江西信江航电枢纽工程围堰防渗及降排水研究

Study on cofferdam anti-seepage and drainage in Jiangxi Xinjiangnavigation power junction project

依托江西信江航电枢纽工程对围堰防渗结构、降排水设计和水泵选型等方面进行了研究和总结。采用的复合土工膜加高喷防渗墙的组合式防渗结构具有较好的施工效率和防渗性能。由于砂卵砾石层高压旋喷桩施工质量离散性较大,需要适当增加喷浆时间。基坑降排水的初期排水和经常性排水量根据规范进行计算,在初期排水过程中覆盖层的水排出速度较慢,所以初期排水时覆盖层的给水度可以适当取小值。围堰内基坑降排水建议采用集水明排方式,并根据"两级截水,三级排水"的原则对排水沟和集水坑进行布置。水泵选型应考虑扬程和流量,初期排水可以采用卧式离心泵和潜水泵结合的方式,经常性排水主要采用潜水泵。

Based on Jiangxi Xinjiang navigation power junction project,the cofferdam anti-seepage structure,drainage design and pump selection were studied and summarized.The combined anti-seepage structure of composite geomembrane and high-pressure jetting diaphragm adopted in this project presents a better construction efficiency and anti-seepage performance.Because of higher quality dispersion of high-pressure jet grouting pile in sandy gravel layer,the jetting time needs to be increased appropriately.The initial drainage and regular drainage of foundation pit shall be calculated according to the code.Due to the slow drainage speed in overburden layer,the water supply ratio can be appropriately taken as a small value in the initial drainage.The foundation pit drainage in cofferdam is suggested to adopt the open drainage mode of water collection,and the drainage ditch and sump are arranged according to the principle of"two-level water interception and three-stage drainage".Head and flow shall be considered for pump selection.The combination of horizontal centrifugal pump or submersible pump can be adopted for initial drainage,and submersible pump is mainly used for regular drainage.