Showing 75 results for Soil
Mr. Seyed Ali Ghaffari, Prof. Amir Hamidi, Dr. Gholamhossein Tavakoli Mehrjardi,
Volume 14, Issue 5 (12-2020)
Abstract
This paper investigates response of triangular shell strip footings situated on the sandy slope. A series of reduced-scale plate load tests were conducted to cover different parameters including three shell footing types with different apex angles in addition to a flat footing, four different distances for strip footings from the crest of the slope namely “edge distance” and reinforcement status (unreinforced and geotextile-reinforced statuses). Bearing capacity of shell footings adjacent to crest of the slope, bearing capacity ratio, shell efficiency factor, influence of apex angle on settlement of footings and the mechanism of slope failure are discussed and evaluated. Also, empirical equations for determination of the maximum bearing capacity of triangular shell strip footings are suggested. As a whole, it has been observed that decrease of shell’s apex angle as good as increase of edge distance could significantly improve the bearing capacity. However, as the edge distance increases, the effect of apex angle on the bearing capacity got decreased. Also, it was found out that the beneficial effect of reinforcement on the bearing capacity decreased with increase of the edge distance. Furthermore, the efficiency of shell footings on bearing capacity was attenuated in reinforced slopes compared to the unreinforced status.
Mr. Mohammad-Emad Mahmoudi-Mehrizi, Prof Ali Ghanbari,
Volume 14, Issue 5 (12-2020)
Abstract
The use of piles, helical anchors and, in general, helical foundations has considerably increased in the last 30 years. The adoption of this technology in the international and domestic codes of each country, as well as in research and studies, and, finally, the publication of numerous books and papers in this area, and the existence of manufacturers’ products, committees, and contractors of this technology has contributed to its expansion and development. However, such methods have progressed at a very slow pace in many countries, especially in developing countries. This paper attempts to assess the global advancement of the helical foundations by reviewing 292 papers from 1990 to 2020 and comparing the related research findings. This will help clarify the issue and determine the scope of technological progress. On the other hand, collecting valuable papers in this area will make it easier for researchers to make further research. Subsequently, the characteristics of this technology are highlighted and the reasons for its lack of progress in the developing countries are addressed. For this purpose, a questionnaire is sent to researchers, developers, designers, and contractors of the geotechnical projects. The purpose of this questionnaire is to specify the type of existing projects, the soil type of project site, the degree of familiarity with the helical foundation technology, the reasons for not using this method and the solutions available to expand and develop this method. Finally, there are suggestions to develop this approach and the issues that need further research.
Zahra Hoseinzadeh, Ebrahim Asghari-Kaljahi, Hadiseh Mansouri,
Volume 15, Issue 2 (9-2021)
Abstract
The soil of the Arvand free zone in the north of Khorramshahr is fine cohesive and cannot be used in earth works. On the other hand, suitable materials for this purpose (coarse-grained soils) are located at the farther distances which a considerable cost requires. In this regard, it is trying to improve the soil with lime and furnace steel slag. This study is focused on improvement of the fine-grained soil by adding various contents of lime and furnace steel slag. For this purpose, after sampling and performance of compaction tests, different amounts of slag (10, 20 and 30% by weight of dry soil) and lime (2, 4 and 6% by weight of dry soil) were added to the soil and after curing for 28 days, the effect of additives on the physical and mechanical properties of soil was investigated by using several tests such as Atterberg limits, compaction, uniaxial compressive strength (UCS) and CBR as soaked and unsoaked. Based on USCS classification the study soil is CL, its plasticity index is about 25% and sulphate ion content is more than 0.5%. Experimental results show that by adding slag and lime at different contents to soil, mechanical properties of soil improve dramatically, so plastic index of soil decreased and UCS and CBR has been increased. Also, the maximum dry unit weight of soil increases and the optimum moisture content decreases. The test results also indicate that the effect of lime on soil is higher than slag and the effect of slag for less than 35% is not considerable, however the test result of unsoaked CBR show that the bearing of soil increase in the more than slag content 20% is significant. According to the previous studies, due to the relatively high sulphate ion content in the soil, the use of lime alone is inappropriate and the slag can only physically improve soil conditions but also chemically prevent the formation of large volume minerals (like Ettringite) by the reaction of lime with soil sulphate ion.
