Study On Prestressed Concrete Pipe Pile And Compaction Effect Of Pile Driving

Prestressed concrete pipe pile is a new type of precast concrete pile. This type of pile has many advantages, such as simple technology, better quality, low cost and convenient detection, so it has been widely used in geotechnical engineering during the recent years. Though with the above merits,its compaction effect of pile driving still needs to be further researched, and its design theory needs to be further perfected. So the study on prestressed concrete pipe pile is of great theoretical and practical significance.Firstly, this thesis reviews development history of prestressed concrete pipe pile and introduces methods of design, construction and detection. Several problems that arise frequently in engineering application are discussed, and the author gives his own viewpoints on these problems.Secondly, cavity expansion theory is applied to study compaction effect of pile driving. Vesic's solutions to cavity expansion that include cylindrical cavity expansion and spherical cavity expansion are introduced. Then cylindrical cavity expansion theory is applied to study compaction effect of pile driving in saturated soil. Based on the results of conventional triaxial tests, a trilinear curve model is used to simulate stress-strain curve of strain-softening materials. Meanwhile, trilinear curves are also used to simulate curves of volumetric strain, minor principal strain and major principal strain. By using elasto-plastic theory, analytical solutions to cylindrical cavity expansion in strain-softening soil are presented. According to the mechanism of statically pressed pile driving, compaction effect of pile tip can be viewed as hemispheric cavity expansion. Therefore spherical cavity expansion theory is applied to obtain the solutions to stress, strain, displacement fields and final pressure. Resistance force of pile tip is calculated to estimate static pressure.Finally, this thesis discusses time effect on bearing capacity of statically pressed pile. The mechanism of time effect on bearing capacity is analyzed, and relation curve of bearing capacity and time is obtained by using curve fitting method to handle re-pressure test data. According to this relation curve, increase tendency of bearing capacity with time is represented, and an empirical formula is given to estimate bearing capacity of statically pressed pile at some time after pile driving. This thesis promotes the research on work mechanism and design theory of prestressed concrete pipe pile, so it is of important theoretical and practical significance.