Numerical tests on the mechanism of the cushion in composite foundation;

According to the results of in-situ tests,the failure mechanism of composite foundation is mainly decided by the interaction between soil and cushion in the state of thick cushion or under embankments;and the practical bearing capacity of a pile in composite foundation is not brought into full play.

A cushion is installed under a pile cap, then the load is redistributed between the pile and soil.

According to the laboratory and in situ tests, this paper discusses into the roles Of the mattress of compositefoundtion with cement, fly-ask, gravel pile (CFGP), the bearing ratio of CFGP to soil under the vertical loads, and thedeformation behaviour of the compsite foundation.

The optimization of mattress layer in CFG pile composite foundation;

It introduces design method of handling compound foundation by low-strength concrete pile,puts forward fixed 5 parameters in design,narrates calculative process of compound foundation by low-strength concrete pile,and points out importance of mattress layer of compound foundation.

Discussion on influence of cushion to load transfer rules of composite foundation;

Test study on influence of cushion on loading behavior of composite foundations;

Further study on calculation of the designed thickness of cushions in composite foundation with rigid piles;

Through the indoor simulation experiment research to the compound foundation using cement-soil pile,it analyzes and gets the relation among the pile length,bedding cushion and stress ratio,and points out this experimental model is worth to generalize due to the convenient operation,timesaving and labor saving,and realizing many experimental functions.

According to common used bedding cushion materials, authors made some static loading tests to study effects of different bedding cushion materials in rigid-flexible pile compound foundation and influence on bearing capability and deformation performance of compound foundation.

In this paper through the comparisons with foundation treatment methods and the construction of CFG pile a conclusion is drawn that this foundation treatment method is effective method, at the same time some helpful discussion are carried out according to the functions of pile length and bedding cushion.