Poisoning of soil and groundwater resources is among the current major environmental issues world... more Poisoning of soil and groundwater resources is among the current major environmental issues worldwide. One effective way to stop the spread of pollutants and improve soil’s capacity for adsorption is to use natural and inexpensive adsorbents. In this respect, the soil environment can be improved by the addition of zeolite and rice husk ash (RHA). This study examined the behavior of a sand mixture with 20% kaolinite or 20% bentonite in both uncontaminated and contaminated [with Pb(NO3)2] states. Two classes of clay minerals were considered: kaolinite and bentonite. The impact of the adsorbent on the strength performance of the contaminated soil was examined by removing 10% of the clay particles and replacing them with zeolite or RHA adsorbents. Triaxial dynamic and bender element tests were carried out to explore the dynamic behavior of contaminated soils and the liquefaction resistance of the samples polluted with Pb(NO3)2, respectively. The results show that by reducing the heavy metals concentration Pb(NO3)2, the ultimate strength of sand mix with 20% bentonite increased by 40%–50%. In addition, the ultimate strength increased in polluted and noncontaminated situations by adding zeolite or RHA to the soil. The results of triaxial dynamic tests demonstrated that liquefaction resistance was reduced by increasing the contamination concentrations in both the mixes without and with adsorbent. Furthermore, the initial/maximum shear modulus (G0/Gmax) decreased as the adsorbent content increased in both contaminated and noncontaminated states.
Loess soils have always been among the most problematic soils, according to engineers. Due to the... more Loess soils have always been among the most problematic soils, according to engineers. Due to the sensitivity and vulnerability of this soil type, researchers are constantly looking for different solutions to improve and stabilize this soil using different methods. In the present study, a mixture of lime and rice husk ash (LRHA) was used to modify the loess soil of the Golestan province, Iran. Lime and RHA were mixed in a ratio of 2:4 and with different contents of 2.5, 5, 7.5, 10 and 12.5% of the dry weight of the soil. To study the effect of curing on the strength properties, the samples were cured and tested for 7, 18 and 28 days. Atterberg limits, modified Proctor, unconfined compressive strength (UCS) and scanning electron microscope tests (SEM) were performed. It was found that increasing LRHA content increased the value of UCS at different curing times, such that UCS increased about five times by the addition of 5% LRHA to the loess at the end of 28 days. As the curing time i...
Abstract Electro-osmosis is a phenomenon describing the motion of liquid adjacent to a charged su... more Abstract Electro-osmosis is a phenomenon describing the motion of liquid adjacent to a charged surface under the influence of an electric field. Electro-osmosis is considered as an efficient soft soil improvement technique. In this study, series of laboratory tests were performed utilizing graphite and stainless steel electrodes under three levels of voltage gradients for 28 days using the soil from north of Iran to investigate the effect of various parameters on electro-osmotic and geotechnical properties. Moreover, the microstructure and chemical analyses of the soil before and after treatment gave an in-depth perspective to underlying mechanism of this process. Water drainage which has the most important effect on consolidation of soils, terminated after a few days. The termination time for stainless steel is smaller than graphite and the whole drained water volume is larger in case of stainless steel compared to graphite. The strength around the anode is larger than that of the cathode zone and the stainless steel electrode induced larger strength than the graphite electrode. The SEM images exhibited the agglomeration of the soil after electro-osmosis treatment, and some precipitation was also identified, which was attributed to iron based compounds. Chemical analysis illustrated that the concentration of calcium ions decreased around the anode and increased near the cathode while Fe and Al amount did not change significantly, implying the ion exchange and ion migration due to the electro-osmosis process. Additionally, the stainless steel electrode introduced iron and chrome ions to the soil, which affected structure and chemical distribution of the ions.
The performance of a combined Anchored Earth and Geotextile system of earth reinforcement as prop... more The performance of a combined Anchored Earth and Geotextile system of earth reinforcement as proposed recently (Singh & Finlay, 1986) was studied, and is reported in this paper. Semi-Z shaped mild steel model anchors alternating with a synthetic geotextile in depth were used in a test box and loaded. The end results of the tests presented in the paper demonstrate that the combined system is characterized by a fairly high rigidity and high holding capacity. For the covering abstract of the conference see IRRD 836241. (Author/TRRL)
Uncertainties and inherent variability of soil strength parameters, scatter in the data or system... more Uncertainties and inherent variability of soil strength parameters, scatter in the data or systematic testing and
modeling discrepancies are commonly found in geotechnical problems. The same is true for soil nailed walls as an example
of geotechnical problems, which is similar to rock bolt method being used for reinforcing rock mass. Because of these
issues, engineers cannot evaluate and identify the rate of available risk by deterministic methods such as limit equilibrium
method. In probabilistic methods, most of the existing uncertainties in analysis processes can be considered. This research
studies uncertainty in soil nail walls based on a case study and rock slope excavation using Monte Carlo simulation. The
results were then compared with those of the deterministic method.
