长江三峡水库区云阳县典型滑坡变形监测分析

采用2004年云阳县滑坡监测数据和降雨量资料,统计了滑坡与降雨的关系。并以杨柳磅滑坡、裂口山滑坡为例,对其深部位移、地表变形与降雨的关系进行了初步分析。云阳县位于三峡西段,为地质灾害多发区。该县每年5月进入雨季,降雨次数增多,降雨强度加大。2004年暴雨有9次,每次都使滑坡出现了异常。特别是6月和9月暴雨,造成了地表较大的宏观变形。变形出现最多的月份与暴雨出现频次最多的月份相一致。随着降雨强度加大,滑坡数明显增多。研究表明当降雨量大于10mm以上时,就有滑坡出现裂缝、错台及深部位移;当降雨量在50mm以上时,滑坡异常的情况增多,甚至出现土流;平缓的地层在暴雨后易形成极大的孔隙水压力而导致滑坡活动;同时,由于页岩、泥岩遇水后易泥化、软化,产生了顺层滑动;大暴雨后,丰富的地表水渗入地下,突然增大的地下水使结构松散的堆积体含水量增加、岩土强度指标降低,造成了局部变形。由于受地理环境等多方面因素的影响,滑坡体的规模与降雨强度大小没有明显的规律。根据宏观地质调查和钻探资料,裂口山滑坡、杨柳磅滑坡上部地层有超过15m厚的粉质粘土夹块石,下部地层有碎裂砂岩和泥岩。在降雨较大的情况下,水通过裂隙进入,使泥岩、粘土层变软,容易失稳。

Analysis on the Deformation of typical landslides at Yunyang County in the Three Gorges Reservoir region based on monitoring data

The study aims to analyze the correlation between landslides and rainfall by collecting of landslide monitoring data and annual rainfall data at Yunyang in 2004.Taking Yangliubang landslide and Liekoushan landslide as examples,the study further analyzed the correlation between deep displacement,ground deformation and rainfall.Located in the western part of Three Gorges Reservoir, Yunyang is a county with many geological hazards.As it enters into the rainy season in May,both the frequency and the amount of rainfall will increase.There were 9 heavy storms last year,each of them had resulted in the abnormality of landslides,especially the storms in June and August which caused huge and noticeable ground deformation.The months in which deformation appears most frequently correspond with those of storms.With the growing amount of rain,the number of landslides increases.It is found that when the amount of rainfall is greater than 10mm,there will be cracks in landslides,malposition of platforms and deep displacement;when the amount of rainfall is greater than 50mm,there will be an increase in the abnormal condition of landslides and even occurs mudflow.It is also found that after rainstorm,gently-sloped strata easily produce in small openings extremely great water pressure which results in the abnormality of landslides.Meanwhile,because there is a muddy and softening tendency happening in shale and mudstone when meeting water,slide of strata is produced.After heavy rainstorm,a large amount of surface water permeate the ground,and the sudden increase in the amount of ground water causes the corresponding increase in the amount of water in loose accumulative rock and decrease in the intensity of mudstones.Thus deformation occurs in some areas.However,as the result of the influence of various factors,such as geographical conditions,there is no significant correlation between the scale of landslides and the amount of rain.According to macrogeological survey and previous drilling data,Liekoushan and Yangliupang landslides,under which are layers of clastic sandstone and mudstone,are covered with over 15m thick layers of powdery clay and gravel.After the heavy rainfall,rain water permeates the layer of mudstone and clay through cracks and causes it to become softened.As the result of this,the layer will lose its stability.