Compressibility and Strength Behaviour of Sand–tyre Chip Mixtures

Scrap tyres can be shredded into chips and can easily be mixed with granular soils. To assess the behaviour of the admixtures, compressibility and triaxial compression tests were carried out by varying chip size and chip content. The results demonstrated that sand–tyre chip mixtures up to 20% could be a potential material for highway construction and embankment construction up to around 10 m height.     

Drainage Performance of Different Sizes Tire Chips used Alone and Mixed with Natural Aggregates as Leachate Drainage Layer Material

Results of compressibility and hydraulic conductivity testing performed under different levels of average vertical stress were used to determine the appropriate tire chips size (in particular aspect ratio) and tire chip—gravel random state mix combination. Proper sidewall treatment was provided to reduce side wall friction up to minimum level and constant head conditions were maintained with appropriate design flow rate. Results showed that tire chips (length 25 mm, aspect ratio 1) mixed with 40 mm gravel in the random state in mixing ratio of 3:1 (ds:dg) was observed to undergo minimum strain, maximum hydraulic conductivity and hence free drainage even under high vertical stress levels. By selecting tire chips of appropriate aspect ratio and optimum mix combination for the construction of drainage layer of MSW landfill leachate collection system lower strain response, higher hydraulic conductivity values and relatively free drainage even under anticipated higher vertical stress levels may be achieved.     

Influence of size of granulated rubber and tyre chips on the shear strength characteristics of sand–rubber mix

Use of scrap tyres in isolation systems for seismic damping, requires a knowledge of the engineering properties of sand–rubber mixtures (SRM). The primary objective of this study is to assess the influence of granulated rubber and tyre chips size and the gradation of sand on the strength behaviour of SRM by carrying out large-scale direct shear tests. A large direct shear test has been carried out on SRM considering different granulated rubber and tyre chip sizes and compositions. The following properties were investigated to know the effect of granulated rubber on dry sand; peak shear stress, cohesion, friction angle, secant modulus and volumetric strain. From the experiments, it was determined that the major factors influencing the above-mentioned properties were granulated rubber and tyre chip sizes, percentage of rubber in SRM and the normal stress applied. It was observed that the peak strength was significantly increased with increasing granulated rubber size up to rubber size VI (passing 12.5 mm and retained on 9.5 mm), and by adding granulated rubber up to 30%. This study shows that granulated rubber size VI gives maximum shear strength values at 30% rubber content. It was also found that more uniformly graded sand gives an improved value of shear strength with the inclusion of granulated rubber when compared to poorly graded sand.     

Effect of strain rate on strength properties of low-calcium fly-ash-based geopolymer mortar under dry condition

This paper presents the mechanical and elastic properties of inorganic polymer mortar under varying strain rates. The study includes a determination of the compressive strength, modulus of elasticity and Poisson’s ratio at 0.001, 0.005, 0.01 and 0.05 mm/s strain rate. A total of 21 cylindrical specimens having 100 mm length and 50 mm diameter were investigated, and all tests were carried out pursuant to the relevant Australian Standards. Although some variability between the mixes was observed, the results show that, in most cases, the engineering properties of geopolymer mortar compare favourably to those predicted by the relevant Australian Standards for concrete mixtures. It was found that the change in the strain rate causes different behaviour related to the percentage of the ultimate load. The ultimate strength, Young’s modulus and Poisson’s ratio of the geopolymer mortar depend on the strain rate. It was also found that as the strain rate increases, mechanical and elastic properties of geopolymer mortar substantially increase in logarithmic manner.     

PRB技术在地下水污染修复中的研究进展

在综合分析可渗透反应墙（PRB）修复污染技术基础上,提出了存在问题及发展趋势,进而理出需通过深入研究,提高修复系统性能及其可行途径。预计在不远的将来,PRB处理工艺的持续性也同样会有大幅度改进和发展。     

黏土岩时效变形特性试验与理论研究

高放废物地质处置岩体材料选取中,黏土岩因具有低渗透性、损伤自修复特性、对放射性核素具有良好的吸附作用等优点,被认为是一种合理的高放废物地质处置屏障。以黏土岩为研究对象,从黏土岩短期、长期力学特性等方面开展研究工作,主要内容如下：（1）进行黏土岩短期自然固结试验,确定了黏土岩的基本物理力学参数,主要包括前期固结压力、压缩指数等;（2）进行流-固耦合固结试验,试验结果表明盐水作用对黏土岩力学特性具有重要影响,且流-固耦合过程中的膨胀现象与黏土岩的黏土矿物含量和类型密切相关;（3）通过对黏土岩进行固结流变试验,研究黏土岩渗流-应力耦合作用下的长期力学特性,试验表明黏土岩具有明显的流变特性,且流变现象与载荷密切相关;（4）根据固结流变试验建立黏土岩一维流变本构模型,同时将模型计算结果与试验结果进行对比,分析表明,该模型能够很好地反映黏土岩一维固结流变特性。该研究对我国未来黏土岩高放废物处置库的规划、设计、选址和运营等具有重要的参考意义。     

