A high strain‐rate constitutive model for sand and its application in finite‐element analysis of tunnels subjected to blast     

William Higgins  Tanusree Chakraborty  Dipanjan Basu 《国际地质力学数值与分析法杂志》2013,37(15):2590-2610

The paper presents a constitutive model for simulating the high strain‐rate behavior of sands. Based on the concepts of critical‐state soil mechanics, the bounding surface plasticity theory and the overstress theory of viscoplasticity, the constitutive model simulates the high strain‐rate behavior of sands under uniaxial, triaxial and multi‐axial loading conditions. The model parameters are determined for Ottawa and Fontainebleau sands, and the performance of the model under extreme transient loading conditions is demonstrated through simulations of split Hopkinson pressure bar tests up to a strain rate of 2000/s. The constitutive model is implemented in a finite‐element analysis software Abaqus to analyze underground tunnels in sandy soil subjected to internal blast loads. Parametric studies are conducted to examine the effect of relative density and type of sand and of the depth of tunnel on the variation of stresses and deformations in the soil adjacent to the tunnels. Copyright © 2012 John Wiley & Sons, Ltd.  相似文献   

RECENT SEDIMENTATION AND SUSPENDED MATTER IN ERHAI LAKE,YUNNAN PROVINCE,CHINA   总被引：1，自引：0，他引：1  

孙顺才  张琛  宋学良 《中国海洋湖沼学报》1999,17(2):170-180

INTR0DUCnONErhailake,thesecondlargestlakeintheYUnnanPlateauinS0uthWstChina,islo-catedinDaliDefecthe25035'to25"58'N,looo05't0l(X)o07'E(Fig.l)-The40kInlong3-9kInwidelakeisnaInedafteritsearlikeshape.ItsbasicchimteristicsaregiveninTablel.EtheibeeisampicalriftlakeintheDalibasinwhichdeveloPedalongtheYuaniangHongheThewestsideofthebasinisformedbytheDiancangMountainwhichconsists0frock(PrecaInbrianschistandgneissandMiocenemetaInrphiclimestone).TheseisndcallystillactivemoUntainrangrisab0ut…  相似文献   

The response of CO2 flux to rain pulses at a saline desert     

Jie Ma  Xin‐Jun Zheng  Yan Li 《水文研究》2012,26(26):4029-4037

As the substantial component of the ecosystem respiration, soil CO₂ flux is strongly influenced by infrequent and unpredictable precipitation in arid region. In the current study, we investigated the response of soil CO₂ flux to rain pulses at a saline desert in western China. Soil CO₂ flux was measured continuously during the whole growing season of 2009 at six sites. We found that there were remarkable changes in amplitude or diurnal patterns of soil CO₂ flux induced by rainfall events: from bimodal before rain to a single peak after that. Further analysis indicated that there is a significant linear relationship (P < 0.001) between soil CO₂ flux and soil temperature (T_soil). However, a hysteresis between the waveform of diurnal course of CO₂ flux and T_soil was observed: with soil CO₂ flux always peaked earlier than T_soil. Furthermore, a double exponential decay function was fitted to the soil CO₂ flux after rainfall, and total carbon (C) releases were estimated by numerical integration for rainfall events. The relative enhancement and total C release, in association with the rain pulses, was linearly related to the amount of precipitation. According to the size and frequency of rainfall events, the total amount of C release induced by rain pulses was computed as much as 7.88 g C·m^–2 in 2009, equivalent to 10.25% of gross primary production. These results indicated that rain pulses played a significant role in the carbon budget of this saline desert ecosystem, and the size of them was a good indicator of rain‐induced flux enhancement. Copyright © 2012 John Wiley & Sons, Ltd.  相似文献   

Effect of nitrogen and phosphorus on the growth of a red tide dinoflagellateScrippsiella trochoidea (Stein) Loeblich III     

Qin Xiao-ming  Qian Pei-yuan  Zou Jing-zhong 《中国海洋湖沼学报》1999,17(3):212-218

Scrippsiella trochoidea (Stein) Loeblich III was grown in a nitrogen-or phosphorus-limited batch culture system in laboratory. Growth rates and cellular Chl-a were measured as functions of nitrate and phosphate concentrations. Growth rates were hyperbolic with both nitrate and phosphate concentration and fit the Monod equation. The minimum cell quota of nitrogen and phosphorus and then the optimum N∶P ratio ofS. trochoidea were estimated in this study. Measurement of phosphate concentration in Jiaozhou Bay suggest that phosphorus is the limiting factor ofS. trochoidea growth. Contribution No. 3679 from the Institute of Oceanology, Chinese Academy of Sciences. Project 39790110 supported by NSFC, the study aslo supported by the National Climbing Project B (PDBG-7-2) and partly supported by an MF grant from Hong Kong University of Science and Technology.  相似文献   

