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排序方式: 共有113条查询结果,搜索用时 24 毫秒
1.
J. Hošek M. Verčík P. Pokorný J. Beneš V. Komárková T. Radoměřský N. Atanasoska V. Todoroska P. Ardjanliev 《第四纪科学杂志》2021,36(6):1003-1012
Geoarchaeological investigations on the northeastern shore of Lake Ohrid revealed 3.5 m thick deepwater lacustrine sediments overlying terrestrial vegetation macrofossils, worked wood and abundant potsherds dated to the Late Bronze Age (LBA). Distinct contact of deepwater sediment with the sub-aerial weathered limestone bedrock point to a sudden increase in lake level. According to radiocarbon data, catastrophic flooding occurred shortly after 1214 yr bc. Because the area is located in a highly active seismic zone, we propose that this event was caused by tectonically induced, metre-scale coseismic subsidence related to faults bordering the Ohrid alluvial plain. Moreover, this event coincides well with a dramatic switch in the habitation and settlement strategy in the region. More important, however, is the finding that the age of the proposed massive tectonic event and change in habitation lies within the interval of the proposed ‘earthquake storm’ in the eastern Mediterranean dated to 1225–1175 bc. As the Ohrid-Korça zone belongs to the same tectonic province, a relationship between the abovementioned earthquakes and the proposed event can be expected. This research therefore might provide the first direct evidence of a large-scale earthquake event linkable to the LBA collapse of Europe's first urban civilisation in the Aegean. 相似文献
2.
Considering the shear deformation and thickness stretching of large deformation, a modified numerical calculation method based on the thick shell theory is established to determine the collapse pressure of thick-walled pipes. Verification experiments are conducted on ten pipe specimens in hyperbaric chambers. The good agreement between experimental results and numerical predictions shows the validity and reliability of the new numerical calculation method. Combining DNV specification, the characteristic collapse pressure is also calculated for comparison. The difference between experimental results and DNV calculations illustrates the latter one is much conservative in predicting collapse pressure for thick-walled pipes. Sensitivity analysis on manufacturing imperfections and material properties is investigated for pipes with different D/t ratios. Thick-walled pipes are easier to be affected by initial ovality, residual stress and hardening factor. Based on the stress distribution at the moment of collapse, a novel discovery is found that the collapse pressure of thick-walled pipes is dominated by material plastic behavior. 相似文献
3.
The Xiadian Fault is a very important concealed active fault in the Beijing Plain. It is the seismogenic fault of the Sanhe-Pinggu MS8.0 earthquake in 1679. The ancient earthquake sequence in the long historical period is of great significance to understand accurately the activity characteristics of the fault and effectively reduce the earthquake disaster risk in Beijing. We have re-interpreted the Dahuzhuang trench, and identified three layers of buried paleosol, six collapsed wedges and one sand liquefaction event. Further, through the comparison with the landmark strata and paleo-earthquake events revealed by other trenches on the fault, an ancient earthquake sequence with a long historical period of the Xiadian Fault was established:since the 31ka, the Xiadian Fault has 11 occurrences of earthquake events (including the 1679 earthquake), and the average recurrence interval is about 2.8ka. The paleo-seismic sequence also shows that there is an ancient earthquake cluster period from 25ka to 15ka, and there are 5 strong earthquakes in the cluster period. The average recurrence interval is about 2.0ka, which reflects the phase difference of the Xiadian Fault activity. 相似文献
4.
不良工程地质组合导致房屋地基开裂或滑移,墙体承重失衡导致房屋结构性破裂。煤矿开采直接导致地下水位下降,部分影响建筑物地基稳定性及地面塌陷。 相似文献
5.
6.
"5·12"汶川特大地震引发的次生山地灾害中以山体崩塌数量最多.本文在对国道213线都江堰至映秀段以及水磨支线公路边坡地震崩塌调查研究的基础上,分析总结了岩土体边坡的崩塌成灾模式、崩塌作用机理以及崩塌自组织临界(SOC)动力学特性.调查范围包括Ⅸ~Ⅺ度地震区,工点105个.对崩塌体方量、崩塌深度进行统计分析后发现,在Ⅸ度区崩塌体方量和崩塌深度都符合负幂律分布,呈现出明显的自组织临界动力学特性;而Ⅹ、Ⅺ度地震区不呈现该崩塌特性,其崩塌动力学性质受地震的强扰作用控制. 相似文献
7.
8.
Historical evidence shows block breakdown and collapse are actively occurring in large fault aligned caverns in the Yorkshire Dales karst. Deployment of ground penetrating radar at two such sites has provided detailed images of the sedimentary sequences below the present day cavern floor but no large blocks are imaged within the sediments. Solutional processes must be removing limestone from the sediment to allow continued cavern growth. Possible mechanisms to account for the lack of large blocks within the sediment fill are discussed. 相似文献
9.
Two distinct series of slumps deform the upper part of the sedimentary sequence along the continental margin of the Levant.
One series is found along the base of the continental slope, where it overlies the disrupted eastern edge of the Messinian
evaporites. The second series of slumps transects the continental margin from the shelf break to the Levant Basin. It seemed
that the two series were triggered by two unrelated, though contemporaneous, processes. The shore-parallel slumps were initiated
by basinwards flow of the Messinian salt, that carried along the overlying Plio-Quaternary sediments. Seawater that percolated
along the detachment faults dissolved the underlying salt to form distinctly disrupted structures. The slope-normal slumps
are located on top of large canyons that cut into the pre-Messinian sedimentary rocks. A layer of salt is found in the canyons,
and the Plio-Quaternary sediments were deposited on that layer. The slumps are bounded by large, NW-trending faults where
post-Messinian faulted offset was measured. We presume that the flow of the salt in the canyons also drives the slope-normal
slumps. Thus thin-skinned halokynetic processes generated the composite post-Tortonian structural patterns of the Levant margin.
The Phoenician Structures are a prime example of the collapse of a distal continental margin due to the dissolution of a massive
salt layer. 相似文献
10.
Free-Swell and Swelling Pressure of Unsaturated Compacted Clays; Experiments and Neural Networks Modeling 总被引:1,自引:0,他引:1
Expansive soils have received attentions of several investigators in the past half of century in the problematic soils context.
Volume change behavior of unsaturated compacted soils in presence of water and change of degree of saturation was observed
in two form of heave or collapse. Low water content and low density compacted soils in presence of enough surcharge pressure
lose stability and collapse, because of their metastable and susceptible structure to change of degree of saturation. Free-swell
and swelling pressure of five compacted clays, covering low to high plastic clays have been investigated in respect to compaction
states and swelling pressure was compared with collapse pressure threshold. The results of experiments were utilized in two
Artificial Neural Networks to predict free-swell percent and swelling pressure of a soil sample based on index properties
and compaction state. 相似文献