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351.
Seismic passive resistance with vertical seepage and surcharge 总被引:1,自引:0,他引:1
Jun-Jie Wang Hui-Ping Zhang He-Jun Chai Jun-Gao Zhu 《Soil Dynamics and Earthquake Engineering》2008,28(9):728-737
Present paper focuses on the computation of the seismic passive earth pressure acting on a vertical rigid retaining wall by a soil mass subjected to vertical steady-state seepage and a uniform surcharge load. Based on the basic assumptions of Coulomb's theory and a pseudo-static method of analysis, a general solution for the passive earth pressure containing two coefficients is presented. In the solution, many parameters, such as unit weight of saturated soil, soil effective internal friction angle, soil/wall friction angle, water/soil unit weight ratio, surcharge intensity coefficient, horizontal and vertical seismic acceleration coefficients, Poisson's ratio of soil mass, hydraulic gradient, and coefficients of pore water pressure, are considered. The effects of hydraulic gradient and seismic forces on passive earth pressure coefficient and passive earth pressure distribution are investigated. The results indicate that passive earth pressure increases with increasing hydraulic gradient for downward water flow case, but decreases for upward water flow case, and that the presence of seismic forces induces a reduction in passive earth pressure. 相似文献
352.
不同降雨量下人工重建林土壤性状及微生物特性比较 总被引:1,自引:1,他引:0
分析和比较了甘肃省中部典型黄土丘陵区不同降雨量下人工重建林土壤性状及微生物特性.结果表明:随降水量的增加,土壤含水量升高,pH值变化不明显;土壤有机碳、全氮、微生物量碳、微生物量氮含量均表现为以400 mm降水量为分界线,降水量≥400 mm样地的含量显著高于降水量<400 mm样地(p<0.05);降水量为500 mm样地的全磷、速效磷、速效钾含量及土壤微生物呼吸最高,但土壤微生物呼吸熵为200 mm降水量样地最高;微生物熵变化不显著.相关性分析表明,不同降水量梯度下,土壤理化性质与微生物特性之间存在不同程度的相关性. 相似文献
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岩体多重裂隙网络渗流模型研究 总被引:8,自引:0,他引:8
将岩体中的各种裂隙和孔隙按规模和渗透性分为4级处理,即一级真实裂隙网络、二级随机裂隙网络、三级等效连续介质体系和四级连续介质体系。各级裂隙(孔隙)都形成各自的裂隙网络,并以水量平衡原理为基础建立各级裂隙网络之间的联系,组合形成岩体多重裂隙网络渗流模型,从而较全面地反映了地下水在岩体中的运动规律,并进行了工程实例分析。 相似文献
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356.
为提高全国新一代天气雷达运行保障能力,选取了近5年多新一代天气雷达发生的3211个故障案例,从9个雷达分系统方面,按不同型号,对其发生的故障进行了分类统计分析,同时对导致故障的原因也进行了分析。结果表明:对于长期处在高电压工作状态下,且极易被烧坏的器件,以及运行时间较长的器件,要加强备件的备份,提高备件的可靠性、耐压性;要保持机房环境恒温、恒湿、防尘,使雷达能在良好的环境下工作;加强对电机碳刷碳粉尘的清理,定期地对汇流环进行维护、清洗,防止碳刷磨损,以减小被损坏的机会,以及对长时间在高、低温环境下运转的机械结构器件定期维护,以提高运动部件的可靠性;还要重点保证电力、雷达与外界通信畅通,使资料能够正常上传。 相似文献
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358.
