Study On Effects Of Pile Driving On Surrounding Environment And Its Prevention Measures

With the development of the construction of urban underground space, piledriving has caused a number of severe environment problems. Soil-compactingassociated with the process of pile driving will bring a degree of disturbance to thesurrounding soil, change its stress state and have some impact on the existingstructure, road and pipeline close to the pile area. Therefore it is greatly significantto study on the effects of pile driving on surrounding environment and measurestaken to improve safety and economics.This paper first recites and analyzes the present research status and methods.Then based on the above analyses a more comprehensive research concerned aboutthe soil-compacting problem is made as follows:（1）With the infinite-element model established by ABAQUS, a detailedanalyses about the stress and displacement state of pile driving in homogeneoussoil is carried out, considering the influence of large deformation, soil self-weight,dynamic friction and other factors. It also discusses some acting parameters suchas elastic modulus, Poisson’s ratio, cohesion, internal friction angle and dilatancyangle.（2）The displacement field and stress field of pile driving in different layeredground, for example, a hard soil layer that lies above and a hard(soft) soilinterlayer that exists,are analyzed, pointing out that there will be a stress fracturelayer at the intersection between the hard layer and the soft layer, where significantmutations of horizontal displacement occur and the value is larger than that of thehomogenous condition.（3）The distribution and dissipation of the excess pore water pressuregenerated by single pile soil compaction is analyzed.The effects of different soilparameters on the excess pore water pressure distribution is given, and derived the excess pore water pressure in the radial logarithmic decay, affecting20to30timesthe range of the pile diameter.（4）Taking into account the influence of pore water pressure and consolidation,a pile group of two piles is established to study the problems of pile drivingconcerned about displacement, effective stress and excess pore water pressure. In afurther step, the model of3*3piles group is established and the study ondisplacement field is given. Based on the study of the effects of different sequencesof pile driving on displacement field, it is found that a former pile will produce ashielding effect on soil-compacting of the follow-up pile driving.（5）Through the reduction of elastic modulus of the neighborhood pile, thenumerical simulation is used with the axial symmetry model to study thesoil-compacting effect when a neighborhood pile exists. This paper discusses thecompact effects on the soil surrounded and the influence on the neighborhood pilebrought by pile driving, respectively, in different soil layer situation,pile spacingand pile radius. It is found that in homogenous soil, the neighborhood pile subjectsto the axial tension and in the2/3length of the pile it obtains its maximum value.However, in inhomogeneous soil, the force condition on both sides of the pilediffers greatly. Apart from the axial extension, the pile is subjected to the deflectioneffect.（6）The engineering measures to reduce the influence brought by pile drivingare summarized. And the analyses of the effect of controlling pile driving speed,setting pre-drilling bore and anti-squeezing ditch on pile driving are also included.