工艺参数对页岩砖表面氡析出率的影响

采用活性炭坌法吸附页岩样品砖（在不同工艺参数条件下制备）表面析出的氧气,运用高纯锗探测器测量氡子体214Pb特征峰射线的计数．得出页岩样品砖表面氡析出率。通过比较,分析出不同工艺参数（煤矸石的含量、负压、焙烧温度）对页岩砖表面氡析出率的影响。     

聚合物对透水性混凝土性能的影响研究

研究了不同水灰比和聚合物掺量对透水性混凝土的强度、抗冻性、透水系数的影响,结果表明,透水性混凝土存在最佳水灰比;同时聚合物的加入,可显著提高透水性混凝土的抗折强度、抗压强度以及抗冻性能,但对透水系数的影响较小。     

土体参数对支护桩水平位移的影响分析

随着我国经济的快速发展,房屋建筑体积和高度都在不断增加,深基坑工程采用排桩支护或者是桩锚支护的也越来越多,结合实际工程,重点分析了影响桩体水平位移的几个重要因素,分别是土体的弹性模量、重度和内摩擦角,通过分析可知,桩体水平位移随着土体弹性模量的增加而减小,随着重度增加而增加,且影响较明显,随着内摩擦角增大而减小。这些分析为以后的工程设计提供了参考,有着重要的现实意义。     

Seasonal variations in soil gas radon concentration

We have been studying seasonal variations in soil gas radon concentration in southern Finland since 1982.To detect the radon we employ liquid scintillation solution in an open glass vial placed in a plastic tube set in a hole drilled in the ground.The results from an esker area show that there may be an appreciable seasonal variation in soil gas radon concentration, similar to that in houses. Because of the varying permeability and radium concentration of the ground, small changes in the building may have a large impact.     

土质路基双块式无砟轨道参数影响分析

针对土质路基双块式无砟轨道结构,建立了双块式无砟轨道整体有限元模型,研究了主要参数变化对无砟轨道受力的影响,确定了无砟轨道设计参数,从而确保无砟轨道结构设计的安全性、经济性。     

电子氡检测仪测定土壤中氡浓度方法的研究

本文使用RAD-7型电子氡检测仪测定土壤中氡浓度,提出了防止检测系统漏气的措施,优化了仪器运行的各种参数,建立了自动化检测系统,是一种快速、准确、简便的测定土壤中氡浓度的方法。     

Settlement trough parameters for tunnels in Irish glacial tills

Glacial till (or boulder clay) is the most widespread sediment on the island of Ireland. The behaviour of these tills, especially Dublin Boulder Clay, is now better understood as a result of ground investigations and associated testing for major construction projects, particularly in the east of the country over the past decade. Despite an increase in tunnelling activity in the country over the same time period, there is very little documented evidence on the settlements induced by tunnelling operations in glacial till. In this paper, transverse surface settlement data from two glacial till sites are presented. Four profiles are presented for the ‘soft ground’ TBM-bored section of the Dublin Port Tunnel. Nine profiles are reported for pipe-jacked microtunnels constructed for a sewerage scheme in Mullingar in the Midlands; one of which was measured at the top of a railway embankment under which the pipeline passes. The measured settlements have been interpreted using a standard Gaussian error function, and trough width parameters show dependence on the fraction of the till, fine or coarse, that governs its behaviour. In addition, conservative design estimates of maximum trough settlement and volume loss have been provided, and the impact of boulders is discussed. This paper provides the first empirical guidance for predicting surface settlements above tunnels in Irish soils.     

The influence of pH on phosphate release from lake sediments

pH is believed to be an important regulating factor for the release of phosphate from freshwater sediments. Usually, this is demonstrated in laboratory experiments using intact sediment cores and pH regulation of the overlying water by means of NaOH additions. This technique and a pH regulation technique by means of CO₂-stripping were compared. The first method resulted in a 10-fold increase in release rate at pH 9.5 compared to the rate at pH 8.3. The stripping technique yielded only a doubling of the release rate at pH 9.3. Measurements of pH profiles in the sediment in experiments performed at pH 8.3 and 9.0 proved that the enhanced phosphate release when using NaOH for pH regulation is mainly an artifact caused by an increased alkalinity in the water column and the upper sediment layers, resulting from the NaOH additions.     

渗透型涂料表面防护对钢筋锈蚀的影响

采用半电池电位法研究了持续氯盐侵蚀和干湿循环条件下,不同水灰比、表面防护与未防护混凝土中钢筋锈蚀的发展规律.结果表明,当水灰比从0.4增大到0.6,混凝土内钢筋的锈蚀速率增大了约2倍;水灰比相同时,应用硅烷防水剂进行表面防护,混凝土的锈蚀速率明显小于未防护混凝土,且表面防护对于已出现钢筋锈蚀的混凝土依然有效.因此,表面防护是提高和改善新建及既有混凝土结构耐久性的有效措施.     

