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为了初拟无压隧洞圆形断面尺寸和泄流量的大小,这里介绍一种简便的估算方法。依据任意断面临界水深算式为: (αQ~2/g)=(ω_k~3)/B_k (1) 对于圆形断面时,式(1)中的(ω_k~3)/B_k值可写为(ω_k~3)/B_k=E10~(-3)d~5,于是式(1)变为: (αQ~2/g)=E10~(-3)d~5 (2)1 式中:α-流速分布不均匀系数,常取α=1.0; Q—泄流量(米~3/秒); g—重力加速度,g=9.81(米/秒~2); ω_k—临长水深时的过水面积(米~2); B_k—将界水深时的水面变度(米); E—随水力参数变化的系数; d—隧洞直径(米)。众所周知,无压隧洞圆形断面最大泄流量Q_(max)时
In order to preliminarily plan the size of the circular cross-section of the unpressurized tunnel and the size of the discharge, a simple method of estimation is presented here. According to the formula of the critical water depth at arbitrary cross section, the value of (ω_k ~ 3) / B_k can be written as (αQ ~ 2 / g) = (ω_k ~ 3) / B_k (1) becomes: (αQ ~ 2 / g) = E10 ~ (-3) d ~ 5 (2) where α - flow velocity distribution of non-uniform coefficient, often take α = 1.0; Q-discharge (m ~ 3 / s); g-acceleration of gravity, g = 9.81 (m / s ~ 2); ω_k- Area (m ~ 2); B_k - surface water depth (m); E - coefficient of variation with hydraulic parameters; d - tunnel diameter (m). It is well known that the maximum discharge of a circular section without pressure tunnel is Q_ (max)