Study On Bearing Performance Of The Piled Raft Foundation Of #4 Boiler Of Huaneng Yuhuan Power Plant

The bearing and controling settlement capacity of a foudantion is desired higher and higher with large-load upper stuctures appearance. A rafts which has overall stiffness, can control uneven settlement. And piles can carry large load ,and also decrease settlemet of the foudantion. If the two foudantions are combined, the load of the upper structure can be ensured to carry with contoling the foudation settlement effectively. Therefore, a piled raft foudation is prone to a chosen foudation style to bear a stucture with large load.This paper makes use of safety monitoring projects on the piled raft foundation of # 4 boiler of Huaneng Yuhuan Power Plant, to analyse and study bearing capacity of the piled raft foudation. The main content of this paper consists of two parts, one of which is anlysis of a single pile bearing capacity, and the other is study on the overall bearing capacity of the pile raft foudation by experiment in site.It is to analyse the bearing capacity of a single pile by use of comparing the theoretical results which are calculated by method of load transfer with actual data of static load tests. Through analysing the load-settlement trend, the distribution of pile friction-resistance and pile end capacity, and the changes of pile axis load of the two different style of piles ( non-containing rock piles and rock-socketed piles ), the differences of bearing and defoemation between them can be obtained. Then a suggestion can be given to choose a reasonable pile style, by combined the formation of specific conditions, ultimate strength of a single pile and the ease of construction.The study on overall bearing capacity of the pile raft foudation by experiment in site contains time and space by use of field test data. Thtough analysing settlement, pressure of pile and soil, and stess of reinforcing steel bars in the raft in different stages of upper stucture from construction, testing, to end normal operation, load-defoemation characteristics of the pile raft foudation can be obtained based on different loads of upper structure. Then by anlysing settlement, pressure of pile and soil of particular location and period, as well as contrasting pile pressure and soil pressure, the characteristics of distribution load in space by pile raft foudation can slso be obtained.Through combining bearing capacity of single piles and overall bearing capacity of the pile raft foudation, and summing up gains and losses of the pile raft foundation bearing performance, some sugestions are given to choose pile raft foundation for a similor upper sructure.