桥梁深水基础的发展和展望

Developments and Prospects of Deep Water Foundations for Bridge

桥梁基础是将上部结构荷载传递到地基的重要构件。桥梁深水基础主要有沉井基础、沉箱基础、桩基础、管柱基础、复合基础及特殊基础等类型。沉井和沉箱基础是应用较早的深水基础形式,沉井基础一直沿用至今,而沉箱基础则逐步被桩基础和设置基础取代。桩基础自20世纪70年代以后成为我国最主要的深水基础形式。管柱基础20世纪50年代发源于我国,20世纪80年代后被大直径钻孔桩取代。复合基础一般是沉井或沉箱与桩基或管桩复合,兼具两者优点,但施工费用较高。特殊基础一般指锁口钢管桩基础、地下连续墙基础、设置基础、钟形基础、负压筒形基础和浮式基础等,在国际上应用较多,我国在钟形基础和负压筒形基础方面还是空白。我国在设计规范及理念、基础形式、施工技术与装备、深水地基加固等方面与国外发达国家之间还有差距。随着科技与工业的进步,大直径空心钻孔桩、大型管柱群基础或小型沉井群基础、负压筒形基础、地下连续墙基础、设置基础、新型复合基础以及浮式基础将得到更大发展。

Loads on the superstructure of a bridge can be transferred to soil via its foundations.Therefore,foundations are important components for a bridge.There has been a variety of deep water foundations for bridges,such as open caisson foundation,caisson foundation,colonnade foundation,composite foundation as well as special foundation.Among these,the open caisson and caisson foundations are the early deep water foundations,up till now,the open caisson has still been in utilization,while the caisson foundation has been obsolete and gradually replaced by pile foundation and gravity-based foundation.The pile foundation has been developed to the primary type of deep water foundation in China since 1970s.The colonnade foundation originated in China in 1950s,and has been replaced by large-diameter bored piles from 1980s.Composite foundation usually refers to the combined use of open caisson/caisson and pile foundation/tubular column,which absorbs the advantages of the caisson and the piles,but often gives rise to high construction costs.The special foundations include the interlocking pile foundation,underground diaphragm foundation,gravity-based foundation,bell-shaped foundation,suction bucket foundation and floating foundation,which have got wide implementation overseas,however,the bell-shaped foundation and suction bucket foundation have not been practiced in China yet.When it comes to the issues,like design specification and concept,foundation pattern,construction technique and equipment and deep-water ground strengthening,China still has a long way to go to compete with those developed countries.The development of science and technology and industry will bring more chances for the implementation of the large-diameter hollow bored piles,grouped large-pile foundation,small open caisson plus group piles,suction bucket foundation,underground diaphragm wall foundation,gravity-based foundation,novel type of composite foundation and floating foundation.