The Model Test Research On Geogrid-reinforced And Pile-supported Foundation

In this thesis, the existing theory and design methods about pile reinforced earth composite foundation and composite foundation with entirely flexible pile mat on top were reviewed and summarized.A total of 20 groups of static loading model test were conducted including:pile reinforced earth composite foundation model test, model test on composite foundation with entirely flexible pile mat on top and model test on performance characteristics of composite foundation with different pile-soil stress ratio.1. The influences of different pile stiffness, different geotextile layers and location and different loading methods on settlement and differential settlement of composite foundation, pile-soil stress ratio, strain of pile and geogrid were analyzed.2. The analysis of the influences of different pile stiffness composite foundation with entirely flexible pile mat and geogrid combinations on settlement and differential settlement of composite foundation, pile-soil stress ratio, strain of pile and geogrid were also presented.3. This thesis also analyzed the influences of different pile stiffness and moisture content of the foundation on composite foundation settlement, pile-soil stress ratio and strain of pile.Through the analysis of the test results, it can be seen that pile reinforced earth composite foundation could improve the settlement and differential settlement of composite foundation significantly and reduce negative friction, meanwhile, pile-soil stress ratio and average strain of pile increased accordingly. The improvement was different for composite foundation with different pile stiffness. After adding flexible pile mat on top of composite foundation, the pile-soil stress ratio reduced significantly and the bearing capacity of soil between piles can be full played, but the total settlement and differential settlement of composite foundation and negative friction increased simultaneously. For the pile mat with geogrid on top, it can not only reduce the pile-soil stress ratio of composite foundation, but also control its total settlement effectively. As for composite foundation with different pile-soil stiffness ratio, the foundation settlement and pile-soil stress ratio increased significantly with the increasement of pile-soil stiffness ratio. In this situation, the pile will bear more load, which required high bearing capacity of pile. Therefore, when the pile-soil stiffness ratio reached a certain level, Almost all of the stress concentration to the pile, foundation bearing capacity of soil can not play, The meaning of composite foundation has been loss.Based on the test results and design methods in the existing literature, discussed the Geogrid-reinforced and Pile-supported Foundation designing methods and procedures, and gave an example to certify the designing method and procedure. Finally, some suggestions on the design of composite foundation with entirely flexible pile mat were put forward.