chapter 5 Groundwater 第五章 地 下 水

1. chapter 5 Groundwater 第五章 地 下 水

2. Definition of groundwater: Groundwater is that part of water which exits in the space of rock’s, soil’ pore below ground surface. Groundwater is precious naturalresource to human being, But it’s a factors of reducing the strength of the rock and soils. According to the statistics, Nearly 80% engineering geological problems were caused by the existing of groundwater. So the study on groundwater is very important for a geotechnical(岩土工程) engineer.

3. 地下水的基本概念

4. The main topic of chaper 5 §5-1 The physical properties and chemical composition of groundwater §5-2 The classification of groundwater engineering properties §5-3 Moving law of groundwater §5-4 The influence of ground water to the engineering

5. § 5-1 The physical properties and chemical composition of groundwater 一.The physical properties of groundwater temperature color taste transparent smell radioactivity

6. 二. Chemical composition of groundwater Groundwater is a kind of solvent, resolving the soluble composition from rock or soil , so groundwater is full of ions. 1 .The main ion in G Cation阳离子: H+, Na+, K+, Mg2+, Ca2+, Fe2+ Anion阴离子: OH-, Cl-, SO42-, NO2, HCO3-, CO32-, SiO32-, PO42- HCO3-→bicarbonate CO32-→carbonate SO42-→sulfate Cl→chlorate SiO32-→silicate PO42-→phosphate

7. 2.The main gas composition O2→oxygen N2→nitrogen CO2→carbondioxide →from karst area, →plant respiration H2S→sulfate hydrogen exiting confining environment Esp. Oil layer

8. 3.The main colloid(胶体) and organism in G. SiO2 Fe(OH)3 hydroxide Al(OH)3 hydroxide aluminum chemical combination The function of colloid and organism on engineering is indirect, because they may change chemical composition of G.

9. § 5-2 The classification of groundwater and its engineering properties 1 According to the temperature over cold water <0℃ cold water 0-20℃ warm water 20-40℃ hot water 40-100℃ over hot water >100℃

10. According to existing state • gaseous state water（气态水） • liquid state water（液态水） • solid state water （固态水）

11. 3 According to the medium of containing water Karst water(岩溶水) Fracture water（裂隙水） Pore water（孔隙水）

12. 按含水介质的不同，对地下水的分类 Pore water（孔隙水） Fracture water（裂隙水）

14. gravity water（重力水） capillary water(毛细水) free water（自由水） absorbed water（结合水） Strong absorbed water （强结合水） Weak absorbed water （弱结合水） 4 According to interaction between water and its medium

15. Contact point of gas, liquid,solid Column cup diameter of soil grain unit weight of water tension farce of surface （1）Capillary Water Capillary water is controlled by capillarity(毛细作用（surface tension force）

16. the law of is: ◆ the bigger d, the quicker of the speed of capillary water ◆The smaller d, the higher the hc of capillary water, but if d<0.002mm, no capillary water. ◆ silty clay (粉质粘土) and Clay silt (粘质粉土) is most obvious medium for capillary water existing Capillary rise (hc) Capillary fringe(zone) Water table

17. The engineering meaning of capillary water Ground frozen expansion 地面冻胀 Ice lens body 冰透镜体 Ground frozen 地面冻胀 沼泽地（湿地） Marshland (salinized soil)

18. Soil grain Strong absorbed water Free water Weak absorbed water （2） Gravity Water The gravity water is only controlled by gravity (in movement) （3） Absorbed Water water is extra-molecular(极性分子),and the surface of clay grain have negative charge负电荷。

19. 5 According to the storage condition Stagnant water ◈ Air-containing zone Suspending water Impermeable layer (1) Suspending water (2) Stagnant water stagnant water may have bad influence to engineering in limited areas

20. Phreatic surface Movement direction (3) Phreatic Water Phreatic water is below the ground surface, above the first impermeable layer, and has free water surface.

21. 地下水的埋藏类型 上层滞水 潜水埋藏深度 毛细带水 潜水面 潜水 潜水含水 层厚度 隔水底板

22. 地下水的补给、排泄

23. 潜水面形态的变化规律 受地形和河流位置的影响 受底板隔水层高度变化的影响 受含水介质渗透性变化的影响

24. Featuresof phreatic water: ①charging: precipitation and river discharging: river, evaporation, spring ②distribution controlled by impermeable layer or permeable layer and topography ③water level change controlled by weather condition ④chemical composition depending on the circulating speed of ground water and the composition of Water medium and pollution. ⑤ The influence of phreatic water to engineering --frozen expansion --change the strength of soil or rock

25. Pressure-bearing area 承压区 Discharging area 排泄区 recharging area 补给区 Spring 泉 aquifer 含水层 Confined Water 承压水 (4) Confined Water(pressure water)

26. 地下水的埋藏类型 排泄区 补给区 承压区 自流区 承压水 流向

28. Featuresof pressure water: ①recharge is in striped way discharge movement is finished by spring, ②distribution controlled by the distribution of confining layer. ③water level change water table change has no obvious seasonal features ④chemical composition pollution is hard to recover ⑤ The influence of pressure water to engineering

29. H M

30. 截面1 h1 L h2 截面2 A:水 箱截面积 Bucket 水箱 Q Soils sample 土样 L： 渗透路径 h1: 截面1水头 h2 ：截面2水头 Q: 流量 § 5-3 Moving law of groundwater

31. Q: rate of flow (m3/d) A: cross area (m2) L: traveling distance I: hydraulic gradient K: permeability coefficient I : to indicate the water head loss in unit traveling Distance.

32. Darcy law: sand： clay soil： seepage velocity(m/d) initial hydraulic gradient which indicate the value of hydraulic gradient when the ground water begin moving. K indicate the ability of soil (or rock) permitting water to pass

33. 单位体 积土体 unit weigh of water hydraulic gradient dynamic water pressure 水流 § 5-4 The influence of ground water to the engineering 一、seepage failure（渗透破坏） Quicksand (flowing sand) or piping ▣Quicksand流砂 The definition of dynamic water pressure

34. 为流砂发生的条件

35. ▣ piping: （管涌） Under the action of GD, the fine soil grain will be carried away through chinks among coarse soil grain

36. 1 diameter of soil grain (d) 0.05—0.005 粉细砂 2 quicksand: houngenous soils piping: heterogeneous soils 3 流砂和管涌发生条件

37. 基坑的流砂或管涌 坝基的流砂或管涌

38. H h H Uplift pressure 二、Ground water table lowering cause the settlement of soft ground base