In this research, failure mechanism, soil deformation and effect of reinforcement below a STRIP FOUNDATION were studied using physical modeling and PIV method. For this purpose, a comprehensive set of tests were undertaken on dense and loose sands and different geosynthetic materials such as geotextile and geogrid for soil reinforcing. In each step of loading, digital image of deformed soil was captured and image processing was applied with GeoPIV software. The experimental results showed that using of geogrid and geotextile leading to increase bearing capacity considerably, reduce settlement and change the failure mechanism of sand. The test results showed also that geogrid has an effective performance in comparison with geotextile in sand at the range of small strains.

Introduction: Studying the effect of slope angle on bearing capacity of FOUNDATIONs on the slope in urban areas is a challenging problem that has been investigated by researchers for years. In general, the analytical approaches for solving this problem can be categorized into limit equilibrium, characteristics and limit analysis methods. In recent years, there have been studies for using the limit analysis within the framework of finite element method for geomaterials. In these studies, the soil mass is not considered as rigid and there is no need to predefine a failure surface for the slope. In the performed research, using the upper bound finite element limit analysis, bearing capacity of STRIP FOUNDATION on slope have been studied. This analytical method enables the use of the advantages of both methods of limit analysis and finite element analysis. In this method, the slip between the two elements is considered. In order to find the critical state of the failure, the rate of power internally dissipated is linearly optimized, by using the interior points method. The advantages of this method are the high convergence rate in comparison with other analytical optimization methods. The effect of different upstream and downstream slopes and FOUNDATION depths and also the influence of various mesh discretizations have been evaluated. Finally, the results are compared with those obtained from previous methods available in the literature. Methods: The finite element limit analysis method is based on nodal velocities. Considering the principals of the finite element method and having the nodal velocities, the velocity at each node of the element can be obtained from corresponding shape functions. The rate of power internally dissipated in each element is defined by multiplying the strain rate on stress in each element. In this method, the slip between the two elements and the rate of internal power dissipated at each discontinuity of two adjacent elements is considered. For this purpose, in each node, four new unknowns’ velocities are defined. To remove the stress from the equations, and provide a linear relationship for linear optimization, a linear approximation to the yield function has been used. For this purpose, the Mohr-Coulomb yield criterion is estimated with a polygon in the stress space. Also, using the reduced strength parameter, the effect of the dilation angle is considered. According to the principles of upper bound limit analysis, the value of plastic strain rate is calculated from the flow rule. The velocity field in elements and discontinuities must satisfy the set of constraints imposed by an associated flow rule. In order to have an acceptable kinematics field, the velocity vectors have to satisfy the boundary conditions. These conditions include zero kinematics velocities along the vertical and horizontal boundaries of the geometry as well as negative vertical unit velocities and zero horizontal velocities at points underneath the rigid FOUNDATION. Results and discussion: In order to calculate the bearing capacity of FOUNDATION, a set of different uniform and non-uniform mesh has been examined. The results obtained from different uniform mesh sizes indicate a certain divergence in the course of analysis. However, the results between the fine and very fine non-uniform mesh are closely related to each other and are converged. The obtained results show that, by increasing the internal friction angle, the bearing capacity has been increased. At high angles of modified friction, the effect of increasing the internal friction angle on the increase in bearing capacity is more in slopes with lower angles. By increasing the downstream FOUNDATION depth, the bearing capacity has been increased. This increase is more important in the case of slopes with lower angles. However, the upstream depth variations didn't present a significant effete on bearing capacity. In order to investigate the effect of upstream angle on the bearing capacity, the upstream mesh is also refined similar to the downstream. The obtained results indicate that variations of the upstream angle have a minor effect on the bearing capacity. This is of course true if the upstream slope is fully stable. The results of the proposed method in this study are an upper bound for the results reported by the limit equilibrium and displacement finite element methods. As seen in Figure 1, the suggested method predicts lower bearing capacities compared to rigid block limit analysis method and is indeed a lower bound for the classical limit analysis method. The finite element limit analysis with linear optimization has resulted in more bearing capacity than cone optimization. The bearing capacities, obtained from characteristic lines method depending to the slope angles, in some cases is more and in some cases less than those explored by the proposed method. In this paper, the bearing capacity of FOUNDATION located on slope was evaluated by finite element limit analysis method. In this regard, the effects of different downstream and upstream angles of slope and FOUNDATION depths and also, the effect of various mesh discretizations on the bearing capacity were studied. It is shown that an increase in the downstream angle causes a decrease in the bearing capacity and an increase in the downstream FOUNDATION depth leads to an increase in the bearing capacity. However, the upstream angle and upstream FOUNDATION depth were not much effective on the bearing capacity.

