Assistant pullback technique for main span closure of Sutong Bridge

Sutong Bridge is a cable-stayed steel box girder bridge with a main span of 1 088 m. The erection of upper structure adopts geometry control method and requires no change to the unit＇ s size and the structure＇ s none-stress geometry. Before main span closure, the cantilever of girder reaches 540.8 m, the structure state is noticeably influenced by extemal circumstances, the main span closure face great difficulty. By abstracting the advantage of the pullback method abroad and the domestic temperature-cutting method, a new assistant pullback method have put forward and bring into practice actually. In this paper, the analysis key point of practice conditions, key parameter of practice, main measures of the method and the performance is introduced.

Quantitative criteria for identifying main flow channels in complex porous media

To identify the type of main flow channels of complex porous media in oil and gas reservoirs,the"main flow channel index"is defined as the ratio of comprehensive permeability obtained from well test to matrix permeability obtained from core analysis or well logging.Meanwhile,a mathematical model is established based on equivalent flow assumption,the classification method for main flow channels is put forward,and quantitative characterization of main flow channels is realized.The method has been verified by analysis of typical gas reservoirs.The study results show that the"main flow channel index"can quantitatively classify types of flow channels.If the index is less than 3,the matrix pore is the main flow channel;if the index is between 3 and 20,the fracture is the main flow channel and the matrix pore acts as the supplement one;if the index is more than 20,the fracture is the only seepage channel.The dynamic analysis of typical gas reservoirs shows that the"main flow channel index"can be used to identify the type of flow channel in complex porous media,guiding the classified development of gas reservoirs,and avoiding development risk.

Seismic analysis of a long-span continuous steel truss-arch bridge across the Yangtze River

In this paper, an FEM （Finite Element Method） model is established for the main span of the bridge, with the main box arch and suspender members modeled by beam elements, truss members by truss elements, and the orthotropic steel deck by plate elements. The natural frequencies and mode shapes are acquired by the eigen-parameter analysis. By input of a typical earthquake excitation to the bridge system, the dynamic responses of the bridge, including the displacement and accelerations of the main joints of the structure, and the seismic forces and stresses of the key members, are calculated by the structural analysis program, based on which the main laws of the seismic responses of the bridge are summarized, and the safety of the structure is evaluated.

Main flow channel index in porous sand reservoirs and its application

Based on well test interpretation,production performance analysis,overburden permeability and porosity test,gas-water core flooding test and high-pressure mercury injection,a quantitative correlation has been built of in-situ effective permeability with routine permeability and water saturation,and the ranges of Main Flow Channel Index(MFCI)are determined for different permeability levels in porous sand gas reservoirs.A new method to evaluate the in-situ effective permeability of porous sand reservoir and a correlation chart of reserves producing degree and main flow channel index are established.The results reveal that the main flow channel index of porous sand gas reservoirs has close correlation with routine matrix permeability and water saturation.The lower the routine matrix permeability and the higher the water saturation,the lower the MFCI is.If the routine matrix permeability is greater than 5.0×10-3,the MFCI is generally greater than 0.5.When the routine matrix permeability is from 1.0×10-3 to 5.0×10-3,the MFCI is mainly between 0.2 and 0.5.When the routine matrix permeability is less than 1.0×10-3,the MFCI is less than 0.2.The evaluation method of in-situ effective permeability can be used to evaluate newly discovered or not tested porous sand gas reservoirs quickly and identify whether there is tight sand gas.The correlation chart of reserves producing degree and main flow channel index can provide basis for recoverable reserves evaluation and well infilling,and provide technical support for formulation of reasonable technical policy of gas reservoir.

Pore structure characteristics of the relative water-resisting layer on the top of the Ordovician in Longgu Coal Mine

In order to study the permeability and water-resisting ability of the strata on the top of the Ordovician in Longgu Coal Mine, this paper tested the permeability and porosity of the strata, investigated the fracture and pore structure features of the strata, and identified the main channels which govern the permeability and water-resisting ability of the strata. The permeability of the upper, central and lower strata shows as 2.0504 × 10^-3-2.782762× 10^-3, 4.1092 × 10^-3 -7.3387 × 10^-3 and 2.0891 ×10^-3-3.2705 × 10-3 μm^2, respectively, and porosity of that is 0.6786-0.9197%, 0.3109-0.3951% and 0.9829-1.8655%, respectively. The results indicate that： （I） the main channels of the relative water-resisting layer are the pore throats with a diameter more than 6 μm; （2） the major proportion of pore throats in the vertical flow channel and the permeability first increases and then sharply decreases; （3） the fractures occurring from the top to 20 m in depth of the strata were filled and there occurred almost no fracture under the depth of 40 m; and （4） the ratio of turning point of the main flow channel in the strata on top of Ordovician can be used to confirm the thickness of filled water-resisting lavers.

