循环冻融下寒区工程常用保温材料性能变化试验研究北大核心CSCD

保温材料广泛应用于寒区工程的诸多领域。然而,在服役过程中,保温材料往往会受到浸水、冻融和盐蚀等多场耦合的循环作用,导致其保温、防水和强度等物理力学性能出现不同程度的退化。目前,保温材料的类型非常多,但其性能和耐久性有所不同,因此科学合理地选择保温材料不仅关系到其长期保温效果,同时对于工程构筑物的长期稳定性具有重要的意义。针对循环冻融作用,选取寒区工程中常用的4种保温材料[聚酚醛(FLK)、聚氨酯(PU)、聚苯乙烯挤塑板(XPS)和聚苯乙烯发泡板(EPS)]开展了浸纯水、浸盐水和干燥状态下的室内冻融循环试验,对经历了不同冻融次数的样品进行了表观密度、吸水率、导热系数、压缩强度、弯曲强度和微观结构系列测试。结果表明:浸润作用对保温材料物理力学性质影响显著,亲水性材料FLK的保温和力学性能退化显著,而憎水性材料PU、XPS和EPS变化相对较小。干燥条件下,冻融循环作用对FLK、XPS和EPS吸水率以及FLK的导热系数影响量值可观,但对4种保温材料的压缩和弯曲强度影响不大。浸纯水和盐水条件下,经历30次冻融循环后,FLK的导热系数增加约50%,弯曲强度降低超过0.3%,EPS的压缩强度降低超过10%。浸盐水后保温材料经历冻融循环作用后其物理力学性能退化程度与浸纯水条件下有所不同,该差异值得关注。通过扫描电镜图像能够识别4种保温材料的孔隙尺寸、孔隙致密度和固体颗粒胶结方式,但对经历冻融循环作用后的变化难以识别和量化。基于试验结果,结合寒区交通工程应用场景,分析了4种保温材料的冻融耐久性,以期服务于寒区交通工程保温材料的合理应用。     

Multi-core structure of the Kuroshio in the East China Sea from long-term transect observations

Long-term hydrographic temperature and salinity transect data in the East China Sea from June 1955 to November 2001 are analyzed in order to examine the geostrophic velocity and the structure of the Kuroshio current. The structure of the Kuroshio Current is divided into three basic forms, a single-core structure, a double-core structure and a multi-core structure; the appearance percentage of the three forms are 53.1%, 31.4%, and 15.4%, respectively. The analysis suggests that multi-core structures have significant seasonal and interannual variabilities that are not fully understood but may relate to variations in transport and associated flow instabilities. The Kuroshio's spatial character is also analyzed in detail by applying a simplified model of motion instability into this multi-core structure of the East China Sea Kuroshio. The theoretical results are found to be consistent with the observations, suggesting that the instability of the Kuroshio in the East China Sea may bring forth the formation of the observed multi-core structure.     

利用GIS和模糊层次分析法的南极考察站选址研究

南极考察站选址问题关系南极考察站的安全、功能和运行效率。从科考兴趣、环境条件、后勤保障和地形条件四个方面构建南极考察站选址指标体系,将GIS和模糊层次分析法集成构建一种新的数学模型,用于确定南极考察站建立的适宜性区域,实现选址评价。在对已建南极考察站选址分析的基础上进行了模型验证,得到模型的准确度为98.89%,证明此模型具有较高的准确性和较好的适用性。     

