广州航空邮件处理中心土洞及桩端软土层处理工艺研究

广州航空邮件处理中心位于岩溶发育地区,场区内存在大量土洞、溶洞等不良地质现象。该建筑物拟采用静压桩基础。为保证建筑物及场道安全,须对场区土洞进行处理。结合场地具体情况和施工工期要求,首先对大体积土洞进行泵注细石砼骨料充填处理,以消除地面大面积塌陷的危险,消灭压桩机械施工安全隐患,然后开始进行静压桩基础施工,同时在场地允许区域对中小体积土洞、桩端软土层等分别进行泵注砂浆骨料和袖阀注浆处理．以确保洞体密实和保证桩基承载力。通过对处理工艺、处理范围的比较筛选和对质量控制要点、施工技术要点的分析提炼．达到了施工简便、造价合理、安全高效的目的,并采用骨料取芯检测、土体标贯试验和压缩试验、洞体物探等多种检测手段,完全达到了设计要求,取得了良好的工程效果和经济效益。     

施工顺序对软土地坪复合地基的影响探讨

场地回填土与搅拌桩施工顺序将直接影响软土地坪复合地基的处理效果,其中沉降控制是影响地坪安全运行的关键。以近海软土地区工业厂房水泥土搅拌桩复合地基工程为例,探讨了复合地基水泥土搅拌桩、回填土两种不同施工顺序的影响因素及相应处理效果;通过数值模拟试验,计算分析了不同填土厚度下两种工况的地基固结总沉降、施工沉降、工后沉降。结果表明,采用“先土后桩”的施工顺序的施工期沉降大于“先桩后土”,但工后沉降大大减小,提高了软土地坪地基处理效果,有利于处理后地坪的安全运行,验证了前述分析结论,为合理设计方案的确定提供了重要的参考依据。     

亚洲大陆地壳厚度分布轮廓及地壳构造特征的探讨

应用亚洲大陆地区的1°×1°平均布格重力场的数据,选择了均质单层地壳模型,对131条重力剖面的10456个重力点计算确定其莫霍界面深度,得到了亚洲大陆部分的地壳厚度分布轮廓图。 并对亚洲大陆的地壳构造轮廓作了分析与探讨,指出了四点构造特征     

饱和软土压缩曲线的“反常”现象

饱和软土压缩试验时,经常出现压缩曲线“反常”、压缩系数“倒大”的现象。它是土的原始结构发生破坏前后的不同压缩性的客观反映。饱和软土的结构力很微弱,唯质量好的原状土才能见到这种“反常”。应从成孔、取样、测试及资料整理等多个环节保证其工程意义。     

Possibility of degradation of phenylarsonic acid in the presence of ferrihydrite

Although inorganic species are predominant in natural systems, but there are many kinds of organoarsenic species such as methylated and phenylated arsenic compounds. Phenylarsonic acid （PA） is a degradation product of organoarsenics used for chemical warfare agents, which has been detected in well water at the disposal site of the agents in Japan. There are few reports studying behavior of PA in soil. In this study, PA was adsorbed onto ferrihydrite and its chemical forms were determined using high performance liquid chromatography connected to inductivity-coupled plasma mass spectrometry （HPLC-ICP-MS）. 100 mg/kg of PA was mixed with 0.03 g of 2-line ferrihydrite. For each suspension, pH was adjusted by HNO3 or NaOH. Each sample was incubated for more than 19 hours and the final pH was measured. After filtration, the chemical form of arsenic in the filtrate was measured using HPLC-ICP-MS. In addition, ferrihydrite separated by filtration was dissolved by 3 ml of 0.5 M HCI and the arsenic species in the solution was detected by HPLC-ICP-MS （column： Tosoh TSKgel SuperlC-AP, eluent： 0.01 M HNO3）. It was verified that PA is not degraded by heating in 0.5 M HCl solution. At pH 3.1, any arsenic compounds were not detected from the solution, because almost all arsenic species were adsorbed onto ferrihydrite at lower pH. At pH= 12, however, 7%-10% of inorganic arsenic was detected in the solution. In solid phase, there are some problems to determine the precise ratio of inorganic and organic species. When the solution includes Fe ion at 0.01 M level, the retention time of arsenic species drifted compared to those in standard solution, which makes it difficult to determine precisely the arsenic species adsorbed on ferrihydrite. Therefore, more study is needed to determine the ratio of inorganic and organic species in the system.     

