现代黄河水下三角洲砂土液化模式   总被引：1，自引：1，他引：1  

冯秀丽  沈渭铨  杨荣民 《中国海洋大学学报(自然科学版)》1995,(2)

根据实际勘探资料及室内土工试验结果，按极限平衡理论和线性波动理论等，分析了现代黄河水下三角洲砂土在地震和波浪动力因素的作用下发生液化的可能性，并根据其液化过程实质是孔隙水压力产生、发展和消散的过程，总结出砂土液化模式应包括四个阶段；（１）压密阶段：孔隙水压力升高至砂土本身强度，使颗粒产生相对位移；（２）初始液化阶段：孔隙水压力升至土层所受侧向压力，产生较大应变；（３）完全液化阶段：孔隙水压力升至土层上覆有效应力，产生喷水冒沙现象；（４）塌陷形成阶段：孔隙水压力消散。  相似文献   

沙质海岸沿岸输沙率计算方法研究进展     

王宁舸  韩信  孙波  辛文杰  张弛  陈大可 《海洋工程》2023,41(6):171-186

准确预测波浪作用下沿岸输沙率是沙质海岸研究领域的重要科学问题。根据数十年来国内外沿岸输沙率公式的研究进展,按研究方法对各项成果进行分类,并兼顾时间逻辑,回顾了各研究方法的发展历程及其代表性成果。对各项成果的理论基础、考虑因素、资料来源等方面进行了探讨,并采用现场原型沙、室内原型沙和室内轻质沙等实测资料,对国内外常用公式的预测准确性进行了检验。结果表明,孙林云公式与各项实测资料的吻合程度最高,在众多沿岸输沙率公式中具有明显的先进性。在此基础上,对未来可进一步深化研究的方向作出了展望。  相似文献   

Riparian vegetation and island formation along the gravel‐bed Fiume Tagliamento,Italy     

A. M. Gurnell  G. E. Petts  D. M. Hannah  B. P. G. Smith  P. J. Edwards  J. Kollmann  J. V. Ward  K. Tockner 《地球表面变化过程与地形》2001,26(1):31-62

After more than 300 years of river management, scientific knowledge of European river systems has evolved with limited empirical knowledge of truly natural systems. In particular, little is known of the mechanisms supporting the evolution and maintenance of islands and secondary channels. The dynamic, gravel‐bed Fiume Tagliamento, Italy, provides an opportunity to acquire baseline data from a river where the level of direct engineering intervention along the main stem is remarkably small. Against a background of a strong alpine to mediterranean climatic and hydrological gradient, this paper explores relationships between topography, sediment and vegetation at eight sites along the active zone of the Tagliamento. A conceptual model of island development is proposed which integrates the interactions between large woody debris and vegetation, geomorphic features, sediment calibre and hydrological regime. Islands may develop on bare gravel sites or be dissected from the floodplain by channel avulsion. Depositional and erosional processes result in different island types and developmental stages. Differences in the apparent trajectories of island development are identified for each of the eight study sites along the river. The management implications of the model and associated observations of the role of riparian vegetation in island development are considered. In particular, the potential impacts of woody debris removal, riparian tree management, regulation of river flow and sediment regimes, and changes in riparian tree species' distribution are discussed. Copyright © 2001 John Wiley & Sons, Ltd.  相似文献   

