路基动力响应与动力破坏的大型振动台模型试验研究

 针对填方路基在强地震动作用下的动力响应和损伤破坏过程，设计并完成1∶20比尺的填方路基大型振动台模型试验。模型的尺寸为1.93 m×3.0 m×1.4 m(高×长×厚)，采用土体材料制备，通过逐级加载的方式，在振动台上对填方路基进行模型试验。在不同类型、幅值、频率的地震波和白噪声激励下，对模型路基的动力响应、抗震薄弱部位、破坏过程以及地震动参数对动力响应的影响进行研究，分析路基及支挡结构的加速度和位移的变化规律。试验结果表明，在水平地震作用下，模型路基对输入地震波具有明显的放大作用，挡土墙顶部及路肩为加速度峰值最大的区域，是抗震薄弱的部位，整个模型路基首先在该位置出现裂缝；在不同的地震波作用下，路基坡面加速度峰值放大系数随着输入地震动幅值的增加呈现递减趋势，路基对输入波低频部分存在放大作用，对高频部分存在滤波作用；在逐渐加载的地震波作用下，模型路基逐渐出现多处开裂。试验结果可呈现填方路基在强烈地震作用下的损伤破坏过程及破坏形态，有助于揭示地震作用下路基结构的破坏机制，为路基的抗震设防提供相应的参考。

LARGE-SCALE SHAKING TABLE MODEL TEST STUDY OF DYNAMIC RESPONSE AND DYNAMIC FAILURE OF SUBGRADE

Aimed at the seismic response and damage of fill subgrade，a large-scale shaking table model test of subgrade with the scale of 1：20 is introduced. The model subgrade is built by soil with a height of 1.93 m，length of 3.0 m and thickness of 1.4 m. A series of tests were performed with different kinds input seismic waves，amplitudes and frequencies. The dynamic responses of subgrade under earthquake，weak of portions，failure modes，as well as the influence of ground motion parameters are discussed. Results show that the subgrade has amplification effect to input seismic waves，and the effect become extremely prominent around the crest of the subgrade and the top of the retaining wall. The study also show that the top of the retaining wall and the crest of the subgrade are the vulnerable parts of subgrade and cracks normally appear near these parts under seismic motion. The amplification coefficients of the peak acceleration along subgrade slope surface decrease with the increasing earthquake amplitudes. The soil in subgrade has amplification effect to input seismic waves at high frequency and filtering effect at low frequency；and the filtering effect becomes more prominent with the increase of earthquake amplitudes. Lots of cracked locations are identified under gradually increased seismic. Vulnerable parts of the subgrade to earthquake loading and various factors that affect the earthquake-resistant behavior of the subgrade，such as the frequencies of waves，are discussed under seismic motions of different levels. The results are helpful to reveal the mechanism of subgrade damage under earthquake，and provide references for aseismic design of subgrade engineering.