Transport process and mechanism of the Hongshiyan rock avalanche triggered by the 2014 Ludian earthquake,China

The Hongshiyan rock avalanche is a remarkable landslide disaster with approximately volume of 12?×?10⁶ m³, triggered by the 2014 Ms. 6.5 Ludian earthquake in Yunnan Province, China. This study conducted a comprehensive analysis by the model based on discrete element (DEM-based) numerical simulation to understand the transport process and mechanism for this rock avalanche. The simulation results showed that the transport process of the rock avalanche depends on the input seismic duration and motion. The average velocity of the rock avalanche sharply increases to peak value of 27 m/s and then gradually decreases to zero, and 64% and 36% of the total energy are dissipated by collision and friction, respectively. In this process, the progressions from simple disintegration along pre-existing discontinuities to fragmentation that creates new fracture surface are documented, and gradual increase of the fragmentation degree over time results in the decrease of fragment size and the formation of well-graded and narrower-interval gradation. This fragmentation evolution creates a conductive condition to the development of internal shear, and is closely associated with the dense flow regime that dominates the main body of the rock avalanche but presents discontinuous distribution along the flow thickness direction. In addition, further analyzing the simulated results indicates that more likely effects of fragmentation on mobility of rock avalanches depend on fragmentation-induced special flow structure, which makes a rock avalanche in a flow state with lower friction and lower energy consumption.

     

美国创新生态系统发展特征及启示

上海的城市创新生态系统建设已经走在全国的前列。但较高的商务成本一直以来是困扰创业者在沪创业的首要难题。同样高商务成本的美国纽约硅巷却扬长避短,低机会成本"抵充"高商务成本,吸引大批初创者入驻,并逐步演化形成完整、成熟的区域创新生态系统。本研究基于创新生态系统理论,从国家层面、地方层面对美国硅巷创新生态系统的发展特点和政府行为进行分析。在此基础上,本文针对上海深化建设全球科技创新中心面临的挑战,提出几点举措建议。     

Failure mechanism and stability analysis of the Zhenggang landslide in Yunnan Province of China using 3D particle flow code simulation

Based on the principle of 3D particle flow code, a numerical landslide run-out model is presented to simulate the failure process of the Zhenggang landslide (in southwestern China) under the effect of water after a rainfall. The relationship between the micro-mechanical parameters and the macro-shear strength of the grain material is determined through numerical calibrations. Then the rainfall effect is considered in numerical simulations and rain-induced sliding processes are performed, which help us to discuss the mechanism of deformation and failure of this landslide together with field observations. It shows the Zhenggang landslide would most likely be activated in Zone I and would gain momentum in Zone II. In order to prevent the potential disaster, a tailing dam is advised to be designed about 175 m downstream from the current landslide boundary of Zone II. Verified by field observations, the presented landslide model can reflect the failure mechanism after rainfall. It can also provide a method to predict the potential disaster and draft disaster prevention measures.     

从树轮纤维素δ13C序列看树木生长对大气CO2浓度变化的响应

在新疆昭苏树轮碳同位素组成研究的基础上，初步分析了近280a以来云杉内外CO2浓度比（Ci/Ca)，云杉内部CO2浓度（Ci)和水分利用效率（A／g)的变化，结果表明，在整个分析时段内Ci/Ca相对恒定在0．52左右，暗示树木生长对大气CO2浓度升高的基本响应策略；Ci和A/g都有较明显的升高趋势，说明可能有更多的碳被固定在树木之中，进一步分析表明，它们的这种趋势与大气CO2浓度变化有关，从另一个侧面证明了人类活动释放的碳有一部分被树木吸收。     

丹东市大气颗粒物质量浓度变化特征及其与气象要素的关系

利用2008-2017年大气颗粒物质量浓度资料和逐日地面气象观测资料,统计分析了丹东市大气颗粒物质量浓度时间变化特征及其与气象要素的关系。结果表明:2008-2017年丹东市大气颗粒物质量浓度年际变化具有一定的波动性,其中2015-2017年大气颗粒物污染状况持续改善明显;质量浓度月和季节变化特征明显,1月和12月最高、7月最低,冬季最高、夏季最低,非汛期显著高于汛期,供暖期显著高于非供暖期;非汛期大气颗粒物质量浓度超标日相较达标日,气温和能见度偏低,降水偏少,风速偏小;非汛期PM2.5、PM1质量浓度与相对湿度呈显著正相关,与风速呈显著负相关,汛期PM2.5、PM1质量浓度与风速呈显著负相关;PM2.5、PM1质量浓度春、秋、冬季与风速的负相关性最显著,冬季与相对湿度的正相关性也十分显著。     

