门源MS6.9地震诱发明长城山丹段破坏机理分析

2022年1月8日青海门源发生了M_S6.9地震，造成位于低烈度区的甘肃省山丹县境内明长城墙体局部坍塌。作为国家重点文物保护遗址，其坍塌墙体距离此次地震震中114 km,地面振动强度相对较弱，因而其地震破坏机理值得深入研究。地震后，对已坍塌长城墙体进行工程地质调查、病害调查，然后结合调查结果进行理论分析与数值模拟来研究坍塌墙体震害机理。结果表明：此段长城墙体掏蚀病害发育，墙体构造裂缝暴露，尚无保护措施；坍塌墙体临近国道和便道，环境振动效应明显；墙体南北两侧风化差异性明显，北侧墙体含水率较高，夯土强度较低；墙体既有病害加剧了地震惯性力的影响，导致低烈度区长城墙体发生局部坍塌。此次地震对甘肃河西地区明长城遗址保护具有警示意义，研究结果为后期明长城抗震保护提供一定的科学依据。

Damage mechanism along the Shandan section of the Ming Great Wallinduced by Menyuan MS6.9 earthquake

On January 8, 2022, an M_S6.9 earthquake occurred in Menyuan County, Qinghai Province. A local collapse of the Ming Dynasty Great Wall occurred in Shandan County, a low intensity area. As a key national heritage site, the collapsed wall was 114 km away from the epicenter, and was subjected to relatively weak ground vibration, thus its seismic failure mechanism deserves in-depth study. After the earthquake, an engineering geological investigation and disease survey were carried out on the collapsed walls, and then the theoretical analysis and numerical simulation were performed to study the seismic failure mechanism of the collapsed walls in combination with the survey results. The results reveal that: in the Shandan section of the Ming Great Wall, the wall erosion disease is developed, and the structural cracks with no protective measures are exposed. The collapsed wall is near the national road and the village road, hence the environmental vibration effect is apparent. The weathering difference between the north and south sides of the wall is manifest; the moisture of the north side is higher than the south side, thus the strength of the rammed-earth is lower. The existing diseases of the wall aggravate the effect of seismic inertia force, resulting in the local collapse of the Great Wall. The M_S6.9 earthquake has a warning significance for the protection of the Ming Dynasty Great Wall sites in the Hexi region of Gansu. The research results can provide a certain scientific basis for the seismic protection of the Ming Dynasty Great Wall in future.