基于叠前地震纵横波模量直接反演的流体检测方法

流体因子是储层流体识别的重要方法,而叠前地震反演是获得流体因子的有效途径之一.本文从流体因子的构建出发,基于多孔弹性介质岩石物理模型,建立了流体因子与纵横波模量之间的直接关系,避免了流体因子计算所需的密度参数无法准确求取的问题,通过推导基于纵横波模量的Zeoppritz近似方程及弹性阻抗方程,探讨了基于弹性阻抗的纵横波模量直接反演方法,模型与实际应用表明,基于弹性阻抗的纵横波模量直接反演方法合理、可靠,减少了常规方法间接计算纵横波模量带来的累积误差,基于纵横波模量的流体因子计算方法有较好的实际应用效果.     

考虑泊松效应影响的弹塑性荷载传递模型

提出了一种能考虑泊松效应影响的弹塑性荷载传递模型（t-z模型）。该模型既能反映不同材料的桩基在同一土体中抗压承载力的不同,也能反映同一材料桩基在同一土体中桩身抗压摩阻力与抗拔摩阻力的不同,同时还具备模拟循环荷载下t-z曲线滞回特性的能力。根据位移协调算法编制了可用于竖向压、拔荷载作用下单桩响应分析的Matlab程序,利用程序对模型试验进行了模拟,结果对比证明了该模型的适用性。最后分析了桩体弹性模量对压、拔极限摩阻力比值的影响,结果表明,该比值随弹性模量的减小而减小,对于混凝土桩,该值介于0.6～0.8之间,与规范建议的抗拔系数接近。     

激光扫描点云准确快速去噪方法

激光点云数据中孤点和离群点等噪声的自动去除方法是激光点云数据处理的研究热点。本文针对现有孤点的平均点间距阈值探测法存在远距离点云误判的问题,对平均点间距附加距离权重后再根据阈值进行了判断;针对离群点的生长探测法存在效率低的问题,采用均匀八叉树结构以格网为单位进行了生长探测。试验证明了改进方法的自适应性和高效性。     

直接地理参考中轨迹插值算法对精度影响的评估

移动测量中定位定姿系统的精度决定了整个系统的精度,为了获得激光扫描仪采样时对应测量系统时间点处的轨迹数据,需要进行插值。本文介绍了移动测量系统和直接地理参考,给出了典型的插值算法,以笔者所在学校车载移动测量系统的实测数据进行轨迹插值测试,对各种插值算法在不同移动速度下的轨迹插值结果的精度和效率进行了比较,并分析了对激光脚点定位精度的影响。结果表明,对位置进行移动线性插值,对姿态进行移动自然样条插值可以取得较好的精度和效率。     

Factors influencing in-situ leaching of uranium mining in a sandstone deposit in Shihongtan,Northwest China

The Shihongtan uranium deposit in northwest China is a sandstone-type deposit suitable for alkaline in-situ leaching exploitation of uranium. Alkaline leaching tends to result in CaCO3 precipitation there by affecting the porosity of the ore-bearing aquifer. CaCO3 deposits can also block pumping and injection holes if the formulation parameters of the leaching solution are not well controlled. However, controlling these parameters to operate the in-situ leaching process is challenging. Our study demonstrates that the dissolved uranium concentration in the leaching solution increases as HCO3－ concentration increases. Therefore, the most suitable HCO3－ concentration to use as leaching solution is defined by the boundary value of the HCO3－ concentration that controls CaCO3 dissolution-precipitation. That is, the dissolution and precipitation of calcite is closely related to pH, Ca2+ and HCO3－ concentration. The pH and Ca2+ concentration are the main factors limiting HCO3－ concentration in the leaching solution. The higher the pH and Ca2+ concentration, the lower the boundary value of HCO3－ concentration, and therefore the more unfavorable to in-situ leaching of uranium.     

