绿洲外围植被防风生态效益的紊流模型

风沙灾害严重地威胁着处于茫茫沙漠中的绿洲,绿洲外围植被则是防御风沙危害的绿色屏障。我们选择位于昆仑山北麓塔克拉玛干沙漠南缘受风沙危害极其严重的策勒绿洲外围植被为研究对象,采用k-ε紊流数学模型,对三种典型植被覆盖度:18.75%、37.5%、56.3%,七种风速:4、5、6、7、8、9、10m/s共21种处理的流场细节进行了模拟。每一处理中以4320个数据模拟了i=1,2,…,108,j=1,2,…,20,共2160个点位在u方向和v方向的速度,由此,找出风沙流通过植被区,在顺流方向随植被盖度变化的递变规律,并定量的反映了绿洲外围植被降低风速、降低进入绿洲沙流量的生态效益。试验表明:顺流方向2km厚的植被,盖度由0增至15%~20%,可降低风速37%~40%;增至35%~40%,可降低48%左右;增至55%,可降低54%左右。植被盖度由0增至15%,35%,50%,在地面以上0~20cm的高度内,可不同程度地降低沙流量50%~90%。     

独头巷道超前勘探的有效手段——瑞雷波勘探技术井下超前勘探试验结果述评

迄今,用于煤矿井下独头巷道超前勘探的有效手段寥寥无几。常规的钻探方法费工、费时、效率很低,而且有引起突水的危险。瑞雷波勘探方法是一种使用瑞雷面波作为有效波进行零到几十米范围内地震勘探的新型物探方法。它的测线基距与勘探深度的比值可以达到1∶20以上,即1～2m的测线布置,勘探深度可达30～40m以上。完全适用于独头巷道超前勘探的需要。把这样一种地面地质勘探的方法技术移植到井下,在煤巷、岩巷中进行超前探测断层、空巷、冲刷带的试验并获得成功,无疑为煤矿井下独头巷道的超前探测开创了一种全新的物探手段,必将在煤矿的安全掘进和生产方面发挥重要作用。      

香蒲、灯心草人工湿地的研究——Ⅰ.净化污水的效果

本文研究了种植香蒲Ｔｙｐｈａ ａｎｇｕｓｔｉｆｏｌｉａ或灯心草Ｊｕｎｃｕｓ ｅｆｆｕｓｕｓ的人工湿地对城镇污水和人工不污染物的净化效果,调查了香蒲,灯心草不同季节的生长差异及高浓度污水冲击负荷对其生长的影响。香蒲,灯心草人工湿地净化城镇污水,出水水质总体上达到国家Ⅱ,Ⅲ类地面水标准,灯心草湿地对人工污水中凯氏氮,总磷,化学耗氧量地去除率维持在９４％以上,氨氮的去除率为８２．７％－９９．７％;在正常     

南京玄武湖鱼类暴发性死亡原因分析

南京玄武湖近年来死鱼事件频发,对该湖水生生态系统的长期监测结果表明,湖水富营养化和沉积物污染十分严重。但生礅毒理学研究表明,湖水和沉积物等对鱼类尚未见有急性毒性作用,根据玄武湖鱼类死亡症状,从玄下湖鱼体上分离到一种致力极强的鱼类病原菌－－嗜水气单胞菌,研究了该病原菌的至病特性,并系统地分析了水质主要污染指标,水体富化,藻类种群动态,沉积的污染及其氧化还原层等多种因素对玄武涌鱼类暴发性死亡的发生和流     

饱和黄土场地原位试验及液化势评价

目前,主要依靠室内动力试验对黄土液化势进行评价。由于黄土特殊的结构性,室内试验对其饱和的过程较为复杂,且与实际场地饱和黄土差异明显,导致室内黄土液化试验结果并不能代表现场饱和黄土的抗液化强度。本文选取兰州市西固区寺儿沟村某饱和黄土场地进行钻孔测试,现场实施了标准贯入试验、静力触探试验以及剪切波速测试。应用Robertson的土类指数分类图对该场地不同含水率黄土的土类进行了界定,确定了饱和黄土属于类砂土,有液化势。应用NCEER推荐方法,计算了3组原位试验数据的饱和黄土循环抗力比（CRR）,通过与1976年唐山地震和1999年集集地震液化土CRR对比,得出了饱和黄土抗液化强度很低的结论。     

