جستجوی مقالات مرتبط با کلیدواژه « lime » در نشریات گروه « عمران »

Application of different stabilizers and additives such as cement, lime, and fly ash is one of the solutions for improving weak and problematic subgrade soils. In this study, a clay soil was stabilized using different percentages of cement and lime (0, 3, 5, 7 and 9%) and with different moisture content (optimum humidity level, wet side and dry side) and unconfined compressive strength (UCS) test was conducted at different curing times (7, 14, 21, 28 and 60 days). Then, the gene expression programming (GEP) method was employed to model the UCS of cement-stabilized and lime-stabilized clay soil. In the developed models, three variables of additive percentage, curing time and moisture content are used as the input variables to predict the UCS. The results of this study showed that the coefficient of determination (R2) for the model developed to predict the UCS of cement-stabilized clay soil is 0.935 and 0.926 for training and testing data, respectively. The R2 value for the model developed to predict the UCS of lime-stabilized clay soil is 0.911 and 0.884 for training and testing data, respectively. The results of the parametric study showed that the UCS increases with the increase in the percentage of cement and lime and the curing time and decreases with the increase in the moisture content.

This paper examines the behavior of untreated and treated soil with cement and lime, as well as the relationship between the design parameters of the base layer such as uniaxial compressive strength (UCS), CBR with resilient modulus. The sample selection for the triaxial test was based on the results of UCS, Brazilian tensile, wetting-drying and freezing- thawing cycles tests. In general, the addition of lime along with cement causes the tensile strength to be halved compared to the addition of cement alone, but it eliminates the volume reduction problems caused by modification with cement. Also, a large-scale dynamic triaxial test was performed on the untreated base and C7L2 specimens. In all confining pressures, the values of elasticity modulus and damping ratio of C7L2 are higher and lower, respectively, compared to the untreated soil. The data points of ratio of modulus of elasticity-axial strain of sample C7L2 are above the corresponding curves for sand and even higher than the rock ones, and its damping ratio data points are above the corresponding curve for rock samples. The average values of the modulus of elasticity increase with the increase of confining pressure and initial axial stress. Increasing the loading frequency increases the Yang modulus, shear modulus, and damping ratio, but decreases the induced shear strain on the sample. The resilient modulus (in MPa) for dry untreated soil is equal to 10*CBR and for C7L2 is approximately equal to 20*UCS or 3*CBR in soaked state or 2.5*CBR in dry state for 1.25 mm penetration.

In this study, the improvement of a clay soil contaminated with MTBE (methyl tert-butyl ether) using magnesium oxide and hydrated lime was studied. Soil contaminated with MTBE was prepared in the laboratory, then mixed with different percentages of magnesium oxide and hydrated lime. Natural soil was also mixed with the same percentages used with the desired additives. Atterberg limits, compaction, Unconfined compressive strength, and SEM tests were performed on all samples. To determine the strength, the samples were prepared by static method and tested after 7, 14, and 28 days of curing time. The results showed that magnesium oxide and lime both increase the strength and E50 and thus improve natural and contaminated soil, which is a function of the percentage of used additives and curing time. The Comparison of improvement results showed that the final strength in natural soil is higher than in contaminated soil. In addition, the comparison of the results showed that lime has less effect on soil improvement compared to magnesium oxide. The SEM results also showed that the increase in strength is due to the cement materials produced during the carbonation process, which makes the particles paste to each other and make a rigid body.

Weakness of soil in bearing capacity, lack of desirable mechanical properties, swelling properties, etc. These issues and methods required new tricks that were achieved with the evolution of engineering knowledge and the emergence of new technologies in the field of civil engineering. Different methods for soil improvement are selected according to the importance of the project, primary soil type, area of the area to be improved, local access to materials, equipment and specialized personnel, environmental factors, engineers' experiences, economic issues and time allowed to complete the project. To be. It should be noted that knowing the area and studying the types of soils that cause problems is also very necessary and important. In many cases, the soil at the construction site is not suitable for use. In this situation, this problem can be solved with appropriate solutions. One of these solutions is chemical stabilization of soil. Chemical stabilizers stabilize and strengthen soil by creating chemical reactions and altering the structure and bonding between soil particles. In this type of reaction, soil particles completely lose their nature and become a substance with new characteristics. In this article, first, in addition to getting acquainted with the types of problematic soils, the most important methods of soil stabilization and soil formation and various methods of chemical soil stabilization are examined.