Loose sandy soils can be strengthened by reinforcing. Micro-reinforced earth has ductility, enhan... more Loose sandy soils can be strengthened by reinforcing. Micro-reinforced earth has ductility, enhanced elastic stress limit, suitable for analysis by linear methods of analysis, can be idealized to be homogeneous and is ideal for use in earthquake engineering. Free & forced vibration tests were carried out on large 1.5 m x 0.75 m x 0.9 m high reinforced embankments on shake table excited by D.C, motor-oscillator drive. Plane strain conditions were created in lab. From tests, strain dependent shear modulus were obtained. Response computed fron dynamic 2D FEM analysis of test embankments by idealising them with 1-layer and 2-layer system agrees well with response based on test data. This suppots idealisation of microreinforcd earth to be homogeneous.
Journal of Structural Engineering and Geo-Techniques, 2015
In this paper a laboratory study has been carried out on the effect of changing the type of soil ... more In this paper a laboratory study has been carried out on the effect of changing the type of soil filling cylindrical reinforcing elements from SM to GM on behavior of sandy soil. In this study the primary tests for evaluation of the impact of reinforced sand and gravel columns with diameters of 5 cm and heights of 15 cm subjected to vertical stresses of 50, 100, and 150 KPa were carried out in a large-scale direct shear apparatus (300×300×150 mm). Results showed that the shear stress and settlement of the reinforced sample with geogrid and a gravel column increases by 45.4% and decreases by 23.9% respectively compared to the non-reinforced sample.
Poisoning of soil and groundwater resources is among the current major environmental issues world... more Poisoning of soil and groundwater resources is among the current major environmental issues worldwide. One effective way to stop the spread of pollutants and improve soil’s capacity for adsorption is to use natural and inexpensive adsorbents. In this respect, the soil environment can be improved by the addition of zeolite and rice husk ash (RHA). This study examined the behavior of a sand mixture with 20% kaolinite or 20% bentonite in both uncontaminated and contaminated [with Pb(NO3)2] states. Two classes of clay minerals were considered: kaolinite and bentonite. The impact of the adsorbent on the strength performance of the contaminated soil was examined by removing 10% of the clay particles and replacing them with zeolite or RHA adsorbents. Triaxial dynamic and bender element tests were carried out to explore the dynamic behavior of contaminated soils and the liquefaction resistance of the samples polluted with Pb(NO3)2, respectively. The results show that by reducing the heavy metals concentration Pb(NO3)2, the ultimate strength of sand mix with 20% bentonite increased by 40%–50%. In addition, the ultimate strength increased in polluted and noncontaminated situations by adding zeolite or RHA to the soil. The results of triaxial dynamic tests demonstrated that liquefaction resistance was reduced by increasing the contamination concentrations in both the mixes without and with adsorbent. Furthermore, the initial/maximum shear modulus (G0/Gmax) decreased as the adsorbent content increased in both contaminated and noncontaminated states.
Loess soils have always been among the most problematic soils, according to engineers. Due to the... more Loess soils have always been among the most problematic soils, according to engineers. Due to the sensitivity and vulnerability of this soil type, researchers are constantly looking for different solutions to improve and stabilize this soil using different methods. In the present study, a mixture of lime and rice husk ash (LRHA) was used to modify the loess soil of the Golestan province, Iran. Lime and RHA were mixed in a ratio of 2:4 and with different contents of 2.5, 5, 7.5, 10 and 12.5% of the dry weight of the soil. To study the effect of curing on the strength properties, the samples were cured and tested for 7, 18 and 28 days. Atterberg limits, modified Proctor, unconfined compressive strength (UCS) and scanning electron microscope tests (SEM) were performed. It was found that increasing LRHA content increased the value of UCS at different curing times, such that UCS increased about five times by the addition of 5% LRHA to the loess at the end of 28 days. As the curing time i...
