砂泥岩地基大直径灌注桩竖向承载力试验研究

以某电厂桩基础为工程依托,进行了两试桩竖向静载荷试验,探讨了砂泥岩地基大直径灌注桩的荷载传递机理和竖向承载特性。试验结果表明,砂泥岩地基大直径灌注桩在极限荷载作用达到稳定的情况下,荷载由桩侧阻力与桩端阻力共同承担,但表现出很强的摩擦桩特征,桩侧阻力的发挥取决于桩土相对位移,对于不同的土层,桩侧摩阻力达到极限时所对应的桩土之间相对位移不尽相同。针对试验结果,根据上部结构对基础沉降的要求,以桩顶沉降量来控制桩的竖向承载力,并提出了简化的计算公式,该公式考虑了桩土相对位移对桩侧阻力发挥的影响。     

Application of semipermeable membrane device (SPMD) to assess air genotoxicity in an occupational environment

Semipermeable membrane device (SPMD) is a passive sampler that sequesters lipophilic contaminants, mimicking the bioconcentration in the fatty tissue of organisms. This study was designed to assess the use of SPMD and biological tests (Comet assay and Ames test) for air monitoring. For this purpose an occupational environment with expected polycyclic aromatic hydrocarbons (PAHs) contamination (coke plant) was selected for a case study. The SPMDs were deployed in five occupational contaminated sites and in a control site. The SPMD dialysates were chemically analysed and examined for in vitro DNA-damaging activity in human cells (Jurkat) by Comet assay and for mutagenicity with the Ames test (TA98 strain, w/o S9). Total suspended particulates were also collected and analysed (GC–MS). No biological effect of SPMD extract was revealed in the control site. On the other hand, air samples collected with SPMDs within the coke plant showed variable degrees of genotoxic and mutagenic activity. The highest effects were associated with the highest PAH level recovered in the SPMDs extracts and in particulate samples.Results obtained support the sensitivity of biological tests associated to SPMD sampling for evaluating the health risk of potentially contaminated work environments highlighting the usefulness of SPMDs for environmental air quality monitoring.     

不同流向BAF硝化影响因素的对比试验

在温度、水力负荷、气水比、氨氮负荷、有机物负荷等硝化影响因素同等变化的情况下,进行了不同流向单级陶粒BAF硝化效果的对比试验研究。结果表明,UBAF的硝化效果和稳定性优于DBAF。若在同一反应器中同时去除有机物和氨氮,UBAF的经济气水比为3∶1～6∶1,DBAF的经济气水比为3∶1～5∶1。当进水有机物负荷<11 kg/(m³·d),有机物和氨氮的负荷比<5时,UBAF和DBAF的氨氮去除率相差不大。在较高COD浓度下,硝化菌在DBAF中与异氧菌的竞争能力不如UBAF。两级BAF的第一级宜为UBAF,但DBAF可能更适于作为二级滤池以提高系统稳定性、反硝化效率以及出水水质。     

斜井送排式通风隧道的火灾救援通风研究

公路隧道发生火灾开启横通道后,形成通风网络。本文以重庆地区吕家梁隧道为工程依托,进行了斜井前后不同位置发生火灾的通风网络模拟。结果表明,斜井前发生火灾时,受斜井浮力效应、风流密度变化等的影响,主风机的工作压力降低,而体积流量增加;当火灾发生在斜井前隧道时,采用斜井单抽方式可实现全部火灾烟流从竖井中排除,斜井前设射流风机增压调节、斜井后设射流风机增阻调节是一较好方案;对于斜井后发生火灾,采用全射流火灾通风和斜井压入两种通风方案均能满足火灾风流控制要求,虽然后者需要开启轴流风机,通风能耗大,但火灾通风的时效性要好于前者。     

哑铃桩模型试验与承载力计算方法研究

对自主研发的哑铃桩进行了系列试验和理论分析。通过与不同截面形式的桩进行承载性能试验对比,分析了存在顶盘、扩头情况下的哑铃桩与传统单桩等桩型在不同外力荷载作用下的承载力差异,及其与桩端受力、荷载沉降等的关系。研究表明,本文模型试验中,周围填土是砂的条件下,哑铃桩桩端阻力分担了绝大部分的桩顶荷载,可把哑铃桩视作端承桩进行设计,其承载力较之其它桩型显著提高,且在达到桩基极限承载力时,其所对应的桩顶沉降较之普通预制桩明显减小。此外,还针对哑铃桩的构造特点提出了哑铃桩承载力计算公式,并通过与试验数据的对比,验证了其合理性。     