Petrogenesis and geodynamic significance of the Ganhe Formation lavas,eastern Great Xing'an Range,China: Evidence from geochemistry and geochronology
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A‐lei Gu Jing‐gui Sun Ling‐an Bai Yong Zhang Pei‐long Cui Peng Chai Ke‐qiang Zhao Qing‐long Sun Liang Ren Yan‐jun Chen Jun‐quan Zhu 《Island Arc》2016,25(2):87-110
Mesozoic volcanic rocks are widespread throughout the Great Xing'an Range of northeastern China. However, there has been limited investigation into the age and petrogenesis of the Mesozoic volcanics in the eastern Great Xing'an Range. According to our research, the volcanic rocks of the Dayangshu Basin, eastern Great Xing'an Range are composed mainly of trachybasalt, basaltic andesite, and basaltic trachyandesite, with minor intermediate–basic pyroclastic rocks. In this study, the geochemistry and geochronology of the Mesozoic volcanic rocks are presented in order to discuss the petrogenesis and tectonic setting of the Ganhe Formation in the Dayangshu Basin. Zircon U–Pb dating by laser ablation inductively coupled plasma–mass spectrometry indicates that the Mesozoic lavas formed during the late Early Cretaceous (114.3–108.8 Ma). This suite of rocks exhibits a range of geochemical signatures indicating subduction‐related genesis, including: (i) calc‐alkaline to high‐K calc‐alkaline major element compositions; (ii) enrichment of large ion lithophile elements (e.g. Rb, Ba, K) and light rare earth elements (LREEs/HREEs =7.33–9.85); and (iii) weak depletion in high field strength elements (e.g. Nb, Ta, Ti). Furthermore, Sr–Nd–Pb isotopic data yield initial 87Sr/86Sr values of 0.70450–0.70463, positive εNd(t) values of +1.8 to +3.3, and a mantle‐derived lead isotope composition. Combined with the regional tectonic evolution, the results of this study suggest that the Ganhe Group lavas are derived from decompression melting of a metasomatized (enriched) lithospheric mantle, related to asthenospheric upwelling, which resulted from lithospheric mantle delamination and produced extension of the continental margin following the subduction of the Paleo‐Pacific Plate. 相似文献
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360.
Brett R. Baldwin Dora Taggart Yunzhou Chai David Wandor Anita Biernacki Kerry L. Sublette John T. Wilson Claudia Walecka‐Hutchison Camillo Coladonato Bryan Goodwin 《Ground Water Monitoring & Remediation》2017,37(2):58-70
Adaptive site management and aggressive bioremediation in the source zone of a complex chlorinated dense nonaqueous phase liquid (DNAPL) site reduced total chlorinated hydrocarbon mass discharge by nearly 80%. Successful anaerobic bioremediation of chlorinated hydrocarbons can be impaired by inadequate concentrations of electron donors, competing electron acceptors, specific inhibitors such as chloroform, and potentially by high contaminant concentrations associated with residual DNAPL. At the study site, the fractured bedrock aquifer was impacted by a mixture of chlorinated solvents and associated daughter products. Concentrations of 1,1,2,2‐tetrachloroethane (1,1,2,2‐TeCA), 1,1,2‐trichloroethane (1,1,2‐TCA), and 1,2‐dichloroethane (1,2‐DCA) were on the order of 100 to 1000 mg/L. Chloroform was present as a co‐contaminant and background sulfate concentrations were approximately 400 mg/L. Following propylene glycol injections, concentrations of organohalide‐respiring bacteria including Dehalococcoides and Dehalogenimonas spp. increased by two to three orders of magnitude across most of the source area. Statistical analysis indicated that reaching volatile fatty acid concentrations greater than 1000 mg/L and depleting sulfate to concentrations less than 50 mg/L were required to achieve a Dehalococcoides concentration greater than the 104 cells/mL recommended for generally effective reductive dechlorination. In a limited area, chloroform concentrations greater than 5 mg/L inhibited growth of Dehalococcoides populations despite the availability of electron donor and otherwise appropriate geochemical conditions. After implementing a groundwater recirculation system targeting the inhibited area, chloroform concentrations decreased permitting significant increases in concentrations of Dehalococcoides and vinyl chloride reductase gene copies. 相似文献