Research On Pile-Soil Interaction Effect Under Horizontal Earthquake

The separation model is used to consider the motion interaction and the inertial interaction of the piles respectively,and the phase difference obtained from the experiment is used to calculate the vector sum of the two.For the movement interaction,the dual-spring response displacement method is developed based on the elastic foundation beam model to calculate the pile side soil pressure increment and the pile displacement,bending moment,and shear force.For inertial interaction,the mature m-value method is used.In the test,with the 10t load of the shaking table,the viscoelastic boundary was designed and fabricated,which can better eliminate the boundary effect of the model box and realize the vibration simulation of the infinite foundation.Designed and fabricated the high-position and low-position elastic particle system,and studied the phase difference law of the upper particle and the site displacement of the different frequency structure.On the basis of the shaking table test,the test displacement value is fitted,and the measured pile body bending moment is used as the benchmark,and the soil spring stiffness value is obtained by inversion using the dual spring response displacement method;and multi-condition verification,analysis and test data are carried out The regularity is higher.The main conclusions are:1.After the laminated shear box increases the viscoelastic boundary,the displacement amplitude and curve shape of the test soil layer can be obviously adjusted,as well as the acceleration amplitude.2.The time history of the increase of soil pressure on both sides of the pile is reversed.When one side reaches the positive peak,the other side reaches the negative peak.The positive peak is greater than the negative peak.3.The pressure value measured by the pressure box is an incremental value,which is a physical quantity related to displacement.The positive dynamic earth pressure value is the increase in contact force produced by the compression of soil particles.The negative pressure value is caused by the unloading of the active side of the pile.It is a negative pressure increase and has a clear physical meaning.Applied to the dual-spring response displacement method,the active side spring exhibits negative stiffness.4.The spring stiffness of the test pile side soil was back-analyzed by the dual-spring reaction displacement method.The passive side is 12MPa/m,which falls within the range of the relevant code(3?15MPa/m).The average shear strain of the soil layer in the shaking table test is 2.7x10^-3,which is in the same order of magnitude as the corresponding average strain of the actual site of 8.2x10^-3,reaching 33%of the average strain of the actual site,which is relatively close.Therefore,the soil spring stiffness inverted by the shaking table test has practical engineering significance.5.The measured phase analysis shows that the difference between the particle vibration phase of the long-period structure and the soil phase of the site is greater than 90°;the difference between the particle vibration phase of the short-period structure and the soil phase of the site is mostly less than 90°,and a small part is greater than 90°.To be conservative,the sum of the two interaction vectors of the long-period structure can be replaced by the SRSS method,and the vector sum of the short-period structure can be replaced by the algebraic sum.6.The measured phase analysis shows that the strain of the pile body is synchronized with the displacement of the site.The dual-spring response displacement method conforms to the dynamic response mechanism of foundation piles,and can be used to calculate and analyze the contact force of the pile-soil movement interaction and the increment of pile body effect under earthquake action.