地层渐进成拱对浅埋隧道上覆土压力影响研究

砂土及完整性较差、黏聚强度较小的破碎岩体中,浅埋隧道地层拱作用机制随地层变形发展而变化,受此影响隧道松动土压力也相应变化。常规方法忽略了地层拱不同阶段力学机制的不同,同时未考虑剪切面转动与大主应力旋转之间的相互关系,因此,不能解决浅埋隧道地层能否成拱、地层拱何时贯通至地表以及地层拱发展对隧道松动土压力影响等问题。针对这一情况,提出渐进地层拱力学模型以反映不同阶段地层拱的力学机制;其次,同时考虑主应力旋转、剪切面转动及二者相互关系,确定拱内土体应力分布;随后,优化了传统主应力偏转与地层差异沉降间的数学模型。在此基础上确定了渐进地层拱对隧道松动土压力的影响。改进方法结果与传统方法结果及试验结果的对比验证了改进方法的有效性与适用性。通过参数分析研究了隧道初始松动压力、随地层变形发展的松动压力以及地层拱贯通至地表时的极限变形等关键参数。最后,对下北山超大跨浅埋隧道的研究说明了改进方法的实用性。结论显示：（1）初始松动压力为初始松动区内土体重力,初始松动区范围不受覆跨比影响,而受地层强度影响,随内摩擦角增加而减小;（2）最大拱效应阶段以后,松动土压力随地层变形发展而增加,深埋、小跨度隧道（ ）增长速率较慢,反之较快;（3）极限变形随覆跨比、内摩擦角增加而增加,深埋、小跨度隧道地层拱效应更明显;（4）对于下北山隧道,初始地层拱存在,初始松动土压力为0.37 ,极限松动土压力为0.41 ,最终松动土压力为0.54 ,隧道变形应控制在5.7%以下避免地层拱贯通至地表。     

充气锚杆在砂土中的模型试验研究

为探讨充气锚杆的承载特性,通过建立室内试验模型,改变锚杆充气压力大小、埋设深度、土体密度、橡胶膜长度、厚度等条件,进行了一系列的抗拔试验,得到相应的荷载-位移曲线。研究结果表明：在影响充气锚杆抗拔承载力的诸多因素中,充气压力及土体密实度与承载力成一定倍数增长关系,是最显著的影响因素;其次是橡胶膜长度,成显著线性增长关系;充气锚杆的极限位移主要来自橡胶膜的弹塑性变形,反映了充气锚杆在抗拔过程中橡胶膜的力学行为;通过与常用锚杆的对比分析,得出充气锚杆的极限抗拔承载能力约是单锚片螺旋锚的4.3倍,是双锚片螺旋锚的1.9倍,其极限侧阻力约为一般注浆扩大头锚杆的2～4倍     

珠穆朗玛峰绒布冰川水文过程初步研究

2005年4月8日至10月11日对珠峰地区绒布河水文过程进行了连续6个多月的观测.结果表明:该地区的水文过程与温度有较好的相关性,6~8月3个月流量约占观测期内总流量的80%.对比该地区1959年和2005年的水文观测数据,发现2005年同期总径流量比1959年有较大幅度增加,6~8月3个月月均流量2005年较1959年分别增加69%、35%、14%.分析冰芯恢复的降水量资料和珠峰附近长时间序列气象数据,降水自1950年以来保持下降趋势,而气温却呈缓慢升高.气温升高是径流量增大的关键因素.2005年观测期内控制流域径流深为622 mm,径流模数为38.52 L·s^-1·km^-2.     

中国南极冰川学研究10 a回顾与展望

The study of Antarctic glaciology in China is reviewed with the emphasis on the past decade. Much progress has been achieved in the physical characteristics of the Antarctic ice sheet and caps and in the study of climatic and environmental records in Antarctic snow and ice. Through observations of snow profiles of numerous snow-pits and shallow cores in the Wilkes Land and Lambert Glacier basin and along the route of the 1990 International Trans-Antarctica Science Expedition (ITASE), the regional features of snow deposition and densification in Antarctica were revealed. The Nelson Island ice cap in South Shetland Islands was investigated in detail that　greatly enriched the knowledge of glaciers under a sub-Antarctic maritime climate. From the analyses of shallow ice cores and surface snow samples, in particular those taken along the ITASE route, the systematic data of stable isotopes, soluble impurities and heavy metal Pb in present precipitation in Antarctica has been obtained. Some suggestions are proposed through discussing the present hot points in the above fields.     

具有多种胞外酶的对虾肠道黏附菌的分离和鉴定

用对虾饲料培养基从健康凡纳滨对虾肠道分离出500株黏附细菌,以产淀粉酶、脂肪酶和蛋白酶能力为指标,筛选出产该3种消化酶的细菌90株,占总菌株的18%.对其中生长较快的69株进行16S rDNA 基因测序,确定其分类地位.结果显示,69株菌分别属于不动杆菌属(Acinetobacter)、芽孢杆菌属(Bacillus)、葡萄球菌属(Staphylococcus)、假交替单胞菌属(Pseudoalteromonas)、气单胞菌属(Aeromonas)、嗜盐单胞菌属(Halomonas)、利斯顿氏菌属(Listonella)、莫拉氏菌属(Moraxella)等,其中数量最多是芽胞杆菌属,占鉴定细菌总数的53.62%,数量最少是气单胞菌属和嗜盐单胞菌属,均占鉴定细菌总数的2.90%.表明对虾肠道黏附菌群中具有较多能分泌多种消化酶的细菌,可进一步开发为促进对虾消化功能的益生菌