强潮海滩响应威马逊台风作用动力沉积过程研究——以北海银滩为例

研究台风影响下的海滩沉积过程不仅可加深极端海况下的海滩冲淤变化理解,而且有利于海滩资源的保护与海岸工程保护。以强潮海滩——北海银滩为例,通过采集北部湾海区1409号威马逊超强台风作用前后的沉积物、剖面高程及水文资料,探讨强潮海滩的动力沉积过程。结果表明:1)台风作用前后的海滩沙丘-滩肩-沙坝体系的地貌状态基本不变,其中沉积物组分均为砂,细砂、极细砂和中砂三组分平均含量占所有组分的95%以上;与台风作用前比较,台风后的地貌在维持先前形态的条件下,发生局部侵蚀和后退,沉积物相对变粗且细砂含量增加了10%。2)台风作用后后滨沙丘侵蚀,且沉积物滚动组分增加;冲流带和滩肩前缘沉积物的搬运由双跳跃转为单一的跳跃形式。3)台风作用前后的海滩沉积物主要变化过程可由两个模态表征,其中主要模式反映了台风作用前后的海滩以细砂为主的动力沉积变化特征,该模式受控于区域波浪和潮汐的长期耦合作用,并以波浪为主导因素。台风作用前的次要模式反映潮汐作用控制下的海滩沉积横向振荡特征;台风作用后的次要模式表征了台风影响下的海滩横向沉积物偏粗、冲流带-低潮带振荡及其沉积分异过程。     

Pore Characteristics and Factors Controlling Lacustrine Shales from the Upper Cretaceous Qingshankou Formation of the Songliao Basin,Northeast China: A Study Combining SEM,Low-temperature Gas Adsorption and MICP Experiments

To investigate pore characteristics and the factors controlling lacustrine shales,geochemical,mineralogical and petrophysical experiments were performed on 23 shale samples from the Qingshankou Formation of the Songliao Basin,China.A comparison of mercury injection capillary pressure (MICP) and low-temperature N2 adsorption pore-size distribution showed that MICP has a higher pore-size distribution (PSD) line in its overlapping pore diameter range,which may be elevated by the higher pressure of MICP.Therefore,in the overlapping range,low-temperature N2 adsorption data were preferred in pore characterization.Negative correlations were observed between pore volumes and TOC content,indicating organic matter pores are not well-developed in the studied samples.This may be related to their low grade of maturity and type I kerogens.There existed negative relationships between pore volumes and S1,which illustrated that liquid hydrocarbons occupied some pore space.Micropore volume had a better correlation with S1 than mesopore and macropore volumes,which suggests that liquid hydrocarbons preferentially occur in micropores.No obvious relationships between pore volumes and quartz or feldspar were observed,while pore volumes increased with the increasing clay mineral content.These relationships indicate that intraparticle pores in clay minerals represent the principal pore type.     

风浪扰动引起湖泊磷形态变化的模拟试验研究

为了解一次完整的大风浪过程(包括风浪扰动及扰动后的静风期)水体中各形态磷的变化情况及其影响因素,进行了室内模拟风浪扰动的试验研究。结果显示大风浪扰动初期水体中悬浮物(SS)、总磷(TP)、颗粒态磷(PP)和溶解性总磷(DTP)的浓度大幅增加,扰动持续半天后水体SS、TP、PP的浓度均达到最大值,扰动停止后,至少需要10d时间水体中SS、TP、PP的浓度才能回复到扰动前水平;扰动期间水体DTP浓度居于高值,但风浪停止后立即降低;整个风浪过程水体中溶解性反应磷(SRP)浓度变化不大。试验表明,扰动初期沉积物中Fe、Mn结合态磷能快速释放到水体中,但随着扰动的持续,水体复氧,释放到水体中的溶解性活性磷又能与Fe、Mn结合随悬浮物沉降到水底。扰动期间及随后静置1d时间内,水体中悬浮颗粒物的中值粒径连续下降,意味着悬浮颗粒物对磷的吸附能力在不断增强。但水体静置较长时间后,扰动引起的悬浮物几乎全部沉降,絮凝等作用导致水体颗粒物粒度增大。本研究说明虽然大风浪扰动初期能引起浅水湖泊中颗粒态和溶解态营养盐浓度的迅速提高,能够为水华蓝藻的快速生长提供大量可直接利用或酶解的营养盐,但随着风浪扰动的持续,由于水体复氧、水中颗粒物粒度不断细化、颗粒物中的有机成分比例不断增高等,悬浮颗粒物对活性磷的吸附能力也相应提高,两种作用相互削减使得风浪扰动后期水体活性磷浓度的增幅并不明显。     

