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扎木弄沟2000年特大滑坡型泥石流动力学过程及其趋势分析
Alternative TitleThe dynamic process of catactrophic Landslide Triggered Debris Flow (LTDF) on April 9th, 2000 and tendency analysis of debris flow in Zhamunong gully
李俊
Subtype博士
Thesis Advisor陈宁生
2017
Degree Grantor中国科学院大学
Place of Conferral北京
Degree Discipline岩土工程
Keyword滑坡型泥石流 扎木弄沟 动力学过程 内外动力条件 地表振动波谱
Abstract泥石流发展趋势是地质、水文和气象工程界热门的研究课题之一。历史资料显示,100多年来西藏帕隆藏布流域特大规模泥石流总是发生于扎木弄沟、古乡沟和培龙沟,其中以扎木弄沟泥石流规模最大,1902年和2000年易贡扎木弄沟泥石流的规模总量高达8×108m3。第四纪以来在印度板块俯冲和碰撞欧亚板块作用下,帕隆藏布流域发育大量的错落体和崩滑体。但100多年来该流域内特大规模泥石流为何总是发生于这三条泥石流沟?这三条沟的特大规模泥石流动力学过程是怎样的?帕隆藏布流域特大规模泥石流发展趋势如何?这些科学问题备受泥石流领域关注。在2000年扎木弄沟滑坡型泥石流动力学过程研究的基础上,本文分析扎木弄沟泥石流发展趋势,这有助于进一步认识帕隆藏布流域特大泥石流发展趋势,也有助于认识扎木弄沟今后再次发生特大滑坡型泥石流的动力学过程及暴发规模。作者在国家基金委和长江岩土工程总公司(武汉)的资助下,首先利用高精度遥感解译,现场调查2000年扎木弄沟滑坡型泥石流的基本情况。其次通过大比例尺工程地质测绘、物探和取芯钻探等手段对2000年扎木弄沟滑坡型泥石流边界形态和形成、运动和堆积特征进行深入解剖。再次采用地表振动波谱解译、统计分析、理论分析和数值模拟等方法,对2000年滑坡型泥石流的地质环境背景、驱动因素及动力学过程进行深入的研究。通过钻孔资料分析,光释光测年和实地观测等手段,揭示长时间尺度下扎木弄沟特大规模泥石流的发展趋势。最后,结合目前扎木弄沟的物源和2000年滑坡型泥石流的动力学过程,分析扎木弄沟特大滑坡型泥石流的发展趋势。本文取得的主要成果如下:(1) 2000年滑坡型泥石流的发生时间为2000年4月9日20:00:11.95。滑坡型泥石流的容重为2.0t/m3,滑坡型泥石流发生过程中崩滑体的启动速度为89.89m/s,滑坡型泥石流平均流速为30.12m/s,滑坡型泥石流在出山口处的流速为48.7m/s,泥石流流量过程呈现出一个总体上凸,但存在激烈振动的过程,泥石流流量最高可达504×104m3/s以上,出现于第二处撞击点。(2) 2000年4月9日扎木弄沟滑坡型泥石流是区域地质构造演化的结果,极端的地震活动和冻融循环和干湿循环是2000年滑坡型泥石流的激发因素,其中灾前Ms4.8的地震是2000年滑坡型泥石流发生的直接诱发因素。2000年4月9日易贡扎木弄沟滑坡型泥石流是区域地质构造演化的结果。受垂直于右旋平移断层的方向上若干横向断裂控制,扎木弄沟所在区域为地垒段,扎木弄沟易发生滑坡型泥石流。受强烈的新构造运动隆升和河谷快速侵蚀影响,扎木弄沟源头豆腐块式的坡体及其出露的高达数百米的高陡临空面是特大滑坡型泥石流发育的地质基础,河谷深切形成纵比降大的沟谷地貌更加有利于特大滑坡型泥石流的形成。地震活动和冻融循环和干湿循环与滑坡型泥石流的发生具有时空上的耦合关系。扎木弄沟长期强烈的冻融循环使得流域源头的花岗岩岩体强度降低,裂隙增多,孔隙增大。2000年3月至4月9日扎木弄沟经历一个以中旱和中小雨为背景的小量级的干湿循环过程,此时受冻融循环和干湿循环作用破裂的BH01崩滑体处于饱水工况。BH01崩滑体失稳过程于4月9日晚上8时零分11.95秒发生,而在4月9日晚上8点整9.2秒,距扎木弄沟约13km,发生4.8级地震,流域顶部岩土体获得的地震加速度达43.3gal。在此次Ms4.8级的地震诱发作用下,BH01崩滑体发生崩滑。(3) 基于林芝地震台站记录的2000年滑坡型泥石流地表振动波谱,该次滑坡型泥石流的动力学过程可分为四个过程,分别为BH01崩滑区节理裂隙发育过程,裂隙贯通崩滑过程,滑坡转化为泥石流过程和泥石流运动堆积过程。其中后三段动力学过程具有明显的地表振动特征。BH01崩滑区裂隙贯通滑动过程中,滑坡型泥石流呈现振幅大频率高的特征。滑坡转化为泥石流过程中,泥石流能量增加,波的振幅较大,最大振幅64cm,出现于B点,该点频率也最高,为2.1hz。泥石流运动过程中B-C段,由于扎木弄沟沟道较为狭窄且弯道较多,泥石流在弯道处撞击到山体,产生地面振动,波的振幅较大,频率较高,最大振幅为42.64cm,频率为2.0hz。D-E段沟道弯度较大,且泥石流发生弯道超高现象,产生的地表振动比B-D段地表振动更为强烈,波的振幅相对增加,最大振幅为50cm,但地表振动的频率降低,降低为1.4hz。泥石流冲出出山口,沟道与地面坡度较小,泥石流开始堆积,泥石流对地面的撞击减弱,波的振幅减小,频率降低,最大振幅30cm,频率为1.0hz。(4) BH01崩滑区节理裂隙发育过程中,节理裂隙控制着BH01崩滑体的边界与规模,长期的冻融循环和灾前的干湿循环使得BH01崩滑岩体处于饱水工况。扎木弄沟河水的颜色变化说明BH01崩滑体底床的边界(两组主滑动面和后缘陡倾裂隙)已经贯通,雨水和雪水已经渗透到崩滑体底床。(5) 通过崩滑体“蠕滑-拉裂-剪断”失稳破坏模式揭示2000年滑坡型泥石流的裂隙贯通崩滑过程。渗透到BH01崩滑体陡倾裂隙中的降水和冰雪融水给之以高孔隙水压作用,在高孔隙水压的作用下BH01崩滑体受到一个朝向坡外的推动作用,加之水流渗入崩滑体后,在BH01崩滑体切割面上产生的巨大推力和两组主滑面上所产生的浮托力及水对结构面物质的软化导致BH01崩滑体主滑动面上残存的锁固段临近剪断,4.8级地震活动使得最后的455m的锁固段破裂导致BH01崩滑体彻底失稳滑动。(6) 钻孔zzk1和zzk2显示扎木弄沟沟口堆积物可分为五层,从下至上分别为古老泥石流和河流的混杂堆积物、河流相堆积物、37.4±3.1ka特大型泥石流堆积物、37.4±3.1ka-1902年之间泥石流和河流的混杂堆积物、2000年滑坡型泥石流堆积物。(7) 长时间尺度下扎木弄沟泥石流规模呈波动变化过程,特大型泥石流规模随时间先增加后减小,且在特大型泥石流发生后的数十年间,汇流型泥石流规模和频率也逐渐减小。今后扎木弄沟存在发生特大滑坡型泥石流的可能性。经历一定时间的累积(有可能是百年尺度)扎木弄沟滑坡型泥石流易发生,特大滑坡型泥石流灾害发生后,灾害还将延续一段时间,汇流型泥石流规模呈逐年减小趋势。扎木弄沟BH01-1和BH02潜在崩滑体是今后特大滑坡型泥石流的主要物源,其方量分别为0.92×108m3和0.94×108m3。在地震(地震烈度为Ⅷ度)和极端气候工况下,百年内再次发生的滑坡型泥石流规模可能小于4.46×108m3,起动规模千万方级别的滑坡型泥石流都会造成堵河。当堰塞湖水位快速升高时,堰塞坝的结构强度大幅度减小,堰塞坝溃决的风险有可能逐渐增大。
