第六章土壤孔性与结构性 soil porosity and structure 质量 体积 空气质量=0 空气体积 心孔度 水的质量 水体积 土粒质量 体 积 固体体积
第六章 土壤孔性与结构性 soil porosity and structure
第一节土壤孔性 soil porosity
第一节 土壤孔性 soil porosity
B C Sand-sized 物 particles Clay and silt- sIZed particles Pores +1/64 inch- Figure 1. A, Section through sand showing"packing"betwcen the grains B. Seetion through a loamy sand showing concentrations of elay and silt panicles at the points of contact between sand grains, reducing the size of the pores between the sand grains It is important to note that the clay and silt material itself possesses porosity due to very fine"packing"of pores between silt and clay particles. C. Section through a sandy loam showing a typical assembly of sand, silt, and clay particles into aggregates. Large pores exist primarily between aggregates and constitute a smaller proportion of the sail than in sand or loamy sand. As in B it is important to note that the clay and silt portion of this soil itself possesses orosi ty comprising much smaller pores than can be shown her
土壤孔隙状况 土壤是一个疏松多孔体,既有颗粒与颗粒之问的粒 间孔隙,也有团聚体与因聚体之间的结枸孔隙。孔隙 的大小、几何形状、多少以及在土壤不同层次中分配 关糸都是极为复杂的。所以,土壤孔隙具有发生学特 征和意义。 土壤孔隙担负着保存水分和通气(气体交换)双重 功能。孔陳大小和多小对于协调土壤水气矛盾至关重 要。土壤孔隙是微生物活动的场所,是植物根糸仲畏 的主要通道。可见,孔隙性状是土壤的重要质量指标
土壤孔隙状况 土壤是一个疏松多孔体，既有颗粒与颗粒之间的粒 间孔隙，也有团聚体与团聚体之间的结构孔隙。孔隙 的大小、几何形状、多少以及在土壤不同层次中分配 关系都是极为复杂的。所以，土壤孔隙具有发生学特 征和意义。 土壤孔隙担负着保存水分和通气（气体交换）双重 功能。孔隙大小和多少对于协调土壤水气矛盾至关重 要。土壤孔隙是微生物活动的场所，是植物根系伸展 的主要通道。可见，孔隙性状是土壤的重要质量指标
土壤孔隙数量 (一)孔隙度 1.土壤颗粒密度( soil particle density)(ρs(PD 概念:单位容积圄体土粒(不包括粒间孔隙的容积)的质量称为土 壤密度。(克/厘米3) Particle density will also be determined for this soil particle density only takes into account the volume occupied by the solid particles. It excludes the volume occupied by air and water 定义式 M 式中:M固相颗粒质量(g)V固相容积(cm3) 土壤比重(真比重)( soil specific gravity):单位容积固体土粒 的质量与4C肘同体积水重之比。已知4C时水的密度为1。所以, 土壤比重和颗粒密度大小相等,区别在于颗粒密度有量纲,而比 重没有量纲。经常被人们当作一个概念应用
一.土壤孔隙数量 （一）孔隙度 1.土壤颗粒密度(soil particle density)（ρs )（PD） 概念：单位容积固体土粒(不包括粒间孔隙的容积)的质量称为土 壤密度。（克/厘米3） Particle density will also be determined for this soil. Particle density only takes into account the volume occupied by the solid particles. It excludes the volume occupied by air and water 式中：Ms固相颗粒质量（g）Vs固相容积（cm3 ） s s s V M 定义式 = 土壤比重（真比重）（soil specific gravity）：单位容积固体土粒 的质量与4℃时同体积水重之比。已知4℃时水的密度为1。所以， 土壤比重和颗粒密度大小相等，区别在于颗粒密度有量纲，而比 重没有量纲。经常被人们当作一个概念应用
土壤孔隙数量 影响土壤比重的因素: 土壤比重仅仅取决于土壤固相颗粒的物质组成。 Since a large portion of most soils is composed of particles derived from quartz minerals, the particle density of most soils is near 2. 6g/cc which is the density of quartz. Variations in the particle density are due to the presence of heavier minerals like iron oxides or lighter organic components 表4-1土壤中常见组分的密度(克/厘米3) 2.60~2.68 赤铁矿 4.90~5.30 正长石 磁铁矿 5.03~5.18 斜长石 2.62~2.76 水铝石 2.30~240 白云母 2.77~288 高岭石 2.61~268 黑云母 2.70~3.10 蒙皂石 2.53~2.74 角闪石 2.85~3.57 伊利石 3.15~3.90 纤铁矿 腐殖质 140~1.80
一.土壤孔隙数量 影响土壤比重的因素： 土壤比重仅仅取决于土壤固相颗粒的物质组成。 Since a large portion of most soils is composed of particles derived from quartz minerals, the particle density of most soils is near 2.6 g/cc, which is the density of quartz. Variations in the particle density are due to the presence of heavier minerals like iron oxides or lighter organic components. 表 4-1 土壤中常见组分的密度 (克/厘米 3 ) 石 英 正长石 斜长石 白云母 黑云母 角闪石 辉 石 纤铁矿 2.60～2.68 2.54～2.57 2.62～2.76 2.77～2.88 2.70～3.10 2.85～3.57 3.15～3.90 3.60～4.10 赤铁矿 磁铁矿 三水铝石 高岭石 蒙皂石 伊利石 腐殖质 4.90～5.30 5.03～5.18 2.30～2.40 2.61～2.68 2.53～2.74 2.60～2.90 1.40～1.80
