高拱坝深基坑渗流控制措施及分析

Seepage Control Measures and Analysis for Deep Foundation Pit of High Arch Dam

在建溪洛渡高拱坝施工过程中,通过对河床深基坑出现涌水的成因分析,采取了减渗帷幕封闭渗水、截排地表水、降水等施工措施,达到控制河床深基坑涌水的目的。通过其效果分析,提出减渗帷幕的厚度和减渗帷幕深入相对隔水层最小深度,应当满足渗流稳定的要求;对强透水性基岩,要确定好幕体的防渗标准,即幕体的渗透系数与岩体渗透系数的比值,其值不大于0.1,渗透流量就明显减少;对先期导水通道灌浆封堵并进行坝基固结灌浆,不仅是坝体地基加固的需要,同时也是施工期加强基坑底部抵抗承压水能力的需要。

During construction of Xiludu High Arch Dam, the cause analysis on water blowing out from deep foundation pit in the riverbed was performed, the eonstruetion measures, such as sealing infiltration water with antiseepage curtain, intercepting and draining the surface water, pumping and draining the water in the pit, were taken in order to control the water blowing out from deep pit. In this paper, thickness of seepage reducing curtain and the minimum depth into relative impermeable layer, which should meet seepage stability requirements, are proposed on the basis of effectiveness analysis. The seepage control criteria for high permeability rock should be carefully established, i. e . the ratio of permeability coefficient of curtain to that of rock mass. When the ratio is not more than 0. 1, the seepage flow would be decreased. The diversion passage should be grouted and blocked at earlier stage, then the consolidation grouting is carried out, not only for reinforcing dam foundation, but for strengthening the capacity of pit base to resist uplift pressure during eonstruetion.