Critical state behaviour of weakly bonded soil in drained state

A series of consolidated drained triaxial test was performed on weakly bonded soils that were artificially prepared by mixing sand (87%) and kaolin (13%). To create weakly bond strength, samples were fired at 500°C for 5 h. A critical state (CS) concept was used to interpret the results in order to describe the behaviour of the studied soil. Defining the CS is not always straightforward. Several tests showed changing in deviator stress q and volumetric strain ε_v up to the end of tests. Hence, defining the CS requires careful assessments on q–ε_a, Δu–ε_a, q–p′ and v–ln p′ spaces which were performed. A ‘discontinuity’ approach was applied to position the CS on dilatant path in v–ln p′ spaces after considering stress-strain and volumetric strain curves. The critical state line in a v–ln p? space from bonded samples exhibited differences to the destructured samples. This suggests that the influence of cementation bond is substantially clear at lower stresses but as stresses increase beyond the stress yield, cementation degradation becomes more significant. The effect of bonding can be clearly visualised from the normalisation of the stress paths of destructured and bonded samples.     

Predicting the reproduction strategies of several microalgae through their genome sequences

Documenting the sex and sexual reproduction of the microalgae is very difficult, as most of the results are based on the microscopic observation that can be heavily influenced by genetic, physiological and environmental conditions. Understanding the reproduction strategy of some microalgae is required to breed them in large scale culture industry. Instead of direct observation of sex and sexual reproduction under microscope, the whole set or the majority of core meiosis genes may evidence the sex and sexual reproduction in the unicellular algae, as the meiosis is necessary for maintaining the genomic stability and the advantages of genetic recombination. So far, the available genome sequences and bioinformatic tools(in this study, homolog searching and phylogenetic analysis) allow us to propose that at least 20 core meiosis genes(among them ≥6 must be meiosis specific) are enough for an alga to maintain its sexual reproduction. According to this assumption and the genome sequences, it is possible that sexual reproduction was carried out by Micromonas pusilla and Cyanidioschyzon merolae, while asexual reproduction was adopted by Bigelowiella natans, Guillardia theta, Nannochloropsis gaditana, N. oceanica, Chlorella variablis, Phaeodactylum tricornutum and Thalassiosira pseudonana. This understanding will facilitate the breeding trials of some economic microalgae(e.g., N. gaditana, N. oceanica, C. variablis and P. tricornutum). However, the reproduction strategies of these microalgae need to be proved by further biological experiments.     

近40年夏季江苏引发暴雨的江淮气旋统计分析

使用Lu(2017)改进的温带气旋识别和追踪方法得出的江淮气旋资料,统计分析了近40年夏季江苏引发暴雨的江淮气旋概况、路径、形势特征和对应暴雨的主要落区。结果表明,夏季江淮气旋造成江苏暴雨的频次空间上在江淮之间最多,并向北和向南依次递减;时间上在6月最多,约占该月暴雨总次数的1/3。致暴江淮气旋暴雨落区与江淮气旋的路径有一定的对应关系,在淮北和江淮地区,暴雨在致暴江淮气旋过境地区均匀分布,但在苏南地区,暴雨主要集中在苏南的中西部。致暴江淮气旋天气形势可分为偏西气流型和低槽型两类,其中低槽型出现的次数约为偏西气流型的2倍。偏西气流型暴雨区位于500hPa南侧暖湿的西南气流与北侧西北气流的过渡带中,低槽型暴雨区位于槽前西南气流中。850hPa两种类型基本相似,都为闭合的低涡,且低涡位置相比于700hPa明显南移。江淮和苏南地区的暴雨落区大都位于700和850hPa低涡中心的南侧、700hPa急流的北部和850hPa急流的北侧。偏西气流型和低槽型造成的暴雨范围基本相当,但低槽型产生的暴雨量要大于偏西气流型。     

中国花岗伟晶岩型锂矿特征和研究进展

花岗伟晶岩型锂矿是中国锂资源的重要类型之一。本文基于全国87处花岗伟晶岩型锂矿研究资料,通过与全球典型伟晶岩型锂矿的对比分析,梳理总结中国花岗伟晶岩型锂矿的时空分布规律、矿石矿物组合特征、成矿成岩温压条件、演化历史和锂同位素分馏特征,以期为今后找矿工作提供理论依据。研究表明中国花岗伟晶岩锂矿空间分布相对集中,主要分布在8个锂成矿带,主成矿期为三叠纪;含锂矿物相与花岗岩-伟晶岩体系中的H_2O、P、F和Li等挥发性元素密切相关;与国外典型花岗伟晶岩锂矿相比,中国大型-超大型伟晶岩锂矿具有成矿温度相似和成矿压力较大的特征;不同于以Harding伟晶岩为代表的侵位后P-T两阶段演化轨迹,中国花岗伟晶岩锂矿存在以川西扎乌龙为代表的单阶段快速降温降压型演化轨迹;结晶分异是花岗伟晶岩最可能的岩石成因,该地质过程中锂元素和重锂同位素富集于花岗伟晶岩;未矿化伟晶岩全岩比锂辉石矿化伟晶岩全岩更富轻锂同位素的特征表明锂成矿过程发生在流体出溶之后。     

Determination and application of path duration of seismic ground motions based on the K-NET data in Sagami Bay,Japan

