二元结构地层基坑深井降水工法.pdf

  随着城市高层建筑的发展，深基坑工程越来越多。由于深基坑设计和施工受到地质、水文、环境、季节、荷载等诸多因素的影响，在二元结构地层条件下，深基坑的主要矛盾是治理地下水的问题，特别是在地下水位高、承压含水层厚度大、水量丰富的水文地质条件下，如果对地下水治理不当，在开挖过程中极易产生流砂和管涌，影响场区周围建筑物和市政公用设施的安全。很明显，一般的降水技术很难达到要求。中建三局建筑技术研究设计院经过几个工程的实践、探索，逐步形成了一整套深井降水新技术。在地质岩性构成具有明显的二元结构沉积韵律，承压水位距地表仅l~2米，层厚达30米的武汉国际贸易大厦采用了此项新技术获得成功。并获中建三局1995年度科技进步一等奖，同时作为武汉国贸主体综合施工技术的一部分获1995年中建总公司科技进步一等奖。
1  工法原理
    深井降水是在基坑开挖前，根据基坑面积大小、涌水量等因素，预先在坑内、坑外或坑内外结合，布设一定数量的管井，在管井内安装深井泵，抽取地下水，达到降低基坑内的地下水位，以利于地下室在干燥条件下顺利施工的工艺方法。
2  工法特点
    2．l  降水效果显著。
    2．2  施工机具简单多样，便于选择。
    2．3  耗资少。
3  适用范围
    3．l  本工法适用于涌水量较大，渗透系数较大，长江流域一级阶地上二元结构地层的基坑降水。
3．2  本工法对大面积、深基坑尤为适用。
4  设计要点
4．l  降水井
4．1．l  管井结构
合理的管井结构，要求达到能使地下水畅通地流入井内，同时
With the development of urban high-rise buildings, more and more deep excavation. As the deep foundation design and construction by the geology, hydrology, environment, season, load, and many other factors, geological conditions in the dual structure, the deep excavation of the main contradiction is the issue of groundwater management, especially in the high water table, thick confined aquifer, water-rich hydrogeological conditions, groundwater treatment if properly produced in the excavation process is extremely easy flow of sand and piping, influence field area around the buildings and the safety of public utilities. Obviously, the general precipitation are difficult to meet the requirements. Building technology in the construction of three Research and Design Institute Board through several projects the practice, exploration, and gradually formed a set of deep well dewatering technology. Lithologic composition in geological structures with significant deposition of binary rhythm, Pressure Water Jude Biao only l ~ 2 meters, 30 meters thick Wuhan International Trade Building, using the success of this new technology. And was in the construction of the Third Bureau of Science and Technology Progress Award for the year 1995, while the main body of Wuhan International Trade as part of an integrated construction technology by 1995, China State Science and Technology Progress Award.
Engineering Principle 1
    Deep well in the excavation before the pit area according to size, discharge and other factors, in advance of the pit, pit pit outside or inside and outside the combination of laid a number of tube wells, tube wells installed in the deep well, pumping of underground water, to reduce groundwater within the excavation, in order to facilitate the smooth basement construction in dry conditions, the process method.
2 Characteristics of Workers Act
    2. l precipitation effect is remarkable.
    2.2 Construction of simple machine and diverse, easy to choose.
    2.3 cost less.
3 Scope
    3. l The construction method applies to discharge large hydraulic conductivity is high, the Yangtze River basin level terraces dual structure of the foundation pit formation.
3.2 The construction method for large area, especially for deep excavation.
4 design points
4. l dewatering well
4.1. l tube well structure
Rational structure of tube-wells, required to enable the smooth flow of groundwater into the wells, while