深井松软围岩煤巷采动增跨效应及防控技术

针对深井松软煤巷围岩变形严重、巷道支护困难等问题,以城郊煤矿LW21106工作面沿空巷道为工程背景,建立了采动巷道增跨模型,揭示了采动增跨效应演化机理。通过构建巷道顶板横纵弯曲梁模型,指出顶板横向受力、巷道等效跨度、煤岩强度是巷道围岩损伤破坏的主控因素,提出了采动增跨效应防控对策并进行工业性试验。研究结果表明:受采动影响,巷道经历“初始围岩稳定—围岩裂隙发育扩展—围岩剪切破坏加剧—等效跨度增加”过程;巷道顶板最大正应力与应力集中系数、顶板等效跨度、巷道断面尺寸及埋深成正相关关系;巷道顶板在高应力环境下易发生拉剪破坏,增加顶板锚索数量以及锚索预紧力有利于增强顶板初期完整性。基于巷道变形破坏主控因素,提出“围岩加固–卸压–强化支护”协同防控策略;针对现场条件,采用煤柱侧向切顶+注浆加固并对破碎区域补充锚索强化支护的防控技术。现场监测结果表明,煤柱帮最大移近量为18.89cm,顶板下沉量为25.86cm,两帮移近量为29.65 cm,有效控制了煤巷围岩变形,为深井松软围岩巷道变形控制提供了参考。

同步辐射装置主信号源的扩展方法研究

主信号源是同步辐射装置的关键组成部分之一,它不仅用于产生同步辐射光源各子系统所需的稳定度极高的参考信号,还用于生成整个装置的控制系统所需的高精度工作时钟。一般使用射频信号源作为主信号源,而商业射频信号源一般只配备单输出通道,远远不能满足同步辐射装置的需要,使用传统功分器对主信号通道进行扩展又存在幅度衰减、精度下降且相位不一致的问题。为解决上述问题,利用射频芯片AD9361,研究了对主信号源的单路输出进行扩展的方法。该方法可根据用户需求完成相应数量的信号通道扩展,设计了AD9361芯片和FPGA主控模块相结合的硬件架构。搭建实验平台,开展了射频信号源在C波段扩展的实验研究,对所提出的扩展方法进行实验验证。实验结果表明,该方法能保证扩展信号的幅度、频率与相位与主信号保持高度一致。

四主缆大跨悬索桥抗震性能分析及减震措施优化

以燕矶长江大桥为工程背景,首先,采用动力非线性时程法分析了燕矶长江大桥抗震性能,并研究了设置电涡流-摩擦组合型阻尼器和黏滞阻尼器对大跨悬索桥抗震性能的影响;然后,对附加电涡流-摩擦组合型阻尼器摩擦力、阻尼系数和阻尼指数开展了参数敏感性分析;最后,从耗能角度分析地震作用下电涡流-摩擦组合型阻尼器减震特点.结果表明:在E2地震作用下,桥塔关键截面抗弯能力均大于弯矩需求;在“纵向+竖向”地震作用下梁端纵向位移较大.设置塔梁处纵桥向阻尼器后,可有效降低主桥梁端纵向位移;增大摩擦力、阻尼系数与降低阻尼指数均可提升梁端纵向地震响应的控制效果,但参数变化对桥塔控制截面的地震响应影响较小.阻尼系数较大时,电涡流阻尼主导了电涡流-摩擦组合型阻尼器耗能,相较于黏滞阻尼器,电涡流-摩擦组合型阻尼器对梁端纵向位移控制效果更好.