黄河龙门段商周转折时期的古洪水事件及气候背景

通过野外观察研究,在黄河中游晋陕峡谷龙门段乡宁-韩城大桥西端支沟内,发现了全新世古洪水滞流沉积物.通过野外观察和室内实验分析,证明它们是黄河特大洪水悬移质泥沙在高水位滞流环境下的沉积物,记录了黄河晋陕峡谷段一期4次特大古洪水事件.通过地层学对比分析和光释光测年,确定这4次洪水发生在全新世中期-晚期转折阶段,即我国历史上商代末期-西周初期的气候突变转型期.利用"古洪水滞流沉积物厚度含沙量法"恢复古洪水洪峰水位,运用HEC-RAS模型估算出4次古洪水事件洪峰流量介于46280~48800 m~3/s之间.这些成果为黄河中游地区的防洪减灾、水资源开发利用、流域生态环境综合治理等方面提供了可靠的超长尺度水文数据.这为深入理解黄河流域水文系统对于全球变化的响应规律提供了新的证据.     

A New Family of Sauropod Dinosaur from the Upper Cretaceous of Tianzhen, Shanxi Province, China

A new gigantic sauropod, Huabeisaurus allocates gen. et sp. nov., about 20 m in length and 5 m in height, was discovered in the Upper Cretaceous Huiquanpu Formation, Tianzhen County, Shanxi Province. It is notably different from Diplodocidae, Titanosauridae and Nemegtosauridae in the following aspects: the teeth are strong, peg-like with a length ratio of the tooth crown to tooth root at about 3 to 1; the cervical vertebrae are long with forked spines; the spines in dorsal vertebrae are relatively high, unbifiarcated; the caudal vertebrae are amphicoelous, with anterior neural spines and unbifurcated spines and chevrons; the femur is straight and long, narrow and flat and the tibia and fibula are long and flat. These characters show that the described genus should represent a new family, Huabeisauridae fam. nov. The discovery enriches the sauropod dinosaur record in China, and is quite significant to the study of the taxonomy, evolution, migration, extinction and palaeobiogeographic provincialism of the     

An automated approach for conditioning discrete fracture network modelling to in situ measurements

Creation of a geological fracture network model conditioned to in situ geometric measurements is of great importance to geoprofessionals, as fractures dominate pathways for fluid flow, a major concern for many engineering applications. This paper introduces and applies the Stochastic Nelder Mead simplex method to automatically calibrate stochastic parameters of geometric characterisations of a discrete fracture network model. This method can overcome the non-convergence of a previous exploratory approach on the classic Nelder Mead method by others, and is an effective substitution to the manual trial-and-error method and is complementary to existing conditional simulation approaches. The procedure to integrate the Stochastic Nelder Mead with a discrete fracture network is presented in detail, and a case study was conducted. Results show that the improved model can better handle the stochastic nature of the underlying system and effectively simulates the observed number and mean trace length of these fractures, although the model results underestimate its standard deviation. Simulated distributions of trace lengths and spacings are within acceptable ranges except for some small offsets, which can be adjusted during model runs.     

近十年国内钻井液降粘剂研究进展

随着能源消费持续升高,常规资源无法满足日常需求,进行深井钻探显得尤为重要。然而,井底深部高温带来的钻井液粘度增加、流变性变差等问题,致使降粘剂成为不可缺少的钻井液处理剂之一。降粘剂主要通过拆散或阻拦粘土颗粒间形成网架结构,从而达到降低钻井液粘度、改善流变性的目的。结合相关研究文献,综述近十年来国内钻井液降粘剂的研究现状,介绍了3大类降粘剂：合成聚合物类、改性天然材料类、利用工业废料制备降粘剂。针对目前存在的问题,指出未来应从分子结构设计层面研发低成本、环保、适用于高温高盐高密度钻井液的降粘剂,同时注重工业废料的利用,积极与现场应用相结合加快成果转化。近年来,合成聚合物类降粘剂研究量居多、发展最迅速,本文着重介绍了此类降粘剂的发展现状及应用前景。