基于离散单元法的石峁遗址东门城墙稳定性及加固方法研究

石峁遗址外城东门城墙出现了严重的外倾变形,面临倒塌风险,为对其进行科学保护,进行了城墙稳定性及加固方法的研究。提出风化折减系数表征灰缝的风化程度,利用离散单元法建立城墙模型,并验证其有效性,通过强度折减法研究在风化作用下城墙的变形及稳定性,通过反演分析法确定城墙的风化程度和灰缝的力学参数。研究结果表明:灰缝强度降低是城墙变形失稳的主要原因;在土压力作用下,城墙破坏呈滑移-倾覆模式;城墙目前处于欠稳定状态,风化系数为0.45~0.48,灰缝强度粘聚力和内摩擦角分别为21 kPa和14°。在此基础上,提出了灰缝灌浆和外侧支撑两种加固方法并进行了比选,最终加固取得了良好的效果。研究结果可为石峁城墙的后续的加固保护提供借鉴和参考。

Research on the stability and reinforcement method for the east gate wall of the Shimao site based on the discrete element method

The east gate wall of the outer city of the Shimao site has suffered from serious outward deformation and is facing the risk of collapse. In order to protect it scientifically, the stability and reinforcement methods for the wall were studied. The weathering reduction coefficient was proposed to characterize the degree of weathering of the mortar joint. The discrete element method was used to establish the wall model and verify its effectiveness. The deformation and stability of the wall under weathering were studied by the strength reduction method, and the weathering degree of the wall and the mechanical parameters of the mortar joint were determined by the inversion analysis method. The results show that the main cause of wall deformation and instability was the decrease of mortar joint strength. Under the action of earth pressure, the wall failure presented a slip-overturning mode. At present, the wall is in an understable state with the weathering coefficient of 0.45-0.48, mortar joint strength cohesion of 21 kPa and internal friction angle of 14°, respectively. On this basis, two reinforcement methods—grouting and lateral supporting—were proposed and compared, to finally obtain good results. The research results could provide a reference for the follow-up reinforcement and protection of the city wall of the Shimao site.