黑河中游张掖地区沙漠化土地动态变化   总被引：3，自引：0，他引：3  

齐善忠  王涛  罗芳  丁建亮 《山地学报》2005,23(2):153-157

在我国的西北干旱区,由于所处的自然地理位置生态环境脆弱,加之人类不合理的经济活动,使得该区土地沙漠化现象严重,生态环境恶化。位于黑河流域中游的张掖地区,是我国西北地区重要的商品粮生产基地。由于近年来人口、经济快速增长的压力和人类对土地资源不合理的开发利用,产生了土地沙漠化等一系列环境问题,而且土地沙漠化总体呈上升扩展的趋势,严重地阻碍了绿洲经济和社会的持续、稳定发展。以1994年和2000年具有相同时相(秋季)的Landsat TM4、3、2波段(分别赋予红、绿、蓝三种颜色)、分辨率为30m的标准假彩色合成卫星影像的两期TM影像为信息源,利用Erdas8．4遥感图象处理软件、Arcinfo8．1和Arcview3．2等GIS软件,对黑河流域中游张掖地区的沙漠化土地进行了动态监测研究和分析。结果表明：研究区的沙漠化土地类型共有8类,分别为流动沙地(丘)、半固定沙地(丘)、固定沙地(丘)、风蚀残丘、戈壁、闯田、潜在沙漠化土地和非生物治沙工程地;张掖地区各类沙漠化土地发展和逆转同时存在,1994-2000年沙漠化土地面积增加了642．17km^2。其中,临泽、山丹、民乐和肃南4县的沙漠化土地面积增加了714．85km^2,而张掖市和高台县沙漠化土地面积减少了72．68km^2。从总体上来看,全区的各类沙漠化土地变化仍呈上升扩展的趋势。  相似文献   

循环荷载下加筋砾性土填料的动三轴试验分析     

王家全  畅振超  唐毅  唐滢 《岩土力学》2020,41(9):2851-2860

为探究循环动载作用下加筋砾性土填料的动力特性,在不同加筋层数和围压下对加筋砾性土进行了固结不排水动三轴试验,研究加筋层数和围压对加筋砾性土动力特性的影响,并进一步分析了加筋砾性土轴向累积应变发展机制。研究表明:加筋层数增加时,轴向累积应变减小,回弹模量增大,且加筋作用的影响幅度逐渐衰减;增大围压时,土体轴向累积应变减小,回弹模量和动孔压均随之增大;随着加筋层数和振次的增加,滞回曲线逐渐向应力轴靠近,滞回圈面积逐渐减小,土体耗能作用减弱。基于安定理论和间接影响带理论,揭示了加筋作用对轴向累积应变发展的影响机制。建立了能够反映加筋层数的加筋砾性土轴向累积应变预测模型,其条件参数a、b、g与加筋层数呈线性关系,可有效预测循环荷载下加筋砾性土路基沉降变形规律。  相似文献   

远源砂质辫状河储集层内部隔夹层研究与地质建模——以沾化凹陷孤东油田六区馆上段为例     

乔雨朋  邱隆伟  宋子怡  王军  宋璠  刘卫 《吉林大学学报(地球科学版)》2020,50(1):41-51

河流相储层内部隔夹层研究对其储层内部构型表征及剩余油挖潜具有重要指导作用。本文以沾化凹陷孤东油田六区为例,基于岩心、测井资料,对远源砂质辫状河的单井、连井以及平面发育特征进行了分析;基于沉积微相控制和岩心、测井标定,对不同层次的隔夹层进行了识别以及特征描述;基于密井网的约束对心滩内部夹层的规模与产状进行了表征。结果表明：单层间夹层多是物性夹层,单砂体之间夹层包括泥质夹层与泥砾夹层,增生体之间的夹层为落淤层,落淤层宽度为80~400 m,长度为350~1 630 m,落淤层在滩头倾角约为2.03°,在滩尾倾角为1.28°,在两翼倾角为1.58°。利用界面约束方法,对储层内部夹层进行了构型建模,建立了一套能够进一步深度表征辫状河内部非均质性的构型模型。  相似文献   

Potential role of feldspathic sandstone as a natural water retaining agent in Mu Us Sandy Land, Northwest China   总被引：8，自引：0，他引：8  

