川南地区页岩气井平台钻前电法勘探方法对比研究

四川南部页岩气钻井过程中,在1000 m以浅常钻遇岩溶、裂隙,造成工程和环保等事故,为避免以上事故发生,在钻井前开展地面电法勘探,提前预测设计井位下伏岩溶、裂隙等影响钻井的不良地质异常体位置及规模.这里在川南宜宾页岩气示范区,通过研究区物性特征分析、常用地面物探方法选择、参数试验、主要不良地质体的物性识别、综合运用效果...     

南澳岛海域表层沉积物重金属分布、富集与污染评价

南澳岛是广东南澳县的主岛, 周边海域的环境保护被置于当地社会经济发展的重要位置。为此, 2004年 5月、7月选择以水产养殖为主的后江湾和白沙湾及以旅游为主的青澳湾作为研究对象, 对南澳岛海域重金属的 含量、分布、富集及污染状况进行了调查与评价。结果表明该海域重金属元素的平均含量为Cd: 0.19mg.kg-1, Cr: 26.86mg.kg-1, Cu: 20.71mg.kg-1, Ni: 22.78mg.kg-1, Pb: 35.67mg.kg-1, Zn: 79.48mg.kg-1, 低于近岸经济发达海域, 但高于受人类活动影响较小的外海; 在分布特征上表现为湾口高于湾内, 养殖区高于非养殖区的总趋势, 但在各海湾之间重金属含量并无显著差异, 表明南澳岛海域重金属主要来源于地表径流输入。该海域以城市污水中代表元素Cu (Cf = 2.75), Pb (Cf = 2.27)富集为主; 以海洋沉积物质量标准、沉积物质量基准和美国太平洋沿岸基线值评价, 南澳岛海域环境质量均处于健康状态, 但其潜在污染效应仍值得关注。     

河南信阳板栗生长的土壤地球化学评价

信阳板栗是河南省名特优农产品之一,但是有关信阳板栗生长环境的土壤地球化学方面研究较少,致使目前板栗的种植、规划等缺乏理论依据.本文对河南信阳板栗种植区土壤样品的地球化学元素进行测试分析,研究了土壤地球化学元素与板栗品质之间的相关关系.分析结果显示,板栗品质与土壤有机质、阳离子交换量、pH值、全氮、氨态氮、有效锌、有效铜、有效锰、有效硼呈正相关关系,并且与氨态氮、有效锌、有效铜、有效锰、有效硼的相关性很强,说明耕作土壤增加这些元素的含量有利于提高板栗品质,土壤pH值越接近5～6的最适宜范围,板栗品质越好;板栗品质与土壤容重、速效磷、速效钾呈负相关关系,认为在施用磷肥和钾肥增加速效磷、速效钾,提高板栗产量的同时,应注意板栗品质下降的问题.值得注意的是,研究区土壤中有效硼含量低于土壤临界值,是限制板栗品质的重要因素.本研究为提高信阳板栗品质、规划板栗园的种植、科学管理和合理施肥提供了依据.     

小兴安岭“古元古代”东风山群的形成时代及其构造意义:锆石U-Pb年代学证据

报道了黑龙江省东部小兴安岭东风山群亮子河组和红林组锆石的U-Pb定年结果,并讨论了东风山群的所属时代和构造属性。采自该群的大多数锆石呈自形—半自形晶,显示出典型的岩浆生长环带或条痕状吸收,暗示其岩浆成因,极少数的锆石具有经变质作用形成的暗色增生边。定年结果表明:采自东风山铁矿附近的亮子河组二云母片岩中锆石U-Pb定年结果产生了821 Ma、1 286 Ma、1 396 Ma、1 504～1 595Ma、1.8Ga和2.5Ga年龄众数;采自亮子河组标准剖面的黑云母石英片岩和变质粉砂岩中锆石U-Pb定年结果分别产生了425Ma、453Ma、485Ma、506Ma和288Ma、452Ma、486Ma、699Ma、801Ma、900Ma年龄众数;东风山群上部红林组含炭质粉砂质板岩中锆石U-Pb定年结果产生了275Ma、760Ma、781Ma年龄众数,而红林组中的花岗质片麻岩(原岩为花岗岩,侵入到含炭质粉砂质板岩中)锆石U-Pb定年结果为271Ma。根据上述定年结果,结合区域岩浆事件,可以判定:位于东风山铁矿处的亮子河组沉积于新元古代晚期,这是区域上首次发现具有准确同位素年龄的前寒武纪地层;东风山群亮子河组标准剖面处的黑云母石英片岩和变质粉砂岩应形成于早古生代晚期和晚古生代;而东风山群红林组的形成时代应为晚古生代晚期(275～271Ma)。上述结果揭示,小兴安岭东风山群是由不同时代沉积岩和变形的火成岩所构成,主体形成于古生代,部分地层为新元古代晚期沉积;这些地层的物源主要来源于周边的古生代地质体和少量的前寒武纪基底残片。     

Numerical simulation on the process of saltwater intrusion and its impact on the suspended sediment concentration in the Changjiang (Yangtze) estuary

