Abstract: It is of practical significance to work on the approaches of blocking breaches and delaying dam-break as floods and debris flow caused by dam-break are detrimental to the country and people ' s life and property. Nonetheless, since dam-break is non-repeatable and harmful in practice, it can only be studied theoretically by getting data from small-scale tests. In this paper, the small-scale test of blocking breaches by throwing heavy objects is performed to evaluate the results under different throwing heights and flow velocities by three throwing modes. The influencing factors and the rule of motion of the objects in the process of falling are analyzed, and the horizontal and vertical differential equations in ideal status are set up. Based on the least square method and error-revised data from small-cale tests, the parameters are obtained by Matlab programming and the location of throwing objects in simulated dam-break is calculated by using similarity criterion. The study provides theoretical basis for blocking breaches.

Key words: block the breaches , least square method  , similarity criterion