梅子凹大桥岩溶地质钻孔桩的施工技术

1工程概况随岳高速公路上的梅子凹大桥位于湖北省京山县,跨越梅子凹水库,桥长687.10 m,宽26 m,桥墩基础为钻孔灌注桩,桩直径1.5~1.8 m,桩长20 m~28 m;下部构造桥墩为双柱式墩(墩梁固结),桥台为肋板式台、扩大基础,墩柱直径为160~170cm,墩柱最高达32 m;上部构造为40 m跨径预应力     

Effect of underground urban structures on eutrophic coastal environment

The NIES Integrated Catchment-based Eco-hydrology (NICE) model was expanded to include the density current and solute-transport process of groundwater in the Kanto Plain and to incorporate the effects of water table and tidal fluctuations around the eutrophic Tokyo Bay, Japan (NICE-SEA). The simulation reproduced excellently the observed values of river discharge and groundwater level in the catchment. The simulated groundwater level shows a minus value (below the sea level) around the Tokyo metropolitan area because of excessive withdrawal around the urban area in the past. The model shows that the underground urban structures, sewage pipes, seashore concrete dikes, and embankments have changed the hydrologic cycle in the catchment and the nutrient supply to Tokyo Bay. In particular, the groundwater flow is interrupted and the phase is delayed, resulting in an increase in the groundwater level, and a decrease of groundwater seepage into Tokyo Bay. Furthermore, we propose four types of political scenario for provisioning human ecosystem service (ES) sites to promote infiltration. The simulated result forecasts that the groundwater level increases predominantly at a maximum value exceeding 40 cm in a scenario for farmland and productive green areas and that the level recovers in some parts of the urban area. This phenomenon is related to the cut-off of groundwater flow by underground urban structures and the sewer leakage into the aquifer, which also influences the decrease of submarine groundwater discharge around the western side of Tokyo Bay.     

特低渗透油藏裂缝分布规律研究

分析了特低渗透油藏裂缝研究存在的问题、目前的研究现状和发展趋势,分析并总结了渗透油藏裂缝研究的基本思路。认为特低渗透油藏裂缝研究理论应用前景广阔。     

基于灰色-马尔可夫理论的纳米复合陶瓷刀具磨损量预测

应用灰色系统理论和马尔可夫链预测理论建立了纳米复合陶瓷刀具磨损量的灰色-马尔可夫链预测模型,研究了刀具磨损量和刀具寿命的预测方法。AWT纳米复合陶瓷刀具的磨损量及刀具寿命预测结果表明,预测值与实测值误差较小。     

钢-混凝土粘结预测的人工神经网络模型

提出人工神经网络模型来模拟传统的带肋钢筋和混凝土之间的粘结性能,目的是预测钢筋从混凝土混合物中拔出的极限荷载(第一神经网络模型)或抗压强度(第二神经网络)以及根据RILEM试验设计的不同钢筋直径的拔出极限荷载。采用112个带肋钢筋(直径为10mm、12mm)以及三种不同混凝土配合比的拔出试验结果数据库,对神经网络模型进行训练。根据反向传播算法,进行多层感知器训练。第一个模型(ANN-6)有6个输入:钢筋直径、水灰比、砂石比、级配、水泥种类和混凝土龄期。第二个模型(ANN-2)有2个输入:钢筋直径、混凝土抗压强度,两个模型的输出均为极限拔出荷载。研究结果显示:所采用的模型预测精度高、误差低、具有鲁棒性。从鲁棒性方面,第一个模型(ANN-6)比第二个模型(ANN-2)更精确。将混凝土的成分作为输入参数,而不是混凝土的强度,对于带肋钢筋-混凝土界面的局部现象更具代表性。     

Conditions required for the stimulation of bioluminescence activity of the genetically engineered bacteria, P. putida mt-2 KG1206, preserved by deep-freezing

Herein the conditions required for the stimulation of bioluminescence activity in a genetically engineered strain of Pseudomonas putida mt-2 KG1206, containing the intact TOL plasmid and a constructed plasmid with the P_m-lux gene, are reported upon. Both sodium lactate (SL) and potassium nitrate (KNO₃) were able to stimulate the bioluminescence activity, but a greater increase was observed with nitrogen amendment. This selected stimulant was then tested on reconstituted cells that had been preserved by deep-freezing and mixed with pure inducer solution or groundwater samples. The stimulation of bioluminescence activities for deep-frozen strain was in the range of 101-238% of the control. The effect of KNO₃ was found to be dependent on the type of inducers used and the cell conditions. In general, high bioluminescence activity was observed with groundwater samples, contaminated with high inducer compounds. However, no significant correlation was observed between the bioluminescence intensity and the total inducer concentration in the environmental samples contaminated with complex mixtures with inducers.These results should be useful when other recombinant bioluminescence strains are to be used for environmental monitoring. Overall, the results of this study demonstrate the stimulant conditions for the bioluminescence activity of genetically engineered bacteria, and suggest the potential for preliminary application of this deep-frozen engineered strain in a field-ready bioassay to conveniently detect or monitor a specific group of environmental contaminants.     

