The Tianshui Experimental Site of Soil and Water Conservation was set up in 1942.Then the first construction publicized the thinking of soil and water conservation,and popularized the technologies of soil and water co...The Tianshui Experimental Site of Soil and Water Conservation was set up in 1942.Then the first construction publicized the thinking of soil and water conservation,and popularized the technologies of soil and water conservation and related plants.Their efforts established the foundation of the science of soil and water conservation with the first high-tech and high quality R&D team,and pushed the research of soil and water conservation building on the stage of systematization.All of this provided rare good scientific data and theoretical support for the soil and water conservation and the development of the regional economy in Northwest China.展开更多
The combined application of mineral fertilizer and biochar significantly improves the passivation of heavy metal-contaminated soil,surpassing the effects of individual application.This study has reinforced the validat...The combined application of mineral fertilizer and biochar significantly improves the passivation of heavy metal-contaminated soil,surpassing the effects of individual application.This study has reinforced the validation of their passivation competence as soil remediation agents by examining the multifaceted role of potassium-silicon-calcium mineral fertilizer combined with rice husk-based biochar generated at different pyrolysis temperatures.The soil leaching column experiment,conducted based on the adsorption experiments,has facilitated our scrutiny of the passivation impacts of cadmium(Cd)and lead(Pb)when introducing different proportions of mineral fertilizers and biochar into the soil.These results indicate that biochar’s adsorption efficiency for Cd and Pb is significantly improved at escalated pyrolytic temperature conditions in a single solution.The biochar generated at 700℃(C700)renders adsorption effectiveness of approximately 84.24%for Cd and 99.74%for Pb.Biochar conspicuously registers superior adsorption efficiency towards Pb relative to Cd.The mineral fertilizer,which achieves an adsorption efficiency of 97.76%for Cd,is identified as the main adsorbent for Cd,although its competence is slightly lower compared to C700 for Pb adsorption.Within a complex solution,biochar and mineral fertilizer show reduced Cd and Pb adsorption levels compared to single solutions.There is a keen competition for adsorption surfaces witnessed between Cd and Pb,with Pb’s distribution coefficient(Kd)notably outpacing that of Cd.The isothermal adsorption analyses depict that the mineral fertilizer follows the Langmuir model for Cd adsorption,while C700 conveys the Freundlich model for Pb adsorption.The soil leaching column experiment’s results signify that the composite passivation agents significantly outperform the individual passivation agents in efficiency.The combined application of biochar and mineral fertilizer minimizes the cumulative leaching of Cd and Pb,with the optimal soil remedy proportion for heavy metal contamination being 7∶3.In practical application,mindful consideration should be accorded to the deployment ratios of different passivation agents.展开更多
To analyze the characteristics of solar seasonal soil thermal storage in a solar-ground coupled heat pump system (SGCHPS) in severe cold area,the software FLUENT was used to establish the three-dimensional unsteady st...To analyze the characteristics of solar seasonal soil thermal storage in a solar-ground coupled heat pump system (SGCHPS) in severe cold area,the software FLUENT was used to establish the three-dimensional unsteady state fluid-solid coupling mathematical model of multi-well ground heat exchanger (MWGHE).The User-Defined Functions (UDF) of solar collector and plate heat exchanger were written and dynamically loaded into the model of MWGHE as the boundary conditions.In this way,the dynamic simulation of solar seasonal soil thermal storage was realized.The comparison of simulative and experimental results showed that the overall variation trend of simulative and experimental values achieves a good agreement with time;the relative errors of simulated parameters are all in the allowable range.Therefore,it can be obtained that the models established can be applied in the investigation of performance of solar seasonal soil thermal storage.At the same time,it provides a theoretical basis for the study of heating in SGCHPS and soil heat balance analysis after long-time thermal storage and extraction.展开更多