Selection of permeable reactive barrier materials for treating acidic groundwater in acid sulphate soil terrains based on laboratory column tests

The Shoalhaven region of NSW experiences environmental acidification due to acid sulphate soils (ASS). In order to trial an environmental engineering solution to groundwater remediation involving a permeable reactive barrier (PRB), comprehensive site characterisation and laboratory-based batch and column tests of reactive materials were conducted. The PRB is designed to perform in situ remediation of the acidic groundwater (pH 3) that is generated in ASS. Twenty-five alkaline reactive materials have been tested for suitability for the barrier, with an emphasis on waste materials, including waste concrete, limestone, calcite-bearing zeolitic breccia, blast furnace slag and oyster shells. Following three phases of batch tests, two waste materials (waste concrete and oyster shells) were chosen for column tests that simulate flow conditions through the barrier and using acidic water from the field site (pH 3). Both waste materials successfully treated with the acidic water, for example, after 300 pore volumes, the oyster shells still neutralised the water (pH 7).     

Alkalinity production as an indicator of failure in steel slag leach beds treating acid mine drainage

Acid mine drainage is a serious environmental problem throughout mining regions of the US and around the world. In Appalachia, reuse of steel slag from steel production as a source of alkalinity for treatment of acid mine drainage has become a common practice. In these systems, dubbed steel slag leach beds, relatively clean surface water is percolated through a bed of steel slag to add large amounts of alkalinity to the water before mixing it with acidic, metalliferous mine water. These beds do not operate consistently and their failure mechanisms are poorly understood. Using the experience of Raccoon Creek watershed in southern Ohio, the alkalinity distribution of the discharge of six steel slag leach beds is compared. Two of these beds are still functional, one has been abandoned and three are operating poorly. The difference in alkalinity distribution between these beds suggests that a carbonate-dominated alkalinity system is an indicator of a poorly performing steel slag leach bed, while a more even distribution between hydroxide, carbonate and bicarbonate may point to more ideal operating conditions. In eight laboratory column experiments, this evidence was then expanded upon by testing different mixed media substrates (differing mixes of steel slag, wood chips and river gravel) to see which provided the most ideal alkalinity distributions. The columns that had steel slag mixed either with wood chips or wood chips and river gravel outperformed the column with slag only in terms of alkalinity distribution, perhaps due to microbial processes or increased hydraulic conductivity without significant added calcium or carbon that could drive calcium carbonate precipitation within the beds and causing them to fail.     

First results of operating and monitoring an innovative design of a permeable reactive barrier for the remediation of chromate contaminated groundwater

An innovative setup of a permeable reactive barrier (PRB) was installed in Willisau, Switzerland to remediate chromate contaminated groundwater. Instead of a conventional continuous barrier, this PRB consists of cylinders installed in rows: a single row for lower expected Cr^VI-concentrations and an offset double row for higher expected Cr^VI-concentrations. The cylinders are filled with reactive grey cast-Fe shavings mixed with gravel to prevent extensive precipitation of secondary phases in the pore space. The treatment of the contaminants takes place both within the cylinders and in the dissolved Fe^II plume generated downstream of the barrier. Monitoring of the contamination situation over a period of 3 a provided evidence of the mobilization, transport and behavior of the contaminants in the aquifer. Groundwater and reactive material were sampled upstream, within and downstream of the barrier by a Multi-Port Sampling System (MPSS) that revealed the geochemical processes as a function of time and space. Comprehensive chemical analyses included sensitive parameters such as Cr^VI, Fe^II/Fe^III, redox potential, dissolved O₂ and pH. Several campaigns using multiple optical tracers revealed a rather complex hydrological regime at different scales, thereby complicating the barrier performance.     

