泥石流冻土PPT课件

1、Part threePart three地球表层的塑造过程地球表层的塑造过程环境地质学 Environmental Geology7 7、Mass Wasting ProcessesMass Wasting Processes表层整体再塑表层整体再塑（滑坡、泥石流、溶蚀、塌陷）（滑坡、泥石流、溶蚀、塌陷）第1页/共22页Part threePart three地球表层的塑造过程地球表层的塑造过程环境地质学 Environmental GeologyMass Wasting ProcessesThere is nothing inorganic. The earth is not a mere

2、fragment of dead history, stratum upon stratum like the leaves of a book, to be studied by geologists and antiquaries古玩家 chiefly, but living poetry like the leaves of a tree, which precedes flowers and fruit-not a fossil earth, but a living earth. Henry David Thoreau 第2页/共22页Part threePart three地球表层

3、的塑造过程地球表层的塑造过程环境地质学 Environmental GeologyMass Wasting Processes A、Flowing sand, landslides, and rock falls are examples of mass wasting, the general term for gravitationally induced downslope movement of debris. B、Mass-wasting processes operate on sloping lands; eventually the debris reaches a strea

4、m or gully where fluvial processes continue the erosional process. 第3页/共22页Part threePart three地球表层的塑造过程地球表层的塑造过程环境地质学 Environmental GeologyMass Wasting Processes第4页/共22页Part threePart three地球表层的塑造过程地球表层的塑造过程环境地质学 Environmental GeologyMass Wasting ProcessesRockfallRockfall occurs where a cliff of be

5、drock is exposed to weathering and pieces of the bedrock are pried loose and fall, bounce, or roll to rest at the base of the cliff. The resulting deposit is called talus崩塌岩堆 (Behre, 1933; Schumm and Chorley, 1966; Rapp, 1976). In an irregularly eroded cliff, talus cones may develop in the gully冲沟 聚

6、集 talus cones form a more continuous blanket of debris referred to as scree 山麓碎石(Jeffreys, 1932; Adrews, 1961). 第5页/共22页Part threePart three地球表层的塑造过程地球表层的塑造过程环境地质学 Environmental GeologyMass Wasting ProcessesRockfallTalus will not rest at an angle greater than the angle of repose. The angle of repose

7、 is measured similarly to dip of sedimentary rocks, i.e., from the horizontal, and is typically about 33-35. Bedrock composition, as well as talus particle size, angularity, and sorting, has some effect on the angle of repose; large angular boulders may rest at up to 40. The angle of repose of open-

8、pit mine waste rock is approximately 38. 第6页/共22页Part threePart three地球表层的塑造过程地球表层的塑造过程环境地质学 Environmental GeologyMass Wasting ProcessesRockfallOne of the worlds most famous talus slopes is the one which formed an impedment障碍 to prospectors开拓者 during the Klondike gold rush of 1898. the snow-covered

9、talus slope, called the Scales, was the only access to Chilkoot Pass and the Yukon River. The pass was guarded by the Canadian Northeast Police, who required every prospector to carry 1 ton of supplies up the slope and into the interior. 第7页/共22页Part threePart three地球表层的塑造过程地球表层的塑造过程环境地质学 Environmen

10、tal GeologyMass Wasting ProcessesOne of the worlds most famous talus slopes is the one which formed an impedment障碍 to prospectors开拓者 during the Klondike gold rush of 1898. the snow-covered talus slope, called the Scales, was the only access to Chilkoot Pass and the Yukon River. The pass was guarded

11、by the Canadian Northeast Police, who required every prospector to carry 1 ton of supplies up the slope and into the interior. 第8页/共22页Part threePart three地球表层的塑造过程地球表层的塑造过程环境地质学 Environmental GeologyMass Wasting ProcessesCreep Creep is the slow, downslope movement of soil, weathered rock, or other

12、surficial debris. Movement is by quasiviscous flow, occurring under shear stresses sufficient to produce permanent deformation, but too small to result in a discrete failure surface such as a landslide. 第9页/共22页Part threePart three地球表层的塑造过程地球表层的塑造过程环境地质学 Environmental GeologyMass Wasting ProcessesCr

13、eep Creep may be caused by numerous phenomena. For example, in terrains subject to frost, rock or soil may get heaved up perpendicular to the slope upon freezing, and returned vertically downward during a thaw. Thus, over time, material on a slope is likely to move downhill. Micro-landslides and ran

14、dom movements such as overturned trees, etc., all contribute to creep. 第10页/共22页Part threePart three地球表层的塑造过程地球表层的塑造过程环境地质学 Environmental GeologyMass Wasting ProcessesLandslidesLandslide is the process whereby a distinct mass of rock or soil moves downslope due to gravity. Landslides, unlike creep,

15、have one or more distinct failure surfaces. Landslide velocities are typically on the order of 1 m/day to perhaps 300 km/hr as in the special case of air-entrapped landslides generated by earthquakes. Shreve (1968) believes that the prehistoric Blackhawk Landslide in California slid at immense speed

16、s on a layer of compressed air that was trapped beneath the debris. The landslide, consisting of 320 million m3, traveled 8 km across a desert floor at an average slope of 2.5. Hsu (1975) challenges the airlubrication空气润滑空气润滑 hypothesis假说假说 in favor of a debris flow mobilized by collision of particl

17、es within a dust-laden cloud. 第11页/共22页Part threePart three地球表层的塑造过程地球表层的塑造过程环境地质学 Environmental GeologyMass Wasting ProcessesLandslides Landslide activity typically increases after prolonged rains, or after the frost leaves the ground in the spring. The novelist Firtsch (1980) describes the ominous

18、 hazard of landslides which weighs heavily on the minds of people who live in the steep slopes of the Swiss Alps: 第12页/共22页Part threePart three地球表层的塑造过程地球表层的塑造过程环境地质学 Environmental GeologyMass Wasting ProcessesLandslides Classification of landslides. For simplicity, landslides can be classified into

19、 two groups: 1) translational, and 2) rotational.第13页/共22页Part threePart three地球表层的塑造过程地球表层的塑造过程环境地质学 Environmental GeologyMass Wasting ProcessesLandslides 第14页/共22页Part threePart three地球表层的塑造过程地球表层的塑造过程环境地质学 Environmental GeologyMass Wasting ProcessesLandslides 淹死 in the ensuing跟着发生 flood. The 1903

20、 landslide disaster at the mining town of Frank, Alberta, was a translational slide which developed along a prominent set of joints which dip into the valley.第15页/共22页Part threePart three地球表层的塑造过程地球表层的塑造过程环境地质学 Environmental GeologyMass Wasting ProcessesLandslides Rotational landslides (“slumps” or

21、“slips”) develop in surficial deposits or weathered rock (fig6.1). They may be natural in origin or induced by man. The failure surface is roughly arcuate弧形 in cross section (spoon-shaped in three dimensions). At some places the occurrence of a landslide at the base of a hill may leave the hillslope

22、 above unsupported, and so another landslide occurs (Crandell, 1951). The chain-reaction type of stair-stepping slope failure up a hill is called progressive failure. 第16页/共22页Part threePart three地球表层的塑造过程地球表层的塑造过程环境地质学 Environmental GeologyMass Wasting ProcessesLandslides 22 Mathematical analysis.

23、Mathematical models of landslide stability are presented in Terzaghi (1950; 1962), Scheidegger (1961). Stout (1969), Jaeger (1972), Schuster and Krizek (1978), and Huang (1983). Most problems involving the stability of slopes are associated with the design and construction of unbraced无支挡 cuts for highways. A very generalized rule-of-thumb i