天津海域春夏季节游泳动物的组成特征

根据2014年5月及8月在天津海域进行的底拖网调查资料,对该海域游泳动物组成特征进行了初步研究。结果表明,在该海域共捕获游泳动物36种,平均资源密度为126 297.13个/km~2和1 494.40 kg/km~2。以个体密度计算群落多样性,Shannon-Wiener种类多样性指数H′平均为1.803,Margalef种类丰富度指数d平均为0.592,Pielou种类均匀度指数J平均为0.537。资源密度及物种多样性,8月均优于5月。优势种为口虾蛄,重要种为火枪乌贼、日本、斑、六丝钝尾虾虎鱼。天津近岸海域游泳动物渔业资源呈现出低质化的趋势。     

The prediction of traveling jet trenching in stiff clay based on the erosion failure mechanism

The performance of traveling jet trenching in stiff clay was tested. All the key parameters varied in the experiment, including the jet velocity, the shear strength of clay, the diameter of the nozzle, and the translational velocity of the nozzle. The jet–soil interface was found to be an arc. An equation was given to describe the interface. On the basis of the erosion failure mechanism, a new method is presented for predicting jet trenching depth. We first calculated the trajectory of the jet–soil interface and then predicted the distribution of the boundary layer shear stress along the jet–soil interface. The point where the wall shear stress was equal to the critical shear strength of clay was the ultimate trenching depth. The predictive results were found to fit the experimental results well.     

Characteristics and cause analysis of heavy haze in Changchun City in Northeast China

Northeast China has been reported as having serious air pollution in China with increasing occurrences of severe haze episodes. Changchun City, as the center of Northeast China, has longstanding industry and is an important agricultural base. Additionally, Changchun City has a long winter requiring heating of buildings emitting pollution into the air. These factors contribute to the complexity of haze pollution in this area. In order to analyze the causes of heavy haze, surface air quality has been monitored from 2013 to 2015. By using satellite and meteorological data, atmospheric pollution status, spatio-temporal variations and formation have been analyzed. Results indicated that the air quality in 88.9% of days exceeding air quality index(AQI) level-1 standard(AQI 50) according to the National Ambient Air Quality Standard(NAAQS) of China. Conversely, 33.7% of the days showed a higher level with AQI 100. Extreme haze events(AQI 300) occurred frequently during agricultural harvesting period(from October 10 to November 10), intensive winter heating period(from Late-December to February) and period of spring windblown dust(April and May). Most daily concentrations of gaseous pollutants, i.e., NO_2(43.8 μg/m~3), CO(0.9 mg/m~3), SO_2(37.9 μg/m~3), and O_3(74.9 μg/m~3) were evaluated within level-1 concentration limits of NAAQS standards. However, particulate matter(PM_(2.5) and PM10) concentrations(67.3 μg/m~3 and 115.2 μg/m~3, respectively) were significantly higher than their level-1 limits. Severe haze in spring was caused by offsite transported dust and windblown surface soil. Heavy haze periods during fall and winter were mainly formed by intensive emissions of atmospheric pollutants and steady weather conditions(i.e., low wind speed and inversion layer). The overlay emissions of widespread straw burning and coal combustion for heating were the dominant factors contributing to haze in autumn, while intensive coal burning during the coldest time was the primary component of total emissions. In addition, general emissions including automobile exhaust, road and construction dust, residential and industrial activities, have significantly increased in recent years, making heavy haze a more frequent occurrence. Therefore, both improved technological strategies and optimized pollution management on a regional scale are necessary to minimize emissions in specified seasons in Changchun City, as well as comprehensive control measures in Northeast China.     

New-type urbanization in China: Predicted trends and investment demand for 2015–2030

The future development of new-type urbanization has drawn great attention from both the government and public alike. In this context, the present study had three related research aims. Firstly, it sought to predict the urbanization and population dynamics in China at both national and provincial levels for the period of 2015 to 2030. Secondly, on this basis, it sought to examine the spatial variation of urbanization given the predicted national urbanization rate of 70.12%. Thirdly, it sought to estimate and evaluate the national and provincial demands of investment in the development of new-type urbanization. The main conclusions from this study were as follows: (1) The population size and urbanization rate will reach 1.445 billion and 70.12%, respectively, from 2015 to 2030. (2) The demographic dividend will vanish when the population pressure reaches its maximum. During this period, there will be 70.16 million urban population born. The suburban population that becomes urbanized will be 316.7 million, and thus the net increase in urban population will reach 386 million. (3) Although the urbanization rate of every Chinese province will increase during 2015–2030, it will do so unequally, while differences in urbanization quality among provinces will also be substantial. In some provinces, moreover, the urbanization quality is not compatible with their eco-social development. (4) A total of 4,105,380 billion yuan is required to fund new-type urbanization and the investment demand for each province varies greatly; for example, Guangdong province requires the most funding, amounting to approximately 148 times that required by Tibet, the province in least need of funding. In the final part of this study, policy suggestions concerning the investment of the new-type urbanization are put forward and discussed.     