A 10Be production‐rate calibration for the Arctic     

NICOLÁs E. YOUNG  JOERG M. SCHAEFER  JASON P. BRINER  BRENT M. GOEHRING 《第四纪科学杂志》2013,28(5):515-526

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近42年雅鲁藏布江中游四季气温变化特征分析   总被引：2，自引：0，他引：2  

周顺武  张勇 《成都信息工程学院学报》2000,15(4):307-311

利用 1957～ 1998年雅鲁藏布江中游拉萨、日喀则、泽当、江孜 4个站各月平均气温资料 ,通过线性趋势估计和多项式函数拟合分析了该流域春、夏、秋、冬 4季气温长期趋势变化和周期变化 ,并利用滑动T检验等方法讨论了气温突变的问题。结果表明 :在过去 4 2年里 ,雅鲁藏布江中游地区各季气温均有明显的上升趋势 ,其中冬春季增温显著 ,80年代初沿江四季气温除秋季外都出现了明显的增温突变  相似文献   

河西地区重力动态变化的二维离散小波多尺度分解   总被引：7，自引：5，他引：2  

朱桂芝  祝意青  唐文  程宏宾 《大地测量与地球动力学》2004,24(1):46-49

采用二维离散小波的多尺度分解技术，对1994～1995年和2002～2003年的河西地区重力动态变化进行分解，提取该地区不同层次的重力动态变化异常，结果反映了不同深度在一定尺度意义上的介质密度的动态变化分布。  相似文献   

沙质海岸强浪作用下沿岸输沙问题研究   总被引：1，自引：0，他引：1  

王玉海 《海洋工程》2008,26(4)

在沙质海岸上修建导流堤、丁坝等会引起局部海域水沙动力条件的改变和海床冲淤调整,因此准确预测沿岸输沙率是海岸工程建设前进行优化设计的基础条件之一.首先构建了刻画高强度推移质输沙过程中固-液混合体运动的理论模型,通过寻求模型的特解并推导成1D沿岸输沙率公式.该公式适宜计算强浪作用下的推移质输沙率,已得到了大型波浪水槽、往复流水道和海滩现场实测输沙率资料的良好验证.通过与物理模型试验实测输沙量结果的比较,进一步表明该公式能够较好地预测沙质海岸在寒潮大风浪(或台风浪)作用下的高强度输沙量(骤淤量).  相似文献   

The disappearance of eclipses in the central star of the planetary nebula NGC 2346     

Hao Xiang-liang 《Chinese Astronomy and Astrophysics》1991,15(4):431-438

This paper gives the result of photographic photography of the central star AGK3-0° 695 of the planetary nebula NGC 2346 made from 1981 through 1987. From it we see that after the large-amplitude eclipses which had started at the end of 1981 had continued for several years, the amplitude began to decrease rapidly in 1986 to ˜1.1 mag from ˜4 mag in 1984. In 1987, only irregular fluctuations with amplitudes ˜0.4 mag were present in the light curve and not longer any clear periodicity. A preliminary analysis of this phenomenon is carried out here.  相似文献   

桂林洞穴滴水对应CaCO3沉积物的稳定同位素特征与环境意义   总被引：2，自引：0，他引：2  

韩军  杨霄 《海洋地质与第四纪地质》2008,28(4)

桂林地区降水及茅茅头大岩滴水滴速和现代碳酸盐的碳氧同位素研究表明:(1)滴水沉积的δ18O达到了同位素沉积平衡,洞穴滴水的δ18O与同期降雨的δ18O值呈正相关关系;(2)在旱季和湿季交替时,滴水δ18O值滞后于降雨δ18O,受活塞效应的影响;(3)δ13C难以达到同位素沉积平衡,主要受滴水动力学影响;(4)同一洞穴不同滴水对环境的响应不同,如果洞穴顶板覆盖较厚,水分在土壤和岩层中滞留时间较长,滴水则反映受到平滑作用的降雨,反之则波动较大.  相似文献