The Experiment Study On The Scouring Characteristics Of Cohesive Undisturbed Soil

In this paper, through summarizing the domestic and foreign research results on cohesive soil in the last 100 years ,and taking lessons on the similar researches ,the author has specially designed a testing device for the cohesive undisturbed soil experiment, which has been used for starting mechanism of cohesive undisturbed soil experiment, with the 43 groups of cohesive undisturbed soil samples coming from Jiangsu central canal, tide channel, Xinyi river, Changxin island in Yangtse River. The author presented the effect factors of cohesive undisturbed soil and built the relationship between the critical tractive condition and the physical mechanical index of soil through experiment research. The unique experimental study applied in the Sutong Yangtse River highway bridge and the Taizhou diversion channel project has been proved efficient.The main researches results are listed as follow:(l)The critical tractive shear stress formula was concluded by analyzing the starting mechanism of cohesive undisturbed soil and building the starting modelWhen the gravity is neglected, it becomes(2)By demonstrating the hydraulic characteristics of rectangle flume, and comparing the experimental results of closed-pressure flume and opened-non-pressure, the author believed that the experimental results by rectangle closed-pressure flume can substitute for the opened-non-pressure flume. The results provide a method for future research.(3)By summarizing the starting research of the cohesive undisturbed soil in different channel, some result has been found that because the soil form condition and reason is different in different channel, the critical starting condition of cohesive undisturbed soil is different, although they have similar physical mechanical characteristics. In a same river, there are some obvious rules between critical starting condition and physical mechanical index. To silt clay, the critical starting condition increases with the decreasing of shear strength. While it decreases with the increasing of water content. The critical starting condition of silty clay has a non-linear relationship with shear strength and water content. The critical starting condition of clay increases with the increasing of shear strength and water content(4)The method used in this paper is successfully applied in the Sutong Yangtse River highway bridge and the Taizhou diversion channel project. It provides reference for design of mobile-bed model.