土壤孔隙数量 土壤比重值:绝大多数矿物的比重为2.60~2.70之间,对于 矿质土壤而言,经常取其中间值2.65作为土壤比重近视值。 土壤比重与质地关糸:砂质土壤比重值与石英接近,而粘 质土壤含铁、镁矿物较多,比重一般较大。 有机质合量高的土壤比重小。所以,耕层土壤比重比底层 土壤小。 问题:1.比重与土壤压实程度有关糸吗? 2.土壤比重与土壤干湿程度有关糸吗? 3.土壤比重具有诊断特性的意义何在(土壤相对稳定 的性质)表4-2一种森林土壤表层各级土粒的密度 粒级(粒径毫米) 腐殖质(克/千克) 密度(克/厘米3) 全土样 29.5 2.62 0.10~005 0 2.66 0.05~001 4.3 2.66 0.01~0005 14.8 2.62 0.005~0.001 53.7 <0.001 64.2 2.59
一.土壤孔隙数量 土壤比重值： 绝大多数矿物的比重为2.60~2.70之间，对于 矿质土壤而言，经常取其中间值2.65作为土壤比重近视值。 土壤比重与质地关系：砂质土壤比重值与石英接近，而粘 质土壤含铁、镁矿物较多，比重一般较大。 有机质含量高的土壤比重小。所以，耕层土壤比重比底层 土壤小。 问题：1.比重与土壤压实程度有关系吗? 2.土壤比重与土壤干湿程度有关系吗？ 3.土壤比重具有诊断特性的意义何在（土壤相对稳定 的性质） 表 4－2 一种森林土壤表层各级土粒的密度 粒级（粒径毫米） 腐殖质（克/千克) 密度(克/厘米 3 ) 全土样 0.10～0.05 0.05～0.01 0.01～0.005 0.005～0.001 <0.001 29.5 0 4.3 14.8 53.7 64.2 2.62 2.66 2.66 2.62 2.59 2.59
土壤孔隙数量 土壤比重测定方法:比重瓶法 注意!测定 比重用扰动 土
一.土壤孔隙数量 土壤比重测定方法：比重瓶法 注意！测定 比重用扰动 土
Specific gravity(G is a property of the mineral or not to 500 or 1000 ml rock material forming soil grains same scale] density jar Pycnometer) It is defined as for coarse soils mass of a soil grain 50 ml SG Bottle s mass of an equal volume of water for fine soils Method of measurement For fine soils a 50 ml density bottle may be used; for coarse soils a 500 ml or 1000 ml jar. The jar is weighed empty(Mi). a quantity of dry soil is placed in the jar and the jar weighed(M2 ). The jar is filled with water, air removed by stirring, and weighed again(M3). The jar is emptied, cleaned and refilled with water-and weighed again(Md) Mass of so il Mass of water displaced by soil 2 The range ofGs for common soils is 2.64 to 2.72
Specific gravity (Gs ) is a property of the mineral or rock material forming soil grains. It is defined as Method of measurement For fine soils a 50 ml density bottle may be used; for coarse soils a 500 ml or 1000 ml jar. The jar is weighed empty (M1 ). A quantity of dry soil is placed in the jar and the jar weighed (M2 ). The jar is filled with water, air removed by stirring, and weighed again (M3 ). The jar is emptied, cleaned and refilled with water - and weighed again (M4 ). [The range of Gs for common soils is 2.64 to 2.72]
Volume-weight properties volumes Soil sample Air volume of Voids ater Solid Volume of Solids Soil model The volume-weight properties of a soil define its state Measures of the amount of void space, amount of water and the weight of a unit volume of soil are required in engineering analysis and design Soil comprises three constituent phases Solid: rock fragments, mineral grains or flakes, organic matter Liquid: water, with some dissolved compounds(e.g. salts) Gas: air or water vapour In natural soils the three phases are intermixed. To aid analysis it is convenient to consider a soil model in which the three phases are seen as separate, but still in their correct proportions
Volume-weight properties The volume-weight properties of a soil define its state. Measures of the amount of void space, amount of water and the weight of a unit volume of soil are required in engineering analysis and design. Soil comprises three constituent phases: Solid: rock fragments, mineral grains or flakes, organic matter. Liquid: water, with some dissolved compounds (e.g. salts). Gas: air or water vapour. In natural soils the three phases are intermixed. To aid analysis it is convenient to consider a soil model in which the three phases are seen as separate, but still in their correct proportions
