Chapte r 6 The main engineering geology problems in civil e ngineering 第第第 第第第第第第第第
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 ).
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
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
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
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
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.