土壤是陆地生态系统中最大的有机碳库,在全球碳循环中起重要作用。土壤中铁氧化物通过矿物-有机保护作用调控有机碳的固持与矿化过程,是土壤碳循环的关键机制之一。目前土壤碳-铁耦合的实验研究已逐步拓展。为系统梳理土壤碳-铁耦合实...土壤是陆地生态系统中最大的有机碳库,在全球碳循环中起重要作用。土壤中铁氧化物通过矿物-有机保护作用调控有机碳的固持与矿化过程,是土壤碳循环的关键机制之一。目前土壤碳-铁耦合的实验研究已逐步拓展。为系统梳理土壤碳-铁耦合实验设计的研究进展,本研究通过Web of Science和中国知网CNKI数据库收集相关文献,运用CiteSpace进行文献计量分析。结果显示:土壤碳-铁耦合研究呈现阶段性增长,研究内容围绕氧化铁、碳封存、稳定性等关键词展开;碳-铁耦合早期研究聚焦于土壤碳、铁组成与吸附作用,近年来研究逐渐侧重土壤碳-铁耦合机制及环境响应,显示了土壤碳-铁耦合研究的内核深化与外延拓展;碳-铁耦合实验设计主要从碳与铁组分分析、铁与碳添加响应、环境因子调控、区域地理特征差异4个维度开展。现有研究已揭示碳-铁耦合机制的复杂性,但在微观机制和多因子交互作用等方面仍需加强多区域、多时空尺度的实验验证。展开更多
The infiltration of water contaminants into soil and groundwater systems can greatly affect the quality of groundwater. A laboratory-designed large soil tank with periodic and continuous infiltration models, respectiv...The infiltration of water contaminants into soil and groundwater systems can greatly affect the quality of groundwater. A laboratory-designed large soil tank with periodic and continuous infiltration models, respectively, was used to simulate the migration of the contaminants NH4 and NO3 in a soil and groundwater system, including unsaturated and saturated zones. The unsaturated soil zone had a significant effect on removing NH4 and NO3 infiltrated from the surface water. The patterns of breakthrough curves of NH4 and NO3 in the unsaturated zone were related to the infiltration time. A short infiltration time resulted in a single sharp peak in the breakthrough curve, while a long infiltration time led to a plateau curve. When NH4 and NO3 migrated from the unsaturated zone to the saturated zone, an interracial retardation was formed, resulting in an increased contaminant concentration on the interface. Under the influence of horizontal groundwater movement, the infiltrated contaminants formed a contamination-prone area downstream. As the contaminants migrated downstream, their concentrations were significantly reduced. Under the same infiltration concentration, the concentration of NO3 was greater than that of NH4 at every corresponding cross-section in the soil and groundwater tank, suggesting that the removal efficiency of NH4 was greater than that of NO3 in the soil and groundwater system.展开更多
The relationships between rainfall, runoff and erosion in South China granitic weathering red soil region were studied by using data collected from 7 experimental plots in Wuhua County, Guangdong Province. Results sho...The relationships between rainfall, runoff and erosion in South China granitic weathering red soil region were studied by using data collected from 7 experimental plots in Wuhua County, Guangdong Province. Results showed that when rainfall is less than 50 mm, small volumes of runoff were produced. Rainfall intensity might be the main factor in controlling runoff. When rainfall exceeds 50 mm, because of its large volume and high intensity, runoff and the produced amount of erosion increased with raimfall quickly. Analysis of the relationship bebeen runoff and erosion suggsted that runoff of 30 mm (corresponding to about 50 mm rainfall might be taken as a threshold at which wter on land surface was sufficient to start the larg amount of soil particles. Vegtation cover is very effective in protection soil from being eroded. When vegetation coverag increases from 0 to 80 percent,runoff and soil loss decrease from 179.34mm/a to 126.36mm/a and 6262.15T/a km2 to 368.02 T/a km2, respectively.展开更多
This study addresses firstly the soil fabric variations of loose and dense compacted soil samples during a single wetting/drying cycle at suctions between 0 and 287.9 MPa using mainly the mercury intrusion porosimetry...This study addresses firstly the soil fabric variations of loose and dense compacted soil samples during a single wetting/drying cycle at suctions between 0 and 287.9 MPa using mainly the mercury intrusion porosimetry（MIP） tests.Two suction techniques were employed to apply this wide suction range：the osmotic technique for suctions less than 8.5 MPa,and the vapor equilibrium or salt solution technique for suctions higher than 8.5 MPa.Secondly,the soil water retention curves（SWRCs） were predicted by the MIP test results for both loose and dense soil samples.A reasonable correspondence between MIP results and SWRCs was found on the wetting path at lower suctions close to saturation and on drying path at higher suctions.展开更多
