分层液化土中桩基侧向动力反应机理的试验研究

Experimental Study of Lateral Dynamic Response Mechanism of Pile Foundation in Stratified Liquefiable Soil

饱和砂土中的桩基侧向动力响应研究一直是岩土工程界与地震工程领域关注的热点,尤其是群桩侧向动力响应机制是需要重点研究的课题之一。基于振动台试验,通过输入2种不同的波形,采用FBG光栅传感系统对饱和砂土中的单桩与群桩侧向动力响应特性和典型测试点的桩土动力p—y滞洄曲线进行研究。研究结果表明:振动初期,单桩和群桩试验孔压增长不大,随后单桩孔压迅速上升,振动后期逐渐下降至0.5,而群桩孔压则上升缓慢;单桩试验土表加速度在振动初期逐步升高后又迅速降低,且加速度放大值略大于台面加速度值,群桩试验土表加速度在振动初期逐渐升高时就达到了最大,且随着孔压比的升高,加速度没有继续放大,而是逐渐减小,直到后期与单桩试验土表加速度重合;饱和砂土液化对单桩承台加速度和位移的影响较大,群桩承台侧向动力响应对液化的敏感程度略低于单桩承台;在振动输入和承台输入相同的条件下,液化后的群桩基础比单桩基础能更好地抵抗侧向力的作用。

The study of lateral dynamic response of pile foundation in the saturated sand has been concerned in the geotechnical field and the field of earthquake engineering. Especially, the lateral dynamic response of pile-groups is always one of the key research topics. Based on the shaking ta- ble test, through two different shaking table waveforms input and using the FBG grating sensing system, this paper studies the lateral dynamic response characteristics of single pile and pile- groups in the saturated sand and the pile-sand dynamic hysteretic p-y curve of typical test points. The research results show that. The pore pressures of single pile and pile groups increase little in the initial stage of vibration, and then the pore pressure of single pile rises rapidly until later peri- od with decreasing to 0.5, while the pore pressures of pile-groups rises slowly＇s The soil surface acceleration of single pile increases and then quickly reduces, and the amplified acceleration is slightly larger than the shaking table acceleration value in the single pile test. In the pile-groups test, the soil surface acceleration gradually increases and reaches the maximum immediately, the acceleration do not continue to enlarge but gradually decreased with increase of pore pressure ra- tio, until it coincides with the soil surface acceleration of single pile. The impact of liquefaction of saturated sand on acceleration and displacement of single pile slab is more obvious and lateral dy- namic response sensitivity of pile-groups slab in liquefaction is lower than that of single pile~ Un- der the same vibration and the slab input conditions, the pile-groups have better resistance to la- teral force than the single pile after liquefaction.