The composite pile consisting of core-pile and surrounding cement-enhanced soil is a promising pile foundation in recent years.However,how and to what extent the cement-enhanced soil influences the ultimate lateral re...The composite pile consisting of core-pile and surrounding cement-enhanced soil is a promising pile foundation in recent years.However,how and to what extent the cement-enhanced soil influences the ultimate lateral resistance has not been fully investigated.In this paper,the ultimate lateral resistance of the composite pile was studied by finite element limit analysis(FELA)and theoretical upper-bound analysis.The results of FELA and theoretical analysis revealed three failure modes of laterally loaded composite piles.The effects of the enhanced soil thickness,strength,and pile-enhanced soil interface characteristics on the ultimate lateral resistance were studied.The results show that increasing the enhanced soil thickness leads to a significant improvement on ultimate lateral resistance factor(N P),and there is a critical thickness beyond which the thickness no longer affects the N P.Increasing the enhanced soil strength induced 6.2%-232.6%increase of N P.However,no noticeable impact was detected when the enhanced soil strength was eight times higher than that of the natural soil.The maximum increment of N P is only 30.5%caused by the increase of interface adhesion factor(a).An empirical model was developed to calculate the N P of the composite pile,and the results show excellent agreement with the analytical results.展开更多
The California bearing ratio (CBR) test is the most widely spread method of determining the bearing strength of the pavement material and is fundamental to pavement design practice in most countries. This test is expe...The California bearing ratio (CBR) test is the most widely spread method of determining the bearing strength of the pavement material and is fundamental to pavement design practice in most countries. This test is expensive, laborious and time consuming, and to overcome this, Quasi static cone penetrometer machine was fabricated and used to measure the consistency limits (liquid limit-LL, Plastic limit-PL and Plasticity index-PI), which were used to develop an empirical equation to determine CBR. Soil samples were collected and unsoaked CBR, PL, LL and PI were determined according to BS 1377 part 9 and BS 1377-2;1990. Quasi static penetration forces at 20 mm depth of penetration were also determined at consistency limits. It was found that the force of 1020 gf and 60 gf was achieved at a depth of 20 mm at PI and LL respectively. The correlation and regression analysis between consistency limits, and the experimental CBR obtained showed coefficient of determination, R<sup>2</sup> = 0.907 between CBR and all the parameters using multiple linear regression analysis (MLRA). The regression equation developed was used together with the relationship developed between the Quasi static Penetration force at consistency limits and the tested consistency limits to come up with the General Empirical Equation. Verification of the formula showed that the correlation can be used accurately to determine the un soaked CBR.展开更多
The investigation of the long-term performance of solidified/stabilized （S/S） contaminated soils was carried out in a trial site in southeast UK. The soils were exposed to the maximum natural weathering for four yea...The investigation of the long-term performance of solidified/stabilized （S/S） contaminated soils was carried out in a trial site in southeast UK. The soils were exposed to the maximum natural weathering for four years and sampled at various depths in a controlled manner. The chemical properties （e.g., degree of carbonation （DOC）, pH, electrical conductivity （EC）） and physical properties （e.g., moisture content （MC）, liquid limit CLL）, plastic limit （PL）, plasticity index （PI）） of the samples untreated and treated with the traditional and accelerated carbonated S/S processes were analyzed. Their variations on the depths of the soils were also studied. The result showed that the broad geotechnical properties of the soils, manifested in their PIs, were related to the concentration of the water soluble ions and in particular the free calcium ions. The samples treated with the accelerated carbonation technology （ACT）, and the untreated samples contained limited number of free calcium ions in solutions and consequently interacted with waters in a similar way. Compared with the traditional cement-based S/S technology, e.g., treatment with ordinary portland cement （OPC） or EnvirOceM, ACT caused the increase of the PI of the treated soil and made it more stable during long-term weathering. The PI values for the four soils ascended according to the order： the EnvirOceM soil, the OPC soil, the ACT soil, and the untreated soil while their pH and EC values descended according to the same order.展开更多
Determination of physical property of the soil helps in identification and classification of soil which includes analysis of particle size distribution, Atterberg limits, water content, specific gravity, phase determi...Determination of physical property of the soil helps in identification and classification of soil which includes analysis of particle size distribution, Atterberg limits, water content, specific gravity, phase determination and direct shear test. Water plays an important role in triggering landslides and slope failures. Increase of water content reduces the stability of slope. When the moisture content exceeds plastic limits, the slope begins to deform. Three soil samples are collected from the study area and the average bulk density, moisture content and specific gravity are 1.577, 37.032 and 2.434 respectively. Atterberg limit is the most distinctive properties of fine grained sediments and may be used to distinguish silts from clays. Plastic limits (WP), liquid limit (WL), shrinkage limit (WS) values of Nungbi Khunou are 26.236%, 48% and 9.4% respectively. Plasticity index (IP), consistency index (IC) and liquidity index (IL) value is 21.764%, 0.379%, and 60.623% respectively. From index properties value, the soil is highly plastic, stiff and semi-solid in nature. The soil sample falls under CI group in plasticity chart which indicates organic silt and clay soil with medium compressibility and plasticity. Phase determination and particle size distribution result in very high porosity and highly saturated soils which are well graded in nature. Slope and aspect map are prepared from DEM using ArcGIS. Slope is an important contributory factor to landslide, and slope reported from the sampling area indicates gentle slope. Aspect refers to the direction of the terrain faces which is influenced by component like vegetation, settlement, agriculture, precipitation, wind etc. Factor of safety (Fs) calculated from shear stress data is less than 1 indicating unstable slope. From the above finding, the study area may result in sudden and unpredictable failure due to volumetric changes in soil.展开更多
基金The work was supported by the National Natural Science Foundation of China(Grant No.51978540).
