页岩孔隙系统研究实验方法

基于页岩孔隙系统的特殊性,讨论了FESEM-QEMSCAN、FIB-FESEM、NANO-CT、氮气吸附法、小角中子散射等几种页岩孔隙系统研究方法的特点和适用范围。指出场发射扫描电镜以及与之结合的能谱和矿物定量评价系统(FESEM-QEMSCAN)是研究页岩纳米级孔隙类型、大小、形态以及矿物分布的基础手段;聚焦离子束扫描电镜、微纳米CT可刻画页岩孔隙系统在三维空间的展布特征,利用获得的三维数据体进行数值模拟,可进一步计算孔隙度、渗透率等物性参数;氮气吸附法可对小于100nm的极微孔隙的孔径、形态进行求算;小角中子散射则可利用孔隙中存在的气体分子,获得孔隙系统连通性等重要参数。最后从页岩岩石组构的角度,探讨了页岩孔隙控制因素,指出有机质含量与成熟度,黏土矿物类型、含量,碎屑颗粒的含量以及成岩强度是影响页岩孔隙系统的主要因素。     

Laboratory Simulation of the Formation Process of Surface Geochemical Anomalies Applied to Hydrocarbon Exploration

The formation mechanisms and processes of geochemical anomalies used as proxies in surface geochemistry exploration (SGE) have not been well understood. Previous studies cannot realize 3D measurement of microseeping hydrocarbons from reservoirs to the surface, which made it difficult to understand the features and pathways of deep hydrocarbon microseepages. Understanding the processes of hydrocarbon microseepages will contribute to the acceptance and effectiveness of surface geochemistry. Based on a simplified geological model of hydrocarbon microseepages, including hydrocarbon reservoir, direct caprock, overlying strata and Quaternary sediments, this work established a 3D experimental system to simulate the mechanisms and processes of deep hydrocarbon microseepes extending to the surface. The dispersive halos of microseeping hydrocarbons in the subsurface were adequately described by using this 3D experimental system. Results indicate that different migration patterns of hydrocarbons above the point gas source within the simulated caprock and overlying strata can be reflected by the ratio of i-butane to n-butane (i-C4/n-C4), which follow diffusion and infiltration (buoyancy) mechanisms. This is not the case for vertical measurement lines far from the point gas source. A vertical gas flow in the form of a plume was found during hydrocarbon microseepage. For sampling methods, the high-density grid sampling is favorable for delineating prospecting targets. Hydrocarbon infiltration or buoyancy flow occurs in the zones of infiltration clusters, coupling with a diffusion mechanism at the top of the water table and forming surface geochemical anomalies. These results are significant in understanding hydrocarbon microseepage and interpreting SGE data.     

华南地区栖霞组菊花状天青石的交代及其地质意义

本文在收集大量菊花石标本的基础上，通过岩石薄片镜下鉴定及X射线衍射分析，识别了华南地区栖霞组菊花石假象内矿物的成因类型，建立了矿物交代序列，并通过对菊花石假象内各种矿物成分的电子探针分析和对交代方解石，脉方解石及其围岩的氧，碳同位素分析，探讨了菊花石交代过程中的成岩环境,合理地解释了菊花石内正延性玉髓和栖霞组内海泡石的成因。     

从资源、区位和市场看番禺市旅游发展定位

番禺市的旅游资源、旅游区位和交通条件,以及客源市场潜力在珠江三角洲乃至广东省都占有十分重要的地位。其旅游发展应定位于以观光旅游为基础,大力发展娱乐旅游和商务旅游,策略吸引珠江三角洲的家庭游客和商务游客。     

预排水动力固结法处理吹填粉土地基的试验研究

为加固新近吹填的处于流塑状态的粉土地基,首先采用轻型井点降水和动力碾压的方法使地基具有一定的初始承载力。然后,施加较大的强夯动力荷载,从而使地基承载力得到显著提高。这一新的综合加固技术称之为预排水动力固结法。通过现场测试,研究了施工过程中诸如井点降水的影响范围、强夯时孔隙水压力的变化范围、深层沉降的变化等问题。同时,对强夯夯击遍数、每点夯击次数、遍与遍之间的间隙时间等有关问题进行讨论。研究表明,预排水动力固结法可显著提高吹填粉土地基的承载力。     

Heavy metal contamination of cultivated wetland soils along a typical plateau lake from southwest China

Topsoil (0–20 cm) samples were collected from four cultivated wetlands including Northern and Western Fields (about 30-year tillage), and Southern and Western Fields (about 20-year tillage) along the Yilong Lake of China in October, 2005. Total concentrations of As, Cr, Cu, Pb, and Zn were determined using the inductively coupled plasma atomic absorption spectrometry in order to assess contamination status in four sampling plots. Results showed that the average concentrations of these heavy metals in Northern and Western Fields were significantly (P < 0.01) higher than those in reference soils, while they were generally lower in Southern and Eastern Fields. All the mean concentrations of heavy metals were lower, except that the average concentrations of As and Cr in Northern Field slightly exceeded the soil quality guidelines. The contamination indices showed low-contamination levels for As, Cu, Pb, and Zn in Northern and Western Fields, while no contamination levels could be observed in Southern and Eastern Fields. As for Cr, they showed moderate-contamination levels in Northern Field, but low or no contamination levels in other three Fields. The integrated contamination index values indicated Northern and Western Fields were moderately contaminated, while Southern and Eastern Fields were less contaminated. The same contamination sources of these heavy metals were identified in these fields using factor- and cluster analysis.     

