In this paper, a comparison of influences of freeze-thaw action on lime stabilized basalt and polypropylene fiber reinforced clay was investigated. Specimens including 12 mm basalt and polypropylene ...fiber at 0, 0.5 and 1% contents by weight were compacted under standard Proctor effort at their optimum moisture contents. Some of the fiber-clay mixtures were stabilized with 3% of lime, the rest of specimens were free of lime, for comparison. All specimens were cured for 28 days in a moist room (relative humidity is 95 ± 2%) at an average temperature of 20 °C. After curing, specimens were subjected to 0, 1, 3, 7 and 10 cycles of freeze-thaw tests following ASTM procedure. A series of unconfined compression and ultrasonic pulse velocity tests were performed. Test results showed that increased application of freeze-thaw cycles caused a decrease in unconfined compressive strength and ultrasonic pulse velocity of all specimens. A linear correlation was observed between unconfined compressive strength and ultrasonic pulse velocity values. Besides, loss of mass in specimens after being exposed to freeze-thaw action was evident. Considering freeze-thaw resistance, it was understood that polypropylene fiber is more effective in comparison with basalt fiber against freeze-thaw action.
•Freeze-thaw performance of basalt and polypropylene fiber reinforced lime stabilized clay were compared.•It is recommended to use polypropylene fiber instead of basalt fiber in cold regions to improve the engineering properties of soil.•Variations in UPV, UCS and ML of specimens were evaluated.
In soil stabilisation, the use of alternative products to lime or cement has been proposed. However, the effects of these additives, of various origins, on soil behaviour and stabilizing mechanisms ...are not well understood. Thus, the aim of this paper is to characterize the modification of the mechanical behaviour and microstructure of two soils after treatment with one of those product, a vinyl based copolymer. After treatment, both materials were compacted up to their maximum dry density. The mechanical behaviour of the materials as a function of the curing conditions, suction and water content was first determined. In a second step, the alteration of the microstructure by the treatment product was assessed. The results showed that the treatment permitted to significantly improve the strength of the tested soils. Moreover, the efficiency of the product increases when the soil is dried. However, the Young modulus is not significantly modified by the treatment. Microstructural reorganization after co-polymer addition has been detected by SEM technique for kaolin samples, whereas no modification have been observed for silt samples.
Site response analyses and solution of dynamic soil-structure interaction problems need determination of variation of shear modulus and damping ratio with shear strain. Since many studies in ...literature concern evaluation of behavior of sands and silty sands, a series of cyclic triaxial tests were performed to determine the variation of shear modulus and damping ratio of a nonplastic silt with shear strain. Stress controlled cyclic triaxial tests on silt specimens of initial relative densities ranging among 30%, 50% and 70% were performed. Tests were carried out on identical samples under different CSR levels, and the confining pressure was selected as 100 kPa. Variation of shear modulus and damping ratio of silts with cyclic stress ratio amplitude, relative density and number of cycles were investigated. It was understood that soil relative density and cyclic stress ratio amplitude has a significant influence on shear modulus and damping ratio of silts. It was also observed that, as the cyclic stress ratio amplitude is increased, greater shear modulus and lower damping ratio values were obtained.
Geopolymers are obtained by use of alteration of chemical composition and crystal structures of different minerals. Use of geopolymer is an effective and environmental friendly solution in ...stabilization of clayey soil. The vinyl based copolymer is used as an agent as dust controller, highway soil stabilizer, asphalt admixture, concrete production, etc. In this study, strength of a clay is improved by use of a commercial geopolymer. In this regard, soil was amended with polymer ranging among 0 % to 4 %, by volume of dry soil. Unconfined compression and oedometer tests were carried out to evaluate the effects of temperature, initial water content, compaction energy on strength and compression properties of a clay soil - within an experimental framework. The results revealed that, temperature has a considerable effect on geopolymerization. Besides, under constant moisture content during curing, increasing geopolymer content and curing period causes a slight increase in strength of specimens.
