This study explores an alternative to the classical use of direct methods, as water content and dry density measurements, for compaction quality control. For this purpose, the dielectric properties of lateritic materi...This study explores an alternative to the classical use of direct methods, as water content and dry density measurements, for compaction quality control. For this purpose, the dielectric properties of lateritic materials are determined by radar method and are compared with the permittivity determined from the Topp formula and from the CRIM model. This approach allowed to establish a relationship between the geotechnical properties determined during compaction such as dry density, water content or porosity with dielectric permittivity. The obtained results made it possible to determine an optimum dielectric permittivity corresponding to the optimum dry density and the optimum water content that could be used for non-destructive in situ compaction testing. Such an approach should improve the implementation and effectiveness of in situ compaction quality control of geotechnical infrastructures.展开更多
Natural soils of various types have different electrical properties due to the composition,structure,water content,and temperature.In order to investigate the electrical properties of lateritic soil,electrical conduct...Natural soils of various types have different electrical properties due to the composition,structure,water content,and temperature.In order to investigate the electrical properties of lateritic soil,electrical conductivity experiments have been conducted on a self-developed testing device.Test results show that the electrical conductivity of laterite increases with the increase of water content,degree of saturation and dry density.When the water content is below the optimum water content,the electrical conductivity of soils increases nonlinearly and the variation rate increases dramatically.However,when the water content,degree of saturation,or dry density increases to a certain value,the electrical conductivity tends to be a constant.In addition,soil electrical conductivity increases with the increase of temperature,and it is observed that the electrical conductivity decreases with the increase of the number of wetting–drying cycles.展开更多
Based on analytical methods of strength studies for deep soils, direct shear tests were carried out to investigate the shear strength of deep reconstituted soils at different initial dry densities and amounts of water...Based on analytical methods of strength studies for deep soils, direct shear tests were carried out to investigate the shear strength of deep reconstituted soils at different initial dry densities and amounts of water.The results indicate that the shear strength of deep reconstituted soils for identical amounts of water below the plastic limit is enhanced with increasing dry density and but reduced sharply at the critical density, the point at which coarse particles break down.Moreover, the shear strength for identical dry density decreases with additional amounts of water and the rate of degradation is the greatest at the critical density.This is because the friction resistance between coarse particles reduces with increasing amounts of water higher than the plastic limit.In order to obtain reliable strength of deep reconstituted soils, suitable dry densities and amounts of water are necessary.展开更多
This paper reports the results of an investigation carried out on clay soil stabilized with pond ash(PA),rice husk ash(RHA) and cement. Modified Proctor compaction tests were performed in order to investigate the comp...This paper reports the results of an investigation carried out on clay soil stabilized with pond ash(PA),rice husk ash(RHA) and cement. Modified Proctor compaction tests were performed in order to investigate the compaction behavior of clay, and California bearing ratio(CBR) tests were performed to determine the strength characteristics of clay. For evaluation purpose, the specimens containing different amounts of admixtures were prepared. Clay was replaced with PA and RHA at a dosage of 30%e45% and5%e20%, respectively. The influence of stabilizer types and dosages on mechanical properties of clay was evaluated. In order to study the surface morphology and crystallization characteristics of the soil samples, scanning electron microscopy(SEM) and X-ray diffraction(XRD) analyses were carried out,respectively. The results obtained indicated a decrease in the maximum dry density(MDD) and a simultaneous increase in the optimum moisture content(OMC) with the addition of PA and RHA.Multiple linear regression analysis(MLRA) showed that the predicted values of CBR tests are in good agreement with the experimental values. Developed stabilized soil mixtures showed satisfactory strength and can be used for construction of embankments and stabilization of sub-grade soil. The use of locally available soils, PA, RHA, and cement in the production of stabilized soils for such applications can provide sustainability for the local construction industry.展开更多
Callovo-Oxfordian （COx） argillite obtained from the excavation of high-level radioactive waste geological disposal has been evaluated as an alternative sealing/backfill material in France. This paper presents an exp...Callovo-Oxfordian （COx） argillite obtained from the excavation of high-level radioactive waste geological disposal has been evaluated as an alternative sealing/backfill material in France. This paper presents an experimental investigation into the hydro-mechanical behaviour of compacted crushed COx argillite. A series of oedorneter compressive tests including various loading-unloading cycles were conducted on COx argillite powders at different initial water contents. After reaching the desired dry density （2.0 Mg/m^3）, the vertical stress was reduced to different levels （7.0 and 0.5 MPa） and the compacted sample was then flooded under constant volume conditions while measuring the changes in the vertical stress. It was found that the initial water content significantly affects the compressive behaviour. The measured saturated hydraulic conductivity is less than 1×10^-10m/s.展开更多
It is too difficult for a compacted specimen of unsaturated clay prepared and used in a laboratory test to have homogeneous water content and porosity. Although there have been many hydraulic and mechanical studies, t...It is too difficult for a compacted specimen of unsaturated clay prepared and used in a laboratory test to have homogeneous water content and porosity. Although there have been many hydraulic and mechanical studies, there are few papers related to homogeneity of specimen. However, it is clear that homogeneity of specimen influences mechanical properties. In this paper, the use of micro-waves is proposed as method for making homogeneous specimens. The study results indicate that specimens made by micro-waves are more homogeneous than compacted specimens.展开更多