Denitrification potential of marsh soils in two natural saline-alkaline wetlands

Little information is available on denitrification potential of marsh soils in natural saline-alkaline wetlands. The denitrification potentials of an open wetland in the floodplain(Erbaifangzi wetland) and a closed wetland(Fulaowenpao wetland) in backwater areas in Jilin Province of Northeast China were monitored by an anaerobic incubation at 30℃ for 25 days. Our results showed that the relative denitrification index(RDI) increased gradually with incubation time, and showed a rapid increase in the first 5 days of incubation. The RDI values declined quickly from surface soils to subsurface soils and then kept a small change in deeper soils along soil profiles over the incubation time. Denitrification proceeded much faster in the top 20 cm soils of open wetland than in the closed wetland, whereas no significant differences in RDI values were observed in deeper soils between both wetlands. The RDIs were significantly negatively correlated with bulk density and sand content, while a significantly positive correlation with clay content, soil organic matter, total nitrogen and phosphorous. The maximum net NO–3-N loss through denitrification in 1 m depth were higher in the open wetland than the closed wetland with higher soil pH values. Future research should be focused on understanding the influencing mechanisms of soil alkalinity.     

Spatial and seasonal distributions of soil phosphorus in a typical seasonal flooding wetland of the Yellow River Delta,China

Soil samples from 0 to 100 cm depth were collected in four sampling sites (Sites A, B, C and D) along a 250-m length of sampling zone from the Yellow River channel to a tidal creek in a seasonal flooding wetland of the Yellow River Delta of China in fall of 2007 and spring of 2008 to investigate spatial and seasonal distribution patterns of total phosphorous (TP) and available phosphorus (AP) and their influencing factors. Our results showed that TP contents in spring and AP contents in both seasons in surface soils increased with increasing distances away from the Yellow River channel. TP contents in surface soils (0–10 cm) followed the order Site A (698.6 mg/kg) > Site B (688.0 mg/kg) > Site C (638.8 mg/kg) > Site D (599.2 mg/kg) in fall, while Site C (699.6 mg/kg) > Site D (651.7 mg/kg) > Site B (593.6 mg/kg) > Site A (577.5 mg/kg) in spring. Generally, lower TP content (630.6 mg/kg) and higher AP level (6.2 mg/kg) in surface soils were observed in spring compared to fall (656.2 mg/kg for TP and 5.2 mg/kg for AP). Both TP and AP exhibited similar profile distribution patterns and decreased with depth along soil profiles with one or two accumulation peaks at the depth of 40–80 cm. Although the mean TP content in soil profiles was slightly higher in spring (635.7 mg/kg) than that in fall (628.0 mg/kg), the mean TP stock was obviously lower in spring (959.9 g/m²) with an obvious accumulation at the 60–80 cm soil depth compared to fall (1124.6 g/m²). Topsoil concentration factors also indicated that TP and AP had shallower distribution in soil profiles. Correlation analysis showed that AP had significant and positive correlation with these soil properties such as soil organic matter, salinity, total nitrogen and Al (p < 0.01), but TP was just significantly correlated with TN and Al (p < 0.05).     

Non-coaxiality of soft clay generated by principal stress rotation under high-speed train loading

Plenty of geomechanics tests and theories have confirmed the existence of non-coaxiality while soil is subjected to principal stress rotation. This paper investigated the influence of one particular principal stress path, which is a ‘heart-shape’ stress path that is normally induced by high-speed train loading, on the non-coaxiality of reconstituted soft clay. Hollow cylinder apparatus was employed to carry out series of undrained dynamic tests. The goals of this study were to (1) reveal the essential factors of complex cyclic loading paths that influence non-coaxiality in clayey soil and (2) quantify the influence of the factors on variation in non-coaxiality under the high-speed training loading. To analyze the non-coaxiality under high-speed train loading, (a) the pure rotation stress path was utilized as comparison for underling the different influence that ‘heart-shape’ stress path has from other conventional cyclic stress paths. (b) Two variables, dynamic stress ratio and tension–compression amplitude ratio, were introduced in analyzing the evolution of the non-coaxial angle. (c) Based on the test results, equations for describing the revolution of non-coaxiality were proposed which can help to describe the variation in non-coaxial angle under complex loadings quantitatively and understand the influence of the major factors of the stress path intensively.