In recent years, due to the increasing use of hydrocarbons by humans, soil contamination has become a concern in environmental and geotechnical engineering  elds. In the other words, by the growth and development of industries, the number of factories, complexes, re neries and oil product transportation lines around cities increases. Hence, in addition to the environmental concerns caused by the leakage and entrance of pollutions into groundwater and their side e ects, the soil geotechnical characteristics and bearing capacity of soils contaminated by oil contaminations are subject to change. Accordingly, in the oil-rich regions of the world, a great deal of research is devoted to the study of soil re nement, bearing capacity and instability caused by soil contamination. A numerically study was undertaken to achieve an accurate and realistic response. As a review of the previous research indicated, in recent decades, most studies have focused on the geotechnical properties of contaminated soils and there is only a limited amount of information about the bearing capacity and the FOUNDATION settlement behavior. Thus the purpose of this paper is to determine the behavior of STRIP footings rested on the gasoil and kerosene-contaminated sand slope. After determining the bearing capacity, the e ect of petroleum products, including gas oil and kerosene oil, on the bearing capacity of STRIP footings adjacent to sand slopes was investigated. In this study, variables such as the type and percentage of contamination, slope angle, footing distance to slope crest and the thickness of the contaminated layer have been investigated. The results show that a thicker contaminated layer and a greater degree of contamination and soil slope will decrease the bearing capacity of the STRIP footing. Furthermore by increasing the footing distance to slope crest, the bearing capacity of STRIP FOUNDATION is increased. The numerical results have been veri ed for both the load-settlement diagram and the ultimate bearing capacity of the footing, by recent experimental results.

Shallow FOUNDATIONs, such as STRIP FOUNDATIONs are widely used in transmitting loads from the superstructure to the supporting soils. In many cases, the ground materials are not uniform and may have thin layers, which are not usually detected in geotechnical site investigations. In this research, the effects of a thin layer on the ultimate bearing capacity of a STRIP FOUNDATION on the sand bed are investigated by small-scale physical models. Due to very limited research that has been carried out on the thin layer effect on the ultimate bearing capacity, it seems that further studies can understand the effect of this layer. The investigations were carried out by varying the material type, thickness, and depth of the thin layer. The results indicate that the weak thin layer decreases both the ultimate bearing capacity and stiffness of the soil-FOUNDATION system and the strong thin layer increases both the ultimate bearing capacity and the soil-FOUNDATION system stiffness. The amount of this effect depends on the thickness, depth of deposition, and material type of the thin layer. According to the results, the weak layer for the critical depth of 1.2B led to the most reduction in ultimate bearing capacity by 40%, while no effects were observed at a depth of 3.6B. The strong layer is also for the state where this layer is just below the footing, had the highest increase in ultimate bearing capacity by 76%, but at a depth of about 2.4B, it was ineffective.

Building construction on slopes is inevitable, despite many limitations. Due to the seismicity of Iran, calculating the seismic bearing capacity of FOUNDATIONs is more important. The construction along a slope has been observed to result in a reduction in the bearing capacity. To mitigate this decrease, various improvement techniques, such as soil reinforcements like geogrids, can be employed to partially offset this reduction. The present study investigates the impact of ground slope (10 and 20 degrees) on the bearing capacity of granular soils with varying internal friction angles (25, 30, 35, 40, and 45 degrees) in both seismic and static conditions. This investigation employs the finite element limit analysis method and OptumG2 software to determine the upper and lower bounds of the bearing capacity. The findings indicate that the implementation of kh=0.1 leads to a reduction in the seismic bearing capacity of the FOUNDATION, ranging from 2 to 12 percent. The effective length of the geogrid is contingent upon the internal friction angle of the soil and varies within the range of 2B to 3B. Additionally, the study revealed that the optimal distance between the footing and the slope edge (X/B) is influenced by the internal friction angle, with a significantly bigger impact than the slope angle. The optimal distance (X) was estimated to lie within 2B to 4B for internal friction angles of 25, 30, and 35 degrees. Conversely, for internal friction angles of 40 and 45 degrees, the X value was assessed to be no less than 5B.

