Ohmic Conductivity of a Compacted Silty Clay

In its natural state, loess can be considered as an unstable soil, which develops large deformations when moistened. In Argentina, loess is used in most Geotechnical constructions, including embankments and liners. The interest of this work to evaluate the potential application of electrical conductivity measurements for monitoring the effects introduced by remolding and compaction in the soil. Samples of loess were compacted at varied densities and mixed with electrolytes of different concentrations. Electrical conductivity was measured with a two electrode cell. The effects introduced on the measured conductivity by frequency, degree of saturation, soil density, temperature, and electrolyte type and concentration are addressed. Additionally, hydraulic permeability tests were performed on compacted specimens of loess and the relationship between electrical and hydraulic conductivity was determined. It is concluded here that the ohmic conductivity of compacted specimens depends mainly on the salt concentration in the pore fluid, and volumetric water content. The effect of compaction density was observed to be less significant. The whole behavior of electric conductivity of loess is well described by the Archie’s law.     

FeO-MgO-CaO-SiO2系炉渣电导的测定与研究

对FeO-SiO2-MgO-CaO渣系的电导率进行了测试研究。结果表明,在CaO6%,Fe/SiO2=1.2时,随着MgO含量的增加,熔渣电导率增大。MgO11%,Fe/SiO2=1.2时,电导率随CaO含量的增加而增大,当CaO含量大于6%,CaO含量的变化对电导率的影响较弱。电导率随Fe/SiO2比值增加而增大。温度增加,熔渣电导率增大。     

Effect of Penetration Rate on Cone Penetration Resistance in Saturated Clayey Soils

In this paper, the effects of penetration rate on cone resistance in saturated clayey soils are investigated. Shear strength rate effects in clayey soils are related to two physical processes: the increase of shear strength with increasing rate of loading and the increase of shear strength as the process transitions from undrained to drained. Special focus is placed on this second effect. Cone penetration tests were performed at various penetration rates both in the field and in a calibration chamber, and the resulting data were analyzed. The field cone penetration tests were performed at two test sites with fairly homogeneous clayey silt and silty clay layers located below the groundwater table. Additionally, tests with both cone and flat-tip penetrometers in sand-clay mixtures were performed in a calibration chamber to investigate the change in drainage conditions from undrained to partially drained and from partially drained to fully drained. A series of flexible-wall permeameter tests were conducted in the laboratory for various clayey sand mixtures prepared at various mixing ratios in order to obtain values of the coefficient of consolidation, which is required to estimate the penetration rates below which penetration is drained and above which penetration is undrained. A correlation between cone resistance and drainage conditions was established based on the results of the calibration chamber and field penetration tests.     

Determination of Temperature Dependence of Electrical Conductivity and Its Relationship with Ionic Strength of Anaerobic Digester Supernatant, for Struvite Formation

Electrical conductivity (EC) is used for monitoring different types of aqueous systems. The measured EC value at any temperature needs to be corrected for a standard temperature, for reporting or comparison, since EC is dependent on temperature. A temperature compensation factor has been derived for conductivity correction from anaerobic digester supernatant/centrate samples of five different wastewater treatment plants in western Canada. For a temperature compensation factor of 0.0198°C?1, corresponding to the standard temperature at 25°C, the estimated EC25 values were found to be reasonably accurate, with a maximum error of 2.01%. The estimated EC values, based on any standard temperature, were found to be statistically similar to each other. Considering the temperature dependence of EC, a relationship between EC and ionic strength was developed in this study for anaerobic digester supernatant/centrate samples. This relationship can be used to estimate the ionic strength of the solution in a system associated with struvite formation from anaerobic digester supernatant/centrate and effectively monitor the system performance.     

电除尘器运行中效率降低的原因分析及处理方法

分析了1050 m3生铁炉出铁场和矿槽系统电除尘在运行过程中效率降低的原因,并提出了解决的措施。     

套筒石灰窑的发展概况

简述了套筒石灰窑的发展过程,介绍了套筒石灰窑基本结构、工作原理以及存在的问题,并对套筒石灰窑发展方向提出了建议.     

稀土对铝导线导电性能和力学性能的影响

本文研究了工业生产条件下，稀土铈、镧及混俣稀土对电工用铝导线导电性能和力学性能的影响。结果表明，稀土铈可显著提高强度，稀土镧可显著提高导电性。实验证明，稀土元素的添加量选择在０．２－０．３Ｗｔ％的最佳。     

高电导率高屈服强度铝合金的研制

用正交试验法对比分析了纯铝合金中添加Fe、Cu、Mg、Zn对其电导率及屈服强度的影响程度;并由此进行成分配比,通过挤压加工试验,研制出一种高电导率高屈服强度铝合金型材,H112状态电导率达60％IACS左右、屈服强度σ0．2大于90MPa．     

Spatial Variability in Soils: High Resolution Assessment with Electrical Needle Probe