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Alireza Sadeghabadi, Ali Noorzad, Amiali Zad,
Volume 15, Issue 2 (9-2021)
Abstract
Expansive soils contain clay minerals such as compacted kaolin which are widespread in nature. Displacements of this type of soils are associated with matric suction and degree of saturation. To determine the in-situ characteristics, necessary measures may be required to deal with the possible failure related to this type of soil. Different constitutive models of unsaturated soils have been considered the subject of many recent researchers (Sheng et al. 2004; Wheeler et al. 2003; Nuth and Laloui 2008; Zhang and Lytton 2009 a, b 2012). However, those constitutive models are generally complicated that are not properly implemented in computer programs for practical applications. The Barcelona Basic Model (BBM) is one of the geomechanical constitutive models to capture the elastoplastic behavior of unsaturated soils.
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Shaham Atashband, Mohsen Sabermahani, Hamidreza Elahi,
Volume 15, Issue 2 (9-2021)
Abstract
In coastal industrial areas, in addition to the presence of loose soil, sulfate attack on soil improvement elements, such as soil-cement, is a double problem. Generally, the use of type V cement is recommended as one of the methods to reduce the detrimental effects. Considering the limited resources of this type of cement, firstly to determin the relationship between the cement content and the strength obtained in sulfated environments is one of the important engineering question in this field and secondly, as an alternative option, the use of type II cement which is more available, is suggested to use in combination with suitable additives. The present study pursues the above two goals by making cylindrical soil-cement specimens with sand, water and Portland sulfate resistant cements. Sodium sulfate is used as the sulfate in soil and water. In the research, first of all, the relation between type V cement content and unconfined compressive strength of soil-cement is obtained at 0% to 5% sulfate concentration, which results in a cement content of 400 kg/m
3 completely limited the sulfate attack effects in a sulfate concentration of 2%. Secondly, the combination of type II cement with barium chloride and hydroxide was tested. The related results show that the combination of type II cement with barium chloride and hydroxide had higher strengths, about 2.7 to 3.3 times, respectively (in 362 days), than the soil-cement containing type V cement.
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Volume 15, Issue 3 (12-2021)
Abstract
Clayey soils in terms of sharp reduction in strength and swelling ability as a results of water and moisture absorption, it is considered as one of the most problematic soils in civil engineering and construction works. Nowadays, Nano materials such as Nano clay are used to improve and stabilize of clay. On the other side, the increasing volume of municipal waste and residues materials especially debris of building destruction have caused many problems in mega cities such as environmental issues due to incorrect disposal of waste material. Main propose of this research is study of possibility in effecting Nano clay and limestone powder mixture for improve geotechnical properties of Kuye Nasr clayey soil in Tabriz City. In this study, Nano clay and limestone powder in both separate and combined conditions with 5 and 10 percentage are mixed with clay. Curing of stabilized specimens have been performed in 7, 14 and 28 days. For evaluating geotechnical behavior of mixture materials some tests were performed such as Atterberg limits, Compaction, uniaxial strength and direct shear (in 1, 2 and 3 kg/cm2 vertical stress). Results show that the simultaneous effects of 5% Nano clay with 10% limestone powder with 7 days curing period in ambient temperature conditions in clay reduced plasticity index by 72%, improved graining skeleton structure, reduced void ratio of inter grains and increased shear strength by 33%.
