【作者】 胡光海；

【导师】 刘振夏；

【作者基本信息】 中国海洋大学 ， 海洋地质， 2010， 博士

【摘要】 海底滑坡广泛发育于海底陆坡上,是改变海底地形地貌的主导因素,也是大陆坡上沉积物往深海盆地搬运的重要方式。突发大规模的海底滑坡事件可能造成海啸,给沿海地区居民的生命和财产带来巨大损失。因此近几十年来许多学者开始研究海底滑坡分布、物质来源、形成机制以及演化模式,为人类的防灾减灾提供科学依据。东海海域是被动型大陆边缘,具有较陡的大陆坡,海底构造复杂,东海大陆边缘发育大量的海底滑坡。然而,由于过去缺乏高精度、高分辨率的多波束水深数据资料,因此,在东海陆坡海域尚未系统的对海底滑坡作基本形态特征分析与机理探讨。已有的研究表明,海底滑坡在地形上出现下列特征：在坡度剧烈变化处,有弧形主陡坎,沿着主要陡坎的两侧向下延伸则会出现近平行的侧壁；或者在海底峡谷侧壁和在较顺直的海底斜坡上突然出现圈椅状的陡坎或陡壁。本研究基于海底滑坡的地形特征,使用目前较高精度的多波束水深地形资料,利用专业的商用软件CARIS HIPS把离散的多波束水深数据进行网格化,构建高分辨率的海底数字地形模型,绘制海底地形三维立体图和坡度图,以海底滑坡所呈现出的地形特征来识别其发生的位置。识别出海底滑坡后,量测和计算滑坡坡度、主要陡坎高度、滑坡发生的水深、滑坡面积与体积等。识别结果显示,在东海中部陆坡共有102处海底滑坡,面积大小由0.06km2至15.51km2不等；体积大小介于0.001km3和1.942km3之间。估计还有许多地貌形态特征不显著和规模较小滑坡未被计算在内体积最大的滑坡位于已发现海底泥火山附近,海底滑坡的规模可能和泥火山发育有相关性。根据统计可知,大部分海底滑坡发生在局部坡度小于20°、水深在200m～1200m的海底；海底局部坡度与海底滑坡的规模具有较好的正相关性；海底滑坡搬运的土层厚度平均为26m。根据前人研究经验,作为海底滑坡分类参数的H/L值表明研究区海底滑坡发育崩塌型、旋转型和平移型滑坡,而缺少流动型滑坡。崩塌型和旋转型滑坡主要分布在海底峡谷谷壁及其附近海底；而平移型滑坡主要分布在开阔的非海底峡谷陆坡区。通过3个非饱和土模型的土工离心模拟试验表明,研究区海底滑坡区附近发育的泥火山,是海底斜坡失稳过程中孔隙气和孔隙水在压力差作用下,自海底下向上逸出而形成的。土体含气通过影响土体的密度来影响土体的抗剪强度,而对孔压随重力加速变化的斜率影响不明显。通过Slope/W软件进行斜坡稳定性分析表明,研究区海底斜坡上末次冰期以后形成的沉积层在地震烈度7度下可能会发生斜坡失稳现象,在地震烈度6度下局部坡度超过3.1°海底斜坡沉积物可能会发生失稳滑坡,在静压力下,斜坡不会发生失稳现象。本论文主要创新点：1、利用高精度多波束资料对东海中部陆坡的海底滑坡进行系统识别和特征研究,并进行初步分类；2、针对研究区土体含气的情况,采用厌氧发酵法制备含气非饱和土,利用土工离心模拟试验进行斜坡失稳模拟研究。更多还原

【Abstract】 Submarine landslide that widely occurs on the continental slope is one of the major forces which affect the morphology of continental margin, and one of the major mechanisms of sediment transport from the shallow water to the deep basin. Sudden large-scale submarine landslide may trigger tsunami, causing huge losses in property and human life of coastal residents. Therefore, it is important to investigate the distribution, source, mechanisms and evolution model of submarine landslides.East China Sea is a passive continental margin, characterized by rifted, rotated fault blocks and steeper continental slope. Thus, the geological condition is suitable for the development of submarine landslide. However, in the past years, due to lack of high resolution multi-beam bathymetric data, submarine landslides alone the continental slope of the East China Sea have not yet been synthetically studied on its characteristics and mechanism.Typical geomorphologic features of submarine landslide consist of an arcuate headscarp, two sub-parallel sidewalls and sometimes with slumped material appear at the base of the landslide scar. This study is based on seafloor morphology derived from the multi-beam bathymetric data. The discreet multi-beam data are incorporated in the CARIS Hydrographic Information Processing (HIPS) software packages and gridded. Then high resolution digital terrain models are constructed, slope maps and artificial hill-shade images created are used to identify the location of submarine landslides. After the Identification of submarine landslide, various aspects of the failures/fractures, including landslide area, run-out distance, the head-scarp height and slope, and adjacent local un-failed slope gradient, are measured and the relationships statistically analyzed. morphometric statistics give us useful insight into submarine landslides.Based on our investigation, the total number of submarine landslides identified is 102, and the area of the identified landslides ranges from 0.06km2 to 15.51km2, and the volume of the landslide is between 0.001km3 and 1.942km3, and averages 0.165km3. The largest landslide is approximately connected with the reported mud volcanoes.Most landslides occur on the local slopes less than 20°, with the depth of 200m～1200m. There is a high correlation between slope gradient and area. And the thickness of sliding layer is approximately 26m for each landslide. According to previous research experience, submarine landslides could be categorized by the H/L value. The statistic data show that most frequently observed submarine landslide belong to slump, rotational slide and translational slide and that there is a lack of flow slide in the study area. Most slumps and rotational slides are present on the submarine canyon system, and most translational slides are observed on the open continental slope.Three centrifuge modelling experiments of unsaturated soils show that the formation of mud volcano near the submarine landslides is facilitated by the process that the pore gas and water escape under the pressure difference while submarine slope is under instability. The gas in the soil could have effect on the soil strength by affecting its density, and have no significant effect on the rate of the water pore pressure change with the increase of the gravity acceleration.By using Slope/W software, the result of slope stability analysis shows that the sediments deposited in the study area after the last glacial period are under instability in the seismic intensity of 7 degrees, or in the seismic intensity 6 degrees with slope more than 3.1°.but the slope is stable under the self gravityThe main innovations in this dissertation include:(1) Submarine landslides in the continental slope area between 27°N and 30°N are identified, statistically analyzed and preliminarily categorized, based on seafloor morphology derived from multi-beam bathymetric data. (2) Considering the gas content in the soil, the slope stability is analyzed and simulated in the centrifuge model test of submarine unsaturated soil slope with soil samples preparation under the anaerobic condition.更多还原