The global response of a soil is affected by spatial as well as temporal scales. An electrical needle-size probe is developed to effectively assess one-dimensional spatial variability. The probe is designed for laboratory specimens (needle diameter 1.2–2.2 mm), and it can be scaled for field applications. Design considerations include the tip shape, insertion disturbance, electrochemical effects, corrosion, operating frequency, and electrical resonance. Two calibration methods are presented to determine local soil permittivity and resistivity from the measured complex impedance; the simplified calibration procedure is based on resistance measurements only. The local electrical parameters permit one to infer the soil porosity and the electrolyte conductivity. The attainable spatial resolution depends on the needle diameter; submillimetric resolution is typically achieved in laboratory applications. Reconstituted sand specimens and undisturbed clayey specimens are tested to explore the resolution potential of this probe. The electrical needle probe clearly detects the spatial variability that results from different specimen preparation methods in sands and soil layering from natural formation histories such as those in varved clays.     

高导电高耐磨铜基复合材料的研究进展

综述了铜基耐磨复合材料的研究发展现状,介绍了铜基耐磨材料种类、制备方法和增强机理.指出陶瓷颗粒增强铜基复合材料具有较高的耐磨性、高温力学性能和较低的热膨胀系数,且制备工艺简单、成本较低,粉末冶金法仍是当今制备和研究碳纤维和陶瓷颗粒增强铜基复合材料的重要方法,而原位反应合成技术由于具有显著的技术和经济优势,也具有很好的发展前景.     

7085铝合金锻件强度、硬度和电导率关系研究

采用拉伸测试、硬度测试和电导率测试研究了过时效状态下7085铝合金锻件强度、电导率和硬度三者之间的对应关系.结果显示强度与电导率和硬度存在线性对应关系,强度与电导率对应关系式为σb＝-21.085 γ +1396.7,强度与硬度对应关系式为σb＝6.866H-75.53,强度与电导率和硬度拟合结果与实际测试结果符合较好.因此,在实际生产中可以用硬度及电导率等快速检测方法监控产品质量.     

Evaluation of a Dielectric Sensor for Measurement of Soil-Water Electrical Conductivity

The salinity status of soil can be obtained through the measurement of the pore-water electrical conductivity σp. In the present study the WET sensor’s capability in predicting σp through the simultaneous measurements of the soil bulk electrical conductivity (σb) and the soil dielectric constant (K) is investigated. The estimation of σp is based on a model by Hilhorst, which relates σp to the two other quantities K and σb and an extra fitting parameter K0 which is incorporated in the software of the device. The study involved experimental measurements in the laboratory using four different soils with a large range in soil texture and volumetric water content θ. In each soil type four different electrical conductivity aqueous solutions were used. The results exhibited a rather strong linear relationship between K and σb. The slope of this linear relationship appeared to depend on both the soil type and the electrical conductivity of the pore water. The value of K0 seems to be soil specific and increases when the salinity level increases. The σp prediction according to the linear model of Hilhorst deviates for almost all soils tested, except for the case of the sandy soil. Besides the linear model of Hilhorst, the Malicki and Walczak linear model was also tested for all soils under investigation and the model of Munoz-Carpena et al. was tested for sand. Malicki and Walczak model performance at predicting σp values was approximately the same as the Hilhorst model for sand and slightly better for sandy loam. In general, one could argue that the linear models could predict σp with some accuracy for the cases of coarse porous media.     

石灰回转窑窑尾粉尘超低排放的对策

针对鞍钢股份有限公司鲅鱼圈钢铁分公司石灰回转窑窑尾粉尘未达到超低排放标准的问题,采取了优化除尘器滤料、滤袋结构、布袋喷吹制度,优化风煤配比和治理除尘器漏风率等措施后,回转窑窑尾粉尘浓度降至6 mg/m^3,氧含量控制在10%以下,达到了超低排放的目标。     

形变时效处理对铝合金电工圆杆抗拉强度和导电率的影响

探究不同变形量形变热处理对铝电工圆杆导电率及抗拉强度的影响。结果表明,随着轧制变形量的增加,试样的导电率先增加后降低,其抗拉强度得到较大的提升。形变时效后,试样的晶界薄化,组织更加均匀,基体中第二相粒子的含量增加,且出现新相SiB_6、Al_(3.21)Si_(0.47)、Cu_3Fe_(17)、Al_2FeSi。通过"535℃×5h固溶处理+83%轧制+190℃×10h时效"的形变热处理后,试样抗拉强度达到234MPa的峰值,导电率为53.45%IACS。     

Computational Techniques and Shear Band Development for Cylindrical and Spherical Penetrometers in Strain-Softening Clay

