深厚覆盖层坝基防渗墙深度研究

在西部山区深厚覆盖层上建设高坝，坝基防渗是关系到工程成败的关键。塑性混凝土防渗墙加灌浆帷幕防渗体系已经在多座大坝工程中应用，实践证明是成功的。由于坝基防渗墙建设控制工期，并且工期较长，在满足防渗要求的条件下应尽量减少工程量。研究防渗墙的合理深度，能够在一定程度上减少工程量，优化施工工期。基于改进阻力系数法求得防渗墙底部坡降随防渗墙深度变化的解析解，并且通过数值模拟方法详细研究了深覆盖层内防渗墙深度变化时防渗墙底部水头、坡降的变化规律。认为深厚覆盖层内设置防渗墙的深度并非越深越好，而是存在一个最优深度。最优深度的取值取决于覆盖层的深度。一般情况下，相对深度比（防渗墙最优深度与覆盖层深度之比）在0.7左右为防渗的最优取值。

A study of anti-seepage wall depth in thick overburden dam base

Anti-seepage in thick overburden dam base is one of the key problems for dam construction and dam safty. It has been used in several dam projects that the plastic concrete anti-seepage wall plus grouting curtain regarded as the waterproof system. The anti-seepage wall construction impropriated the time limit for such projects; so, it should be shortened as its possible. To study the optimum depth of anti-seepage wall is needed. An analytical solution for grading downwards the anti-seepage wall is deduced based on the drag index methods. And it is studied in detail that the law of grading downwards the anti-seepage wall varied with its depth increase. The results show that the depth of anti-seepage wall in limited thick overburden is not the deeper the better. By contraries, it was sure that there was an optimal depth, in which grading downwards the anti-seepage wall is the least. The value of the optimal depth is related with the depth of the overburden. In general, when the relative depth ratio between the depth of anti-seepage wall and overburden is about 0.7; grading downwards the anti-seepage wall is at the least.