Fabric evolution and liquefaction resistance in multiple-liquefaction process: a micromechanical study using DEM-clump

Acta Geotechnica - Recent earthquake case histories in Japan and New Zealand revealed that soil sites can experience liquefaction multiple times under a sequence of earthquake shaking. Field...     

Hybrid machine learning model with random field and limited CPT data to quantify horizontal scale of fluctuation of soil spatial variability

Acta Geotechnica - The scale of fluctuation (SOF) is the critical parameter to describe the soil spatial variability, which significantly influences the embedded geostructures. Due to the limited...     

Enhanced anisotropic bounding surface plasticity model considering modified spacing ratio of anisotropically consolidated clay

Acta Geotechnica - The critical state of anisotropically consolidated clay is not well captured by the classical anisotropic bounding surface plasticity model without considering the real...     

Shaking table test of subgrade slope reinforced by gravity retaining wall with geogrids

Gravity retaining wall with geogrids has showed excellent seismic performance from Wenchuan great earthquake. However, seismic damage mechanism of this kind of wall is not sufficiently clear. In view of this, a large shaking table test of the gravity retaining wall with geogrids to reinforce the subgrade slope was carried out, and based on the Hilbert-Huang transform and the marginal spectrum theory, the energy identification method of the slope dynamic failure mode was studied. The results show that the geogrids can effectively reduce displacement and rotation of the retaining wall, and it can effectively absorb the energy of the ground movement when combined with the surrounding soil. In addition, it also reveals the failure development of the gravity retaining wall with geogrids to reinforce the subgrade slope. The damage started in the deep zone near the geogrids, and then gradually extended to the surface of the subgrade slope and other zones, finally formed a continuous failure surface along the geogrids. The analysis results of the failure mode identified by the Hilbert marginal spectrum are in good consistency with the experimental results, which prove that the Hilbert marginal spectrum can be applied to obtain the seismic damage mechanism of slope.

     

In situ calcite U−Pb geochronology by high-sensitivity single-collector LA-SF-ICP-MS

Science China Earth Sciences - U?Pb geochronology of calcite using laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS) is an emerging method, with potential applications...     

Temporal evolution of the focal mechanism consistency of the 2021 Yangbi MS 6.4 earthquake sequence in Yunnan

Using the Cut And Paste (CAP) method, we invert the focal mechanism of 38 moderate earthquakes (M_S ≥ 3.0) recorded by Yunnan seismic network and analyze the corresponding focal mechanism consistency based on the minimum spatial rotation angle. Our results indicate that the M_S 6.4 mainshock is induced by a lateral strike slip fault (with a rake angle of ～ ?165°) and a little normal-faulting component event along a nearly vertical plane (dipping angle～ 79° and strike ～138°). Combining our results with high resolution catalog, we argue that the seismogenic fault of this earthquake sequence is a secondary fault western to the major Weixi-Qiaohou-Weishan fault. The focal mechanism evolution can be divided into three periods. During the first period, the foreshock sequence, the focal mechanism consistency is the highest (KA<36°); during the second period which is shortly after the mainshock, the focal mechanism shows strong variation with KA ranging from 8° to 110°; during the third period, the seismicity becomes weak and the focal mechanism of the earthquakes becomes more consistent than the second period (18°<KA<73°). We suggest that the KA, to some extent, represents the coherence between local tectonic stress regime and the stress state of each individual earthquake. Furthermore, high focal mechanism consistency and high linearity of seismic distribution may serve as indicators for the identification of foreshock sequence.     

羌塘盆地毕洛错地区古油藏地球化学特征与油源对比

羌塘盆地是一个大型中生代海相沉积盆地,盆地内发育多套烃源岩,并发现多处古油藏和油气显示,确定古油藏油源对油气勘探至关重要.为明确古油藏油源,对古油藏和烃源岩样品进行地球化学分析.研究表明古油藏可分为2类:Ⅰ类古油藏整体处于成熟-高成熟阶段,C₂₄四环萜烷丰度较高,三环萜烷丰度低,C₂₉规则甾烷占有一定优势,C₂₉藿烷含量较高,体现出以陆源有机质贡献为主的特征.Ⅱ类古油藏整体处于低成熟-成熟阶段,以C₂₃三环萜烷为主峰,低丰度C₂₄四环萜烷,C₂₇规则甾烷占优势,表明母质来源以低等水生生物为主.油源对比表明,两类古油藏来源于不同的烃源岩,Ⅰ类油藏来自于上三叠统扎那组烃源岩,Ⅱ类油藏主要为下侏罗统曲色组烃源岩的贡献.      

塔中地区良里塔格组海平面变化对高频层序和沉积演化的控制

【研究目的】碳酸盐岩地层易受海平面变化影响而发育高频层序,但是反映海平面变化的地化指标的精度不足,导致高频层序对海平面振荡的响应认识不够深入,高频海平面变化对台地边缘礁滩沉积的高频层序和沉积演化的控制尚不明确。【研究方法】论文研究选取塔里木盆地塔中地区某钻井的上奥陶统良里塔格组连续取心资料,通过密集取样开展微相分析和碳、氧同位素测试分析。【研究结果】该井良里塔格组中上部发育7种微相类型,沉积演化分析表明良里塔格组沉积中—晚期,沉积环境由潮坪向生物礁-颗粒滩再到较深水的开阔台地演化。碳、氧同位素测试显示δ¹³C为0.5993‰~1.6228‰（均值1.139‰）,δ¹⁸O值为-8.3608‰~-5.1452‰（均值为-6.790‰）;δ¹³C和δ¹⁸O的振荡变化与微相变化和沉积旋回对应良好。古海洋条件分析表明,良里塔格组沉积时期气候温热,礁、滩体发育层段样品的古温度值最高,代表着高的碳酸盐产率;Z值所反映的古盐度在底部潮坪沉积段最高,在高频旋回的顶部古盐度均明显减小,指示可能存在大气淡水的影响。与塔北地区南缘和巴楚地区的δ¹³C和δ¹⁸O存在一定差异,主要受控于沉积环境和古水深。【结论】良里塔格组中—上部存在至少3个完整的海平面升降变化周期,内部又包括至少2个次级周期;不同级别的海平面振荡主要受古气候变化驱动,并控制了高频层序的发育。海平面先缓慢上升再持续稳定或小规模振荡,是连续厚层的生物碎屑和砂屑颗粒滩沉积发育的有利条件;良里塔格组沉积晚期海平面快速上升,沉积环境向滩间洼地和较深水的开阔台地转变。在高频层序顶部海平面的小规模下降导致的早期岩溶作用是礁滩体储层质量改善的重要因素。     

Investigation of rainfall-induced toe-cut slope failure mechanisms in the southeastern coastal area of China

Natural Hazards - Owing to the contradiction between the mountainous terrain and increasing population density in the southeastern coastal region of China, toe-cut slopes are widely distributed in...