干湿循环条件下红砂岩软弱夹层微结构与剪切强度的关联性     

陈宾  周乐意  赵延林  王智超  晁代杰  贾古宁 《岩土力学》2018,39(5):1633-1642

极旱极涝频繁交替的极端气候事件会加剧岩土风化,降低强度,影响岩土工程结构稳定。采用直剪试验和扫描电镜技术,研究了对顺层红砂岩边坡稳定性起控制作用的软弱夹层在常温状态、干湿循环条件下（60℃风干）的力学特性及微观结构变化规律,通过相关分析、逐步回归方法得到了影响强度的微结构显著变量,构建了反映二者关联性的回归方程。研究表明：红砂岩软弱夹层剪切强度及黏聚力在1～5次循环过程中急剧降低,5次后变化趋缓,循环次数对内摩擦角变化影响微小;干湿循环次数增加,平均面积、平均直径、平均周长、定向概率熵等4个微结构参数减小,并与黏聚力呈现正相关关系;颗粒个数、平均形状系数、形态分布分形维数3个微观参数与黏聚力呈现负相关关系;分析认为,干湿循环过程中宏观力学特性蜕化及微观结构参数变化之间显著相关,干湿循环造成的岩土颗粒胀缩、碎裂、结构破坏是导致红砂岩软弱夹层剪切强度蜕化的主要原因。  相似文献   

Variations in Amplitudes and Wave Energy along the Energy Dispersion Paths for Rossby Waves in the Quasigeostrophic Barotropic Model     

Yaokun LI  Jiping CHAO  Yanyan KANG 《大气科学进展》2022,39(6):876-888

Variations in wave energy and amplitude for Rossby waves are investigated by solving the wave energy equation for the quasigeostrophic barotropic potential vorticity model.The results suggest that compared with rays in the nondivergent barotropic model,rays in the divergent model can have enhanced meridional and zonal propagation,accompanied by a more dramatic variability in both wave energy and amplitude,which is caused by introducing the divergence effect of the free surface in the quasigeostrophic model.For rays propagating in a region enclosed by a turning latitude and a critical latitude,the wave energy approaches the maximum value inside the region,while the amplitude approaches the maximum at the turning latitude.Waves can develop when both the wave energy and amplitude increase.For rays propagating in a region enclosed by two turning latitudes,the wave energy approaches the minimum value at one turning latitude and the maximum value at the other latitude,while the total wavenumber approaches the maximum value inside the region.The resulting amplitude increases if the total wavenumber decreases or the wave energy increases more significantly and decreases if the total wavenumber increases or the wave energy decreases more significantly.The matched roles of the energy from the basic flow and the divergence of the group velocity contribute to the slightly oscillating wave energy,which causes a slightly oscillating amplitude as well as the slightly oscillating total wavenumber.  相似文献   

冲绳海槽海底地形的补偿模式研究Ⅰ.理论均衡响应函数的计算   总被引：1，自引：0，他引：1  

刘保华  吴金龙  辛柏森  彭超 《海洋学报》1998,20(6):70-75

本文从区域补偿和实验均衡出发,导出了上部负载和下部负载相关时理论均衡响应函数的计算公式,计算了弹性板有效厚度不同以及上部负载和下部负载的比例不同时的理论均衡响应函数曲线,并对曲线形态进行了初步的讨论．  相似文献   

春季中华哲水蚤在不同海湾或河口对环境的适应性          下载免费PDF全文

杨杰青  陈渊戈  张冬融  周进  晁敏  史赟荣 《应用海洋学学报》2023,42(3):460-468

为探究南黄海和东海不同海域春季中华哲水蚤（Calanus sinicus）分布主要受何种环境因子影响及对各环境因子的响应差异,利用2020年春季南黄海海州湾至长江口以北海域和东海长江口海域、三门湾邻近海域、福建中部近岸海域调查数据,基于广义可加非线性模型（GAMs）分析了中华哲水蚤与环境因子的关系。结果表明：海州湾至长江口以北海域中华哲水蚤主要受温度、溶解氧、化学需氧量、Chl a、pH和氨氮的影响。其密度随着温度的增加呈一个波谷曲线变动,温度在14 ℃时密度最低;随着溶解氧的增加其密度呈一个波谷曲线变动,溶解氧含量在10 mg/L时中华哲水蚤密度最低;随化学需氧量增加其密度波动变化;随着Chl a浓度的增加其密度先下降再呈波动上升;随着pH的增加中华哲水蚤密度逐渐降低;随着氨氮浓度的增加中华哲水蚤密度逐渐增加。长江口海域中华哲水蚤主要受盐度、水深、化学需氧量和活性磷酸盐影响,随盐度和水深的增加其密度逐渐增加;随化学需氧量和活性磷酸盐浓度增加其密度逐渐降低。三门湾邻近海域中华哲水蚤主要受盐度、pH和透明度影响,随盐度的增加其密度逐渐增加;随pH的增加其密度逐渐降低;随透明度的增加其密度先降低后增加,透明度在1.2 m左右其密度最低。福建中部近岸海域中华哲水蚤主要受水深、透明度、温度和溶解氧影响,随水深的增加,其密度逐渐增加;随透明度的增加其密度波动增加;随温度和溶解氧的增加其密度逐渐降低。  相似文献   