重庆市主城区物流园区空间布局及其对城市空间结构的影响

选择现代物流业相对发达的西部地区的中心城市—重庆主城区为典型案例,通过对物流园区实地调研与管理部门的访谈获取论证数据展开案例实证。重庆市主城区的物流园区的案例研究发现：① 物流园区的空间布局具有两大特征：一是围绕城市中心区外围布局,二是沿交通干线或重要交通设施布局;② 物流园区的自身建设是城市开发的重要组成部分,其空间布局对城市空间结构的影响一方面促进和引导城市建成区的向外扩张,另一方面体现在物流园区通过自身建设和对周边地区的带动改变城市的用地结构和内部用地功能。最后分析总结了物流园区对城市空间结构影响的4种机制：垄断机制、配套机制、地价机制和聚集机制。     

西藏玛旁雍错湿地资源及其保护利用

玛旁雍错湿地是西藏高原典型的脆弱生态系统,拥有比较丰富的动植物和旅游资源,具有重要的生态保护利用价值。玛旁雍错湿地目前存在的主要问题为:湖泊周围固体废弃物污染较严重;过度放牧、湿地周边植被破坏、湿地周围蝗虫和鼠(兔)害严重、气候变暖干等因素导致湿地系统内土地沙化和荒漠化日趋加剧;湿地面积日趋萎缩;野生动物资源受到严重威胁。针对上述问题,提出了该湿地资源保护利用的具体措施。     

高放废物处置库甘肃北山预选区地下水的形成

在高放废物处置库场地选择和性能评价中,水文地质特征是最重要的因素之一,地下水的形成则是水文地质研究中的首要问题。在水文地质、地下水化学、同位素、CFC、地下水动态等资料综合分析的基础上,探讨了高放废物处置库甘肃北山预选区地下水的形成问题。研究结果表明,北山地区地下水以赋存于变质岩、岩浆岩、碎屑岩、碳酸岩节理、裂隙中的基岩裂隙潜水为主,地下水化学成分具有明显的水平分带性特征,地下水动态类型主要为入渗—蒸发—径流型,结合地下水同位素和CFC 特征,认为区内地下水主要由当地大气降水入渗补给形成。浅部地下水主要由现代区内降水补给形成,而深部地下水则可能由地质历史时期降水补给形成。     

数字岩石物理中弹性参数的有限差分计算方法

数字岩石物理利用三维成像技术和数学方法,建立数字岩心,开展多场物理响应模拟,计算岩石的等效弹性参数,为岩石物理学研究开拓了新的领域.本文发展了一种基于高阶有限差分的岩石模量数值计算的新方法,该方法便于理解,容易实现,占用内存相对较少,计算效率高,结果合理,弥补了常规岩石物理实验周期长,成本高,误差大等不足.该方法将三维数字岩心样本嵌入一个具有与岩心样本骨架颗粒相同弹性性质的区域中扩充成一个新模型,测量由数字岩石样本非均匀结构带来的纵波或横波峰值振幅的时间差,利用该时间差(相对参考模型)估算纵横波的等效速度,进而求取等效弹性模量.理论模型和实际岩心的计算结果表明,数值模拟结果与实验结果有较高的吻合度,验证了该方法的合理性.     

REVIEW ON IN-SITU COSMOGENIC 14C DATING AND POTENTIAL APPLICATION IN PALEOEARTHQUAKE

Over the last two decades, in-situ cosmogenic ¹⁴C dating has become an import tool in Quaternary geology and is recognized to geoscientists because of its potential to provide information on exposure age and process rate estimates for geomorphic studies. The in-situ cosmogenic radiocarbon has a relatively short half-life(5730 yr)and is substantially more sensitive than all the other cosmogenic nuclides used so far. It is therefore particularly useful to determine surface-exposure ages of Holocene landforms and quantify erosion rates in rapidly denuding landscapes during the past few tens of thousands of years. Moreover, in situ ¹⁴C is produced in quartz which is both highly resistant to weathering and common in nature, so it can be used in combination with other in-situ cosmogenic nuclides such as ³He, ¹⁰Be,²¹Ne,²⁶Al, and ³⁶Cl to constrain complex exposure histories involving burial and/or erosion occurring over the past 25ka. The age and slip rate of Holocene normal fault have been undoubtedly a challenge for seismologists to be faced with as result from lack of appropriate late Quaternary sediment. Recently, the cosmogenic nuclides such as ³⁶Cl of preserved, seismically exhumed normal fault scarps were used to identify the last few major earthquakes and recover their ages and displacements through the modeling of the content of ³⁶Cl in the scarp rocks. This paper mainly summarizes the development of in-situ ¹⁴C dating, including its research history, production rate estimate, production mechanism, chemical behavior and experimental method. The potential application of in-situ ¹⁴C dating to recovering past earthquakes, their timing, and the regularity of their recurrence for preserved, seismically exhumed normal fault scarps is also introduced.