The eastern foothills of the Helan Mountains in China are a typical mountainous region of soil and gravel,where gravel could affect the water movement process in the soil.This study focused on the effects of different...The eastern foothills of the Helan Mountains in China are a typical mountainous region of soil and gravel,where gravel could affect the water movement process in the soil.This study focused on the effects of different gravel contents on the water absorption characteristics and hydraulic parameters of stony soil.The stony soil samples were collected from the eastern foothills of the Helan Mountains in April 2023 and used as the experimental materials to conduct a one-dimensional horizontal soil column absorption experiment.Six experimental groups with gravel contents of 0%,10%,20%,30%,40%,and 50%were established to determine the saturated hydraulic conductivity(K_(s)),saturated water content(θ_(s)),initial water content(θ_(i)),and retention water content(θ_(r)),and explore the changes in the wetting front depth and cumulative absorption volume during the absorption experiment.The Philip model was used to fit the soil absorption process and determine the soil water absorption rate.Then the length of the characteristic wetting front depth,shape coefficient,empirical parameter,inverse intake suction and soil water suction were derived from the van Genuchten model.Finally,the hydraulic parameters mentioned above were used to fit the soil water characteristic curves,unsaturated hydraulic conductivity(K_(θ))and specific water capacity(C(h)).The results showed that the wetting front depth and cumulative absorption volume of each treatment gradually decreased with increasing gravel content.Compared with control check treatment with gravel content of 0%,soil water absorption rates in the treatments with gravel contents of 10%,20%,30%,40%,and 50%decreased by 11.47%,17.97%,25.24%,29.83%,and 42.45%,respectively.As the gravel content increased,inverse intake suction gradually increased,and shape coefficient,K_(s),θ_(s),andθ_(r)gradually decreased.For the same soil water content,soil water suction and K_(θ)gradually decreased with increasing gravel content.At the same soil water suction,C(h)decreased with increasing gravel content,and the water use efficiency worsened.Overall,the water holding capacity,hydraulic conductivity,and water use efficiency of stony soil in the eastern foothills of the Helan Mountains decreased with increasing gravel content.This study could provide data support for improving soil water use efficiency in the eastern foothills of the Helan Mountains and other similar rocky mountainous areas.展开更多
Suitable vineyard soils enhance soil stability and biodiversity which in turn protects roots against erosion and nutrient losses. There is a lack of information related to inexpensive and suitable methods and tools to...Suitable vineyard soils enhance soil stability and biodiversity which in turn protects roots against erosion and nutrient losses. There is a lack of information related to inexpensive and suitable methods and tools to protect the soil in Mediterranean sloping vineyards(>25° of slope inclination). In the vineyards of the Montes de Málaga(southern Spain), a sustainable land management practice that controls soil erosion is actually achieved by tilling rills in the down-slope direction to canalize water and sediments. Because of their design and use, we call them agri-spillways. In this research, we assessed two agri-spillways(between 10 m and 15 m length, and slopes between 25.8° and 35°) by performing runoff experiments under extreme conditions(a motor driven pump that discharged water flows up to 1.33 l s^(-1) for 12 to 15 minutes: ≈1000 l). The final results showed: i) a great capacity by these rills to canalize large amounts of water and sediments; and, ii) higher water flow speeds(between 0.16 m s-1 and 0.28 m s^(-1)) and sediment concentrationrates(up to 1538.6 g l^(-1)) than typically found in other Mediterranean areas and land uses(such as badlands, rangelands or extensive crops of olives and almonds). The speed of water flow and the sediment concentration were much higher in the shorter and steeper rill. We concluded that agri-spillways, given correct planning and maintenance, can be a potential solution as an inexpensive method to protect the soil in sloping Mediterranean vineyards.展开更多
To gain insight into the inelastic behavior of piles, the response of a vertical pile embedded in dry sand and subjected to cyclic lateral loading was studied experimentally in centrifuge tests conducted in Laboratoir...To gain insight into the inelastic behavior of piles, the response of a vertical pile embedded in dry sand and subjected to cyclic lateral loading was studied experimentally in centrifuge tests conducted in Laboratoire Central des Ponts et Chaussees. Three types of cyclic loading were applied, two asymmetric and one symmetric with respect to the unloaded pile. An approximately square-root variation of soil stiffness with depth was obtained from indirect in-flight density measurements, laboratory tests on reconstituted samples, and well-established empirical correlations. The tests were simulated using a cyclic nonlinear Winkler spring model, which describes the full range of inelastic phenomena, including separation and re-attachment of the pile from and to the soil. The