不同类型黄土场地地震诱发灾害分析

Analysis of seismic hazards by different types of loess sites

基于FLAC3D数值模拟方法,建立不同类型的黄土场地计算模型,研究地震动强度和频率对不同类型黄土场地的动力响应特征和变形规律,分析不同类型黄土场地地震动响应的差异性,揭示不同类型黄土场地诱发的地震灾害,结合理论分析验证数值模拟结果的可靠性。研究表明:黄土-泥岩接触型二元结构斜坡极易发生滑动破坏引起斜坡失稳,并且在坡肩位置引起较为明显的动力响应,加速度放大系数是坡顶的2倍左右,是一元结构黄土斜坡相同部位加速度放大系数的1.5倍左右;黄土斜坡临空面的存在会引起土体沿坡面发生一定范围的滑动和堆积,黄土塬内较塬边更为稳定,不易发生损伤破坏;低频地震波对平坦场地的地震响应影响明显,随着高程的增加,频带宽度增加,傅里叶谱幅值增加,坡肩处的幅值是坡脚的2倍左右;黄土斜坡场地易诱发大面积的滑坡灾害,黄土塬场地在剪切力和压张破坏条件下易诱发局部震陷灾害。

Based on FLAC3D numerical simulation method,different types of loess site calculation models were established,under different conditions of ground motion intensity and frequency,the dynamic response characteristics and deformation rules on different types of loess sites were studied,to reveal the seismic disasters induced by different types of loess sites,the reliability of numerical simulation results was verified by theoretical analysis.The results show that the sliding failure of the loess-mudstone contact type slope is easy,and the dynamic response is obvious at the slope shoulder.The acceleration amplification coefficient is about 2 times that of the top of the slope,the two-element structure is about 1.5 times the acceleration amplification factor of the same part of the loess slope.The existence of free surface of loess slope will cause the soil to slip and accumulate along the slope in a certain range,the loess tableland is more stable than the margin of the tableland,and it is less prone to damage and destruction.The low-frequency seismic wave has obvious influence on the seismic response of the flat site.The amplitude at the slope shoulder is about twice that at the slope toe.The loess slope site is easy to induce large scale landslide disaster,and the loess tableland site is easy to induce local earthquake subsidence disaster under the conditions of shear force and compression failure.