面向对象的连云港海岸带土地利用变化及驱动力分析   总被引：2，自引：0，他引：2  

高祥伟  费鲜芸  韩兵 《海洋科学》2014,38(4):81-87

以连云港海岸带为研究区,基于1978年和2010年两期Landsat影像,提取土地利用信息,分析土地利用特征及其动态变化过程;面向土地利用变化基本单元,进行土地利用变化驱动力分析。结果表明:研究期初,该地区的主要土地类型为耕地和盐田,共占研究区面积的67.14%;32 a间共有37.17%的土地发生了变化,盐田和耕地面积快速减少,水产养殖区和工矿企业用地快速增加,有限的林地资源在减少,滩涂围垦达面积46.55 km2,土地利用程度加深;变化的土地中,38.95%由经济结构调整驱动,发展潜力大;27.75%由政策驱动,存在诸多的社会和生态问题;20.49%由政策或者经济结构调整与生产力水平共同驱动,取得较好经济和社会效益;12.81%的土地由政策、人口及经济发展共同驱动。连云港海岸带土地利用存在诸多不足之处,也具有巨大的发展空间。本研究对连云港市提高土地利用的社会效益和生态效益具有重要意义。  相似文献   

明基床上开孔沉箱垂直力峰值对应的水平力分析          下载免费PDF全文

孙大鹏  张玉彬  夏志盛  吴浩 《海洋工程》2014,32(6):49-58

利用水槽二维物理模型对规则波及不规则波作用下明基床上开孔沉箱所受到的波浪力进行了较为系统的试验研究。分析了开孔沉箱总垂直力峰值时刻对应的总水平力与相对基床高度、消浪室相对宽度、波陡、相对水深以及开孔率等影响因素之间的关系,给出了明基床上开孔沉箱总水平力比值(总垂直力峰值时刻对应的总水平力/总水平力峰值)与各影响因素之间的计算关系式。研究成果可供实际工程参考应用。  相似文献   

靠球减震系统在导管架平台中的应用          下载免费PDF全文

王梦川  杨树耕  唐友刚  陈涛  王宁  张建勇 《海洋工程》2014,32(2):24-29

导管架生产储油平台在油轮靠泊和外输期间,如遇风浪天气,平台的晃动非常明显,为此引入橡胶靠球减震系统。运用ANSYS有限元分析软件,建立导管架生产储油平台的真实有限元模型,计算平台在靠船碰撞力和波浪力共同作用下平台关键点位置应力变化及振动响应过程,为靠球减震系统在实际工程中应用提供理论依据。  相似文献   

Dynamic response analysis of a floating mooring system   总被引：1，自引：0，他引：1  

Conghuan Le  Hongyan Ding  Puyang Zhang 《中国海洋大学学报(英文版)》2014,13(3):381-389

An innovative floating mooring system with two or more independent floating mooring platforms in the middle and one rigid platform on each side is proposed for improving efficiency and safety in shallow water. For this new system, most of collision energy is absorbed through the displacement of floating platforms. In order to illustrate the validity of the system, a series of model tests were conducted at a scale of 1:40. The coupled motion characteristics of the floating mooring platforms were discussed under regular and irregular waves, and the influences of wave direction and other characteristics on dynamic response of the system were analyzed. The results show that the mooring system is safest at 0° of wave incident angle, whereas the most dangerous mooring state occurs at 90° of wave incident angle. Motion responses increase with the increase of wave height, but are not linearly related to changes in wave height.  相似文献   

辽西大黑山生态修复区土地利用格局变化及驱动力     

郑云龙  高鹏  张立勇  王兵 《山地学报》2014,32(6)

生态修复区土地利用与覆盖变化是区域环境变化研究的重要内容,可为水土保持生态修复措施的调控及效益定量评价提供依据。以辽西大黑山生态修复区2000年、2005年和2010年的Landsat TM遥感影像为基础数据,基于Erdas Imagine遥感软件和ArcGIS技术平台,利用土地利用动态度、土地利用程度综合指数和转移矩阵等指标,对研究区土地利用格局的动态变化进行了定量分析,并探讨了其变化的驱动力因素。结果表明:1.10 a间,耕地保持面积最大,其次是林地和草地;耕地和未利用土地占总面积比例分别减少了28.43%和44.32%,林地、草地、城镇村及工矿交通、水域及水利设施用地占总面积比例分别增加了83.68%、10.75%、21.07%和162.74%。2.2000—2005年,林地的土地利用变化幅度最大,为12.42%,其次为未利用土地和草地;2005—2010年,水域及水利设施用地的土地利用变化幅度最大,为24.82%,其次是草地、未利用土地和耕地。3.研究区土地利用程度和开发强度处于中等偏上水平,2000—2005年土地利用处于发展期,2005—2010年土地利用处于调整期;土地利用类型的转入和转出主要发生在耕地、林地和草地之间。4.水土保持生态修复和退耕还林等生态建设项目的实施,可以较大程度地改变微地貌、减少地表坡度、提高植被盖度,在短时间使土地利用的空间分布发生较大变化,是其土地利用格局变化的主要驱动力因素。  相似文献   

泥石流源区典型草本植物根系抗拉试验   总被引：5，自引：0，他引：5  

陆桂红  欧国强  杨顺  王钧  宇岩 《山地学报》2014,32(6)

