南京市浦口区某山前缓坡滑坡复活机制再分析

Analysis on the reactivation mechanism of a piedmont gentle slope landslide in Pukou district,Nanjing

南京猪头山滑坡属于典型的覆盖层滑坡,2003年5月边坡发生缓慢变形失稳,没有对周围造成很大的危害,故未引起足够重视,2016年6~7月间受强降雨的影响再次发生大规模的滑动。研究发现,该滑体的地层具有特殊地质结构,在强降雨条件下会产生暂时性承压水,在其承压水的渗透力及浮托力作用下,其稳定性将会大大下降,因此该滑坡的再滑动与降雨密切相关。本文运用数值模拟方法分析了滑坡变形过程与降雨时长及降雨强度之间的关系,结果表明猪头山山前缓坡的稳定性随降雨时长和降雨强度增大逐渐降低,且具有一定的突变性,其滑坡面的位置位于坡体填土层的下部,较好地揭示了猪头山降雨型滑坡形成的机理以及滑坡再滑动机制。这一研究为所在地区的降雨性滑坡预报和治理提供了科学依据。

Objectives:In recent years,with the frequent occurrence of extreme climates,rainfall has continued to increase.From June to July 2016,Nanjing experienced historical continuous rainfall.The number of rainy days reached 15 days,the longest in history.Long-term rainfall has caused frequent landslide geological disasters.Zhutou Hill landslide in Nanjing is a typical overburden landslide.The slow deformation and instability of the slope in May 2003 did not attract enough attention,because no much harm was done to the surrounding area.The largescale landslide occurred again in June and July 2016 due to the heavy rainfall.It is found that the stratum of the landslide body is specially geologically structured.The temporary confined water,produced under the condition of heavy rainfall would greatly reduce its stability under the action of the osmotic and floating force.Therefore,the resliding of the landslide is closely related to rainfall.Methods:In this thesis,the relationship between the deformation process of landslide and the duration and intensity of rainfall is analyzed with numerical simulation.This paper draws a comprehensive engineering geological profile of Zhutou Hill slope in Nanjing.Combined with the rainfall situation in Nanjing from June to July 2016,the slide software was used to analyze the Zhutou Hill landslide mechanism.In this paper,the limit equilibrium method is used to calculate the slope stability.This paper simulates the slope stability under different rainfall conditions.Results:The results show that when the number of rain days is less than 2 days,the slope stability coefficient shows a slight increase or unchanged first,and when the rainfall is greater than 2 days and the rainfall is large(more than 25 mm/d),the slope stability drops significantly,diving As the water level rises,seepage force is generated,and temporarily confined water appears in the gravel layer,which generates floating support force,which greatly reduces the stability of the gentle slope and causes instability and damage.The results show that the stability of Zhutou Hill gentle slope gradually decreases with the duration and intensity of rainfall with a certain degree of mutation.The landslide surface is located in the lower part of the fill soil,which reveals the formation mechanism of Zhutoushan Hill rainfall-induced landslide and the re-sliding mechanism.Conclusions:The re-sliding of the Zhutou Hill landslide in Nanjing is caused by rainfall,which is a typical rainfall-type landslide.The Zhutou Hill landslide has the characteristics of gentle slope,poor stability and obvious influence by rainfall.It is calculated by numerical simulation that short-term heavy rainfall has little effect on the slope stability of Zhutou Hill.Continuous rains are more likely to cause slope instability.The results provide a scientific evidence for the prediction and control of rain-induced landslides in the region.