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, , Morteza Jiriaei Sharahi,
Volume 15, Issue 4 (12-2021)
Abstract
Soil stabilization and reinforcement has long played an important role in civil engineering, especially in geotechnics, and over time and the need for a more robust and stable ground to withstand gravity and higher shear forces, has become particularly important. Also, in recent years, with the entry of the environment into the construction industry, with the aim of reducing the adverse effects of industrial waste and construction waste on people's living environment and preserving the environment for the future, in many cases reduces the economic costs of projects. In this research, granular soil is reinforced in two loose and semi-dense states using a waste material called ethylene-vinyl acetate (EVA). The experiments were performed without adding moisture, by weight percentage method and using CBR device. The results show that soil resistance increases significantly with the use of these additives and its effect on soil increases with decreasing soil specific gravity. Also, the optimal amount of additives in loose and semi-dense state is 2% additive and 1% additive, respectively.
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Prof. Amir Hamidi, Mr. Mahdi Sobhani, Ms. Farzaneh Rasouli, Ms. Marjan Sadrjamali,
Volume 16, Issue 1 (5-2022)
Abstract
The goal of this study was improvement of sandy soil using a combination of polystyrene foam container waste and Portland cement. For this purpose, Babolsar sand was used as the base soil. Strips of disposable polystyrene foam container waste in “chips” of 50 ´ 5 mm and 50 ´ 10 mm were added to the soil at 0.0%, 0.1%, 0.2% and 0.3% by weight along with 3% Portland cement at a relative density of 70%. All samples were cured for 7 days under saturated conditions and then tested using a large-scale direct shear apparatus. The results showed that, in both cemented and uncemented samples, the addition of foam chips increased the cohesion and internal friction angles, which increased the shear strength of the soil. At higher percentages and using larger-sized foam chips, the shear strength increased even more. In uncemented samples, the stiffness did not change with the addition of foam chips, yet the final dilation of the samples decreased. In cemented samples, both the stiffness and softening behavior after the peak strength point decreased. The final dilation of the cemented samples increased at higher foam chip contents and for the larger sized chips. The results of numerical analysis showed that the use of foam chips increased the safety factor of a slope improved in this manner. It also was found that the foam chips with a lower length-to-width ratio had a greater effect on increasing the safety factor of the tested slopes.
Hossein Sarbaz, Ali Neysari Tabrizi,
Volume 16, Issue 4 (12-2022)
Abstract
In recent years, the use of environmentally friendly microorganisms and biopolymers in geotechnical activities, especially in soil improvement, has received much attention. This is in order to reduce the harmful environmental effects caused by the use of traditional and industrial materials, including cement. Therefore, it seems to be necessary to study the effects of environmentally friendly biopolymers from different points of view, including environmental issues, soil erosion and the factors that influence the geotechnical parameters of the different deposits. The purpose of this article is to review the studies carried out on the use of guar gum. As a green additive from an environmental point of view and the factors that influence the mechanical parameters of soils treated with this biopolymer. The advantages and disadvantages of guar gum from an environmental point of view, as well as the effects of this additive on different soils, are the subject of discussion. Geotechnical parameters such as the unconfined compressive strength, the shear strength, the erosion resistance and the durability of the soils treated with guar gum will be evaluated. The influence of the guar gum parameters in relation to the concentration of the biopolymer guar gum, the moisture conditions, the temperature and the processing time will then be discussed. Finally, the potential opportunities and challenges for the use of guar gum in the geotechnical field will be presented.
Aylar Hosniyeh, Dr Rouzbeh Dabiri, Alireza Alizadeh Majdi, Elnaz Sabbagh,
Volume 16, Issue 4 (12-2022)
Abstract
Silty soils containing sodium content, known as salty silty soils, are classified as another type of problematic soil. When this type of soil comes into contact with water, it can swell and diverge, leading to settlement and deformation. Considering that a significant part of the Urmia Lake basin and the Tabriz plain consists of sodium-rich fine soils, the aim of the project is to improve the quality of the soils. Therefore, one of the main objectives of this study is to assess the sediments within the lake bed in order to reduce erosion and to evaluate the possibility of improving and stabilizing the sodium saline silty soils in the area using the geopolymerization technique. To achieve this, pumice material with pozzolanic properties was separately mixed with the soil under investigation at weight percentages of 3%, 5% and 7%, together with a calcium hydroxide solution as a catalyst at concentrations of 2%, 5% and 7%. The samples were then cured for one day. Laboratory tests, including compaction, uniaxial compressive strength, direct shear, and consolidation, were carried out to evaluate the geotechnical behavior of the improved soil. The results obtained indicate that the combination of 3% pumice with 2% calcium hydroxide increased the uniaxial compressive strength of the stabilized sample by 1.32 times after one day of curing. In addition, the mixture of 7% pumice with 2% calcium hydroxide significantly improved the internal friction angle by 20 times. Finally, the combination of 7% pumice with 2% calcium hydroxide reduced the value of free swelling potential by up to 86%.
