A new high-stress undrained ring-shear apparatus and its application to the 1792 Unzen–Mayuyama megaslide in Japan

Sassa and others in the Disaster Prevention Research Institute (DPRI), Kyoto University, developed a series of undrained ring-shear apparatus to physically simulate landslide initiation and motion, from DPRI-3 (Sassa 1992) to DPRI-7 (Sassa et al., Landslides 1(1):7–19, 2004). The maximum undrained capacities in the DPRI series ranged from 300 to 650 kPa. Sassa and others in the International Consortium on Landslides (ICL) have developed a new series of undrained ring-shear apparatus (ICL-1and ICL-2) for two projects of the International Programme on Landslides (IPL-161 and IPL-175). Both projects are supported by the Science and Technology Research Partnership for Sustainable Development Program (SATREPS) of Japan. ICL-1 was developed to create a compact and transportable apparatus for practical use in Croatia; one set was donated to Croatia in 2012. ICL-2 was developed in 2012–2013 to simulate the initiation and motion of megaslides of more than 100 m in thickness. The successful undrained capacity of ICL-2 is 3 MPa. This apparatus was applied to simulate possible conditions for the initiation and motion of the 1792 Unzen–Mayuyama megaslide (volume, 3.4?×?10⁸ m³; maximum depth, 400 m) triggered by an earthquake. The megaslide and resulting tsunami killed about 15,000 people. The Unzen Restoration Office of the Ministry of Land, Infrastructure and Transport (MLIT) of Japan systematically collected various papers and reports and published two summary leaflets: one in English in 2002 and an extended version in Japanese in 2003. Samples were taken from the source area (for initiation) and the moving area (for motion). The hazard area was estimated by the integrated landslide simulation model LS-RAPID, using parameters obtained with the ICL-2 undrained ring-shear apparatus. The estimated hazard area agrees reasonably with the landslide moving area reported in the Ministry leaflets.     

Three-dimensional hydrostratigraphical modelling to support evaluation of recharge and saltwater intrusion in a coastal groundwater system in Vietnam

Saltwater intrusion is generally related to seawater-level rise or induced intrusion due to excessive groundwater extraction in coastal aquifers. However, the hydrogeological heterogeneity of the subsurface plays an important role in (non-)intrusion as well. Local hydrogeological conditions for recharge and saltwater intrusion are studied in a coastal groundwater system in Vietnam where geological formations exhibit highly heterogeneous lithologies. A three-dimensional (3D) hydrostratigraphical solid model of the study area is constructed by way of a recursive classification procedure. The procedure includes a cluster analysis which uses as parameters geological formation, lithological composition, distribution depth and thickness of each lithologically distinctive drilling interval of 47 boreholes, to distinguish and map well-log intervals of similar lithological properties in different geological formations. A 3D hydrostratigraphical fence diagram is then generated from the constructed solid model and is used as a tool to evaluate recharge paths and saltwater intrusion to the groundwater system. Groundwater level and chemistry, and geophysical direct current (DC) resistivity measurements, are used to support the hydrostratigraphical model. Results of this research contribute to the explanation of why the aquifer system of the study area is almost uninfluenced by saltwater intrusion, which is otherwise relatively common in coastal aquifers of Vietnam.     

从北华北盆地的地质结构看1976年唐山地震的发震机理

北华北盆地经过古近纪拉张、新近纪挤压形成了怀柔—三河—唐山—锦州—下辽河向南突出的弧形构造带,它与向南推挤的南北向唐山—丰南隆起一起构成燕辽山字型构造。唐山—丰南脊柱向南推挤造成弧顶挤压应力集中。一旦应力集中超过极限值,应力必然释放,形成大地震。文章从这一认识出发对1976年唐山地震的发震机理进行了探讨。     

内蒙白音华一号露天煤矿首采区南(非工作)帮边坡稳定性评价

根据工程地质勘察成果,分析了首采区南(非工作)帮边坡岩体的工程地质条件,并据此进行了岩石物理力学性质统计,软弱层(面)分布特征以及泥岩、炭质泥岩对地下水敏感度等研究。在此基础上建立了不同条件下不同滑面类型的边坡极限平衡法数值分析模型,并进行了相应的边坡稳定性计算成果评价,由此提出了南(非工作)帮边坡角的建议值:次边坡角采用值α1≤13°,主边坡角采用值α2≤19°。根据评价结果提出了修正岩体力学参数、合理调整采区和留设安全煤壁的建议。该评价结果为露天煤矿总平面设计系统中的边坡设计提供了依据。     

