Quantifying the effects of plant litter in the topsoil on the soil detachment process by overland flow in typical grasslands of the Loess Plateau,China

Plant litter can be incorporated into topsoil by a natural process, affecting the soil erosion process. This is a widespread phenomenon in erosion-prone areas. This study was conducted to investigate the effect of litter incorporation on the process of soil detachment on the Loess Plateau, China. Four common plant litters (Bothriochloa ischaemum L. Keng., Artemisia sacrorum Ledeb., Setaria viridis L. Beauv., and Artemisia capillaris Thunb.) were collected, then incorporated into the silt loam soil at five rates (0.1, 0.4, 0.7, 1.0, and 1.3 kg m⁻²) on the basis of our field investigation. Twenty litter–soil treatments and one bare soil control were prepared. After 50 days of natural stabilization, 30 soil samples of each treatment were collected. We used a flume test to scour the soil samples under six flow shear stress conditions (5.66, 8.31, 12.21, 15.55, 19.15, and 22.11 Pa). The results showed that the different incorporated litter masses and morphological characteristics, such as litter tissue density (ranging from 0.52 to 0.68 g cm⁻³), length density (2.34 to 91.00 km m⁻³), surface area density (LSAD; 27.9 to 674.2 m² m⁻³), and volume ratio (0.003 to 0.050 m³ m⁻³), caused varied soil detachment capacities (0.043 to 4.580 kg·m⁻²·s⁻¹), rill erodibilities (0.051 to 0.237 s m⁻¹), and critical shear stresses (2.02 to 6.83 Pa). The plant litter incorporated within the soil reduced the soil detachment capacities by 38%–59%, lowered the rill erodibilities by 32%–46%, and increased the critical shear stresses by 98%–193% compared with the bare soil control. The soil containing B. ischaemum (L.) Keng. litter was more resistant to erosion. By comparing different parameters, we found that the contact area between the litter and soil was the main factor affecting the soil detachment process. The soil erosion resistance increased with the increasing contact area between the soil and litter. Furthermore, the litter incorporation effect on rill erodibility can be comprehensively reflected by LSAD (R² = .93; Nash–Sutcliffe efficiency = 0.79), which could be used to adjust the rill erodibility parameter in physical process-based soil erosion models.     

土层抗浮锚杆承载力关键影响因素现场试验研究

工程实践及理论研究均表明,锚土界面特性和锚杆的几何形状是影响抗浮锚杆承载力的2个关键因素。采用不同的施工工艺进行现场试验施工,得到了具有不同锚土界面特性和锚杆几何形状的抗浮锚杆。通过现场锚杆抗拔试验得到锚杆的应力应变关系及极限抗拔承载力。研究结果表明,改善锚土界面特性和采用变截面的锚固体可显著提高锚杆的抗拔承载力。同时,提出了1种经济高效的抗浮锚杆施工工法。     

黄河下游影响带含水系统激发补给动态调蓄研究

黄河下游悬河的特殊地质环境条件,使黄河水与其影响带地下水水力联系密切,地下水开采潜力大。为优化水资源联合调度,刻画地下水集中供水水源地与含水系统调蓄的内在联系,根据地下含水系统岩性结构及地下水的补、径、排条件,按水源地定流量的开采方案,建立浅层地下水二维水流模型。应用FEFLOW软件,对黄河下游影响带10处地下水水源地进行激发补给动态调蓄模拟预测。结果显示,傍河水源地开采条件下,可以通过增大黄河的侧渗补给量,实现含水系统动态调蓄水资源的功能。     

中国区域科技创新资源分布及其与经济发展水平协同测度

21 世纪是知识经济时代,为了提高中国的科技创新能力以促进经济快速发展,各区域进行了大量科技创新资源的建设投入。但科技投入只有真正转化为创新能力、产出创新成果,才能促进经济的发展。本文分别从国立、地方、企业三方面综合评价了各省的科技创新资源,分析其空间分布格局,并结合经济发展水平,分析了区域科技创新资源与经济发展水平之间的相关性。研究表明,中国各省科技创新资源与经济发展水平总体上呈正相关趋势,但具体到各省份,随着科技创新资源的增加,其经济发展水平却有升有降。为充分发挥区域科技创新资源的作用,提高科研成果产出,区域科技创新资源与经济发展水平的配置关系仍需优化调整。探索中国科技创新资源与经济发展水平间的驱动与响应机制,建立科学合理的决策模型,实现国家用于宏观调控的国立科技创新资源、各地区自主决策的地方科技创新资源、市场驱动的企业科技创新资源三者有机结合、高效配置,以更大程度地实现科技产出,促进经济发展,对于转型期的中国,实现由依靠传统资源要素进入到依靠科技资源支撑和推动社会经济发展的新阶段,具有重要意义。     

