MODEL EXPERIMENTAL RESEARCH ON ANTI-SLIDING CHARACTERISTICS OF MICROPILES WITH CAP BEAM
SUN Shuwei1，2，ZHU Benzhen1，MA Huimin1
(1. Northwest Research Institute Co.，Ltd. of C.R.E.C.，Lanzhou，Gansu 730000，China； 2. Department of Hydraulic and Hydropower Engineering，Tsinghua University，Beijing 100084，China)
Abstract：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.