model consists of three mathematical expressions capable of reproducing a wide variety of monotonic and cyclic experimentalp-y curves. The physical meaning of key model parameters is graphically explained and related to soil behavior. Comparisons with the centrifuge test results demonstrate the general validity of the model and its ability to capture several features of pile-soil interaction, including： soil plastification at an early stage of loading, ＂pinching＂ behavior due to the formation of a relaxation zone around the upper part of the pile, and stiffness and strength changes due to cyclic loading. A comparison of the p-y curves derived from the test results and the proposed model, as well as those from the classical curves of Reese et al. （1974） for sand, is also presented.展开更多
In this paper, field experimental comparison is made between a small track-type experimental prototype skidder and a J-50 skidding tractor. Experimental data, including skidding productivity, soil compaction on skiddi...In this paper, field experimental comparison is made between a small track-type experimental prototype skidder and a J-50 skidding tractor. Experimental data, including skidding productivity, soil compaction on skidding trails, and damage rate of the residual trees, are analyzed. The results indicate that with the condition of scattered skidding area and low skidding volume per cycle, small track-type experimental prototype skidder has advantage on working and a higher skidding productivity. It makes lower soil compaction to the skidding trails in the depth of 0-5 cm, 5-10 cm, and 10-15 cm. Under the same work conditions, the damage rate of the residual trees made by small track-type experimental prototype skidder is only 1/5 of those made by J-50 type skidding tractor. The damage rate is reduced by 80%.展开更多
文摘The Tianshui Experimental Site of Soil and Water Conservation was set up in 1942.Then the first construction publicized the thinking of soil and water conservation,and popularized the technologies of soil and water conservation and related plants.Their efforts established the foundation of the science of soil and water conservation with the first high-tech and high quality R&D team,and pushed the research of soil and water conservation building on the stage of systematization.All of this provided rare good scientific data and theoretical support for the soil and water conservation and the development of the regional economy in Northwest China.
基金supported by the National Natural Science Foundation of Sichuan Province(22NSFSC0191,22NSFSC3990)。
文摘The combined application of mineral fertilizer and biochar significantly improves the passivation of heavy metal-contaminated soil,surpassing the effects of individual application.This study has reinforced the validation of their passivation competence as soil remediation agents by examining the multifaceted role of potassium-silicon-calcium mineral fertilizer combined with rice husk-based biochar generated at different pyrolysis temperatures.The soil leaching column experiment,conducted based on the adsorption experiments,has facilitated our scrutiny of the passivation impacts of cadmium(Cd)and lead(Pb)when introducing different proportions of mineral fertilizers and biochar into the soil.These results indicate that biochar’s adsorption efficiency for Cd and Pb is significantly improved at escalated pyrolytic temperature conditions in a single solution.The biochar generated at 700℃(C700)renders adsorption effectiveness of approximately 84.24%for Cd and 99.74%for Pb.Biochar conspicuously registers superior adsorption efficiency towards Pb relative to Cd.The mineral fertilizer,which achieves an adsorption efficiency of 97.76%for Cd,is identified as the main adsorbent for Cd,although its competence is slightly lower compared to C700 for Pb adsorption.Within a complex solution,biochar and mineral fertilizer show reduced Cd and Pb adsorption levels compared to single solutions.There is a keen competition for adsorption surfaces witnessed between Cd and Pb,with Pb’s distribution coefficient(Kd)notably outpacing that of Cd.The isothermal adsorption analyses depict that the mineral fertilizer follows the Langmuir model for Cd adsorption,while C700 conveys the Freundlich model for Pb adsorption.The soil leaching column experiment’s results signify that the composite passivation agents significantly outperform the individual passivation agents in efficiency.The combined application of biochar and mineral fertilizer minimizes the cumulative leaching of Cd and Pb,with the optimal soil remedy proportion for heavy metal contamination being 7∶3.In practical application,mindful consideration should be accorded to the deployment ratios of different passivation agents.