In this study, the relationships among plasticity ratio, clay fraction and liquidity index of clay-sand mixtures were investigated. Two types of clays, namely, kaolin (K) and calcium-montmorillonite ...(CM) were used to prepare clay-sand mixtures of different grain size distributions. Clays were mixed with clean sands of two different grain size distributions (well graded sand-SW and poorly graded sand-SP) at clay contents ranging between 0% to 100% by increments of 10%, in terms of dry weight. Fall cone, Casagrande, plastic limit and laboratory vane shear tests were performed on various clay- sand mixtures with different clay contents. Experimental results revealed that, above 100% water content, undrained shear strength values of CMSW and CMSP mixtures were determined to be around 50 kPa. On the other hand, undrained shear strengths of KSW and KSP mixtures are around 30 kPa, for a water content of 30%. Average undrained shear strengths of CMS and KS mixtures at their plastic limits are obtained as 210.68 kPa and 119.62 kPa, respectively. Average undrained shear strengths of these mixtures at their liquid limits are determined to be 2.40 kPa and 1.88 kPa, respectively. It is concluded that various mechanisms control liquid and plastic limits of clay-sand mixtures which are influenced by gradation of sand, clay content as well as origin of clay. As a result, several relationships among parameters including water content, liquidity index, undrained shear strength, cone penetration depth, fall cone liquid limit and Casagrande liquid limit were presented.
•Results of penetration tests for 44 clay-sand mixtures are presented.•Sand and clay fractions affect on overall behavior.•A clear relationship exists between liquidity index and undrained shear strength.•Atterberg limits are influenced by size distribution of sand and properties of clay.
This study presents an investigation into liquefaction and post-liquefaction behavior of a nonplastic silt under cyclic loading. A systematic approach was adopted for assessment of above-mentioned ...behavior by performing cyclic triaxial tests on saturated specimens in terms of pore water pressure build-up characteristics, effective stress, number of cycles and double amplitude axial strain. The specimens, consolidated under an effective confining pressure of 100 kPa, were prepared at relative densities ranging among 30–80%. The results revealed that the axial strains of specimens of lower relative densities were increased at higher CSR levels. For prediction of pre- and post-liquefaction behavior, a family of curves for establishing relationships among factor of safety to liquefaction, post-liquefaction volumetric strain and relative density were established. These curves, along with the calculation of post-liquefaction volumetric strain, may be useful in estimation of settlements of silt after being subjected to cyclic loading.
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•Variation of cyclic resistance of a nonplastic silt is investigated.•The effects of DR, CSR, γ and εv is investigated.•FoS against liquefaction is correlated with the maximum shear strain.•A relationship between FoS and post liquefaction volumetric strain was derived.•Results of this study may be beneficial in engineering practice.
Angle of shearing resistance is the key for the strength analysis of soils, since this parameter is commonly used for the description of shear strength of a soil. Many factors including soil ...mineralogy, particle shape, grain size distribution, void ratio, organic content, as well as water existence are effective on this parameter. Use of shear box tests for the determination of angle of shearing resistance is prevalent in geotechnical engineering practice, since it is rather successful in identification of shear strength of granular media. However, for cases in which shear box tests exhibit unreliable outcomes, alternative methods for the determination of this parameter could be beneficial. In this investigation, a number of nonlinear multiple regression, adaptive neuro-fuzzy inference systems, and artificial neural network (ANN) models are employed for the estimation of estimating the angle of shearing resistance of uniform sands by means of several grain size distribution, particle shape, and density parameters. Data including results of 132 shear box tests, particle shape identifiers, and grain size distribution parameters on uniform sands are used in the models. In training sessions, results of 104 tests are selected randomly and the results of remaining 28 tests are considered for testing sessions. The results revealed that the performance of a simple ANN architecture is sufficient for pre-evaluation of shearing resistance angle of uniform sands with the help of selected parameters. Since generalization of these models necessitates vast amount of experiments, great care should be dedicated on the assessment of similarity of training as well as testing data.
In the past, several studies were performed for assessment of compaction properties of different types of soils. A comprehensive evaluation of compaction parameters is essential for engineers working ...in practice. The main goals of compaction in landfills including highways and railways can be listed as reducing permeability and developing strength as well as enhancing the stability of soils. Literature includes various correlations proposed for establishing the link between the compaction properties of soils and Atterberg limits. Besides, many researchers performed laboratory studies to obtain correlations among soil index, strength, compression, and compaction characteristics of soils. In this study, in addition to authors’ own data composed of compaction, strength, index, and consistency identifiers of sand-clay mixtures from three different types of sands (S1, S2, Q) and two types of clays (kaolinite and bentonite), a vast amount of data from past studies including tests on different types of soils around the world were also compiled. The global database was evaluated to propose novel correlative relationships among compaction characteristics, grain size distribution properties, and Atterberg limits. Proposed equations and relationships for estimation of compaction characteristics seem to be viable to use in practice.
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