摘要
三峡二期围堰的防渗墙主要建在上、下游横向围堰堰体内，防渗墙最大高度约７４ｍ，成槽总面积达７．９５万ｍ２，墙厚１．０～１．１ｍ。其施工的主要难点是：工程量大，施工强度高，要求在一个枯水期内（６个月）完成主要部位的工程量，月最高成墙面积１．３８万ｍ２；防渗墙穿过的地层结构复杂，河床段堰体高度的２／３为水下抛填的风化砂和砂卵石，属强透水层，造孔成槽时漏浆严重，孔壁极不稳定，易坍孔；覆盖层中分布有形状极不规则的块石和块球体，钻进时容易导致斜孔；河床深槽部位的基岩系陡直立坡段，钻进时易溜钻、跑钻，嵌岩成槽困难。工程技术人员根据不同的地层特点，探索总结出了一套防渗墙成槽的施工方法，即“钻凿”法，“两钻一抓”法，“两钻三抓（铣）”法，“铣、砸、爆”法，“抓、铣、钻、砸、爆”综合法，“液压双反弧接头槽”法等，工程完工后，由长江委三峡工程建设监理部对其进行了质量鉴定，结果表明：合格率为１００％，优良率达到８０％以上。
Impervious core walls of the TGP Stage Ⅱ cofferdams were mainly constructed in the upstream and downstream transverse cofferdams, with their maximum wall height of about 74 m, total trenching area of 79 500 m 2, wall thickness of 1.0～1.1 m. Difficult points of construction of the impervious core wall are as follows: ① The work quantity of the core walls is large, construction intensity is very high and the work of main portion needs to be completed within one low flow period (6 months) with a monthly maximum area of building wall being 13 800 m 2;② The structure of strata to be passed through by core walls is complicated, cofferdam materials of 2/3 cofferdam height in the river bed section are weathered sand and sand gravel dumped under water and belong to strongly pervious layer, so that paste leakage was serious when boring and trenching, side walls of bores were not stable and easy to collapse;③ There are unregular block stones and boulders in overburden, so inclined bore might arise during boring operation;④ In the deep river channel section, foundation rock is in a state of steep slope, so it was difficult to trench in foundation rock for embedding core wall due to sliding and deviating of drill bit. Technical personnel investigated a set of construction methods for building core wall trench such as methods of “drilling～chiseling”, “two drillings and one grabbing”,“two drillings and three grabbings(cuttings)”,“cutting hammerblowing blsating”,“integrating of grabbing cutting drilling hammerblowing blasting”and “double arc joint trench by hydraulic machinery”.After completion, the quality of the impervious core walls was assessed by the construction supervision department of Changjiang Water Resources Commission, and the assessment results show that the ratio of impervious core walls up to standard is 100% and the excellent core walls are 80%.
出处
《人民长江》
北大核心
1999年第5期1-3,共3页
Yangtze River
关键词
混凝土
防渗墙
三工程
围堰防渗
帷幕灌浆
Leakproof of cofferdam Concrete cut off wall Regional engineering geology Curtain grouting Project quality Sanxia Multipurpose Project
