EXPERIMENTAL AND FIELD STUDY ON MINING-PIT MIGRATION   总被引：5，自引：0，他引：5  

S.Ali Akbar Salehi NEYSHABOURI  Ali FARHADZADEH  Ata AMINI 《国际泥沙研究》2002,17(4)

1 INTRODUCTION Because of the large quantity of sand and gravel in their beds, rivers have always been considered as a major source of sand and gravel for civil works. Acceptable quality, ease of extraction and economy are some of the reasons could be mentioned. Unfortunately, specific laws and regulations regarding the safe in-stream mining have not been provided for users and officials. What should be taken into account are the effects of over-mining of sand and gravel, which can cause …  相似文献   

Reconstruction of the diagenesis of the fluvial-lacustrine- deltaic sandstones and its influence on the reservoir quality evolution-- Evidence from Jurassic and Triassic sandstones, Yanchang Oil Field, Ordos Basin     

罗静兰  S.Morad  张晓莉  闫世可  武富礼  李玉宏  薛军民 《中国科学D辑(英文版)》2002,45(7)

The reservoir quality of Jurassic and Triassic fluvial and lacustrine-deltaic sandstones of the Yanchang Oil Field in the Ordos Basin is strongly influenced by the burial history and facies-related diagenetic events. The fluvial sandstones have a higher average porosity (14.8%) and a higher permeability (12.7×10?3 ?m2) than those of the deltaic sandstones (9.8% and 5.8 ×10?3 ?m2, respectively). The burial compaction, which resulted in 15% and 20% porosity loss for Jurassic and Triassic sandstones, respectively, is the main factor causing the loss of porosity both for the Jurassic and Triassic sandstones. Among the cements, carbonate is the main one that reduced the reservoir quality of the sandstones. The organic acidic fluid derived from organic matter in the source rocks, the inorganic fluid from rock-water reaction during the late diagenesis, and meteoric waters during the epidiagenesis resulted in the formation of dissolution porosity, which is the main reason for the enhancement of reservoir-quality.  相似文献   

Spatial and temporal variability of pore‐water pressures in residual soil slopes in a tropical climate     

R. B. Rezaur  H. Rahardjo  E. C. Leong 《地球表面变化过程与地形》2002,27(3):317-338

It is critical to understand and quantify the temporal and spatial variability in hillslope hydrological data in order to advance hillslope hydrological studies, evaluate distributed parameter hydrological models, analyse variability in hydrological response of slopes and design efficient field data sampling networks. The spatial and temporal variability of field‐measured pore‐water pressures in three residual soil slopes in Singapore was investigated using geostatistical methods. Parameters of the semivariograms, namely the range, sill and nugget effect, revealed interesting insights into the spatial structure of the temporal situation of pore‐water pressures in the slopes. While informative, mean estimates have been shown to be inadequate for modelling purposes, indicator semivariograms together with mean prediction by kriging provide a better form of model input. Results also indicate that significant temporal and spatial variability in pore‐water pressures exists in the slope profile and thereby induces variability in hydrological response of the slope. Spatial and temporal variability in pore‐water pressure decreases with increasing soil depth. The variability decreases during wet conditions as the slope approaches near saturation and the variability increases with high matric suction development following rainfall periods. Variability in pore‐water pressures is greatest at shallow depths and near the slope crest and is strongly influenced by the combined action of microclimate, vegetation and soil properties. Copyright © 2002 John Wiley & Sons, Ltd.  相似文献   

中国西南及邻区上地幔P波三维速度结构/   总被引：8，自引：0，他引：8  

雷建设  周蕙兰 《地震学报》2002,24(2):126-134

利用ISC报告以及中国和NEIC基本测震台网报告中的80974条P波初至到时资料（地震数为7053，台站数为165，且地震和台站都分布在研究区内），对中国西南及邻区（北纬10～36、东经70～110）的深至400km的上地幔三维速度结构进行了研究，分辨率达22．初步结果表明:①研究区速度的横向不均匀性，虽随深度增加而减弱，但至400km深度时仍很明显；②在北纬16和24的纵剖面上，可以看到与印度板块向东和欧亚板块相碰撞挤压相对应的速度结构，以及印度板块与欧亚板块速度结构的差异．在东经90的纵剖面上，与印度板块向北俯冲到欧亚板块（青藏高原）之下相对应的速度结构也比较明显；③在90ｋｍ深度的横剖面上，由缅甸的密支那至越南的洞海的低速条带，可能与红河断裂带有关；④ 提出并使用了能够更为准确直观地描述分辨率好坏的图示方法．   相似文献   

