As the under-reamed pile is a new pile-type, its applied time is not very long in Shenzhen and its peripheral regions, a lot of developers (investors) have very big worry to it.

Analysis on construction method of boring and expanding bottom pile in permafrost region in Qinghai-Tibet plateau;

Construction technology of boring and expanding bottom pile in Qinghai-Tibet Plateau;

Based on the engineering example,discussion is given to the foundation selection of high-rise building in terms of technical and economical feasibilites,and introduction is made to the application characteristic of pump-absorption anti-cycle drilling bottom-enlarged grouting piles and its key construction techniques.

According to the engineering practice,introducing the technical points of drilling bottom-enlarged grouting pile,pointing out the technical measurements of prevention and treatment in the construction.

The paper presents an introduction to the function of the bell-out bored piles and machinery andequipment used for building these piles.

Compared to artificial digging-hole pile, the pumping reverse-circulation under-reamed bored pile has higher adaptability to geological condition, and its construction is safety and reliability.

In the paper, according to its success application in a tall building, the design and construction of under-reamed bored pile is debated in details.

According to successful application of bored pile in a tall building, construction principle of under-reamed bored pile is discussed in details.

The composite foundation formed by CFG pile and drilling ram expanded pile (DRE pile) which used widely in Beijing area are applied to a project, using CFG pile to minimize the building settlement and DRE pile to improve shallow soil bearing capacity respectively.