Abstract Electro-osmosis is a phenomenon describing the motion of liquid adjacent to a charged su... more Abstract Electro-osmosis is a phenomenon describing the motion of liquid adjacent to a charged surface under the influence of an electric field. Electro-osmosis is considered as an efficient soft soil improvement technique. In this study, series of laboratory tests were performed utilizing graphite and stainless steel electrodes under three levels of voltage gradients for 28 days using the soil from north of Iran to investigate the effect of various parameters on electro-osmotic and geotechnical properties. Moreover, the microstructure and chemical analyses of the soil before and after treatment gave an in-depth perspective to underlying mechanism of this process. Water drainage which has the most important effect on consolidation of soils, terminated after a few days. The termination time for stainless steel is smaller than graphite and the whole drained water volume is larger in case of stainless steel compared to graphite. The strength around the anode is larger than that of the cathode zone and the stainless steel electrode induced larger strength than the graphite electrode. The SEM images exhibited the agglomeration of the soil after electro-osmosis treatment, and some precipitation was also identified, which was attributed to iron based compounds. Chemical analysis illustrated that the concentration of calcium ions decreased around the anode and increased near the cathode while Fe and Al amount did not change significantly, implying the ion exchange and ion migration due to the electro-osmosis process. Additionally, the stainless steel electrode introduced iron and chrome ions to the soil, which affected structure and chemical distribution of the ions.
The performance of a combined Anchored Earth and Geotextile system of earth reinforcement as prop... more The performance of a combined Anchored Earth and Geotextile system of earth reinforcement as proposed recently (Singh & Finlay, 1986) was studied, and is reported in this paper. Semi-Z shaped mild steel model anchors alternating with a synthetic geotextile in depth were used in a test box and loaded. The end results of the tests presented in the paper demonstrate that the combined system is characterized by a fairly high rigidity and high holding capacity. For the covering abstract of the conference see IRRD 836241. (Author/TRRL)
Uncertainties and inherent variability of soil strength parameters, scatter in the data or system... more Uncertainties and inherent variability of soil strength parameters, scatter in the data or systematic testing and
modeling discrepancies are commonly found in geotechnical problems. The same is true for soil nailed walls as an example
of geotechnical problems, which is similar to rock bolt method being used for reinforcing rock mass. Because of these
issues, engineers cannot evaluate and identify the rate of available risk by deterministic methods such as limit equilibrium
method. In probabilistic methods, most of the existing uncertainties in analysis processes can be considered. This research
studies uncertainty in soil nail walls based on a case study and rock slope excavation using Monte Carlo simulation. The
results were then compared with those of the deterministic method.
Loose sandy soils can be strengthened by reinforcing. Micro-reinforced earth has ductility, enhan... more Loose sandy soils can be strengthened by reinforcing. Micro-reinforced earth has ductility, enhanced elastic stress limit, suitable for analysis by linear methods of analysis, can be idealized to be homogeneous and is ideal for use in earthquake engineering. Free & forced vibration tests were carried out on large 1.5 m x 0.75 m x 0.9 m high reinforced embankments on shake table excited by D.C, motor-oscillator drive. Plane strain conditions were created in lab. From tests, strain dependent shear modulus were obtained. Response computed fron dynamic 2D FEM analysis of test embankments by idealising them with 1-layer and 2-layer system agrees well with response based on test data. This suppots idealisation of microreinforcd earth to be homogeneous.
Journal of Structural Engineering and Geo-Techniques, 2015
In this paper a laboratory study has been carried out on the effect of changing the type of soil ... more In this paper a laboratory study has been carried out on the effect of changing the type of soil filling cylindrical reinforcing elements from SM to GM on behavior of sandy soil. In this study the primary tests for evaluation of the impact of reinforced sand and gravel columns with diameters of 5 cm and heights of 15 cm subjected to vertical stresses of 50, 100, and 150 KPa were carried out in a large-scale direct shear apparatus (300×300×150 mm). Results showed that the shear stress and settlement of the reinforced sample with geogrid and a gravel column increases by 45.4% and decreases by 23.9% respectively compared to the non-reinforced sample.
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modeling discrepancies are commonly found in geotechnical problems. The same is true for soil nailed walls as an example
of geotechnical problems, which is similar to rock bolt method being used for reinforcing rock mass. Because of these
issues, engineers cannot evaluate and identify the rate of available risk by deterministic methods such as limit equilibrium
method. In probabilistic methods, most of the existing uncertainties in analysis processes can be considered. This research
studies uncertainty in soil nail walls based on a case study and rock slope excavation using Monte Carlo simulation. The
results were then compared with those of the deterministic method.
modeling discrepancies are commonly found in geotechnical problems. The same is true for soil nailed walls as an example
of geotechnical problems, which is similar to rock bolt method being used for reinforcing rock mass. Because of these
issues, engineers cannot evaluate and identify the rate of available risk by deterministic methods such as limit equilibrium
method. In probabilistic methods, most of the existing uncertainties in analysis processes can be considered. This research
studies uncertainty in soil nail walls based on a case study and rock slope excavation using Monte Carlo simulation. The
results were then compared with those of the deterministic method.