南海北部陆坡白云凹陷区海底滑坡的识别与特征分析

发布时间：2017-12-31 12:38

本文关键词：南海北部陆坡白云凹陷区海底滑坡的识别与特征分析　出处：《国家海洋局第一海洋研究所》2015年硕士论文　论文类型：学位论文

【摘要】：海底滑坡是陆坡区广泛发育的地质灾害类型之一,既是塑造海底地形地貌的主导因素,也是大陆坡上沉积物向深海盆地搬运的重要方式。我国南海北部陆坡区存在丰富的天然气水合物和油气资源,同时也是滑坡等地质灾害极为发育的区域。本文以南海北部陆坡白云凹陷为研究区,开展海底滑坡的分布、滑坡特征及成因机制研究,结果对于评价深水油气钻探及海底管道安全有较强的指导意义,对于认识陆坡区沉积物质搬运也有一定的科学意义。研究区位于南海北部陆坡白云凹陷区,水深约200~1700m,水深和地貌类型变化较大。本文综合利用多波束水深资料、浅地层剖面以及侧扫声呐资料,对研究区的海底滑坡的类型、规模、分布和成因机制进行了分析与研究,得到如下结论:(1)基于多波束地形数据,利用编制海底陡坡自动识别程序对海底滑坡进行了识别,并通过地震剖面资料和侧扫声呐资料对识别的滑坡进行对比验证,结果表明利用海底陡坡自动识别程序快速识别海底滑坡是可行的,但识别结果主要受水深数据精度的影响。(2)研究区海底滑坡主要分布在海底峡谷区,其中峡谷的头部和峡谷两侧的谷壁是海底滑坡集中分布区。在研究区共识别出145个海底滑坡,统计的结果显示,滑坡面积大小在0.04~15.88km2之间不等,其中91.7%的滑坡面积小于4km2;大约有110个海底滑坡(约占76%)分布在海底峡谷的谷壁及其附近区域。(3)对不同位置(上陆坡、中陆坡和下陆坡)的典型滑坡的内部声学结构的分析结果表明,上陆坡滑坡体属于脆性滑坡体,其特征是内部基本保持了原来的结构和层理;中陆坡海底滑坡具有明显的弧形滑动面,峡谷壁上的滑坡体属于塑性滑坡体,内部结构和层理杂乱;两峡谷中脊上的滑坡体属于脆性滑坡体;下陆坡峡谷尾部浊流堆积扇区的滑坡体主要是塑性滑坡体,且滑坡底部的滑动面不十分明显。(4)海底坡度和土体力学强度是研究区海底滑坡的主要控制因素。基于Geo Slope数值分析软件,构造了3°、6°、8°、9°、12°和15°六种坡度海底斜坡模型。计算结果表明,地震作用和斜坡坡度都是影响海底斜坡稳定性的重要因素,坡度较小的稳定斜坡,地震作用对斜坡稳定性的影响比较明显;随着斜坡坡度的增大,大于临界坡度时斜坡就会处于不稳定状态,此时地震作用的影响变得不再那么明显;通过8°和9°斜坡模型的对比,结合研究区海底坡度及滑坡分布特征,该研究区的斜坡稳定性临界坡度与数值模拟结果一致均约为9°。
[Abstract]:Submarine landslide is one of the widely developed geological hazards in the continental slope area, which is the dominant factor in shaping the topography and landform of the seabed. It is also an important way to transport sediments on the continental slope to deep-sea basins. There are abundant natural gas hydrates and oil and gas resources in the northern slope of the South China Sea. This paper takes Baiyun Sag on the northern slope of the South China Sea as the research area to study the distribution, characteristics and genetic mechanism of submarine landslides. The results are of great significance for evaluating the safety of deep water oil and gas drilling and submarine pipelines, as well as for the understanding of sediment transport in the continental slope. The study area is located in Baiyun sag on the northern slope of the South China Sea. The depth of water is about 200 ~ 1700m, and the water depth and geomorphologic types vary greatly. In this paper, the types and scale of submarine landslides in the study area are analyzed by using multi-beam bathymetric data, shallow stratum profile and lateral sonar data. The distribution and genetic mechanism are analyzed and studied. The following conclusions are obtained: 1) based on multi-beam topographic data, the submarine landslide is identified by compiling an automatic identification program for submarine steep slope. The results show that it is feasible to identify the submarine landslide quickly by using the automatic recognition program of submarine steep slope through seismic profile data and side scan sonar data. However, the identification results are mainly affected by the accuracy of the depth data. 2) the submarine landslides in the study area are mainly distributed in the submarine canyon area. The head of the canyon and the valley wall on both sides of the canyon are the concentrated distribution areas of submarine landslides. 145 submarine landslides have been identified in the study area, and the statistical results show that. The area of landslide varies from 0.04 ~ 15.88 km ~ 2, of which 91.7% is less than 4 km ~ 2; There are about 110 submarine landslides (about 76 parts) distributed in the valley wall of the submarine canyon and its adjacent area. The results of the analysis of the internal acoustic structure of the typical landslide on the middle and lower slopes show that the upper slope landslide belongs to the brittle landslide, and its characteristics are that the internal structure and stratification are basically maintained. The submarine landslide on the middle slope has obvious arc sliding surface, the landslide body on the valley wall belongs to the plastic landslide body, the internal structure and stratification are chaotic. The landslide on the middle ridge of the two canyons belongs to the brittle landslide. The slope body in the turbidity accumulation sector at the tail of the downslope canyon is mainly plastic landslide. The slope of the bottom of the landslide and the mechanical strength of the soil are the main controlling factors of the landslide. Based on the software of Geo Slope numerical analysis, 3 掳is constructed. 6 掳/ 8 掳/ 9 掳/ 12 掳and 15 掳/ 6 slope models. The calculated results show that seismic action and slope gradient are important factors affecting the stability of submarine slope, and the slope with low slope is stable. The effect of earthquake on slope stability is obvious. With the increase of slope gradient, the slope will be unstable when the slope is larger than the critical slope, and the effect of earthquake becomes less obvious. Based on the comparison of 8 掳and 9 掳slope models and the characteristics of submarine slope and landslide distribution in the study area, the critical slope of slope stability in the study area is about 9 掳consistent with the numerical simulation results.
【学位授予单位】：国家海洋局第一海洋研究所
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：P736;P642.22

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