Global oil production exceeds two million tons per year, contaminating the soil around oil facilities. Consequently, the soil’s geotechnical properties are modified. Since Iran is an oil-rich country with numerous refineries and oil extraction facilities, it is crucial to study the mechanical behavior of contaminated clay soils. This study examines the stabilization of oil-contaminated clay (CH) soils in the Masjedsoleyman contaminated clay soils by adding lime. To this end, laboratory tests were conducted to determine the chemical properties, Atterberg limits, standard compaction, and unconfined compressive strength (UCS) of the soil and conduct a microstructural analysis. As a result, 144 contaminated soil samples (76 mm in height and 38 mm in diameter) containing 0, 4, 7, and 10% oil were synthesized by adding 0, 3, 6, and 9% lime. The samples were subjected to unconfined strength tests and microstructural analyses after 1, 14, and 28 curing days. The results of the standard compaction test revealed that the optimum moisture content (OMC) of samples with greater oil contamination decreased by 44.4%, while their maximum dry density (MDD) increased. The unconfined compressive tests indicated that adding 6% lime resulted in the highest unconfined strength (416.6%) compared to other cases. As curing time increased for lime-stabilized samples, the unconfined compressive strength of the samples improved due to the cementation of lime particles with clay soil. The microstructural analysis results demonstrated that the 7% oil-contaminated clay soil had a laminar and discontinuous structure and numerous porous spaces between soil particles. However, longer curing times reduced the porosity and cavities in samples stabilized with different lime percentages. This confirmed the high cation exchange capacity of lime and the presence of pozzolanic reactions, which increased the unconfined compressive strength of the samples. Overall, this study demonstrates the efficacy of adding lime in stabilizing the contaminated clay and the potential use of stabilized contaminated clay as an alternative construction material and practice in the environmental protection of sites.

Due to the sharp reduction in budget of civil projects and road construction, the need to use local soil as the base is felt as a way to reduce the final cost of projects. Therefore, this research examines the characteristics of untreated and treated base soil with 3% lime, including uniaxial compressive strengths and indirect tension (Brazilian) test and resilient modulus with different curing times, as well as after performing tests of wet -dry cycles and freezing- thawing. Uniaxial and Brazilian samples with a diameter of 10.1 cm and a height of 11 cm were made in 3 layers with the same thickness and dry density of 2.2 g/cm3 and initial moisture of 6% and 8%. The results show that the addition of lime significantly increases the CBR values and shear strength of the soil. Soil treatment with lime improves its resistance against wetting-drying cycles, but it is not suitable against freezing- thawing cycles. Also, based on the tests to determine the resilience modulus, a comparison was made to determine the relationship between CBR values of untreated and treated soil with lime under hot-dry weather conditions. The results showed that the modulus values of dry untreated soil and lime treated soil are equal. The CBR value (maximum value based on penetration of 2.5 mm or 5 mm) in untreated soil is equal to the same value for penetration of 1.25 mm in lime treated soil. Therefore, for design purposes, it is recommended to use correlation relations of resilience modulus and CBR values for penetration of 1.25 mm for soil treated by lime.

The construction of different paths on fine-grained soil beds is often inevitable and, it is necessary to select and design suitable methods of soil improvement. One of these methods is shallow soil mixing with different additives such as lime and Nano-clay. These particles can improve the physical and chemical properties of the soil as much as possible and make changes on a microscopic scale. In this paper, the stabilization of fine-grained soil beds and their strength properties due to the addition of Nano-clay and lime mixing are investigated. For this purpose, the series of unrestricted compressive strength tests, Atterberg limits, density, PH and microstructural tests including X-ray diffraction (XRD) and scanning electron microscope (SEM) have been performed on the mixture of soil with Nano-clay and lime with different adding percentages at 7, 14 and 28-day curing period. The obtained results indicate that the optimum soil properties were obtained by adding 3% lime and 3% Nano-clay during the 28-day curing period and according to the results of microstructural analysis, it was found that soil resistance increased due to the formation of calcium silicate hydrated gel with reducing the voids and increasing the contacts between soil particles.