Preparation and evaluation of iron–chitosan composites for removal of As(III) and As(V) from arsenic contaminated real life groundwater

A study on the removal of arsenic from real life groundwater using iron–chitosan composites is presented. Removal of arsenic(III) and arsenic(V) was studied through adsorption at pH 7.0 under equilibrium and dynamic conditions. The equilibrium data were fitted to Langmuir adsorption models and the various model parameters were evaluated. The monolayer adsorption capacity from the Langmuir model for iron chitosan flakes (ICF) (22.47 ± 0.56 mg/g for As(V) and 16.15 ± 0.32 mg/g for As(III)) was found to be considerably higher than that obtained for iron chitosan granules (ICB) (2.24 ± 0.04 mg/g for As(V); 2.32 ± 0.05 mg/g for As(III)). Anions including sulfate, phosphate and silicate at the levels present in groundwater did not cause serious interference in the adsorption behavior of arsenate/arsenite. The column regeneration studies were carried out for two sorption–desorption cycles for both As(III) and As(V) using ICF and ICB as sorbents. One hundred and forty-seven bed volumes of As(III) and 112 bed volumes of As(V) spiked groundwater were treated in column experiments using ICB, reducing arsenic concentration from 500 to <10 μg/l. The eluent used for the regeneration of the spent sorbent was 0.1 M NaOH. The adsorbent was also successfully applied for the removal of total inorganic arsenic down to <10 μg/l from real life arsenic contaminated groundwater samples.     

Geochemistry of redox-sensitive elements and sulfur isotopes in the high arsenic groundwater system of Datong Basin, China

High arsenic groundwater in the Quaternary aquifers of Datong Basin, northern China contain As up to 1820 µg/L and the high concentration plume is located in the slow flowing central parts of the basin. In this study we used hydrochemical data and sulfur isotope ratios of sulfate to better understand the conditions that are likely to control arsenic mobilization. Groundwater and spring samples were collected along two flow paths from the west and east margins of the basin and a third set along the basin flow path. Arsenic concentrations range from 68 to 670 µg/L in the basin and from 3.1 to 44 µg/L in the western and eastern margins. The margins have relatively oxidized waters with low contents of arsenic, relatively high proportions of As(V) among As species, and high contents of sulfate and uranium. By contrast, the central parts of the basin are reducing with high contents of arsenic in groundwater, commonly with high proportions of As(III) among As species, and low contents of sulfate and uranium. No statistical correlations were observed between arsenic and Eh, sulfate, Fe, Mn, Mo and U. While the mobility of sulfate, uranium and molybdenum is possibly controlled by the change in redox conditions as the groundwater flows towards central parts of the basin, the reducing conditions alone cannot account for the occurrence of high arsenic groundwater in the basin but it does explain the characteristics of arsenic speciation. With one exception, all the groundwaters with As(III) as the major As species have low Eh and those with As(V) have high Eh. Reductive dissolution of Fe-oxyhydroxides or reduction of As(V) are consistent with the observations, however no increase in dissolved Fe concentration was noted. Furthermore, water from the well with the highest arsenic was relatively oxidizing and contained mostly As(V). From previous work Fe-oxyhydroxides are speculated to exist as coatings rather than primary minerals.The wide range of δ³⁴S_[SO4] values (from − 2.5 to + 36.1‰) in the basin relative to the margins (from + 8‰ to + 15‰) indicate that sulfur is undergoing redox cycling. The highly enriched values point to sulfate reduction that was probably mediated by bacteria. The presence of monomethylarsonic acid (MMA) and dimethylarsinic acid (DMA) is also evidence of microbial reactions. The depleted signatures indicate that some oxidation of depleted sulfide occurred in the basin. It must be noted that the samples with depleted sulfur isotope values have very low sulfate concentrations and therefore even a small amount of sulfide oxidation will bias the ratio. No significant correlation was observed between δ³⁴S_[SO4] values and total arsenic contents when all the samples were considered. However, the wells in the central basin do appear to become enriched in δ³⁴S_[SO4] as arsenic concentration increases. Although there is evidence for sulfate reduction, it is clear that sulfate reduction does not co-precipitate or sequester arsenic. The one sample with high arsenic that is oxidizing cannot be explained by oxidation of pyrite and is likely an indication that there are multiple redox zones that control arsenic speciation but not necessarily its mobilization and contradict the possibility that Fe-oxyhydroxides sorb appreciable amounts of arsenic in this study area. It is evident that this basin like other two young sedimentary basins (Huhhot and Hetao in Inner Mongolia) of northern China with high arsenic groundwater is transporting arsenic at a very slow rate. The data are consistent with the possibility that the traditional models of arsenic mobilization, namely reductive dissolution of Fe-oxyhydroxides, reduction of As(V) to more mobile As(III), and bacteria mediated reactions, are active to varying degrees. It is also likely that different processes control arsenic mobilization at different locations of the basin and more detailed studies along major flow paths upgradient of the high arsenic aquifers will shed more light on the mechanisms.     

Thermal performance of borehole heat exchanger under groundwater flow: A case study from Baoding

The performance of ground source heat pumps (GSHPs) depends strongly on the heat transfer between the soil and borehole heat exchangers (BHEs). In the present work, a thermal performance experiment of a BHE under groundwater flow was conducted in Baoding, China. Based on the measurement of the natural ground temperature profile, a simplified theoretical model was presented to estimate the characteristics of groundwater flow. The results showed that the presence of groundwater had an obvious influence on the temperature profile in the aquifer. Due to the strong groundwater advection, the thermal performance of the BHE was enhanced. The enhanced effect depends to a great extent on the distribution and thickness percentage of the ground layer with the greatest groundwater flow. In the present case, the heat injection and heat extraction of the BHE were enhanced on average by 9.8% and 12.9%, respectively, compared with the case without groundwater flow, when the total thickness of coarse sand and gravel layer as a percentage of the borehole depth was 10.6%. This enhanced effect is favorable for reducing the possible imbalance between heat injection and extraction from and to the ground, which is helpful for the long-term operation of GSHP systems.