issa shooshpasha

The bio-mediated soil improvement techniques have been gaining increasing attention recently. In this method, the bacteria was cultivated aerobically in the laboratory and added to the soil with reactant solutions such as urea and calcium chloride. Most of the existing studies are on sandy soils and few researches have been done on silty sandy soils. However, most soils in nature are compounds of fine-grained and coarse-grained soils. In fine-grained soils, silt does not have very good resistance due to the lack of adhesion between its particles. Hence, in this study Sporosarcina pasteurii bacterium was cultivated aerobically for stabilizing sand with different percentages of silt to determine the optimum bacteria suspension volume. After some bacterial tests such as measuring bacterial growth, standard plate count, gram staining, pH determination, growth without urea, and urease test, geo-technical tests like soil sieve, compaction, and Atterberg limits were also done. Standard plate count was estimated 2.5*108 through serial dilution plating and culture media pH was determined 8.64 from different samples. Moreover, to achieve the best results, different sampling methods were compared. As the calcium carbonate creates a network of calcified bridges of calcite between sand grains, an electron microscope was used for scanning the surface with a focused beam of electrons. Results of triaxial tests show that the maximum strength for samples with 0%, 10%, 20%, 30% and 40% of silt was improved from 700, 900, 750, 600 and 550 to 1100, 1400, 1550, 1600, and 1500 kPa respectively by adding optimum bacteria suspension volume.

Hydraulic conductivity of soils is one of the most important parameters in designing soil structures, water, and environmental resources management. Hydraulic conductivity in the soil varies with the size of their particles. Several studies by different researchers on fine-grained soil hydraulic conductivity and coarse-grained soils are done. In some studies, the methods and materials used to reduce soil hydraulic conductivity. On the other hand, nanoclays are nanoparticles of layered mineral silicates. Depending on chemical composition and nanoparticle morphology, nano clays are organized into several classes such as montmorillonite, bentonite, kaolinite, hectorite, and halloysite(Majeed and Taha, 2013). Organically modified nanoclays (organoclays) are an attractive class of hybrid organic-inorganic nanomaterials with potential uses in polymer nanocomposites, as rheological modifiers, gas absorbents, and drug delivery carriers(Abbasi et al, 2016).Plate-like montmorillonite is the most common nanoclay used in materials applications. Montmorillonite consists of ~ 1 nm thick aluminosilicate layers surface-substituted with metal cations and stacked in ~ 10 µm-sized multilayer stacks. Depending on the surface modification of the clay layers, montmorillonite can be dispersed in a polymer matrix to form a polymer-clay nanocomposite. Within the nanocomposite individual, nm-thick clay layers become fully separated to form plate-like nanoparticles with a very high (nm × µm) aspect ratio.In this study, the effect of different amounts of montmorillonite nano clay (0.25, 0.5, 0.75, and 1%) on the hydraulic conductivity in three different densities (85, 90, and 95%) of sandy and clay soils have been investigated experimentally.

Several numerical studies have been carried out to analyze the behavior of piled raft foundations, but very few experimental studies are reported in literatures. The conventional approach for the design of piled raft foundations ignores the raft load sharing and it has been assumed that the piles carry the whole of structural loads. This approach is unduly conservative and lead to an uneconomic design. Only when the piles cap is elevated from the ground level, this design method is valid. In a piled raft foundation, pile-soil-raft interaction is complicated. The available laboratory studies are mainly focused on steel piles. The present study aimed to evaluate the behavior of piled raft foundations in sand, using experimental physical models.

ABSTRACT Piles are relatively long structural foundation members that are used to transmit loads from soil layers with low bearing capacity (or high settlement) to deep soil layers with high bearing capacity. In foundation design, determination of pile bearing capacity is considered as a complex issue. In this paper, the bearing capacity of steel pipe piles in sandy soil is studied using the results of static compressive load test. Piles were installed in soil using the jacking method. In this method, at first, a hydraulic jack was applied for installing piles and then, it was used for applying the compressive load required in the static load test. After recording data, the values of bearing capacity of the piles were compared with the values calculated from analytical methods. Then, the values of friction capacity of piles were evaluated using the results of tension test. The results showed that due to the effects of soil plug on the bearing capacity of piles and installing piles using the jacking method, the obtained values of bearing capacity of the piles are much than their analytical ones. Moreover, the results indicate the effect of frictional resistance on the ultimate bearing capacity of the piles.

