deposits and fine soils is stone columns, which are widely used to reduce subsidence and increase the soil bearing capacity of structures such as fluid storage tanks. Embankments, broad foundations, and light structures are used. The use of rock columns as a soil improvement method has been the subject of research by many researchers for the past 40 years. Numerous analytical methods, numerical analyze, and laboratory tests have been performed to investigate the effect of different soil and rock column parameters on the bearing capacity and subsidence of rock columns. One of the most significant research achievements in this field is the idea of reinforcing stone columns with geosynthetic cover, which was proposed more than 25 years ago. During this period, relations have been provided for designing these reinforced stone columns and considering the effect of geosynthetic cover. This paper presents the results of researchers' research on the effect of various parameters on the bearing capacity and subsidence of stone columns..

Fatigue cracks are amongst the most important factors for destruction of asphalt pavements, caused by excess loads and traffic in roads and airports. GEOSYNTHETICS, as strengthening materials, are able to increase fatigue life and prevent early cracks in asphalt pavements, to a large extent. Efficiency of GEOSYNTHETICS in asphalt pavements depends on many factors including asphalt mix, temperature, location, etc ... This paper studies the performance of two types of GEOSYNTHETICS (Geogrid and Geotextile)on the fatigue life of asphalt blocks with dimensions of 381x63x50 mm. Samples were provided of non reinforced, reinforced by geotextiles and geogrids, from asphalt slabs for the purpose of testing. Fatigue tests were conducted by four point beam test, and fatigue load by half-sin wave at a frequency of 10 cycle/sec (no rest period) has been used. The end of fatigue life is defined as decrease stiffness to 50% of its primary stiffness. Results indicated that the fatigue life of reinforcement beam with geogrid and geotextile increase 56% and 50% respectively. Furthermore reinforcing layer increases primary stiffness and reduces rate of cracks propagation in reinforcement specimens compared to non- reinforcement specimens.

Today, the use of new materials to improve soil bearing capacity is widely used. One of the new materials used in this field is GEOSYNTHETICS. In many cases, standard solutions in geotechnical engineering to improve the ability and properties of soil are not practical. They need to use materials with easier access, lower cost, and better performance. From this research, the effect of different types of GEOSYNTHETICS and the application and optimal use of these new materials in geotechnical engineering in various projects such as foundations, pools, embankments, bridge bridges, and roads. In this research, reviewing previous studies on GEOSYNTHETICS, including numerical, laboratory, and numerical studies, an overview of the benefits and applications of these materials in civil and road engineering has been made. The research results show that GEOSYNTHETICS in Increasing the bearing capacity and improving the strength properties of the soil have many applications and are also more economically justified than other methods of soil improvement.

Conventional stone columns are widely used to improve soft soils in which high compressibility and low shear strength are observed. In very soft soils, granular columns may undergo excessive bulging due to a lack of lateral support provided by the surrounding soil. Wrapping the granular columns with appropriate geosynthetic material can reduce the total and differential settlements while improving the load-carrying capacity of the reinforced ground. A compacted sand or gravel mat (known as a working platform) placed below the embankment is commonly used to prevent excessive lateral deformation of the foundation’s soft soil. In the circumstance of very high applied load, this granular mat may be further reinforced with a geogrid layer to enhance its effectiveness and control the overall stability of the embankment. This paper presents the results of a series of three-dimensional numerical analyses to study the development of hoop forces in geosynthetic encasement under different combinations of working platform thickness and basal geogrid stiffness. The results showed that for a constant working platform thickness, the hoop forces increased with the height of the embankment. The maximum values of the encasement hoop forces were also observed to reduce significantly as the thickness of the working platform increased

