Granulometry,cluster analysis and spatial distribution of manganese contaminated soils,Kgwakgwe, southeastern Botswana

The particle size distribution (PSD) of 400 Mn contaminated soil samples was established, and generated data were statistically analysed and spatially presented. The PSD for the 53 µm – 4 µm size fraction soil samples ranged from 11.05 to 100 wt %, whereas that for < 4 µm was from 0.3 to 30 wt %. Texturally, samples were dominantly silt loam, although silt and sandy loam were also present, as well as loam, loamy sand and clay classes. Six clusters were identified with cluster one being the most dominant occurring in sandy loam, silt loam and loamy sand. The < 53 µm fraction had three dominant areas, and the < 4 µm fraction had several unevenly presented populations as reflected in the maps. Because of its spatial distribution, the < 4 µm fraction may pose hazards to human health. Furthermore, predominance of Mn limits land use to subsistence agriculture with possibly low crop yield.     

Stormwater quality associated with a silt trap (empty and full) discharging into an urban watercourse in Scotland

The aim was to assess the influence of a full silt trap at the end of a stormwater drainage pipe on the water quality of stormwater discharged into a semi‐natural urban watercourse. For approximately eleven weeks, the water qualities of the preliminarily treated stormwater and of the receiving watercourse (Braid Burn) were studied. The mean outflow concentrations of suspended solids were 2.0 mg/l and 34.1 mg/l during dry and wet weather conditions, respectively. Suspended solids concentrations of up to 141.6 mg/l were recorded during storm events. Suspended solids values for treated stormwater were often too high compared to international secondary wastewater treatment standards of around 30 mg/l. Pollutants including heavy metals (e.g., zinc, copper and nickel) accumulated in the silt trap. However, high outflow velocities during heavy rainfall events did not result in clearly defined sediment layers due to sediment re‐suspension. Metals did not accumulate in the receiving watercourse.     

粉喷桩技术在地基处理中的应用

介绍粉喷桩技术在揭东县松山排涝站泵房地基处理中的应用情况,重点介绍粉喷桩设计、施工及质量检验,应用结果表明:采用粉喷桩处理软弱地基,具有工期短、造价低、施工干挠小及效果好等优点.     

浪店水源泵站工程应用大型潜水轴流泵的可行性

浪店水源工程位于黄河小北干流，该河段河势游荡不定，引水口位置难以确定，为了适应河势变化，提高取水保证率，取得长远较好的社会效益，拟采用可移动的大型潜水轴流泵。本文就该工程应用此泵的可行性作一分析。     

Improvements in small-scale standardized testing of geotextiles used in silt fence applications

Silt fence have been used as a means for intercepting and treating construction site stormwater runoff prior to offsite discharge for well over 30 years. Standard small-scale testing methodologies for evaluating the filtering component of silt fence installations have failed to mimic realistic flows and sediment loadings commonly seen in field applications. To address these issues, this study evaluated the performance capabilities of two nonwoven and three woven silt fence geotextiles using an innovative testing methodology and a newly developed small-scale testing apparatus. The overall intent for conducting the evaluations was to develop a deeper understanding of effluent flow rates, sediment retention capabilities, and water quality impacts associated with geotextile fabrics. Results suggest that effluent flow rates of nonwoven geotextiles are on average 43% lower than woven materials, which results in extensive upstream retention times of impounded stormwater for nonwoven materials. Sediment retention results indicate that nonwoven geotextiles have an average sediment retention rate of 97% while woven geotextiles average 91%. Finally, water quality analyses suggest that the primary means for turbidity reductions rely on the process of sedimentation during the 30-min test period (i.e., 46% reduction) and filtration during the 90-min dewatering period (i.e., 19% reduction).     

城市大型立交桥整体爆破拆除

介绍了复杂环境下数码电子雷管在城市大型立交桥爆破拆除中的应用。该桥为三层互通式,桥梁路线长,桥下淤泥层深厚。采用深孔为主、浅孔为辅的爆破技术,数码电子雷管网路为主、非电网路为辅的复式起爆网路。数码电子雷管网路既能减少多层立交桥桥体在爆破拆除塌落中的相互干扰又能利用其高精度毫秒延时特点达到减振目的。采用孔外延时起爆技术,铺设缓冲层和挖减振沟等多种减振措施,降低在淤泥地质上的触地振动。同时采用爆破水雾降尘等技术缓解了爆破拆除的粉尘危害,达到了良好的拆除爆破效果,可为同类工程提供参考。     

Cyclic properties of dense to very dense silica sand

This paper presents results of a series of cyclic laboratory test performed on dense to very dense silica sand. Triaxial and direct simple shear tests were performed on reconstituted sand. The test program aimed to determine the cyclic shear strength and soil deformation properties for foundation design of offshore wind turbine structures on the Dogger Bank site, offshore United Kingdom, but is also applicable for foundation design of other offshore structures and other locations. Two sand batches were used, one with clean silica sand and one with 20% silt content. Normally consolidated specimens from both batches were reconstituted to a target relative density approximately equal to 100% and 80%. On the clean sand with a target relative density of 80%, tests were also performed on specimens with an overconsolidation ratio of OCR = 4. Various contour diagrams, presenting cyclic shear strength and average and cyclic shear strains for different number of cycles, are presented. These diagrams can be used in the front-end engineering design (FEED) stage of commercial design projects on similar soil conditions, to define soil behavior when limited cyclic data is available, or in the planning stage of a cyclic laboratory test program. Effects of precycling and fines content on the cyclic behavior of triaxial and DSS specimens are discussed.     

Selection of silt fence filter to retain suspended toxic particles

A silt fence filter was required to retain potentially toxic particles of 0.1 mm-diameter and larger that could become suspended in water decanted from contaminated dredge spoils. An experimental study was performed to select it. The experiments consisted of two parts, Part 1 tests were conducted according to an accepted engineering standard to compare four candidate geotextiles. Part 2 tests simulated expected field conditions, and were conducted to determine whether one geotextile selected from the Part 1 tests was likely to perform well. The geotextile selected for Part 2 tests retained particles of 0.1 mm and larger, and was installed as a silt fence filter in the field. The silt fence filter was removed shortly after dredging began because it clogged, primarily due to unexpected, high amounts of suspended sediment in the supernatant. The design of the support structure for the silt fence did not permit maintenance of the filter, which may have prevented its failure. The failure may also have been prevented if salt or other materials used to promote flocculation of the dredged spoils were readily available and used on the spoils. The selection procedure described may be helpful because the conditions tested for in the laboratory are likely to occur or could be induced.     

大口径管道穿越复杂岩土层的方案设计

本文主要结合工程实例,介绍管道长距离穿越复杂岩、土层的敷设方案,尤其是穿越岩、土互换土层情况下的设计方案,可供类似工程设计参考。