Comparison of magnetic parameters with vehicular Br levels in urban roadside soils

Chemical methods are generally chosen to monitor soil pollution but magnetic measurements proved to yield additional information at low cost and less time consumption. In this investigation, the novel use of rapid and non-destructive magnetic measurements to characterize Br levels in Xuzhou (China) urban roadside soils was reported. X-ray fluorescence spectrometry (XRF) was used to quantify Br in the soil samples. Data from 21 roadside soil samples confirm Br contamination, with a mean level of 4.36 mg kg⁻¹ and a range of 2.4–8.7 mg kg⁻¹. These values are higher than that of unpolluted soils in Xuzhou that averages 1.1 mg kg⁻¹. Hierarchical clustering analysis shows Br in Xuzhou roadside soils is mainly from road traffic. Clear correlations between Br levels and simple magnetic parameters [mass specific susceptibility (χ _LF), susceptibility of anhysteretic remanent magnetization (χ _ARM), saturation isothermal remanence (SIRM)] are observed. The present study shows that these three magnetic parameters can be used as a proxy for Br levels in Xuzhou urban roadside soils.     

Free-Swell and Swelling Pressure of Unsaturated Compacted Clays; Experiments and Neural Networks Modeling

Expansive soils have received attentions of several investigators in the past half of century in the problematic soils context. Volume change behavior of unsaturated compacted soils in presence of water and change of degree of saturation was observed in two form of heave or collapse. Low water content and low density compacted soils in presence of enough surcharge pressure lose stability and collapse, because of their metastable and susceptible structure to change of degree of saturation. Free-swell and swelling pressure of five compacted clays, covering low to high plastic clays have been investigated in respect to compaction states and swelling pressure was compared with collapse pressure threshold. The results of experiments were utilized in two Artificial Neural Networks to predict free-swell percent and swelling pressure of a soil sample based on index properties and compaction state.     

基质吸力变化引起的体积应变研究

与降雨有关的边坡表层变形位移,其根源是基质吸力降低引起的非饱和土体积应变。利用某滑坡体的原状样及其重塑样,分别在100kPa、200kPa围压作用下,采用单纯增加基质吸力的应力路径,对基质吸力引起的体积应变,进行试验测试。结果显示: (1)试样的体应变,随基质吸力的增大,单调增大,服从对数函数关系;(2)围压由100kPa增加到200kPa的试样体积模量,随基质吸力的增大,单调增大,服从幂函数关系;(3)与基质吸力有关的体积变化系数,随基质吸力的增大,单调减小,服从幂函数关系;并且当基质吸力大于200kPa以后,随基质吸力增大,体积变化系数接近于常数,约为0.0059左右。在此基础上,本文针对这种由单纯基质吸力变化引起的非饱和土体积应变规律及机理,进行了探讨。     

临近基坑既有建筑物地基的抗剪强度指标取值问题

基坑开挖不仅改变了半无限空间体边界条件,卸载时还会引起周围地层移动,导致既有建筑物地基承载力的附加损失。在临近基坑既有建筑物地基承载力计算中,其抗剪强度参数的选取有别于斜坡上地基计算参数的常规取值方法。通过探讨临近基坑既有建筑物地基抗剪强度指标的取值问题,建议以地基土的完全软化强度与残余抗剪强度的平均值作为临近基坑既有建筑物地基抗剪强度指标,并据此估算了临近基坑既有建筑物地基承载力。所得结果与斜坡上地基承载力的试验值和理论解对比分析后显示出其具有一定的合理性。所建议的抗剪强度指标取值方法,还有待于试验的进一步验证。     

