复杂环境条件下深基坑综合支护措施的应用

北京某交易中心一期基坑工程属大型深基坑工程，各种地下管线和地上建(构)筑物复杂，介绍了针对其复杂环境条件的综合支护措施的设计思路与实际应用效果。     

长沙现代大厦复合土钉墙基坑支护方案设计

分析了长沙现代大厦基坑的岩土工程条件及周边环境条件，在此基础上对几种基坑支护方案进行了分析论证，并对所采用的复合土钉墙支护方案进行了设计计算。     

地热井常见主要问题分析与研究

针对目前地热井施工技术现状及地热井使用中常见的问题，进行了较为详细的分析和研究，并就今后发展方向和建议进行了初步探讨。     

视电阻率观察中一种抗介质干扰的尝试

埋地金属管线对视电阻率的观测危害甚大。造成观测值大幅改变，跳动，无规律可循。严重时，甚至台站报废，被迫搬迁。通过一些突发事件的启发，结合现场实验，并引证了一些理论计算，笔者摸索出了只须对金属管道作局部微小的改造，就能基本克服其对观测的干扰的方法。该方法在红格台试验半年多来，取得了明显的效果。观测值恢复到安装的水管以前的水平，再无大幅度的跳动。该方法节约经费，简单易行，大大提高了台站在复杂环境中的生存能力。     

Chemical forms of heavy metal contaminants in sediments of Miyun reservoir

The chemical forms, spatial distribution and sources of As, Hg, Cd, Pb and Zn in sediments of the Miyun reservoir were studied. The results of sequential extraction demonstrate that most of As, Pb and Zn were bound to the residual fraction, Hg was associated with the sulfide fraction while Cd was associated with the carbonate fraction and the residual fraction. On the vertical profiles the concentrations of the heavy metals in total and each fractions mostly decreased with increasing depths in sediments, suggesting that the heavy metals input from the upstream watershed increases yearly. Summation of the residual fraction, the sulfide fraction and the carbonate fraction accounts for 60.03%―85.60% of the total heavy metal contents in the sediments, which represent the geochemical background values of the elements and relate closely to soil erosion. Results of the main factor analysis show that most sediments of the reservoir come from the upstream soil erosion, the point source pollution and domestic waste. Moreover, the microbial activities taking place on the sediment-water interface are also one of the major factors to cause the increasing content of the organic matter fraction and the iron-manganese oxide fraction. Environmental change of the reservoir water could make the removability of the heavy metals increase, leading to the increase of their concentrations in pore water in sediments, and imperiling water quality of the reservoir.     

Microorganisms in Lianxian lateritic gold deposit in Guangdong and their effects on leaching of heavy metals

Microorganisms in the lateritic profiles of the Lianxian gold deposit in Guangdong were cultured, isolated and identified. The microorganisms include bacteria such as Bacillus, Enterobacter, Pseudomonas, Lactobacillus, Actinetobacter, Aeromona, Listeria, Agrobacteriura, Cotyttebacteriurn, and Moraxella, fungi such as Penicillium, Alter naria, Cladosporium, Saccharcornyces, Mucor, and the chemoautotrophic Thiobacillu.~. It is shown in a leaching experiment that the microorganisms can accelerate the leaching of Cu, Cd, Zn, and that the G- bacteria are most efficient for leaching Cu, Zn and the G^ bacteria are better for leaching Cd.     

Efficient use of resources: urban waste ash and soil fertility on the Jos Plateau, Nigeria

Waste disposal constitutes an acute problem in numerous African cities. One solution could lie in the recycling of the nutrient-rich waste into agriculture taking place in and around cities. Farmers involved in vegetable production around Jos, Nigeria, have developed a sophisticated soil fertility management strategy combining inorganic fertilizers, manure and urban waste ash. This paper: (1) investigates the socio-economic constraints linked to obtaining scarce organic inputs, particularly urban waste ash and the health hazards (particularly heavy metal contamination of soil and crops) caused by using this ash and (2) suggests ways to improve use of this important resource.     

Mathematical model for hydraulically aided electrokinetic remediation of aquifer and removal of nonanionic copper

One of the most cost-effective in situ technologies for soil and groundwater (i.e., aquifer) remediation is electrokinetic remediation. In electrokinetic remediation, electromigration due to electric field is combined with hydromigration due to hydraulic flow by purge water to remove pollutants from aquifers through the pore water. This study aims at investigating theoretically the role of electromigration (as active movement) of pollutants and the role of hydromigration (as passive movement) of pollutants in electrokinetic remediation, and making it clear that the control variables for electrokinetic remediation are the applied voltage and the hydraulic flow rate. These aims are pursued by construction of a mathematical model based on physico-chemical considerations and by model simulations of the electrokinetic remediation applied to the virtual aquifer polluted by heavy metals of copper sulfate. According to numerical simulations with the model: (1) heavy metal (nonanionic copper) is removed from the upstream anode region and accumulated in the downstream cathode region; (2) to carry away the heavy metal outside the aquifer (global removal), hydromigration by purge water flow is essential; and (3) electromigration contributes mainly to the redistribution of heavy metals within the aquifer (local removal and local accumulation).     

土钉与锚杆联合支护在深基坑工程中的应用

结合深圳市星海阁办公楼的工程实例,从周边环境对深基坑支护的特殊要求及复杂的地质条件出发,论述了采用土钉与锚杆联合支护形式的依据.介绍了在深基坑支护施工中采取的具体措施后期效果.同时分析了这种联合支护结构形式的力学特点,通过将两者联合使用,可实现锚杆支护结构水平侧移小和土钉支护结构受力合理的优点.且土钉与锚杆联合支护,使得上部锚杆和中下部的土钉墙两者形成了统一的受力整体,共同抵抗荷载和变形.     

Parallelized combined finite-discrete element (FDEM) procedure using multi-GPU with CUDA

This paper focuses on the efficiency of finite discrete element method (FDEM) algorithmic procedures in massive computers and analyzes the time-consuming part of contact detection and interaction computations in the numerical solution. A detailed operable GPU parallel procedure was designed for the element node force calculation, contact detection, and contact interaction with thread allocation and data access based on the CUDA computing. The emphasis is on the parallel optimization of time-consuming contact detection based on load balance and GPU architecture. A CUDA FDEM parallel program was developed with the overall speedup ratio over 53 times after the fracture from the efficiency and fidelity performance test of models of in situ stress, UCS, and BD simulations in Intel i7-7700K CPU and the NVIDIA TITAN Z GPU. The CUDA FDEM parallel computing improves the computational efficiency significantly compared with the CPU-based ones with the same reliability, providing conditions for achieving larger-scale simulations of fracture.