中国与美国西部平均构造剪应力值的比较          下载免费PDF全文

陈培善  白彤霞  李保昆 《地震学报》2002,24(5):479-486

提出了一种估计一个地区平均构造剪应力值的方法．用这种方法，选取哈佛大学公布的1977～1999年共15 993次地震的矩张量数据，估计了美国西部19个地区、中国和邻区43个地区(每个地区为1010范围)的平均环境剪应力值．结果表明，美国西部南加州西部海域和南加州应力最高，达13.7和12.0 MPa，然后向北、向南和向东逐渐递减，但最小也达8.7 MPa，是最高值的63%．中国新疆西北部地区和西藏察隅地区应力水平最高，达17.2和12.9 MPa，比美国高．中国的华北、云南、四川、台湾和美国南加州的应力水平差不多．中国南北地震带的应力水平为13 MPa左右，比南加州略高．两个重要地区的平均剪应力值分布图，提供了地学的基本数据．这些结果可为研究地震活动的大背景提供依据，对研究强地面运动参数(如峰值加速度及反应谱等)的衰减关系也是有用的．   相似文献   

用应变积累释放模型研究中国大陆地块分区地震活动   总被引：11，自引：1，他引：11       下载免费PDF全文

马宏生  刘杰  张国民  李丽 《地震学报》2002,24(6):569-578

依据活动地块假说及活动边界的划分，对中国大陆地震活动进行分区．在此基础上，应用应变积累释放模型，通过地震应变积累释放的计算，研究了中国大陆各活动地块分区的地震活动性，初步探讨了各地块的地震活动阶段划分．此外，还对应变积累释放模型的应用前提条件进行了必要的讨论，并对模型结果中可能出现的问题给予一定分析．   相似文献   

Production of selected cosmogenic radionuclides by muons: 2. Capture of negative muons   总被引：1，自引：0，他引：1  

B. Heisinger  D. Lal  A. J. T. Jull  P. Kubik  S. Ivy-Ochs  K. Knie  E. Nolte   《Earth and Planetary Science Letters》2002,200(3-4):357-369

We have determined the production yields for radionuclides in Al₂O₃, SiO₂, S, Ar, K₂SO₄, CaCO₃, Fe, Ni and Cu targets, which were irradiated with slow negative muons at the Paul Scherrer Institute in Villigen (Switzerland). The fluences of the stopped negative muons were determined by measuring the muonic X-rays. The concentrations of the long-lived and short-lived radionuclides were measured with accelerator mass spectrometry (AMS) and γ-spectroscopy, respectively. Special emphasis was put on the radionuclides ¹⁰Be, ¹⁴C and ²⁶Al produced in quartz targets, ²⁶Al in Al₂O₃ and S targets, ³⁶Cl in K₂SO₄ and CaCO₃ targets, and ⁵³Mn in Fe₂O₃ targets. These targets were selected because they are also the naturally occurring target minerals for cosmic ray interactions in typical rocks. We also present results of calculations for depth-dependent production rates of radionuclides produced after cosmic ray μ⁻ capture, as well as cosmic ray-induced production rates of geologically relevant radionuclides produced by the nucleonic component, by μ⁻ capture, by fast muons and by neutron capture.  相似文献   

Isotope variations in a Sierra Nevada snowpack and their relation to meltwater     

Padinare V. Unnikrishna  Jeffrey J. McDonnell  Carol Kendall   《Journal of Hydrology》2002,260(1-4):38-57