基于工程经济性的公路悬索桥主缆最优垂跨比研究

为寻求工程经济性最优的公路悬索桥主缆垂跨比,以我国近年多座采用混凝土桥塔的单跨公路悬索桥为背景,建立主缆、锚碇、桥塔基础工程量的直接函数模型和桥塔塔身工程量的非线性函数拟合模型,对跨度750~2250 m、单层车道数4~8及双层车道数6+4、垂跨比1/14~1/6共952种布置形式的悬索桥进行大范围关于主缆垂跨比的工程经济性研究,并以2座实桥为算例分析主缆垂跨比对悬索桥静、动力性能及抗风性能的影响。结果表明:主缆垂跨比对悬索桥工程经济性影响显著;悬索桥主缆最优垂跨比与跨度相关,而车道数、加劲梁荷载集度的影响相对较小,涉水和不涉水的差异也不显著;基于工程经济性考虑,跨度750~2250 m的悬索桥主缆最优垂跨比为1/6.5~1/8.5,比经验值增大较多。2座实桥算例分析表明随着垂跨比增加,加劲梁挠度和活载应力有所增加,抗风性能略有提升,建议方案设计阶段加大垂跨比研究范围、对工程经济性和桥梁力学性能进行综合比选。

深江铁路洪奇沥公铁大桥主桥设计关键技术

研究目的:洪奇沥公铁大桥是深江铁路的控制性工程,主桥采用主跨808 m公铁合建斜拉桥一跨跨越洪奇沥水道,上层布置8车道城市快速路,下层布置4线铁路。结合建设条件、结构特点及使用性能,对主桥结构体系、主梁横断面及结构形式、索-塔锚固结构、施工方法等关键技术展开研究,确定技术合理可行和经济节约的设计方案。研究结论:(1)首创了短边跨叠合板-桁组合梁斜拉桥结构体系,主桥长度减少20%,节省工程投资;(2)首次在4线铁路公铁合建斜拉桥上采用倒梯形双主桁截面,桥面布置紧凑、受力明确;(3)提出的边跨主梁采用矩形钢管混凝土叠合板-桁组合结构,集结构受力和锚固压重于一体,施工便捷;(4)发明了“自平衡交叉锚固+齿块锚固”的索-塔混合锚固方式,技术经济性高;(5)钢主梁创新采用“纵向大节段+横向分块”施工方法,解决了超宽超高超重整节段钢桁梁运输受既有桥净空限制的难题;(6)本研究成果可为公铁合建桁梁斜拉桥设计提供参考或借鉴。

基于多PRI脉压回波的单通道雷达干扰分离方法

研究了一种基于盲源分离的单通道雷达有源相干干扰抑制方法。针对伴随式干扰场景,在间歇采样转发干扰、部分脉冲密集转发干扰等有源相干干扰并存的条件下,建立了基于脉冲压缩的多脉冲重复间隔采样抗主瓣有源相干干扰模型并对其可行性进行了证明。针对现有单通道盲源分离方法在时域进行分离效果有限的问题,提出对脉压后的距离维数据进行盲源分离的思想,可在一定程度上抑制噪声对盲源分离的影响。同时,由于目标信号和干扰信号在脉冲压缩后重合度较低,可获得更好的分离效果。仿真和实测结果表明,在多个干扰源存在的条件下,本方法可有效分离真实目标回波和干扰回波。当信噪比大于5 dB时,目标脉压回波相似系数接近100%;选取虚拟通道数越多,分离效果越好。

论中国特色调解型行政复议模式

调解原则载入总则规定之中,是《行政复议法》修改的一大亮点,预示着中国特色调解型行政复议模式的生成。依法化解矛盾纠纷成为各级政府分内职责,行政争议实质化解成为新兴政法话语,复议化解行政争议主渠道地位的实现,共同构成了中国特色调解型行政复议模式的社会背景。就规范内涵而言,调解优先、应调尽调是新模式的基本特质,调解覆盖到各类型行政复议案件、贯穿于行政复议办理全过程、调解结案方式和效力多样化则是新模式的核心要义。中国特色调解型行政复议模式的有效运作,需要从加强行政复议人员能力建设、建立科学考评体系和充分借助体制内外力量等方面予以保障。中国特色调解型行政复议模式的发展,将重塑行政争议化解整体格局,进一步推进国家治理体系和治理能力的现代化。

