盾构隧道下穿管道施工引起的管-土相互作用研究

采用Loganathan公式研究了盾构隧道下穿管道施工引起的地下管道处土体竖向位移,利用考虑土中剪力传递的Pasternak模型模拟管-土相互作用,运用修正Vlasov模型中的迭代流程计算出Pasternak模型的关键参数——弹性系数k与剪切系数gs。将计算结果与已有文献结果及工程监测数据进行对比,深入分析了迭代求解k、gs值的Pasternak模型与传统模型的计算差异,并进一步研究了土中剪力、管道与隧道的夹角、土体弹性模量及隧道半径的变化对管-土相互作用的影响。研究结果表明：迭代求解的k、gs值能提升Pasternak模型的精确度;土中剪力对管道竖向位移计算值的影响可达15.3%;随着管道与隧道夹角的减小,管道的竖向位移增大、弯矩减小;土体弹性模量与隧道半径的增大均会增加管道的竖向位移和弯矩。     

Crust and Upper Structure of Qinghai-Tibet Plateau and Its Adjacent Regions From Surface Waveform Inversion

CRUST AND UPPER STRUCTURE OF QINGHAI-TIBET PLATEAU AND ITS ADJACENT REGIONS FROM SURFACE WAVEFORM INVERSION     

中国大陆科学钻探主孔1200米构造柱及变形构造初步解析

在利用成象测井资料准确地恢复岩心空间位置的基础上，建立了位于江苏省东海县毛北村的中国大陆科学钻探主孔岩心1200m精细构造柱。划分了由榴辉岩与超镁铁质岩组成的第一岩性-构造单元及由副片麻岩夹榴辉岩与超镁铁质岩透镜体组成的第二岩性-构造单元，自上而下岩石的面理产状由向东陡倾变为向南东缓倾。第一岩性-构造单元的榴辉岩与超镁铁质岩是毛北榴辉岩杂岩体的组成部分，在榴辉岩中发现以南北向拉伸线理及由北往南的剪切指向为特征的超高压变质岩早期变形举止。位于第二岩性一构造单元下部(770-1130m深度)300多米厚的韧性剪切带是地表出露的毛北韧性剪切带在孔下的延伸，剪切应变及石英组构分析表明，在伴随的退变质角闪岩相一绿帘角闪岩相一绿片岩相的转换过程中，剪切应变由自SE往NW的“逆冲”转为NW向SE的正向滑移。结合钻孔围区地质，重塑了上部由毛北榴辉岩杂岩体与副片麻岩围岩组成的轴面向SE倾斜的同斜倒转褶皱系，以及下部为韧性剪切带的构造模型。钻孔验证了VSP地震反射剖面中850-1200m深度的强反射层与韧性剪切带相吻合。结合苏鲁超高压变质地体的折返构造的研究，提出该构造模型的成因与折返阶段超高压变质地体的斜向上的挤出及后折返阶段的穹隆形成有关。     

2020年7月西北太平洋和南海“空台”环流特征分析

2020年7月西北太平洋和南海出现了史无前例的“空台”事件。利用NCEP再分析数据集、中国气象局（CMA）台风最佳路径等资料研究了此次“空台”现象的大尺度环流背景及动力和热力学特征。使用台风潜在生成指数（DGPI）分析发现2020年7月大尺度环流背景不利于台风生成,环流系统的异常通过影响对流层垂直风切变和垂直运动限制了台风的活动。2020年7月马斯克林高压较常年明显偏西偏弱,导致索马里急流强度减弱,越赤道气流不活跃,菲律宾以东洋面和南海海域盛行一致的偏东气流,历史同期活跃在该区域的季风槽无法建立,从而不利于热带扰动的生成。北半球极涡主体偏向西半球一侧,影响东半球冷空气势力较弱,副热带高压位置偏西;南亚高压较历史同期偏强且偏东,其东侧强盛的偏东气流将洋中槽截断,在西北太平洋区域出现反气旋性环流,该区域下沉气流增强,导致副热带高压强度增强,对流层中层强烈的下沉气流抑制了台风的生成和发展。此外,受中高层环流系统异常的影响,7月菲律宾吕宋岛以东洋面和南海地区环境垂直风切变较常年偏高2～4 m/s,南海部分海域偏高达4～8 m/s,同时该区域内异常偏强的下沉气流导致对流层低层相对湿度偏低,大气层...     

