Bearing Mechanism Analysis And Experimental Research On Gravel Pile Composite Foundation

Relying on the control mechanism of underground excavation formation process program(National Natural Science Foundation) and Chang Zhu Tan Tobacco Logistics Park joint workshop construvtion project, gravel compaction pile composite foundation is selected as the optimal soft foundation treatment plan through comparative analysis. By analyzing the mechanism of compacted gravel piles composite foundation, using methods of site test and numerical simulation, bearing mechanism and stability of gravel compaction pile are deeply studied. And based on the actual situation of the project, concrete construction method is proposed. The main contents are as follows:(1) Based on the topography, hydrology and geological conditions of Chang Zhu Tan Tobacco Logistics Park, the stability of soft-soil foundation and the mechanism of groundwater on foundation are analyzed. Through comparing many kinds of foundation treatment schemes, gravel compaction pile composite foundation is selected as the optimal soft foundation treatment plan.(2)The reinforcement mechanism of soft soil foundation using gravel compaction pile is discussed from aspects of compaction replacement interactions, drainage consolidation capability and the improvement of performance of composite foundation respectively. The specific damage form of gravel compaction pile is presented. Aimed at the actual situation of this project, the construction technology of gravel compaction pile is proposed.(3)Through heavy dynamic penetration test and static load test of gravel pile composite foundation, the result shows that the compactness of pile is good and the characteristic value of bearing capacity satifies the design requirements. The characteristic value range of bearing capacity of three test points do not exceed 30% of the average, and the the average value is more than 100kPa.(4) Through finite element software ABAUQS, the numerical simulation of gravel pile composite foundation is carried out. The load-settlement curves agree well with that by the field test, which verifies reliability of field load test. The result shows that the bearing capacity of composite foundation pile advances with the increase of pile-soil friction coefficient. By comparing the bearing capacities of different pile lengths and diameters, the appropriate increase of pile lengths and diameters can improve the allowable pressure of composite foundation.