帷幕灌浆技术在既有土坝可溶岩坝基中的应用

APPLICATION OF CURTAIN GROUTING TO THE SOLUBLE ROCK FOUNDATION OF EXISTING SOIL DAM OF WANGHUATING RESERVOIR

针对河南省方城县望花亭水库坝基水文地质与工程地质条件,对坝基渗流进行了分析,指出在桩号0+165～0+430坝段的大理岩总出露宽度为265 m,第5,7层大理岩仅占坝址区大理岩总宽度38%,但渗漏量却占坝基总渗漏量的69.7%,由此形成落水洞、大面积沼泽地、管涌和接触冲刷等隐患。分别对坝基大理岩进行封闭式帷幕和悬挂式帷幕灌浆处理。按照初步设计阶段灌浆设计要求,拟采用常规的一次灌浆法或“孔口封闭自上而下分段灌浆法”,但灌浆试验表明在钻孔中止塞困难,绕塞返浆严重,造成土坝吃浆量很大,坝顶冒浆十分严重,对坝基进行灌浆非常困难。经反复试验,摸索出“孔口及坝体封闭、基岩内自上而下分段孔内循环灌浆”的灌浆工艺和灌浆方法。灌浆试验及灌浆施工结果表明,采用新的灌浆工艺后,虽然也存在不少施工难题,但灌浆效果很好。总结了这种新的施工方法的产生、试验情况、施工工艺、灌浆效果检查等,以便供同类工程参考。

The seepage of dam foundation of Wanghuating reservoir is analyzed according to the hydrogeological and engineering conditions. It is pointed out that the total width of the marble outcrop under the dam block between stake 0+165-0+430 is 265 m. The fifth and seventh layers of the marbles are 38% of the total width of dam site, but its seepage amount accounts for 69.7% of the total seepage amount. Thus there are hidden troubles of sinkholes, swamps of big area, piping of the highly permeable layer and contact erosion. Therefore, the treatments of curtain grouting and hole-top enclosure curtain grouting to the dam foundation are considered. According to the requirement for the preliminary design phase, the method of sectioned grouting from top to bottom with hole-top enclosure is adopted. But the grouting test results show that the method is difficult to carry out and the grouting effect is unsatisfying. Problems such as trouble watertight plug, serious grout-recycling in the hole, considerable emission of slurry to the dam body and out the top of dam occur. By many tests, the sectioned grouting from top to bottom in bedrock with slurry cycling within hole and enclosure at dam body and hole top is employed. The results of testing and practical grouting show that the grouting effects is excellent in spite of some difficulties in execution. The development of this new method, testing, construction techniques and quality inspection are introduced.