青藏高原封闭道碴层对下部多年冻土保护作用的现场实验研究   总被引：1，自引：1，他引：0  

马小杰  张建明  张明义 《冰川冻土》2006,28(2):229-234

为了研究封闭道碴层对其下部多年冻土是否具有积极的保护作用,在青藏铁路北麓河试验段附近建立了封闭碎石道碴坑和卵石地表对比试验场,并对下部地温进行监测.结果发现:经过两个冻融循环后,道碴坑底部(1.3 m深度处)年平均地温为-1.11℃,比卵石地表相同深度低0.73℃;道碴坑中部(0.7m深度处)年平均地温为-1.60℃,比卵石地表相同深度地温低1.4℃.封闭碎石道碴层可以提升冻土上限,降低多年冻土温度,对下部多年冻土起到很好的保护作用.封闭道碴层的这种降温效果是由于道碴层具有可变导热系数的特点,暖季道碴层上部温度高,下部温度低,不产生对流,等效导热系数小,传入道碴层以下土体的热量较少;相反寒季道碴层上部温度低,下部温度高,产生自然对流,等效导热系数增大,有利于道碴层以下土体释放热量.  相似文献   

Combined effects of groundwater and aeolian processes in the formation of the northernmost closed saline depressions of Europe: north-east Spain     

Jos Angel Snchez  Antonio Prez  Pablo Coloma  Javier Martínez-Gil 《水文研究》1998,12(5):813-820

A genetic and evolutionary model is established for saline depressions in continental areas. These depressions are located in arid or subarid areas, and are developed on low permeability geological mediums (K<10 mm/day) with a lack of streams reaching the small lakes. The phenomenon of evaporation is fundamental, since it is the basic requirement for the presence or absence of a free water surface in the lake, and also for depression of the phreatic surface, which causes inflow of groundwater towards the lake. With these conditions, the proposed model includes the following stages: (i) initiation of the close depression; (ii) deepening of the depression; (iii) formation of the lake basin and the end of the deepening; and (iv) levelling and lateral extension of the lake basin. The combined effects of groundwater flows and aeolian action offer a coherent explanation for the origin and evolution both of the closed depressions found in the Ebro Valley, and of the salt lakes that subsequently form. The processes described form morphologies of oval shape with the main axis parallel to the direction of the wind, flat floors and evaporitic sedimentation, although they act on geological materials with different lithologies. © 1998 John Wiley & Sons, Ltd.  相似文献   

淮南煤田阜凤推覆构造带水文地质特征研究   总被引：6，自引：0，他引：6  

桂和荣  宋晓梅  彭子成 《地球学报》2005,26(2):169-172

淮南煤田阜凤逆冲断层是一压性断层,使寒武系灰岩、砂泥岩推覆于二叠系煤系地层之上。该断层的水文地质特征,对推覆体下安全采煤具有重要影响。本文测试了阜凤推覆体岩石化学成份并进行了含、导水性分析;研究了阜凤断层带构造岩的微观特征,并通过崩解试验分析了断层带介质的水稳定性及地下水径流的有利条件;最后利用灰岩浸溶试验及碳酸平衡原理进一步研究了阜凤断层带的开放性与封闭性,结论是：阜凤推覆构造带属开放系统,具有地下水补给和径流的必要条件,是导水的。其导水性随煤矿开采规模的扩大而增强,此结论已在煤矿生产实践中得到验证。  相似文献   

The role of marine protected areas in environmental management   总被引：1，自引：0，他引：1  

Jennings  Simon 《ICES Journal of Marine Science》2009,66(1):16-21

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基于IGS连续运行站的地壳非对称运动趋势研究     

杨强  党亚民  李建成 《测绘科学》2009,34(2)

本文利用IGS全球分布的连续运行站研究了地壳运动趋势。首先利用线性拟合计算了各运行站的高程方向线性速度,然后利用求得的线性速度计算了不同纬度的闭合环纬线变化率。结果表明,地壳各点运动趋势既不均衡也不对称;南半球闭合环纬线变化率全部为正值,说明南半球纬线圈处于拉伸状态,反映南半球整体膨胀趋势;北半球变化率有正有负,说明北半球整体变化趋势不明显。通过分析得出地壳存在非对称运动趋势的结论。  相似文献   

Spatial and temporal patterns in bacterial abundance, production and viral infection in a temporarily open/closed southern African estuary     

E.L. Allan  P.W. Froneman 《Estuarine, Coastal and Shelf Science》2008,77(4):731-742