Instability of earth slopes in open channels have been always considered by hydraulic engineering. In present study, application of lime and nano lime in control of failure in side slope of earth channel has been investigated experimentally. Results showed, lining of 20% lime and 5% nano lime, increased angle of internal friction 24.4% and 35.5%, respectively and cohesion reached a value of 3.3 kPa. In feeding, for slopes of 26.5, 33, 45 and 53 degree failure occured in water levels of 560 mm, 460 mm, 460 mm and 410 mm, respectively. For seepage situation, slope of 26.5 degree was stable and slopes of 33 and 45 became instable in water level of 510 mm. Slopes of 45 degree with 10% lime and 53 degree with 20% lime were stable in maximum level of 660 mm. Potential variation behind the slope showed curve procedure with lime percent. Lining of side slop with lime and nano lime decreased seepage discharge in same water level. Also, application of lime and nano lime changed shape of failure zone and using nano lime decreased cracks in size. In feeding, without and with lime lining, curved failure surface and crack observed on slope.

The presence of organic matter in soil reduces its compressive and shear strength. It is, therefore, not suitable for construction projects. Soil strength can be enhanced by various methods. Stabilization and reinforcement are two common ways of improving soil strength parameters. In this study, the effect of polypropylene fibers on stabilized soil was investigated. For this purpose, lime and xanthan gum biopolymer were used as stabilizers, and soil was reinforced with polypropylene fibers. The experiments were performed using 1 and 3% lime, 1 and 1.5% xanthan gum biopolymer and 0.5% polypropylene fibers (by dry weight). To investigate the effect of these materials on soil strength, uniaxial compression strength and indirect tensile strength tests were conducted. The processing time of the samples was 7 and 21 days. The results showed that the addition of lime, xanthan gum biopolymer and polypropylene fibers can increase the compression strength of soil. Increasing the processing time can also increase the strength of stabilized soil, and addition of fibers leads to the improvement of soil ductility. The maximum tensile strength was observed in the sample stabilized with xanthan gum biopolymer. In the soil sample with 1% lime, the addition of fibers could increase the soil tensile strength. The results suggest that soil strength parameters can considerably be improved if xanthan gum is replaced with lime. In addition, this material is environment-friendly.

Marly soils have a relatively good resistance in the dry state, but these characteristics tend to significant degradation in contact with water (Ouhadi & Yong, 2003, Hosseini et al. 2012). The Failure to identify the behavior of clayey fine-grained soils, and especially marls, can challenge the structures constructed on such soils. Because of the extent and distribution of this type of soil in many regions of Iran, especially in southern Iran, and the high potential for the construction of hydraulic structures in these areas, it is necessary to study the behavior of these soils. Accordingly, the purpose of this study is to investigate the geotechnical characteristics of marl soils and provide a solution for improving the engineering properties of these soils.

In many coastal areas, due to lack of fresh water, there are many limitations to use in soil stabilization. On the other, due to the extension of saline water on the surface of the earth, more studies are needed on the effects of saline water on soil improvement. Therefore, in this paper, by conducting large structural and microstructural experiments, the effect of ions in sea water on the process of chemical stabilization of clay soils with lime and nanosilica has been studied. Different amounts of lime, nanosilica, distilled water and Gulf Sea water have been used to stabilize kaolinite clay .Sample clay of kaolinite has been modified with different amounts of lime and nanosilica. In this regard, soil gradation test, Atterberg limits, pH changes of samples, compressive strength variations over time have been investigated. Also, for microstructure evaluation, X-ray diffraction analysis and scanning electron microscopy have been used. Based on the results, Unconfined Compression Strength of seawater samples has improved compared to distilled water samples. Also, when the sample were modified by 6% lime, the strength of seawater samples increased by 4% compared to distilled water samples during the 28-day processing period.

Soil as a substrate of land and the foundation of civil structures is of particular importance in the development of urban areas. Some soils are classified as problematic soils due to their low mechanical resistance or high sensitivity to moisture changes, such as the Chalus coastal sand. Soil stabilization with suitable materials is one of the methods of soil improvement for problematic soils. The effect of calcium carbonate (i.e., lime) and nano-calcium carbonate (i.e., nano-lime) on the mechanical properties of the Chalus coastal sand is evaluated in this study. For this purpose, after sampling the soil from the coasts of Chalus city and conducting basic geotechnical experiments, the mixtures were prepared with different percentages of lime and nano-lime and compaction and strength tests were performed on the mixtures. The results showed that lime and nano-lime improved the mechanical properties of the soil material. However, the effect of nano-lime on the mechanical properties of Chalus sand is more significant compared to lime-sand mixtures. In addition, the increase in the lime and nano-lime content in soil mixtures resulted in an increase in the internal friction angle and cohesion.

