In situ X-ray micro-CT for investigation of damage evolution in black shale under uniaxial compression     

Y. Wang  Z. Q. Hou  Y. Z. Hu 《Environmental Earth Sciences》2018,77(20):717

Crack damage evolution of shale is crucial to the hydraulic fracturing treatment and engineering stability. Although many effects have been done on the macroscopic characteristics of shale, yet the microscopic failure mechanism is not well understood. A uniaxial compressive test on black shale was conducted under topographic monitoring using in situ X-ray micro-tomography (µCT). A series of high-resolution reconstruction images were obtained by carrying out CT scans at six key points throughout the test to obtain the internal structure of shale sample. In addition, the CT values for the purpose of crack damage evolution in shale were identified. Clear 2D/3D CT images, CT value analysis and image segmentation analysis reveal that the sample experiences compression, damage, cracking, crack propagation, and collapse stages. Crack geometry and distribution in the shale sample is visualized by rendered CT images, and a combined tension and shear failure mode is observed from the fracture rose diagram. This work suggests that formation and propagation of fractures are influenced by the stratified structure and weak cementation medium between layers.  相似文献   

Bioacoustic application on fisheries management in an artificial reefs’ ecological reserve of Bohai Gulf China     

Lei Zeng  Zhenzhao Tang  Pimao Chen  Chunqiang Hou  Guobao Chen 《Environmental Earth Sciences》2018,77(21):728

Various techniques have been used in marine fishery resources assessment. Among those, acoustic techniques have high efficiency and wide adaptability, and are environment friendly. Therefore, acoustic techniques played a key/indispensable role in the field of ecosystem-based fishery management. Acoustic surveys were conducted during the wet (May) and dry (November) seasons in 2016 in the artificial reefs ecological reserve of Bohai Gulf and a nearby control region to understand the current situation of fishery resources and explore the effectiveness of underwater artificial constructions by a dual-frequency identification sonar (DIDSON) and a scientific split-beam echosounder (120 KHz, Simrad EY60). Fish densities in various seasons and regions showed significant differences and interaction, with a maximum value of 358020.34 ind/n.mile² in the artificial reefs’ region and a minimum value of 71898.35 ind/n.mile² in the control region during the wet season. Fish densities in defined parallel transects revealed a roughly southward migration trend of small-size individuals from wet season to dry season. Single echo detections in the artificial reefs region demonstrated a wider target strength (TS) range (? 60 ~ ? 30 dB vs ? 60 ~ ? 51 dB) and higher mean TS values (? 55.87 dB vs ? 58.31 dB) than the control region both in the wet and dry seasons, which indicated a more complicated and stable fish community structure in the artificial reefs area. The vertical distribution of single echo detections tracked by the echoview post-processing system showed an apparent downward gathering effect. A positive correlation between TS and water depth was discovered from Pearson correlation analysis in the artificial reefs region during the dry season.  相似文献   

Light transmission method to explore the migration and distribution of Cr(VI) in a sandy aquifer     

Rui Zhou  He Sun  Zhimin Hou  Ying Guo  Hejun Ren 《Environmental Earth Sciences》2018,77(6):255

The migration and distribution of contaminants in heterogeneous aquifers are mostly investigated through numerical simulations. They are rarely examined through experimental simulations because of sampling difficulties. In this study, we used the light transmission method (LTM) to explore the migration and distribution of hexavalent chromium [Cr(VI)] in homogeneous sandy aquifers with or without a low-permeability bottom and lens (heterogeneous aquifer). Experimental phenomena were observed via images obtained with a high-power light source. The migration distances of pollution plume were also monitored. Under heterogeneous conditions, low-permeability aquifer materials considerably inhibited the migration of Cr(VI) and altered the Cr(VI) migration rate of horizontal and vertical plumes spread to a certain extent. Common horizontal and vertical migration curve equations in all three conditions were also obtained through distance–time curve fitting. The difference between high- and low-concentration zones was accurately revealed, and the experimental phenomenon was further explained. The proposed method could be used for the qualitative investigation and visualization of the migration and distribution of Cr(VI).  相似文献   

