初始干密度对桂东南降雨型花岗岩残积土滑坡起动模式的影响

Effect of Initial Dry Density on Initiation Mode of Rainfall-Induced Granite Residual Soil Landslide,Southeastern Guangxi Province,China

桂东南花岗岩残积土滑坡灾害频发,严重威胁该地区居民生命财产安全,制约当地社会经济发展。明晰初始干密度对花岗岩残积土滑坡起动过程的影响是滑坡预警与防治的科学基础。通过开展人工土槽模型试验,观测花岗岩残积土滑坡起动过程的共性与差异,分析土体含水率和孔隙水压力的变化特征,最终探讨初始干密度对滑坡起动模式的影响。结果表明:(1)在降雨强度分别为60mm/h和90mm/h条件下,当初始干密度由1.20g/cm^3增至1.40g/cm^3时,滑坡起动时间分别延迟17min和13min,且起动模式由突然滑动型转变为渐进破坏型;(2)滑坡起动过程具有显著的共性,在降雨初期,雨水完全入渗至坡内,坡脚土体率先软化滑动;持续降雨导致坡面结皮现象发生,地表径流出现,低洼地带和冲沟形成;(3)初始干密度增加导致残积土抵抗雨水入渗能力增强,从而引起含水率和孔隙水压力响应时间延迟,孔隙水压力最大值和变化量减小。研究成果将为桂东南降雨型花岗岩残积土滑坡防治预警提供初步依据。

The granite residual soil slopes occur failures frequently in southeast Guangxi,China,posing threats to the local communities and impeding social-economic development.To understand the effect of initial dry density on the motivation of granite residual soil slope would provide scientific basis for landslide warning and prevention.In this study,it conducted artificial flume model tests to investigate the mechanism of granite residual soil slope failures.The similarities and differences in the initiation patterns of landslides in flumes were examined.And the changes of soil moisture content along with pore water pressures were analyzed.The effect of initial dry density on the initiation mode of the landslides was discussed.The results showed that:(1)Under the rainfall intensity of 60 mm/h and 90 mm/h respectively,when the initial dry density increased from 1.20 g/cm3 to 1.40 g/cm3,the initiation time of landslide was delayed by 17 min and 13 min;the initiation mode changed from a sudden sliding type to a progressive destruction type.(2)There were significant similarities in the patterns of slope failures.In the beginning of the artificial rain,slopes were infiltrated,following by the slope toe soil softened and slipped;An another pattern was that the continued rainfall led to a consolidated topsoil crust on slope surface,hillslope runoff,gullies and low-lying part of the slope.(3)The increase of initial dry density led to enhanced resistance of residual soil to rainwater infiltration,which led to the delay of response time of water content and pore water pressure,and the decrease of maximum and variation of pore water pressure.The research results will provide a preliminary basis for the prevention and early warning of rainfall-induced granite residual soil landslide in southeast Guangxi.