The superiority of the geosynthetic reinforced soil wall to another reinforced soil systems, is led to the increasing expansion. So far many studied have been conducted on GEOSYNTHETICS reinforced soil walls, with assuming rigid bed. But the behavior of this system and mechanism of it components has less been considered when the bed is compressible or loose. The present study investigated the effect of effective parameters (i. e., facing inclination, connection type of geogrids to the facing, toe condition, length of reinforcement and vertical distance of reinforcements) on the behavior of reinforced soil wall seated on compressible bed, using finite element method. Also the behavior of the wall under conditions of end of construction and surcharge loading has been investigated. The results showed that the parameters that had the greatest effect on the behavior of the reinforced soil wall during the weakening of the bed, is facing inclination, vertical distance between reinforcements and toe condition. Decreasing vertical distance of reinforcements and increasing facing inclination, has led to significantly decrease in horizontal displacement of wall and maximum reinforcement load. Also according to the results, the bed with compressible soil, the type of connection of reinforcement and length of reinforcement did not show a significant effect on the improvement of the wall’ s behavior, except when the wall was placed on a loose bed.

In recent years by increasing the terrorist threats and explosive operations in urban areas, protecting the important life line infrastructures against threats that arise from the explosion has become more important. Hence, predicting the extent of the destructive power of the explosion and its effects on soil layers necessitates further studies and researches. In order to reduce stress caused by the explosion and to control increasing compressive and shear stresses in the soil and lateral pressure on the pipes, several solutions have been presented. One of these solutions is utilizing geosynthetic reinforcement. In reinforced soils, the mechanism of stress transfer is based on the interaction of soil and reinforcement elements. The shear stress reaction causes tensile forces in reinforcement elements. This phenomenon leads to an increment of shear strength, elasticity and ductility of the reinforced soil. In this study, FEM method is used for modeling pipelines buried in the reinforced sandy soil exposed to surface blast loading. By comparing the results, it can be concluded that by using reinforcement in the soil, the stresses and deformations in the buried pipeline could be reduced. The results show that the deformation rate obtained from the placement of reinforcements at a depth of 1. 5 m from the ground level (with a fixed width), has decreased by an amount of 35%. In addition, the rate of reduction in deformation of the pipe crest has decreased about 51% using a 4 meter wide reinforcement at a constant depth of 1 meter.

Stabilization of excavations and retaining walls are important issues in the geotechnical field. The use of new and novel methods in excavation sites, and providing safe conditions for the final aim of the project is one of the challenging matters in this regard. Excavation in sandy soils, due to lack of enough cohesion for its stability, faces serious problems. In order to solve this problem, using special techniques to improve stability is a very important subject. GEOSYNTHETICS (i. e. geotextile, geogrid, and geocell) are among the new techniques, which could enhance the stability and performance of sandy soils. In this research, 3D finite different analysis was performed to investigate unreinforced and reinforced excavations using geotextile, geogrid, and geocell elements and their comparison. Results indicated that in the case of using geotextile, geogrid and geocell the critical depth of excavation increased up to 3. 125, 2. 75, and 2. 25 times of unreinforced excavation, respectively.

In this research, numerical simulation using the finite element method and PLAXIS numerical software (version 8.2) were used. Also, the calculation point of the road settlement, which is the criterion for comparing different models, is selected in the loading center on the road, which is considered as the representative of the road settlement in the output results of the vertical displacement. The results of the numerical investigation of the effect of the tensile strength of GEOSYNTHETICS on the road settlement show that this parameter did not have a significant effect on the road settlement. Also, from the numerical modeling of the effect of the length of GEOSYNTHETICS on the road body, it is determined that the settlement of the road in modeling with geogrid is the same size as the width of the road (which is equal to 7 meters in this model) equal to 3.65 mm and with geogrid 9 meters wide. It is equal to 3.5 mm. The results showed that if the amount of friction between the geosynthetic element and the soil is considered equal to the internal friction angle of the soil, the settlement of the road at the loading center of the model has decreased by 12%. Finally, the investigation of the effect of geosynthetic element placement on the road settlement shows that by moving the geosynthetic layer from the sub-base-substrate boundary to the top-base boundary, the road settlement decreased by 0.9 mm.