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本文指出土坝上游用铺盖防渗是一种符合多、快、好、省的方法.本文主要研究了下列问题:1.介绍基础土壤的管涌可能性及其所谓抗渗强度的概念,并讨论它们对设计铺盖长度的影响;2.讨论了经济安全的铺盖长度、厚度及渗流量计算;3.确定斜墙后浸润线的位置及铺盖下等势线的分布.选择最短铺盖长度,主要取决于下面两个条件:1.铺盖下坝基渗透坡降 j_0小于或等于坝基土壤的尤许坡降(以不发生渗透变形为原则);2.单宽渗流量小于或等于允许设计渗流量 (以蓄水水能利用为原则).根据巴夫洛夫斯基的分段法原理及上述原则得到下列计算公式.铺盖长度计算:表示第一个条件的计算公式为(15)式;表示第二个条件的为(14)式.给定了铺盖长度后,渗流量按(18)式计算.铺盖的厚度按(25)式计算.从72个试验资料证实本文所建议的计算公式在目前说来,较其他国内外学者的公式精度高.从理论和试验研究结果可得铺盖防渗的几点重要的概念:1.铺盖的透水性愈小(k_0/k_n≥5000)防渗的效用也就愈大,反之防渗的效用则很小.2.不管铺盖的透水性强与弱都存在着“有效铺盖长度”的概念,即铺盖的长度如大于有效铺盖长度时,它的防渗作用不显著.“有效铺盖长度”是随铺盖的透水性增加而减小.3.想用强透水性的铺盖防渗(不管铺盖怎样长),要达到弱透水性铺盖那样的效果是不可能的(指渗流量的大小而言),因此,铺盖的透水性愈小愈好,k_0/k_n 值最好至少大于2000.
This paper points out that the seepage control in the upstream of earth dam is a kind of method that meets the needs of more, faster, better and more economical.This paper mainly studied the following problems: 1. Introduced the possibility of pipe infiltration and its so-called impervious strength Their impact on the design cover length; 2. The economical and safe bedding length, thickness and seepage flow calculation are discussed; 3. The location of the subsidence line and the distribution of the equipotential lines under the cover wall are determined. The choice of the shortest cover length mainly depends on Under the following two conditions: 1. Under the cover dam foundation seepage gradient j_0 less than or equal to the dam foundation soil slope (according to the principle of infiltration and deformation does not occur); 2 single-width seepage flow is less than or equal to allow design seepage flow According to the principle of piecewise method of Pavlovsky and the above principle, the following calculation formula is obtained: The calculation of the cover length: The formula for expressing the first condition is (15); the second Given the length of the bedding, seepage flow is calculated by Equation (18), and the thickness of the bedding is calculated as (25). From the 72 experimental data, it is verified that the formula proposed in this paper is Come, more than other domestic and foreign scholars fine formula The degree of high.From the theoretical and experimental research results can be seepage control seepage a few important concepts: 1 cover the water permeability of the smaller (k_0 / k_n≥5000) seepage control effect is greater, while the effectiveness of seepage control It is very small.2.It has the concept of “effective cover length” regardless of the strong and weak water permeability of the coverings, that is, the impervious effect is not significant when the cover length is greater than the effective cover length. “Effective cover length” is With the increase of water permeability of the cover decreases .3 want to use a strong permeability of the cover impermeable (no matter how long the cover), to achieve the effect of weak permeability of the cover is not possible (referring to the size of the seepage flow) Therefore, the smaller the water permeability of the cover, the better, k_0 / k_n value is preferably at least greater than 2000.