Study on Liquefaction-Induced Ground Movement and Damage to In-ground Structures

据报道，根据地球物理条件，液化的地面移动了几米的大小，对地基桩和埋管等地下结构造成了致命的破坏。这些液化引起的地面运动已被地震工程界公认为是结构抗震设计的关键因素之一。为了弄清液化引起的地面运动对地下结构的影响，在振动台上进行了模型地面试验研究。模型饱和砂土长6.0m，深宽1.0m，采用正弦激励液化。桩模型分别为直径1.8cm和2.2cm的丙烯管和乙烯管，埋在模型地基中。测量了地基的加速度和位移、孔隙水压力、液化土的土压力和模型桩的地层。本实验发现，当地面位移达到最大值时，模型桩的应变不一定最大，这说明所谓的“地震反应位移法”，即通过地面弹簧将地面位移强制施加到地下结构中，不能应用于液化土中的结构。在对实测结果进行详细分析的基础上，得出了液化土横向运动对地下结构的地震荷载与流体的阻力相似的结论。

It was reported that liquefied ground had moved with a magnitude of several meters depending on geophysical conditions and caused fatal damage to in-ground structures such as foundation piles and buried pipes. These liquefaction-induced ground movement has been recognized in earthquake engineering circles as one of critical factors for the earthquake resistant design of the structures.In order to clarify the effect of the liquefaction-induced ground movement on the in-ground structures, the authors conducted experimental studies by model ground on a shaking table. Model saturated sand ground of 6.0m in length and 1.0m in depth and width was liquefied by sinusoidal excitation. Pile models which is acryl and vinyl pipes with a diameter of 1.8cm and 2.2cm were buried in the model ground. The acceleration and displacement of the ground, pore water pressure, earth pressure of liquefied soil and the stratum the model piles were measured.From this experiment it was found that the strain of the model piles was not necessarily maximum when the ground displacement reached the maximum value, which suggests the so-called "Seismic Response Displacement Method" where the ground displacement is forced to in-ground structures through the ground spring, can not be applied to the structures in liquefied soil. Based on the detailed examination of the measured results the authors reached a conclusion that the seismic loading to in-ground structure from the lateral movement of liquefied soil is similar with the drag force of the liquid flow.