初始含水率对冻结粉质黏土变形和强度的影响规律研究

冻土的变形和强度受温度、水分及压力的影响甚为显著。通过对-6 ℃的冻结粉质黏土在初始含水率为12.5%～20%范围内进行一系列的三轴试验,分析初始含水状态对冻土变形和强度的影响规律。研究发现,当初始含水率较低时,随着围压的增大,冻结粉质黏土相继出现应变软化和应变硬化特征;当初始含水率大于16%时,其应力-应变关系主要呈现出应变软化特征;随着初始含水率的增大,初始切线模量随围压从线性缓慢增大逐渐过渡为抛物线形的分布。同时,根据包络线定理,建立非线性摩尔-库仑强度准则,用以描述初始含水率为12.5%、14%和16%的冻结粉质黏土强度随围压变化的非线性;当初始含水率为18%和20%时,其强度可用线性摩尔-库仑强度准则描述。     

黔东北地区下寒武统牛蹄塘组页岩气特征及主控因素分析*

黔东北地区页岩气资源丰富,其下寒武统牛蹄塘组具有巨大的勘探潜力。在对几口探井分析的基础上,结合露头资料及地球化学特征,认为研究区牛蹄塘组页岩具有厚度大、分布广、有机碳含量高、热演化程度相对较高、储集条件较好等特征。但由于大部分针对牛蹄塘组页岩气的钻井遇到的都是含气量低、甲烷含量低、氮气含量高的页岩,因此对黔东北地区页岩气富集的主控因素进行了系统分析,认为该地区牛蹄塘组页岩气具有沉积控带、断裂控藏的明显特征。     

湛江组灰色黏土空间展布规律研究

分布于湛江地区的湛江组灰色黏土因其特有的强结构性在实际工程中产生一系列岩土工程问题,20世纪80年代已为国内众学者所关注。由于湛江组地层在雷州半岛区域内,具有不同沉积环境而表现出不同空间展布规律,实际工程中难以掌握其分布特性。根据现场地质调查资料,结合雷州半岛的地形地貌、地质构造以及湛江组地层的沉积环境,在雷州半岛布置27个钻孔进行地质钻探取样。不同区域典型地层剖面图说明,灰色黏土在不同的沉积环境有着不同沉积韵律、埋藏深度、地层厚度等,分布具有区域性,根据层顶埋深及地层厚度分析灰色黏土的结构性对实际工程的影响。同时,根据钻孔地层数据,利用基础 GIS软件平台MAPGIS构建湛江组结构性黏土空间展布规律三维地质模型,全面展示出灰色黏土在雷州半岛的整个展布规律,实现灰色黏土空间展布的可视化,最后简单地介绍该模型的基本应用。     

黄土坡临江I号崩滑体变形及稳定性演化规律研究

为准确把握黄土坡临江I号崩滑体在水库运营期间的变形及稳定性演化动态,采用试验隧洞群的形式充分揭露崩滑体的地质结构及空间形态,并构建崩滑体双层滑带地质模型。采用饱和-非饱和渗流有限元算法获取其在水库运营期间地下水渗流场的动态变化过程,以此为基础研究崩滑体的变形和稳定性演化规律。研究表明,崩滑体的变形主要发生在库水位下降期间,且呈明显的牵引式运动特征,变形演化规律与GPS监测点实测数据相符;崩滑体的浅层滑坡在演化过程中受地下水渗流场动态变化的影响较大,因此,其稳定性系数的波动幅值也较大,其临界失稳水位下降速度为2.0 m/d。综合分析认为,黄土坡临江I号崩滑体整体稳定性相对较好,但浅层滑坡在降雨和库水位下降过程中存在局部失稳的可能。     

Eliminating illegal bottom trawl fishing in the coastal waters of Korea

Illegal bottom trawl fishing using nets with a small mesh size has been one of the most difficult problems to address in fisheries management in Korea. This practice has occurred for the last century, since the Japanese colonial period. The elimination of illegal bottom trawl fishing, regulated in the Fisheries Law (Law No. 10292), was extremely difficult because the number of vessel owners increased to greater than 3000, creating a strong oppositional lobby. Therefore, the Korean government carried out an ‘incentive program’ to buy-back vessels, which has been very effective in eliminating illegal bottom trawl fishing in the coastal waters of Korea.     