Detection of leakage paths at the Wanyao dam body in Southwest China by hydrochemical analysis and tracer testing     

Yong Huang  Xiaolan Hou  Zhimin Fu  Jinguo Wang 《Environmental Earth Sciences》2018,77(23):791

Leakage at the Wanyao dam body was studied using a combined approach of field exploration, hydrochemical analysis and tracer testing. The objective of study was to determine the location of the water leakage paths at the dam. A hydraulic connection was observed between exploration boreholes of dam crest and drain holes at drainage gallery during the period of drilling. This connection shows that there were some defects in the dam. The hydrochemical compositions and characteristics of the water samples involved the main anions and cations, total dissolved solids, electrical conductivity, pH and water temperature which were analyzed and evaluated by correlation and cluster analysis. The results indicated that a close hydraulic connection existed between water from the dam body and reservoir water, particularly reservoir water from Sections III and IX. Tracer testing results demonstrated further existence of leakage paths between reservoir water and Sections III and IX. Also, there were multiple leakage paths in Section IX compared with a single path of Section III. Furthermore, the leakage location of upstream concrete faces in the vertical and horizontal directions was determined accurately with the measured electrical conductivity of receiving points. The experimental data provide a strong foundation and basis for maintaining and reinforcing the dam.  相似文献   

Geochemical characteristics and analysis of crude-oil source in the deep-water area of the Baiyun Sag,South China Sea     

Dashuang He  Dujie Hou  Tao Chen 《Russian Geology and Geophysics》2018,59(5):499-511

In the Baiyun Sag, the oil relationship with possible source rocks is complicated, and little research on oil sources in the area has been performed. In this paper, geochemical studies of carbon isotopes, biomarkers, paleoenvironmental deposition, and crude oil maturity, carried out with the use of oil samples from the Baiyun Sag, demonstrate that the organic matter in crude oil has an oxidizing depositional environment and primarily lacustrine facies conditions, with a significantly higher plant input. The oil samples used are mature to highly mature. Crude oil in the northern area of the Baiyun Sag is more mature than samples in the eastern part of the sag. Despite limited source rock data, we were able to conclude that the crude oil samples were derived mainly from the Enping Formation; other potential source rocks of the Wenchang and Zhuhai Formations may also have contributed to the reservoirs in different parts of the sag. Furthermore, the source of crude oil in each structure in the Baiyun Sag was analyzed; for example, crude oil in the LH19-5 structure was generated from the organic matter of the Enping Formation, and crude oil in the LW3-1 structure was derived from the mixed organic matter of the Enping, Wenchang, and Zhuhai Formations. © 2018, V.S. Sobolev IGM, Siberian Branch of the RAS. Published by Elsevier B.V. All rights reserved.  相似文献   

Comparative study of surrogate models for groundwater contamination source identification at DNAPL-contaminated sites     

Zeyu Hou  Wenxi Lu 《Hydrogeology Journal》2018,26(3):923-932

Knowledge of groundwater contamination sources is critical for effectively protecting groundwater resources, estimating risks, mitigating disaster, and designing remediation strategies. Many methods for groundwater contamination source identification (GCSI) have been developed in recent years, including the simulation–optimization technique. This study proposes utilizing a support vector regression (SVR) model and a kernel extreme learning machine (KELM) model to enrich the content of the surrogate model. The surrogate model was itself key in replacing the simulation model, reducing the huge computational burden of iterations in the simulation–optimization technique to solve GCSI problems, especially in GCSI problems of aquifers contaminated by dense nonaqueous phase liquids (DNAPLs). A comparative study between the Kriging, SVR, and KELM models is reported. Additionally, there is analysis of the influence of parameter optimization and the structure of the training sample dataset on the approximation accuracy of the surrogate model. It was found that the KELM model was the most accurate surrogate model, and its performance was significantly improved after parameter optimization. The approximation accuracy of the surrogate model to the simulation model did not always improve with increasing numbers of training samples. Using the appropriate number of training samples was critical for improving the performance of the surrogate model and avoiding unnecessary computational workload. It was concluded that the KELM model developed in this work could reasonably predict system responses in given operation conditions. Replacing the simulation model with a KELM model considerably reduced the computational burden of the simulation–optimization process and also maintained high computation accuracy.  相似文献   