植被对于泥石流源区的生态修复和物源稳定具有重要意义,其中植物根系的抗拉力学特性是影响植物护坡的主要因素之一。为了探究泥石流源区植物根系的抗拉特性,以都江堰市锅圈岩泥石流源区为研究区,在野外调查的基础上,通过重要值计算确定了源区典型草本植物并进行抗拉强度试验。研究表明,锅圈岩泥石流源区主要分布有寒芒、节节草等对恶劣环境适应性强的乡土植物,它们的根系平均分布深度在30 cm以内;根系抗拉力与根径呈幂函数正相关关系,抗拉力随根径的增大而增大。当根径0.50 mm时,抗拉强度与根径也表现出幂函数关系;当根径0.50 mm时,部分植物根系的抗拉强度值波动较大。不同植物根系的平均抗拉强度从大到小依次为铁杆蒿(106.24 MPa)、节节草(非节点处,30.79 MPa)、草地早熟禾(28.69 MPa)、小飞蓬(20.20 MPa)、多头苦荬(18.77 MPa)、寒芒(老根,14.87 MPa)、节节草(节点处,12.67 MPa)、寒芒(新根,8.29 MPa)。泥石流源区草本植物的根系抗拉力学特性良好,对稳固浅层土体和泥石流物源有积极作用。  相似文献   

Changes in the critical erosion velocity for sediment colonized by biofilm     

Hongwei Fang  Qianqian Shang  Minghong Chen  Guojian He 《Sedimentology》2014,61(3):648-659

In flowing water the incipient motion of sediment can be affected by the presence of microbial biofilm growth. This article documents a series of flume experiments using non‐uniform sediments, in which sediment entrainment was investigated for cases where the sediment was immersed in deionized water, so that no biofilm developed, and for cases where a bio‐sediment was cultivated by placing the sediment in a mixture of natural water and nutrient solution. Differences in entrainment and the velocity at incipient motion were measured over an eight week period, as biofilm grew. It was found that the incipient motion phenomena were quite distinct between the two kinds of sediment. Sediment with biofilm was more stable and, over time, incipient velocity increased to a threshold level, before declining. Biofilm development is clearly an important control on the stability of sediments, especially in eutrophic water bodies. Two incipient velocity formulas were derived for sliding and rolling conditions. Film water theory was utilized to describe the cohesive force between sediment particles and the adhesive force generated by biofilm was introduced into the formula derivation; the time variation characteristics of biofilm strength and the features of the substrate were also taken into consideration. Such analyses can help to predict sediment transport changes due to biofilm presence in nutrient‐rich water bodies.  相似文献   

The critical scale of fluctuation for active lateral forces in spatially variable undrained clays     

《Computers and Geotechnics》2014

This study addresses the phenomenon of the critical scale of fluctuation (SOF) for active lateral force (P_a) in undrained clay when there is a spatial variability in the clay. The phenomenon is significant under shear strength (τ_f) random fields but is insignificant under unit weight (γ) random fields. It is found that the phenomenon of the critical SOF is connected to the nature of the spatial averaging, which is “line averaging” under τ_f random fields and is “area averaging” under γ random fields. The former averaging effect (line) is significantly weaker than the latter (area), so the tendency for the critical slip plane to seek for a favorable location is stronger for the τ_f random field than for the γ random field. Hence, the phenomenon of the critical SOF is more pronounced under τ_f random fields than under γ random fields. The underlying mechanisms for the phenomenon of the critical SOF will be explored in this paper.  相似文献   

Test and numerical research on wall deflections induced by pre-excavation dewatering     

《Computers and Geotechnics》2014

Numerous studies have been devoted to the performance of excavations and adjacent facilities. In contrast, few studies have focused on retaining wall deflections induced by pre-excavation dewatering. However, considerable inward cantilever deflections were observed for a diaphragm wall in a pre-excavation dewatering test based on a long and narrow metro excavation, and the maximum deflection reached 10 mm (37.6% of the allowable wall deflection for the project). Based on the test results, a three-dimensional soil–fluid coupled finite element model was established and used to study the mechanism of the dewatering-induced diaphragm wall deflections. Numerical results indicated that the diaphragm wall deflection results from three factors: (1) the seepage force around the dewatering well and the soil–wall interaction caused the inward horizontal displacement of the soil inside the excavation; (2) the reduced total earth pressure on the excavated side of the diaphragm wall above approximately 1/2 of the maximum dewatering depth disequilibrated the original earth pressure on both sides of the diaphragm wall; and (3) the different negative friction on the excavated and retained sides of the diaphragm wall led to the rotation of the diaphragm wall into the excavation.  相似文献   

东北地区唐代渤海古城遗址空间格局及影响因素分析     

刘海洋  付雨鑫  殷铭徽 《地理科学》2022,42(6):1005-1014

运用ArcGIS软件及空间分析等方法,研究了东北地区234座唐朝渤海国古城遗址分布特征,探讨了古城遗址空间格局与自然条件的关系。通过对234座古城址进行分析,发现唐朝渤海国古城址主要集中在4个集聚区,即图们江?鸭绿江流域集聚区（A）、牡丹江流域集聚区（B）、松花江?辽河流域集聚区（C）、穆棱河流域集聚区（D）。其中图们江?鸭绿江流域集聚区是最主要的遗址分布区,位于研究区的南部,占遗址总量的47.43%。研究区渤海国古代城址呈北疏南密的分布特征,形成明显的“空间组群”格局。在当时的气候环境之下,水热条件等自然因素成为影响城址的主要因素,而政治、经济、军事和交通区位等人文因素则对古城遗址的数量和分布起重要导向作用。  相似文献