Compact clay layers are one the most impermeable layers. Dispersivity and cracking of clay layers are among the factors that reduce the efficiency of clay and necessitate clay stabilization. Clay healing properties and the importance of self-healing cracks in clay layers as one of the characteristics and attributes of clay in recent years have been studied. In this research, the self-healing performance of clay layers due to the addition of lime to the clay materials of Gordyan dam borrow pit (Gargar) was investigated. For this purpose, two dispersive (S2 and S3) soil samples (ND3 and ND4) were investigated by adding lime to the extent 0.25, 0.5, 1 and 2%, and Double Hydrometer, Atterberg limits and Pinhole tests of dispersivity and self-healing were investigated. The results showed that by adding 1% of lime to clay, the range of plasticity index increased and the discharge rate of the pinhole test for both samples was 28% and the final diameter of the sample for both samples decreased by 67%, indicating an improvement in self-healing process and a reduction of dispersivity and becoming non-dispersive soil (ND1). The results also showed that pinhole testing has reliable and more accurate results than other tests in determining soil dispersivity.

Due to the limited soil resources and population increase, the use of contaminated or problematic soil is inevitable. There are different methods to improve the geotechnical properties of clay soils. One of the ways is to stabilize the soil with stabilizers such as Portland cement and lime. Investigation of the combined effect of organic pollutants under the influence of stabilizers (Portland cement (I) and lime) on Kaolinite clay using modified Proctor and CBR experiments constitutes the present research framework. The maximum unit weight decreased with an increase in Anthracene content while its variations were strongly dependent to the Glycerol content. The maximum of dry unit weight and a minimum of optimum water content occurred at a glycerol content of 6%. Based on test results, it was found that the increase in strength of clean Kaolinite using 6% of Portland cement is equivalent to that of 30% lime. It was also found that the contaminants decrease the strength of kaolinite; however, both stabilizers increase it. The effect of Portland cement on the strength of the specimens contaminated with Anthracene was better than that of lime and the effect of Portland cement and lime on the improvement of samples contaminated with Glycerol was considerable.

Problematic soils are sometimes needed to be used in dam construction. This usually occurs when appropriate materials are located far from the dam site and cannot be used for economic reasons. In this case, available problematic soils (e.g., dispersive soils) can be utilized after amendment. The amended soil is supposed to not show its problematic behavior before treatment. It is conventional to treat dispersive soils by the addition of the most used one being lime. However, the addition of lime may cause a considerable reduction in the plasticity index of the mixture that, in turn, can produce other problems. An important consequence caused by the low plasticity index of the amended soil used in earth dams is an arching phenomenon, which can finally lead to failure of the dam. In this research, lime and bentonite are used to amend dispersive soil samples taken from Mirzakhanloo-Dam site located in Zanjan Province. The aim was to treat the dispersivity of samples and, also, to avoid the arching problem. For this reason, a set of laboratory tests was conducted on the prepared samples. Lime was used in samples with amounts of 0.6, 1, 1.5, 3, 5 percents of dry weight of the soil. Moreover, bentonite was used with amounts of 3, 5, 10, 15, and 20 percents. Pinhole test, double hydrometer test, crumb test, and chemical test were performed on the pure soil and additive-soil samples to evaluate the dispersivity of soil samples. Moreover, Atterberg limits, particle size, and hydraulic conductivity of samples were examined. The result showed that the combination of 5% lime and 15% bentonite can solve the problem such that, on the one hand, the dispersivity of soil is treated and, on the other hand, the arching problem is controlled. Almost all previous research studies have recommended the lime and other additives for the amendment of dispersive soils regardless of the arching problem. This paper strongly recommends considering this problem. Since the creation of a small crack in dams can lead to failure with regard to the piping problem, it is important to carefully assess the outcome of soil improvement programs and control the plastic index of the amended soil.