The influence of soil remediation on lead in house dust

Lead in house dust has long been recognized as a principal source of excess lead absorption among children at the Bunker Hill Superfund Site (BHSS) in northern Idaho. House dust lead concentration from homeowner's vacuum cleaner bags has been monitored since the epidemic of childhood lead poisoning in 1974. Geometric mean house dust lead concentrations decreased from >10000 mg/kg in 1974 to approximately 4000 mg/kg in 1975, in response to air pollution control initiatives at the defective primary lead smelter. After smelter closure, 1983 mean dust lead concentrations were near 3000 mg/kg and were most dependent on soil sources. Following emergency soil removals from public areas and roadsides and fugitive dust control efforts in the mid-1980s, house dust lead decreased by approximately 40-60% to 1200-1500 mg/kg. In 1992, a cleanup goal of 500 mg/kg dust lead community average, with no individual home exceeding 1000 mg/kg, was adopted. This goal was to be achieved by a combination of contaminated soil removals and fugitive dust control efforts throughout the 21 square mile BHSS. Continual reductions in house dust lead concentrations have been noted throughout the residential area soil cleanup. Geometric mean house dust lead concentrations averaged approximately 500-600 mg/kg from 1996 to 1999 and dropped below 500 mg/kg in 2000. Analysis of these data indicates that approximately 20% of the variance in dust lead concentrations is attributed to yard, neighborhood, and community soil lead concentrations. Since 1996, dust lead concentrations and dust and lead loading rates have also been measured by dust mats placed at entryways into the homes. Neighborhood soil lead concentrations, household hygiene, the number of adults living in the home, and the number of hours a child spends outdoors in summer explain approximately 26% of the variance in mat dust lead loading rates. It is estimated that post-remedial house dust lead concentrations will stabilize at 400-500 mg/kg, as compared to approximately 200 mg/kg in socio-economically similar background communities; the difference possibly attributed to residual soil concentrations (3-6 times background), recontamination of rights-of-way, tracking of non-residential mining district soils and dusts, fugitive dusts associated with the remediation, and residual structural or carpet dusts.     

降雨入渗对震后边坡岩土力学参数影响

通过对震后重灾区平通镇牛斐村大咀山山坡土样进行直接剪切试验,探讨了降雨对山坡土体的抗剪强度影响因素,并对正交试验结果进行了分析,得出了一些有益的结论。     

天津地区地基土中氡含量的初步调查

在天津市域内选择适宜地点实地测量,从目前仅有的30余点实测资料统计,天津市土壤氡的平均浓度为8 572 Bq/m3。根据氡及其短寿命子体的形成、衰变、运移、富集规律以及实测结果得出,天津市域内的断裂经过地带以及凹陷地区,如蓟县、宁河、宝坻、武清、汉沽、市区及塘沽的海河沿线地区,氡浓度较高。     

原始气象数据对建筑设计室外计算参数的影响

根据暖通规范的室外空气计算参数的确定方法,对1971年~2000年的原始气象资料进行了统计计算,将得出的室外空气计算参数与暖通规范中的室外空气计算参数进行了比较分析,结果表明室外空气计算参数总体呈上升趋势。     

The occurrence of methane in recent deltaic sediments and its effect on soil stability

Summary River-mouth depositional pattern are modified by sediment-deforming processes of sufficient magnitude to severely endanger bottom-supported structures. Several types of deformations are present, including (a) peripheral slumping, (b) differential weighting and diapirism, (c) radial tensional faulting, (d) mass wasting and flowage induced by wave motion and degassing, and (e) deepseated clay flowage. The processes of bacterial methane production and the resulting effects on sediment deformation have been investigated in four cores taken in the Recent deltaic sediments of the Mississippi River. Dissolved methane in the interstitial waters ranged in concentration from 2 × 10⁻³ to 1.7 ml/l, whereas total CH₄ (dissolved plus bubble phase) ranged from 5 × 10⁻³ to over 300 ml 1. High concentrations of methane corresponded to zones of low shear strength and were observed where dissolved sulfate was depleted. Calculations of maximum in situ methane concentrations, based on chemical reduction of excess total CO₂, indicate that methane could be present above saturation levels (bubble phase). Classical anaerobic geochemical gradients were observed in sediment profiles where no movement had previously occurred. The pore water geochemistry of sediment profiles within peripheral mudflows suggest that coexistence of methane and sulfate indicate convective mixing of sediments and bottom seawater. Calculations using the equilibrium slopes of wave-induced mudflows indicate that shear strengths during movement must be less than the values measured before or after the flow. An improved model of mass movement is presented which relates the physical and geochemical properties of unstable sediments.