Shake table study on precast segmental concrete double-column piers

Seismic capacity, including the ultimate load-carrying capacity and ultimate deformation capacity of precast segmental concrete double-column(PSCDC) piers with steel sleeve(SS) connection or grouted corrugated-metal duct(GCMD) connection, has been verified to be similar to those of cast-in-place(CIP) piers by quasi-static tests. However, the lack of knowledge of seismic response characteristics and damage process of PSCDC piers has limited their application in high-intensity seismic areas. Therefore, shake table tests, using variable types and intensities of seismic ground motions, were performed to investigate the seismic behavior of connection joints and to evaluate the seismic performance of PSCDC piers with SS and GCMD connections. Also, a finite element analysis(FEA) model was developed to study the influence of design parameters on the seismic behavior of the piers. The results showed that the main damage in PSCDC piers was caused by the cyclic opening and closing of connection joints. Under high-intensity ground motions, the PSCDC piers had a lower seismic performance than the CIP piers due to a significant decrease of their integrity and stiffness. The seismic performance of PSCDC piers is comparable to CIP piers when using an appropriate initial stress of the prestressing tendons.     

密云水库内湖富营养化现状分析

2001年的调研结果显示,由于网箱养鱼的影响,密云水库内湖已成为富营养水体,库区水体处于中营养水平,但有向富营养化发展的趋势;内湖水体通过侧渗、扩散等途径与库区水体进行物质交换,当水位达到150m以上时,水漫过相隔的窄坝,内湖与库区连为一体,内湖对库区的污染加重,内湖是库区的内污染源,应取消内湖的网箱养鱼,减少内源污染,稳定密云水库水质。     

历史时期希门错湖泊沉积色素记录的古环境变化

湖泊沉积物中色素的含量,种类以及相应的参数是研究湖泊初始生产力和湖泊环境的有效手段之一。本文根据青藏高原东部希门错短柱岩芯ＸＭ９２０１沉积物的色素指标的综合判别,讨论了该地区过去２０００多年来的古环境变化过程和特点,对比分析我国东西部气候记载及冰芯研究,探讨了各气候事故表现形式的异同点。     

华北地区地震空区的统计分析

对华北地区1970—2017年出现的地震空区采用统一的识别标准进行全时空清理研究, 结果表明, 华北地区M≥5地震前出现空区的比例为36.7%, 且华北地区M_L≥3.0地震空区的持续时间与主震震级存在一定的线性正相关关系, 但长轴尺度、 起始震级与主震震级的线性关系不明显; 报准率为0.76, 虚报率为0.24, 漏报率为0.60, R值为0.32, 高于具有97.5%置信水平的R₀值, 表明地震空区这种预测方法在华北地区具有较好的预报效果。     

Geological and geochemical characteristics of the Baogudi Carlintype gold district(Southwest Guizhou,China) and their geological implications

The newly discovered Baogudi gold district is located in the southwestern Guizhou Province,China,where there are numerous Carlin-type gold deposits.To better understand the geological and geochemical characteristics of the Baogudi gold district,we carried out petrographic observations,elemental analyses,and fluid inclusion and isotopic composition studies.We also compared the results with those of typical Carlin-type gold deposits in southwestern Guizhou.Three mineralization stages,namely,the sedimentation diagenesis,hydrothermal(main-ore and late-ore substages),and supergene stages,were identified based on field and petrographic observations.The main-ore and late-ore stages correspond to Au and Sb mineralization,respectively,which are similar to typical Carlin-type mineralization.The mass transfer associated with alteration and mineralization shows that a significant amount of Au,As,Sb,Hg,Tl,Mo,and S were added to mineralized rocks during the main-ore stage.Remarkably,arsenic,Sb,and S were added to the mineralized rocks during the late-ore stage.Element migration indicates that the sulfidation process was responsible for ore formation.Four types of fluid inclusions were identified in ore-related quartz and fluorite.The main-ore stage fluids are characterized by an H2O–NaCl–CO2–CH4±N2system,with medium to low temperatures(180–260℃)and low salinity(0–9.08%NaCl equivalent).The late-ore stage fluids featured H2O–NaCl±CO2±CH4,with low temperature(120–200℃)and low salinity(0–7.48%Na Cl equivalent).The temperature,salinity,and CO2and CH4concentrations of ore-forming fluids decreased from the main-ore stage to the late-ore stage.The calculated δ^13C,d D,and δ^18O values of the ore-forming fluids range from-14.3 to-7.0%,-76 to-55.7%,and 4.5–15.0%,respectively.Late-ore-stage stibnite had δ^34S values ranging from-0.6 to 1.9%.These stable isotopic compositions indicate that the ore-forming fluids originated mainly from deep magmatic hydrothermal fluids,with minor contributions from strata.Collectively,the Baogudi metallogenic district has geological and geochemical characteristics that are typical of Carlin-type gold deposits in southwest Guizhou.It is likely that the Baogudi gold district,together with other Carlin-type gold deposits in southwestern Guizhou,was formed in response to a single widespread metallogenic event.