Study On Compacting Effects And Construcrion Measures Of JAcked Pile

Jacked pile is widely used because of its various advantages such as noiseless, vibrationless, no impact and minor construction stress. However, the obvious compacting effects caused by the penetration of jacked pile may have severe influence on surrounding engineering environment. So it is important for engineering application that compacting effects of jacked pile are effectively predicted and construction measures that can decrease the compacting effects of jacked pile are taken. Through the detailed analysis of cavity expansion theory, strain path method and finite element theory applied in jacked pile, some deficiencies are put forward. According to the analysis,some main original work are made.Firstly, on the basis of strain path method (SPM), closed-form analytical expressions of displacement fields caused by the installation of jacked pile are obtained in small strains. The expressions can take into account some important aspects such as stress-free ground surface, incompression of soil, prebored hole and tubular pile. Through the analysis of displacement field, the variation rules of horizontal and vertical displacements are obtained. The integrate expressions of large strain are deduced by means of SPM. And the difference of the soil compacting effects in the condition of large strain and small strain is analyzed.Secondly, according to the analytical expressions of single jacked pile, the displacement fields of subsequent jacked pile due to the presence of adjacent pile are obtained. The expressions of displacement fields of dorsal and frontal surface for two piles, row piles and group piles are derived. The solution taking into consideration the effect of construction sequence of jacked pile accords with the actual engineering.Thirdly, some shortcomings that numerical simulation can't effectively applied in jacked pile are proposed. Several problems need to be resolved in numerical simulation of jacked pile; for instance, finite deformation problem, constitutive model of soil, contact between pile and soil and loading problem. Then displacement fields are researched via the finite element model that accords with actual process of jacked pile. And the effects of displacement fields caused by difference modulus ratio, friction between pile and soil, possion ration of soil and soil index of c and Φ are put forward. On the same supposition, the numerical solution and analytical solution are agreeablewith each other.Fourthly, some construction measures that are used to decease the compacting effect are analyzed by use of finite element method. And the impact of construction measures such as prebored hole and groove that prevent the compacting effect is discussed.Finally, comparisons are made between theoretical and measured displacement. In general, satisfactory agreement is found.