A new technique to reduce the radioactivity of fly ash utilized in the construction industry

High volume utilization of industrial wastes and by products is the solution for high disposal costs. Acceptable radioactivity levels in addition to other environmental factors is a key factor for safe utilization of wastes and byproducts of coal burning power plants. In general the radioactivity levels of most fly ashes are similar to natural materials. For higher radioactivity fly ash the radioactivity values must be reduced to acceptable limits. This can be done by mixing the fly ash with less radioactive natural materials. In this study a new technique involving the use of snow as an additive to the compaction water of fly ash is presented. Fly ash at optimum water content, and fly ash with additional 10% by weight snow are compacted, hermetically sealed to allow for equilibrium of ²²⁶Ra and ²³²Th with their decay products and cured for 28 days at the curing room. Radioisotope activity analysis are conducted with a gamma analyst integrated gamma spectrometer. The activities of ²³⁵U, ²²⁶Ra, ²³⁸U, and ²³²Th of the fly ash and snow-added fly ash samples compacted at optimum moisture content are determined. The control samples revealed radioactivity values above UNIPEDE maximum allowable limits. Addition of snow caused a decrease of 31-42% in the radioisotope activity levels to that of control samples in Bq kg⁻¹.The decrease in radioactivity is linked to increased void ratio after melting of ice, increased densification of matrix around the pores due to higher level of cementitious mineral formation. The decrease in the radioisotope activity levels will allow utilization of fly ash in highway embankment construction where large surface area exposure and large volume usage makes it more critical for human health. Another advantage of the developed technology is the reduction of transportation costs by more than ten per cent by using less material for construction.     

堤防工程环境地质问题的分析及评价方法

近几年来，随着我国堤防建设的高潮，堤防工程环境地质问题也越来越被人们注意，本作旨在探讨堤防工程环境地质问题产生的成因机制和影响因素，继而对其进行分析评价，从而提出减免堤防工程影响环境的对策。     

Failure Analysis of a Bridge Embankment with Cracked Approach Slabs and Leaking Sand

This paper describes a successful failure analysis to determine the causes of loss of backfill sand from a mechanically stabilized earth (MSE) wall, and cracks on the concrete approach slabs on top of it. The Texas Department of Transportation was concerned that the cracks on the approach slabs may be related to the excessive loss of backfill from behind the MSE walls, and that the embankment structure may be unsafe due to potential voids under the concrete slab. Several cubic meters of sugar sand had washed out of the wall and deposited adjacent to the paneled walls. A series of destructive and nondestructive tests were carried out to determine the causes of the problems. It was found that the cracking of the approach slab and the loss of backfill were unrelated. Suggestions for resolving both problems were made based on this study.     

荆南长江干堤垂直防渗工程安全监测

在 1999～ 2 0 0 0年长江堤防隐蔽工程建设中 ,荆南干堤采用了水泥土防渗墙垂直截渗的方案。为了解防渗墙的截渗效果及大堤可能出现的险情 ,从公安埠河镇至斗湖堤镇 (全长 40 km )共 9个断面布置了安全监测仪器。汛期 ,实测防渗墙前后水头差达 1.0～ 3.0 m ,实测大堤最大水平位移为 2 .0 m m。观测成果表明 :荆南长江干堤在实施水泥土防渗墙后 ,延长了堤基的渗径 ,水泥土防渗墙起到了较好的截渗作用。     

Numerical modeling of floating geosynthetic-encased stone column–supported embankments with basal reinforcement

The performance of the floating geosynthetic-encased stone column–(GESC)-supported embankments with basal reinforcement was examined using a 3-dimensional (3D) hydro-mechanical coupling finite element model. Comprehensive parametric analyses were performed on the governing factors such as consistency of substratum soil, tensile stiffness of basal reinforcement and encasement, and embankment height. The results indicated that a higher embankment load is transferred to the surrounding soil when a GESC was constructed on a weaker substratum. This causes larger increases in the settlement and lateral displacement of the GESC on the weaker substratum. The tensile strain of the basal reinforcement and hoop strain in the encasement also increases. In addition, high tensile stiffness in basal reinforcement and encasement is necessary to ensure feasible settlement reduction in a floating GESC-supported embankment with basal reinforcement.     

浅谈堤防工程防洪预案的编制与实施

介绍了堤防工程防洪预案的编制和实施措施．     

Numerical analysis and geophysical monitoring for stability assessment of the Northwest tailings dam at Westwood Mine

The Westwood Mine aims to reuse the tailings storage facility #1(TSF #1) for solid waste storage, but,downstream of the Northwest dike is considered critical in terms of stability. This paper uses numerical modeling along with geophysical monitoring for assessing the Northwest dike stability during the restoration phase. The impact of waste rock deposition in the upstream TSF #1 is considered. The geophysical monitoring is based on electrical resistivity methods and was used to investigate the internal structure of the dike embankment in different deposition stages. The numerical simulations were performed with SLOPE/W code. The results show a factor of safety well above the minimum recommended value of 1.5. Geophysical monitoring revealed a vertical variation in the electrical resistivity across the dike, which indicates a multilayer structure of the embankment. Without any current in situ data, the geophysical monitoring helped estimating the nature of the materials used and the internal structure of the embankment. These interpretations were validated by geological observation of geotechnical log of the embankment. Based on this study, it is recommended that the water polishing pond be partly filled before waste rock is deposited in TSF #1. In addition, to ensure the stability of the dike, the piezometric head monitoring prior to and during waste rock deposition is recommended.     

探讨河道综合整治理念与生态护岸

通过月明河河道综合整治项目,分析了河道现状存在的主要问题,根据综合整治的设计理念,提出了整治原则和目标,确定了综合整治的主要措施是清淤切滩、清障疏浚、生态护岸、截污治污、景观设置等,旨在提高河道行洪排沥能力、改善沿河生态环境、营造城市美丽河道景观,提高城市品位。