Lab 6 Part III_Data Sheet_F2F

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Georgia State University *

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1113L

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Geology

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Apr 3, 2024

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Angle of Repose (Materials provided in class) In this activity you will measure the maximum slope at which grains are stable (angle of repose). You will explore how different properties of the sediment influence slope stability and lead to different slope failures (mass movements). Materials  Pan or tray  Sediment samples: dry sand, damp sand, angular gravel, rounded gravel  protractor  small scoop  container of water Instructions (Read these carefully or you will have to redo your responses!) 1. Slowly pour a stream of dry sand into the center of your pan or tray. Do not pack the sand with your hands. Only pour over the top of the pile using the scoop. Bigger piles create a more accurate angle of repose (you may want to use all of the sand provided). Avoid disturbing your pile and carefully measure the maximum angle, or steepest slope, of the dry sand. This slope is called the angle of repose. Record your answer on the data sheet (1) by turning your protractor upside down and aligning the slope of the pile with the best fit angle line on the protractor (try closing one eye and holding the protractor some distance from the pile). 2. Add a few grains (a pinch) of dry sand to the top of your pile and see how the grains move. Repeat, observing the movement again. Describe the downward movement of the dry sand on the data sheet (2). Note whether the sand grains move individually or in large groups. 3. Put all your dry sand back into its container. Sweep your tray clean (use the garbage cans and paper towels). 4. Repeat the experiment using damp sand. Place a pile of damp sand in the center of your pan or tray. You will probably have to scoop the sand instead of pour it. You can gently pack the pile together, but use only gentle pressure. What is the maximum angle of the damp sand? (3) 5. Add a pinch of the damp sand to the top of the pile and see how the grains move. Repeat, observing the movement again. Describe the downward movement of the damp sand on the data sheet (4). Note whether the grains move individually or in large groups. 6. With the cup, slowly pour water onto the pile of damp sand and observe what happens to the sand pile as the sand becomes saturated. Can the saturated sand maintain its angle of repose? (5). 7. Again, put the wet sand back into its proper container (separate from dry sand) and clean up your tray and any other mess, then answer questions (6) – (9). 8. Slowly pour the rounded gravel into the center of your tray or pan. Make sure your pile is large enough to get the true angle of repose! Carefully measure the angle of repose, without disturbing the pile. Record angle (10). Pour the rounded gravel back into the container. 9. Repeat the experiment using the angular gravel and record the results (11). Answer questions (12 and 13). 10. Put all materials away. Clean up your area. 129

Angle of Repose (Materials provided in class) DATA SHEET Name: ___arely vicente___________________________ Group Members: ______________________________ ______________________________ ______________________________ ______________________________ 1. Dry sand angle of repose is _____20_______ degrees. 2. Dry sand movement: Its dropping individually 3. Damp sand angle of repose is ____40_______ degrees. 4. Damp sand movement: Moves in a group 5. Can the saturated sand maintain a steep angle of repose? yes 6. Which sediment condition – dry or damp – permits steeper slope angles? _______ 7. Which sediment condition – dry or damp – lends itself to the most dramatic, quickest, and therefore most dangerous style of slope failure? __ rockslide____________ 8 Explain why you think the damp sand can maintain a higher angle of repose than the dry sand. Dry sand is quicker to slide down, versus damp sand which Due to the water holds longer and can maintain a higher angle of repose. 9. Suppose a house is built on a slope made of sediment. The slope is slightly greater than the angle of repose. Is this house at risk from mass movement? Yes, the house is at risk from mass movement if it is built on a slope that is slightly greater than the angle of repose. 10 . Rounded gravel angle of repose is ___30____ degrees. 11 Angular gravel angle of repose is ___35_____

Angle of Repose (Materials provided in class) . degrees. 12 . Compare the angle of repose for the dry sand and the dry gravel. What impact does grain size have on the angle of repose? Grain size depending on it being dry or damp determines whether there is a stronger hold. Dry sand would be the easiest to collapse because it falls grain by grain. 13 . Compare the angle of repose for the rounded gravel and the angular gravel. What impact does grain shape have on the angle of repose? As the roundness of materials increases, the angle of repose decreases since there is less friction between the grains. Use the results of your experiments and the graphs below to answer the following questions. Source of data: City of Seattle, 1999. Seattle Landslide Study http://www.seattle.gov/DPD/Landslide/Study/default.asp accessed August, 2005. 14. In the Seattle area, which four months experience the greatest amount of rainfall? November , December, January, february

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