对发挥行政复议主渠道作用的反思与制度重构

当前,我国理论界和实务界所面临的一个重大挑战是如何将行政复议作为解决行政争议的主渠道。本文分析了我国行政复议的性质,针对最新审议通过的《中华人民共和国行政复议法(修订草案)》,提出我国行政复议需要解决的问题。通过对我国行政复议的受案范围、复议渠道以及行政复议体制机制等方面的完善,从而实现行政复议主渠道作用,以推动行政复议真正发挥其化解行政争议的功能,为行政相对人提供更加便捷的救济途径。

论行政复议在化解税务行政争议中的主渠道作用

实质化解税务行政争议有利于和谐税收征纳关系、保护纳税人合法权益。相比于税务行政诉讼,税务行政复议机关的税收专业性更强、审理权限更大、审理范围更广。但因部分纳税人难以按税务机关的要求补缴税款,缴纳滞纳金,无法取得行政复议权,导致中国税务行政案件不多。`税务行政复议机关的分散导致专业化税务行政复议人才队伍的建设存在困难,税务行政复议机关的公正性、独立性等受到质疑。无条件赋予纳税人行政复议权,集中税务行政复议机关等措施将有利于充分发挥税务行政复议化解税务行政争议的主渠道作用。

关于黄河与河套古湖河湖关系演变的假说性分析——兼论对黄河内蒙古段生态治理的启示

黄河曾经在流经河套盆地过程中形成吉兰泰、乌兰布和、巴彦淖尔、呼包4个古湖,且在高湖面时期连成统一的“河套古大湖”,其后4湖分离并分别演绎了自己的河湖关系。在研习前人相关成果基础上,通过建立整体假说性解释框架,试图按照历史顺序与逻辑顺序统一的要求对该河段河湖关系的演变过程进行重建,并为与之相关的生态系统的治理提供借鉴。研究认为:主河道构建是黄河主动实施填湖、建堤、造槽并“甩湖”的过程与结果;冲积扇是黄河填湖的主要模式,而冲积扇顶附近凸起则是湖口淤塞、移动并最终筑成黄河自然堤的主要原因;巴彦木仁与磴口两地控制点对形成鄂尔多斯一侧黄河主河道起到了关键性作用;黄河西派在高湖面期间从巴彦木仁湖口注入吉兰泰-乌兰布和古湖,与从北面入湖的黄河水共同促成贺日木西尼古砂嘴及其延伸砂脊生长,并在低湖面期将这两个湖分离。基于对所述黄河历史过往的认识,须尽可能立足高效集成利用有限水资源这一观念,将减灾与适度重造沿河湖泊和绿洲结合,营建可持续的内蒙古段黄河生态体系。

持续冲刷期内黄河下游河床演变特点分析

基于2006年10月至2018年11月黄河下游12个典型断面观测数据,通过分析断面主槽平滩形态特征参数变化率及深泓线和主槽中心线的摆动强度,探讨了持续冲刷期内下游河床的调整变化过程及特点。结果表明:黄河下游断面形态调整表现出既有横向展宽又有冲深下切或淤高态势;河床平面摆动促进了断面主槽形态调整,河相系数变化率与深泓线和主槽中心线摆动强度均成正相关关系;来水来沙条件是主槽形态改变的主要驱动力,且可引起局部河段深泓线摆动强度增大。通过调整小浪底水库的运行模式及布设控导工程可进一步塑造并维持稳定的黄河下游中水河槽。

基于调研数据的部分斜拉桥设计关键参数研究

针对部分斜拉桥设计关键参数缺少足够规范指导的问题,通过对国内外的部分斜拉桥进行设计主要参数调研统计,并与现有相关规范、科研成果进行对比研究,讨论了部分斜拉桥各型结构体系适用性、拉索布置形式,总结给出拉索倾角和间距、边主跨比、塔跨比、索梁刚度比和无索区长度等重要设计参数取值范围。结果表明,拉索倾角一般为11°~35°,主梁上拉索间距一般采用3.5 m~8 m,塔上的拉索间距一般采用0.5 m~1.2 m;3跨布置时,边主跨比一般集中在0.41~0.70,塔跨比宜采用1/3~1/13,索梁刚度比宜小于30;主跨跨中无索区长度与跨径之比宜取0.06~0.21。

