考虑堆填界面软化及地下水位波动的大型弃渣场边坡稳定性分析

弃渣场是基础建设中的重要附属设施,近年来业界对弃渣场边坡稳定与安全十分关注.针对弃渣场长期运行中堆填界面软化和地下水位波动这2种典型致灾因子,本文在地质补勘、岩土试验和变形监测的基础上,采用强度折减有限元法模拟研究了一大型弃渣场的典型失稳机制和稳态演化规律.研究发现由于地表入渗的长期淋溶和地下水浸润作用,依附堆填界面产生黏粒充填现象和强度软化效应,从而诱发依附堆填界面的应变局部化,导致边坡潜在失稳模式的转变、松动区的扩大和边坡稳态的下降,弃渣场设计与运行过程中,应对堆填界面软化效应予以重视.对监测数据反映的雨季地下水位上浮2m的工况进行校核计算,以及地下水位进一步抬升条件下的边坡稳态模拟预测,表明在遭遇极端降雨事件或排水设施失效等恶劣工况下,该弃渣场具有安全储备不足的风险,因此需要加强地下水位监测和地下排水设施维护,保障弃渣场边坡的长期稳定与安全.本文提出的评价思路、方法和成果可供类似弃渣场边坡稳定性评价借鉴.

Slope Stability Analysis of Large Dump Yard Considering Sofening of Landfill Interface and Groundwater Level Fluctuation

The dump yard is an important ancillary facility in the infrastructure,and the industry is very concerned about the stability and safety of the slope of the dump yard.In view of the two typical hazard factors of softening of the landfill interface and the fluctuation of the groundwater level in the long-term working of the dump yard based on geological survey as well as geotechnical test and deformation monitoring,the typical instability mechanism and steady state evolution of a large dump yard were simulated by the method of strength reduction finite element.The study found that due to the long-term leaching of the surface and groundwater immersion,the landfill interface cause the phenomenon of clay accumulation and the strength softening effect,which induces the localization of the strain of the landfill interface and the transformation of the potential instable model of the slope and the expansion of the loose area and the decline of the slope stability.In the process of design and operation of the dump yard,the softening effect of the landfill interface should be paid attention.By the calculation of the condition of 2 m floating on the groundwater level during the rainy season reflected in the monitoring data and the slope stability simulation prediction under the condition of further lifting of the groundwater level,the dump yard is at risk of insufficient safety reserves in adverse conditions such as extreme rainfall events or failure of drainage facilities.Therefore it is necessary to strengthen the monitoring of the groundwater level and the maintenance of underground drainage facilities to ensure the long-term stability and safety of the slope of the dump yard.The evaluation ideas,methods and results put forward in this paper can be used for reference for the stability evaluation of slope of similar dump yards.