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Chapter 8.5 Ground Water Related Issues on Engineering Geology课程教案、知识点、字幕

同学们好

欢迎来到地质学与工程地质课程

地下水是地质环境的重要组成部分

也是外力地质作用中最为活跃的因素

人类在推动经济高速发展的同时

也给地下水环境造成了一定的影响

这节课我们来学习

由于地下水环境改变

而引起的一些工程地质问题

主要包括地面沉降、地面塌陷

渗透破坏及基坑突涌

土体它是由土体颗粒骨架及孔隙构成的

在土体饱和的情况下

地下水充满了土体内的孔隙

这样土体颗粒骨架和水

共同承担来自上面的压力

土体骨架承担的应力就是有效应力

而孔隙水承担的部分称为孔隙水压力

大家想一想

如果由于地下水的过度开采

或者由于某种原因引起地下水位的下降

是不是将导致孔隙水压力的减小

为了达到原始应力平衡 有效应力必然会增加

这种作用将导致土体被压缩

孔隙体积减小

从而产生地面沉降现象

一般的粘性土它的孔隙率比较大

所以压缩性也比较高

通常比砂土大一到两个数量级

所以一般来讲

隔水层的固体压缩

是导致地面沉降的主要因素

当然含水层的压缩也会有很大的影响

地面沉降一个典型的例子就是

美国加利福尼亚州的圣金安地区

这是1925年时地面的位置

1955年的时候地面到了这里

到1977年地面到了这个位置

在50年左右的时间里总共沉降了15米多

根据统计我国已有

16个省、市的近50个城市发生了地面沉降

沉降面积达到4.8万多平方公里

年均直接经济损失在1亿元以上

这是我国华北平原地面沉降的情况

可以看出地面沉降与地下水位的下降

有明显的相关性

这个是上海地区1980年到1995年期间

不同城区平均累计地面沉降量

非常有意思的是可以看出从中心城区

到郊区再到郊县沉降量逐渐的减少

为什么呢

相信大家都会知道答案

地面沉降会引起一系列的工程问题

比如建筑物的倾斜、开裂

还有地裂缝等灾害

大规模的地面沉降会造成城市排水系统的失效

从而引起城市内涝的灾害

而沿海地区的地面沉降还会导致海水的入侵

地面沉降一般是由于

过度开采地下水资源而引起的

对于地面沉降严重的地区

可以在含水层进行回灌的方式

使地面沉降适当的恢复

比如上海地区

每年就采用人工回灌地下水的方式

来弥补地下水位的下降

但是这种方式只能使地面沉降适当的恢复

要想大量的恢复几乎是不可能的

地面塌陷是松散土层中

产生的突发性断裂、陷落的一种灾害现象

这种现象大部分是由于

人为局部改变地下水位而引起的

由于水位短时间内大幅度下降

水力坡度大

增加了地下水的潜蚀能力

对地层进行冲蚀、掏空

形成地下洞穴

一旦洞穴顶部失去平衡

便会突然发生这种地面塌陷事故

特别是在岩溶区经常会遇到

比如我国岩溶发育的广西

有些地方有时一连出现几个塌陷坑

这个是正在发展的地面塌陷

而这个是已经形成的塌坑

另外由于城市地下工程

比如地铁、深基坑等

开挖过程中由于快速疏干地下水

也会诱发一些地面塌陷事故

这种现象在城市中经常会遇到

地下水在运动过程中

当动水压力超过一定值时

土中的部分颗粒甚至整个土体将发生移动

从而引起土体的变形和破坏

这个过程就是渗透变形

有时又叫做渗透破坏

根据它的形成机制又可以分为

管涌和流土两种方式

管涌是指在渗流作用下

细颗粒沿着土体骨架中的孔道

发生移动而带走的现象

又叫做潜蚀

管涌一般发生在不均匀的砂粒土中

细颗粒物质

被从粗颗粒骨架构成的孔隙中带走

从而导致土体的孔隙

及孔隙度变大

强度变低

甚至破坏

流土是在渗流作用下一定体积的土体

同时发生移动的现象

它一般发生在均质的砂土层或粉土层中

会导致土体强度完全丧失

发生流土时的水力梯度叫做临界水力梯度

可以通过这个公式来计算得到

对于管涌 由于发生的水动力条件一般比较复杂

所以发生它的临界水力梯度

一般是通过实验或者是图表法得到

这个是2003年7月1日

上海轨道交通4号线区间隧道

也就是浦西联络通道

施工过程中发生的渗水

从而产生流土破坏

导致大量的流沙涌入

引起地面大幅度沉降

并使得一栋八层楼的房屋发生倾斜

另外我国长江中下游的平原冲积地层

在地质剖面上一般为上面是粘性土

往下是粉砂、细砂等

砂层间也有粘性土的夹层

再往下是砂粒及卵石等强透水层

并与河水相通

在汛期高水位的时候

由于水流经过强透水层时

它的压力损失很小

所以河流大堤在数百米范围内的粘土层下面

承受着很大的水压力

如果这股水压力冲破上面的粘土层

下面的粉砂、细砂就会随水流出

从而发生管涌

根据分析 在1998年发生长江洪水险情中

以渗流险情最为普遍

沿着长江有6000多处险情

其中400多处属于渗流险情

而其中管涌又被视为险中之险

当基坑下覆有承压含水层时

如果开挖基坑所留的底板

经受不住承压水头的压力作用

那它被承压水顶裂或冲毁

这种现象就是基坑突涌

随着现在城市建设中的基坑开挖深度越来越深

基坑突涌也时有发生

工程中通常对承压含水层进行预先排水

以降低承压水的水头压力方式来避免这种灾害

好 这节课我们学习了

由于地下水环境改变而引起的

一些常见的工程地质问题