文摘The composite pile consisting of core-pile and surrounding cement-enhanced soil is a promising pile foundation in recent years.However,how and to what extent the cement-enhanced soil influences the ultimate lateral resistance has not been fully investigated.In this paper,the ultimate lateral resistance of the composite pile was studied by finite element limit analysis(FELA)and theoretical upper-bound analysis.The results of FELA and theoretical analysis revealed three failure modes of laterally loaded composite piles.The effects of the enhanced soil thickness,strength,and pile-enhanced soil interface characteristics on the ultimate lateral resistance were studied.The results show that increasing the enhanced soil thickness leads to a significant improvement on ultimate lateral resistance factor(N P),and there is a critical thickness beyond which the thickness no longer affects the N P.Increasing the enhanced soil strength induced 6.2%-232.6%increase of N P.However,no noticeable impact was detected when the enhanced soil strength was eight times higher than that of the natural soil.The maximum increment of N P is only 30.5%caused by the increase of interface adhesion factor(a).An empirical model was developed to calculate the N P of the composite pile,and the results show excellent agreement with the analytical results.
文摘The California bearing ratio (CBR) test is the most widely spread method of determining the bearing strength of the pavement material and is fundamental to pavement design practice in most countries. This test is expensive, laborious and time consuming, and to overcome this, Quasi static cone penetrometer machine was fabricated and used to measure the consistency limits (liquid limit-LL, Plastic limit-PL and Plasticity index-PI), which were used to develop an empirical equation to determine CBR. Soil samples were collected and unsoaked CBR, PL, LL and PI were determined according to BS 1377 part 9 and BS 1377-2;1990. Quasi static penetration forces at 20 mm depth of penetration were also determined at consistency limits. It was found that the force of 1020 gf and 60 gf was achieved at a depth of 20 mm at PI and LL respectively. The correlation and regression analysis between consistency limits, and the experimental CBR obtained showed coefficient of determination, R<sup>2</sup> = 0.907 between CBR and all the parameters using multiple linear regression analysis (MLRA). The regression equation developed was used together with the relationship developed between the Quasi static Penetration force at consistency limits and the tested consistency limits to come up with the General Empirical Equation. Verification of the formula showed that the correlation can be used accurately to determine the un soaked CBR.
文摘The investigation of the long-term performance of solidified/stabilized （S/S） contaminated soils was carried out in a trial site in southeast UK. The soils were exposed to the maximum natural weathering for four years and sampled at various depths in a controlled manner. The chemical properties （e.g., degree of carbonation （DOC）, pH, electrical conductivity （EC）） and physical properties （e.g., moisture content （MC）, liquid limit CLL）, plastic limit （PL）, plasticity index （PI）） of the samples untreated and treated with the traditional and accelerated carbonated S/S processes were analyzed. Their variations on the depths of the soils were also studied. The result showed that the broad geotechnical properties of the soils, manifested in their PIs, were related to the concentration of the water soluble ions and in particular the free calcium ions. The samples treated with the accelerated carbonation technology （ACT）, and the untreated samples contained limited number of free calcium ions in solutions and consequently interacted with waters in a similar way. Compared with the traditional cement-based S/S technology, e.g., treatment with ordinary portland cement （OPC） or EnvirOceM, ACT caused the increase of the PI of the treated soil and made it more stable during long-term weathering. The PI values for the four soils ascended according to the order： the EnvirOceM soil, the OPC soil, the ACT soil, and the untreated soil while their pH and EC values descended according to the same order.
文摘Determination of physical property of the soil helps in identification and classification of soil which includes analysis of particle size distribution, Atterberg limits, water content, specific gravity, phase determination and direct shear test. Water plays an important role in triggering landslides and slope failures. Increase of water content reduces the stability of slope. When the moisture content exceeds plastic limits, the slope begins to deform. Three soil samples are collected from the study area and the average bulk density, moisture content and specific gravity are 1.577, 37.032 and 2.434 respectively. Atterberg limit is the most distinctive properties of fine grained sediments and may be used to distinguish silts from clays. Plastic limits (WP), liquid limit (WL), shrinkage limit (WS) values of Nungbi Khunou are 26.236%, 48% and 9.4% respectively. Plasticity index (IP), consistency index (IC) and liquidity index (IL) value is 21.764%, 0.379%, and 60.623% respectively. From index properties value, the soil is highly plastic, stiff and semi-solid in nature. The soil sample falls under CI group in plasticity chart which indicates organic silt and clay soil with medium compressibility and plasticity. Phase determination and particle size distribution result in very high porosity and highly saturated soils which are well graded in nature. Slope and aspect map are prepared from DEM using ArcGIS. Slope is an important contributory factor to landslide, and slope reported from the sampling area indicates gentle slope. Aspect refers to the direction of the terrain faces which is influenced by component like vegetation, settlement, agriculture, precipitation, wind etc. Factor of safety (Fs) calculated from shear stress data is less than 1 indicating unstable slope. From the above finding, the study area may result in sudden and unpredictable failure due to volumetric changes in soil.
