Heavy meals in urban roadside soils, part 1: effect of particle size fractions on heavy metals partitioning   总被引：8，自引：0，他引：8  

Xue-Song Wang  Yong Qin  Yong-Kang Chen 《Environmental Geology》2006,50(7):1061-1066

Urban roadside soils are important environmental media for assessing heavy metal concentrations in urban environment. However, among other things, heavy metal concentrations are controlled by soil particle grain size fractions. In this study, two roadside sites were chosen within the city of Xuzhou (China) to reflect differences in land use. Bulk soil samples were collected and then divided by particle diameter into five physical size fractions, 500–250, 250–125, 125–74, 74–45, < 45 μm. Concentrations of metals (Ti, Cr, Al, Ga, Pb, Ba, Cd, Co, Cu, Mn, Ni, V, Zn, Mo, As, Sb, Se, Hg, Bi, Ag) were determined for each individual fraction. These metals could be roughly classified into two groups: anthropogenic element (Pb, Ba, Cd, Cu, Zn, Mo, As, Sb, Se, Hg, Bi, Ag) and lithophile element (Ti, Cr, Al, Ga, Co, Mn, Ni, V) in terms of values of enrichment factor. As expected, higher concentrations of anthropogenic heavy metals (Cu, Zn, Mo, As, Hg, Bi, Ag) are observed in the finest particle grain size fraction (i.e. < 45 μm). However, heavy metals Se, Sb and Ba behave independently of selected grain size fractions. From the viewpoint of mass loading, more than 30% of the concentrations for all anthropogenic heavy metals are contributed by the particle grain size fractions of 45–74 μm at site 1 and more than 70% of the concentrations for all heavy metals are contributed by the particle grain size fractions of 45–74 and 74–125 μm at site 2. These results are important for transport of soil-bound heavy metals and pollution control by various remedial options.  相似文献   

Undrained cyclic behavior of bentonite–sand mixtures and factors affecting it     

Ivan Borisovich Gratchev  Kyoji Sassa  Viktor Ivanovich Osipov  Hiroshi Fukuoka  Gonghui Wang 《Geotechnical and Geological Engineering》2007,25(3):349-367

In this work, the cyclic behavior of bentonite–sand mixtures and factors affecting it were studied by means of a ring-shear apparatus and a scanning electron microscope. It was found that bentonite content had a significant influence on the liquefaction potential of the studied soils. A small amount of bentonite in the mixtures would cause the formation of “loose” microstructures, resulting in the occurrence of rapid liquefaction under cyclic loading, while a high bentonite content would cause the formation of clay matrixes, thus raising the soil resistance to liquefaction. In addition, the effect of pore water chemistry on the cyclic behavior of a high plasticity bentonite–sand mixture was carefully examined. It was also found that the presence of ions in pore water would change the clay microfabric, making it more open and thus more vulnerable to liquefaction. Finally, the effects of loading frequency on the cyclic behavior of mixtures with different amounts of bentonite were investigated. It was found that as the bentonite content increased, the influence became more pronounced.  相似文献   

Pullout capacity of embedded suction anchors in sand     

K.D. Jones  Y. Cho 《Ocean Engineering》2007,34(16):2107-2114

An analytical solution has been developed to estimate the horizontal, vertical, and inclined loading pullout capacities of embedded suction anchors in sand. Validation of the analytical solution on pullout capacities has been made through comparisons with the centrifuge model test results. Primary variables for the centrifuge model tests are the depth to the loading point, the load inclination angle, and the addition of flanges. The results indicate that both the horizontal and vertical pullout capacities of the embedded suction anchor in sand increase, reach the peak and then start to decrease as the loading point moves downward. The inclined loading pullout capacity is very much dependent on the load inclination angle and the loading point. The effect of flanges on the pullout capacities is also found to be significant.  相似文献   

变形模量测试结果差异的分析          下载免费PDF全文

徐兵 《江苏地质》2008,32(2):141-143

地基土的变形模量是衡量地基土工程力学特性的一个重要指标,结合工程实例介绍了应用不同面积的承压板对同一点的地基土进行浅层平板载荷试验时,运用其测试结果计算得到地基土的变形模量并不一致,一般承压板的面积越大,变形模量值越小。分析了其中的原因,并提出了相应的解决办法。  相似文献   

循环荷载下土石混合体力学特性野外试验研究   总被引：7，自引：0，他引：7  

徐文杰  胡瑞林 《工程地质学报》2008,16(1):63-69

土石混合体是一种物理、力学性质非常复杂的不连续介质。以云南某高速公路土石混合体边坡为例,分别对选取的3个试验点进行了单调加载、循环加载一次及多次循环加载试验,获取了其相应的剪切位移-剪切应力关系曲线,并对其曲线特征进行分析研究。通过对试样三维滑动面的形态分析,指出由于土石混合体三维滑动面的不规则性,利用传统的二维计算方法难以得到较为准确的强度参数。基于三维极限平衡理论,提出了土石混合体水平推剪试样强度参数的三维数据计算方法。并利用该方法得到了研究区土石混合体的相应的强度参数及残余强度参数。  相似文献   

