木材密度包括基本密度、气干密度等,在12%含水率条件下的气干密度(D12)较常用,因此有必要将木材气干密度换算为基本密度(Db)。目前利用木材气干密度计算基本密度的模型有Reyes、Chave、Simpson和Vieilledent模型等,然而这些模型预测结...木材密度包括基本密度、气干密度等,在12%含水率条件下的气干密度(D12)较常用,因此有必要将木材气干密度换算为基本密度(Db)。目前利用木材气干密度计算基本密度的模型有Reyes、Chave、Simpson和Vieilledent模型等,然而这些模型预测结果不完全一致。利用中国林业科学研究院木材工业研究所(Research Institute of Wood Industry,Chinese Academy of Forestry,CRIWI)和法国农业国际合作研究发展中心(French Agricultural Research Centre for International Development,CIRAD)的木材D12和Db数据,首先基于CRIWI的木材密度数据建立D12与Db的关系模型,然后将CRIWI和CIRAD的D12数据分别代入Reyes模型、Chave模型、Simpson模型、Vieilledent模型和新建模型,获得每个树种木材Db的预测值,并根据Db预测值和实测值计算残差绝对值均值。不同模型残差绝对值均值比较结果表明:Reyes模型在利用CRIWI和CIRAD的木材密度数据时预测Db的准确性都比较高,适用性最广;Simpson模型、新建模型在D12高于1.0 g/cm3时预测Db的准确性降低。展开更多
中国广泛分布砂岩地层,其水力特性影响工程稳定性。干密度是土水特征曲线的重要影响因素,但其对砂岩土水特征曲线的影响机制尚不明确。为了探究不同干密度砂岩土水特征曲线及其微观特性,采用压力板仪开展了不同干密度砂岩土水特征试验,...中国广泛分布砂岩地层,其水力特性影响工程稳定性。干密度是土水特征曲线的重要影响因素,但其对砂岩土水特征曲线的影响机制尚不明确。为了探究不同干密度砂岩土水特征曲线及其微观特性,采用压力板仪开展了不同干密度砂岩土水特征试验,提出了考虑干密度的砂岩土水特征曲线模型,同时,基于扫描电镜(scanning electron microscope, SEM)和压汞测试分析了不同干密度砂岩微观特性,揭示了干密度对砂岩土水特征曲线影响的微观机理。研究表明:干密度越大,砂岩持水能力越强;干密度对砂岩进气值和残余饱和度均有影响,且砂岩进气值随着干密度的增大呈近似线性增长;不同干密度砂岩孔径分布均为单峰形态,随着干密度的增大,砂岩峰值孔隙半径逐渐减小;干密度较高的砂岩,颗粒排列紧密,孔隙半径较小,主要以中等和小孔隙为主,而干密度较低的砂岩,颗粒排列松散,孔隙半径大,包括大小不等的孔隙。研究可为非饱和砂岩工程安全提供一定的参考。展开更多
非饱和土广泛地存在于自然界和工程领域,其工程性质和行为特征备受关注,对工程建设安全性和地质环境稳定性至关重要。土–水特征曲线(SWCC)作为描述非饱和土的基本工具,揭示了土壤湿度状态与基质吸力的变化关系,其形状和参数与土壤力学...非饱和土广泛地存在于自然界和工程领域,其工程性质和行为特征备受关注,对工程建设安全性和地质环境稳定性至关重要。土–水特征曲线(SWCC)作为描述非饱和土的基本工具,揭示了土壤湿度状态与基质吸力的变化关系,其形状和参数与土壤力学行为、渗透性及工程应用紧密相关,而干密度的变化则直接影响土体的孔隙结构、持水性能和力学响应。基于此,本研究基于压力板仪,开展土–水特征曲线测试,探究了不同干密度条件下粉质黏土土–水特征曲线的变化规律。结果表明:土样的干密度对土–水特征曲线的变化具有显著影响,相同基质吸力下,初始干密度越大的试件对应的质量含水率越小,随着干密度的增大,试件之间质量含水率的差异逐渐减小;当基质吸力由0增大至500 kPa时,干密度为1.5、1.6、1.7 g/cm3的试件的质量含水率分别减小了11.1%、10.7%、9.8%;基于VG模型,建立考虑干密度的土–水特征曲线模型,可快速预测山东某地区粉质黏土土–水特征曲线,提供便捷途径。Unsaturated soil widely exists in nature and engineering fields. Its engineering properties and be- havior characteristics have attracted much attention, which is very important for the safety of engineering construction and the stability of the geological environment. The soil-water characteristic curve (SWCC), as a basic tool to describe unsaturated soil, reveals the relationship between soil moisture state and matric suction. Its shape and parameters are closely related to soil mechanical behavior, permeability, and engineering application. The change of dry density directly affects the pore structure, water holding capacity and mechanical response of soil. Based on this, this study carried out the soil-water characteristic curve test based on the pressure plate instrument and explored the variation law of the soil-water characteristic curve of silty clay under different dry density conditions. The results show that the dry density of the soil sample has a significant effect on the change of the soil-water characteristic curve. Under the same matrix suction, the larger the initial dry density, the smaller the corresponding mass moisture content of the specimen. With the increase of dry density, the difference of mass moisture content between specimens gradually decreases. When the matric suction increased from 0 to 500 kPa, the mass water content of the specimens with dry density of 1.5, 1.6 and 1.7 g/cm3 decreased by 11.1 %, 10.7 % and 9.8 %, respectively. Based on the VG model, a soil-water characteristic curve model considering dry density is established, which can quickly predict the soil-water characteristic curve of silty clay in a certain area of Shandong and provide a convenient way.展开更多