Design of transverse reinforcement to avoid premature buckling of main bars

This paper proposes an enhancement to the current strength and confinement‐based design of transverse reinforcement in rectangular and circular reinforced concrete members to ensure that the flexural strength of reinforced concrete sections does not degrade excessively due to buckling of longitudinal bars until the desired level of plastic deformation is achieved. Antibuckling design criteria are developed based on a popular bar buckling model that uses a bar buckling parameter (combining the bar diameter, yield strength, and buckling length) to solely describe the bar buckling behavior. The value of buckling parameter that limits the buckling‐induced stress loss to 15% in compression bars at the strain corresponding to the design ductility is determined. For a bar of known diameter and yield strength, the maximum allowable buckling length can then be determined, which serves as the maximum limit for the tie/stirrup/hoop spacing. Lateral stiffness required to restrain the buckling tendency of main bars at the locations of the ties/stirrups/hoops depends on the flexural rigidity of the main bars and the buckling length (equal to or multiple of tie/hoop/stirrup spacing), whereas the antibuckling stiffness (ie, resistance) provided by the ties/stirrups/hoops depends on their size, number, and arrangement. Using the above concept, design recommendations for the amount, arrangement, and spacing of rectangular and circular ties/stirrups/hoops are then established to ensure that the antibuckling stiffness of the provided transverse reinforcement is greater than the stiffness required to restrain the buckling‐prone main bars. Key aspects of the developed method are verified using experimental tests from literature.     

区域土地资源人口承载力理论模型及实证研究

在传统食物型人口承载力基础上,引进表征土地资源经济产出的货币型人口承载力来综合考虑土地资源人口综合承载力,建立了区域土地资源人口承载力模型。并以呼和浩特市域作为研究区域,运用系统动力学(SD)原理与方法,在不同情景下模拟了土地资源人口承载力,得出较优的发展方案,即到2020年呼和浩特市域食物型人口承载力为310万人,货币型人口承载力为1 723万人,综合人口承载力为1 000万人口,货币型人口承载力多出食物型人口承载力5.56倍,货币型人口承载力对综合人口承载力的贡献远超过了食物型人口承载力的贡献。     

中低温开放含硫水热体系中水岩淋滤实验研究

针对湘中湘西矿区的地质实际在１００￣３００℃,２０ＭＰａ压力条件下,对中低温开放含硫水热体系地层岩石中Ｓｂ、Ａｓ、Ｈｇ的多元素进行了淋滤实验研究。实验结果表明,随温度的升高,Ｓｂ和Ｈｇ的淋滤率增大;低温富硫热液有利于Ｓｂ和Ａｓ的活化迁移。同时,水岩比值、岩性以及岩石中元素的存在形式也是控制元素活化能力的重要因素。     

Comparative Study of Gacun and Youre Silver–Lead–Zinc–Copper Deposits in Sichuan, SW China, and their Mineralization Significance

The large Gacun silver–lead–zinc–copper deposit in Sichuan Province is one of the largest volcanogenic massive sulfide(VMS) deposits in China. The deposit consists of western and central ore bodies, which form a vein–stockwork mineralization system corresponding to hydrothermal channels, and eastern ore bodies, which form an exhalative chemical sedimentary system derived from a brine pool in a submarine basin. The Youre lead–zinc deposit, which is currently under exploration and lies adjacent to the southern part of the Gacun deposit, is characterized by intense silicification and vein–stockwork structures and consists of massive silicified rhyolitic volcanics, banded rhyolitic tuff, and phyllitic sericite tuff. From a comparison of their ore-bearing horizons, the Gacun and Youre deposits have a continuous and stable hanging wall(calcareous slate and overlying andesite) and foot wall(rhyolite–dacite breccia and agglomerate), and the lithologic sequence includes lower intermediate to felsic rocks and upper felsic rocks. Thus, the Youre deposit, which comprises relatively thinly layered low–grade ore, is regarded as forming a southward extension of the Gacun deposit. A further comparison of the structures of the ore-bearing belts between the two deposits suggests that the Youre ore bodies are similar to the western ore bodies of the Gacun deposit. Moreover, the characteristics of fluid inclusions and stable isotopes in the Youre deposit are also similar to those of the western ore bodies of the Gacun deposit. Genetic models of the deposits are proposed for the Gacun–Youre ore district, and massive concealed ore bodies may occcur in the Youre deposit at depths that are similar to those of the eastern ore bodies of the Gacun deposit.