Application And Study On Thelager Diameter Anddeep Penetrationsteel Pipe Piles

In recent years, with the rapid development of economy in our country, the construction for the port terminal extends to deep water regional, and the sea-crossing bridge also proceeded towards maximization. Pile foundation, as the only choice of the projects for deep water port terminal, sea-crossing bridge and etc. tends to be of large diameter and super length, while the theory of the pile gained progress rapidly. However, considering the variation of the soil and complicated of the pile and soil, the study on the pile foundation theory has yet to be further improved, especially for the large diameter and the super length piles.Large diameter and super length steel pipe piles located at the coastal areas where cover poor isotropy soil of several dozen meters, associated with mud, silt and weak earth etc. The complex nature geology makes the mechanics properties further complex. Therefore, it is no way to get the exact result for the properties of the large diameter and super length piles by a simple theory resolution. It is possible to establish an experienced calculation formula by accumulating plenty of testing data and according to the theory to solve changes regularity, and that the formula helps designers aware of the deformation mechanism of large diameter piles and it is easier for the construction personnel perform experienced judgment.On the basis of summary for the status of bearing capacity theory, static load and dynamic performance for piling foundation in the current domestic and overseas projects, the thesis is studying on the following four aspects:(1) Static load test for the above sea piling foundation and high-strain dynamic test for piling foundation had been performed for two of the large port terminal projects, which provide the values of maximum force by the hammer blow, input energy, ultimate bearing capacity and etc. It is known that the static soil resistant values always increase when the depth in the dust increase. The static soil resistant values decrease apparently while the pile tip drives into the soft soil from the hard soil. Values of coefficient of restitution can be obtained by the initial high-strain dynamic test and the retapping test. And the coefficient of restitution has something to do with interregna. The correctness of the test can be insured through the comparison of the high-strain dynamic test and static load test.(2) By the way of statics and the test results, the axial force and the distribution of a friction resistance, the curve of which are uniformly on the convex. The friction resistance has something to do with the embed depth of the soil by analyzing play character of the friction resistance and the pile tip resistance which is not synchronized. To fully use of the pile tip bearing capacity of the required settlement is much greater than the friction resistance's.(3) By the dynamic piling formula and the test results, studying on the drivability of the full diameter steel pipe piles, it is known that the capacity of the hammer blow and the depth in the dust are two of the important factors which impact the drivability of the piling foundation. The penetration, the depth in the dust, the ultimate bearing capacity, the exchanged pallets and etc. which would impact the systematic efficiency of the piling can be obtained during the process of the energy transmitting.(4) The statics analysis of the soil plug can be performed through the effective stress method which would obtain the soil plug formula, the result of which is consistent with the test result. The impact of the occlusion effect was researched by studying on different pile tips and soil properties on pile ends. The occlusion effect in the crushed gravel and mixed clay is apparently stronger than it was in the weathered rock. While the occlusion effect is not obviously when different pile tips are in the weathered rock. The coefficient value of the occlusion effect can be obtained when the opening full diameter steel pipe piles are in the weathered rock.(5) Through the effective stress theory, pile capacity of different stop time was derived, to analyze the pile capacity with time, and the general characteristics of capacity growth.