| The near-surface soil existing in engineering environment of pipe piles is mostly unsaturated,consists of three-phase system: solid skeleton and pores,with water and air filled in the pores.Because of the characteristics of the hollow section of the pipe pile,in addition to the outside pile soil,the joint action between the pile and the soil plug must be taken into consideration,resulting in the force mechanism is more complicated.As a new type of pile and because of the complexity of the problem,the pile dynamics field has mostly focused on the dynamic response of a solid pile in a single-phase or saturated two-phase medium.In this paper,based on the latest research results of unsaturated soil mechanics and soil dynamics,the hydraulic properties of low-saturated soils are first studied through a more accurate micro-mechanical physical model,and then the incident SH-waves are studied based on the wave equation of three-phase porous media.At the same time,the horizontal dynamic response of pipe piles in unsaturated soil,and finally a small-scale shaking table model test study was conducted on the interaction between unsaturated soil and pipe piles.The main research content includes the following aspects:(1)The unsaturated soil particles are approximated as ellipsoids.Based on the Young-Laplace equation,a liquid bridge calculation model with two different sizes of ellipsoidal particles is established.It is calculated by the ring hypothesis solution and the Young-Laplace equation numerical method respectively.The effects of contact angle,roughness,ratio of the two particles,and the flatness of the particles on the capillary force and the volume of the liquid bridge were evaluated.The ring hypothesis method was used to evaluate the error,and the shape of the liquid bridge obtained by the two calculation methods was described and compared.In addition,the soil-water characteristic curves of low-saturated soils with different contact angles and roughness were calculated based on the contact sphere model consisting of the same ellipsoidal particles.(2)Based on the Novak three-dimensional continuum model,the horizontal displacement solution of the free-field soil subjected to the SH wave is firstly solved for the horizontal vibration of the pipe pile due to the SH wave incident.Then the full consideration of the materials between the phases in the unsaturated soil is given.The inertial and viscous coupling effects and the capillary pressure effect are decoupled by using the Helmholtz vector decomposition and the separation variable method for the three-dimensional wave equations of the porous media to obtain the horizontal displacement and horizontal dynamic impedance of the soil around the pile and the soil under the pile-soil interaction;Then based on the Euler beam model,considering the continuity condition of the pile-unsaturated soil and the boundary conditions of the pile top and the pile tip,the dynamic balance equation of the single pile in the unsaturated soil under the SH wave is established,and the horizontal dynamic amplification factor of the pile is obtained.The frequency domain solutions of the horizontal and horizontal dynamic impedances are used to analyze the resonance effect of the pile-soil system,and the distribution laws of the pile body displacement,bending moment and shear force along the depth are investigated.(3)Under the condition of the pile-soil interaction,the seismic performance of PHC pipe piles under unsaturated soil conditions is studied through small-scale shaking table model tests.The test adopted a layered shearing earth box,and by setting factors such as soil compaction range,soil plug height,site soil layering,and pile end support conditions for different piles,different excitation frequencies and intensities were applied to each model.Based on the distribution of bending moment,shear force and displacement along the pile,the vibration response law of the pipe pile in the unsaturated soil and the influence of the vibration parameters are discussed. |
PDF Full Text Request