不透水地基上堤坝上游坡的附加渗径

Additional length of seepage path of upstream slope of dams and levees on impervious strata

根据努美罗夫的理论解,附加渗径ΔL与上游水深H成正比,与单宽流量与渗透系数的比值q/k成反比。按该理论解的浸润线方程,应用数值积分法求出比例系数α和β,并提出了有足够精度的拟合式。边坡有压流的附加渗径ΔL仅与透水层厚度T成正比,而和H、q/k无关,ΔL=C0T。根据计算结果,α=C0。对于ΔL反比于q/k,文中作了分析和解释。该计算方法还可推广应用于上游坡下有一定厚度覆盖层的附加渗径计算,并且对附加渗径的各计算式作了比较和分析,并以实例说明了如何应用附加渗径计算堤坝的渗流。

According to Numerov＇s theoretical solution, the additional length of seepage path of upstream slope of dams and levees on impervious strata is direct propotional to the upstream water depth H, and inverse propotional to the ratio of the seepage quantity of unit width to the permeability coefficient q/k. On the basis of the equation of phreatic line in Numerov＇s theoretical solution, coefficients α and β are calculated by Simpson＇s numerical integration method. For confined flow, the corresponding additional length of slope is directly propotional to the thickness T of permeable strata only; and not relate to H and q/k, i.e. △L -- CoT. In accordence with the calculating results, α = C0 . Why the additional length △L is inversely propotional to q/k, the reason is explained. The method of calculating AL has extended to the condition that under the slope an overburden is located. All the formulae of additional length △L are analysed and compared each other. Finally, an example is given to relate the process of calculating the seepage flow of dams with the additional length △L.