非黏性土泊松比试验研究

土体泊松比是反映土体侧向变形的重要参数,但是目前的研究应用与模型参数的重要性不相符.通过基于局部变形测量的三轴试验,分析了泊松比的变化规律:在相同的成样方法和控制密度条件下,同一种材料的颗粒排列组合结构基本类似,在不同围压条件下的试样变形规律基本保持一致;随主应力比的增加,切线泊松比也随之增加,建立泊松比与主应力比之间的关系更符合泊松比取值规律.     

不同饵料对管角螺生长、肝脏消化酶活性及软体部营养成分的影响

以缢蛏(Sinonovacula constricta)(A)、菲律宾蛤(Venerupis Philippinaram)仔(B)及自制配合饲料(C)作为饵料,分别研究了上述3种饵料对二龄管角螺(Hemifusus tuba Gmelin)生长、肝脏消化酶活性以及软体部营养成分的影响。结果表明：(1)鲜活饵料的投喂更有利于管角螺的生长和营养物质的累积,配合饲料的摄食效果较差,还需进一步的优化和完善;其特定生长率大小为：缢蛏组＞菲律宾蛤仔组＞配合饲料组,组间差异显著(P＜0.05);(2)不同饵料的投喂对其肝脏消化酶活性的影响差异显著,在整个实验区间的胰蛋白酶活力的大小为：缢蛏组＞菲律宾蛤仔组＞配合饲料组,组间差异显著(P＜0.05);配合饲料组的淀粉酶活力和脂肪酶活力先降后升,鲜活饵料组则较稳定;45 d 后配合饲料组的淀粉酶活力和脂肪酶活力皆显著高于鲜活饵料组的(P＜0.05);表明管角螺在饥饿时,消化酶可能存在补偿性分泌,优先利用糖原和脂肪作为能源物质;(3)不同饵料对管角螺软体部的灰分和水分没有显著影响(P＞0.05),鲜活饵料组的粗蛋白和粗脂肪含量皆显著高于配合饲料组(P＜0.05)。     

A Singular Perturbation Method for Parametric Investigation on J-lay Installation of Deepwater Pipelines

The maximum bending moment or curvature in the neighborhood of the touch down point (TDP) and the maximum tension at the top are two key parameters to be controlled during deepwater J-lay installation in order to ensure the safety of the pipe-laying operation and the normal operation of the pipelines. In this paper, the non-linear governing differential equation for getting the two parameters during J-lay installation is proposed and solved by use of singular perturbation technique, from which the asymptotic expression of stiffened catenary is obtained and the theoretical expression of its static geometric configuration as well as axial tension and bending moment is derived. Finite element results are applied to verify this method. Parametric investigation is conducted to analyze the influences of the seabed slope, unit weight, flexural stiffness, water depth, and the pipe-laying tower angle on the maximum tension and moment of pipeline by this method, and the results show how to control the installation process by changing individual parameters.     

Regional geochemistry of sediments from the Hellenic volcanic arc in regard to submarine hydrothermal activity

Some 600 surface sediment samples from the Hellenic Volcanic Arc region have been analyzed by bulk and HCl selective leach geochemical techniques. Geostatisti‐cal analysis, followed by further selective leaches on a number of samples, has been used in order to identify any regional hydrothermal influence on the sediments and/or any local hydrothermal metal enrichments. The two main sediment components affecting the geochemical variability in the region are biogenic carbonate and volcaniclastic/terrigenous detritus. Proximity to islands appears to be the primary factor controlling the variability in these components. Sediments from deeper water, to the south of the Hellenic Volcanic Arc and in the Anydros Basin, exhibit some elevated levels of Mn, Co, and Cu, probably of hydrogenous origin. No widespread hydrothermal influence to the sediments in the region is recognized, although this could in part be due to the high sedimentation rates in the region. Localized hydrothermal inputs to sediments are, however, recognized proximal to Santorini, in particular within the northern part of the central caldera. These are predominantly of Fe and associated adsorbed/coprecipitated elements along with some Mn enrichment. Several samples proximal to Milos, just off the coast in the northern part of the central Milos embayment, also show enrichments of commonly hydrothermally associated elements, including Mn, Cu, Zn, and Pb. Data suggest that these enrichments could, in part, be due to weathering of “on‐land”; mineralization as well as hydrothermal inputs.     

Case Studies of PSDDF for Phased Placement of Dredged Soils

Use of Terzaghi's one-dimensional consolidation theory is not suitable for consolidation of highly deformable soft clays such as dredged soils. To model this condition, it is necessary to consider non-linear finite strain consolidation behavior, i.e., changes in compressibility and permeability with increasing stress. A one-dimensional non-linear finite strain numerical model, Primary Consolidation, Secondary Compression, and Desiccation of Dredged Fill (PSDDF), has been used to predict the stress-dependent settlement of fine-grained dredged materials. In this paper, two case studies of using PSDDF are discussed to illustrate the applicability and accuracy of PSDDF. The first case study involves PSDDF simulations of laboratory-phased placement of a marine clay dredged from Busan, Korea. PSDDF results are in good agreement with the corresponding results of the laboratory large strain consolidation tests. The other involves estimating the service life of the Craney Island Dredged Material Management Area near Norfolk, Virginia, in the United States. The excellent agreement between measured and calculated values shows that PSDDF is a reliable tool for predicting settlement of dredged material.     