Dr. Ehsan Pegah,
Volume 17, Issue 1 (3-2023)
Abstract
The ratios of elastic shear stiffness anisotropy and fabric anisotropy in granular soils are of very important characteristics in soil mechanics, which can influence directly lots of geotechnical engineering attributes. The shear stiffness anisotropy in a soil mass is directly related to the soil fabric anisotropy, which in turn has a fundamental contribution in variations model of shear stiffness anisotropy ratio. The main objective of this study is to evaluate the variations ranges of shear stiffness and fabric anisotropy ratios in granular soils by developing a novel approach for estimating fabric anisotropy ratio from soil grading and particles shape properties. By presuming cross-anisotropy, the anisotropic shear stiffness values of 1042 conducted tests on 200 distinct sandy and gravelly soil specimens from 43 various soil types of diverse sites throughout the world were acquired from literature. Those were then integrated with their associated void ratios, stress conditions, grading parameters and particles shape specifications to produce a comprehensive database of anisotropic shear moduli with respect to testing conditions. The collected data were analyzed, from which the shear stiffness and fabric anisotropy ratios could be calculated for examined geomaterials. The resulting values for fabric anisotropy ratio were then depicted versus grading and particles shape information to inspect the level of dependences through deriving the respective correlations. The findings of this study may serve as a suitable technique to obtain first-order approximations for fabric and shear stiffness anisotropies from soil grading and particles shape characteristics.
Ehsan Pegah,
Volume 17, Issue 2 (9-2023)
Abstract
The ratios of elastic anisotropy in cohesionless soils are always of substantial importance in respective analyses to the geotechnical and geological engineering projects. These ratios are raising from the available discrepancies in anisotropic elastic parameters ascribed to the different directions and planes of soil mass. The major objective of this study is to recognize the variations range of anisotropy ratios resulting from anisotropic shear and Young’s moduli for a variety of cohesionless soils followed by assessing the potential relations among these two anisotropies. To this end, by assuming the transversely isotropy in cohesionless soils, the anisotropic elastic constants from 266 conducted laboratory tests on 37 various soil specimens relating to 10 different sands were derived from conventional triaxial and seismic waves laboratory tests coupled with the numerical testing results in literature. By sorting the collected data and subsequently their analyses, at the first stage, the values of shear and Young’s moduli anisotropy ratios were calculated for the studied soils. Furthermore, by plotting the anisotropy ratios in several joint panels and performing a series of regression analyses on the resulting values, the possible dependencies were inspected between these two anisotropies. At last, the indicative equations among shear and Young’s moduli anisotropies were developed with insistence on use of which instead of the former similar relations in literature.
Dr Masoud Amelsakhi, Eng Elham Tehrani,
Volume 17, Issue 4 (12-2023)
Abstract
This research is a laboratory study to improve the geotechnical properties of sandy soils. Concrete waste with a grain size of 1.2 to 1 inch was used for this purpose. The effect of using concrete waste at 0, 10, 20 and 30 weight percent on dry sandy soil in two loose and dense states was investigated. Based on the results of the direct cutting test, the addition of concrete waste has increased the shear strength and the internal friction angle of the soil; The loose samples made with ٪30 of concrete waste had the greatest effect, so adding ٪30 of concrete waste to loose sand increased the internal friction angle of the soil by ٪32 and the shear strength by ٪42 Similarly, adding ٪10 of concrete waste to dense sand increased the internal angle of friction of the soil by ٪4 and the shear strength by ٪6.