To study the relationship between sediment transportation and saltwater intrusion in the Changjiang (Yangtze) estuary, a three-dimensional numerical model for temperature, salinity, velocity field, and suspended sediment concentration was established based on the ECOMSED model. Using this model, sediment transportation in the flood season of 2005 was simulated for the Changjiang estuary. A comparison between simulated results and observation data for the tidal level, flow velocity and direction, salinity and suspended sediment concentration indicated that they were consistent in overall. Based on model verification, the simulation of saltwater intrusion and its effect on sediment in the Changjiang estuary was analyzed in detail. The saltwater intrusion in the estuary including the formation, evolution, and disappearance of saltwater wedge and the induced vertical circulation were reproduced, and the crucial impact of the wedge on cohesive and non-cohesive suspended sediment distribution and transportation were successfully simulated. The result shows that near the salinity front, the simulated concentrations of both cohesive and non-cohesive suspended sediment at the surface layer had a strong relationship with the simulated velocity, especially when considering a 1-hour lag. However, in the bottom layer, there was no obvious correlation between them, because the saltwater wedge and its inducing vertical circulation may have resuspended loose sediment on the bed, thus forming a high-concentration area near the bottom even if the velocity near the bottom was very low during the transition phase from flood to ebb.     

Numerical simulation on the process of saltwater intrusion and its impact on the suspended sediment concentration in the Changjiang(Yangtze)estuary

To study the relationship between sediment transportation and saltwater intrusion in the Changjiang (Yangtze) estuary, a three-dimensional numerical model for temperature, salinity, velocity field, and suspended sediment concentration was established based on the ECOMSED model. Using this model, sediment transportation in the flood season of 2005 was simulated for the Changjiang estuary. A comparison between simulated results and observation data for the tidal level, flow velocity and direction, salinity and suspended sediment concentration indicated that they were consistent in overall. Based on model verification, the simulation of saltwater intrusion and its effect on sediment in the Changjiang estuary was analyzed in detail. The saltwater intrusion in the estuary including the formation, evolution, and disappearance of saltwater wedge and the induced vertical circulation were reproduced, and the crucial impact of the wedge on cohesive and non-cohesive suspended sediment distribution and transportation were successfully simulated. The result shows that near the salinity front, the simulated concentrations of both cohesive and non-cohesive suspended sediment at the surface layer had a strong relationship with the simulated velocity, especially when considering a 1-hour lag. However, in the bottom layer, there was no obvious correlation between them, because the saltwater wedge and its inducing vertical circulation may have resuspended loose sediment on the bed, thus forming a high-concentration area near the bottom even if the velocity near the bottom was very low during the transition phase from flood to ebb.     

非极限主动土压力计算方法初探

针对未达到极限位移的刚性挡土墙,提出了一种简单可行的主动土压力计算方法。根据反映墙后主动区土体应力-应变性状的卸荷应力路径试验确定的应力-应变关系,建立非极限状态摩擦角与墙体位移的关系。对于未达到极限位移的挡土墙,结合已取得的位移与摩擦角之间的关系,采用与滑裂面相平行的微条对墙后滑动楔体进行划分,对微条进行受力分析,建立平衡方程,推导了滑裂面的倾角,从而得到非极限主动土压力计算公式。随后与一例模型试验数据作了对比分析,计算值与实测值基本吻合,仅在墙下部1/3墙高范围内存在一定的差距。研究表明,所提出的计算方法能够用于计算处于非极限状态下挡土墙的土压力,具有一定的理论意义和工程参考价值。     

局部剪切破坏模式下的无重地基承载力

局部剪切破坏是一种常见的地基破坏模式,该破坏模式下的地基承载力理论计算方法尚不完善,对无重地基局部剪切破坏的极限承载力理论进行了研究。首先从破坏时破裂面延伸位置的角度完善了浅基础3种破坏模式的划分标准。对于局部剪切破坏,土体强度并未完全发挥出来,潜在破坏区处于非极限状态,所以将土体强度逐渐发挥的概念引入地基承载力中,通过适当的假设,建立了局部剪切破坏模式下无重介质地基承载力的理论计算方法,并与已有的经典成果进行比较分析,印证了该方法的合理性。研究成果为解决局部剪切破坏模式下地基承载力的计算提供了理论参考。     

水利系统气象工作座谈会在京召开

1990年4月5～6日,第一次水利系统气象工作座谈会在北京召开。会议由水利部水文水利调度中心主持,来自各流域机构、丹江口水利工程枢纽及河海大学的代表参加了会议。与会代表介绍了各自单位开展防汛气象服务工作的情况和经验体会,并提出了目前存在的问题。大家     

切沟侵蚀预报研究进展与展望

切沟侵蚀是重要的土壤侵蚀类型,是小流域侵蚀泥沙的主要来源。准确预报切沟侵蚀空间分布及其强度的时空变化,对于优化小流域水土保持措施配置、维持区域粮食产能和保障区域生态安全,具有重要的理论和实践意义。地形临界模型、敏感性评价、切沟形态特征经验关系、侵蚀预报模型和景观演变模型是预测切沟发育部位、评价发育概率或估算切沟侵蚀强度的主要方法。从这些方法的基本思路与原理出发,系统分析了相关研究进展,对比了研究结果的差异并评价了各方法的优缺点。未来研究需聚焦切沟监测方法优化与数据积累、切沟演变过程与数据可比性、预报方法遴选及区域适宜性、经验模型研发与参数区域分异,以及切沟侵蚀机理研究与过程模型研发,从而为促进切沟侵蚀预报研究、阻控切沟侵蚀、保障区域社会经济可持续发展提供技术支撑。