Raft foundations usually have a high bearing capacity in sand, but the amount of settlement limit the allowable bearing pressure. Nowadays, the employment of piled rafts foundations as a solution for decrease of settlement is common. In such cases, the raft usually carries a high portion of structural loading, and the piles are as the settlement reducer elements. The number of piles and their configuration are determined that settlement of the foundation decreases to an allowable value. In these situations, the configuration of piles is determined in optional manner and strategically. In a piled raft foundation, pile-soil-raft interaction is complicated. Although several numerical studies have been carried out to analyze the behaviors of piled raft foundations, very few experimental studies are reported in the literature. This paper concentrates on study of behavior of piled raft in sand by physical modeling and finite element analysis method. The piles and raft models were made of cast-cast-in-place concrete. The physical models consisted of single pile, single pile in group, unpiled raft and piled raft foundation. The size effects of the models were investigated. The results showed that with installation of the single pile in the group, the pile bearing capacity and stiffness increase. Due to increase of the number of piles beneath the raft, the bearing capacity of raft increase and its settlement decrease, significantly. With the use of finite element method and the critical state theory, one can predicate behavior of test model in the full scale dimensions.

Improvement of weak soils with adding elements such as fibers that can increase tensile strength and stabilizing soils with additives that react chemically with them to make soils with desirable engineering properties is called reinforcement and stabilization (Consoli et al 2009). Researchers have always tried to improve bearing capacity, strength and properties of soil using different methods such as mechanical and chemical modifications and also reinforcement by high tensile strength elements Ghiassian, H. and Holtz, D, H., 2005). Randomly distributed discrete fibers offer strength isotropy and limit potential planes of weakness that can develop parallel to oriented reinforcement (Yetimoglu, T. and Salbas, O., 2003). Cementation in its general sense is binding and in geotechnical engineering, cementation is sticking soil particles to each other to form a cohesive mass with a higher strength. Soil structure is one of the factors that can affect behavior of (fine and coarse- grained) soils. Cementation plays an important role in the structure formation of coarse-grained soil. Soil structure is geometric arrangement of the soil particles and the forces, if any, between them the objective of this research is experimental study of the effect of reinforcement and stabilization on the behavior of sandy soil and evaluating effect of fibers on the shear behavior of cemented sand using strain-controlled triaxial tests under consolidated undrained conditions.

Chemical stabilization by cement is among the factors of optimizing the soil performance. Numerous studies have been performed in the field of using cement as a stabilizing material (Naderi Nia- Naeini SA, 2009; Dupas J, Pecker A, 1979). The results of this research show that the addition of cement to the soil increases stiffness and improves soil’s failure behavior and its engineering properties. Improving the engineering properties of the soils stabilized with cement is essentially due to hardening of cement as a result of hydration of cement and forming additional cementitious materials between the hydrated cement and clay particles in the soil (Shihata SA, Baghdadi ZA, 2001). On the other hand, although cement industry has adopted the most modern technologies to reduce pollution, different stages of cement production and transportation have a great share in the environmental pollution. Studies indicate that to produce one ton of cement and clinker in Iran 0.655 and 0.79 tons of CO2 greenhouse gas are emitted respectively (Milika Bildrici 2019). Therefore the cement mix optimization is such that the lowest amount of energy is used to produce it with the least damage to natural resources and finally the best performance possible is provided which is considered as a main goal (Khaleghi, M. H. 1990).

