框架微型桩结构抗滑特性的模型试验研究

 基于模型试验结果，对框架微型桩结构的抗滑特性进行研究。研究结果表明，滑坡推力作用下，框架微型桩结构中微型桩顶水平位移与荷载之间为双曲函数关系，且框架梁在荷载作用下发生倾斜，后排微型桩产生较为明显的被拔出趋势。对土压力以及桩身弯矩的监测结果表明，均布荷载作用下，作用在框架微型桩结构上的滑坡推力的分布近似为梯形，滑面及桩顶部土压力较大，桩底部土压力较小，后排微型桩受到的滑坡推力比前排桩大，推力最大值之比约为1∶0.6，滑面以下桩后土抗力的分布近似为倒三角形。将微型桩布置更为密集的微型桩框架结构具有更大的极限抗力；但是，在相同位移容许值的条件下，试验中2种结构的抗滑承载力差别不大。框架梁可以有效限制微型桩顶位移并减小桩身弯矩，但也会在微型桩顶部产生较大的弯矩，故实际工程中可以采取增大截面尺寸、增大框架梁埋深或增设套管等措施提高微型桩截面的抗弯刚度，从而提高框架微型桩结构的整体抗滑性能。

MODEL EXPERIMENTAL RESEARCH ON ANTI-SLIDING CHARACTERISTICS OF MICROPILES WITH CAP BEAM

Based on the model experiments，the anti-sliding characteristics of micropiles with cap beam were studied. It was shown that，a hyperbolic function could be used to describe the relationship of load and lateral displacement of micropile head. Micropiles in the rear row were trend to be pull out and the cap beam is tilt during the loading process. It was shown by monitoring the soil pressure that pushing force acting on micropiles with cap beam was trapezoidal distribution，and the resistance force below sliding surface was inverted with triangular distribution. The soil pressure value was larger at micropile head and around sliding surface and smaller at the bottom of micropiles. The ratio of pushing force acting on the micropiles between the rear row and leading row was 1∶0.6. Micropiles with cap beam and smaller spacing of micropile have larger anti-sliding capacity，but under the same value of the acceptable displacement，there was not a big difference between the two structures in the experiment. The pile cap beam could restrain the lateral displacement of micropile head and reduce the bending moment of micropile body effectively，meanwhile produce a higher bending moment at the micropile head，thus some methods，i.e. installing an oversized casing in the top portion of micropile，constructing a larger pile diameter at the top，embedding the pile cap deeper and so on could be adopted reasonably in engineering practice.