Ms Roghayeh Hasani, Dr Ebrahim Asghari-Kaljahi, Dr Sina Majidiana,
Volume 18, Issue 2 (9-2024)
Abstract
With the expansion of the petroleum industry and the aging of facilities and pipelines, oil spills are becoming more frequent. In addition to environmental impacts, oil spills can cause changes in the plasticity and dispersivity of soils. To investigate the potential for dispersion in fine-grained soils due to oil leakage, soil samples were collected from the Shazand Refinery area in Arak and mixed with 0, 5, 10, 15, and 20% by weight crude oil. Specimens were prepared at the maximum dry density obtained from the Proctor compaction test and, after curing, pinhole and double hydrometer tests were conducted. The results of the mentioned tests showed that the fine-grained soil tends to disperse with the addition of up to 15% oil, and this dispersion increases with further increases to 20%. Changes in the soil fabric with increasing oil content were investigated using scanning electron microscopy (SEM) images, and the results showed that the dispersion of soil particles increased with increasing oil content.
Dr Masoud Amelsakhi,
Volume 18, Issue 3 (12-2024)
Abstract
Tunnels behave differently under seismic conditions due to their geometric shape, geotechnical parameters and installation depth. Although tunnels are less damaged compared to surface structures, they are still damaged during earthquakes. Various experiences have proved this matter, so researchers are concerned to study the seismic behavior of tunnels. In this research, circular tunnels are discussed under static and pseudo-static loading. In addition to different pseudo static earthquake factors, internal soil friction angle, soil behavior models, sliding and non-sliding of tunnel wall are also studied. Three different soft, medium and stiff soil conditions are studied. Some results show that in all three soil conditions and two soil behavior models, Mohr-Coulomb and hardening soil, the horizontal displacements increase due to the increase of the pseudo static earthquake factor. It should be noted that softening of the soil increases the horizontal displacements.
Dr Ali Ghanbari, Fatemeh Mirdar,
Volume 18, Issue 4 (12-2024)
Abstract
Examining the seismic response of the ground surface and its impact on structures due to topographic effects and soil-structure interaction (TSSI) is highly significant. If the site has sloping topography, the importance of this study is further amplified, and the slope effect on soil-structure interaction must be considered. This research uses Loma Prieta (1989) earthquake records to analyze the seismic response of a 5-story concrete building located 5 meters from the crest of the slope for four angles: 15, 30, 45, and zero degrees (SSI), using 3D numerical analysis. Modeling was conducted with MIDAS GTS NX software for both TSSI and SSI systems. An elastic model and an HSS model were used for the building and soil, respectively. The seismic response of the building was evaluated by comparing maximum lateral displacements, base shear forces, inter-story drifts, and horizontal accelerations in TSSI and SSI analyses. As the slope angle increased from zero degrees (SSI) to 15, 30, and 45 degrees (TSSI), the average lateral displacement of the floors increased by 44%, and the average maximum horizontal acceleration increased by 21%. Additionally, with the slope angle increasing from zero degrees (SSI) to 15, 30, and 45 degrees (TSSI), the average ratios of inter-story drift and maximum base shear force increased by 14% and 21%, respectively.
Amir Khoshgoftar, Mahdi Khodaparast,
Volume 18, Issue 5 (12-2024)
Abstract
Soil contamination by petroleum contaminants and their derivatives has harmful effects on the soil environment. The structure and geotechnical parameters of the soil will change as a result of the interaction between the contaminant and the soil. The double layer thickness of the clay will change, and the structure of the clay soil will become similar to that of the granular soil. In the present study the effect of contamination by burnt-oil waste from refineries on the compaction and resistance behavior of clayey sand soils was investigated. The geotechnical characteristics of soil types contaminated with different percentages of hydrocarbons from previous research were also reviewed and analyzed. The primary effects were decreases in the internal friction angle, California bearing ratio and permeability of the soil and increases in the cohesion and Atterberg limits of the soil. The shear strength of the contaminated soil did not show a definite or constant trend of change. When contaminated with acidic sludge, despite an increase in the cohesion of the soil, a decrease in the internal friction angle caused a decrease in the shear strength. When contaminated with dirt filter residue, the shear strength of the soil increased with the substantial increase in cohesion, despite a decrease in the internal friction angle.