Aphid establishes colony in the selective plant parts like vine, leaf petiole, leaflet, inflorescence, and tender fruit in Dolichos lablab Linn but not the entire plant. In this study, the aphid colony establishment i...Aphid establishes colony in the selective plant parts like vine, leaf petiole, leaflet, inflorescence, and tender fruit in Dolichos lablab Linn but not the entire plant. In this study, the aphid colony establishment in vine is focused to understand the differential resistance response between two varieties. At the early stage of aphid infestation, the aphid colony establishment was significantly different between two genotypes (p value = 0.00) and abbreviated as “resistant” variety that supported lower aphid proliferation (mean value = 48.2 ± 2.2) and “susceptible” variety that supported comparatively higher aphid proliferation (mean value = 215.5 ± 16.9). The total aphid number was significantly different between the two varieties, realized at the early infestation stage when both “antixenosis” and “antibiosis” defense mechanisms were working on. Some plant specific factors like vine diameter, wet/ dry weight ratio of vine, phloem sap pressure, the compactness of the vine, wet/dry weight ratio of leaflet, length of leaf petiole, diameter of leaflet vein were identified as modulating factors. The impact of resistant variety on aphid was also investigated for better understanding of aphid defense mechanism.展开更多
Establishment of effective sawah management system in parts of southeastern Nigeria may involve the manipulation of certain soil physical properties in form of ecological engineering works. This practice may affect th...Establishment of effective sawah management system in parts of southeastern Nigeria may involve the manipulation of certain soil physical properties in form of ecological engineering works. This practice may affect the soil physical properties adversely. The objective of the study were basically to compare the influence of sawah and non sawah water management practices on the soil physical properties following rice cultivation with various inorganic and organic amendments. Parameters determined were soil bulk density, total porosity, moisture contents at field capacity (FC) and wilting point (WP), water-stable aggregates, dispersion ratio (DR), and hydraulic conductivity (Ks). Sawah managed soils reduced significantly the soil bulk density in the first and second year of planting thus increasing the soil total porosity during the same period Moisture content also improved in sawah management while WP increased significantly in the second year of planting. In spite of the destruction of soil structure as a result of cultural practices during rice cultivation the DR is improved on the long run by sawah water management. Moisture contents at FC and WP relates significantly with soil bulk density which also relates negatively with total porosity during the 2 years of cultivation. However, FC and WP may be very good tools in the estimation of bulk density. Again, the amendments were identified as promoting the development of soil aggregates and Ks on a long term.展开更多
文摘This study explores an alternative to the classical use of direct methods, as water content and dry density measurements, for compaction quality control. For this purpose, the dielectric properties of lateritic materials are determined by radar method and are compared with the permittivity determined from the Topp formula and from the CRIM model. This approach allowed to establish a relationship between the geotechnical properties determined during compaction such as dry density, water content or porosity with dielectric permittivity. The obtained results made it possible to determine an optimum dielectric permittivity corresponding to the optimum dry density and the optimum water content that could be used for non-destructive in situ compaction testing. Such an approach should improve the implementation and effectiveness of in situ compaction quality control of geotechnical infrastructures.
基金The fnancial supports from the National Natural Science Foundation of China(Grant No.51209196)the Science and Technology Project of Ministry of Transport of China(Grant No.20113184931700)
文摘Natural soils of various types have different electrical properties due to the composition,structure,water content,and temperature.In order to investigate the electrical properties of lateritic soil,electrical conductivity experiments have been conducted on a self-developed testing device.Test results show that the electrical conductivity of laterite increases with the increase of water content,degree of saturation and dry density.When the water content is below the optimum water content,the electrical conductivity of soils increases nonlinearly and the variation rate increases dramatically.However,when the water content,degree of saturation,or dry density increases to a certain value,the electrical conductivity tends to be a constant.In addition,soil electrical conductivity increases with the increase of temperature,and it is observed that the electrical conductivity decreases with the increase of the number of wetting–drying cycles.
基金Projects 50534040 supported by the National Natural Science Foundation of China2006BAB16B01 by the Ministry of Science and Technology of ChinaCX08B_103Z by the Post Graduate Research Projects of Jiangsu Province
文摘Based on analytical methods of strength studies for deep soils, direct shear tests were carried out to investigate the shear strength of deep reconstituted soils at different initial dry densities and amounts of water.The results indicate that the shear strength of deep reconstituted soils for identical amounts of water below the plastic limit is enhanced with increasing dry density and but reduced sharply at the critical density, the point at which coarse particles break down.Moreover, the shear strength for identical dry density decreases with additional amounts of water and the rate of degradation is the greatest at the critical density.This is because the friction resistance between coarse particles reduces with increasing amounts of water higher than the plastic limit.In order to obtain reliable strength of deep reconstituted soils, suitable dry densities and amounts of water are necessary.
