The Investigation of Effective Factors in the Removal of Bentonite Jelly from the Joints of Cut-off Wall Panels

In the construction process of a plastic concrete cut-off wall, concreting is usually performed using the termie pipe method. In this method, concreting is performed from the lowest point in the excavated trench (containing the slurry) using a funnel and the pipe connected to it. The concrete poured in the funnel gradually settles in the panel through the termie pipe which is beneath the slurry and the end of the pipe has always been in the concrete. Because of its unit weight which is less than that of the concrete, the slurry goes up and the height of its column reduces. As the construction continues the length of the termie pipe is cut down so that the remaining operation is carried out more easily. In this process there are three types of flows to be considered: concrete flow in the termie pipe, concrete flow in the panel and slurry flow in the panel. Using the fundamentals of hydraulics, this paper tries to study the interactions among these fluids. It also examines the influential factors in removing the bentonite jelly in order to provide the plastic concrete with homogeneity and consistency (slump 22-16 cm) in primary and secondary panels of cut – off wall as a most reliable water tightening system in most dam foundations.