The type and percentage of clay minerals in the soil as well as the pore fluid properties of double layer are the important parameter that influence on the strength and behavioral properties of the clay Soils. In this regard, clay soils are highly sensitive to changes in environmental conditions and their behavior and strength parameters will be affected by many factors such as soil disturbance, water content, loading and drainage conditions, loading rate, temperature, etc. Therefore, one of the important parameter that affect the results and efficiency of lime stabilized clay soil samples and optimum lime content (OLC) is the type and percentage of clay minerals in the clay soils. In common, methods of lime stabilization, the most effective innate factor of clay minerals in the soil is not considered comprehensively. So it has been observed that the results of various test methods are completely in conflict with each other. The accuracy of the test results depends on the simultaneous consideration of chemical and mineralogical properties of the soil. In this research, to study the micro and macro-structure of stabilization process of lime stabilized clay soil samples, different combination of bentonite and kaolinite clay samples with different percentage of lime were studied experimentally. Studied samples during the time of 7 and 28 days were cured and uniaxial test were performed on them. Then Scanning Electronic Microscope (SEM) images were done to investigate the effect of the percentage and clay mineral type on the lime stabilized clay samples. The results of this research indicate that lime stabilization increase the UCS of soft clay soils about 2 to 10 times. Also, the interaction of soil-additive, the pozzolanic reaction progresses over the time, the optimum mixture of soil and lime as well as the stabilization efficiency, significantly dependent on the type and percentage of clay minerals in the soil.

Soft clayey soil generally has high compressibility and low strength. Presence of this soil type in the site of ‎civil projects can always be a challenge for construction issues. Soil stabilization is one of the useful ways to ‎improve problematic soils. Cutter Soil Mixing (CSM) is almost a new method for deep stabilization. This ‎experimental study, investigate the effect of different depths on soft clay ‎properties which stabilized by CSM ‎method. To simulate various depths and related surcharge pressures, new devices were designed, modified ‎and used for laboratory tests. Moreover, mixture of blast furnace slag and hydrated lime slurry was used in this ‎method for the first time. The samples were cured for 28 and 56 days ‎under various surcharge pressures, which actually represent different depths. The results revealed that by increasing the depth, mositure content and saturated/dry densities of the samples were decreased and increased respectively. In addition, by ‎passing the critical depth, fewer changes were obsorved in the moisture contents and saturated/dry densities of the samples. Finally, the strength parameters of stabilized samples were icreased significantly.

Soil pH is a measure of the acidity and alkalinity in soils, ranging from 0 to 14 that measured in a slurry of soil mixed with water. Soil pH normally falls between 3 and 10, with 7 being neutral, acid soils have a pH below 7 and alkaline soils have a pH above 7. Ultra-acidic soils have pH value less than 3.5 and very strongly alkaline soils have pH value more than 9 which are rare. Extremes in acidity or alkalinity may affect mechanical behaviour physical properties of soil. Recently, the rapid development of cities and the industrial revolution have caused enormous environmental impacts and become a serious environmental problem. About 80% of the pollutants in the atmosphere, including suspended particles and gases, result from vehicular traffic and industrial activities. Precipitation acts as a significant natural cycle to clean up atmospheric pollutants such as gases and particles in the air. The major sources of acid water are strong presence of SO2 and NOx gases in the atmosphere. One of the most important effects of acid water is its effect on soil, including washing nutrient cations, releasing toxic elements, and acidifying the soil. Also, acid mine drainage and the contaminants associated with it, is a common occurrence in waste dumps of mining sites results in acidic conditions with a pH of less than 4 develop over time. On the other hand, mineral deposits, over liming in some parts of the land and the use of limestone to improve the different soil natural and control the pH in waste dumps leads to alkaline conditions (pH more than 7) at mine sites. One of the most important effects of air pollution is acid rain. The increasing expansion of cities, the rapid growth of urbanization and the industrial revolution have caused enormous environmental impacts in and around cities. Industrial activities, production of energy and fuel, the use of fertilizers and pesticides cause significant amounts of contaminants to the atmosphere. The entry of metal contaminants and acidifying compounds such as sulfur, nitrogen compounds or their reaction to the atmosphere in the rain will increase the acidity of the rain which can change the quality of atmospheric precipitation. In general, it can be stated that the meaning of acid rain is a rain that has a pH of less than 5.5 which is a lower natural pH. In the current study, the effect of acid rain on the mechanical behavior and physical properties of lime stabilized sand with respect to the eastern regions of Isfahan has been investigated. At first, the various lime content was added to the soil and the specimens were tested after treatment and saturation under various pH values. The results show that adding lime increased the optimum moisture content, shear strength of the specimens, the cohesion and the friction angle of the soil. On the other hand, reducing the pH value results in continuously decreasing the shear strength parameters of the soil specimens. Finally, based on the scanning electron microscopy (SEM) image from the specimens, the effect of pH and lime content on the bonds between the sand grains was investigated.