桩间黄土卸荷湿陷过程中卸荷量计算方法初探     

金鑫  王铁行  郝延周  赵再昆  张亮  张猛 《岩土力学》2022,43(9):2399-2409

为确定桩间黄土卸荷湿陷过程中卸荷量的合理取值,开展桩−土界面大型剪切试验,研究桩间黄土卸荷湿陷状态下桩−土界面剪切强度、剪切位移及桩−土界面法向力之间的相关关系。结果表明：在桩间土中性点深度范围内,不同竖向应力和含水率状态下的桩−土界面剪切强度可代表桩侧负摩阻力。利用卸荷量与桩侧负摩阻力互为作用力与反作用力的力学原理,并在分析卸荷量随湿陷深度和湿陷进程变化规律的基础上,提出黄土卸荷湿陷过程中卸荷量计算方法,通过对比卸荷量计算值与不同黄土地区桩侧负摩阻力现场实测值,以验证其合理性。该方法不仅为科学评价黄土卸荷湿陷特性提供卸荷作用量化手段,还为相关黄土工程的优化设计提供理论参考依据。  相似文献   

Numerical modeling of secondary migration and its applications to Chang-6 Member of Yanchang Formation (Upper Triassic), Longdong area,Ordos Basin,China     

Luo  XiaoRong  Yu  Jian  Zhang  LiuPing  Yang  Yang  Chen  RuiYin  Chen  ZhanKun  Zhou  Bo 《中国科学:地球科学(英文版)》2007,50(2):91-102

Mathematic modeling, established on the basis of physical experiments, is becoming an increasingly important tool in oil and gas migration studies. This technique is based on the observation that hydrocarbon migration tends to take relative narrow pathways. A mathematical model of hydrocarbon migration and accumulation is constructed using the percolation theory. It is then calibrated using physical experimental results, and is tested under a variety of conditions, to understand the applicability of the model in different migration cases. Through modeling, dynamic conditions of large-scale migration pathways within homogeneous formations can be evaluated. Basin-scale hydrocarbon migration pathways and their characteristics are analyzed during the model application to the Chang-8 Member of the Triassic Yanchang Formation in Longdong area of Ordos Basin. In heterogeneous formations, spatial changes in fluid potential determine the direction of secondary migration, and heterogeneity controls the characteristics and geometry of secondary migration pathways.

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Molecular analysis of the commercial deep-sea crabs Chaceon ramosae and Chaceon notialis (Brachyura,Geryonidae) reveals possible cryptic species in the South Atlantic     

《Deep Sea Research Part I: Oceanographic Research Papers》2014

Deep-sea red crabs Chaceon ramosae and Chaceon notialis are commercially and ecologically important crustaceans in South Atlantic waters. With some overlapping occurring at the edge of the crabs’ distribution, the fisheries are managed separately in Brazil and Uruguay, with some differences in the regulations, although the stock is supposedly shared between the two countries. To assess genetic information on these two species, we examined the nucleotide sequence of the mitochondrial 16S rDNA and CO1 mtDNA genes in samples from the southern region. We also compared these data to sequences from other congeners. The genetic analysis revealed a clear separation between C. notialis and C. ramosae. In addition, we detected the existence of at least two different groups within the species that is currently recognized as C. notialis. This might indicate the existence of cryptic species, leading us to speculate about the presence of two different taxonomic entities, although further research is needed to resolve this issue.  相似文献   

鄂尔多斯盆地东南部石炭系本溪组沉积微相特征及其对天然气富集控制作用     

李云  张建伍  李晶  何剑  孙桂梅  乔玉兰 《西北地质》2014,(2):216-222

综合利用钻井、测井资料,结合邻区露头调查,深入分析鄂尔多斯盆地东南部天然气主要勘探层系石炭系本溪组沉积微相及其砂体分布特征,认为鄂尔多斯盆地东南部本溪组主要发育障壁海岸沉积体系及陆棚沉积体系,并进一步划分出砂坪、混合坪、泥坪、泥灰坪、障壁砂坝、泻湖泥、泥质陆棚7种沉积微相;障壁砂坝及砂坪砂体是天然气储集的骨架砂体,其发育完全受控于沉积相带的展布;本溪组主要产气层"晋祠砂岩"为障壁砂坝及潮汐砂坪成因,障壁主砂坝呈北北东—南南西展布;小砂坝则零星分布,砂坪呈北北西—南南东展布,2类砂体发育区是本溪组天然气勘探有利目标区。  相似文献   

Spatial evaluation of phosphorus retention in riparian zones using remote sensing data     

Guotao Dong  Shengtian Yang  Yunfei Gao  Juan Bai  Xuelei Wang  Donghai Zheng 《Environmental Earth Sciences》2014,72(5):1643-1657

Riparian zones act as important buffer zones for non-point source pollution, thus improving the health of aquatic ecosystems. Previous research has shown that riparian zones play an important role, and that land use has an important effect, on phosphorus (P) retention. A spatial basin-scale approach for analyzing P retention and land use effects could be important in preventing pollution in riparian zones. In this study, a riparian phosphorus cycle model based on EcoHAT was generated with algorithms from soil moisture and heat models, simplified soil and plant phosphorus models, plant growth models, and universal soil loss equations. Based on remote sensing data, model performance was enhanced for spatial and temporal prediction of P retention in the riparian zone. A modified soil and plant P model was used to simulate the soil P cycle of a riparian zone in a temperate continental monsoon climate in northern China. A laboratory experiment and a field experiment were conducted to validate the P cycle model. High coefficients of determination (R ²) between simulated and observed values indicate that the model provides reliable results. P uptake variations were the same as the net primary productivity (NPP) trends, which were affected by soil temperature and moisture in the temperate continental monsoon climate. Beginning in June, the monthly content increased, with the maximum appearing in August, when the most precipitation and the highest temperatures occur. The spatial distribution of P uptake rates from March to September showed that areas near water frequently had relatively high values from May to August, which is contrary to results obtained in March, April, and September. The P uptake amounts for different land uses changed according to expectation. The average monthly P uptake rates for farmlands and grasslands were more than those for orchards and lowlands, which had moderate P uptake rates, followed by shrubs and forests. The spatial distribution of soil erosion demonstrated that the soil erosion came primarily from high-intensity agricultural land in the western and central areas, while the northern and eastern study regions, which were less affected by human activity, experienced relatively slight soil erosion. From the point of view of P pollution prevention, the spatial structure of riparian zones and the spatial distribution of land use around the Guanting reservoir are thus not favorable.  相似文献   