Isotopic variations in melting snow are poorly understood. We made weekly measurements at the Central Sierra Snow Laboratory, California, of snow temperature, density, water equivalent and liquid water volume to examine how physical changes within the snowpack govern meltwater δ¹⁸O. Snowpack samples were extracted at 0.1 m intervals from ground level to the top of the snowpack profile between December 1991 and April 1992. Approximately 800 mm of precipitation fell during the study period with δ¹⁸O values between −21.35 and −4.25‰. Corresponding snowpack δ¹⁸O ranged from −22.25 to −6.25‰. The coefficient of variation of δ¹⁸O in snowpack levels decreased from −0.37 to −0.07 from winter to spring, indicating isotopic snowpack homogenization. Meltwater δ¹⁸O ranged from −15.30 to −8.05‰, with variations of up to 2.95‰ observed within a single snowmelt episode, highlighting the need for frequent sampling. Early snowmelt originated in the lower snowpack with higher δ¹⁸O through ground heat flux and rainfall. After the snowpack became isothermal, infiltrating snowmelt displaced the higher δ¹⁸O liquid in the lower snowpack through a piston flow process. Fractionation analysis using a two-component mixing model on the isothermal snowpack indicated that δ¹⁸O in the initial and final half of major snowmelt was 1.30‰ lower and 1.45‰ higher, respectively, than the value from simple mixing. Mean snowpack δ¹⁸O on individual profiling days showed a steady increase from −15.15 to −12.05‰ due to removal of lower δ¹⁸O snowmelt and addition of higher δ¹⁸O rainfall. Results suggest that direct sampling of snowmelt and snow cores should be undertaken to quantify tracer input compositions adequately. The snowmelt sequence also suggests that regimes of early lower δ¹⁸O and later higher δ¹⁸O melt may be modeled and used in catchment tracing studies.  相似文献   

Stable isotope values of Costa Rican surface waters   总被引：3，自引：0，他引：3  

Matthew S. Lachniet  William P. Patterson 《Journal of Hydrology》2002,260(1-4):135-150

Stable isotope data of surface waters from the humid tropics in general, and Costa Rica in particular, are scarce. To improve our understanding of the spatial distribution of stable isotopes in surface waters, we measured δ¹⁸O and δD in river and lake (n=63) and precipitation (n=3) samples from Costa Rica. We also present data from the IAEA/WMO isotopes in precipitation network as context for our study. Surface water isotope values do not strongly correlate with elevation, stream head elevation, stream length, distance from Caribbean Sea, or estimated mean annual precipitation for the country as a whole. However, the data show distinct regional trends. The δ¹⁸O and δD values downwind of mountain ranges are inversely related to the altitude of the ranges the air masses traverse. In the lee of the high Talamanca Range, δ¹⁸O values are 6–8‰ lower, while in the lee of the lower Tilarán Range δ¹⁸O values are 2–3‰ lower than upwind sites along the Caribbean Slope. An altitude effect of −1.4‰ δ¹⁸O/km is present on the Pacific slope of southern Costa Rica, equivalent to a temperature effect of −0.3‰/°C. The Nicoya and Osa Peninsulas have higher values than upwind sites, suggesting input of Pacific-sourced moisture, evaporative enrichment, or decreased condensation temperatures. Elevated and increasing d-excess values inland along the Nicaragua Trough suggest a recycled component may be an important contributor to the water budget. These data provide preliminary stable isotope information for Costa Rica, and will benefit paleoclimatic research in the region. More detailed studies would be beneficial to our understanding of the controls on stable isotope composition of tropical waters.  相似文献   

Predicting average annual groundwater levels from climatic variables: an empirical model   总被引：8，自引：0，他引：8  

Zhuoheng Chen  Stephen E. Grasby  Kirk G. Osadetz 《Journal of Hydrology》2002,260(1-4):102-117

On the basis of one-dimensional theoretical water flow model, we demonstrate that the groundwater level variation follows a pattern similar to recharge fluctuation, with a time delay that depends on the characteristics of aquifer, recharge pattern as well as the distance between the recharge and observation locations. On the basis of a water budget model and the groundwater flow model, we propose an empirical model that links climatic variables to groundwater level. The empirical model is tested using a partial data set from historical records of water levels from more than 80 wells in a monitoring network for the carbonate rock aquifer, southern Manitoba, Canada. The testing results show that the predicted groundwater levels are very close to the observed ones in most cases. The overall average correlation coefficient between the predicted and observed water levels is 0.92. This proposed empirical statistical model could be used to predict variations in groundwater level in response to different climate scenarios in a climate change impact assessment.  相似文献