铁还原地下水环境中微生物降解苯和甲苯的碳源 专一性分析

文中研究在粒状铁化学还原三氯乙烯渗透反应格栅和生物降解苯和甲苯渗透反应格栅的联合格栅技术中,下游生物降解格栅中铁还原环境下微生物对苯和甲苯的生物降解。通过模拟粒状铁渗透反应格栅下游铁还原环境,主要研究微生物以苯、甲苯作为碳源时,对碳源的专一性。通过批实验发现,对于分别用苯和甲苯培养驯化的微生物,互换碳源后,微生物对2 000.00μg/L苯和甲苯的生物降解半衰期分别由之前的1.0和1.5 d减少到0.7和1.0 d,互换碳源后苯和甲苯的去除率分别增加38%和32%。在粒状铁渗透反应格栅下游生物降解渗透反应格栅中,微生物在铁还原环境下以苯、甲苯作为碳源时对碳源没有专一性,苯和甲苯可以同时被生物降解去除。     

土工带加筋碎石土本构关系的三轴试验研究

通过碎石土和加筋碎石土的大型三轴试验,分析了土工带加筋碎石土的变形特性和土工带加筋对碎石土应力-应变关系的影响,采用双曲线函数拟合加筋土体的应力-应变试验曲线,建立了土工带加筋碎石土的非线性模型以克服经典的刚塑体模型不能反映加筋土体在达到破坏荷载前的变形形态的缺点,提出了土工带加筋土体切线模量的计算公式,该模型能正确反映土工带加筋土体的变形特性,在岩土工程方面有一定的实际应用价值.     

Grain-size information from the statistical properties of digital images of sediment

The autocorrelation technique for estimating grain-size from digital images of sand beds has been extended and validated for use on coarse sand (0·7 mm) and gravel (up to ∼20 mm). A number of aspects of the technique have been explored and some potential improvements suggested. Autocorrelation is just one suitable statistical method sensitive to the grain-size of sediment in digital images; four additional techniques are presented and their relative merits discussed. A collective suite of techniques applicable to the general problem of grain-size estimation from digital images of sediment might broaden the applicability to more sedimentary environments, as well as improve its accuracy. These techniques are compared using a large data set from a gravel barrier beach in southern England. Based on over 180 samples, mean grain-size of sieved and imaged sediments correspond to within between 8% and 16%. Some theoretical aspects of the spatial arrangement of image intensity in digital images of natural sediments are addressed, including the fractal nature of sediments in images, which has potential implications for derivation of grain-size distributions from images of sand-sized material through segmentation and thresholding. The methods outlined in this contribution may also find application in further uncovering the geometric structure of sediment beds, as well as in the simulation of sedimentation processes.     

高温冻结砂土温度界限试验研究

由于高温冻土力学特性与融土相近,对其研究越来越多,然而迄今并没有一个广为接受的基于力学指标的明确定义。以冻结饱和标准砂为研究对象,利用三轴剪切试验和侧限压缩试验获得黏聚力、割线变形模量和压缩指数等力学指标,通过分析这些指标随温度变化的规律,试图从力学特性的角度对于高温冻结砂土给出一个明确的温度界限。研究发现,冻结砂土在-1.0℃到-0.5℃之间,黏聚力、割线变形模量和压缩指数等力学指标发生突变,因此,将-1.0℃定义为高温冻结砂土的温度界限,对涉及高温冻土的工程建设和维护具有重要的意义。     

南京长江二桥南汊桥塔基主要工程地质问题与力学参数的确定

南京长江二桥南汊桥塔基主要工程地质问题是岩石的强度问题. 由于塔基岩石为胶结差的砾岩与砂砾岩, 且结构和颗粒不均匀, 勘探中取样极为困难, 加之岩石常规试验的不适宜性, 使得岩石力学强度问题复杂化. 为此勘察期间对塔基岩石工程地质特性进行了较全面的研究, 并结合类似岩石的原位试验对比分析, 确定了符合本大桥的力学参数建议值, 为桩基的优化设计提供了可靠依据.      

地下水有机污染处理的渗透性反应墙技术

系统介绍了一种新的地下水污染原位治理方法(渗透性反应墙),具体包括渗透性反应墙的布置形式、介质选取、反应机理、应用现状以及存在问题等.在工程实践中,根据现场的水文地质条件和地下水中有机污染物的特点,可以通过改变反应墙的布置形式来有效地截获羽状体.与传统的抽出-处理系统相比,渗透性反应墙具有处理费用低、使用寿命长等特点,特别对高密度非水溶相液体(DNAPLs)形成的污染羽状体有较好的处理效果.     