Google Earth Engine平台下秦岭地区植被覆盖时空变化分析     

赵侃  师芸  牛敏杰 《测绘通报》2022,(5):49-55

秦岭地区植被覆盖动态变化对其生态环境有重要影响。本文利用Google Earth Engine云平台,选取1986—2019年Landsat TM/OLI地表反射率数据,结合像元二分模型估算秦岭地区植被覆盖度(FVC);通过年际变化斜率、变异系数、Hurst指数等评价指标,对FVC的时空变化、稳定性和持续性变化进行分析。此外,探究FVC与气温、降雨的耦合关系,并分析土地利用变化对FVC的影响。结果表明:34年间,秦岭地区FVC整体上呈现良好的状况,中高等及以上植被覆盖区达73.11%;FVC由1986年的62.86%增长到2019年的70.01%,植被活动在不断增强;FVC的变异系数均值为0.34,标准差为0.45,其稳定性与其空间分布呈高度自相关性;秦岭地区的植被覆盖变化受气候变化和人为因素的共同影响。  相似文献   

基于改进麻雀搜索算法优化BP神经网络的PM_(2.5)浓度预测北大核心CSCD   总被引：1，自引：0，他引：1  

赵侃  师芸  牛敏杰  王虎勤 《测绘通报》2022,(10):44-48

针对传统BP神经网络模型收敛速度慢、易陷入局部极值等问题,本文采用分段线性混沌映射(PWLCM)和萤火虫算法(FA)改进麻雀搜索算法(SSA),并优化BP神经网络模型初始权值和阈值,对西安市PM_(2.5)浓度进行预测。通过比较不同模型预测结果的评价指标,并与性能较优的SSA-BP模型对比,ISSA-BP模型预测结果的RMSE、MAPE、MAE分别下降了3.70、3.73、3.34。试验结果表明,改进后的麻雀搜索算法具有高效的全局最优搜索能力,优化后的ISSA-BP神经网络预测稳定性高,精度优于BP、SSA-BP神经网络模型,可用于预测PM_(2.5)浓度。  相似文献   

甘肃庆城庄19井区上三叠统延长组长82亚油层组低渗透储层的地质特征     

谢渊  ;谢正温  ;孙虎  ;鲁洪江  ;刘国良 《中国区域地质》2008,(6):844-854

长82亚油层组是甘肃庆城地区庄19井区上三叠统延长组中储集砂岩相对富集的层位,但砂岩低渗透性的特点显著,成为影响该区石油储产量增长的主要地质因素。结合前人的相关工作,通过钻井岩心观察、测井曲线分析、储层岩石实验测试等工作,详细地分析了庄19井区长82亚油层组低渗透储层的地质特征,认为沉积微相和压实作用、胶结作用是控制低渗透性储集砂岩发育和分布的主要地质因素,寻找以水下分流河道微相为代表的有利储集相带砂岩体是油气勘探的重要方向。  相似文献   

圆盘固相萃取富集-气相色谱法测定地表水中有机氯和有机磷农药   总被引：4，自引：2，他引：2       下载免费PDF全文

何淼  饶竹 《岩矿测试》2008,27(1):12-16

采用环境友好的圆盘固相萃取新技术富集水体中有机氯农药和有机磷农药,分别用微池电子捕获检测器(μECD)和火焰光度检测器(FPD)气相色谱法检测,实现了水中有机氯和有机磷农药残留物的测定。结果表明,16种有机氯农药的平均回收率为64.7%~102%,精密度(RSD,n=6)为2.9%~15%;13种有机磷农药的平均回收率为65.9%~104%,精密度(RSD,n=6)为1.7%~17%。方法快速、灵敏、低污染,可用于水体中多种有机氯农药和有机磷农药的残留分析。  相似文献   

甘南牧区劳动力转移背景下留守农户生计策略选择          下载免费PDF全文

苏芳  郑亚萍 《干旱区地理》2018,41(4):826-832

劳动力转移的行为和经历对贫困农（牧）户的生计产生了并继续产生着复杂而深远的影响,并构成了留守家庭成员进行新的生计选择的背景和前提条件。在资本变动和要素约束下,西部民族地区农（牧）户进行着不同的生产决策,并形成不同类型的生计策略。以甘南牧区为例,通过解析劳动力转移的特征变量,总结典型的劳动力转移农（牧）户家庭主要的生计策略模式,揭示了甘南牧区劳动力转移对留守农（牧）户生计策略选择的作用关系,并得出相应的结论。结果表明：转移劳动力文化水平、劳动力转移的外出时间、务工去向与转移劳动力工种类型在一定程度上影响了留守农（牧）户生计策略的选择。这可为西部民族地区政府部门制定科学、合理、可持续的劳动力资源利用政策,促进当地农（牧）户生计的可持续发展提供参考依据。  相似文献