In this thesis , first , reasons and factors for the stability of loose rock dams were summarized according to the field surveys and certain expert ' s experiences . then , researches on block stability problems were reviewed , and according to the relationship between grain size and incipient velocity , it is found that the block weight is in direct proportion to 6 - 9 power of incipient velocity , and 50 % increase of the velocity will result in about 40 times change of the block weight . after that , experiments were conducted in a flume , focusing on the relationship between incipient velocity and some main factors including block weight , water depth over the dam , cross - section size , block material and river bed material
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