An internally consistent thermodynamic data set for phases of petrological interest

The thermodynamic properties of 154 mineral end-members, 13 silicate liquid end-members and 22 aqueous fluid species are presented in a revised and updated data set. The use of a temperature-dependent thermal expansion and bulk modulus, and the use of high-pressure equations of state for solids and fluids, allows calculation of mineral–fluid equilibria to 100  kbar pressure or higher. A pressure-dependent Landau model for order–disorder permits extension of disordering transitions to high pressures, and, in particular, allows the alpha–beta quartz transition to be handled more satisfactorily. Several melt end-members have been included to enable calculation of simple phase equilibria and as a first stage in developing melt mixing models in NCKFMASH. The simple aqueous species density model has been extended to enable speciation calculations and mineral solubility determination involving minerals and aqueous species at high temperatures and pressures. The data set has also been improved by incorporation of many new phase equilibrium constraints, calorimetric studies and new measurements of molar volume, thermal expansion and compressibility. This has led to a significant improvement in the level of agreement with the available experimental phase equilibria, and to greater flexibility in calculation of complex mineral equilibria. It is also shown that there is very good agreement between the data set and the most recent available calorimetric data.     

绍兴中心城区工程地质特征及场地工程建设适宜性评价

根据时代、成因类型、物理力学性质,绍兴中心城区岩土层可划分为10个工程地质层。以地貌、岩土层性质与结构组合类型及是否存在第二硬土层、砂砾土或基岩等桩基持力层为依据,划分出1个低山丘陵区基岩岩组、1个山麓沟谷区低压缩松散岩组、1个平原区高压缩松散岩组及其4个亚组。采用"点面结合、由点到面"的定量评价方法,开展建筑地基(场地工程建设)适宜性评价,划分出场地工程建设适宜区、较适宜区和适宜性差区。     

Solid phase iron–sulfur geochemistry of a reactive barrier for treatment of mine drainage

This paper discusses the solid phase Fe–S geochemistry of a reactive barrier at the Nickel Rim mine site (Ontario, Canada). The barrier, designed to treat groundwater contaminated by acid mine drainage, is composed of leaf and municipal compost and wood chips. This study shows that S is accumulating in the organic material as primarily acid volatile sulfides, at concentrations up to 195 μmol S g⁻¹ d.w. (0.63 wt% S) in a zone of preferential flow. Pyrite and/or S⁰ account for only a small fraction of the total reduced inorganic S, as oxidants are probably present at only low concentrations in the barrier system. The results of the solid phase analyses, the formation of disordered mackinawite (Fe_1+xS) on piezometer tubing, and thermodynamic calculations indicate that the precipitation of poorly crystalline Fe monosulfides is the primary sink for Fe and S in the barrier. Siderite (FeCO₃) formation is proposed as an additional Fe sink in areas of high Fe flux. Minor accumulations of acid-soluble, organically-bound S in the reactive barrier occur in zones of low aqueous Fe concentration. After 23 months of operation, the average rate of S accumulation at the up-gradient edge of the barrier is calculated to be 87 μmol S g⁻¹ a⁻¹ (d.w. organic material), or 47 mol S m⁻² a⁻¹ in the direction of groundwater flow. Solid phase analyses from samples collected 3 and 14 months after installation indicate that the S accumulation rate declined by a factor of 3 over that time period.     

地下水有机污染控制及就地恢复技术研究进展（三）

本文是关于地下水有机污染控制及其就地恢复技术进展概况的第3篇文章，文中主要介绍渗以应格栅中的氧化－还原反应格栅和生物降解反应格栅。     

Swell–consolidation characteristics of artificial sand clay mixes

Many remedial measures have been devised to lessen the damage caused by expansive soils. Physical alteration, chemical stabilization, innovative foundation techniques like belled piers, drilled piers, under-reamed piles and granular pile anchors are some of these remedial measures. Mixing a non swelling material such as gravel or sand to expansive soil is one of the methods of physical alteration. This paper presents experimental data on artificially prepared sand-clay mixes. Swell and consolidation characteristics of these artificially prepared sand-clay mixes were studied in one dimensional consolidometer. Fine sand content and fines content in the expansive soil were arbitrarily varied in the investigation. The fines content was varied as 425–300 μm and 150–75 μm, separated from the same expansive soil based on the grain size. Swell potential and swelling pressure decreased with increasing fine sand content but increased with increasing fines content. Coefficient of compressibility, coefficient of volume compressibility and compression index of the samples decreased initially up to a sand content of 15% and thereafter increased at higher sand contents.