Earthquakes and soil liquefaction in flood stories of the ancient Near East

Flood stories in the Hebrew Bible and the Koran appear to be derived from earlier flood stories like those in the Gilgamesh Epic and still earlier in the Atrahasis. All would have their source from floods of the Tigris and Euphrates rivers.

The Gilgamesh Epic magnifies the catastrophe by having the flood begin with winds, lightning, and a shattering of the earth, or earthquake. Elsewhere in Gilgamesh, an earthquake can be shown to have produced pits and chasms along with gushing of water. It is commonly observed that earthquake shaking causes water to gush from the ground and leaves pits and open fissures. The process is known as soil liquefaction. Earthquake is also a possible explanation for the verse “all the fountains of the great deep (were) broken up” that began the Flood in Genesis. Traditionally, the “great deep” was the ocean bottom. A more recent translation substitutes “burst” for “broken up” in describing the fountains, suggesting that they erupted at the ground surface and were caused by an earthquake with soil liquefaction. Another relation between soil liquefaction and the Flood is found in the Koran where the Flood starts when “water gushed forth from the oven”. Soil liquefaction observed erupting preferentially into houses during an earthquake provides a logical interpretation if the oven is seen as a tiny house. A case can be made that earthquakes with soil liquefaction are embedded in all of these flood stories.     

晋中至太原城际铁路沿线地质条件分析

晋中至太原城际铁路位于山西断陷带次级构造单元太原断陷盆地内,盆地内部新构造运动复杂,城际铁路沿线跨越多条第四纪隐伏活动断裂,并穿过榆次地裂缝发育地带及砂土液化区域,这些地质问题极大地影响着晋中至太原城际铁路的前期勘测选线。本文从地质构造、地层岩性、浅层地震勘探等方面对穿越城际铁路的三条活动断裂的危险性进行了分析评价,以查明断裂错动对城际铁路的影响。结合前人对榆次地裂缝的研究成果,对城际铁路附近的地裂缝发育情况进行了调查验证,以查明榆次地裂缝对城际铁路的影响。通过在城际铁路车站及车辆段布置地质钻孔,进行标贯试验、剪切波速测试,以查明城际铁路沿线工程地质条件,对沿线车站及车辆段场地进行液化判定及场地类别判定。针对城际铁路沿线存在的上述地质问题,给出了相应的工程建议,对城际铁路前期勘测设计具有重要的指导意义。     

Laboratory Study for Influence of Clay Content (CC) on Wave-Induced Liquefaction in Marine Sediments

In this artice, the influence of clay content on the wave-induced liquefaction in marine sediments was reported. The one-dimensional (1-D) equipment was setup with a vertical cylinder and 1.8–m–thick clayey sandy deposit and 0.2–m–thick water above the deposit. Unlike the previous experimental study for a single soil layer, this study used sand-kaolin mixtures, sand-illite mixtures, and sand-bentonite mixtures as the experimental samples. A series of experiments with 3,000 wave cycles in each test were conducted under numerous wave and soil conditions, which allowed us to examine the influence of clay content (CC) on wave-induced liquefaction in marine sediments. The experimental results showed that the clayey sandy deposit will become prone to liquefaction with the increase of CC when CC is less than a critical value, which depends on the type of clay. However, when CC is greater than the critical value, liquefaction depth will decrease as CC increases. Furthermore, when the CC value reaches a certain level, liquefaction will not occur. For example, no liquefaction occurs when CC ≥ 33% for both kaolin-sand and illite-sand mixtures and CC ≥ 16.36% for bentonite-sand mixtures.     

A Preliminary Study on the Soft–Sediment Deformation Structures in the Late Quaternary Lacustrine Sediments at Tashkorgan, Northeastern Pamir, China

This study identified soft–sediment deformation structures(SSDS) of seismic origin from lacustrine sediments in the late Quaternary paleo–dammed lake at Tashkorgan, northeastern Pamir. The observed deformation structures include sand dykes, liquefied diapir and convolute structures, gravity induced SSDS, and thixotropic pillar and tabular structures. We conducted a preliminary study on the morphology, formation and trigger mechanisms of pillar and tabular structures formed by liquefaction of underlying coarse sand and thixotropy of the upper silty clay. The regional tectonic setting and distribution of lacustrine strata indicate that the most probable trigger for the SSDS in lacustrine sediments was seismic activity, with an approximate earthquake magnitude of M6.0; the potential seismogenic fault is the southern part of the Kongur normal fault extensional system. AMS 14 C dating results indicate that the SSDS were formed by seismic events occurring between 26050±100 yr BP and 22710±80 yr BP, implying intense fault activity in this region during the late Pleistocene. This study provides new evidence for understanding tectonic activity and regional geodynamics in western China.     

地下RC结构物地震响应特征土工离心试验的模拟

地下结构物抗震稳定性的研究具有重要实际意义。基于动态土工离心试验,应用有效应力法分析了不同水平地震作用下土层和地下RC结构物的最大水平位移、不同埋深的土层加速度和超孔隙水压力变化规律,以及结构物的破坏发展特征,并进一步与试验结果进行了相互验证和对比,取得了较好效果,为重要地下结构物的抗震设计提供了依据和参考。     

某长江大桥深度超过15米的砂土层液化势的综合评价

不同抗震设计规范的砂土液化判别方法或国内外其他有代表性的液化判别方法所采用的地震动参数和土性指标及其埋藏条件是不同的,因而采用这些方法对同一工程场地进行液化势预测时其评价结果通常有一些差异,甚至会得到相反的结论。为了给重大工程建设提供较为合理、可信的地基液化势预测结果,采用多种液化判别方法进行场地液化势的综合评价是比较客观的,也是必要的。本文结合某长江大桥桥基工程,采用建筑抗震设计规范的砂土液化判别方法、国内外有代表性的液化判别方法、有限元数值分析法等多种方法逐一对该工程场地砂性土层进行液化判别,并结合室内动三轴液化试验结果,对主桥墩不考虑冲刷条件和考虑一般冲刷深度5m条件时的砂性土层进行了液化势的综合评价,并将各土层的液化势分为液化、可能液化和不液化3个等级,得到了较为合理可靠的判别结果。     

饱和砂土液化研究进展

根据国内外文献资料,从三方面总结了饱和砂土的最新进展:饱和砂土液化判别方法、砂土液化的试验研究以及液化后分析,特别是探讨了液化对上部结构的影响。最后指出了存在的问题和今后的研究方向。     

浅基础水平场地砂土液化危害性评价

分析了《建筑抗震设计规范》中砂土液化危害性评价方法的不足,通过确立液化土层在不同震害模式情况下的液化震陷计算值,建立了以震陷值S为指标的浅基础水平场地地基液化危害性评价等级,得到了其评价程序.     

波浪作用下成层海床孔隙水压力响应的简化分析

采用不排水条件下孔隙水压力发展模式,作为Terzagh i一维固结方程中考虑波浪循环作用所引起的孔隙水压力源项,对于成层海床建立了推广的一维动力固结方程,运用数理方程中的分离变量法与G reen函数求解了成层海床在波浪作用下残余孔隙水压力的发展规律,进而对成层海床的液化势进行了评判。对比计算与分析表明,海床表层土的渗透性及其厚度对于海床的整体抗液化性能具有显著的影响,低渗透性的表层导致海床孔隙水压力的显著积累,此时表层置换法是防治液化的有效途径。     

长输管道抗震研究的新进展

本文主要从以下4个方面:地震对长输管道的危害、长输管道震害的研究方法、管道抗震分析和管道抗震的措施,介绍了近几年长输管道抗震方面的研究进展,指出了今后长输管道的研究方向。