固结时间对软粘土动剪切模量的影响

随着固结时间的增加,试样逐渐变硬的硬化效应使软粘土的动剪切模量增大;同时,随着固结时间的增加,试样高度和直径明显减小的尺寸效应,也使软粘土的动剪切模量受到显著的影响。通过软粘土自振柱试验,分析了固结时间对软粘土的最大动剪切模量、动剪切模量比和试样尺寸的影响;根据自振柱试验的基本原理,分析了试样尺寸的变化对软粘土动剪切模量的影响;结合试验得到的固结时间和试样尺寸的关系,分析了固结时间通过试样尺寸对软粘土动剪切模量的影响。     

高速公路连拱隧道开挖三维稳定性分析

通过对金丽温高速公路湾连拱隧道工程区的地质特征的详细分析和现场调查,系统研究了湾隧道开挖及加固全过程的围岩应力场、变形场的状况及变化特征。结果表明,湾连拱隧道围岩应变率较高,围岩衬砌后的位移值比未衬砌时减小了50%,采用目前的衬砌类型后,衬砌变形将较大幅度地变小,衬砌应变值基本满足要求;虽然围岩拉应力值随着隧道的开挖逐渐变大,除局部位置外,衬砌整体基本满足抗拉的要求。     

紫下大桥安全检测与评价方法研究

钢桥因具有跨径大、承载能力强、施工工期短等特点,被世界各国广泛采用,但在使用过程中,由于重载甚至超载车辆的反复作用、自然灾害的侵袭及交通事故等人为因素的作用,经常造成桥梁损伤和局部破坏,导致桥梁承载能力和耐久性的降低,甚至影响到运营的安全。本文建立了钢拱桥的健康检测和安全评价方法,采用防腐涂层厚度测定、结合强度测定、无损探伤和动静载荷试验等手段对紫下大桥健康状况进行了检测,采用不确定层次分析法对大桥进行了安全评价,提出了处理意见和措施,为既有钢拱桥的健康检测、评价和维护积累了有益的资料。     

中国农业面源污染与经济发展关系的实证研究

把握现阶段我国经济发展过程中农业面源污染压力的演变规律,是制定农业可持续发展政策的基本依据。运用1998~2006年我国31个省（市、自治区）面板数据模型对经济发展与农业面源污染的环境库兹涅茨曲线(EKC)关系进行实证研究。选取各省化肥投入密度、农药投入密度、畜禽粪尿排泄物密度作为度量农业面污染源排放量的指标,选取各省人均国民生产总值作为经济发展衡量指标。研究结果表明,我国农业面源污染源排放量与经济增长总体上具有显著的倒“U”型曲线关系,三类污染源与人均GDP均处于曲线上升阶段,自发到达农业面源污染减排拐点还需较长时间。政府应强化农业环境政策的干预力度,加大对农业面源污染的治理力度。     

A wind tunnel study of the effect of roadway configurations on the dispersion of traffic-related pollution

In this paper we examine the effect of different roadway configurations, including noise barriers and roadway elevation or depression relative to the surrounding terrain, on the dispersion of traffic-related pollutants for winds perpendicular to the roadway. A wind tunnel experiment modeling 12 different configurations was performed to study the flow fields and the concentration distributions resulting from emissions from a simulated six-lane highway. All of the configurations examined here reduced the downwind ground-level concentrations relative to that for a flat, unobstructed roadway; however, the degree to which the concentrations were reduced varied widely depending on the particular situation.Ground-level concentration data from the cases considered in this research indicate that a constant entrainment velocity can be used over the region beginning downwind of any initial disturbance to the flow resulting from the roadway configuration (e.g., a recirculation region behind a noise barrier) and extending at least to the end of our measurements. For example, for the case of a single noise barrier on the downwind side of the road, this region extends from approximately four barrier heights downwind of the roadway to 40 barrier heights. It was also found that the virtual origin concept is useful in describing the initial mixing created by the particular roadway configuration. To effectively model the influence of the roadway configuration on the dispersion, a combination of a virtual origin and an entrainment velocity may be effective. The magnitude of the virtual origin shift appears to depend on the particular roadway configuration, while the entrainment velocity appears to be a function of the friction velocity and the roadway geometry. These results suggest that road configuration must be taken into account in modeling near-road air quality.