Research On The Effect Of Tunnelling On The Bearing Behavior Of Piles

Based on the existing research results, the influence of tunnelling on pile foundation inexisting buildings is studied. The load transfer mechanism of axially loaded pile and theinteraction of soil and pile are discussed.This paper research content mainly includes several aspects:（1）The equivalent formation damage model is established, based on the stratumdeformation model and boundary conditions of formation damage, the level distribution loadsof Mindlin fundamental solutions is adopted, the horizontal and vertical expressions of soildisplacement due to tunnelling are solved. Using the three-dimensional finite differencemethod, the analysis model of tunneling is established to analyze the soil horizontal andvertiacal distribution.（2）Adopting p-y curve method, the analytical solutions of single axially loaded pile areobtained by the difference method; Based on the Winkler foundation model, the load transferequation of the single pile subjected to passive displacement is established, the analyticalsolutions of horizontal displacement and vertical displacement of the single pile caused bytunnelling in homogeneous and heterogeneous foundation are worked out. By the analysis ofthe example, the horizontal displacement, vertical displacement and the axial force of thepile due to tunnelling in homogeneous foundation are obtained.（3） According to the shear displacement method and the Mindlin solution for verticaland horizontal displacement of soil transfer coefficient, considering the shielding of soilvertical displacement of pile foundation, the shielding displacement due to pile foundationshielding effect is calculated. Considering the pile-pile interaction of the passive pile groups,the super position principles are used to calculate vertical displacement and internal force ofpile groups caused by tunneling.（4）Design a kind of test apparatus which can simplify working condition of tunnellingto exert the soil lateral displacement and vertical displacement and then carry out indoor test to research the characteristics of single axial loaded pile and pile groups caused by tunnelling.Based on the different soil displacements due to different tunnel depth, different test groupsare designed. The bearing characteristics of single pile and pile groups are obtained.（5） The pile foundation underpinning is taken with tunnelling, the three-dimensionalfinite difference method is used to simulate the process of tunneling and pile foundationunderpinning construction, the bearing capacity of pile groups in the process of pilefoundation underpinning is obtained.Through numerical analysis, the soil displacement distribution caused by tunnelling isstudied. Through theoretical analysis, the analytic solution of the displacement of soil due totunnelling is solved, and the analytical solution of pile and pile groups due to tunnelling isworked out. The influence of tunnelling on single axially loaded pile and pile groups is futherdiscussed. By the model test, the behavior of axially loaded pile and pile grous subjected totunnelling is further studied.