Construction Technology For Weak-Foundation Reclamation Works

Reclamation has seen a long history in the coastal areas of China, while reclamation of tidal flats has become an effective means to increase the land area. Major progress in reclamation technology has played a vital role in tidal flats reclamation works, which has evolved from natural displacement of silt by dumping rocks and filling in layers based on past experience to today's foundation consolidation method of plastic drains and treatment of soft seawall foundation by explosion displacement method, and from vast human labor in the past to today's mechanical construction. In particular, the development and progress of reclamation technology has contributed greatly to the safety and reliability of the works and economic justification of investment.In recent years, such reclamation technology has been innovated in China as driving plastic drains in deep water, laying geotextile in deep water, wide application of geotextile in anti-seepage, separation, reinforcement, etc. as well as new techniques and work processes in water closurc and carthmoving plant. However, even wider research and application will be required to meet the development of reclamation works in view of increased requirement of the works and construction difficulty.This article is an analysis of key construction technology for weak-foundation reclamation works, taking the example of 2nd Phase Tidal Flats Reclamation Works in Huangdai, Wenzhou City, based on following features of the project:(1) Coastal construction, influenced much by tide and sea waves, esp. during the typhoon period, which should be taken full consideration in the work program and calculation of major equipment efficiency.(2) Large amount of foundation treatment work to be done under water, raising high requirement for work organization esp. with regard to inter-crossing operations.(3) Filling on silty tidal flat foundation demands full consideration of foundation slip and partial shear damage, necessitating careful observation and testing of loading rate during construction stage and control of loading rate for the dyke.(4) Due to settlement of weak foundation and elapse of time between different layers, settlement shall be allowed for each layer; furthermore, the dyke settlement shall be allowed as final acceptance would not take place until three months after completion of contract.(5) Work method and sequence for special sections and landforms shall be given full consideration. The construction techniques are analyzed from following aspects: placing geotextile under water, placing bedding layer of crushed stones under water, driving plastic drains under water, dumping rocks for dyke, special section treatment, underwater quality testing and control, dyke settlement observation. Through analysis of specific characteristics and difficulties of construction activities, equipment selection, construction progress control, quality control, etc., we have not only provided technical support for construction, but also guaranteed its economic benefits. The study has helped to grasping the construction technology of weak-foundation reclamation, providing experience for major equipment selection, work efficiency calculation, work program, key quality control method, technology risk control, etc.