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导管架平台桩身循环往复运动将使桩周土体超孔隙水压增加、横向土抗力降低,从而导致桩基弱化。泥面以下6倍桩径处嵌固桩身的等效桩简化理论没有考虑桩基弱化对平台基础自然频率的影响,计算结果与实测值有一定差距。为研究桩基弱化对平台结构横向振动特性的影响,进行了比例尺为1:10的导管架平台模型试验,测量不同循环荷载作用之后导管架平台模型水平方向的振动特性。由试验结果可知,桩基横向土抗力在不同循环荷载作用过程中出现不同程度的衰减,桩基土抗力的衰减与桩身往复运动的幅值和次数有关。考虑桩-土相互作用时导管架平台模型两个水平方向的基础自然频率(基频)比等效桩理论计算值分别低15.5%和6.0%。桩基弱化后,实测值与计算值的差距增大到22.0%和13.4%。假设导管架-桩-土系统阻尼为比例阻尼,通过试验结果发现,桩基弱化对系统阻尼影响较小。
The cyclic reciprocating motion of the jacket of the jacket pipe platform will increase the excess pore water pressure of the soil around the pile and reduce the horizontal resistance of the soil, resulting in the weakening of the pile. The simplified theory of the equivalent piles embedded in the pile body under 6 times of the mud surface does not consider the influence of the weakening of the pile foundation on the natural frequency of the platform foundation. The calculated result is different from the measured value. In order to study the influence of the weakening of pile foundation on the lateral vibration characteristics of the platform structure, a jacket platform model test with a scale of 1:10 was conducted to measure the horizontal vibration characteristics of the jacket platform model under different cyclic loads. From the test results, it can be seen that the lateral soil resistance of the pile foundation attenuates to some extent during different cyclic loadings. The attenuation of the soil resistance of the pile foundation is related to the amplitude and the number of reciprocating pile movements. The fundamental natural frequency (fundamental frequency) of the two horizontal directions of the jacket platform model considering the pile-soil interaction is 15.5% and 6.0% lower than that of the equivalent pile respectively. After the pile foundation weakens, the difference between measured value and calculated value increases to 22.0% and 13.4%. Assuming that the damping of jacket-pile-soil system is proportional damping, it is found from the test results that the weakening of pile foundation has little effect on the system damping.