微型桩群桩支护滑坡的地震动力响应研究

Seismic behavior of the landslide supported by micropiles

依托大型振动台进行微型桩群桩支护滑坡和无桩滑坡2组物理模型试验。采用El Centro波、汶川波、Kobe波以及不同频率的正弦波作为输入地震波,通过监测滑坡不同位置的加速度、桩身前后土压力及桩身应变等,分析地震作用下2组滑坡的加速度响应规律、桩身前后土压力分布特征、桩身受力情况及破坏模式等。试验结果表明:微型桩群桩支护结构可有效提高滑坡的抗震性,对传播至滑坡体的地震波有一定阻滞作用,尤其是坡脚附近,但随着高程的增大,这种阻滞作用趋于减弱。地震引发的桩后滑坡推力和桩后滑床抗力呈上小下大的"正三角形"分布,桩前滑体抗力和桩前滑床抗力呈上大下小的"倒三角形"分布。地震作用时桩体弯矩峰值呈"M"型分布,其最大弯矩点位于滑面上1.4倍桩径处和滑面下6.6倍桩径处,随着加载量级的增大,滑面上部最大弯矩点上移至3.7倍桩径处。地震激励后微型桩的损伤特征和破坏模式与静力情况类似,呈反"S"型分布,破坏区域主要集中在滑面上1.4~4.0倍桩径范围内以及滑面下1.4~3.4倍桩径范围内。

Shaking table tests were performed to model two landslides（micropiles reinforced landslide and unreinforced landslide）.El Centro waves,Wenchuan waves,Kobe waves and sinusoidal waves with different frequencies were applied respectively.Acceleration response of landslides,dynamic earth pressure distribution in front and back of micropiles,the stress condition and failure mode of micropiles were monitored and analyzed respectively.The results indicate that micropiles have a good seismic performance for landslide,and it can suppress the seismic wave propagating through the landslide,especially at the toe of landslide,however,the suppression decreases with the height.For the dynamic earth pressure distribution in the back of micropiles,the pushing force of sliding mass and the resisting force of sliding bed is distributed triangularly（small at the upper part and large at the lower part）.For the earth pressure distribution in front of micropiles,the resisting force of sliding mass and the pushing force of sliding bed is distributed triangularly（large at upper part and small at lower part）.The peak bending moment of micropile shows an ＂M＂ shape.The maximum bending moment point is near the place 1.4 times of pile diameter above the sliding surface and 6.6 times of pile diameter below the sliding surface under earthquake,and the maximum bending moment point above the sliding surface moves up to the place 1.4 times of pile diameter with the increasing of loading amplitude.The failure characteristics of micropile after earthquake shows a reverse＂S＂shape,which is similar to that under static load conditions.The destruction area of micropile is distributed mainly in the place 1.4–4.0 times pile diameter above the sliding surface and 1.4–3.4 times pile diameter below the sliding surface.