Model Test On Cushion Pool With Lining Slope But No Bottom Protection In Altash Project

The remarkable characteristics of key hydro-junction are narrow valley,high water head,large discharge per unit width.The problem of energy dissipation is critical,and it is also the problem that needs to be solved in practice.With the development of construction of high arch dam such as Ertan,a new type of flood discharge and energy dissipation b y surface-bottom ski-drop flow combined with plunge pool behind the dams is exploited and it can solve this difficult problem well.But demerits are existing more or less,for example fussy construction and high quality demands.So if it has good engineering geological environment and extra depth of water,the cushion pool with lining slop but without buttom protection can be considered adopting.In order to demonstrate its feasibility,this paper conducts a systematic study of this cushion pool based on Altash project.The details are as follows:(1)First,combined with flat bottom water cushion pond,the hydraulic characteristics in the water cushion pond are summarized and the time-averaged pressure,fluctuating pressure,uplift force and their distribution in plunge pool are studied through the model test.Then the possible damage range and maximum anchorage force can be predicted;(2)Based on the characteristic distribbutions of uplift force,this paper makes new proposals for the shape of plunge pool.Tests for uplift force were conducted with lowering its bottom elevation,adding tail-weir and the combination of the two.(3)With granular materials for simulating terrain environment,the test results of the shape of the river bed downstream on different working conditions respectively.It can be used to optimize the shape of flip bucket of spillway tunnel through the analysis of the flow pattern and scouring patterns.And to analyze the characteristics of tipsy bucket,curved surface bucket and tongue-type bucket,this paper makes a useful conclusion about the erosion adjustment law.(4)The RNG k-ε two-equational model for 3-D turbulent flow was applied to numerically simulate flood discharging and energy dissipation based on the original scheme and the 3rd optimization scheme,then the simulation data was compared with the experimental data.There was some difference between simulation and experiment,but it can be used as reference for model test,and it can help to understand the complex flow pattern and energy dissipation mechanism of plunge pool.Then using the result,the erosion can be numerically simulated,and the result is similar to the data of model test.