1 / 17

SCHEDULE

SCHEDULE. OUTLINE. In Class Exam 2 Landsliding Types Mechanics Sensitivity Probability. MIDTERM 2a. Mean: 14.4 Range: 5-30.5 Class performance is now where previous classes were by finals. MIDTERM 2a. Which is most difficult? 1/4 description 1/4 coverages 1/4 functions 1/4 code.

thorntonr
Download Presentation

SCHEDULE

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. SCHEDULE

  2. OUTLINE In Class Exam 2 Landsliding • Types • Mechanics • Sensitivity • Probability

  3. MIDTERM 2a • Mean: 14.4 • Range: 5-30.5 • Class performance is now where previous classes were by finals

  4. MIDTERM 2a Which is most difficult? 1/4 description 1/4 coverages 1/4 functions 1/4 code

  5. Landslide Type: Deep-Seated Large Gradual Lithologic Control Groundwater Control

  6. Landslide Type: Shallow Rapid Small Rapid Root Control Saturation Control

  7. Landslide Mechanics Factor of Safety: Ratio of Forces FS=resisting/initiating FS<1: landslide FS>1: no landslide

  8. Landslide Mechanics qo is the surcharging weight of the vegetation is the angle of the slope is the friction angle of the soil C is the soil cohesion Cr is the root reinforcement h is the soil thickness z is the saturated thickness gw is the unit weight of water gsis the unit weight of saturated soil

  9. Stability Calculation slope_grid q0_grid z phi_grid gw Cr_grid gs_grid h_grid C_grid FS_grid

  10. Computational Process literature Stand cover dem Soil cover Grids of Slope, Cohesion, friction... FS_grid

  11. Example Using q0=10-40 psf C=0 psf Cr=100-200psf phi=35-40 deg gs=150 pcf gw=72 pcf

  12. Problem 1: Equation usually doesn’t predict cells that slid, but predicts sliding in cells that didn’t. Reasons: • uncertainty in parameters • uncertainty in process Solution: Pseudo probability: • FS is only correlated with landsliding

  13. Problem 2: Parameters are uncertain/variable Solution: • Model uncertainty in each parameter, i.e. Cohesion might be within range (3-10 kPa) 1. Choose a value for each parameter 2. Calculate FS 3. Repeat 4. Calculate fraction of times FS<1

  14. Problem 3: How do you model soil saturation? Solution: • Assume steady state rainfall Qin=Qout q*w*d=P*fa Pc=dc*(qw)/fa where dc is the critical value of z that makes FS=1 z>h :never slides z<0 :always slides

  15. Problem 4: Isn’t this all too complicated to use? Solution: • Map hazard ratings (low/moderate/high)

  16. Problem 5: What are the consequences of management? Solution: • Observe fraction cells that slid with each mgt • Assume similar fraction for future mgt • Map/calculate resulting landsliding

  17. Example If we map the topography as high/mod/low And map management as road/cut/none We can make a 3x3 table of hazard/mgt We can calculate fraction of cells in each zone that have slid We can ‘what if’ on other road & harvest plans

More Related