预应力锚索在边坡加固中方位角的确定

根据预应力锚索在边坡加固中的作用机理,结合工程实例讨论了确定预应力锚索方位２角时应考虑的因素,并介绍了方位角的确定过程。     

高30断块油藏S／P二元复合驱室内实验研究

针对高30断块砂岩油藏,筛选和评价了表面活性剂／聚合物（S／P）二元复合驱油体系。结果表明,表面活性剂CDS-1在有效浓度（0．025％～0．300％）低而宽的范围内,体系与原油的界面张力可降到能大幅度提高驱油效率的10^-2mN／m数量级;当疏水缔合聚合物HNT201—3浓度为1250mg／L、CDS-1浓度为0．05％时,体系在地层条件下的表现黏度可达72．37mPa·s。在模拟油层渗透率及非均质变异系数的岩心上,注入0．30PV二元复合体系及0．10Pv聚合物保护段塞时,可比水驱提高采收率20．91％OOIP。     

全长黏结式锚索对软岩洞室的加固效应研究

采用为研究软岩洞室中自由式预应力锚索加固效应而进行的物理模型试验中的相关参数,在假设注浆体与岩石孔壁之间的摩阻力与其之间的相对位移存在比例关系,以及该摩阻力最大值与岩体力学性质,运用岩体与锚索单元网格自由剖分的方法,通过数值计算,对全长黏结式锚索在软岩洞室中的加固效应进行了研究,得到了洞壁开挖位移曲线以及锚柱表面摩阻力、锚柱轴力的分布曲线。研究结果表明,锚固洞室开挖位移大大减少;位于岩体活动区及稳定区的锚柱体上的摩阻力变化幅度不同;锚柱最大轴力点的位置是变化的等结论。     

利用LiDAR点云提取有地形约束的光滑海岸线

针对传统海岸线提取算法误差大、在地形突变区域形变大的缺点,提出了一种基于离散LiDAR点云提取有地形约束海岸线的方法.首先,通过离散点云构建约束三角网,减少内插规则格网的误差并且保证海岸线不穿越地形结构;其次,进行顾及地形结构的点云高程修正,在数据源上缓解海岸线的平滑问题;最后采取二次多项式法消除毛刺,利用动态阈值张力样条函数内插生成光滑海岸线.     

Study of water tension differences in heterogeneous sandy soils using surface ERT

Herbaceous vegetation in the Sahel grows almost exclusively on sandy soils which preferentially retain water through infiltration and storage. The hydrological functioning of these sandy soils during rain cycles is unknown. One way to tackle this issue is to spatialize variations in water content but these are difficult to measure in the vadose zone. We investigated the use of Electrical Resistivity Tomography (ERT) as a technique for spatializing resistivity in a non-destructive manner in order to improve our knowledge of relevant hydrological processes. To achieve this, two approaches were examined. First, we focused on a possible link between water tension (which is much easier to measure in the field by point measurements than water content), and resistivity (spatialized with ERT). Second, because ERT is affected by solution non-uniqueness and reconstruction smoothing, we improved the accuracy of ERT inversion by comparing calculated solutions with in-situ resistivity measurements. We studied a natural microdune during a controlled field experiment with artificial sprinkling which reproduced typical rainfall cycles. We recorded temperature, water tension and resistivity within the microdune and applied surface ERT before and after the 3 rainfall cycles. Soil samples were collected after the experiment to determine soil physical characteristics. An experimental relationship between water tension and water content was also investigated. Our results showed that the raw relationship between calculated ERT resistivity and water tension measurements in sand is highly scattered because of significant spatial variations in porosity. An improved correlation was achieved by using resistivity ratio and water tension differences. The slope of the relationship depends on the soil solution conductivity, as predicted by Archie's law when salted water was used for the rain simulation. We found that determining the variations in electrical resistivity is a sensitive method for spatializing the differences in water tension which are directly linked with infiltration and evaporation/drainage processes in the vadose zone. However, three factors complicate the use of this approach. Firstly, the relation between water tension and water content is generally non-linear and dependent on the water content range. This could limit the use of our site-specific relations for spatializing water content with ERT through tension. Secondly, to achieve the necessary optimization of ERT inversion, we used destructive resistivity measurements in the soil, which renders ERT less attractive. Thirdly, we found that the calculated resistivity is not always accurate because of the smoothing involved in surface ERT data inversion. We conclude that further developments are needed into ERT image reconstruction before water tension (and water content) can be spatialized in heterogeneous sandy soils with the accuracy needed to routinely study their hydrological functioning.     

岩质边坡楔形体锚索加固方向角三维优化设计

以岩质边坡中常见的楔形体滑动为研究对象,研究其最优锚固方向角的计算方法。将锚索自由段单位长度能提供的最大抗滑增量作为目标控制变量,将坡面和两组滑动面的特征参数与锚索设计参数作为优化控制自变量,通过坐标系转换建立线性方程组对锚索的预拉力进行分解,得到用于锚固方向角三维优化的新计算方程。在该方程的基础上,借助导数法和Matlab软件中的fmincon函数分别对锚索加固方向与坡面走向垂直的二维优化方式和锚索加固方向不受限制时的三维优化方式下的锚固方向角进行了优化。最后通过算例与工程实例分析相结合,证明了推荐的最优锚固方向角计算方法的有效性与先进性。新方法可进一步提高锚索的锚固效益,减少锚索的总用量,降低边坡的支护费用。     

拉索端部弹性约束振动控制研究(Ⅱ)——试验验证

在索端沿轴向设置弹性约束,对拉索振动轴向被动控制进行了试验研究。研究了支座移动对拉索振动频率的影响;验证了弹性约束对拉索振动的减振效果,讨论了阻尼系数和弹簧刚度对减振效果的影响;最后验证文献[10]中理论研究的正确性。     

Dynamic Analysis of Towed and Variable Length Cable Systems

Towed cable systems are frequently used in marine measurements where the length of the towed cable varies during launch and recovery. In this paper a novel method for modeling variable length cable systems is introduced based on the finite segment formulation. The variable length of the towed cable is described by changing the length of the segment near the towing point and by increasing or decreasing the number of the discrete segments of the cable. In this way, the elastic effects of the cable can be easily handled since geometry and material properties of each segment are kept constant. Experimental results show that the dynamic behavior of the towed cable is consistent between the model and the physical cable. Results show that the model provides numerical efficiency and simulation accuracy for the variable length towed system.     

Nonlinear Dynamic Responses of Tension Leg Platform with Slack-Taut Tether

The slack-taut state of tether is a particular adverse circumstance,which may influence the normal operation state of tension leg platform (TLP).The dynamic responses of TLP with slack-taut tenor are studied with consideration of several nonlinear factors introduced by large amphliude motions.The time histories of stresses of tethers of a typical TLP in slacktaut state are given.In addition,the sensitivities of slack to stiffness and mass are investigated by varying the stiffness of tether and mass of TLP.It is found that slack is sensitive to the mass of TLP.The critical curved surfaces (over which indicates the slack) for the increase of mass are obtained.