Most of the available soils in nature are non-homogeneous and can be considered as a homogeneous layer with simplifications. So far, different methods have been presented in order to achieve bearing capacity of these soil types. Stress Characteristic Lines Method, presented by previous researchers, is one of the best numerical methods able to determine the bearing capacity of FOUNDATIONs. The important advantage of this method over the other numerical methods is that it neither requires the customary and troublesome meshing nor uses complex and specific behavioral models of soil, whereas only the stress field is required at the collapse moment not the strain field, and the computations are performed with higher speed and simplicity. So far, previous researchers have been able to provide programs through this method in order to estimate the bearing capacity of homogeneous soil. However, this is not true in all cases. Layered soils are mostly encountered in practice. The thickness and also cohesion of layers are the e effective parameters in this regard. The present article evaluates the bearing capacity coefficient (N*C) of a STRIP in FOUNDATION for two undrained clay soil layers (upper layer is weaker than lower layer) with respect to changes in the upper layer thickness as well as variations in cohesion ratio of two layers by using the mentioned method. Therefore, in addition to briefly reviewing the technical literature and calculation procedure of STRIP FOUNDATION based on homogeneous soil, an algorithm for two layered soil is presented. Then, by using BCTL software (Bearing Capacity of Two Layer) obtained by this algorithm, changes of static load bearing capacity of the STRIP FOUNDATIONs (N*C) on the two undrained clay layers have been evaluated. As expected, by increasing the ratio of Cu1/Cu2 to one (for different thickness of top layer over width of STRIP footing), bearing capacity coefficient (N*C) is converged into number 5.142.

Determining the bearing capacity of the soil and its subsidence is one of the most important parameters that must be carefully evaluated when designing a safe FOUNDATION. In the present study, using a physical model, the behavior of the FOUNDATION located on sandy soil under static loading and the effect of various factors on soil behavior have been investigated. In this laboratory study, the effect of FOUNDATION width, sandy soil density and amount of overhead on STRIP FOUNDATION subsidence has been investigated. The soil material used in this study is poorly grained medium sand (SP). The FOUNDATION model has a width of 5, 7.5 and 10 cm and its length is 34 cm. The sand raining technique has been selected to obtain a homogeneous sample with a definite relative density and repeatability of laboratory conditions. The loading system is compressed air that has the ability to apply a uniform and static load. The relationship between the final relative settlement and the width of the FOUNDATIONs located on medium-density sandy soils is linear, and as the FOUNDATION width increases, the final relative settlement reaches less than its final ultimate bearing capacity. At the same pressure, the settlement of the FOUNDATION located on medium-density sandy soils is about 10 % higher than the FOUNDATION located on dense sandy soils. Soil behavior up to a pressure of about 50% of the final bearing capacity is linearly elastic. The pressure- settlement relationship of the STRIP FOUNDATION is linear up to about 5% of the FOUNDATION width. General shear failure occurs at a relative settlement of about 12 to 14%. For this reason, it is suggested to determine the ultimate bearing capacity of the STRIP FOUNDATION located on sandy soil, the amount of pressure such as 12% .

In this study, several methods have been experimentally evaluated to increase the efficiency of reinforcements in the bearing capacity of a STRIP footing on sand. The capacity of the FOUNDATION in five different configurations including single and multilayer reinforcements was evaluated with free and wraparound anchored end, different thickness, and nailed with different numbers of nails and patterns. According to the results of these tests, dividing the length of the reinforcement and using it in more layers increases the efficiency of the reinforcement, but this division of the length of the reinforcement has a certain limit that reducing this limit reduces the efficiency. The use of wraparound anchorage caused more interaction between the soil grains and the reinforcement surface and as a result increased the bearing capacity of the FOUNDATION. Increasing the thickness of the reinforcements was another parameter studied in this study. Increasing the thickness of the reinforcement caused the bearing capacity to increase.  The results of the experiments show that the pattern of nails has a significant effect on the performance of the reinforced soil.