基金Sponsored by the Scienctific and Technology Project of Heilongjiang Province(Grant No.2007-04)
文摘To analyze the characteristics of solar seasonal soil thermal storage in a solar-ground coupled heat pump system (SGCHPS) in severe cold area,the software FLUENT was used to establish the three-dimensional unsteady state fluid-solid coupling mathematical model of multi-well ground heat exchanger (MWGHE).The User-Defined Functions (UDF) of solar collector and plate heat exchanger were written and dynamically loaded into the model of MWGHE as the boundary conditions.In this way,the dynamic simulation of solar seasonal soil thermal storage was realized.The comparison of simulative and experimental results showed that the overall variation trend of simulative and experimental values achieves a good agreement with time;the relative errors of simulated parameters are all in the allowable range.Therefore,it can be obtained that the models established can be applied in the investigation of performance of solar seasonal soil thermal storage.At the same time,it provides a theoretical basis for the study of heating in SGCHPS and soil heat balance analysis after long-time thermal storage and extraction.
文摘土壤是陆地生态系统中最大的有机碳库,在全球碳循环中起重要作用。土壤中铁氧化物通过矿物-有机保护作用调控有机碳的固持与矿化过程,是土壤碳循环的关键机制之一。目前土壤碳-铁耦合的实验研究已逐步拓展。为系统梳理土壤碳-铁耦合实验设计的研究进展,本研究通过Web of Science和中国知网CNKI数据库收集相关文献,运用CiteSpace进行文献计量分析。结果显示:土壤碳-铁耦合研究呈现阶段性增长,研究内容围绕氧化铁、碳封存、稳定性等关键词展开;碳-铁耦合早期研究聚焦于土壤碳、铁组成与吸附作用,近年来研究逐渐侧重土壤碳-铁耦合机制及环境响应,显示了土壤碳-铁耦合研究的内核深化与外延拓展;碳-铁耦合实验设计主要从碳与铁组分分析、铁与碳添加响应、环境因子调控、区域地理特征差异4个维度开展。现有研究已揭示碳-铁耦合机制的复杂性,但在微观机制和多因子交互作用等方面仍需加强多区域、多时空尺度的实验验证。
基金the National Key Basic Research Program (973 Program) of China (No.2002CB412303)the National Natural Science Foundation of China (No.50709009)the Key Project of Chinese Ministry of Education (No.106088).
文摘The infiltration of water contaminants into soil and groundwater systems can greatly affect the quality of groundwater. A laboratory-designed large soil tank with periodic and continuous infiltration models, respectively, was used to simulate the migration of the contaminants NH4 and NO3 in a soil and groundwater system, including unsaturated and saturated zones. The unsaturated soil zone had a significant effect on removing NH4 and NO3 infiltrated from the surface water. The patterns of breakthrough curves of NH4 and NO3 in the unsaturated zone were related to the infiltration time. A short infiltration time resulted in a single sharp peak in the breakthrough curve, while a long infiltration time led to a plateau curve. When NH4 and NO3 migrated from the unsaturated zone to the saturated zone, an interracial retardation was formed, resulting in an increased contaminant concentration on the interface. Under the influence of horizontal groundwater movement, the infiltrated contaminants formed a contamination-prone area downstream. As the contaminants migrated downstream, their concentrations were significantly reduced. Under the same infiltration concentration, the concentration of NO3 was greater than that of NH4 at every corresponding cross-section in the soil and groundwater tank, suggesting that the removal efficiency of NH4 was greater than that of NO3 in the soil and groundwater system.
