金沙江上游苏洼龙滑坡形成机制与稳定性研究

发布时间：2018-08-02 14:08

【摘要】：苏洼龙滑坡位于金沙江上游巴塘-中咱一带,地处构造活动十分强烈的青藏高原东南缘的高山峡谷区,地震活动频繁且强度大,地质环境相当复杂。研究区内沿金沙江河谷发育有大量古滑坡,对古滑坡的形成机制、稳定性及其发展趋势进行研究,为本地区重大工程的规划选址提供科学依据。本文以金沙江上游苏洼龙滑坡为例,根据野外地质调查、实地测量,结合室内实验及前人研究成果,对苏洼龙滑坡及其周边湖相沉积物的空间分布和形成年代、滑坡的成因机制以及破坏特征进行了初步的研究；然后基于FLAC3D软件运用数值模拟分析手段对苏洼龙滑坡残留堆积体在自然工况、暴雨工况和地震工况等三种工况下的稳定性做出了评价,得出以下结论：(1)苏洼龙滑坡为大型岩质古滑坡,滑坡发生后即堰塞金沙江并到达对岸,形成了堰塞湖。利用’4C测年和光释光(OSL)测年方法确定了苏洼龙古滑坡及其周围一带堰塞湖湖相沉积物的形成年代,结果表明：苏洼龙滑坡堵江事件发生的时间是在1355 BP左右,其周边发育的两级湖相沉积物平台形成的时代分别为1.8 ka BP和1.3 ka BP。(2)堰塞湖湖相沉积物中发现的两种软沉积物变形(液化卷曲构造和球枕构造),揭示了该区在1115BP左右,至少发生了一次震级不小于5级的古地震；推测导致苏洼龙滑坡发生的原因可能是地震或者是地震和降雨的联合作用。(3)苏洼龙滑坡坝的湖相沉积特征及年代学表明了金沙江上游王大龙大型滑坡群具有多期次的特点,即它们可能是多次古地震诱发形成的。自1900 BP以来,该区受雄松-苏洼龙活动断裂的影响,曾发生过至少多次古地震(1900 BP, 1355 BP,1115 BP),表明该区活动断裂自全新世晚期以来一直是十分活跃的。(4)强烈的地质动力作用和存在有利结构面是苏洼龙滑坡形成的重要条件。推测滑坡变形破坏过程如下：后缘形成拉裂缝—震裂裂缝加深和拉长—坡体前缘剪切破坏—山体震裂松动—滑面形成—快速滑动—堰塞金沙江。(5)基于FLAC3D软件,对滑坡的稳定性进行模拟计算,结果显示滑坡在自然工况和暴雨工况下是稳定的,但在本文给定的地震动力作用下发生失稳破坏。
[Abstract]:The Suwulong landslide is located in the upper reaches of the Jinsha River from Batang-Zhongzan. It is located in the alpine canyon area of the southeast margin of the Qinghai-Tibet Plateau, where the tectonic activity is very strong. The seismic activity is frequent and the intensity is high, and the geological environment is quite complex. There are a large number of ancient landslides developed along the Jinsha River valley in the study area. The formation mechanism, stability and development trend of the ancient landslides are studied, which provides scientific basis for the planning and location selection of the major projects in this area. Taking the Suwulong landslide in the upper reaches of Jinsha River as an example, according to the field geological survey, field survey, laboratory experiments and previous research results, the spatial distribution and formation age of the Suwulong landslide and its surrounding lacustrine sediments are studied. The cause mechanism and failure characteristics of landslide are studied preliminarily, and then the residual accumulation of landslide in Suwulong is analyzed by numerical simulation based on FLAC3D software. The stability of the landslide is evaluated under the conditions of rainstorm and earthquake, and the following conclusions are drawn: (1) Suwulong landslide is a large ancient rock landslide. After the landslide occurs, the Weir River reaches the opposite bank and forms a barrier lake. The formation age of the sediments of the ancient landslide in Suwulong and its surrounding areas of the barrier lake is determined by using the dating method of Yao4C and (OSL). The results show that the time of the event of blocking the river in the landslide of Suwulong is about 1355 BP. The formation times of the two-stage lacustrine sediment platform are 1.8 ka BP and 1.3 ka BP. (2, respectively. Two types of soft sediment deformation (liquefaction convoluted structure and ball pillow structure) found in the lake sediments revealed that the area is around 1115BP. At least one paleo-earthquake of magnitude not less than 5 occurred; It is speculated that the occurrence of Suwulong landslide may be caused by earthquake or the combined action of earthquake and rainfall. (3) the lacustrine sedimentary characteristics and chronology of Suwulong landslide dam indicate that the large landslide group of Wang Dalong in the upper reaches of Jinsha River has the characteristics of multiple periods. That is, they may have been induced by multiple paleoearthquakes. Since 1900 BP, the area has been affected by the Xiongsong-Suwulong active fault. At least a number of paleoearthquakes (1900 BP, 1355 BP ~ 1115 BP),) have shown that the active faults in this area have been active since the late Holocene. (4) strong geodynamic action and the existence of favorable structural surface are the important conditions for the formation of Suhualong landslide. It is inferred that the process of deformation and failure of landslide is as follows: the forming of tension fissure, the deepening of seismic crack and the elongated shear failure of front edge of slope body, the formation of earthquake crack loosening of mountain body, the formation of sliding surface, the rapid sliding of Weir plug Jinshajiang River. (5) based on FLAC3D software, The stability of the landslide is simulated and calculated. The results show that the landslide is stable under the natural condition and the rainstorm condition, but the instability and failure occur under the earthquake dynamic action given in this paper.
【学位授予单位】：中国地质大学(北京)
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：P642.22

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