福建深沪湾海底古森林遗迹自然保护区优化调整对策研究          下载免费PDF全文

颜利  蒋金龙  巫建伟 《海洋开发与管理》2021,38(5):85-91

我国自然保护地的建设和发展经历了60余年,仍然存在重叠设置、多头管理、边界不清、权责不明,以及自然保护地保护与当地经济发展矛盾突出等问题,亟须对现有自然保护地管理体制、机制进行改革,建立自然生态系统保护的新体制、新机制。因此现有自然保护地体系优化调整理论和技术方法研究成为近期生态环境保护研究的热点和重点。文章剖析了福建深沪湾海底古森林遗迹自然保护区存在的问题。提出自然保护区的优化调整对策,包括：厘清自然保护区与地质公园的关系;逐步解决历史遗留问题;妥善处理自然保护区与海水养殖之间的矛盾;优化自然保护区向陆一侧边界线;对自然保护区实行分区管控政策等。调整后的深沪湾海底古森林遗迹自然保护区面积为24.66 km2,比原自然保护区面积减少1.17 km2。其中：核心保护区面积为7 km2,一般控制区面积为17.66 km2。为编制深沪湾海底古森林遗迹自然保护区优化调整方案和历史遗迹自然保护区管理提供参考。  相似文献   

A Research on the 2014 Wenzhou M4.2 Earthquake in the Shanxi Reservoir     

Zou Zhenxuan  Ma Zhijiang  Zhou Xinmin  Zhang Fan  Li Jun  Li Jinlong 《中国地震研究》2017,31(4):455-462

Complete records of more than 3,000 earthquake events in the Shanxi, Wenzhou reservoir earthquake sequence were recorded from August to November,2014 by the high-density,high-resolution monitoring stations of the Zhejiang Regional Digital Seismic Network and the reservoir earthquake monitoring network,with a maximum magnitude of M4. 2. Based on 3-D epicenter location, focal mechanism solutions, and in combination with the geological and tectonic characteristics of the reservoir area,the earthquake sequence is discussed in this paper. The linear fitting of the Hypo SAT location results show that the main shock occurred in the NW trending fault and the earthquake sequence is concentrated in bands along the active faults,with a strike of305 °,dipping SW with dip angle of 85 °. By using P-wave first motion symbols, we obtained the average focal mechanism of M ≥ 3. 5 earthquakes,with a strike 308 ° and dip 84 ° for nodal plane II. The field geological survey and research show that the strike,dip and rake of nodal plane II are roughly consistent with the occurrence of the Shuangxi-Jiaoxi fault. The comprehensive analysis reveals that the NW-trending Shuangxi-Jiaoxi fault is the seismogenic structure of the earthquakes.  相似文献   

全球地震灾害发展趋势综述     

贾晗曦  林均岐  刘金龙 《震灾防御技术》2019,14(4):821-828

基于EM-DAT（OFDA/CRED）国际灾害数据库及美国地质勘探局（USGS）给出的数据,提取全球1970—2018年干旱、地震、极端温度、极端气候、洪水、滑坡、火山活动、火灾和块体运动9种自然灾害的相关数据,并进行综合分析,着重分析死亡人数和经济损失。分析结果表明,21世纪以来地震灾害造成的损失最大。此外,2000—2017年全球重大地震尤其是9次特大地震的分析结果显示,可有效减轻地震灾害损失的措施至少包括建立地震预警机制、建设韧性城乡、建立完善的风险排查机制。  相似文献   

The characteristics of the structure,strain and kinematic vorticity of the Wulian detachment fault zone,Shandong Peninsula,China     

Jinlong NI  Junlai LIU  Yujie SUN  Xiaoxiao SHI  Shen LI 《中国科学:地球科学(英文版)》2019,(9)

