深厚覆盖层中弱透水层对渗流影响的试验研究

摘要

我国西南、西北地区常存在强弱互层的深厚覆盖层坝基,弱透水层在深厚覆盖层坝基中对渗流影响较大,其影响规律需要深入研究.试验中将弱透水层设置在坝基的不同位置,变化垂直防渗墙的深度.试验结果表明,弱透水层处在中间位置处,其与防渗墙形成半封闭式联合防渗体系能有效降低坝基渗流量与出逸坡降;上江坝工程实例中,经半封闭式联合防渗体系降低后的渗流量及出逸坡降皆在允许范围内;从理论层面上考虑,该弱透水层若能加以利用,可大大减小防渗墙深度.此外,研究还发现,当防渗墙位置越深,其与防渗墙形成的半封闭式防渗体系越能有效减小渗流量及出逸坡降.研究成果能为类似工程提供一定的理论参考及建议,从而降低工程造价.%The deep overburden dam foundation of strong and weak layers is always met in Southwest and Northwest China.Weak aquifer in deep overburden dam foundation has a great influence on seepage.The influence law needs to be explored in depth.Weak aquifer is set at different positions underneath dam foundation in this test.The depth of vertical cuttoff wall is variable.The result of this test shows that when weak aquifer at the middle of dam foundation,cuttoff wall can form semi-closed combined seepage prevention system,which can effectively decrease seepage discharge of dam foundation and exit gradient.When the semi-closed combined seepage prevention system is adopted in Shangjiang dam,seepage discharge and exit gradient meet allowable requirements.If weak aquife can be utilized,the depth of cuttoff wall can be greatly reduced.This study also finds that when the position of cuttoff wall is deeper,the seepage control of semi-closed combined seepage prevention system can effectively reduce seepage discharge and exit gradient.The results can provide some theoretical reference and suggestions for similar projects,so as to reduce the project cost.