In conventional design of pile foundations, all loads are taken by the piles, i.e. the contact pressure between the raft and the soil is neglected. In the last decades, geotechnical engineers have started to take this pressure into account in design of pile foundation. Such a foundation, where the raft and the piles interact to transfer the loads to the ground, is in this dissertation called piled raft foundation or piled raft.
Waste tires, rubbers and plastic materials, normally produced in every society, enter the environment and cause serious problems. These problems may, to some extent, be reduced by finding applications for them in engineering, for example,they can be used for geotechnical applications as backfill material and solving problems with low shear strength soils like clayey soil. Therefore, this experimental work has been performed to investigate the influence of randomly oriented fiber inclusion on the geotechnical behavior of clayey soils. In general, some characteristic properties of tire materials are the low density, high elasticity, low stiffness and high drainage capacity. These properties open up possibilities for utilization of the material in an innovative manner. By adding small quantities of rubber chips in the soils, the natural elasticity of rubber could help lower the stiffness of the stabilized material and introduce more flexibility in the final stabilized columnar system.

To implement asphalt roads in an area, in many cases, especially in poor and swampy areas, there is a need for improvement. In recent years, the use of reinforced soil is common for the design of roads, foundations and retaining walls. On the other hand, the solid waste management, in terms of large volume and longtime decomposition of wastes such as sack polypropylene fibers, in addition to its effective role in the economic cycle is as one of the important indicators of development at the macro level in developing countries. Therefore, reinforcing of soil with the use of waste materials has a particular importance. In this research, by performing a laboratory experiment, the effect of adding various percentages of sack polypropylene fibers on the behavior and values of strength parameters of non-cemented and cemented sand (with three weight ratios of 3, 5 and 7% and 7-day treatment time) were investigated. The results show that the presence of these fibers has a significant effect on the behavior of non-cemented and cemented sand. Adding these fibers improves the strength parameters (φ and C), increase the maximum strength, failure strain and residual strength of soil. The effect of these fibers on the all studied parameters in non-cemented soil is higher than that of cemented soil. Also, their effect becomes less by increasing the percentage of cement in cemented soil. According to the research, these materials can be used in the road beds, which has environmental benefits, in addition to economic benefits

Pile foundations often used to transfer structural loads into deeper layers. On granular soils shaft resistance is an important factor bearing capacity of axially loaded, especially when the pile is subjected to tensile loading. Tensile forces apply on the pile holding the position of ship repair, basements, pumping stations, waterworks structures which are under water. In addition, transmission lines towers, tall chimneys, submerged platforms, masts, and other similar structures that are built on piles, in exposed disturbing moments resulting from wind, earthquakes and sea waves. In such structures, disturbing moments transferred, in some piles for pressure and other piles for tensile load. So, study the behavior of these piles and also effective parameters on the tensile capacity of is very important. Bearing the applied tensile loads on structures is one of the important applications of deep foundations, especially piles. Tensile capacity of these foundations is often produced by the frictional resistance in soil-pile interface. Piles are deep foundations which have considerable acceptance because of multi-applications. Understanding the behavior of piles and prediction of their tensile capacity is so important. In the last three decades various theories have been created regarding the behavior of piles under different loading conditions. The validity of these theories is evaluated by comparing the test results on models or structures piles with the predictions of theoretical. The field tests are Perfect scale and highly desirable, but often costly and difficult. For this reason, laboratory experiments are used to study the behavior of piles under tensile load. But to consider real conditions of the area, especially coastal sites, can be installed the piles in the soil that have been used to study the tensile behavior of piles. The reliability of tension test results in the homogeneous soils and the impact of surface layers of sand in providing friction force are special cases that have not been tested in real conditions of the site. Different methods are developed to achieve safe, constructible and economic design, such as analytical, experimental and in-situ methods, but in some cases they are still subjected to limitations. These methods can’t neither determine tensile capacity of pipe piles in coastal sand nor examine behavior of them. Since jacking technique is recommended for achieving improved soil properties and eliminating the deficiencies of other installation methods, so investigation of its effect is important. In this method, after jacking the piles with hydraulic jacks, the piles are arbitrarily tested under compressive loading to determine their compressive bearing capacity and then their tensile capacity is determined based on ASTM D-3689 procedure. After reading test data, the ultimate tensile capacity of piles were determined using tensile capacity criteria and then compared with analytical results. Tensile behaviors of piles at large displacements are also investigated and required force for larger pull out displacements were measured. The results showed that determined uplift capacities are more than analytical results and sand compaction due to pile installation can increase frictional resistance. It also revealed that the tangential criterion is determinant to obtain ultimate tensile capacity in most piles.