Method for assessing coal-floor water-inrush risk based on the variable-weight model and unascertained measure theory

Water inrush from coal-seam floors greatly threatens mining safety in North China and is a complex process controlled by multiple factors. This study presents a mathematical assessment system for coal-floor water-inrush risk based on the variable-weight model (VWM) and unascertained measure theory (UMT). In contrast to the traditional constant-weight model (CWM), which assigns a fixed weight to each factor, the VWM varies with the factor-state value. The UMT employs the confidence principle, which is more effective in ordered partition problems than the maximum membership principle adopted in the former mathematical theory. The method is applied to the Datang Tashan Coal Mine in North China. First, eight main controlling factors are selected to construct the comprehensive evaluation index system. Subsequently, an incentive-penalty variable-weight model is built to calculate the variable weights of each factor. Then, the VWM-UMT model is established using the quantitative risk-grade divide of each factor according to the UMT. On this basis, the risk of coal-floor water inrush in Tashan Mine No. 8 is divided into five grades. For comparison, the CWM is also adopted for the risk assessment, and a differences distribution map is obtained between the two methods. Finally, the verification of water-inrush points indicates that the VWM-UMT model is powerful and more feasible and reasonable. The model has great potential and practical significance in future engineering applications.     

Provenance and paleogeography of the Mesozoic strata in the Muang Xai Basin,northern Laos: petrology,whole-rock geochemistry,and U–Pb geochronology constraints

International Journal of Earth Sciences - The Muang Xai Basin, located in northern Laos, is associated with the Simao, Vientiane, and Khorat Basins. The paleogeographic link of these basins has not...     

鄂尔多斯盆地姬塬西部三叠系延长组长8油层组成岩作用与致密化过程*

利用岩心、铸体薄片、扫描电镜、碳氧同位素及流体包裹体等资料,对鄂尔多斯盆地姬塬西部三叠系延长组长8油层组致密储集层特征进行了研究,重点分析了储集层成岩作用特征和储集层致密化成因机制及过程。研究区长8油层组砂岩主要为岩屑长石砂岩和长石岩屑砂岩,经历了压实—压溶、胶结、交代、溶蚀及构造破裂等成岩作用,整体处于中成岩A期晚期。典型成岩序列依次为机械压实、绿泥石黏土膜、早期(泥晶)方解石胶结、石英次生加大、长石、岩屑溶蚀、自生高岭石胶结、自生石英胶结、中期(含)铁方解石胶结。综合研究认为:(1)近物源伴随湖平面快速上升的沉积环境提供了储集层致密化的物质基础,不同沉积微相储集层物性差别较大,分流河道最好,分流间湾最差;(2)长8油层组原始孔隙度为41.35%,压实作用损孔率为50.67%,造成储集层孔隙度急剧降低,胶结作用损孔率为37.48%,导致孔隙度进一步减小,溶蚀作用仅增加了3.26%的孔隙度,难以有效改善储集层质量;(3)上述沉积与成岩因素共同导致储集层致密,致密化过程可分为压实孔隙骤减阶段、早期胶结减孔阶段、溶蚀作用增孔阶段和晚期胶结致密阶段共4个阶段;(4)油气大量充注期储集层孔隙度远低于10%,长8油层组先致密后成藏。     