The spatial and temporal patterns in bacterial abundance, biomass, production, nanoflagellate abundance and the loss of bacterial production due to viral lysis were investigated in a temporarily open/closed estuary along the eastern seaboard of southern Africa over the period May 2006 to April 2007. Bacterial abundance, biomass and production ranged between 1.00 × 10⁹ and 4.93 × 10⁹ cells l⁻¹, 32.43 and 108.59 μg C l⁻¹ and 0.01 and 1.99 μg C l⁻¹ h⁻¹, respectively. With a few exceptions there were no significant spatial patterns in the values (P > 0.05). Bacterial abundance, biomass and production, however, demonstrated a distinct temporal pattern with the lowest values consistently recorded during the winter months. Bacterial dynamics showed no effect of mouth opening events. Nanoflagellate and bacterial abundances were significantly correlated to one another (P < 0.05) suggesting a strong predator-prey relationship. The frequency of visibly infected bacterial cells and the number of virus particles within each bacterial cell during the study demonstrated no significant temporal or spatial pattern (P > 0.05) and ranged from 0.5 to 6.1% and 12.0 to 37.5 virus particles per bacterium, respectively. Viral infection and lysis was thus a constant source of bacterial mortality throughout the year. The estimated percentage of bacterial production removed by viral lysis ranged between 7.8 and 88.9% (mean = 30.3%) of the total which suggests that viral lysis represents a very important source of bacterial mortality during the study.  相似文献   

Summary of studies on closed-polyculture of penaeid shrimp with fishes and moluscans   总被引：1，自引：0，他引：1  

李德尚  董双林 《中国海洋湖沼学报》2000,18(1):61-66

ＩＮＴＲＯＤＵＣＴＩＯＮＴｈｅｗｏｒｌｄ’ｓｓｈｒｉｍｐｃｕｌｔｕｒｅｉｎｄｕｓｔｒｙｈａｓｂｅｅｎｓｕｆｆｅｒｉｎｇｆｒｏｍｖｉｒａｌｅｐｉｄｅｍｉｃｄｉｓｅａｓｅｓａｎｄｆｅｌｌｉｎｔｏａｄｉｆ ｆｉｃｕｌｔｐｏｓｉｔｉｏｎｆｏｒｙｅａｒｓ.Ｉｔｉｓｇｅｎｅｒａｌｌｙａｃｃｅｐｔｅｄｔｏｄａｙｔｈａｔｔｈｅｄｉｓｅａｓｅｓｗｅｒｅｃａｕｓｅｄｍａｉｎｌｙｂｙｗａｔｅｒｐｏｌｌｕ ｔｉｏｎｃｒｅａｔｅｄｂｙｓｈｒｉｍｐｃｕｌｔｕｒｅｉｔｓｅｌｆ,ｂｏｔｈｉｎｓｈｒｉｍｐｐｏｎｄｓａｎｄｉｎｃｏａｓ…  相似文献   

利用小角中子散射表征页岩闭孔结构与演化     

张林浩  徐嫣然  孙梦迪  蒋恕  张钰莹  Chunming Wu  张介辉  梁兴  王高成 《沉积学报》2021,39(2):310-323

随着页岩孔隙网络结构表征更加精细与定量化,页岩中闭孔含量、结构与演化引起了广泛关注.为研究页岩的闭孔特征,通过小角中子散射、氮气吸附、高压压汞和氩离子抛光—场发射扫描电镜等实验手段对四川盆地威201(W201)井中下志留统龙马溪组页岩、上奥陶统五峰组页岩和下寒武统筇竹寺组页岩中的闭孔含量及孔隙结构进行了测定,同时分析了...  相似文献   

毗邻建筑考虑局部场地效应时的LQG控制     

于骁  张文首  林家浩 《地震工程与工程振动》2007,27(6):197-202

本文基于虚拟激励法和留数定理推导出毗邻建筑考虑局部场地效应时在平稳随机地震激励下的LQG控制问题的闭合解。利用此闭合解进行场地土参数研究表明,场地土参数对位移和加速度响应的影响是不同的,甚至是相反的。因此对于给定的LQG控制加权阵Q和R,场地土的卓越频率和阻尼比变化对减震效果有显著影响,应予以重视。  相似文献   

淤泥质海岸人造沙滩工程评估:以启东碧海银沙沙滩为例     

滕雨辰  刘爽  庄振业  曹立华  张永华 《海洋地质前沿》2021,37(1):77-83

启东碧海银沙沙滩位于长江入海口北支口北侧启东嘴附近,是典型的粉砂淤泥质海岸,受长江江流、海水风暴潮和潮流等影响,海岸地质背景较为复杂,以海陆交互作用的潮间带和水下三角洲地貌为主,本身地质条件并不适合作为沙滩旅游项目的开发.自2011年起,恒大集团在这里使用泥岸人造沙滩技术,通过围堤筑坝、滤沙净水,成功建成了围海7.23...  相似文献