Evaluation of seismic displacement demands from the September 19, 2017 Puebla‐Morelos (Mw = 7.1) earthquake in Mexico City

This short communication presents the assessment of seismic inelastic and elastic displacement demands computed from earthquake ground motions (EQGMs) recorded in Mexico City during the intermediate‐depth intraslab Puebla‐Morelos earthquake on 19 September 2017 (Mw = 7.1). Evaluation is conducted by means of peak elastic and inelastic displacement demand spectra, inelastic displacement ratio, C_R, spectra, and generalized interstory drift spectra computed for selected recording stations located in different soil sites of Mexico City, including those located in areas of reported collapsed buildings. Results of this study confirm previous observations made from interplate (subduction) EQGMs that peak inelastic displacement demands are greater than corresponding elastic counterparts for short‐to‐medium period structures, while the opposite is true for medium‐to‐long period structures. Possible basin site effects were identified from generalized interstory drift spectra. It is also shown that an equation introduced in the literature to obtain estimates of C_R developed from interplate EQGMs provides also a good estimate for mean C_R computed from the intermediate‐depth intraslab EQGMs.     

Evaluating spatial variation of suspended sediment rating curves in the middle Yellow River basin,China

Abstract The suspended sediment load in the middle Yellow River basin (YRB) cannot be well predicted by capacity‐based transport formulas because a large fraction of suspended sediment load is composed of wash load. This study evaluated the spatial variations of sediment rating curves (SRCs) in the middle YRB. Both power and linear SRCs were used to fit daily flow and suspended sediment concentration (SSC) historical data at 49 gauging stations throughout the middle YRB. The spatial variation in regression coefficients was investigated, and the relationship between regression coefficients and the physical characteristics of watersheds was discussed. The results indicate that SRC regression coefficients vary with drainage area and basin slope, but their responses to these parameters are remarkably different in watersheds with different underlying surfaces, which indicates the significance of sediment availability, erodibility, and grain size distribution. For power SRCs representing sediment transport in unsaturated flows, the regression coefficients are more closely correlated with the drainage area in loess regions and with the basin slope in rock mountain regions. For linear SRCs representing sediment transport in saturated flows, saturated SSCs vary with coarse (particle size > 0.05 mm) and fine (particle size < 0.01 mm) fractions in suspended sediment. The maximum saturated SSC among the different gauging stations is associated with the optimal grain size composition of suspended sediment, which has been proposed for loess regions in previous studies. This study provides theoretical support for estimating the regression parameters for sediment transport modelling, especially in ungauged basins.     

广西航运枢纽工程建设中的极软岩研究

广西郁江桂平至上游百色规划有10个千吨级航运枢纽梯级,其中老口、鱼梁、那吉处在南宁、百色第三纪盆地。盆地内泥质岩石属软~极软泥岩,它具有低强度、对环境敏感、弱改造等特性,反映在工程设计中地基承载力不足、地基应力及变形超标,抗剪强度低、抗滑稳定问题突出等方面;在工程施工中体现在岩体工程稳定性差,施工保护要求高等。根据那吉等工程勘探试验研究成果,提出针对软岩工程地质问题评价及基础验收、建基面保护、地基处理等应注意的问题和采取的对策。     

Streamflow prediction under extreme data scarcity: a step toward hydrologic process understanding within severely data-limited regions

Streamflow prediction in ungauged basins is necessary to support water resources management decisions. Herein we refine and evaluate the Streamflow Prediction under Extreme Data-scarcity (SPED) model, a framework designed for streamflow prediction within regions of sparse hydrometeorological observation. With the SPED framework, inclusion of soft data directs optimization to balance runoff efficiency with the selection of hydrologically representative parameters. Here SPED is tested in catchments around the world, including four well-gauged catchments, by mimicking data-scarcity and comparing against data-intensive approaches. By differentiating equifinal models, SPED succeeds where traditional approaches are likely to fail: partially dissimilar reference/target catchments. For instance, in a pair of reference/target catchments with different base flow regimes, SPED outperforms a model calibrated only to maximize efficiency (NSE of 0.54 versus 0.08). SPED performs consistently (NSE range: 0.54–0.74) across the diverse climatological and physiographic settings tested and proves comparable to state-of-the-science methods that use robust data networks.     