It is widely known and well emphasized that the cemented sand is one of economic and environmental topics in soil stabilization. In some instances, a blend of sand, cement and other materials such as fiber, glass, nano particle and zeolite can commercially available and effectively used in soil stabilization in road construction. In this investigation, zeolite and its effect on compaction studied as one of pozelan additive material to cement. Therefore, cilinopiolite kind of zeolite, Neka cement type II and Babolsar sand are used. Compaction poroctor tests were carried out on 24 combination type of cement and zeolite with include different cement percentages 2, 4, 6 and 8 percent of total dry weight of samples and replacement percent’s of 0, 10, 30, 50, 70 and 90 cement with zeolite. Results show that by replacement cement material by zeolite, the maximum dry density increased 2 to 2.5% in comparison with cemented samples and 14% optimum water content approximately concluded. At the end, a function fits Based on Voltra series presented to relate maximum dry density and zeolite-cement-soil parameters.

The improvement of local soils with cement and zeolite can provide great benefits, including strengthening slopesin slope stability problems, stabilizing problematic soils and preventing soil liquefaction. Recently, dosage methodologies are being developed for improved soils based on a rational criterion as it exists in concrete technology.The present study aims to quantify the influence of the amount of cement, zeolite, the porosity and the curing time in the evaluation of unconfined compressive strength (UCS) of zeolite-cemented sand mixtures. A program of unconfined compression tests considering three distinct voids ratio, four cement contents (varying from 2 to 8%), six zeolite contents (varying from 0 to 90%) and three curing time (7,28 and 90 days) was performed in this paper. The results show that UCS values of samples substantially increased with increasing zeolite content to an optimum value of 30% after 28 days of curing time. The rate of improvement is approximately between 20 to 80% and 20% to 60% for 28 and 90 days curing times respectively. Moreover, the polynomial models are shown to be appropriate one to estimate UCS values of zeolite-cemented mixtures. Additionally, the sensitivity analysis reveals the influence of parameters and the contribution of each coefficients in the polynomial model. Cement and zeolite content relates more strongly among relative density and curing time.