榆林黄河中游粗泥沙区生态问题与生态格局构建

黄河中游粗泥沙是黄河下游地上悬河形成的最重要组成物质,从源头遏制粗泥沙入黄是保障黄河长久安澜的根本之策。笔者采用从大尺度向小尺度梯度分析、生态问题识别诊断与综合评判等方法,确定了陕西省榆林市北部7个黄河一级支流区为粗泥沙主要来源区,并在识别出粗泥沙主要来源区生态问题及其之间关联性、紧迫度、优先度的基础上,提出了榆林黄河中游粗沙区生态保护修复的系统性对策。即围绕2个核心目标、3个关键问题,将研究区划分为10个保护修复单元,提出布局7类工程和29个子项目,构建“1廊2带3区多点” 的人与自然和谐共生的生态安全格局,从而达到提升粗泥沙集中来源区生态系统稳定性和韧性,实现从源头遏制粗泥沙入黄,缓解拦沙坝、水库和“地上悬河”泥沙淤积压力的目标。研究成果对于保障中国北方生态安全和能源资源安全等具有极为重要的意义。     

Empirical correlations of soil parameters based on Cone Penetration Tests (CPT) for Greek soils

This study presents the results of Cone Penetration Tests (CPT) and estimated correlations with the results of other in-situ tests (standard penetration test, cross-hole, seismocone) and laboratory tests (classification and undrained shear strength tests). These tests cover nearly all types of penetrable soils in Greece and, together with the formulation of empirical correlations, complement and improve on previous studies due to the significant number of CPT measurements.     

非饱和土抗剪强度理论的研究进展

非饱和土的工程性质是20世纪90年代以来国际岩土工程界研究的热点,非饱和土的抗剪强度是非饱和土的重要工程性质之一,在参阅了中、外文相关资料的基础上,总结了非饱和土抗剪强度理论的研究成果,提出了非饱和土抗剪强度有待进一步研究的问题。     

Effect of rod friction on vane shear tests in very soft organic harbour mud

Very soft organic harbour mud is increasingly used as a filling and construction material in harbour construction and reorganization. The undrained shear strength of such soft sediments is the critical geotechnical soil parameter with regard to any specific construction design. Field and laboratory vane shear testing is a standard method to quickly determine this important parameter. So far, the effect of rod friction on vane shear tests in very soft organic soils is unclear. In this study we present results from laboratory experiments on harbour mud from a construction site in northern Germany. Relations among vane and rod geometry, penetration depth, water content, rod friction and undrained shear strength are derived. Based on these relations the influence of rod friction on vane shear test results is investigated. The results indicate that field and laboratory vane shear test measurements may be significantly influenced by rod friction. Methods are proposed to correct for the rod influence, which is shown to increase with rising water contents.     

福建某低品位钼矿选矿试验研究

针对福建某低品位钼矿矿石性质,确定了粗磨粗选、粗精矿再磨精选的浮选方案。采用该浮选方案及合理的选别条件,对含钼为0.08%的钼原矿选别,获得钼精矿品位52.45%、钼精矿产率为0.14%、钼回收率90.19%的良好指标。     

Mapping fractional landscape soils and vegetation components from Hyperion satellite imagery using an unsupervised machine-learning workflow

An unsupervised machine-learning workflow is proposed for estimating fractional landscape soils and vegetation components from remotely sensed hyperspectral imagery. The workflow is applied to EO-1 Hyperion satellite imagery collected near Ibirací, Minas Gerais, Brazil. The proposed workflow includes subset feature selection, learning, and estimation algorithms. Network training with landscape feature class realizations provide a hypersurface from which to estimate mixtures of soil (e.g. 0.5 exceedance for pixels: 75% clay-rich Nitisols, 15% iron-rich Latosols, and 1% quartz-rich Arenosols) and vegetation (e.g. 0.5 exceedance for pixels: 4% Aspen-like trees, 7% Blackberry-like trees, 0% live grass, and 2% dead grass). The process correctly maps forests and iron-rich Latosols as being coincident with existing drainages, and correctly classifies the clay-rich Nitisols and grasses on the intervening hills. These classifications are independently corroborated visually (Google Earth) and quantitatively (random soil samples and crossplots of field spectra). Some mapping challenges are the underestimation of forest fractions and overestimation of soil fractions where steep valley shadows exist, and the under representation of classified grass in some dry areas of the Hyperion image. These preliminary results provide impetus for future hyperspectral studies involving airborne and satellite sensors with higher signal-to-noise and smaller footprints.