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| Grain erosion induced by the Wenchuan Earthquake and its control |
| Wang Zhaoyin,Liu Dandan,Shi Wenjing |
| Tsinghua University,State Key Laboratory of Hydroscience and Engineering,100084,Beijing,China |
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Abstract Grain erosion is defined as the phenomenon of detachment of grains from bared rocks under the action of insolation,temperature changes,and freezing and thawing,movement down a steep slope triggered by wind and shaking,and cumulates at the toe of the mountain forming a deposit fan.The Wenchuan Earthquake,occurred in Sichuan on May 12,2008,caused numerous rockfalls,avalanches and landslides,which damaged vegetation and left scars on high slopes.Consequently grain erosion occurred throughout the earthquake area.Grain erosion caused flying stones injuring humans,and resulted in numerous slope debris flows.The laws of grain erosion and control measures are studied by field investigations and field experiments.It is found that the most serious grain erosion occurred in spring and early summer because of intensive insolation of sunshine and temperature change. Wind is the triggering agent for grain falling from the slope.Experimental results show that the amount of grains falling from the slope per time is proportional to the fourth power of wind speed and the size of grains increases linearly with the wind speed.The experiments also demonstrate that grain erosion may be controlled with some moss species.Moss spores were mixed with clay suspension and splashed on the bared rock.A layer of green moss appeared on the rock and stopped the grain erosion,because the moss layer cut off the sunshine and mitigates temperature difference.Many huge bared mountains suffering grain erosion in the earthquake area can be quickly greened by using helicopter to spray moss spores and clay suspension.
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Received: 03 September 2009
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