As one of the vital tectonic units of the Wulian Metamorphic Core Complex(MCC), the Wulian detachment fault zone(WDFZ), which developed in the Jiaodong peninsula, separates the lower plate of the ultrahigh pressure(UHP) metamorphic rocks in the Sulu orogenic belt from the upper plate of the early Cretaceous Zhucheng basin and the basin basement. The fault zone generally strikes NNE with a dip in the west along the southern portion of the MCC and strikes NE with a dip in the WNWalong the northern portion. The fault zone displays a wavy-tile-shaped extension on the plane, principally composed of the fault breccias and mylonite and transits downward to the mylonitic gneiss. As a whole, the detachment fault zone shows a top-towest or a WNW extension. By calculating the harmonic mean, we obtain a Flynn index K of 0.98–2.0, and the mean value is approximately 1.35 in the fault zone. According to the polar Mohr construction, the extensional crenulation cleavage, the RS/θ,and the quartz C-axial fabric methods, we acquire mean kinematic vorticity values of 0.64–0.97, 0.76–0.93, 0.6–0.92, and 0.63–0.98 with mean values of 0.83, 0.80, 0.78 and 0.86, respectively, for mylonite and promylonite. The strain measurement results and the kinematic vorticity values indicate that the WDFZ is a normal ductile shear zone developed in the extensional setting.The kinematic track shows that the kinematic vorticity value decreases gradually from the NW to the SE as a whole. A simple shear dominates in the middle and upper parts of the shear zone, which is reflected by a higher vorticity value(0.75, up to 0.98),a low thinning rate and a lower K value. In contrast, toward the footwall, the pure shear is increased significantly, showing a lower vorticity value(0.70, low to 0.64), a relatively high thinning rate and a higher K value. Combined with the geotectonic background, the development and evolution of the WDFZ should respond to lithospheric thinning and the destruction of the North China Craton(NCC). As a result, the WDFZ can be defined as a thinning normal shear zone developed in the extension tectonic setting and the combined result of the simple shear caused by the crust extension and pure shear led by the rapid uplift of the footwall and magmatic upwelling.  相似文献   

Progress and performance evaluation of BeiDou global navigation satellite system: Data analysis based on BDS-3 demonstration system   总被引：5，自引：0，他引：5  

Yuanxi Yang  Yangyin Xu  Jinlong Li  Cheng Yang 《中国科学:地球科学(英文版)》2018,61(5):614-624

The first two Medium Earth Orbit (MEO) satellites of the third generation of BeiDou satellite navigation System (BDS-3) were successfully launched on November 5, 2017. This historical launch starts the new era of the global navigation satellite system of BeiDou. Before the first two satellites of BDS-3, a demonstration system for BDS-3 with five satellites, including two Inclined Geosynchronous Orbit satellites (IGSO) and three MEO satellites, was established between 2015 and 2016 for testing the new payloads, new designed signals and new techniques. In the demonstration system, the new S frequency signal and satellite hydrogen clock as well as inter-satellite link (ISL) based on Ka-band signals with time-division multiple addresses (TDMA) were tested. This paper mainly analyzes the performances of the demonstration system, including the signalto- noise ratios, pseudorange errors and the multipath errors of the civilian signals of BDS-3. The qualities of signals in space, time synchronization and timing precision were tested as well. Most of the performances were compared with those of the regional BeiDou satellite navigation system (BDS-2). At last, the performances of positioning, navigation and timing (PNT) of the future BeiDou global system (BDS-3) were evaluated based on the signal quality of the present demonstration satellite system.  相似文献   

西洞庭湖季节性淹水和植被类型对温室气体排放通量的影响     

郭佳  晁碧霄  张颖  雷光春  王玉玉 《湖泊科学》2020,32(3):726-734

植被类型及淹水带来的干湿交替过程是影响温室气体排放的重要因素.本文通过原状土柱模拟实验,模拟西洞庭湖水文节律变化对不同土壤—植被系统温室气体排放的影响.利用静态箱—气相色谱法研究不同植被—土壤类型(芦苇湿地、灰化苔草湿地和刚砍伐的杨树林湿地)在季节性淹水条件下的CO_2、CH_4和N_2O的排放通量变化,并探讨了在水位变化的情况下,不同植被—土壤类型对全球增温潜势的贡献.结果表明:在不同的水文条件下,芦苇湿地的CO_2排放通量均显著高于苔草和杨树林湿地;淹水过程导致3种植被类型覆盖湿地CO_2排放通量显著降低,甲烷排放通量升高,其中芦苇湿地CH_4排放通量升高显著,苔草和杨树林湿地CH_4排放通量升高不明显;水文变化及植被类型对N_2O排放通量的影响不显著;不同植被类型湿地对全球增温潜势的贡献为:芦苇杨树林苔草,分别为16191.3、3405.6和1883.1 kg/hm~2.本研究结果表明在西洞庭湖湿地恢复过程中,不再人为增大芦苇湿地面积,将杨树林湿地恢复为苔草湿地,更有利于降低湿地恢复过程中温室气体的排放.  相似文献