Chemical degradation characteristics of reinforced concrete reefs in South Korea

The chemical degradation characteristics of reinforced concrete reefs, which had been fully immersed in Tongyeong waters of South Korea for 18–25 years, were studied. In order to investigate the marine environmental impact on the concrete reefs, environmental factors, for example pH, have been observed between 1997 and 2002. Then, four reinforced concrete reefs recovered from different sites in Tongyeong waters were nondestructively tested. Finally, those test results were analyzed to determine the chemical deterioration. Based on the test results, it is shown that the reinforced concrete reefs have sound chemical properties and their originally estimated service life is secure enough for a further service period in water depths of 28–32 m. A concrete cover depth of 40 mm is recommended for the design of reinforced concrete reefs to achieve safety in marine environments and special events occurring during installation and construction.     

Bearing capacity tests of strip footings on reinforced layered soil

The ultimate bearing capacity of strip footings resting on subsoil consisting of a strong sand layer (reinforced/unreinforced) overlying a low bearing capacity sand deposit has been investigated. Three principal problems were analysed based on results obtained from the model tests as follows: (1) the effect of stratified subsoil on the foundations bearing capacity; (2) the effect of reinforcing the top layer with horizontal layers of geogrid reinforcement on the bearing capacity; (3) effect of reinforcing stratified subsoil (reinforced and unreinforced) on the settlement of the foundation. It has been observed that reinforcing the subsoil after replacing the top layer of soil with a well-graded soil is beneficial as the mobilization of soil-reinforcement frictional resistance will increase.     

两种抗差估计在陀螺信号处理中的比较

捷联寻北仪中影响寻北精度的主要因素是陀螺随机漂移.由于陀螺信号中不可避免地存在异常观测或粗差,陀螺随机漂移中包含异常噪声(异常数据).抗差估计通过连续降权和连续减弱影响的方法抵制异常数据,是一种控制异常数据的有效方法.本文给出了两种抗差估计解及其相应原则,利用一个实际算例比较了两种抗差估计控制异常数据影响的能力.计算结...     

Monitoring crack development in fiber concrete beam by using electrical resistivity imaging

Accurate detection of damaged concrete zones plays an important role in selecting the proper remedial technique. This study presents results from an application of the electrical imaging method to monitor the development of cracks in fiber concrete beams.The study showed that resistivity measurements on the concrete specimens were able to detect the increase of concrete resistivity with the curing time that reached about 65 Ωm after 28 days of curing. A similar development trend of concrete compressive strength was also found.Two types of cracks were investigated, i.e., artificial cracks made of plastic sheets inserted in concrete and cracks developed during a four-step loading test. A mini-electric imaging survey with Wenner array was conducted on the tension face of the beams. To deal with the effect of the beam size new procedures to correct resistivity measurements before inversion were proposed and successfully applied in this study. The results indicated that both crack direction and depth could be accurately determined in the inverted resistivity sections.     

Monitoring and warning of landslides and debris flows using an optical fiber sensor technology

Landslides and debris flows are typical geo-hazards which occur in hilly or mountainous regions. Debris flows may result from landslides. Geotechnical instrumentation plays an important role in monitoring and warning of landslides and resulted debris flows. Traditional technologies for monitoring landslides and debris flows have certain limitations. The new optical fiber sensors presented in this paper can overcome those limitations. This paper presents two new optical fiber sensor systems: one is the Fiber Bragg Grating (FBG)-based in-place inclinometer for monitoring landslides and the other is the FBG-based column-net system for monitoring debris flows. This paper presents the calibration results of FBG-based in-place inclinometers in laboratory. It is found that the calibration results are in good agreement with theoretical results. Both the FBG-based in-place inclinometers and the FBG-based column-net system have been installed at a site in Weijiagou valley, Beichuan County, Sichuan Province of China. Some preliminary results have been obtained and reported in the paper. The advantages of the FBG monitoring systems and their potential applications are also presented.     

