Lime is widely used to modify clayey soils to enhance their physical and chemical properties,and lime-treated soil has become a key material in transportation infrastructure.Chemical reactions were identified through ...Lime is widely used to modify clayey soils to enhance their physical and chemical properties,and lime-treated soil has become a key material in transportation infrastructure.Chemical reactions were identified through laboratory tests from field samples collected from the subgrade after 30 years of operation to understand its long-term performance evolution.Exchangeable calcium,carbonated calcium,and total calcium were quantified using ethylenediaminetetraacetic acid(EDTA)titration,gasometric analysis,and the strong acid extraction method,respectively.These measurements enabled the evaluation of calcium transformation during the pozzolanic reaction,providing a quantitative characterization of pozzolanic progression in the lime-treated clay matrix.Evolutions in pH,electrical conductivity,and salinity were also tracked.Mechanical performance was assessed through maximal shear modulus(Gmax)and unconfined compressive strength(UCS)tests.Then,the microstructure and mineral composition were analyzed via scanning electron microscopy(SEM)and X-ray diffraction(XRD).Furthermore,with an extended curing period,the pH,electrical conductivity,salinity,and exchangeable calcium content were found to decrease gradually.In contrast,the carbonation-related calcium content increased,and the clay mineral structures were significantly altered.The significant increase in Gmax and UCS is attributed to the formation of calcium-aluminate-silicate-hydrate(C-(A)-S-H)for pozzolanic and carbonation reactions where the clay mineral is involved.SEM reveals the curled edges of clay minerals and the formation of a 3D network.Additionally,XRD patterns further confirm the presence of increasing amounts of amorphous phases within the 2θrange of 15°–32°,indicating the progression of the pozzolanic reaction.展开更多
To better understand the dynamic properties of expansive clay treated with lime, a series of laboratory tests were conducted using a dynamic triaxial test system. The influential factors, including moisture content, c...To better understand the dynamic properties of expansive clay treated with lime, a series of laboratory tests were conducted using a dynamic triaxial test system. The influential factors, including moisture content, confining pressure, vibration frequency, consolidation ratio, and cycle number on the dynamic characteristics were discussed. Experimental results indicate that specimens at low moisture contents tend to damage along the 30~ shear plane and they present brittle failure, while saturated specimens show swelling phenomenon and plastic failure. A redtiction in cohesion has been observed for unsaturated samples at large number of cycles, while it is opposite for the internal friction angle. For the saturated specimens, both the cohesion and internal friction angle decrease with increasing number of cycles.展开更多
Lime-treatment of clayey soil significantly increases its shear and tensile strengths.Consequently,the tensile strength of lime-treated soils deserves careful investigation because it may provide an appreciable benefi...Lime-treatment of clayey soil significantly increases its shear and tensile strengths.Consequently,the tensile strength of lime-treated soils deserves careful investigation because it may provide an appreciable benefit for the stability of earth structures.This study investigates the tensile and shear strengths of an untreated and lime-treated(3%of lime)plastic clay at different curing times(7 d,56 d and 300 d),through triaxial tension and compression tests.Triaxial tension tests are performed using“diabolo-shaped”soil samples with reduced central section,such that the central part of the specimen can be under axial tension while both end-sections remain in axial compression.Consolidated undrained(CU)conditions with measurement of pore water pressure allow analyzing the failure conditions through effective stress and total stress approaches.The results of triaxial tension tests reveal that the failure occurs under tensile mode at low confining pressure while extensional shear failure mode is observed under higher confining pressure.Consequently,a classical Mohr-Coulomb shear failure criterion must be combined with a cut-off tensile strength criterion that is not affected by the confining pressure.When comparing shear failure under compression and tension,a slight anisotropy is observed.展开更多
In the present study,unconfined compressive strength(qu)values of two lime-treated soils(soil 1 and 2)with curing times of 28 d,90 d and 360 d were optimized.The influence of void/lime ratio was represented by the por...In the present study,unconfined compressive strength(qu)values of two lime-treated soils(soil 1 and 2)with curing times of 28 d,90 d and 360 d were optimized.The influence of void/lime ratio was represented by the porosity/volumetric lime content ratio(η/Liv)as the main parameter.η/Liv represents the volume of void influenced by compaction effort and lime volume.The evolution of qu was analyzed for each soil using the coefficient of determination as the optimization parameter.Aiming at providing adjustments to the mechanical resistance values,the η/Liv parameter was modified to η/LivC using the adjustment exponent C(to make qu-η/Liv variation rates compatible).The results show that with the decrease of η/LivC.qu increases potentially and the optimized values of C were 0.14-0.18.The mechanical resistance data show similar trends between qu and η/LivC for the studied silty soil-ground lime mixtures,which were cured at ambient temperature(23±2)℃ with different curing times of 28-360 d.Finally,optimized equations were presented using the normalized strengths and the proposed optimization model,which show 6% error and 95% acceptability on average.展开更多
基金supported by the National Natural Science Foundation of China(Grant No.42302311)the ARC Discovery Project Program(Grant Nos.DP210100437 and DP230100126).
