积石山M6.2地震诱发秦阴村黄土震陷灾害研究

Characteristics of the loess seismic subsidence in Qinyin Village,Shiyuan Town,induced by the Jishishan M 6.2 earthquake

2023年12月18日在甘肃省临夏州积石山县发生的M6.2地震诱发了多处黄土震陷灾害。通过对积石山县石塬镇秦阴村黄土震陷灾害进行现场调查,得出灾害的主要特征;利用原状黄土开展室内试验,研究秦阴村黄土的物性参数特征、微结构特征和震陷性,结合现场调查结果分析震陷灾害产生的主要原因。研究结果表明:秦阴村震陷区内土体酥裂,裂缝发育,边缘土体坍落或产生滑坡;土层呈反倾台阶状震裂破坏,最大沉降量57 cm,裂缝最大长度约300 m,宽度约83 cm。震陷区黄土土质疏松、含水率较高、架空孔隙发育、颗粒胶结较弱,具备产生震陷的土性条件。震陷区黄土层厚度较大,地震的等效动应力大于土体产生震陷的临界动应力,且地震动持续时间较长、卓越周期较大,使得场地产生了严重的震陷破坏。

The Jishishan earthquake of magnitude 6.2 on December 18,2023,caused numerous loess seismic subsidence disasters.Field investigations in Qinyin Village,Shiyuan Town,Jishishan County,revealed the characteristics of these subsidence events.Using a series of laboratory tests,microstructure,the physical parameters,microstructure,and seismic subsidence properties of the loess in Qinyin Village were studied.The main causes of these subsidence disasters were also analyzed based on field survey results.Results show that the loess in the seismic subsidence area of Qinyin Village is characterized by flakiness and cracking.Ground fractures are developed,and collapses,and slides are prevalent at the edges of loess ridges.The seismic damaged strata exhibit a reverse-stepped fracture pattern,with maximum settlement reaching approximately 57 cm.The maximum crack measured approximately 300 m in length and 83 cm in width.The loess in the seismic subsidence area is loose and has a high moisture content,with well-developed micro-trellis pores and weak particle cementation.These conditions make the soil susceptible to seismic subsidence.The loess layer in the seismic subsidence area is notably thick.The equivalent dynamic stress from the earthquake exceeded the critical dynamic stress required for loess subsidence.Furthermore,the duration and predominant period of the ground motion were large,significantly contributing to the ground motion's duration,and the predominant period contributed significantly to the damage.