文摘This paper reports the results of an investigation carried out on clay soil stabilized with pond ash(PA),rice husk ash(RHA) and cement. Modified Proctor compaction tests were performed in order to investigate the compaction behavior of clay, and California bearing ratio(CBR) tests were performed to determine the strength characteristics of clay. For evaluation purpose, the specimens containing different amounts of admixtures were prepared. Clay was replaced with PA and RHA at a dosage of 30%e45% and5%e20%, respectively. The influence of stabilizer types and dosages on mechanical properties of clay was evaluated. In order to study the surface morphology and crystallization characteristics of the soil samples, scanning electron microscopy(SEM) and X-ray diffraction(XRD) analyses were carried out,respectively. The results obtained indicated a decrease in the maximum dry density(MDD) and a simultaneous increase in the optimum moisture content(OMC) with the addition of PA and RHA.Multiple linear regression analysis(MLRA) showed that the predicted values of CBR tests are in good agreement with the experimental values. Developed stabilized soil mixtures showed satisfactory strength and can be used for construction of embankments and stabilization of sub-grade soil. The use of locally available soils, PA, RHA, and cement in the production of stabilized soils for such applications can provide sustainability for the local construction industry.
基金Supported by the French National Radioactive Waste Management Agency
文摘Callovo-Oxfordian （COx） argillite obtained from the excavation of high-level radioactive waste geological disposal has been evaluated as an alternative sealing/backfill material in France. This paper presents an experimental investigation into the hydro-mechanical behaviour of compacted crushed COx argillite. A series of oedorneter compressive tests including various loading-unloading cycles were conducted on COx argillite powders at different initial water contents. After reaching the desired dry density （2.0 Mg/m^3）, the vertical stress was reduced to different levels （7.0 and 0.5 MPa） and the compacted sample was then flooded under constant volume conditions while measuring the changes in the vertical stress. It was found that the initial water content significantly affects the compressive behaviour. The measured saturated hydraulic conductivity is less than 1×10^-10m/s.
文摘It is too difficult for a compacted specimen of unsaturated clay prepared and used in a laboratory test to have homogeneous water content and porosity. Although there have been many hydraulic and mechanical studies, there are few papers related to homogeneity of specimen. However, it is clear that homogeneity of specimen influences mechanical properties. In this paper, the use of micro-waves is proposed as method for making homogeneous specimens. The study results indicate that specimens made by micro-waves are more homogeneous than compacted specimens.
文摘Aphid establishes colony in the selective plant parts like vine, leaf petiole, leaflet, inflorescence, and tender fruit in Dolichos lablab Linn but not the entire plant. In this study, the aphid colony establishment in vine is focused to understand the differential resistance response between two varieties. At the early stage of aphid infestation, the aphid colony establishment was significantly different between two genotypes (p value = 0.00) and abbreviated as “resistant” variety that supported lower aphid proliferation (mean value = 48.2 ± 2.2) and “susceptible” variety that supported comparatively higher aphid proliferation (mean value = 215.5 ± 16.9). The total aphid number was significantly different between the two varieties, realized at the early infestation stage when both “antixenosis” and “antibiosis” defense mechanisms were working on. Some plant specific factors like vine diameter, wet/ dry weight ratio of vine, phloem sap pressure, the compactness of the vine, wet/dry weight ratio of leaflet, length of leaf petiole, diameter of leaflet vein were identified as modulating factors. The impact of resistant variety on aphid was also investigated for better understanding of aphid defense mechanism.
文摘Establishment of effective sawah management system in parts of southeastern Nigeria may involve the manipulation of certain soil physical properties in form of ecological engineering works. This practice may affect the soil physical properties adversely. The objective of the study were basically to compare the influence of sawah and non sawah water management practices on the soil physical properties following rice cultivation with various inorganic and organic amendments. Parameters determined were soil bulk density, total porosity, moisture contents at field capacity (FC) and wilting point (WP), water-stable aggregates, dispersion ratio (DR), and hydraulic conductivity (Ks). Sawah managed soils reduced significantly the soil bulk density in the first and second year of planting thus increasing the soil total porosity during the same period Moisture content also improved in sawah management while WP increased significantly in the second year of planting. In spite of the destruction of soil structure as a result of cultural practices during rice cultivation the DR is improved on the long run by sawah water management. Moisture contents at FC and WP relates significantly with soil bulk density which also relates negatively with total porosity during the 2 years of cultivation. However, FC and WP may be very good tools in the estimation of bulk density. Again, the amendments were identified as promoting the development of soil aggregates and Ks on a long term.
