工程地质学-岩质边坡稳定分析课件.ppt

1、The Vaiont Landslide in the Dolomites(The Dolomites are a mountain range in Northern Italy)This map shows the scale of the landslide,which slopped the contents of the reservoir over the dam and killed more than 2000 people in Longarone and the adjoining communities This is a view of the landslide fr

2、om upstream.地质 Rockslide at Yosemite National Park,California kills one,injures 47.不稳定边坡的防治措施不稳定边坡的防治措施平整坡面以免坑洼地积水平整坡面以免坑洼地积水外围挖沟槽以阻断地表水流向坡体外围挖沟槽以阻断地表水流向坡体坡体上修筑排水沟坡体上修筑排水沟防地表防地表水入渗水入渗Surface Drainage on a slope on the road into Runswick Bay,a coastal village in Yorkshire,EnglandIn the Henllys landsl

3、ide in South Wales trench drains have been dug in front of the landslip,so that it will slide over the top,and be drained from underneath.Drains are installed in near-horizontal boreholes under a tip of urban refuse which was sliding downhill near Ancona,Italy.This diagram shows a coastal landslide

4、with several systems of drainage Drains are installed in near-horizontal boreholes from shafts in a coastal landslide at Herne Bay,Kent.Drains are installed in a variety of ways to stabilize slopes.Gros Ventre Landslide Wyoming Traits:largest historic slide in U.S.June 23rd,1925.40 million metric to

5、ns.followed heavy rains and snow melt.formed 40-60 meter deep lake.beds dipping parallel to slope.ranch destroyed by rising lake.1927 break out flood.View from Grand Teton mountains across valley to E to Gros Ventre Range and large flake scar on mountain side.Upper part of slide showing where basal

6、slip surface at bottom of Tensleep sandstone(on top of Amsden Formation clay beds)is exposed.Note intact sliver with trees half way down bare scarp.View from interior of hummocky toe to other side of valley where Tensleep sandstone rode up and against in place Chugwater red clastics.View from head s

7、carp scar with snow to translational slide block in middle to hummocky toe at base.Creep is the unnoticed slow movement of unconsolidated soils downslope.It is commonly seen as curved tree trunks as in the above phote.Important to look for when buying real estate but not life-threatening.An earth fl

8、ow near Interstate Highway 70,Ellsworth County.The head is the upslope portion of the landslide.The scarp,the steeply inclined failure surface with exposed soil and rock,marks the top of a landslide.The toe is the downslope portion of the landslide.A mound of soil called a lobe marks the toe of the

9、landslide.RECOGNITION OF AREAS OF POTENTIAL SLOPE FAILURE(25)I Main Topics A Motivation B Signs of slope instability http:/anaheim- I Motivation A Most landslides(or potential slides)can be recognized or predicted if the proper investigations are performed in advance.B Except for small slides,slides

10、 typically cost far less to prevent than to fix(An ounce of revention is worth a pond of cure.).C Massive slides may cost many times the cost of the desired facility;they should be avoided.III Signs of past slope instability(focus on topography and hydrology)A Review of maps(Figs.4.5,3.9 in SR 176)B

11、 Review of aerial photos&remote sensing imagery in SR 176 1 Hummocky topography http:/www.kgs.ukans.edu/Publications/pic13/pic13_2.html a Oblique aerial photos:Figs.2.19,2,22,2.23,2.28,2.33 b Stereophotos:Figs.3.14,3.26,3.31 2 Arcuate fractures and old scarps or scars http:/anaheim- a Oblique aerial

12、 photos:Figs.2.19,3.40,b Stereophotos:Figs.3.5,3.7,3.14,3.19,3.20,3.24 3 Areas of anomalous vegetation(seasonal photos useful)a Oblique aerial photos:Plate 3.3 a Stereophotos:Plates 3.1,3.2 4 Areas of seepage:Vertical infrared imagery:Fig.3.35 5 Sand flows and talus(Figs.3.25,3.30)C Features to exam

13、ine in field reconnaissance 1 Ground cracks(Fig 4.2 in SR 176)2 Closed hillside depressions 3 Phreatophytes and seeps 4 Patched or hummocky roads 5 Tilted walls,trees,and fencesSurface signs of soil creep.Leaning power and telephone pole,fences and gravestones,and trees bending first downslope befor

14、e growing straight up may provide evide of soil creep.The mechanics of soil creep.Individual soil or rock particles are raised at right angles to the slope by swelling or expansion and then settle vertically downward during compaction or contraction.The net result is slow downslope creep.EARTHFLOW:S

15、oil and other surface materials move downslope as a viscous flow.SLUMP:a type of rotational slide.BLOCK SLIDE:The sliding mass is moving along a planar surface.Jipazi Landslide,Sanxia Gorges,Yangtze RiverOne of landslide in the Loess PlateauDebris Flow in Jiangjiaguo,Yunnan ProvinceTake samples from debris flow in JiangjiaguoFront view of Xintan LandslideBird view of Xintan Landslide