文摘Lime is widely used to modify clayey soils to enhance their physical and chemical properties,and lime-treated soil has become a key material in transportation infrastructure.Chemical reactions were identified through laboratory tests from field samples collected from the subgrade after 30 years of operation to understand its long-term performance evolution.Exchangeable calcium,carbonated calcium,and total calcium were quantified using ethylenediaminetetraacetic acid(EDTA)titration,gasometric analysis,and the strong acid extraction method,respectively.These measurements enabled the evaluation of calcium transformation during the pozzolanic reaction,providing a quantitative characterization of pozzolanic progression in the lime-treated clay matrix.Evolutions in pH,electrical conductivity,and salinity were also tracked.Mechanical performance was assessed through maximal shear modulus(Gmax)and unconfined compressive strength(UCS)tests.Then,the microstructure and mineral composition were analyzed via scanning electron microscopy(SEM)and X-ray diffraction(XRD).Furthermore,with an extended curing period,the pH,electrical conductivity,salinity,and exchangeable calcium content were found to decrease gradually.In contrast,the carbonation-related calcium content increased,and the clay mineral structures were significantly altered.The significant increase in Gmax and UCS is attributed to the formation of calcium-aluminate-silicate-hydrate(C-(A)-S-H)for pozzolanic and carbonation reactions where the clay mineral is involved.SEM reveals the curled edges of clay minerals and the formation of a 3D network.Additionally,XRD patterns further confirm the presence of increasing amounts of amorphous phases within the 2θrange of 15°–32°,indicating the progression of the pozzolanic reaction.
基金Supported by the National Natural Science Foundation of China(40772185)the Knowledge Innovation Program of Chinese Academy of Sciences(kzcx2-yw-150)
文摘To better understand the dynamic properties of expansive clay treated with lime, a series of laboratory tests were conducted using a dynamic triaxial test system. The influential factors, including moisture content, confining pressure, vibration frequency, consolidation ratio, and cycle number on the dynamic characteristics were discussed. Experimental results indicate that specimens at low moisture contents tend to damage along the 30~ shear plane and they present brittle failure, while saturated specimens show swelling phenomenon and plastic failure. A redtiction in cohesion has been observed for unsaturated samples at large number of cycles, while it is opposite for the internal friction angle. For the saturated specimens, both the cohesion and internal friction angle decrease with increasing number of cycles.
文摘Lime-treatment of clayey soil significantly increases its shear and tensile strengths.Consequently,the tensile strength of lime-treated soils deserves careful investigation because it may provide an appreciable benefit for the stability of earth structures.This study investigates the tensile and shear strengths of an untreated and lime-treated(3%of lime)plastic clay at different curing times(7 d,56 d and 300 d),through triaxial tension and compression tests.Triaxial tension tests are performed using“diabolo-shaped”soil samples with reduced central section,such that the central part of the specimen can be under axial tension while both end-sections remain in axial compression.Consolidated undrained(CU)conditions with measurement of pore water pressure allow analyzing the failure conditions through effective stress and total stress approaches.The results of triaxial tension tests reveal that the failure occurs under tensile mode at low confining pressure while extensional shear failure mode is observed under higher confining pressure.Consequently,a classical Mohr-Coulomb shear failure criterion must be combined with a cut-off tensile strength criterion that is not affected by the confining pressure.When comparing shear failure under compression and tension,a slight anisotropy is observed.
基金the Federal University of Technology-Parana, to the CAPES, CNPqFundacao Araucaria do Parana in Brazil for financial support
文摘In the present study,unconfined compressive strength(qu)values of two lime-treated soils(soil 1 and 2)with curing times of 28 d,90 d and 360 d were optimized.The influence of void/lime ratio was represented by the porosity/volumetric lime content ratio(η/Liv)as the main parameter.η/Liv represents the volume of void influenced by compaction effort and lime volume.The evolution of qu was analyzed for each soil using the coefficient of determination as the optimization parameter.Aiming at providing adjustments to the mechanical resistance values,the η/Liv parameter was modified to η/LivC using the adjustment exponent C(to make qu-η/Liv variation rates compatible).The results show that with the decrease of η/LivC.qu increases potentially and the optimized values of C were 0.14-0.18.The mechanical resistance data show similar trends between qu and η/LivC for the studied silty soil-ground lime mixtures,which were cured at ambient temperature(23±2)℃ with different curing times of 28-360 d.Finally,optimized equations were presented using the normalized strengths and the proposed optimization model,which show 6% error and 95% acceptability on average.