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La Présence De Méthane Dans Des Sédiments Deltaiques Récents Et Son Influence Sur La Stabilité Du Sol

Résumé Les structures des sédiments à l’embouchure d’un fleuve sont modifiées par des processus déformateurs d’une ampleur suffisante pour mettre gravement en danger les constructions qui s’appuient sur le fond. On peut distinguer plusieurs types de déformations: a) enfoncement périphérique; b) tassement irrégulier et diapirisme; c) formation de failles de tension rayonnantes; d) perte de masse et écoulement provoqués par le mouvement des vagues et le dégazage; et e) écoulement d’argiles profondes. Les processus de production du méthane par les bactéries et leurs conséquences sur la déformation des sédiments ont été étudies sur quatre carottes prélevées dans les sédiments delta?ques récents du Mississipi. Les concentrations de méthane dissous dans les eaux intersticielles sont comprises entre 0,002 et 1,7 ml/l, cependant que le méthane total (bulles et gaz dissous) est compris entre 0,005 et plus de 300 ml/l. Les fortes concentrations en méthane correspondent aux zones de faible résistance au cisaillement; elles s’observent aux endroits où le sulfate dissous est épuisé. Les calculs de concentrations maximales de méthane in situ, basés sur la réduction chimique du CO₂ total en excès, montrent que le méthane pourrait être présent au-dessus des niveaux de saturation (phase bulles). Les gradients géochimiques anaérobiques classiques furent observés sur des profils sédimentaires où aucun mouvement n’était apparu précédemment. La géochimie des eaux intersticielles des profils sedimentaires des coulées de boues périphériques permet de supposer que la coexistence de méthane et de sulfate indique un mélange de sédiments et d’eau du fond de la mer, par convexion. Les calculs utilisant les profils d’équilibre de coulées de boues produites par les vagues montrent que la résistance au cisaillement pendant le mouvement peut être moindre qu’avant ou après l’écoulement. On présente un modéle amélioré de mouvement de masse, tenant compte des propriétés physiques et géochimique des sédiments instables.

     

Radon and radon daughter levels in energy efficient housing

radon and radon daughter concentrations have been measured in 33 “energy-efficient” homes in a small subdivision in Kanata, Ontario. Integrated radon measurements were determined over three month periods for a year using solid state nuclear track detectors. Radon and radon daughter grab sample determinations were made during corresponding periods and confirm the distributions of the integrated radon measurements.Annual average individual home radon concentrations show an 8 fold concentration range between homes. This variability in radon concentrations is not reflected in the range of air exchange rates for the homes. A distinct seasonal variation is noted for the median values of the radon and radon daughter concentrations and the equilibrium factor F in the dwellings.     

重力式加筋土挡墙设计参数的影响分析

重力式加筋土挡墙是将传统重力挡墙和普通加筋土挡墙相结合的一种新型挡墙。采用FLAC程序,模拟先浇筑重力挡墙,后填筑墙后加筋土的施工顺序,在已完成一个典型重力式加筋土挡墙从墙后填土到墙顶和墙顶堆载完成以后两个阶段数值模拟,掌握其工作性状的基础上,进一步对重力挡墙刚度、墙后填土性质、加筋土工格栅性质、加筋长度和间距等主要影响因素进行数值模拟分析,为设计参数的合理选择提供依据。     

工艺参数对陶瓷透水砖性能影响的研究

采用煤渣、废瓷粒等工业废渣为骨料,以石灰石、白云石、长石、高岭土、石英和瓷石粉的混合料为高温粘结剂制备陶瓷透水砖,研究工艺参数对透水砖性能的影响。结果表明,随着煤渣用量的增加或成型压力的降低,透水砖的透水性能提高而机械强度降低。通过DTA-TG分析确定了在800℃保温4 h的优化烧成制度,有效避免了黑心和变形缺陷的产生。FE-SEM显微照片表明,合理的煤渣颗粒级配能使煤渣粗颗粒间形成孔径为0.5～1.5 mm的大气孔,而煤渣颗粒本身由于其中可燃物燃烧形成了孔径为数十个微米的微孔,这种特殊的结构赋予透水砖强度高、透水好的性能。     

核电厂暖通设计中室外气象参数的选用

我国核电厂暖通设计中室外气象参数的选用长期处于不规范状态,核岛一般按照美国规范选用,常规岛及BOP按照我国规范选用,其中存在着矛盾。通过比较分析两国规范,针对实例分别统计计算,并对统计结果分析比较,最终确定按照我国规范取用的气象参数更保守,因此建议后续的核电厂暖通设计中气象参数应统一按照我国规范选用。     

基于气象参数的混凝土结构日照温度作用分析

气象参数是分析日照环境下混凝土结构温度作用的关键参数之一。影响日照环境下混凝土结构温度场的气象参数主要有太阳辐射、气温和风速。本文分析了这些气象参数变化的一般规律,提出其时程分析模型,并从概率统计的角度分析了这些参数的分布规律,确定了具有一定重现期的气象参数代表值。最后以一个混凝土箱梁为例,利用这些气象参数代表值计算分析了其日照温度场,并根据计算温度场拟合得到竖向温差分布曲线。计算表明,分析日照环境下混凝土结构温度场时应考虑气象参数的随机分布。