历史文化商业街经营者的地方感研究——基于黄山市屯溪老街案例     

孔翔  王惠  侯铁铖 《地域研究与开发》2015,(4)

历史文化商业街若能凸显地方性特征将更具吸引力,经营者的地方感不仅是商业街地方性水平的重要标志,更是地方性建构的主体基础。对屯溪老街经营者地方感进行了实地调研,初步探讨了经营者地方感的形成机制,并为历史文化商业街的优化发展提出了建议。研究结果表明:经营者地方感不仅受到地方文化景观和经营活动绩效的影响,更与经营者同游客的互动交流相关,而这也将影响到历史文化商业街的吸引力。老街商业开发的模糊定位一定程度上削弱了其地方性,但丰富的历史文化景观以及经营者与游客的频繁互动,则有助于增进经营者地方感。由此,历史文化商业街的发展不仅要重视保护特色文化景观,更要优化商业活动品质,促进经营者与游客的互动,这是增进经营者地方感和商业街吸引力的基本保障。  相似文献   

国外棕地研究进展     

肖龙  侯景新  刘晓霞  李开宇  肖叶甜 《地域研究与开发》2015,(2):142-147

"棕地"一词最早出现在英国的规划文献中,20世纪90年代初开始成为美国官方用语。近年,棕地问题已成为了一个十分严肃的城市发展问题,交织了经济、社会、发展与环境保护的矛盾。为了推动棕地领域内的研究,在整理与分析国外相关文献资料的基础上,针对国外在棕地的定义、基本特征、分类、治理和开发价值评估、环境风险与责任、政策与法律法规、利益相关者及其关系以及棕地的治理与开发对策等方面的研究成果进行了述评。  相似文献   

岱海近400年以来的环境变化:高分辨率XRF岩芯扫描结果的研究     

辛首臻  成艾颖  余俊清  高春亮  洪荣昌  张丽莎 《盐湖研究》2015,(2):1-6,33

岱海是东亚夏季风边缘地带的闭流型半咸水湖泊,其汇水流域降水量的变化易于引发湖泊水位和水化学变动。选用DH11-1岩芯进行1 mm分辨率XRF元素扫描分析,并对测试结果进行多元数理统计分析,旨在查明这些元素与外源碎屑、自生碳酸盐沉积以及岱海水位、水化学变化的关联。结果显示,Si、Al、Ti、K、Fe、Rb等元素相关性好,并呈现相似的变化趋势,其含量变化与主要河流带入的碎屑物的多寡有关;Ca元素主要反映沉积物中自生碳酸盐即文石和方解石矿物含量的增减。研究发现,在人类活动严重影响之前,岱海在过去~400年期间的环境特征总体可划分为4个阶段,各阶段的水位、水化学特征及水量平衡有所不同,总体受汇水盆地降水量变化的控制。此外,沉积物中Cu、Zn、Cr可能与人类活动影响有关。  相似文献   

海南东寨港红树林保护区碳储量及固碳功能价值评估   总被引：3，自引：0，他引：3  

胡杰龙  辛琨  李真  高春  颜葵 《湿地科学》2015,(3):338-343

以海南东寨港红树林保护区为例,利用遥感判读、野外调查和采样数据,采用经验公式和实验室分析方法,计算了12种红树群落植物和土壤的固碳量,得到海南东寨港红树群落的固碳总量为29.56×104t,单位面积固碳量为187.54 t/hm2,其中,土壤固碳量达到90.99%;最后,运用碳税法计算东寨港红树林固碳功能价值为2.75×108元,单位面积红树林的固碳功能价值为17.44×104元。  相似文献