Other AbstractThe trend of debris flow is one of the major topics in the field of geology, hydrology and meteorology. According to historical data of more than one hundred years, large-scale debris flows always occurred in the gully of Zhamunon, Guxiang, Peilong and Tianmo in Parlung Zangbo basin. Under the India plate driven and collided on the Eurasian plate, lots of landslides existed in Parlung Zangbo basin since from Quaternary Period. However, why large-scale debris flows always happen in the three gullies mentioned earlier? How the internal and external dynamic factors affect the occurrence of the large scale debris flow of the three gullies? What are dynamics processes of large-scale debris flows in the three gullies? How the trends of future large-scale debris flows are in the three gullies? Those scientific issues attracted many scientists attention. The research object is landslide triggered debris flow of Zhamunong gully. This thesis analysis the trend of large-scale debris flow in Zhamunong gully based on the dynamic process of Landslide Triggered Debris Flow on 9th April, 2000 (2000 LTDF). The study purpose is help to understand the trends of large-scale debris flows in other three gullies. Firstly, the basic data of 2000 LTDF was investigated by field and high resolution remote sensing methods, this work is supported by National Natural Science Foundation of China and Changjiang Geotechnical Engineering Corporation. Secondly, I analysis the shapes and dynamic characteristics of 2000 LTDF based on the large scale engineering geological mapping, geophysical prospecting and drilling. Thirdly, the geological environment background, triggering factors and dynamic process of 2000 LTDF were study based on some methods which are statistical analysis, spectral interpretation, theoretical analysis and numerical simulation. Fourthly, the magnitude tendency of debris flow was reveal by Borehole data analysis, Optical Stimulated Luminescence (OSL) and field observation under long time scale scale in Zhamunong gully. Finally, based on the materials at present and dynamic process of 2000 LTDF, I analyze the tendency of large-scale landslide triggered debris flow in Zhamunong gully. The main achievements of this thesis are as follows:(1) The accurate occurrence time of 2000 LTDF is 20:00:11.95. The density of 2000 LTDF is 2.0t/m3, the starting velocity of 2000 LTDF is 89.89m/s, the average velocity of 2000 LTDF is 30.12m/s, the 2000 LTDF velocity is 48.7m/s in the mountain-pass section, and the discharge process of 2000 LTDF increase first and then decrease. The maximum discharge of 2000 LTDF is 504×104m3/s which occurs at second impact section.