This paper addresses numerical simulation of deep penetration of full-flow penetrometers in strain-softening, rate-dependent, cohesive soil, and the observed phenomenon of periodic shear bands. The analysis was conducted using a large deformation finite element approach, modifying the simple elastic–perfectly plastic Tresca soil model to allow strain-softening, with strain-rate dependency being incorporated in order to avoid spurious mesh dependency. Parametric analyses were carried out varying the strain-softening parameters (hence the relative brittleness of the soil), the rigidity index of the soil, and the strain-rate parameter. Increased brittleness of the soil led to reduction in the penetration resistance, but also to increasingly significant oscillations in the resistance–penetration responses. The oscillation was found to result from periodic shear bands evolving cyclically ahead of the advancing cylindrical and spherical penetrometers. Analyses with different values of rigidity index confirmed further that the periodic shear bands were a real material phenomenon, rather than due to errors in numerical simulation. Similar phenomena have been observed for continuous flow problems in granular materials. However, rising strain-rate dependency tended to suppress the oscillations.     

Determination of Hydraulic Conductivity Using Piezocone Penetration Test

An elastoplastic, finite-strain, coupled theory of mixtures in an updated Lagrangian reference frame is applied to the piezocone penetration test to estimate the hydraulic conductivity of the soil via analysis of the steady-state excess pore pressure generated during piezocone penetration. The results of this approach were compared with piezocone penetration test data. It showed that reliable hydraulic conductivities can be estimated conveniently without performing pore pressure dissipation tests. This study also shows that the change in the dimensionless excess pore pressure (excess pore pressure is normalized by the effective overburden pressure) at the cone tip is almost constant when the dimensionless hydraulic conductivity (hydraulic conductivity is normalized by the penetration speed and cone radius, hereafter called DLHC) is less than 10?7 or greater than 10?4. It is also shown that the drainage condition around the cone tip is close to a fully undrained condition when the DLHC of the soil is less than 10?7, while it is close to a fully drained condition when the DLHC of the soil is greater than 10?4.     

Effect of Penetration Rate on Penetrometer Resistance in Clay

This paper discusses the effects of penetration rate on the penetration resistance in soft clay for various shaped penetrometers (cone, T-bar, ball, and plate) and for T-bars with different aspect ratios. Constant rate (“normal”) and variable rate (“twitch”) penetration tests, where the penetration rate was successively halved over eight steps with the penetrometer advanced by one or two diameters in each step, were undertaken in the beam centrifuge at the University of Western Australia. The tests were conducted on samples reconstituted from clay collected from the Burswood site in Western Australia. The twitch tests showed higher penetration resistance than the corresponding normal tests after the penetration rate had been reduced by a factor of 16 due to cumulative effects of partial consolidation. The penetration rate at which the resistance started to increase due to partial consolidation was used to estimate the consolidation coefficient, cv, of the reconstituted clay. The interpreted cv values were similar to values estimated from other consolidation data, both in the centrifuge and from laboratory Rowe cell and constant rate of strain consolidation tests. In addition, results from in situ twitch tests at the Burswood site were examined to evaluate viscous effects on the penetration resistance.     

熔渣导电性的研究

以固体电解质脱氧为例,分析了渣金反应的电化学机理。结合熔渣导电性方面已有的研究成果及应用情况的分析得出结论：一切有利于熔渣中电子和（或）空穴在金属与熔渣界面传递的措施,都将大大提高金属与渣相的反应速率。     

白灰窑自动控制系统的开发应用

介绍了白灰生产中自动控制系统的硬件配置、软件的开发及应用情况。此系统已投入使用,性能稳定,控制准确,取得了明显的效益。     

Hydraulic Conductivity of Geosynthetic Clay Liners Exhumed from Landfill Final Covers

Samples of geosynthetic clay liners (GCLs) from four landfill covers were tested for water content, swell index, hydraulic conductivity, and exchangeable cations. Exchange of Ca and Mg for Na occurred in all of the exhumed GCLs, and the bentonite had a swell index similar to that for Ca or Mg bentonite. Hydraulic conductivities of the GCLs varied over 5 orders of magnitude regardless of cover soil thickness or presence of a geomembrane. Hydraulic conductivity was strongly related to the water content at the time of sampling. Controlled desiccation and rehydration of exhumed GCLs that had low hydraulic conductivity (10?9?to?10?7?cm/s) resulted in increases in hydraulic conductivity of 1.5–4 orders of magnitude, even with overburden pressure simulating a 1-m-thick cover. Comparison of these data with other data from the United States and Europe indicates that exchange of Ca and/or Mg for Na is likely to occur in the field unless the overlying cover soil is sodic (sodium rich). The comparison also shows that hydraulic conductivities on the order of 10?6?to?10?4?cm/s should be expected if exchange occurs coincidently with dehydration, and the effects of dehydration are permanent once the water content of the GCL drops below approximately 100%. Evaluation of the field data also shows that covering a GCL with a soil layer 750–1,000?mm thick or with a geomembrane overlain by soil does not ensure protection against ion exchange or large increases in hydraulic conductivity.