通过这节课的学习

同学们要了解它们所产生的机理和危害

重点掌握地面沉降及渗透破坏的机理和危害

Geology and Engineering Geology课程列表:

0 Introduction

-0.1 Human Engineering Activities and the Geological Environment

--Chapter 0.1 Human Engineering Activities and the Geological Environment

-0.2 Tasks for Engineering Geology

--Chapter 0.2 Tasks for Engineering Geology

-0 Quiz--Homework

1 The Earth and the Crust

-1.1 Formations and Evolution of the Earth

--Chapter 2.1 Formations and Evolution of the Earth

-1.2 Basic Attributes of the Earth

--Chapter 1.2 Basic Attributes of the Earth

-1.3 Construction of the Geo-sphere and the Geological Processes

--Chapter 1.3 Construction of the Geo-sphere and the Geological Processes

-1 Quiz--Homework

2 Endogenic Geological Process

-2.1 Crustal Movement

--Chapter 2.1 Crustal Movement

-2.2 Magmatism

--Chapter 2.2 Magmatism

-2.3 Metamorphism

--Chapter 2.3 Metamorphism

-2.4 Earthquake

--Chapter 2.4 Earthquake

-2 Quiz--Homework

3 Exogenic Geological Process

-3.1 Introduction

--Chapter 3.1 Introduction

-3.2 Weathering Effects

--chapter 3.2.1 Physical Weathering

--chapter 3.2.2 Chemical and Biological Weathering

--chapter 3.2.3 Weathering Products and Influencing Factors of the Weathering Process

-3.2 Weathering Effects--Homework

-3.3 Geological Effects of the Flowing Surface Water

--chapter 3.3.1 Geologic Process of Temporary Torrents

--chapter 3.3.2.1 River Erosion Effects

--chapter 3.3.2.2 River Transport and Sedimentation Effects

-3.3 Geological Effects of the Flowing Surface Water--Homework

-3.4 Geological Effects of Winds

--Chapter 3.4 Geological Effects of Winds

-3.4 Geological Effects of Winds--Homework

-3.5 Geological Effects of Glaciers

--Chapter 3.5 Geological Effects of Glaciers

-3.5 Geological Effects of Glaciers--Homework

-3 Quiz Easy--Homework

-3 Quiz Enhanced--Homework

4 Minerals and Rocks

-4.1 Minerals

--Chapter 4.1.1 Minerals and Their Morphological Characteristics

--4.1.2 Minerals and Rocks-Mineral Characteristics-Physical and Mechanical Prop

--Chapter 4.1.3 Visual Identification of Common Minerals

-4.1 Minerals--Homework

-4.2 Magmatic Rocks

--Chapter 4.2.1 Main Mineral Compositions of Magmatic Rocks

--Chapter 4.2.2 Texture and Structure of Magmatic Rocks

--Chapter 4.2.3 Common Classification and Identification Methods for Magmatic Rocks

