Shaking table simulation of soft sediment deformation structures in lacustrine sediments

IF 2.7 2区地球科学 Q1 GEOLOGY

Sedimentary Geology Pub Date : 2024-10-01 DOI:10.1016/j.sedgeo.2024.106756

Lianji Liang , Zhihao Lu , Qitao Zhang , Hongshui Tian , Fuchu Dai , Hanchao Jiang , Ning Zhong

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引用次数: 0

Abstract

Soft sediment deformation structures (SSDSs) in lacustrine sediments could record paleoearthquakes in tectonically active areas. However, their interpretations of deformation and triggering mechanisms still exist disagreement due to the lack of understanding of natural formation processes of SSDSs. In this study, two large shaking table experiments of saturated lacustrine sedimentary sequences, including Model 1 (simple stratigraphic system of thick silty-clay and sand layer) and Model 2 (stratigraphic systems of thin silty-clay and sand alternating layers) were carried out at the different peak ground accelerations (PGA) in order to simulate the earthquake-triggered SSDSs on the basis of field investigation in Tashkorgan of western China. The results showed that there were no SSDSs formed at the PGA 0.125g, and the excess pore-water pressure ratio (γ_μ) measured in the sand layer was lower than 0.1; sand volcanos, pipes and sand veins were formed at the PGA 0.25g, and the γ_μ value of the sand layer reached about 0.2 with the maximum liquefied depths of nearly 30 cm, indicating that weak liquefaction occurred in the sand layer; sand volcanos, pipes, sand veins, diapirs, load and flame structures, ball-and-pillow structures, silty-clay deformation structures were formed at the PGA 0.5g and 0.8g, and the γ_μ value of sand layer reached about 0.91 and 0.94 with the maximum liquefied depths of nearly 60 cm and 100 cm, respectively. The γ_μ value of silty-clay layers measured in all the tests was lower than 0.1, indicating that little liquefaction but thixotropy happened in the silty-clay layers. The tests showed that liquefied SSDSs could form at the PGA 0.25g, while thixotropic and gravity-driven SSDSs could form until the PGA reached 0.5g. This study also provided insights for single or closely spaced shaking events being responsible of superposed deformed beds. The simulated SSDSs have striking resemblance to that of ones identified in the field, supporting the earthquake triggering of SSDSs in the Tashkorgan area.

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振动台模拟湖沼沉积物中的软沉积物变形结构

湖沼沉积物中的软沉积物变形结构（SSDSs）可以记录构造活跃地区的古地震。然而，由于对 SSDSs 的自然形成过程缺乏了解，他们对其变形和触发机制的解释仍存在分歧。本研究在中国西部塔什库尔干野外调查的基础上，对饱和湖相沉积序列进行了两次大型振动台实验，包括模型 1（厚淤泥质粘土和砂层的简单地层系统）和模型 2（薄淤泥质粘土和砂层交替的地层系统），在不同的峰值地面加速度（PGA）下模拟地震触发的 SSDS。结果表明，PGA 0.125g 时未形成 SSDS，测得砂层过剩孔隙水压力比（γμ）小于 0.1；PGA 0.25g 时形成了砂火山、砂管和砂脉，砂层γμ值达到 0.2 左右，最大液化深度为 0.2m。2，最大液化深度近 30 cm，表明砂层发生了弱液化；在 PGA 0.5g 和 0.8g 时，砂层形成了砂火山、管道、砂脉、斜管、荷载和火焰结构、球枕结构、淤泥质变形结构，砂层的 γμ 值分别达到约 0.91 和 0.94，最大液化深度近 60 cm 和 100 cm。所有试验中测得的淤泥质粘土层的γμ值均小于 0.1，表明淤泥质粘土层液化程度很小，但发生了触变。试验表明，液化 SSDS 可在 PGA 值为 0.25g 时形成，而触变性 SSDS 和重力驱动 SSDS 可在 PGA 值达到 0.5g 时形成。这项研究还为单次或间隔较近的振动事件造成叠加变形床提供了启示。模拟的 SSDS 与实地发现的 SSDS 非常相似，这支持了地震引发塔什干地区 SSDS 的观点。

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来源期刊

Sedimentary Geology 地学-地质学

CiteScore

5.10

自引率

7.10%

发文量

133

审稿时长

32 days

期刊介绍： Sedimentary Geology is a journal that rapidly publishes high quality, original research and review papers that cover all aspects of sediments and sedimentary rocks at all spatial and temporal scales. Submitted papers must make a significant contribution to the field of study and must place the research in a broad context, so that it is of interest to the diverse, international readership of the journal. Papers that are largely descriptive in nature, of limited scope or local geographical significance, or based on limited data will not be considered for publication.