Evaluating a process‐based model for use in streambank stabilization: insights on the Bank Stability and Toe Erosion Model (BSTEM)

Streambank retreat is a complex cyclical process involving subaerial processes, fluvial erosion, seepage erosion, and geotechnical failures and is driven by several soil properties that themselves are temporally and spatially variable. Therefore, it can be extremely challenging to predict and model the erosion and consequent retreat of streambanks. However, modeling streambank retreat has many important applications, including the design and assessment of mitigation strategies for stream revitalization and stabilization. In order to highlight the current complexities of modeling streambank retreat and to suggest future research areas, this paper reviewed one of the most comprehensive streambank retreat models available, the Bank Stability and Toe Erosion Model (BSTEM), which has recently been integrated with several popular hydrodynamic and sediment transport models including the Hydrologic Engineering Center's River Analysis System (HEC‐RAS). The objectives of this paper were to: (i) comprehensively review studies that have utilized BSTEM and report their findings, (ii) address the limitations of the model so that it can be applied appropriately in its current form, and (iii) suggest directions of research that will help make the model a more useful tool in future applications. The paper includes an extensive overview of peer reviewed studies to guide future users of BSTEM. The review demonstrated that the model needs further testing and evaluation outside of the central United States. Also, further development is needed in terms of accounting for spatial and temporal variability in geotechnical and fluvial erodibility parameters, incorporating subaerial processes, and accounting for the influence of riparian vegetation on streambank pore‐water pressure dynamics, applied shear stress, and erodibility parameters. Copyright © 2016 John Wiley & Sons, Ltd.     

砂土的抗剪强度与干密度的曲线拟合

利用曲线拟合的最小二乘法原理，确定砂土在某垂直压力下的抗剪强度与干密度的关系，并绘制曲线图，可避免人工处理数据的随意性，减小了误差。     

Analysis of threshold and incipient conditions for sediment movement

Prediction of threshold conditions and incipient motion is the essential issue for the study of sediment transport. This work compares existing empirical threshold curves proposed for Shields diagram, a method based on the concept of probability of sediment movement, and an empirical method based on movability number. These methods are used to predict the incipient motion conditions for experimental runs taken from various studies. Most of the experimental data, used in this work, have not been used before in derivation of alternative formulations for Shields diagram and other methods. The empirical threshold curves based on the Shields entrainment function was the least successful at predicting the measured incipient motion conditions, while the use of the movability number gives good predictions of critical shear velocity compared with experimental data.     

陕西小秦岭华阳川韧性剪切带的特征 及其区域构造意义

陕西小秦岭华阳川韧性剪切带发育在新太古界太华群之中,野外调研和显微构造观察结果表明,该韧性剪切带是由构造片岩、眼球状片麻岩组成的深层次韧性剪切带,具有逆冲兼左行走滑的斜冲特征。对韧性剪切带构造片岩黑云母进行^40Ar／^39Ar同位素定年,获得坪年龄为419M±0．6Ma,反等时线年龄为417Ma±0．8Ma。认为华阳川韧性剪切带及其相应的小秦岭区域主导构造变形是发生于419Ma左右的秦岭加里东事件的结果。     

Evaluation of stress strain non-uniformities in the laboratory direct simple shear test specimens using 3D discrete element analysis

The direct simple shear (DSS) device is one of the commonly used laboratory element testing tools to characterize the shear behaviour of soil. The interpretation of results from an element test requires understanding of the degree of stress and strain non-uniformities in a given test specimen. So far, studies on stress and strain non-uniformities in the DSS test have been conducted using direct boundary measurements of stresses in laboratory specimens supported by a continuum based analytical approach. Discrete element modelling now provides a means of modelling the soil behaviour in a realistic manner using a particulate approach. Accordingly, the performance of a DSS specimen was modelled using discrete element modelling with emphasis on assessing stress and strain non-uniformities in the specimen during shearing. The approach allowed for the numerical determination of stresses not only at the boundaries, but also within the DSS specimen. It was shown that mobilised stress ratio distribution throughout the shearing phase for the majority of specimen volume at locations near the central planes parallel and perpendicular to the direction of shearing is fairly uniform. Finally, it was noted that the potential for particle slippage at locations near the specimen centre can result in non-uniform shear strain distributions.     

暖切变型江淮梅雨锋结构及其形成和维持机制

对在1991年7月上旬特别稳定的梅雨形势下持续10天的特大暴雨期作了合成和典型过程研究,并进一步探讨了暖切变型江淮梅雨锋天气系统模型。它在自由大气层表现为结构竖立的相当正压切变线和一种不同于经典地转动量近似的带状准二维运动场。边界层的浅层锋生倾斜环流以及偏于切变线轴以南的Ekman抽吸与自由大气层中基本上由积云对流加热驱动的竖直环流相互依存和耦合,造成持续的大暴雨。这种系统的初生和中断后复苏的机制可能是由斜压性极弱的副热带高空东移的短波扰动在低层“湿度锋”带紧南侧触发导致的一种带状CISK。