基桩动力稳定性模型试验研究

Model Test for Dynamic Stability of Piles

为探讨动力荷载作用下基桩的动力稳定性,在大型地槽中以均匀细砂模拟桩周土,分别构造不同桩径、桩身埋置率及边界条件的基桩.通过协调加载系统在桩顶施加不同幅值与频率的简谐振动荷载,利用埋设的传感器采集桩身及桩周土的应力应变等动力响应,经对比分析获得桩径、埋置率、荷载频率与大小等参数对桩顶位移的动力影响规律,并验证了基桩的参数共振现象.研究发现:频率观测值小于理论计算值,可用取值为0.5～0.8的系数k予以调整,且动荷载幅值越大、桩周土越深,k的取值就越偏小.

In order to investigate the stability of piles under dynamic loads,an indoor model test was designed,in which homogeneous fine sand was used to simulate the subsoil around the pile shaft with various diameters,embedded ratios and boundary conditions at the top and the toe.Then,simple harmonic loads with different vibration amplitudes and frequencies were exerted at the pile top,and the corresponding dynamic responses of the pile shaft and subsoil（including dynamic stress and strain,etc） were measured with the sensors instrumented among the pile-soil system.Based on the test data obtained,a comparative analysis was made to discuss the dynamic influencing rules of various parameters（such as the diameter and embedded ratio of pile shaft,the frequency and magnitude of dynamic load,etc） on the pile top displacement.Furthermore,the parametric resonance phenomenon of the pile was observed and verified in the test.And the difference between the smaller frequencies measured and the theoretical values may be improved by a coefficient of k ranging from 0.5 to 0.8,which decreases with the increase of the dynamic load amplitude and the depth of subsoil.