文摘The relationships between rainfall, runoff and erosion in South China granitic weathering red soil region were studied by using data collected from 7 experimental plots in Wuhua County, Guangdong Province. Results showed that when rainfall is less than 50 mm, small volumes of runoff were produced. Rainfall intensity might be the main factor in controlling runoff. When rainfall exceeds 50 mm, because of its large volume and high intensity, runoff and the produced amount of erosion increased with raimfall quickly. Analysis of the relationship bebeen runoff and erosion suggsted that runoff of 30 mm (corresponding to about 50 mm rainfall might be taken as a threshold at which wter on land surface was sufficient to start the larg amount of soil particles. Vegtation cover is very effective in protection soil from being eroded. When vegetation coverag increases from 0 to 80 percent,runoff and soil loss decrease from 179.34mm/a to 126.36mm/a and 6262.15T/a km2 to 368.02 T/a km2, respectively.
文摘This study addresses firstly the soil fabric variations of loose and dense compacted soil samples during a single wetting/drying cycle at suctions between 0 and 287.9 MPa using mainly the mercury intrusion porosimetry（MIP） tests.Two suction techniques were employed to apply this wide suction range：the osmotic technique for suctions less than 8.5 MPa,and the vapor equilibrium or salt solution technique for suctions higher than 8.5 MPa.Secondly,the soil water retention curves（SWRCs） were predicted by the MIP test results for both loose and dense soil samples.A reasonable correspondence between MIP results and SWRCs was found on the wetting path at lower suctions close to saturation and on drying path at higher suctions.
基金funded by the National Natural Science Foundation of China(32360321)the Natural Science Foundation of Ningxia Hui Autonomous Region,China(2023AAC03046,2023AAC02018)the Ningxia Key Research and Development Project(2021BEG02011).
文摘The eastern foothills of the Helan Mountains in China are a typical mountainous region of soil and gravel,where gravel could affect the water movement process in the soil.This study focused on the effects of different gravel contents on the water absorption characteristics and hydraulic parameters of stony soil.The stony soil samples were collected from the eastern foothills of the Helan Mountains in April 2023 and used as the experimental materials to conduct a one-dimensional horizontal soil column absorption experiment.Six experimental groups with gravel contents of 0%,10%,20%,30%,40%,and 50%were established to determine the saturated hydraulic conductivity(K_(s)),saturated water content(θ_(s)),initial water content(θ_(i)),and retention water content(θ_(r)),and explore the changes in the wetting front depth and cumulative absorption volume during the absorption experiment.The Philip model was used to fit the soil absorption process and determine the soil water absorption rate.Then the length of the characteristic wetting front depth,shape coefficient,empirical parameter,inverse intake suction and soil water suction were derived from the van Genuchten model.Finally,the hydraulic parameters mentioned above were used to fit the soil water characteristic curves,unsaturated hydraulic conductivity(K_(θ))and specific water capacity(C(h)).The results showed that the wetting front depth and cumulative absorption volume of each treatment gradually decreased with increasing gravel content.Compared with control check treatment with gravel content of 0%,soil water absorption rates in the treatments with gravel contents of 10%,20%,30%,40%,and 50%decreased by 11.47%,17.97%,25.24%,29.83%,and 42.45%,respectively.As the gravel content increased,inverse intake suction gradually increased,and shape coefficient,K_(s),θ_(s),andθ_(r)gradually decreased.For the same soil water content,soil water suction and K_(θ)gradually decreased with increasing gravel content.At the same soil water suction,C(h)decreased with increasing gravel content,and the water use efficiency worsened.Overall,the water holding capacity,hydraulic conductivity,and water use efficiency of stony soil in the eastern foothills of the Helan Mountains decreased with increasing gravel content.This study could provide data support for improving soil water use efficiency in the eastern foothills of the Helan Mountains and other similar rocky mountainous areas.
