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1、Chapter 1Chapter 1 Physical propertPhysical propertiesies and and engineering classification of soilengineering classification of soil第一章 土的物理性质及工程分类土的三相组成 土的颗粒特征 土的三相比例指标 粘性土的界限含水率 无粘性土的密实度 土的工程分类本章主要内容土的生成(Formation of soil )土是岩石经风化、剥蚀、搬运、沉积 (weathering, erosion, transportation and redeposition)而形
2、成的包括固体矿物、液 体水和气体 (solid particles, liquid, gas) 的 一种集合体三类风化Physical weathering (物理风化) 指岩石经受风、霜、雨、雪的侵蚀,温度湿度的变化、不均 匀膨胀与收缩,使岩石产生裂隙,崩解为碎块。这种风化仅 改变颗粒大小与形状,不改变原来矿物成分。生成的土呈松 散状态,无粘性土 Original mineral (原生矿物) Chemical weathering (化学风化) 指岩石碎屑与空气、水和各种水溶液相接触,经氧化、碳化 和水化作用,改变原来矿物成分,形成新的矿物。生成的土 为细粒土,粘性土 Secondary
3、mineral (次生矿物) Biological weathering (生物风化) 由动物、植物和人类对岩体的破坏称生物风化 Organic matter (有机质)1.1 Components of soil (土的组成)Three phases solid phase (固相) liquid phase (液相) vapor phase (气相)AirAirAirAirSolidSolidSolidSolidWaterWaterWaterWater土体的三相比例不同,它的状态和工程性质也不同: 固体气体(液体 = 0) 干土 固体液体气体 湿土 固体液体(气体 = 0) 饱和土1. 固
4、相 (Solid phase)无机矿物颗粒(原生矿物,次生矿物)和有机 质 原生矿物(Original mineral)是岩浆在冷凝过程中形成的矿物,由物理风化而 形成 单矿物颗粒(如:石英、长石、云母等)或多矿物 颗粒(如:漂石、卵石、砾石等)组成 颗粒较为粗糙 特点:弱吸水性,性质稳定,无塑性1) 固相(续)次生矿物(Secondary mineral) 由原生矿物经过化学风化而生成 主要由粘土矿物组成 颗粒细小、扁平 特点:性质不稳定,吸水性强,体积膨胀性, 塑性 有机质(Organic matter) 由生物风化而生成 腐植质、泥炭( Muck and peat)2. 液相 (Liqu
5、id phase)重力重力水 Bulk water表面张力和重力毛细水 Capillary water自由水 Free water弱结合水 Feeble absorbed water物理化学力强结合水 Strong absorbed water结合水 Hygroscopic water (absorbed water)主要受力情况水的分类1) 结合水结合水(吸附水):受到粘土表面电分 子力的吸引 强结合水(吸着水):厚度只有几个水 分子厚,性质接近固体(有粘滞性、弹性、 抗剪强度) 弱结合水(薄膜水):呈粘滞状态,性 质也接近固体(弱于强结合水),对粘性土 的性质影响最大2) 自由水自由水:不
6、受粘土表面电 分子力的吸引。与普通水 一样,受重力支配,能传 递静水压力并具有融解作 用 重力水:地下水位以下, 只受重力规律支配,具有浮 力作用 毛细水:地下水位以上, 受到表面张力和重力的作 用,对土粒不产生浮力Height of capillary rise, h h h hc c c c= = = = f(df(df(df(d) ) ) )Diameter of tube, d d d d3. 气相(Vapor phase)1) Free air (自由气体)与大气连通,对土的工程性质影响小 2) Sealing foam (封闭气泡) 影响土的性质 (压缩性,渗透性等)Free ai
7、rFree airFree airFree airSolidSolidSolidSolidWaterWaterWaterWaterSealing foamSealing foamSealing foamSealing foam1.2 土的颗粒特征1. 土粒粒组的划分 粒径(粒度):与实际土颗粒体积相等的当 量小球体的直径 粒组:大小相近的土粒合并而成粒组 Huge grain group (巨粒组) Coarse grain group (粗粒组) Fine grain group (细粒组)Six grain groups表 1-1 粒组划分标准粒径 d (mm)0.0050.0752602
8、00Clay (粘 粒)Silt (粉 粒)Sand ( 砂 粒)Gravel (砾石)Cobble (卵石) Macadam(碎石)Boulder (漂石) Rubble (块石)Huge grain groupCoarse grain groupFine grain group2 土粒组成的表示方法土的粒径级配:土中不同粒组的相对含量 (各粒组干土质量的百分比) 表示方法:表格法三角坐标法以累计百分含量表示颗粒分布(累积)曲线法以粒组表示粒组频率曲线法曲线法1)表格法-累积百分含量表示法表1-21)表格法-粒组表示法表1-32) 曲线法:两类曲线Percentage of particle
9、s by Percentage of particles by Percentage of particles by Percentage of particles by weight smaller than size shownweight smaller than size shownweight smaller than size shownweight smaller than size shownGrain diameter of Grain diameter of Grain diameter of Grain diameter of soil (mm)soil (mm)soil
10、 (mm)soil (mm)O100大小lgd (mm)Percentage of each grain group Percentage of each grain group Percentage of each grain group Percentage of each grain group particles by weightparticles by weightparticles by weightparticles by weightGrain diameter of Grain diameter of Grain diameter of Grain diameter of
11、soil (mm)soil (mm)soil (mm)soil (mm)O100大小lgd (mm)Particle size distribution curveParticle size distribution curveParticle size distribution curveParticle size distribution curveGrain group frequency curveGrain group frequency curveGrain group frequency curveGrain group frequency curveNote: the diff
12、erence lies in the vertical coordinatesNote: the difference lies in the vertical coordinatesNote: the difference lies in the vertical coordinatesNote: the difference lies in the vertical coordinates累积曲线的应用根据粒径分布曲线,可以得到: 每一粒组的相对含量 特征粒径 不均匀系数Cu 曲率系数Cc特征粒径:不均匀系数:反映曲线的坡度60 u 10dCd=2 30 c 1060()dCd d=曲率系
13、数: 反映曲线的形状根据Cu 和 Cc 可以划分土的粒径级配.(Fig. 5, Fig.6)d60, d30, d10 denote that 60%, 30%, 10% of the particles which is smaller than that size in grading curves d60: limiting size (限定粒径) d10: effective size (有效粒径)(1-2)(1-3)Grain diameter of soil (mm)Grain diameter of soil (mm)Grain diameter of soil (mm)Grai
14、n diameter of soil (mm)Percentage of particles by weight Percentage of particles by weight Percentage of particles by weight Percentage of particles by weight smaller than size shown (%)smaller than size shown (%)smaller than size shown (%)smaller than size shown (%)0 0 0 010101010202020203030303040
15、4040405050505060606060707070708080808090909090100100100100100100100100101010101 1 1 10.10.10.10.10.010.010.010.010.0010.0010.0010.001Soil BSoil BSoil BSoil B Soil ASoil ASoil ASoil ASoil CSoil CSoil CSoil CFig.5Fig.5Fig.5Fig.5 Particle size distribution curves of three different soilsParticle size d
16、istribution curves of three different soilsParticle size distribution curves of three different soilsParticle size distribution curves of three different soilsCurve A:low degree of slope the difference between d60 and d10 is large Cu is large more non-uniform well- graded (曲线平缓,Cu大,不均匀,级配良好) Curve B:high degree of slope the difference between d60 and d10 is small Cu is small less non-uniform poorly graded (曲线陡,Cu小,均