扬州深大基坑降水方案优化设计

扬州东部综合客运枢纽地下配套工程深大基坑采用大放坡+地下连续墙+内支撑围护，场地地层为深厚强透水地层，降水井布置在坡底还是坡间平台，将直接影响降水的动态控制。本文提出了方案一（坡底布井）和方案二（坡间平台布井）2套降水方案，并利用数值模拟方法进行了比选。对比结果：虽然方案一井数和最终总涌水量略少于方案二，但是需提前降水，会造成大量水资源的浪费；而方案二可以根据基坑开挖深度的增加，逐步增加抽水井，体现了按需降水的原则。因此，认为方案二更优。类似基坑进行降水方案设计时，不应仅考虑总井数和最终总涌水量，还应考虑到不同开挖阶段，动态控制、按需降水，才能从源头上实现基坑工程的绿色施工。

Optimized dewatering design for a deep and large foundation pit in Yangzhou

This article describes the foundation pit dewatering case of the underground support project of the Comprehensive Passenger Transportation Hub in the East of Yangzhou, where step-slope excavation is adopted as well as diaphragm wall and inner support in the foundation pit excavation. Since the aquifer is thick and highly permeable, deployment of the dewatering wells, either at the bottom of the slope or the inter-slope platform, will directly affect the dynamic control of dewatering. In this paper, two dewatering plans are proposed for comparison: in Plan 1, wells are arranged at the slope bottom; while in Plan 2 wells are arranged at the inter-slope platform. Comparison results from the numerical simulation method show that: in Plan 1, although the number of wells and the final total flow rate are slightly smaller than the those in Plan 2, the need to pre-dewatering will result in a large amount of water waste; in Plan 2, the pumping well number can be gradually increased with the depth of the excavation, reflecting the principle of dewatering on demand. Therefore, Plan 2 is considered to be better. This research can serve as a reference to the dewatering design of similar foundation pits: not only shouldthe total number of wells and the final total flow rate be considered, but also the different excavation stages. By implementing the principles of dynamic control and dewatering on demand, the green construction of foundation pit works can be realized from the very start.