The lack of accessibility of high quality materials and the increased costs associated with the use of these materials will finally demand engineers to use local soils. In such cases, ground improvement performed reasonably in many conditions. Ground improvement can be defined as the procedure of increasing shear strength parameters and decreasing the permeability and compressibility of the soil. Different methods can be used to improve the geotechnical properties of the problematic soils such as loose sand that one of them is using additives. The stabilization of soils with cement is an attractive technique due to economic and environmental issues and avoiding the use of borrow materials from elsewhere. Cementation of sand results in increased brittle behavior as peak compression strength increases. The compressive strength of artificially cemented soils has been studied in the past by several investigators.A number of studies have also reported on the influence fiber, glass, fly ash, silica fume and nono particle on the mechanical behavior of cemented sands .However, to the author’s knowledge, there has been a little effort devoted to the research on the use of pozzolans such as natural zeolite as an addictive material to the cemented sands. Natural zeolite, an extender, has been investigated for use as cement and concrete improver by some researchers.
It is widely known and well emphasized that the cemented sand is one of economic and environmental topics in soil stabilization. In some instances, a blend of sand, cement and other materials such as fiber, glass, nano particle and zeolite can commercially available and effectively used in soil stabilization in road construction. In this investigation, zeolite and its effect on unconfined compression studied as one of addictive material to cement. Therefore, cilinopiolite kind of zeolite, Neka cement type II and Babolsar sand are used. A total number of 144 unconfined compression tests were carried out on 24 combination type of cement and zeolite include different cement percentages 2, 4, 6 and 8 percent of total dry weight of samples and replacement percent’s of 0, 10, 30, 50, 70 and 90 zeolite with cement based on 50,70 and 85% relative densities in7 and 28 days curing times. Results show that in 28 day curing time, by replacement percentage of 30 zeolite material by cement, the unconfined strength increased 20 to80% in comparison with cemented samples by increasing shear strain. For higher cement content and less compacted blends, these improvement rates are more. At the end, a power function fits presented to relate unconfined compressive strength (UCS) and zeolite-cement-soil parameters (porosity (n) and voids/ polynomial model of cement and zeolite voids).It is widely known and well emphasized that the cemented sand is one of economic and environmental topics in soil stabilization. In some instances, a blend of sand, cement and other materials such as fiber, glass, nano particle and zeolite can commercially available and effectively used in soil stabilization in road construction. In this investigation, zeolite and its effect on unconfined compression studied as one of addictive material to cement. Therefore, cilinopiolite kind of zeolite, Neka cement type II and Babolsar sand are used. A total number of 144 unconfined compression tests were carried out on 24 combination type of cement and zeolite include different cement percentages 2, 4, 6 and 8 percent of total dry weight of samples and replacement percent’s of 0, 10, 30, 50, 70 and 90 zeolite with cement based on 50,70 and 85% relative densities in7 and 28 days curing times. Results show that in 28 day curing time, by replacement percentage of 30 zeolite material by cement, the unconfined strength increased 20 to80% in comparison with cemented samples by increasing shear strain. For higher cement content and less compacted blends, these improvement rates are more. At the end, a power function fits presented to relate unconfined compressive strength (UCS) and zeolite-cement-soil parameters (porosity (n) and voids/ polynomial model of cement and zeolite voids).

The piles are foundations that transfer the load from building to the subsoil. And generally used in situations where spread or mat footings are not the best choice. Some examples include situations where the surface soil is weak and compressible, the structural loads are very high the upper soil is subjected to scour, and horizontal load capacity is required Due to poor bearing capacity and settlement of the soil, application of the piles have a long history Correct estimation of bearing capacity of piles is one of important issues that is always under attention of geotechnical researchers, because determination of ultimate bearing capacity of piles is required for their safe designing. The effect of various issues such as inhomogeneous, and variety of the soil, water, the diversity of the various combinations of the soil in nature, possibility of the creep, complicate behavior of stress-strain, complicate interaction of the soil and pile, pile material, and methods of construction make some difficulties in determination of the bearing capacity. Transmission of load from the pile to the soil is by the shaft friction and toe. it is important to know the exact of amount the friction resistance, therefore in this study, the shaft resistance of piles in Sorkhrood sandy soil was investigated through 14 pressure loading tests on small scale concrete piles with different dimensions and the obtained results were compared with the results of some other methods.

Settlement based design for shallow foundation realizing consolidation aspect is a major task of geotechnical engineer. Compression index (Cc) from the odometer test is used to estimate the consolidation settlement of clays. Since the determination of Cc from odometer tests is relatively time-consuming, empirical equations based on index properties can be useful for settlement estimation. Empirical correlations have been proposed to relate the Cc of clay deposits to other soil parameters. New polynomial models are proposed for correlation. In order to assess the merits of the proposed approach, a database containing 352 data points have been compiled from case histories via geotechnical investigation sites in the province of Mazandaran, along southern shoreline of the Caspian Sea, Iran. We compare our results involving polynomial fitting with earlier results of statistical correlation relations among Cc with other geotechnical soil properties. The predicted values using our model are checked with the measured ones to evaluate the performance of the polynomial model. The results suggest that the newly proposed approach of correlation provides a means for recognizing more efficiently the patterns in the data and reliably predicting the Cc.

