Experimental studies on intake headloss of a blasted lake tap

27th IAHR Symposium on Hydraulic Machinery and Systems

Yang, James^1,2 ; Billstein, Mats^1 ; Engström, Fredrik^3 ; Strand, Rikard^3

Vattenfall Research and Development, Ålvkarleby

814 26, Sweden^1

Hydraulic Engineering, Royal Institute of Technology, Stockholm

100 44, Sweden^2

Vattenfall Vattenkraft AB, Luleå

971 77, Sweden^3

关键词: Explosive charges;    Free-surface vortices;    Narrow channel;    Physical model;    Submerged tunnels;    Vertical shaft;   

Others  :  https://iopscience.iop.org/article/10.1088/1755-1315/22/4/042011/pdf
DOI  :  10.1088/1755-1315/22/4/042011

来源: IOP

【 摘 要 】

In existing reservoirs, construction of an intake is sometimes achieved by so-called lake tapping, a submerged tunnel piercing by blasting out the rock plug at the intake. The blasting process involves phases of rock, water, air and gas released from the explosive charge; the resulting entrance profile often differs from design assumptions. The intake headloss is a factor of concern for power generation. For a vertical intake formed by lake tapping, experiments have been carried out in a 1:30 physical model to examine the effect of entrance shapes on intake headlosses. The purpose is that, if there is potential to reduce the headlosses, the originally blasted intake shape would be modified. In the model, five alternative shapes are evaluated. The test results show that to enlarge the vertical shaft area is the most effective way to reduce the intake headloss; to further blast out a narrow channel upstream does not give much effect. Bearing in mind the risk of free-surface vortex at the intake, the influence of the intake modifications on vortex is also checked.