北京顺义-前门-良乡断裂探槽的微观分析及其启示

松散沉积物中的断层常常未留下明显的宏观形迹,单靠肉眼观测往往难以确定断层是否存在,即使判断出有断层亦常难以确定其活动性质和活动方式。大量资料表明,微观分析是探讨松散沉积物中断层和古地震事件的行之有效的方法。文中通过对采自顺义-前门-良乡断裂的顺义油库探槽样品的微观分析,探寻松散沉积物中宏观形迹不明断层的显微沉积学和显微构造标志,并据此判断是否伴随古地震事件。研究结果表明,松散沉积物中的断层在微观上表现为明显的滑移错动面、微破碎带、变形条带、泥质充填条带、黏土矿物集中和定向的带、铁质物集中的带以及碎屑颗粒集中和定向的带等。显微沉积学研究则表明,断层及其附近的地层中显微纹层常发生扰动现象,断层内样品碎屑颗粒粒度分布的粗尾段降低而细尾端增高,棱角状颗粒含量明显增加;扫描电镜分析表明这些碎屑颗粒有新的破裂产生,而分形研究获得了断层内样品较高的分维值(D约为2.5)。上述特征可以作为松散沉积物中宏观形迹不明断层的微观判断标志。此外,本研究还发现了与震击物的一些宏观标志,如球状体或枕状体、负荷构造、流体流、固体物质流以及有机物的悬浮等非常相似的微观特征。显然,它们可以作为判断古地震事件的微观标志。上述结果表明,微观分析是     

里下河古潟湖相软土基本工程特性与形成机理的关系

淮盐高速公路穿越的里下河地区,广泛分布有高含水量、高压缩性古潟湖相软土,工程性质很差,该层软土的工程性质与里下河古潟湖的形成机理密切相关。本文在对潟湖形成一般模式总结的基础上,结合苏北地区第四纪以来沉积环境及区域地质地貌变化情况,得出里下河古潟湖相软土的形成机理,并对淮沿高速公路盐线典型地段土样工程性质进行分析,根据土的工程性质的垂直变化,判断古潟湖相软土的分布情况,进而寻找古潟湖相软土工程性质与其形成机理之间的关系。     

青岛港液体化工码头区软基处理方法的对比分析研究

使用层次分析法,对青岛港港池浚深挖泥吹填形成的液体化工码头的软基处理方法进行优选。结合土质特点等因素,分区进行不同工艺的分析,建议真空预压法和强夯法进行地基处理。两种方法的地基处理资料对比表明,真空预压法为首选处理工艺。     

不同实验条件下软质岩石地基承载力分析

现行《岩土工程勘察规范》(GB50021-2001)及《建筑地基基础设计规范》(GB50007-2002)规定,确定岩石地基承载力特征值常用方法有取岩样作室内试验和现场原位载荷试验等。软质岩的岩石试样作室内试验时,因环境条件与实地有明显的差异,试验结果多不理想,现场静载试验在实际环境条件下进行,能更好地挖掘软质岩石地基承载力特征值的潜力,减少基础工程造价。     

自动气象站辅助软件在数据传输中的应用

针对自动气象站监测与数据传输中常出现的问题,开发了6个辅助软件用于自动气象站的数据采集和传输,以保证数据传输的完整性和准确性。     

加荷条件下软黏土的孔隙演化特征

开展上海软黏土的宏微观三轴剪切试验,研究软黏土受荷状态下孔隙的演化特征。结果表明：局部变形在加荷初期就开始发生。随着荷载的增加,细碎团聚体增多,孔隙不断地扩展,生成大的贯通孔隙,孔隙定向排列明显,剪切带形成。微观结构参数与剪应力比呈非线性正相关关系,最大孔隙面积、孔隙比、孔隙各向异性率及分布分维数在受荷初期缓慢地增大,后期快速增大。应变为8%时,最大各向异性率达到0.68,最大孔隙比为1.96。剪切带附近的微观结构参数都大于带外值。在受荷过程中,土的微观结构发生劣化,软黏土变形过程分为损伤开始、损伤发展剪切带形成和土体破坏3阶段,微观结构的劣化与土的宏观力学特性紧密相联系。