(2) The occurrence of 2000 LTDF was the result of regional geological tectonic evolution. The motivate factors of 2000 LTDF were long-term freeze-thaw cycle and dry-wet cycle and earthquake. Earthquake of Ms 4.8 is the direct inducing factor of 2000 LTDF.The occurrence of 2000 LTDF was the result of regional geological tectonic evolution. Controling a number of transverse faults in the direction perpendicular to the dextral slip fault, Zhamunong gully get the relative rising horst, in which LTDF is prone to exist. The geological bases of LTDF were fragmentized slope and it’s hundreds of meters high steep surface in the source of Zhamunong gully. Valley landform with gradient high is more favorable to the formation of the LTDF.There is a coupling relation between the occurrence of 2000 LTDF and earthquake and freeze-thaw cycle and dry-wet cycle. The strength of granite rock is decreased, the fissures are increased, and the pores are enlarged in the source of Zhamunong gully. From March to April 9th, 2000, a small scale dry-wet cycle was experience by Zhamunong gully. At this time, the BH01 landslide is saturated under the freeze-thaw cycle and dry-wet cycle. The BH01 landslide was slide at 8 pm 11.95 seconds on 9th April, 2000. An earthquake of Ms 4.8 occurs from Zhamunong gully about 13km on 8 pm 9.2 seconds on 9th April, 2000, the top rock and soil of Zhamunong gully obtained 43.3gal of seismic acceleration. Under the influence of the Ms 4.8 earthquake, the BH01 landslide was occurred.(3) The dynamic processes of 2000 LTDF have four processes based on the ground vibration spectrum recorded by Linzhi seismic station. The four processes contain joint and crack development process in BH01 landslide, crack fracture and sliding process, landslide translate into debris flow, movement and deposition of debris flow. The dynamic processes of the latter three segments have obvious characteristics of surface vibration.Characteristics of large amplitude and high frequency were revealed in crack fracture and sliding process of BH01 landslide. The debris flow energy increase and the amplitude are large and the maximum amplitude of B section is 64 cm in dynamic process of landslide translate into debris flow. Because debris flow hit the mountain at the bend, the amplitude and frequency are high in the dynamic process B-C of debris flow movement, the maximum amplitude is 42.64 cm, and the frequency is 2.0 Hz. Because the bending of channel is large in dynamic process D-E of debris flow movement, the amplitude of the wave is increasing, the maximum amplitude is 50cm, but the frequency is reduced to 1.4 Hz. The debris flow was deposited gradually and the impact of debris flow on the ground was weakening gradually after mountain-pass section. Therefore, the amplitude of the wave decreases to 30cm and the frequency decreases to 1.0 Hz respectively in the dynamic process of debris flow deposition.