文摘木材密度包括基本密度、气干密度等,在12%含水率条件下的气干密度(D12)较常用,因此有必要将木材气干密度换算为基本密度(Db)。目前利用木材气干密度计算基本密度的模型有Reyes、Chave、Simpson和Vieilledent模型等,然而这些模型预测结果不完全一致。利用中国林业科学研究院木材工业研究所(Research Institute of Wood Industry,Chinese Academy of Forestry,CRIWI)和法国农业国际合作研究发展中心(French Agricultural Research Centre for International Development,CIRAD)的木材D12和Db数据,首先基于CRIWI的木材密度数据建立D12与Db的关系模型,然后将CRIWI和CIRAD的D12数据分别代入Reyes模型、Chave模型、Simpson模型、Vieilledent模型和新建模型,获得每个树种木材Db的预测值,并根据Db预测值和实测值计算残差绝对值均值。不同模型残差绝对值均值比较结果表明:Reyes模型在利用CRIWI和CIRAD的木材密度数据时预测Db的准确性都比较高,适用性最广;Simpson模型、新建模型在D12高于1.0 g/cm3时预测Db的准确性降低。
文摘中国广泛分布砂岩地层,其水力特性影响工程稳定性。干密度是土水特征曲线的重要影响因素,但其对砂岩土水特征曲线的影响机制尚不明确。为了探究不同干密度砂岩土水特征曲线及其微观特性,采用压力板仪开展了不同干密度砂岩土水特征试验,提出了考虑干密度的砂岩土水特征曲线模型,同时,基于扫描电镜(scanning electron microscope, SEM)和压汞测试分析了不同干密度砂岩微观特性,揭示了干密度对砂岩土水特征曲线影响的微观机理。研究表明:干密度越大,砂岩持水能力越强;干密度对砂岩进气值和残余饱和度均有影响,且砂岩进气值随着干密度的增大呈近似线性增长;不同干密度砂岩孔径分布均为单峰形态,随着干密度的增大,砂岩峰值孔隙半径逐渐减小;干密度较高的砂岩,颗粒排列紧密,孔隙半径较小,主要以中等和小孔隙为主,而干密度较低的砂岩,颗粒排列松散,孔隙半径大,包括大小不等的孔隙。研究可为非饱和砂岩工程安全提供一定的参考。
文摘非饱和土广泛地存在于自然界和工程领域,其工程性质和行为特征备受关注,对工程建设安全性和地质环境稳定性至关重要。土–水特征曲线(SWCC)作为描述非饱和土的基本工具,揭示了土壤湿度状态与基质吸力的变化关系,其形状和参数与土壤力学行为、渗透性及工程应用紧密相关,而干密度的变化则直接影响土体的孔隙结构、持水性能和力学响应。基于此,本研究基于压力板仪,开展土–水特征曲线测试,探究了不同干密度条件下粉质黏土土–水特征曲线的变化规律。结果表明:土样的干密度对土–水特征曲线的变化具有显著影响,相同基质吸力下,初始干密度越大的试件对应的质量含水率越小,随着干密度的增大,试件之间质量含水率的差异逐渐减小;当基质吸力由0增大至500 kPa时,干密度为1.5、1.6、1.7 g/cm3的试件的质量含水率分别减小了11.1%、10.7%、9.8%;基于VG模型,建立考虑干密度的土–水特征曲线模型,可快速预测山东某地区粉质黏土土–水特征曲线,提供便捷途径。Unsaturated soil widely exists in nature and engineering fields. Its engineering properties and be- havior characteristics have attracted much attention, which is very important for the safety of engineering construction and the stability of the geological environment. The soil-water characteristic curve (SWCC), as a basic tool to describe unsaturated soil, reveals the relationship between soil moisture state and matric suction. Its shape and parameters are closely related to soil mechanical behavior, permeability, and engineering application. The change of dry density directly affects the pore structure, water holding capacity and mechanical response of soil. Based on this, this study carried out the soil-water characteristic curve test based on the pressure plate instrument and explored the variation law of the soil-water characteristic curve of silty clay under different dry density conditions. The results show that the dry density of the soil sample has a significant effect on the change of the soil-water characteristic curve. Under the same matrix suction, the larger the initial dry density, the smaller the corresponding mass moisture content of the specimen. With the increase of dry density, the difference of mass moisture content between specimens gradually decreases. When the matric suction increased from 0 to 500 kPa, the mass water content of the specimens with dry density of 1.5, 1.6 and 1.7 g/cm3 decreased by 11.1 %, 10.7 % and 9.8 %, respectively. Based on the VG model, a soil-water characteristic curve model considering dry density is established, which can quickly predict the soil-water characteristic curve of silty clay in a certain area of Shandong and provide a convenient way.