防波堤滑移运动解析解及其应用研究

基于波浪力时程曲线分解,推导出非破碎波和破碎波作用下防波堤滑移运动方程的解析解,可为类似问题提供参考.通过与以往实验结果对比验证了解析解的有效性,并将其应用于防波堤设计实例中,计算了不同设计波浪重现期条件下的期望滑移距离和期望失效概率,表明我国规范中设计波浪重现期标准的合理性.从计算结果分析,考虑到分项系数对于荷载效应的放大作用,遵从规范设计出来的防波堤尺寸明显偏于安全,若采用允许一定变形的设计理念,则可在不影响结构可靠性的基础上极大节约材料用量.     

具有压敏特征的稠油油藏水平井产能分析

依据幂律流体在压敏油藏中的稳定渗流理论以及水平井远井和近井区域渗流场的描述,推导考虑幂律性特征的稠油在压敏油藏中3种流态并存的水平井产量计算公式.依据区域边界流量和压力相等的原则给出方程解法,最终可求得水平井的产量.通过计算结果与油田实际资料的对比,证明了该方法的有效性和实用性.对幂律指数、介质变形系数、启动压力梯度与水平井产量关系分析结果表明,稠油油藏水平井的产量与启动压力梯度和介质变形系数呈线性反比关系,随着幂律指数的降低,水平井产量快速下降.     

Study on Movement Evolution Law of Soil Water in Condition of Agronomic Water Saving Irrigation

Fresh water supplied are often limited in mainland China, reducing agricultural productivity. However the use of straw mulch is the main management technique for agronomic water saving. This paper investigates the movement of soil water under straw mulch compared to a non-mulch test plot. Results demonstrated that straw mulch effected soil water movement primarily during drought periods and throughout shallow soil (i.e. depths of less than 200 cm). The soil moisture and soil water potential at the mulch test plot in drought period are both higher than that of contrast test plot, and along with increasing soil depth, the straw mulch effect weakens. When evaporation is dominated by surface evaporation, straw mulch will effectively restrict the evaporation of soil water; when evaporation dominated by vegetation transpiration, the straw mulch promotes the transpiration of vegetation. In drought periods, straw mulch is not effective for deep soil water infiltration, but is advantageous for soil water utilization of mid- and shallow- soils (0-120 cm), however the infiltration speed rate of straw mulch point during high water period is higher than that of contrast plot. This paper highlights the importance of good management practices of agricultural land in order to limit soil water losses, which is essential when water is such a limited resource.     

A consistent framework for Horton regression statistics that leads to a modified Hack's law

A statistical framework is introduced that resolves important problems with the interpretation and use of traditional Horton regression statistics. The framework is based on a univariate regression model that leads to an alternative expression for Horton ratio, connects Horton regression statistics to distributional simple scaling, and improves the accuracy in estimating Horton plot parameters. The model is used to examine data for drainage area A and mainstream length L from two groups of basins located in different physiographic settings. Results show that confidence intervals for the Horton plot regression statistics are quite wide. Nonetheless, an analysis of covariance shows that regression intercepts, but not regression slopes, can be used to distinguish between basin groups. The univariate model is generalized to include n > 1 dependent variables. For the case where the dependent variables represent ln A and ln L, the generalized model performs somewhat better at distinguishing between basin groups than two separate univariate models. The generalized model leads to a modification of Hack's law where L depends on both A and Strahler order ω. Data show that ω plays a statistically significant role in the modified Hack's law expression.     

大气边界层剪切湍流统计特性的风洞实验及其层次相似律

对风洞模拟的大气边界层的剪切湍流场的速度脉动时间序列信号以及某一高度位置上的小波变换分解重构的信号进行了系统的统计分析.结果表明, 在非均匀下垫面大气边界层的不同垂直高度上的信号, She-Leveque湍流层次相似律都成立, 层次相似指数β和最高激发态的奇异标度指数γ随垂直高度的变化而变化, 并给出不同尺度的分解重构信号的一些层次结构特点.