文摘Suitable vineyard soils enhance soil stability and biodiversity which in turn protects roots against erosion and nutrient losses. There is a lack of information related to inexpensive and suitable methods and tools to protect the soil in Mediterranean sloping vineyards(>25° of slope inclination). In the vineyards of the Montes de Málaga(southern Spain), a sustainable land management practice that controls soil erosion is actually achieved by tilling rills in the down-slope direction to canalize water and sediments. Because of their design and use, we call them agri-spillways. In this research, we assessed two agri-spillways(between 10 m and 15 m length, and slopes between 25.8° and 35°) by performing runoff experiments under extreme conditions(a motor driven pump that discharged water flows up to 1.33 l s^(-1) for 12 to 15 minutes: ≈1000 l). The final results showed: i) a great capacity by these rills to canalize large amounts of water and sediments; and, ii) higher water flow speeds(between 0.16 m s-1 and 0.28 m s^(-1)) and sediment concentrationrates(up to 1538.6 g l^(-1)) than typically found in other Mediterranean areas and land uses(such as badlands, rangelands or extensive crops of olives and almonds). The speed of water flow and the sediment concentration were much higher in the shorter and steeper rill. We concluded that agri-spillways, given correct planning and maintenance, can be a potential solution as an inexpensive method to protect the soil in sloping Mediterranean vineyards.
基金EU Fifth Framework Program: Environment, Energy and Sustainable Development Research and Technological Development Activity of Generic Nature: The Fight Against Natural and Technological Hazards, Research Project QUAKER Under Contract No. EVG1–CT–2002–00064
文摘To gain insight into the inelastic behavior of piles, the response of a vertical pile embedded in dry sand and subjected to cyclic lateral loading was studied experimentally in centrifuge tests conducted in Laboratoire Central des Ponts et Chaussees. Three types of cyclic loading were applied, two asymmetric and one symmetric with respect to the unloaded pile. An approximately square-root variation of soil stiffness with depth was obtained from indirect in-flight density measurements, laboratory tests on reconstituted samples, and well-established empirical correlations. The tests were simulated using a cyclic nonlinear Winkler spring model, which describes the full range of inelastic phenomena, including separation and re-attachment of the pile from and to the soil. The model consists of three mathematical expressions capable of reproducing a wide variety of monotonic and cyclic experimentalp-y curves. The physical meaning of key model parameters is graphically explained and related to soil behavior. Comparisons with the centrifuge test results demonstrate the general validity of the model and its ability to capture several features of pile-soil interaction, including： soil plastification at an early stage of loading, ＂pinching＂ behavior due to the formation of a relaxation zone around the upper part of the pile, and stiffness and strength changes due to cyclic loading. A comparison of the p-y curves derived from the test results and the proposed model, as well as those from the classical curves of Reese et al. （1974） for sand, is also presented.
基金Sponsored by the Special Scientific Research Funds for Forest Non-profit Industry(Grant No.201104007)the Fundamental Research Funds for the Central Universities(Grant No.DL13BB10)
文摘In this paper, field experimental comparison is made between a small track-type experimental prototype skidder and a J-50 skidding tractor. Experimental data, including skidding productivity, soil compaction on skidding trails, and damage rate of the residual trees, are analyzed. The results indicate that with the condition of scattered skidding area and low skidding volume per cycle, small track-type experimental prototype skidder has advantage on working and a higher skidding productivity. It makes lower soil compaction to the skidding trails in the depth of 0-5 cm, 5-10 cm, and 10-15 cm. Under the same work conditions, the damage rate of the residual trees made by small track-type experimental prototype skidder is only 1/5 of those made by J-50 type skidding tractor. The damage rate is reduced by 80%.
