扩底桩的优点是显然的,它不仅可以节约成本,而且在某些情况下,如我国江汉平原及类似场地中的二元土结构(上部为软土,下部为砂、卵石),可很好地解决等径桩很难处理的地基问题。国外扩底桩的应用发展很快,有的国家扩底桩在钻孔灌注桩中的比例,由10％猛增至50％到60％。但他们近年来所设计的钻头大都是集机械、 The advantages of peri- ly-explorated piles are obvious. It not only can save costs, but also in some cases, such as the binary soil structure in the Jianghan Plain and similar sites in China (the upper part is soft soil, and the lower part is sand and pebbles). It is a good solution to the foundation problems that are difficult to deal with isometric piles. The application of expanding piles abroad has developed rapidly. In some countries, the proportion of piles with enlarged bottoms in bored piles has soared from 10% to 50% to 60%. However, most of the drills they designed in recent years are mostly mechanical,