Chapter 6 The main engineering geology

problems in civil engineering

第六章 工程地质问题分析

The main topics of chapter 6:

§6-1 The erosion of river( 河流的侵蚀 )

§6-2 landslide （滑坡） §6-3 Collapse （崩塌） §6-4 mudflow （泥石流） §6-5 Karst and Earth cave （岩溶和土洞） §6-6 The engineering problems in

underground engineering

（地下工程地质问题）

§6-1 The erosion of river( 河流的侵蚀 )

一、 What is river erosion

Which mean the damage to the river bed or river bank,

the river erosion is the most active,vigorous factor to the

change of topography. No river erosion, no complicated

surface.

二、 The river erosion’s type

  Which can be divided into ： side erosive （侧蚀） cut erosion （下蚀）

cut erosion( 下蚀 )

→ means that the moving water and its materials carried

by water have motive power that makes river bed deepe

ned continuously.Cut erosion are usually obvious in upstr

eam of river.

  In bridge engineering, the location of foundation must b

e considered carefully. That is the elevation of bottom sur

face of foundation must will be lower than the erosion ba

se line( 侵蚀基准面 ).

Erosion line 1

Erosion line 2

side erosive

Side erosion are caused by traverse circulation of river. The results of side erosion is that river valley is broaden . The side erosion is obvious in middle or downstream of river.Preventing method: stone cage, changing of river route

Direction of side erosion

Direction of side erosion

Building is not in goodposition

traverse circulation of river

§6-2 landslide （滑坡）

  一 .The definition of landslide （滑坡的定义）

  The soil or rock body slide down along the fixed

sliding surface on the action of gravity.  

The happening of landslide may cause the damage

of building , endanger human life, also cause the artifical

earthquake.

滑坡形态描述

滑坡体Sliding body

滑坡床Sliding bed

滑坡壁 cliff

滑坡面Sliding surface

扇形张裂缝Fan-haped tensive cracks

滑坡舌

鼓胀裂缝Swelling cracks

剪裂缝 Shear cracks

滑坡周界

滑坡台阶

二 .The feature of different part of landslide

Tension cracks

三 .The classification of landslide （滑坡分类） 1.  According to the materials difference of sliding body （按物质组成分类）

■ soil land sliding 土体滑坡 ■ rock land sliding(bedrock landslide) 岩层滑坡 ■special landslides( frozen and thaw 、 collape slide) 特殊滑坡

■ soil land sliding( 土体滑坡 )

cohesive soils landslides （粘土滑坡） loess landslides （黄土滑坡） eluvial soils landslides （残积层滑坡）

Eluvial soil landslide

cohesive soils landslides

■ rock land sliding(bedrock landslide) 岩层滑坡

顺层滑坡 切层滑坡

滑动面

滑动面

movement parallel to planes of eakness and occasionally parallel to slope.

■special landslides( frozen and thaw 、 collape slide)

特殊滑坡

冻融层

Flow: viscous to fluid-like motion of debris.

2  According to the mechanics condition （按滑坡形成的力学条件）

River erosionArtificial cutting

tractive stylePushing style

3 其它分类方法

四、 the developing process of landslide （滑坡的阶段）

step 1 creep deformation stage （蠕动阶段） no fixed sliding plane f

Soft rock

深层蠕动

表层蠕动

step 2 failure stage （破坏阶段）  The penetrating failure plane has formed; the sliding ma

ss slowly or quickly slides along the crack plane ， drunken-l

ike trees; sabre-like trees develops in this stage

step 3 stable stage （稳定阶段）  The sliding mass has been in balanced position drunken trees have become to grow vertically

五、 The mechanics analysis and influencing factor

sinQT

cosQN

Q L

：坡角在平行滑面上的分力在垂直滑面上的分力

滑体的重力

QT

QN

Q

:

:

:

不平衡极限平衡

稳定

1

1

1

T

F

forceslippingtotal

forceslippingantitotalK

土层均匀时：

11

22

dQ

RLdQ

M

MF f

S

rs

六 The analysis influence factors of sliding （滑坡影响因素分析） The influence factor can be considered as the factors which have the contribution to the change of safety factor (K)

① slope appearance （斜坡的几何特征） slop high 坡高 ; slope angle, slope shape

②  rock and soils properties （滑坡体岩土性质） soft rock (shale, sand rock) soil with montmorillonite which is easy to absorb water and expanding.

③ structure （结构面发育程度） the condition of strata plane, joint, fault, (dip angle, dip direction)

④ water （地下水和地表水） to soft rock and soil

⑤  earthquakes （地震） to stimulate the liquefaction( 液化 )

to produce the inertia force to rock or soil body

⑥ artificial factors （人为因素） cutting slope impropely

putting on (piling) (over lapping) soil or building structure

七、 the control (harness) of land slipping

Control principle( 防治原则 )

first prevention ; second harness

The controlling measure （方法） ◆ Discharging water

(surface water and ground water

Landslide ground Water Drainage Works

◆ the supporting structure

Retaining wall Anti-sliding

Deep foundation works would be enforced according to the thrust of the landslide and depth of the sliding surface under such conditions that ordinary piles would not work well enough. In the Kamenose area, these works have been carried out mainly with ferroconcrete piles of 3.5x4.0 meters in diameter and 30x60 meters in length. At present, the works are enforced with larger structures of 6.5 meters in diameter and 100 meters in length.

◆ anchoring bar(pin, rod)

Prestressed Anchors

Anchored Walls for Landslides

◆ unloading and cutting

挡土墙 抗滑桩 锚固工程