--Chapter 4.2.4 Basic Characteristics of Common Magmatic Rocks Ⅰ

--Chapter 4.2.5 Basic Characteristics of Common Magmatic Rocks Ⅱ

-4.2 Magmatic Rocks--Homework

-4.3 Sedimentary Rocks

--Chapter 4.3.1 Material Compositions of Sedimentary Rocks

--Chapter 4.3.2 Texture and Structure of Sedimentary Rocks

--Chapter 4.3.3 Basic Characteristics of Common Sedimentary Rocks

-4.3 Sedimentary Rocks--Homework

-4.4 Metamorphic Rocks

--Chapter 4.4.1 Mineral Composition and their Texture andStructure

--Chapter 4.4.2 Basic Characteristics of Metamorphic Rocks

-4.4 Metamorphic Rocks--Homework

-第4章 Quiz Easy--Homework

-第4章 Quiz Enhanced--Homework

5 The Geologic Times

-5 The Geologic Times

--Chapter 5 The Geologic Times

-5 Quiz--Homework

6 The Geological Structure

-6.1 Horizontal Structure and Dipping Structure

--Chapter 6.1 Horizontal Structure and Dipping Structure

-6.2 Fold Structure

--Chapter 6.2 Fold Structure

-6.3 Fault Structure

--Chapter 6.3.1 Joint

--Chapter 6.3.2 Characteristics and Types of Faults

--Chapter 6.3.3 Fault Identification in the Wild

-6 Quiz Easy--Homework

-6 Quiz Enhanced--Homework

7 Geological Maps

-7.1 ntroduction

--Chapter 7.1.1 Types of Geological Maps

--Chapter 7.1.2 Scale of Geological Maps

-7.2 Presentation of the Geological Maps

--Chapter 7.2.1 Formation Lithology

--Chapter 7.2.2 Geological Structure

--Chapter 7.2.3 Contact Relations Between Stratas

-7.3 Reading and Analysis of the Geological Maps

--Chapter 7.3 Reading and Analysis of the Geological Maps

-7 Quiz Easy--Homework

-7 Quiz Enhanced--Homework

8 Ground Water

-8.1 Basic Conceptuals

--Chapter 8.1 Basic Conceptuals

-8.1 Basic Conceptuals--Homework

-8.2 Reservation and Movements of Ground Water

--Chapter 8.2 Reservation and Movements of Ground Water

-8.2 Reservation and Movements of Ground Water--Homework

-8.3 Movements of the Ground Water

--Chapter 8.3 Movements of the Ground Water

-8.3 Movements of the Ground Water--Homework

-8.4 Ground Water Quality

--Chapter 8.4 Ground Water Quality

-8.4 Ground Water Quality--Homework

-8.5 Ground Water Related Issues on Engineering Geology

--Chapter 8.5 Ground Water Related Issues on Engineering Geology

-8.5 Ground Water Related Issues on Engineering Geoligical Problem--Homework

-8 Quiz Easy--Homework

-8 Quiz Enhanced--Homework

9 Geological Engineering Attributes of Soils

-9.1 Soil Mass

--Chapter 9.1 Soil Mass

-9.1 Soil Mass--Homework

-9.2 Attributes of Soils

--Chapter 9.2.1 Physical Properties of Soil

--Chapter 9.2.2 Water-Physical Properties of Soil

--Chapter 9.2.3 Mechanical Properties of Soil

-9.2 Attributes of Soils--Homework

-9.3 Engineering Classification of Soils

--Chapter 9.3 Engineering Classification of Soils

-9.4 Special Soils and Its Engineering Attributes

--Chapter 9.4.1 Soft Soil and Its Engimeering Attributes

--Chapter 9.4.2 Loess and Its Engineering Attributes

--Chapter 9.4.3 Expansive Soil adn Its Engineering Attributes

-9.4 Special Soils and Its Engineering Attributes--Homework

-9 Quiz Easy--Homework

-9 Quiz Enhanced--Homework

10 Geological Engineering Attributes of Rocks

-10.1 Introduction

--Chapter 10.1 Introduction

--10.1 Introduction--Homework

-10.2 Physical and Water-Physical Properties of Rocks

--Chapter 10.2 Physical and Water-Physical Properties of Rocks

--10.2 Physical and Water-Physical Properties of Rocks--Homework

-10.3 Mechanical Properties of Rocks

--Chapter 10.3.1 Deformation Characteristics

--Chapter 10.3.2 Strength

--10.3 Mechanical Properties of Rocks--Homework

-10.4 Structural Plane and Structural Body of Rock Mass

--Chapter 10.4 Structural Plane and Structural Body of Rock Mass