Jichang Han  Jiancang Xie  Yang Zhang 《中国地理科学(英文版)》2012,22(5):550-555

This paper analyzed the water-retention mechanism of feldspathic sandstone(fine-(<1 mm diam.)and gravel-sized(2-3 cm diam.)in Mu Us Sandy Land,Northwest China.The objective of this study is to study the effect of feldspathic sandstone amendment on water retention in sandy land.The results showed that as the proportion of fine feldspathic sandstone in the sandy land soil increased,the soil texture changed from sand to silt loam,the capillary porosity gradually increased from 26.3%to 44.9%,and the soil saturated hydraulic conductivity decreased from 7.10 mm/min to 0.07 mm/min.Feldspathic sandstone gravel formed micro-reservoirs in the sandy land soil,playing the role of a′water absorbent′and′water retaining agent′in sandy land.Amendment with feldspathic sandstone can increase water retention in the arable layer of sandy land by 67%.This study provides a theoretical basis for the amelioration of sandy land on a large scale.It can be concluded that amendment with feldspathic sandstone can improve the physical properties of sandy land soil and increase soil water retention.  相似文献   

Diversity and temporal variation of peracarid fauna (Crustacea: Peracarida) in the shallow subtidal of a sandy beach: Playa América (Galicia, NW Spain)     

Juan Moreira  Loreto Gestoso  & Jesús S. Troncoso 《Marine Ecology》2008,29(S1):12-18

Peracarids (Crustacea: Peracarida) are an important component of soft-sediment faunas and are considered good indicators of quality of water and sediments. Nevertheless, little is known about diversity of peracarid crustaceans on the shallow subtidal sediments of Playa América, a sandy beach in the Ensenada de Baiona (Galicia, NW Spain). Therefore, the peracarid fauna of its shallow subtidal zone was studied in a fine-sand site at 4-m depth from February 1996 to February 1997. Monthly sampling yielded a total of 4753 individuals belonging to 60 species. Amphipods were dominant in number of individuals and species followed by cumaceans. The assemblage showed a stable composition in species through the year and was numerically dominated by a few species, namely the amphipods Siphonoecetes kroyeranus and Microprotopus maculatus and the cumacean Pseudocuma longicorne . These species showed large monthly fluctuations in abundance, with maximal values between summer and autumn.  相似文献   

Importance of orientation to the sun and local landscape features in young inexpert Talitrus saltator (Amphipoda: Talitridae) from two Italian beaches differing in morphodynamics,erosion or stability     

Simone Gambineri  Felicita Scapini 《Estuarine, Coastal and Shelf Science》2008

Juvenile sandhoppers (Talitrus saltator Montagu 1808; Crustacea: Amphipoda) were tested under natural conditions to examine their ability to orient to the sun and local features. Experiments were carried out on two Italian sandy beaches subject to different geomorphological dynamics, one under erosion from the sea and the other one under morphodynamic equilibrium (between erosion and accretion). Laboratory-born samples of each population were tested on their beach of origin and compared with wild individuals of the same age; other laboratory-born samples were tested on both beaches, that of origin and the other beach. The population from the beach displaying geomorphologic equilibrium, oriented seawards on both beaches, referring to the sun and the local landscape, while the population from the beach under erosion tended to orient to prominent landscape features on both beaches displaying a scototaxis. These results showed the importance of orientation to local landscape features in young inexpert talitrids, and the innateness of this behaviour in natural populations when shoreline stability allows for a genetic stabilisation of orientation mechanisms.  相似文献   

Reproductive pattern of the epifaunal amphipodPontogeneia rostrata (Crustacea) on dolsando sandy shore in Korea     

Ok Hwan Yu  Seung Jin Jeong  Hae-Lip Suh 《Ocean Science Journal》2008,43(3):127-133

Reproductive patterns of an epifaunal amphipod,Pontogeneia rostrata, were studied on Dolsando sandy shore in Korea. The life history pattern was iteroparous, with recruitment mainly occurring from winter to spring. The sex ratio was male-biased, especially during breeding periods. The mean body length of females was significantly larger than that of males. Brood size and egg volume were positively related to the body length of ovigerous females. There was no significant difference in brood size between successive breeding periods, but egg volumes were significantly higher in early winter (December) than in late spring breeding (May and June), increasing the probability of survival to hatching. These traits contribute to more reproductive potential in early winter than in late spring breeding. The mean brood size of epifaunalP. rostrata was larger but the mean egg volume smaller than that of infaunal amphipods in this sampling area. We suggest that reproductive effort for epifaunal species may be proportionally greater than for infaunal species in risky environments.  相似文献