Testing Study On Mechanism And Effect Of Post-grouting At The Bottom Of Super Large Bored Piles Foundation

Super large pile groups foundation is commonly applied for great span bridges. With the constantly emerging sea-bridges, dimensions of pile groups foundation are larger and larger. "The success of bridge is up to foundation", so safety and stability have attracted universal attention. However, it is difficult to ensure the quality of over length and large diameter bored pile because of the defects inherent, leading to the complicated mechanical behavior of pile groups foundation. In order to solve these problems, pile-bottom post-grouting technology has sprung up.At present, the research on post-grouting mechanism is confined to the statistical analysis of data, the mechanism and its effect researched by the prototype observation is rare, especially the research on bearing behavior of pile groups foundation and pile top axial force distribution after pile-bottom post-grouting.Based on the National Basic Research Program of China (973 Program)-Basic Research on the Safety of Major Engineering Project in Hazardous Environments (2002CB412707) , National 11th Five-Year Technology Support Project-Research on Key Techniques in the Construction of Sutong Bridge (2006BAG04B01,2006BAG04B05) and Jiangsu Provincial Traffic Science Study Program-the Key Techniques Study on Super Bored Pile-groups Foundation (04Y029) , according to the safety monitoring for foundation of Sutong Bridge, using the methods of theoretical analysis, prototype observation data analysis and numerical simulation, several problems are studied as follows:â‘ Based on the tests and theories at home and abroad, action pattern and mechanism of grouting in the soil and the ways of grouting to the pile tip resistance and side friction were studied.â‘¡According to the mass tracking observation data in period of grouting, mechanics mechanism and effect of pile-bottom post-grouting were analyzed deeply.â‘¢FEM was applied to analyze the effect of post-grouting to bearing behavior of over length large diameter bored pile. The relationship between base consolidation parameters and bearing capacities was summarized. Combined with testing data, the soil parameters after grouting were back-analyzed and bearing behavior of cinquefoil pile groups foundation before and after grouting were simulation analyzed.â‘£Based on the mass measured data during concreting the pier base and cable tower, distribution rule of pile top axial force after grouting were discussed and bearing behavior and effects of pile groups were researched.