横向非均匀地球负荷问题的CLFE有限元算法的有效性   总被引：3，自引：2，他引：1       下载免费PDF全文

汪汉胜  Wu Patrick  Hugo Schotman  王志勇 《地球物理学报》2006,49(6):1657-1664

本文设计了三个数值算例分别模拟径向分层黏弹地球对二阶球谐负荷、均厚圆盘负荷和全球末次冰期真实冰负荷的响应.利用耦合位扰动Laplace方程的三维有限元法(CLFE),计算出地球表面的位移、大地水准面的变化、冰后海平面变化和这些量的现今变化速率,并将其结果与传统谱方法的结果进行对比.结果表明,两种方法的结果总体上表现出良好的一致性,因此,CLFE方法被证实是正确的、有效的、能被用于研究地幔横向非均匀性的影响.值得注意的是,新的方法完全没有横向非均匀小扰动假设的限制.  相似文献   

加卸载响应比在Poisson模型下的随机分布   总被引：9，自引：2，他引：7  

庄建仓  尹祥础 《中国地震》1999,15(2):128-138

本文在地震的发生时间服从Ｐｏｉｓｓｏｎ过程,而地震震级服从Ｇｕｔｅｎｂｅｒｇ－Ｒｉｃｈｔｅｒ关系的前提下,对不同定义的加卸载响应比Ｙ值的随机分布进行了探讨。结果表明：当在计算窗口的地震发生的期望数目较大（〉４０）时,Ｙ１￣Ｙ５值的分布基本稳定,出现高加卸载响应比的概率极低。然而当计算窗口的地震期望数目过小时,Ｙ２￣Ｙ５值则变得不太稳定。也就是说,服从Ｐｏｉｓｓｏｎ过程的地震序列,在计算窗口的地震期  相似文献   

加卸载响应比在震群研究中的应用   总被引：2，自引：0，他引：2  

王海涛  彭克银 《内陆地震》1999,13(2):112-119

在震群特性研究中引入加卸载响应比理论,选以新疆８２个震群为研究样本,以加卸载响应比≥２．０作为判定前兆震群的指标,对样本的震群特性进行了分析判定。结果表明,判定前兆震群的２６个震群中有２０个对应了其后一年内发生的５级以上地震,异常报率为７６．９％。  相似文献   

唐山两次中级地震前后地下水位固体潮加卸载响应比的变化     

张昭栋  刘章增 《东北地震研究》1999,15(2):6-16

本文将加卸载响应比的理论和方法引入到地下水位潮汐资料计算中来,从岩石的应变与应力的非线性响应分析了井水位固体潮加卸载响应比的物理。  相似文献   

Determination of Ocean Tide Loading Displacement by GPS PPP with Priori Information Constraint of NAO99b Global Ocean Tide Model     

Hong Zhao  Zhi Liu 《Marine Geodesy》2018,41(2):159-176

The published global ocean tide models show good agreement in deep oceans and exhibit differences in complex coastal areas, along with subsequent Ocean Tide Loading Displacement (OTLD) modeling differences. Meanwhile, OTLD parameters (amplitudes and phase lags) derived by Global Positioning System (GPS) Precise Point Positioning (PPP) approach need long time to converge to a stable state and show poor precision of S2, K1, and K2 constituents. Based on the fact that no constraint is imposed in the current kinematic solution, a new method is put forward, in which global ocean tide model predictions are taken as the priori information constraints to speed up the convergence rate and improve the accuracy of the GPS-derived OTLD parameters. First, the data of tide gauge from 01 January 2014 to 31 December 2016 are used to generate the harmonic parameters to evaluate the accuracy of six global ocean tide models and a regional ocean tide model (osu.chinesea.2010). Osu.chinesea.2010 model shows good agreement with the tide gauge results, while NAO99b model presents relatively large difference. The predictions from osu.chinesea.2010 and NAO99b model are employed as reference and the prior information, respectively. Second, continuous observations of 12 GPS sites during 2006–2013 in Hong Kong are collected to generate three dimensional OTLD amplitudes and phase lags of eight constituents using PPP with prior information constraints approach and harmonic analysis. Third, comparing the convergence time of eight constituents from PPP without and with priori information constraints approaches, the results show that the new method can significantly improve the convergence rate of OTLD amplitude estimates which obtain a certain level of stability seven years earlier than that derived by the PPP without priori information constraints. Precision of OTLD parameters derived by the new method is about 1 mm. By comparing with the precision of single PPP approach, the accuracy of eight constituents has been improved, especially for S2, K1, and K2 constituents. Finally, through comparing the different correction effects of OTLD estimates on the coordinates and their time series of the ground GPS stations, the results show that OTLD estimates derived by the new approach have similar influence as the osu.chinasea.2010 ocean tide model. The new method provides an effective means to improve the convergence and precision of the GPS-derived OTLD parameters, and achieve a similar correction as the high precision ocean tide model.  相似文献