Effects of soil surface components on soil hydrological behaviour in a dry Mediterranean environment (Southern Spain)

Various researchers have studied the spatial pattern of soil surface components such as vegetation, rock fragments, bare soil, litter and surface crusts, as a key factor of hydrological behaviour in Mediterranean settings with heterogeneous patches of vegetation cover and strong human impact. The studies indicate that there is a mosaic of patches that generate run-off or infiltrate overland flow, distributed in various ways along hillslopes. Few of these studies, however, have looked at areas underlain by metamorphic rocks such as phyllites or schists. This study analysed the temporal and spatial variability of the effects of soil surface components on hydrological processes in a small dry Mediterranean catchment underlain by metamorphic rocks. A systematic sampling of multiple sites throughout a hydrological year was carried out.We related the hydrological behaviour of soil surface components to 1) their position along the hillslope, 2) the distance of existing vegetation tussocks from the line of run-off, 3) rainfall intensity and 4) the main physical/chemical soil properties affecting infiltration processes. Statistical analysis was used to check the validity of the relationships. The results show that soil surface components have highly variable effects, in both space and time, on soil hydrological behaviour. These effects particularly depend on the location along the line of maximum slope and the intensity of preceding rainfall, whose interaction defines soil hydrological status. These results are similar to those for other Mediterranean settings with different lithology, in that the succession of contributing patches are hydrologically interconnected along a hillslope. The variables used and the grouping of explanatory variables through principal component analyses were found to be suitable for discussing the spatial distribution of soil surface components in the hydrologically dynamic environment of the study area.     

中国生态足迹和生物承载力构成比例变化分析

基于生态足迹模型,计算了中国1995-2006年人均生态足迹和生物承载力的各构成组分.运用统计-动力学建模方法,构建生态足迹和生物承载力各组分构成比例变化的普适预测模型.结果表明:①1995.2006年,中国人均生态足迹构成以能源足迹和耕地足迹为主,耕地、林地、建设等足迹比例在波动中不断下降,草地、水域足迹比例先上升后下降,能源足迹比例不断增加;人均生物承载力构成以耕地为主.林地、建设、水域承载力比例相差不多,草地承载力比例最小,其中耕地、草地承载力比例不断增加,林地、水域、建设等承载力比例不断下降,且变化幅度均很小.②2007-2015年,耕地、林地足迹比例继续下降,草地、水域、能源足迹比例将逐渐上升,建设足迹比例将在下降一段时间后出现增加趋势,耕地、林地、草地等承载力比例将不断增加,其中耕地、林地承载力比例增加幅度很小.草地承载力比例相对增幅较大;水域、建设承载力比例均呈下降趋势.文章还探讨了可能导致中国人均生态足迹和生物承载力构成比例出现上述变化的原因,给出相应的政策建议,并分析了二者之间的内在变化规律.研究结果对指导我国调整产业结构、土地利用规划和改善生态环境有较重要的启示和借鉴意义.     

考虑主应力方向变化的原状软黏土应力应变性状试验研究

为反映真实工程条件下主应力轴旋转应力路径引起土体性状的变化,对杭州地区正常固结原状软黏土在固结不排水的主应力轴定向剪切和主应力轴单调旋转条件下的应力-应变关系进行试验研究。研究发现,不同主应力方向的定向剪切路径下,随主应力方向变化,试样中各应变发挥程度显著不同,但破坏时的临界八面体应变变化较为稳定,且当八面体应变达到5%时,强度发挥程度已接近甚至超过90%。若剪切过程中增加了主应力幅值不变的不排水主应力轴单调旋转应力路径,只要破坏时主应力方向一致,经历与未经历主应力轴旋转试样的临界应变分量接近,但主应力轴旋转会影响加载阶段试样主应力、主应变增量方向所表现出的不共轴性,并且此影响随旋转时剪应力水平的提高而趋于显著,即使在临界破坏状态下依然明显。试验结果表明,由于土体原生各向异性、黏塑性等性质的存在,并不适宜用相关联流动法则来分析主应力轴旋转条件下土体的应力-应变关系特征。     

基于主成分分析法的福州开发区土地集约利用研究

从土地开发程度、用地结构状态、土地利用强度、用地投入产出效益4个层面选取9个指标建立开发区土地集约利用评价指标体系。以福州市14个国家、省级开发区为评价单元,运用主成分分析法测算开发区集约利用综合指数,探讨各开发区集约利用水平,并在评价基础上将福州市开发区分为3种土地利用模式并提出相应的对策和建议。