不锈钢内衬技术在江阴市供水管网改造中的应用

本文结合不锈钢内衬技术在江阴市玻璃钢供水管道改造中的应用,介绍了不锈钢内衬玻璃钢管施工工艺流程和施工技术措施,分析了不锈钢内衬施工效果和优势。展望了不锈钢内衬技术在城市供水管网改造中的应用前景。     

Use of principal component analysis for identification of Rockland and Trego Hot Springs tephras in the Hat Creek Graben,northeastern California,USA

Discontinuous tephra layers were discovered at Burney Spring Mountain, northern California. Stratigraphic relationships suggest that they are two distinct tephras. Binary plots and standard similarity coefficients of electron probe microanalysis data have been supplemented with principal component analysis to correlate the two tephra layers to known regional tephras. Using principal component analysis, we are furthermore able to bound our uncertainty in the correlation of the two tephra layers. After removal of outliers, within the 95% prediction interval, we can say that one tephra layer is likely the Rockland tephra, aged 565–610 ka, and the second layer is likely from Mt. Mazama, the Trego Hot Springs tephra, aged ~ 29 ka. In the case of the Rockland tephra, the new findings suggest that dispersal to the north was highly restricted. For Trego Hot Springs ash, the new findings extend the distribution to the southwest, with a rapid thinning in that direction. Coupled with considerations of regular tephra dispersal patterns, the results suggest that the primary dispersal direction for both tephras was to the south, and that occurrences in other directions are unlikely or otherwise anomalous.     

Characterization of tephras dispersed by the recent eruptions of volcanoes Calbuco (1961), Chaitén (2008) and Cordón Caulle Complex (1960 and 2011), in Northern Patagonia

Pyroclastic materials dispersed in recent volcanic eruptions in Northern Patagonia were analysed in order to characterize the volcanic provenance by the geochemical fingerprint. The volcanic products studied were dispersed by eruptions of volcanoes Calbuco in 1961, Chaitén in 2008, and Cordón Caulle Volcanic Complex (CCVC) in 1960 and 2011. The geochemical characterization was based on the determination of 35 major and trace elements by Instrumental Neutron Activation Analysis, including geochemical tracer such as Rare Earth Elements (REE). The study of the pyroclastic products also included the morphological analysis by petrographic and scanning electron microscopy, and the mineralogical characterization by X-ray diffraction.Geochemical tracers determined in the glass fraction of the dispersed pyroclastic materials allowed a clear discrimination of the three volcanoes that gave origin to the tephras, the three of them with different evolution degree. Tephras from 1960 and 2011 CCVC eruptions showed the same geochemical signature. The geochemical parameters providing the differential characterization are the normalized REE and multi-element patterns, the Eu anomaly, the heavy to light and medium to light REE normalized ratios, and the Cs, Sc, Rb, Ta and Th concentrations. The bulk glassy fraction showed the same composition for each volcanic eruption in samples collected even in distant sites (from 100 to 220 km in Chaitén, 2008, and from 80 to 650 km in CCVC 2011), attesting to be the most reliable material for correlation purposes.According to the mineralogy, cristobalite was found in volcano Chaitén tephra as an indicator of such origin. Arsenic, an element of environmental interest, exhibited concentrations ranging from 6 to 16 μg g⁻¹, with the highest values corresponding to Puyehue–Cordón Caulle and Chaitén products.     

Li2S—B2O3体系玻璃的形成及其稳定性研究

本要用情性气体保护下的高温熔融反应及液氮淬冷技术制备了Li_2S-B_2O_3体系玻璃。采用XRD、ICP及化学滴定法分别确定了产物的形态和化学组成。利用DTA星热法测定了玻璃的转变温度Tg、晶化温度Tc及晶化峰值温度Tp，并根据Tg、Tc-Tg、Tp－Tg、（Tp－Tg）／Tg四种玻璃稳定性判据讨论了Li2S-B2O3玻璃的相对稳定性。实验表明，Li2S-B2O3体系能在Li2S的摩尔分数X≤0．45的浓度范围形成玻璃，且在x=0．25附近玻璃的稳定性最强。     

材料表面性质对微生物附着行为的影响

利用荧光显微镜计数法,研究了微生物在4种不同材料表面的初始附着行为,对微生物附着进行了定量描述,初步获得以下结果:(1)不同材料表面,细菌的附着量呈现如下差异:316L不锈钢＞PVC＞玻璃,在有机硅材料(道康宁T2)表面的附着变动性很大;(2)同种材料表面,不同细菌的附着量也不同,表现为:Shewanella oneidensis MR-1菌株和Pseudomonas aeruginosa PAO1菌株均大于Escherichia coli JM 109菌株.并由此对其附着差异和影响因素进行了讨论.