Abstract: The strengthening work of submerged dike at Hechangzhou left braded channel consists of two parts: rock riprap (with nylon cage) on the dike crest and slope protection by rock blocks. Since there is no related specification or experience in determining the compensation coefficient of engineering quantity and construction technique, field tests were conducted for the construction positioning, the detailed technique of rock riprap (with nylon cage), and the compensation coefficient of engineering quantity. Through the field tests, construction positioning was determined, and according to the test results, the compensation coefficient of engineering quantity of riprap at dam crest and dam abutment is 1.2, the compensation coefficient of engineering quantity at underground dam slope is 1.5. Moreover, the calculation formula of the riprap's and nylon riprap's drift distance were derived, and in association with the field test, the riprap's and nylon riprap's drag coefficient was calculated. The research achievements have been applied to the design and construction of strengthening work of submerged dike at Hechangzhou left braded channel, and achieved expected results.

Key words: Zhenjiang-Yangzhou reach of Yangtze River, Hechangzhou braided channel, submerged dike, construction positioning, deepwater riprap, nylon riprap's drift distance, stone drift distance