(4) The boundary and scale of BH01 landslide are controlled by joints. BH01 landslide is saturated under the long term freezing and thawing cycles, drying and watering cycle before disaster. The boundaries of the bottom bed of BH01 landslide (the two main sliding surfaces and the steep fractures of trailing edge have been basically connected. The melted snow water and rainwater has completely penetrated into the bottom of the BH01 landslide. The crack fracture and sliding process of 2000 LTDF was revealed by the landslide failure mode of ‘creep, fracture and shear’. The high pore water pressure that comes from rainwater and melts water was impacted on the BH01 landslide.(5) The BH01 landslide is driven by a force toward the slope under the action of high pore water pressure. The residual locking section on the structure surface of BH01 landslide was close shear off by huge thrust force and uplift force and the softening of water causes on the main sliding surface. The final lock section of 455m was eventually ruptured by the Ms 4.8 earthquake, and then the BH01 landslide was slide.(6) Borehole zzk1 and zzk2 show that depositions can be divided into five layers in the mouth of Zhamunong gully. From bottom layer to top layer, there are the ancient debris flow deposition, fluvial deposition, large-scale debris flow deposits of 37.4+3.1ka, mixed deposits of debris flow and river from 37.4+3.1ka to 1902, the deposition of 2000 LTDF.(7) The process of debris flow magnitude is fluctuating under long time scale in Zhamunong gully, the magnitude of large-scale debris flows were firstly increased then decreased, and magnitude and frequency of smaller debris flow were decreased in the decades after the occurrence of the large-scale debris flows.(8) Large-scale landslide triggered debris flow of Zhamunong gully may occur in the future. The smaller debris flow after the landslide triggered debris flow disaster will decrease year by year. Potential landslide named BH01-1 and BH02 are the major materials of future landslide triggered debris flow in Zhamunong gully. The volumes of BH01-1 and BH02 are 0.92×108m3 and 0.94×108m3 respectively. The magnitude of landslide triggered debris flow maybe less than 4.46×108m3 impacted by the earthquake (seismic intensity is eight degree) and extreme climate within one hundred years. Landslide triggered debris flow will block river which volume more than ten million. When the water level of dammed lake rises rapidly, the structural strength of the dam is greatly reduced, and the risk of dam may increase gradually.
Pages152
Language中文
Document Type学位论文
Identifierhttp://ir.imde.ac.cn/handle/131551/24584
Collection山地灾害与地表过程重点实验室
Affiliation中国科学院成都山地灾害与环境研究所
First Author Affilication中国科学院水利部成都山地灾害与环境研究所
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李俊. 扎木弄沟2000年特大滑坡型泥石流动力学过程及其趋势分析[D]. 北京. 中国科学院大学,2017.
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