Soroush Mahdavian, Navid Rashidi, Ali Raeesi, Jamal Abdullahi,
Volume 19, Issue 1 (6-2025)
Abstract
Clay soils typically have low strength and a high swelling percentage. They are considered as problematic soils in Civil Engineering projects. This research study examined the effects of magnesium chloride (MgCl2) solution on the clay soil improvement through conducting laboratory experiments. The experimental program included Atterberg limits, compaction, swelling, unconfined compression strength (UCS) and Scanning Electron Microscopy (SEM) tests. Available clay soil in the Lab was mixed with MgCl2 solution at weight percentages of 3%, 5%, 7% and 10% Samples for the swelling and strength tests were made using thestatic compaction method. The moisture and dry unit weight of the prepared samples were the same as those of thecorresponding compaction curves. The strength test results showed that the final strengths of the samples with 3% MgCl₂ at 7-, 14-, and 28-day curing times were 1401, 2018, and 1848 kPa, respectively. The results also showed that a reduction in strength of the samples occurred with more than a 3% solution of MgCl₂. For samples with 10% MgCl2 solution, the strength decreased until 14 days of curing time, but increased thereafter. Additionally, the results indicated that the reduction in swelling percentage compared to natural soil was 4.95%, 3.98%, 2.8%, and 3.9% for samples with 3%, 5%, 7%, and 10% MgCl₂, respectively, showing that the reduction in swelling depends on the MgCl₂ percentage. Additionally, the SEM results showed that the improvement in the soil was due to chemical reactions between the soil and MgCl₂.
Ehsan Pegah,
Volume 19, Issue 1 (6-2025)
Abstract
Accurately quantifying the anisotropic elastic parameters of in situ soils is essential for many geotechnical and geological engineering studies. This research introduces an innovative geophysical field technique for assessing these parameters in situ by utilizing the directional variations of P-wave and S-wave velocities. Assuming cross-anisotropy in the soil layers at the test location, it was shown that P- and S-wave propagation velocities along different orientations and planes can be effectively measured through a combination of seismic refraction and downhole surveys. The refraction data were analyzed using Seismic Refraction Tomography (SRT), Multichannel Analysis of Surface Rayleigh Waves (MASW), and Multichannel Analysis of Love Waves (MALW) to estimate the horizontal P-wave velocity (VPH), vertical S-wave velocity (VSV), and horizontal S-wave velocity (VSH), respectively.Moreover, the vertical and oblique P-wave velocities (VPV and VPθ) were identified by evaluating the travel times and distances of wave signals obtained from downhole tests. These velocity measurements were then incorporated into advanced equations formulated from elastic wave propagation theory, facilitating the computation of elastic parameters at the site. To evaluate the accuracy and efficiency of the proposed approach, the obtained results were compared with corresponding laboratory measurements, revealing a satisfactory level of agreement between the two datasets. The proposed methodology offers a practical means for in situ assessment of cross-anisotropic elastic properties in near-surface geomaterials using field-based seismic techniques.
Dr Seyed Ali Asghari Pari,
Volume 19, Issue 6 (12-2025)
Abstract
Various factors influence earth dams' stability and flow rate, including geometric characteristics, material permeability, and upstream water height. Understanding unsaturated soil behavior in earth dams is crucial, necessitating the application of unsaturated soil mechanics principles due to the complexities involved. This study investigates the effect of Soil-Water Characteristic Curve (SWCC) parameters on the slope stability of an earth dam under steady-state and rapid drawdown conditions. The findings reveal that SWCC parameters significantly influence water flow and slope stability. Additionally, considering unsaturated unit weight can improve slope stability under varying conditions.