中亚造山带东部岩浆热液矿床时空分布特征及其构造背景

中亚造山带东部是古亚洲洋构造域、鄂霍茨克洋构造域和古太平洋构造域复合叠加区域,矿产资源丰富。本文收集2000—2014年公开发表文献中岩浆热液矿床约1 200个同位素年龄数据,整理出201个较为可靠的年龄数据,通过数字化编图,揭示成矿的时空分布特征及形成背景。结果显示:中亚造山带东部成矿作用始于寒武纪,出现6个重要成矿期:510~473、373~330、320~253、250~210、210~167、155~100 Ma。510~473 Ma(峰值507 Ma),矿床主要分布在大兴安岭—小兴安岭—张广才岭和北山地区,零星发育热液脉型和斑岩型铁铜金钨矿床,与古亚洲洋开始俯冲及微陆块碰撞拼合有关。373~330 Ma(峰值372Ma),矿床主要分布在南蒙古奥尤陶勒盖地区,发育超大型斑岩型铜金矿床,形成于古亚洲洋俯冲环境。320~253 Ma,矿床主要分布在大兴安岭南段,发育少量斑岩型铜矿床和造山型金矿床;其中,298 Ma在大兴安岭南段首次出现以钼为主的斑岩型矿床,指示该区板块俯冲增生向拼贴转变逐渐过渡。250~210 Ma(峰值244 Ma),在蒙古—鄂霍茨克造山带东侧额尔古纳—中蒙古地块主要形成斑岩型铜矿床,可能与蒙古—鄂霍茨克洋俯冲有关;以东地区,主要在大兴安岭南段和辽远地块形成斑岩型钼矿床,在张广才岭发育岩浆熔离型铜镍矿床,反映了古亚洲洋闭合后伸展环境。210~167 Ma(峰值170 Ma),在蒙古—鄂霍茨克造山带西侧乌兰巴托西北部发育造山型-斑岩型金矿床,其东侧额尔古纳地区形成斑岩型铜钼矿床,可能与蒙古—鄂霍茨克洋俯冲碰撞有关;在吉黑东部—张广才岭—小兴安岭—大兴安岭,发育斑岩型钼铜矿床和矽卡岩型铅锌钨金矿床组合,可能属于古太平洋板块向西俯冲成矿体系。155~100 Ma(峰值136 Ma),中亚造山带东部整体处于伸展环境;其中,155~120 Ma在额尔古纳地区主要发育浅成低温热液型银铅锌矿床和造山型金矿床,大兴安岭北段发育斑岩型钼矿床,可能反映了额尔古纳地区和大兴安岭北段受蒙古—鄂霍茨克洋碰撞后伸展环境控制,而在吉黑东部形成浅成低温热液型金矿床,大兴安岭南段发育热液脉型-矽卡岩型锡矿床,可能受古太平洋板块向北俯冲弧后伸展的控制;120~100 Ma沿着华北克拉通和佳蒙陆块边缘发育浅成低温热液型-斑岩型金钼矿床。本研究综合岩浆热液矿床时空分布和矿床类型,进一步揭示了古亚洲洋构造域控制中亚造山带东部古生代成矿作用持续到晚二叠世(到早三叠世),并在晚三叠世叠加古太平洋构造域成矿体系,而额尔古纳—中蒙古地块成矿作用在三叠纪开始主要受蒙古—鄂霍茨克洋构造域限定,并持续到早白垩世早期。     

Estimation of critical state-related formula in advanced constitutive modeling of granular material

Different critical state-related formulas, for the critical state line and the critical state-dependent interlocking effect, have been proposed in constitutive modeling of granular material during last decades, which rises up a confusion on how to select an appropriate model in the geotechnical applications. This paper aims to discuss the selection of these critical state-related formulas and parameters identification. Three formulas of critical state line together with two formulas of critical state-dependent interlocking effect are combined to propose six elasto-plastic models. Drained and undrained triaxial tests on four different granular materials are selected for simulations. In order to eliminate artificial errors, a new hybrid genetic algorithm-based intelligent method is proposed and used to identify parameters and estimate simulations with minimum errors for each granular material and each model. Then, the performance of each CSL and each state parameter is evaluated using two information criteria. Furthermore, the performance was evaluated by simulating three footing tests using finite-element analysis in which the models are implemented. All comparisons demonstrate the incorporation of nonlinear critical state line combined with the state parameter e/e _c in constitutive modeling can result in relatively more satisfied simulated results.     

An efficient optimization method for identifying parameters of soft structured clay by an enhanced genetic algorithm and elastic–viscoplastic model

Soft structured clays usually exhibit complex behaviors, which can lead to difficulties in the determination of parameters and high testing costs. This paper aims to propose an efficient optimization method for identifying the parameters of advanced constitutive model for soft structured clays from only limited conventional triaxial tests. First, a new real-coded genetic algorithm (RCGA) is proposed by combining two new crossover and mutation operators for improving the performance of optimization. A newly developed elastic–viscoplastic model accounting for anisotropy, destructuration and creep features is enhanced with the cross-anisotropy of elasticity and is adopted for test simulations during optimization. Laboratory tests on soft Wenzhou marine clay are selected, with three of them being used as objectives for optimization and others for validation. The optimization process, using the new RCGA with a uniform sampling initialization method, is carried out to obtain the soil parameters. A classic genetic algorithm (NSGA-II)-based optimization is also conducted and compared to the RCGA for estimating the performance of the new RCGA. Finally, the optimal parameters are validated by comparing with other measurements and test simulations on the same clay. All comparisons demonstrate that a reliable solution can be obtained by the new RCGA optimization combined with the appropriate soil model, which is practically useful with a reduction in testing costs.