Research And Application Of Pile-raft Foundation For Replacement Of Pile Foundation

In the construction project, There are more and more engineering quality problems.With the rapid economic development, more and more high buildings are built,Therefore, pile foundation is widely used in engineering.however, as we know, the pileis underground engineering, It is hard to judge whether the quality is good or not. theproblem will be found after the piles are completed. Pile foundation engineering qualityproblems could be derived from the survey and design construction increase indetection, etc. We can use piled raft to replace the pile foundation when the pile is bad,By changing the original load transfer path of structure,it shifts the load on the newpiled raft and decreases the load ratio of the primary pile, The original pile bearingcapacity is designed as safety reserves.The piled raft has the advantages of largestiffness、high bearing capacity, and so on. The raft is mass concrete, So temperaturestress control is important and difficult in construction. The crack of raft will decreasethe bearing capacity. When the pile holes are constructed, however, the foundation haslarge compression stress, we must plan the order carefully, or accident may emerge andcause much loss.Based on some one great pile replacement project, this paper presents thefollowing work:①This paper presents the tectonic form between the raft and primary piles, theconstruction order of the bar holes in the primary piles,the location of bar hole, thedesign, theory and test methods of grouting.②By optimizing the plane position of piles, and with the help of birth-and-deathelements of ABAQUS, different construction order of piles are simulated to know thedeformation for foundation,then choose the best construction order.③Based on the mass concrete temperature field, the temperature stress andrestraint stress can be computed, what is more, regularities distribution of stress andtemperature crack controlment methods will be known.④By the MIDAS, the temperature stress is simulated, According to comparing thesituations for restrain and non-restrain, some measures are adopted to decrease therestraint stress.