Duration models are one of the important parameters in ground-motion simulations. This model varies in different study areas, and plays a critical role in nonlinear structural response analysis. Currently, available empirical models are being globally used in ground-motion simulations, with limited research focusing on path duration in specific regions. In this study, we collected 6,486 sets of three-component strong-motion records from 29 K-NET stations in the Sagami Bay, Japan, and its surrounding areas between January 2000 to October 2018. We extracted the effective duration of 386 pieces of ground-motion records by manually picking up the S-wave arrival time and calculating the significant duration. We then obtained the path duration model of the study area based on the empirical equation of dynamic corner frequency and source duration of [7]. Compared with the results of the available empirical models, the Fourier spectrum of the simulated ground motion from our effective duration model showed higher accuracy in the long-term range, with less fitting residuals. This path duration model was then applied to simulate two earthquakes of M_W5.4 and M_W6.2, respectively, in the region using the stochastic finite-fault method with a set of reliable source, path, and site parameters determined for the study area. The simulation results of most stations fit well with observation records in the 0–30 Hz frequency band. For the M_W5.4 earthquake, the simulated ground motions at KNG005/KNG010/SZO008 stations were relatively weak in the mid to high frequency band (1–30 Hz) because the quality factor and geometric diffusion model used in the simulation were the averages of the entire Sagami Bay region, causing a bias in the results of a few stations owing to local crustal velocity anomalies and topographic effects. For the M_W6.2 earthquake, the simulated ground motions were relatively weak at all SZO and TKY stations, mainly because of the close distance from these stations to the epicenter and the complex seismic-wave propagation paths. The analysis suggests that the differences between the simulation results of the two earthquakes were mainly related to complex geological conditions and seismic-wave propagation paths.     

地质勘查行业管理制度变迁的路径依赖与创新选择

根据制度变迁和路径依赖理论来分析我国地质勘查行业管理制度变迁中的路径依赖现象,发现我国地质勘查行业管理制度变迁具有强制性、渐进性、滞后性和单一性特征。并因不良惯性的路径依赖陷入非效率的锁定状态,主要表现为：方式手段上重审批轻监管、管理理念上重管理轻服务、体制机制上重政府主导轻市场参与。分析认为,原有管理制度的惯性作用和改革的阻力与动力,是影响地质勘查行业管理制度变迁中路径依赖性的主要因素。地质勘查行业管理改革创新需要从降低改革阻力、克服制度惯性、增加改革动力等三个方面来打破原有管理制度的锁定效应。     

变质地质学研究中的一些困难问题

变质地质学研究中,首先需要准确判明变质过程是属于多期或单期、多峰或单峰变质作用。研究中应该对同一研究区不同类型的变质岩石开展综合研究,查明各种变质反应结构,以期对变质反应结构的解释尽可能准确,并对变质反应进行定量论证。同一变质岩内前、后两个世代变质矿物组合之间,并不存在所谓的热力学局部平衡。在应用方面,矿物温度计与压力计属于反演方法,热力学视剖面图模拟属于正演方法。本文指出了它们之间的相同之处和各种区别。众所周知,目前反演出的变质作用压力并无方向性,差异应力对总应力的贡献尚不明朗。最好根据同一视域或同一块变质岩石,来反演变质作用P-T-t轨迹。实际上,P-T-t轨迹一般不应该是圆滑的曲线,其构造意义的解释也还存在不确定性。同一地区变质作用PT条件的突变、P-T-t轨迹的明显差异,表明地质体之间存在断层接触关系。变形作用与变质作用的耦合研究需要加强,变质作用的定年也不能仅仅局限于变质副矿物。特别值得注意的是,同一造山带内范围有限的地域,也未必属于同一变质相系。     

莫116井区水平井钻井设计优化与应用

莫116井区在水平井钻井施工过程中,面临着“缩、卡、塌、漏、喷、硬”等难题,为避免井下复杂事故、缩减钻井周期、降低作业风险,在该区开展了水平井优化设计与轨迹优化控制技术研究工作。通过井区已钻井资料论证分析,针对性地对井身结构和井眼轨迹控制提出了优化方案;根据前期实钻情况和钻柱力学分析,优化了水平井钻井钻具组合和钻井参数;通过优化泥浆体系,解决定向作业井段了井壁稳定性差、定向施工摩阻大、粘附卡钻几率高等问题。通过对上述研究成果的现场应用,实现了水平井优快钻井目标,二开定向段和三开井段平均机械钻速相比优化前水平分别提高27%、30%,其中M614等井实现了“一趟钻”完成了水平段钻进目标。     

基于CBR和GIS的海上溢油应急资源配置方案研究

传统溢油应急资源配置方案的制定主要依靠现场工作人员的经验,存在很大的主观性,方案制定缺乏科学理论支持。将CBR(案例推理技术)以及GIS技术引入到溢油应急资源配置方案的制定中,解决应急资源配置方案制定过程中资源种类、数量确定以及海陆资源运输等问题。对CBR涉及的案例表示、案例检索、案例调整和案例学习等核心问题进行系统研究,综合考虑GIS技术支持下的陆海一体化资源运输,建立溢油应急资源配置专家系统。研究表明,该系统能帮助现场工作人员快速制定溢油应急资源配置方案,为溢油应急提供科学合理建议。     

加权路网分层的最优路径计算

为了弥补传统分层算法在平面最短路径计算中对出行者出行习惯考虑不充分的缺陷,该文提出了一种分层算法的优化策略,即加权路网分层:首先运用层次分析法计算选定的道路属性的权值,对道路属性权值进行组合相加,进而确定道路权值,然后根据确定的分层阈值对路网进行分层,最后运用双向A*算法进行试验,并与传统的分层路网计算结果进行比较。实验结果表明,加权分层策略充分考虑了出行者的出行习惯,能够适用于路径导航中的最优路径计算,具有可行性与实用性。