土方超挖对土钉墙基坑支护安全性的影响分析

结合某基坑支护工程实例，分析了土方超挖对土钉墙基坑支护稳定性的不利影响。     

土钉墙与预应力锚杆联合支护技术

北京市深基坑工程中土钉墙支护技术应用比较广泛，对于边坡变形要求严格的基坑，采用土钉墙与预应力锚杆联合支护技术可有效控制变形，结合工程实例，介绍了该技术的设计思路及应用过程，说明了该技术的适用性，并就施工中遇到的问题进行分析，给出相应的处理措施。     

复合土钉墙支护技术在某大型软土基坑围护中的应用

根据拟建建筑基坑的工程地质条件、周边环境条件、基坑开挖深度等特点综合考虑，对基坑分段采用超前微型桩支护加土钉墙、放坡加土钉墙2种复合支护方案。实践证明，该工程所采用的多种复合式支护实施方案，技术安全可靠，经济合理。     

Natural siliceous dust and human health： Pathways, toxicity, and impact

Fine atmospheric dust includes mineral particles and aggregates, fibrous minerals and fibrous organic material. Generation, dislodgement and transport （deflation） of natural dust with the finer （〈4 microns） components suspended as silt-size aggregates, is widespread in and adjacent to the world＇s drylands, as well as deriving from volcanic vents. Silica is a highly fibrogenic agent in lung tissue. Long-term inhaling of siliceous dusts can lead to a number of fibrotic lung diseases, including natural （non-occupational） pneumoconioses （notably silicosis, but including asbestosis and others）. Different polymorphs of silica show different levels of toxicity in interaction with lung tissue. Particles with highly active surfaces may release radicals, causing cell damage. Some types of inhaled particulates are degraded by macrophages, but many are highly resistant and persist in the lungs, some stimulating fibroblastic cells to deposit collagen. Silicosis is an inflammation of the lung commonly caused by silicate mineral particles, leading to fibrosis. Three types are recognized： nodular pulmonary fibrosis （simple or chronic silicosis）, acute silicosis, and accelerated silicosis. Generally, finer particulates have greater oxidative capacity than the coarser fractions. They contain more reactive oxygen species, their greater bioreactivity making them more toxic to pulmonary tissue. Nevertheless, inhalation of large dust particles （〉 10μm） may constitute a health risk if the mineralogy is toxic, regardless of where the grains lodge in the respiratory system. Dust may absorb harmful gases, disease-generating bacteria and carcinogenic hydrocarbon compounds. Silica-related respiratory disease may also an exacerbate cardiac problem, and epidemiology suggests a link with tuberculosis. Quantification of dust loading and exposure requires study of spatial and temporal patterns, supported by meteorological analysis, airflow modeling and satellite-borne imagery. Some acute, short-term health impacts have been assessed using atmospheric and health records both before and after a dust storm or by comparison of populations within and outside such events. Analysis of the size, shape, mineralogy and geochemistry of ambient dust particulates provides information on natural dust sources, dust concentrations, and potential particulate toxicity, as well as providing a datum for assessment of human exposure levels.     

湿地生态系统碳循环过程及碳动态模型

从地上、地下有机物质生产对湿地碳输入的贡献,湿地土壤碳库以及土地利用变化对湿地土壤碳库和碳排放的影响,甲烷排放和可溶性有机碳输出以及影响因子,湿地生态系统碳循环动态模型4个方面对湿地生态系统碳循环国内外研究进展和研究成果进行综述、分析,提出了我国亚热带区域天然湿地碳循环研究的主要热点和方向:⑴沿海湿地碳库估算及土地利用转化对土壤碳库和温室气体排放的影响;⑵酸沉降对于我国东南沿海低纬度地区湿地甲烷排放的影响;⑶沿海湿地生态系统碳循环动态模型的应用与开发;⑷湿地系统可溶性有机碳的输出机理探讨.