土耳其1915恰纳卡莱大桥无索区钢箱梁安装关键技术

土耳其1915恰纳卡莱大桥为主跨2023 m的双塔三跨钢箱梁悬索桥。钢箱梁总长3563 m,边跨及桥塔处无索区钢箱梁均为非标准节段,长度为9.8~43.6 m,吊装重量为344~1330 t,涉及多种吊装方式及节段安装工艺,施工难度大。该桥边跨S33节段定位精度要求高、顶推难度大,利用特殊设计牛腿,顺利实现节段顶推及边跨合龙;边跨焊接线形精度要求高、工序转换复杂,S32和S31节段布设临时吊索系统,确保焊接线形可控;塔区工作平台上的S01、T00和M01单个节段利用特殊设计三向可调支架及导向架施工,确保浮吊吊装安全可靠及定位精度可控;S02和M02节段吊装时与已吊装节段在空间上相互干扰,通过布设牵引荡移系统,顺利实现塔区S02和M02节段缆载吊机大角度吊装及节段荡移;采用吊索调节装置、边跨反拉系统及4台缆载吊机同步抬吊等措施,塔区S01、T00和M01组拼焊接的大节段顺利合龙。

支流入汇对干流航道通航条件影响模拟研究

自然河流由于支流的汇入,在交汇区与干流相互混掺顶托,改变了原有的水流形态,形成复杂的水流结构,对内河船舶航运的操纵性和安全性均造成一定影响。采用数值模拟试验方法,基于分离式(MMG)水动力模型,系统地研究了不同交汇角、汇流比以及干支流河道宽度比情况下交汇区船舶通航条件,即船舶航行时的漂角和偏航距离因素,并以此为基础,基于Design-Export响应面分析软件,得出了无量纲化后的最大偏航距离与交汇角、汇流比以及干支流宽度比之间的响应函数。

Adjustment in the main-channel geometry of the lower Yellow River before and after the operation of the Xiaolangdi Reservoir from 1986 to 2015

Based on the measured discharge,sediment load,and cross-sectional data from 1986 to 2015 for the lower Yellow River,changes in the morphological parameters(width,depth,and cross-sectional geomorphic coefficient)of the main channel are analyzed in this paper.The results show that before the operation of the Xiaolangdi Reservoir(XLDR)from 1986 to 1999,the main channel shrunk continually,with decreasing width and depth.The rate of reduction in its width decreased along the river whereas that of depth increased in the downstream direction.Because the rate of decrease in the width of the main channel was greater than that in channel depth,the cross-sectional geomorphic coefficient decreased in the sub-reach above Gaocun.By contrast,for the sub-reach below Gaocun,the rate of decrease in channel width was smaller than that in channel depth,and the cross-sectional geomorphic coefficient increased.Once the XLDR had begun operation,the main channel eroded continually,and both its width and depth increased from 2000 to 2015.The rate of increase in channel width decreased in the longitudinal direction,and the depth of the main channel in all sub-reaches increased by more than 2 m.Because the rate of increase in the depth of the main channel was clearly larger than that of its width,the cross-sectional geomorphic coefficient decreased in all sub-reaches.The cross-sectional geometry of the main-channel of the lower Yellow River exhibited different adjustment patterns before and after the XLDR began operation.Before its operation,the main channel mainly narrowed in the transverse direction and silted in the vertical direction in the sub-reach above Aishan;in the sub-reach below Aishan,it primarily silted in the vertical direction.After the XLDR began operation,the main channel adjusted by widening in the transverse direction and deepening in the vertical direction in the sub-reach above Aishan;in the sub-reach below it,the main channel adjusted mainly by deepening in the vertical direction.Compared with the rates of decrease in the width and depth of the main channel during the siltation period,the rate of increase in channel width during the scouring period was clearly smaller while the rate of increase in channel depth was larger.After continual siltation and scouring from 1986 to 2015,the cross-sectional geometry of the main-channel changed from wide and shallow to relatively narrow and deep.The pattern of adjustment in the main channel was closely related to the water and sediment conditions.For the braided reach,the cross-sectional geomorphic coefficient was negatively correlated with discharge and positively correlated with suspended sediment concentration(SSC)during the siltation period.By contrast,the cross-sectional geomorphic coefficient was positively correlated with discharge and negatively correlated with SSC during the scouring period.For the transitional and meandering reaches,the cross-sectional geomorphic coefficient was negatively correlated with discharge and positively correlated with SSC.