Standard Penetration Test (SPT) is one of the most effective tests for quick and inexpensive evaluation of the mechanical properties of soil layers. Numerous studies have been conducted to evaluate correlations between SPT blow counts (NSPT) and the soil properties such as friction angle (). In this paper, the relation between and in situ parameters of soil including NSPT, effective stress and fine content is investigated for granular soils. In order to demonstrate the relevancy of and corrected SPT blow count (N60), a new polynomial model based on Group Method of Data Handling (GMDH) type neural networks (NN) was used based on a 195 data sets including three soil parameters. That has been recorded after two major earthquakes in Turkey and Taiwan in 1999. This study addresses the question of whether GMDH-type NN is capable to estimate based on specified variables. Results confirm that GMDH-type NN Provide an effective way to recognize data pattern and predict performance over granular soils accurately. Finally, the effect of fine content and effective overburden stress on the correlation of N60 and has been studied by sensitivity analysis.

1. Generally, prediction and calculation of the settlement of piles are complicated due to soil change during pile construction and many uncertainties inherent in the load distribution along the shaft and base of the pile. Therefore, most of the suggested relations about the settlement of piles are empirical. The results of some load tests in sand are available in reports. The empirical and semi-empirical relations have been used for the calculation of pile settlement previously by researchers. However, nowadays, calculation of pile settlement is carried out by load-transfer, elasticity theory and numerical (such as finite element) methods. Pile load test is one of the accurate methods for evaluation of pile settlement that is generally applied for important projects. In this study, settlements of piles were measured by performing compression load tests on 12 small scale cast-in-situ concrete piles in sandy soils and the obtained results were compared with the results of some other settlement calculation methods. 2. Methodology2.1. Site characterization:The area of study is located in Sorkhroud city. The soil of this region consists of coastal deposits. The groundwater table was below the base of piles. Therefore, the effect of groundwater on piles was not considered in this study. Then, laboratory and in-situ tests were carried out.2.2. Load tests on piles:The compression load tests were carried out using constant rate of penetration (CRP) method and in accordance with ASTM D 1143-81[1]. In this study, 180*80*80 cm concrete blocks were used to provide reaction for the applied load. The weight of each block was about 2.7 ton. The blocks were placed on a 6-m long beam. The piles were loaded by utilizing a 50 ton capacity hydraulic jack having a stroke of 15 cm, placed below the beam. Figs. 1-3 show the equipment.2.4. Pile settlement calculation In the present research, the settlements of piles were calculated by Meyerhof’s empirical and Vesic’s semi-empirical methods [2, 3]. On the other hand, recently, computer programs can numerically model piles and evaluate their settlements. In the numerical modeling, selection of soil modulus of elasticity is usually difficult considering soil’s elastic behavior. Therefore, different relations have been suggested for estimation of this parameter. The study shows that by performing pile load test and considering soil’s elastic behavior, the soil modulus of elasticity can be estimated using back analysis. For this purpose, the piles were numerically modeled using the computer program PLAXIS 2D and the obtained load-settlement curves were compared with the corresponding curves obtained by pile load tests.3. The load-settlement curves of piles were determined by performing pile load tests. The settlement calculation was performed for the selected piles using empirical and semi-empirical methods. The results show that empirical and semi-empirical methods are in a good agreement with the results obtained by pile load tests. Since soil behavior is modeled using Mohr-Coulomb elastic-plastic model, the settlements of piles depend on soil modulus of elasticity significantly. In this paper, soil modulus of elasticity was determined using back analysis and trial and error methods for the selected piles considering their allowable loads. 4. In this study, the settlements of piles in sandy soils were evaluated by performing pile load tests. At first, soil modulus of elasticity was estimated using finite element method. The results depict that the obtained soil modulus of elasticity is in a good agreement with Schmertmann method [4]. The obtained sand modulus of elasticity with medium relative density is about 12000 kPa. Vesic’s semi-empirical and Meyerhof’s empirical methods [2, 3] evaluate the settlements of piles acceptably which can be used for practical purposes. However, Meyerhof [2] method was more accurate. The results show that by selecting an acceptable empirical coefficient Cp in the Vesic [3] method, pile settlement can be predicted more accurately. The disturbance of soil during pile construction greatly affects this coefficient. In the present study, the empirical coefficient (Cp) was estimated 0.035 for in-situ piles constructed in slightly disturbed sandy soils with medium relative density.