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滩间山金矿矿床成因初步探讨

本文通过对滩间山矿区地层、构造及岩浆岩与成矿关系的研究,认为中元古界万洞沟群是金的矿源层;成矿构造具有多期次、多阶段活动的特点,矿体受单一及复合型式的构造控制;华力西期侵入体对成矿作用仅体现于为矿床的形成与再造提供热源。矿质在弱酸—中偏碱性溶液中,主要呈硫络合物的形式搬运、并在还原条件下成矿。特别指出,含磷质物地层是区内重要的岩金找矿标志之一。     

The application of δ13C and C/N ratios as indicators of organic carbon sources and paleoenvironmental change of the mangrove ecosystem from Ba Lat Estuary, Red River, Vietnam

In this study, two sediment cores (~70 cm) were collected from separate mangrove forests straddling the Ba Lat Estuary, Red River of northern Vietnam, to examine the origins of sedimentary organic carbon (SOC) and reconstruct the paleoenvironment. In addition, mangrove leaves and particulate organic matter were collected and measured for δ¹³C to trace the origins of SOC. The cores were analyzed by high-resolution sections for δ¹³C, TOC, C/N ratios, sediment grain size, water content, and porosity, with values of δ¹³C, TOC, and C/N ratios ranging from −28.19 to −22.5‰, 2.14–30.94 mg/g, and 10.29–18.32, respectively. The δ¹³C and TOC relationship indicated that there were some small residual effects of diagenetic processes on TOC and δ¹³C values in mangrove sediments. However, the shifts of δ¹³C and C/N ratios from the bottom to the surface sediment of the cores explained the change in organic matter sources, with values of C/N > 12 and δ¹³C < −25‰, and C/N < 12 and δ¹³C > −25‰ indicated terrestrial (e.g., mangrove litter) and marine phytoplankton sources, respectively. The covarying δ¹³C, C/N ratios, and sediment grain sizes during the past 100 years in sediment cores showed that the paleoenvironment may be reconstructed into three environments (subtidal, tidal flat, and intertidal mangrove). General trends in δ¹³C and C/N followed a gradual increase in the C/N ratio and a concomitant decrease in δ¹³C from the subtidal, through to tidal flat, and to the intertidal mangrove. δ¹³C and C/N ratios are therefore effective in measuring the continuum of environmental change in mangrove ecosystem.     

Comparative response assessment of minimally compliant low‐rise conventional and base‐isolated steel frames

In this study, the multi‐intensity seismic response of code‐designed conventional and base‐isolated steel frame buildings is evaluated using nonlinear response history analysis. The results of hazard and structural response analysis for three‐story braced‐frame buildings are presented in this paper. Three‐dimensional models for both buildings are created and seismic response is assessed for three scenario earthquakes. The response history analysis results indicate that the design objectives are met and the performance of the isolated building is superior to the conventional building in the design event. For the Maximum Considered Earthquake, isolation leads to reductions in story drifts and floor accelerations relative to the conventional building. However, the extremely high displacement demands of the isolation system could not be accommodated under normal circumstances, and creative approaches should be developed to control displacements in the MCE. Copyright © 2010 John Wiley & Sons, Ltd.     

Structural controls on the occurrence and morphology of karstified assemblages in northeastern Vietnam: a regional perspective

Karstified assemblages occur widely in, and distinctively shape, the geological landscape of the northeastern part of Vietnam. These carbonate rocks were deposited during three major periods of basinal evolution including: (1) Late Cambrian, (2) Early Devonian to Early Carboniferous, and (3) Carboniferous to Earliest Triassic. These sedimentary units contain primary sedimentary structures and have undergone numerous post-depositional geological processes including multiple deformational events, which can be regionally correlated. Several thrusting events and associated folding have led to significant thickening of the carbonate units. The subsequent post-thrusting cross-folding events, followed by several phases of brittle faulting and fracturing further modified the spatial geometry and outcrop of these rocks. The combination and interaction of the primary structures with those formed during the long-lived and complicated deformational history is an important controlling factor in local and regional hydrogeological systems in the region. The geological structures now recorded in the carbonate units ultimately govern the formation of the unique modern surface and sub-surface geomorphology of the karstic terrains in northeastern Vietnam. These structures should be further investigated in the context of water resource assessment and natural hazard prediction and mitigation.