Effects of hydrocarbon physical properties on caprock’s capillary sealing ability

A new mechanics formula of caprock’s capillary sealing ability has been established in this paper, in which the boundary layer resistance was considered and characterized by starting pressure gradient. The formula shows that capillary sealing ability of caprock is determined not only by the capillary force of rock and the buoyancy of hydrocarbon column, but also by the starting pressure gradient of hydrocarbons and the thickness of caprock. The buoyancy of hydrocarbon column, the starting pressure gradient of hydrocarbon, and the capillary force of caprock are affected by hydrocarbon density, hydrocarbon viscosity, and hydrocarbon-water interface tension respectively. Based on hydrocarbon property data of reservoirs of Jiyang Depression and equations from literature, the effects of hydrocarbon density, hydrocarbon viscosity, and hydrocarbon-water interface tension on the sealing ability of caprock are analyzed. Under formational conditions, the sealing ability of oil caprock can vary up to dozens times because of the variations of the oil density, oil viscosity, and oil-water interface tension. Thus, the physical characters of hydrocarbon should be considered when evaluating the capillary sealing ability of caprocks. Study of the effects of physical characters on sealing ability of caprock can provide guidance to exploring special physical property hydrocarbon resources, such as viscous oils, and hydrocarbon resources in special pressure-temperature environments.     

Modelling the dynamics of snow cover, soil frost and surface ice in Norwegian grasslands

Studying the winter survival of forage grasses under a changing climate requires models that can simulate the dynamics of soil conditions at low temperatures. We developed a simple model that simulates depth of snow cover, the lower frost boundary of the soil and the freezing of surface puddles. We calibrated the model against independent data from four locations in Norway, capturing climatic variation from south to north (Arctic) and from coastal to inland areas. We parameterized the model by means of Bayesian calibration, and identified the least important model parameters using the sensitivity analysis method of Morris. Verification of the model suggests that the results are reasonable. Because of the simple model structure, some overestimation occurs in snow and frost depth. Both the calibration and the sensitivity analysis suggested that the snow cover module could be simplified with respect to snowmelt and liquid water content. The soil frost module should be kept unchanged, whereas the surface ice module should be changed when more detailed topographical data become available, such as better estimates of the fraction of the land area where puddles may form.     

库布齐沙漠几种沙生灌木叶解剖结构耐旱特征研究

采用石蜡切片法,对库布齐沙漠的主要造林灌木四翅滨藜、小叶锦鸡儿、杨柴、柽柳、互叶醉鱼草和蒙古莸等叶的解剖结构进行了显微观察。选择叶片厚度、角质层厚度、栅栏组织厚度、栅栏组织细胞长、栅栏组织细胞宽、栅栏细胞密度、CTR等多指标。结果表明,柽柳叶片厚度高于其他5种,互叶醉鱼草叶片厚度最小。互叶醉鱼草角质层厚度最厚,角质层与叶片厚度的比值大小顺序为:互叶醉鱼草>四翅滨藜>柽柳>小叶锦鸡儿>蒙古莸>杨柴。CTR大小顺序为:蒙古莸>杨柴>小叶锦鸡儿>互叶醉鱼草>四翅滨藜>柽柳。利用隶属函数综合评价,结果表明:6种树种耐旱能力大小依次为杨柴>四翅宾藜>柽柳>蒙古莸>小叶锦鸡儿>互叶醉鱼草。     

通过根套结构分析研究羽毛三芒草抗旱机制

沙生植物能够通过不同的作用机制抵抗外界干旱。作为典型沙生植物的羽毛三芒草,可以通过根分泌一些黏性物质形成一种根套结构从而具有较高抗旱性。研究过程中首先培养羽毛三芒草的无菌苗,然后以此为基础利用光学显微镜和电子显微镜研究羽毛三芒草的根套结构。结果表明,羽毛三芒草的根套是自身生长出的,并且具有腔室结构,腔室为一个密闭的独立空间并被连接带隔开成许多小室。羽毛三芒草可能通过其独特的腔室结构储存水分来应对沙漠的干旱环境。     