--10.4 Structural Plane and Structural Body of Rock Mass--Homework

-10.5 Features and Mechanical Properties of the Structural Plane

--Chapter 10.5.1 Properties of Structural Plane

--Chapter 10.5.2 Mechanical Properties of Structural Plane

--10.5 Features and Mechanical Properties of the Structural Plane--Homework

-10.6 Mechanical Properties of Rock Mass

--Chapter 10.6 Mechanical Properties of Rock Mass

--10.6 Mechanical Properties of Rock Mass--Homework

-10.7 Engineering Classification of Rock Mass

--Chapter 10.7.1 Engineering Classification of Rock Mass Ⅰ

--Chapter 10.7.2 Engineering Classification of Rock Mass Ⅱ

--10.7 Engineering Classification of Rock Mass--Homework

-10 Quiz Easy--Homework

-10 Quiz Enhanced--Homework

11 Analysis on the Stability of Slopes

-11.1 Slope Deformation and Destruction

--Chapter 11.1.1 Slope Deformation

--Chapter 11.1.2 Slope Destruction

-11.1 Analysis on the Stability of Slopes--Homework

-11.2 Factors on the Stability of Slopes

--Chapter 11.2 Factors on the Stability of Slopes

-11.3 Analysis on the Stability of Slopes

--Chapter 11.3 Analysis on the Stability of Slopes

-11.3 Analysis on the Stability of Slopes--Homework

-11.4 Structural Analysis Method on Rocky Slope Stability

--Chapter 11.4.1 Stereographic Projection Method Ⅰ

--Chapter 11.4.2 Stereographic Projection Method Ⅱ

-11.5 Measures for Preventing and Controlling the Slope Deformation

--Chapter 11.5 Measures for Preventing and Controlling the Slope Deformation

-11.5 Measures for Preventing and Controlling the Slope Deformation--Homework

-11 Quiz Easy--Homework

-11 Quiz Enhanced--Homework

12 Geological Engineering Analysis on Stability of the Adjacent Rocks of Underg

-12.1 Underground Caverns and the Stress Distribution

--Chapter 12.1 Underground Caverns and the Stress Distribution

-12.1 Underground Caverns and the Stress Distribution--Homework

-12.2 Deformation and Destruction of the Adjacent Rocks

--Chapter 12.2.1 Brittle Adjacent Rock

--Chapter 12.2.2 Plastic Surrounding Rock and Surrounding Rock Stability Sign

-12.3 Factors on Stability of the Adjacent Rocks

--Chapter 12.3 Factors on Stability of the Adjacent Rocks

-12.4 Measures for Preventing Instability of the Adjacent Rocks

--Chapter 12.4 Measures for Preventing Instability of the Adjacent Rocks

-12 Quiz--Homework

13 Analysis on the Stability of the Rock Mass of the Ground Work

-13.1 Dam Foundation of the Water Conservancy Project

--Chapter 13.1.1 Dam Types and Requirements for Engineering Geological Conditions

--Chapter 13.1.2 Deformation Failure Mode and Stability Analysis

-13.2 Common Methods of Foundation Constructions

--Chapter 13.2 Common Methods of Foundation Constructions

-13 Quiz--Homework

14 Geological Engineering Analysis on the Reservoir Construction

-14.1 Reservoir Leakage

--Chapter 14.1 Reservoir Leakage

-14.2 Stability of the Reservoir Bank

--Chapter 14.2 Stability of the Reservoir Bank

-14.3 Reservoir Surrounding Immersions and Sedimentations

--Chapter 14.3 Reservoir Surrounding Immersions and Sedimentations

-14 Quiz--Homework

15 Methods and Technics of Engineering Geological Exploration

-15.1 Introduction

--Chapter 15.1 Introduction

-15.2 Engineering Geological Mapping

--Chapter 15.2.1 Research Content

--Chapter 15.2.2 Structural Plane Statistics

-15.3 Engineering Geological Exploration and Field Experiments

--Chapter 15.3 Engineering Geological Exploration and Field Experiments

-15.4 Instructions on the Geological Compass

--Chapter 15.4 Instructions on the Geological Compass

- Quiz--Homework

Chapter 8.5 Ground Water Related Issues on Engineering Geology笔记与讨论

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