The Study On Model Experiment Of Pile Penetration By Synchronous Dynamic Grouting And Bearing Capacity

With the rapid development of urban infrastructure construction, high-rise buildings continue to emerge, pile has become the main basis form of a high-rise buildings. The Jacked pile is more widely applied in multi-storey buildings and high-rise buildings in China's soft soil area, because of no noise, no vibration, high construction speed and reliable quality. In recent years, with its popularization and application in the north of china, it is found that it is difficult for jacked pile to cross the middle and thick sands and hard soil in rivers and lakes'sedimentary area. This problem affects the applicable range of jacked pile in a large sense. Penetration accompanied with synchronous skin grouting is a good thought of solving this difficulty. The application of this method can reduce resistance in the process of installation and after solidifying of grout, the section of the pile will be magnified, meanwhile the soil surrounded the pile will be consolidated. As a result, the bearing capacity will be improved. As for engineering practice, it can decrease the diameter and length of the pile, reduce the project costs. Consequently, researching in this aspect is very significant for the promotion and application of jacked pile in the practice. Presently, this method is still at a phase of research and discussion. How the effect does still needs to put to the test.In view of this, this article relied on Natural Science Foundation project of Shanxi Province "Synchronous Dynamic grouting method to reduce jacked pile resistance and improve the bearing capacity of piling mechanism of experimental research " (item number: 2008011055), combined the research achievements of many scholars at home and abroad, researched the influence of synchronous skin grouting to the jacking pressure,dynamic skin friction and the vertical compressive bearing capacity of jacked pile in the process of installation by the laboratory study, and achieved the following results:(1)Through the test of model pile with three kinds of diameter, contrasting the result between synchronous skin grouting and not grouting in the process of installation in sands, it is found that jacking pressure decreased about 20%. It indicates that the method of synchronous grouting can decrease penetrating resistance efficiently. Thus, it provides the foundation for solving the difficulty of installation in middle and thick sands in practice.(2)Through the test of installation of model pile with three kinds of diameter in sands, the trend of jacking pressure and skin friction of jacked pile in the process of installation is revealed initially.(3) Through the static load test of model pile with three kinds of diameter in sands, the distribution curves of axial force and skin friction along the pile are obtained, and the rules about load transference are studied. (4)According to the data of static load test, the curves of load-settlement are drawn. Based on the features of curves and the country standard, the ultimate bearing capacity is confirmed. By analysis, seven days after finishing penetration, the ultimate bearing capacity increase 15%, fourteen days after finishing penetration, the ultimate bearing capacity increase 35%. It shows that the method of synchronous skin grouting can improve the ultimate bearing capacity efficiently.(5)According to the data of test, the relation of final pressure and the ultimate bearing capacity at the condition of synchronous dynamic grouting and not grouting is analyzed briefly. The conclusion is: the ultimate bearing capacity is greater than final pressure.