干旱区拟步甲水分散失速率的特征

不同时空分布的拟步甲(Teneberionidae)抗干旱能力存在着差异性,其抗干旱能力主要采用水分散失速率进行评价。在室内30℃恒温处理下,采用重量法测定了不同季节典型干旱环境下13种拟步甲水分散失速率,同时采用陷阱捕获法在野外调查了拟步甲种群动态,分析了不同时空拟步甲抗干旱能力。结果表明,夏季活动高峰种的拟步甲水分散失速率明显小于春季活动高峰种,但夏季活动高峰种致死中时间(LT50)与最大死亡时间(Tmax)比春季活动高峰种大;不同干旱环境下的拟步甲水分散失速率也存在差异性,表现为干旱绿洲区干旱荒漠区极度干旱区,而LT50与Tmax的大小顺序与水分散失速率相反,表明了夏季活动高峰种的拟步甲抗干旱能力大于春季活动高峰种,极度干旱地区的拟步甲更能忍耐干旱环境。     

黄土动力特性试验及深厚黄土地基上土石坝抗震分析研究

对某深厚黄土地基上土石坝的坝基黄土和筑坝黄土进行动三轴和共振柱等动力试验,求得其动强度、动应力-应变关系,以及用于计算动孔压的动孔压特性曲线及其他动参数。在静力分析的基础上对大坝连同地基进行了三维有效应力动力分析。计算表明,Ⅶ度地震下黄土坝基会出现液化,危及大坝安全。为此,建议了距上下游坝脚一定范围内对坝基进行填土压重的经济便利的大坝抗震措施,并对填土压重的抗液化效果进行了优化分析,最终得到经济合理的填土压重范围和压重厚度。     

饱和粉质黏土反复冻融电阻率及变形特性试验研究

针对青藏铁路北麓河粉质粘土,利用冻融循环全过程电阻率试验设备获取封闭系统下冻融过程电阻率、土体温度场、冻胀融沉变形量全过程曲线,探讨了饱和粉质黏土正冻正融过程电阻率及变形特性。试验结果表明：冻融循环过程中电阻率与冻融变形的变化是实时的、完全同步的,利用电阻率特性研究冻融过程土体结构变化是可行的;每次冻融冻土电阻率随着冻融次数增加呈指数关系减小,融土电阻率随冻融次数增加呈指数关系增加;每次冻胀量与融沉量随冻融次数的增加而减小,平均干密度随冻融次数增加而增加,并且经过5次冻融循环后冻胀融沉量和干密度均趋于稳定。     

具有逆辨识结构的模糊神经网络控制及其应用

该文提出一种新型模糊神经网络结构及算法。在这种控制方案中,采用三层模糊神经网络控制器和神经网络逆辨识控制器相结合的结构。计算机仿真研究和实际应用表明,采用新型模糊神经网络控制方法,对大滞后非线性系统的控制是有效的。     

钻孔后压浆技术在苏通大桥基础工程中的应用

钻孔灌注桩后压浆技术,使水泥浆液在高压下渗透、充填和挤密,与沉渣、泥皮、桩周和桩端土体发生物理化学固结,增大了土体和桩端的强度,改变了桩的受力类型,提高了桩侧摩阻力和端阻力,从而提高了单桩的承载力。在苏通大桥超长大直径桩中应用了桩底后压浆技术。通过试桩静载试验,决定在工程施工中采用U型压浆管方案。试桩结果表明,压浆后极限承载力测试值是压浆前的1.48～2.0倍,压浆后端阻力是压浆前的2.46～7.21倍,表明利用后压浆技术达到了节约工程投资、提高工程施工质量及可靠性的目的,并产生了较大的技术经济效益和良好的社会环境效益,这将促进我国公路桥梁建设的桩基技术迈向一个新台阶。     

基坑开挖时立柱桩的沉降计算

在基坑工程中,立柱桩和工程桩形成了长短桩复合桩基础。通过有限元法模拟桩侧摩阻力分布的变化,认为在这种复合桩基础中短桩（工程桩）的存在会影响到长桩（立柱桩）桩侧摩阻力的分布。根据剪切位移法得到考虑短桩影响的计算方法,并将被影响后的长桩桩侧摩阻力分布形式做了等量简化,使之适用于Geddes应力法。提出了利用Geddes应力法计算长短桩复合桩基础沉降的方法,并编制了相应的计算程序PLS,根据实际工程资料进行验算的结果与实测数据基本一致。