利用卡洪山口科学研究钻孔中应力引起的钻孔崩落估计量大水平主应力值

本文我们利用钻孔岩样的力学性质，详细观察应力引起的钻孔崩落和由水压致裂实验估计的最小水平主应力值Ｓｋｍｉｎ，构成了卡洪山口（Ｃａｊｏｎ Ｐａｓｓ）钻孔直至３．５ｋｍ深的最大水平主应力Ｓｈｍａｘ的垂直剖面。正如基本上与所有其它的钻孔一样，卡洪山口钻孔的水压致裂应力测量得到的，最小水平主应力Ｓｋｍｉｎ数据比最大水平主应力Ｓｈｍａｘ的数据多得多（并且更加可靠）。为利用观察的井壁崩落约束Ｓｈｍａｘ的值，使     

利用卡洪山口科学研究钻孔中应力引起的钻孔崩落估计最大水平主应力值

本文我们利用钻孔岩样的力学性质,详细观察应力引起的钻孔崩落和由水压致裂实验估计的最小水平主应力值S_(kmin),构成了卡洪山口(Cajon Pass)钻孔直至3.5km深的最大水平主应力。S_(Hmax)的垂直剖面。正如基本上与所有其它的钻孔一样,卡洪山口钻孔的水压致裂应力测量得到的,最小水平主应力S_(hmin)数据比最大水平主应力S_(Hmax)的数据多得多(并且更加可靠)。为利用观察的井壁崩落约束S_(Hmax)的值,使用了由有效应变能准则得出的脆性破裂准则。这个破裂准则也允许我们考虑钻孔周围的三向应力,并考虑孔隙流体压力以不同方式对岩石强度的影响。比较从崩落估计出的S_(Hmax)剖面和从水压致裂实验得出的S_(Hmax)的估计值表明:当孔隙压力对水压致裂破裂起始的影响可以忽略时,它们相当符合。在这个钻孔中,直至3.5km深的总体应力状态相当于倾滑兼走滑断层型应力状态。最大水平主应力剖面有几个应力值显著减小的地方,它们与主要的断层带有关,这个结果和由水压致裂得出的最小水平主应力S_(kmin)剖面一致。     

根据钻孔崩落资料确定剑川地区应力场方向

本文论述了钻孔崩落的力学机制、产生环境及其与现今构造应力场的关系,介绍了超声波井下电视的测井原理、操作技术和钻孔崩落测井资料分析方法。根据一口800米深钻孔的超声波井下电视测井获得的崩落资料,确定剑川地震活动区最大水平主应力方向为N20°E。这与近两年来在该区采用水压致裂法测定的最大水平主压应力方向N15°E是十分一致的     

非均匀岩石钻孔崩落方位的模拟与研究

钻孔崩落法是地应力测量的一种重要方法，但是考虑到岩石力学性质的非均匀性，崩落方法角会偏离最小主应力方向。用Weibull分布来描述岩石力学性质的离散性，用RFPA方法对非均匀岩石的钻孔崩落方位角进行了模拟。通过对模拟结果的分析，研究了非均匀岩石钻孔崩落方位角的分布情况。指出了RFPA方法进一步应用的前景。     

套芯法、水压致裂法原地应力测量、钻孔崩落及震源机制解分析所得结果的对比

我国已积累了大量震源机制解资料,近年来为各种目的开展了套芯法及水压致裂法原地应力测量,并从一些深钻井的测井资料中获得了一批钻孔崩落数据,为地壳应力状态的研究提供了十分有用的资料.为了进行区域构造应力场的研究,笔者对上述各种方法的测量结果进行了对比研究.在同一个钻孔中用不同的方法进行原地应力测量,如在同一个钻孔中用套芯法及水压致裂法进行观测;用水压致裂法的测量结果与同一钻孔中发现的钻孔崩落资料进行对比.还在相距不远的钻孔中用同样的或不同的方法进行原地应力测量;还将同一地区各种方法所得的资料进行了对比,发现其差异并不很大.这就使我们有可能利用上述各种方法提供的资料来进行区域构造应力场及地壳应力状态的研究.     

套芯法、水压致裂法原地应力测量、钻孔崩落及震源机制解分析所得结果的对比

我国已积累了大量震源机制解资料,近年来为各种目的开展了套芯法及水压致裂法原地应力测量,并从一些深钻井的测井资料中获得了一批钻孔崩落数据,为地壳应力状态的研究提供了十分有用的资料.为了进行区域构造应力场的研究,笔者对上述各种方法的测量结果进行了对比研究.在同一个钻孔中用不同的方法进行原地应力测量,如在同一个钻孔中用套芯法及水压致裂法进行观测;用水压致裂法的测量结果与同一钻孔中发现的钻孔崩落资料进行对比.还在相距不远的钻孔中用同样的或不同的方法进行原地应力测量;还将同一地区各种方法所得的资料进行了对比,发现其差异并不很大.这就使我们有可能利用上述各种方法提供的资料来进行区域构造应力场及地壳应力状态的研究.      

利用孔壁竖向裂缝方位数据分析沂沭断裂带的地应力场特征

区域地应力场状态的特征参数对于区域地壳稳定性分析、深部能源和资源开采以及深部基础设施建设都至关重要。主应力方向是地应力场的重要特征指标之一。在众多基于钻孔的地应力测量与估算方法中,利用钻孔孔壁诱发裂缝(DITF)确定区域应力场最大水平应力方向是最直接的方法之一。利用跨沂沭断裂带布置的3个深度约400m的钻孔,于2012—2014年开展了为期3a的高精度超声波钻孔电视重复扫描录井及水压致裂应力测量工作,以期准确确定区域的地应力场特征。通过录井图像精确识别出竖向裂缝共199组,其中包括钻孔诱发裂缝99组、水压致裂裂缝43组、后期生长裂缝57组。经循环统计方法确定的沂沭断裂带区域应力场的最大水平主应力优势方向为92.28°,并在优势方向附近首次发现竖向裂缝自然生长现象,进一步验证了利用超声波钻孔电视确定应力方向的准确性。     

利用斜井钻孔崩落资料反演冀中坳陷上地壳应力状态

介绍了用斜井钻孔崩落法分析应力状态的正演方法和反演方法．根据冀中坳陷中部地区和南部地区两个地点共6口斜井的钻孔崩落资料，利用正、反演相结合的方法分析了两个地点的水平主应力方向和主应力的相对大小．结果表明，在冀中坳陷中部地区(饶阳凹陷内)和南部地区(深县凹陷)，水平最大主压应力方向分别为N86E和N77E，上地壳浅部(深度1 000～4 000 m)的应力状态因地点而异，其中冀中坳陷中部地区的3个主压应力的相对大小为SH:SV:Sh=1.38:1.00:0.57，即处在走滑型应力状态；而在冀中坳陷南部地区，3个主压应力的相对大小为SH:SV:Sh=0.80:1.00:0.62，即处于正断层型应力状态．      

陕西汉中盆地水压致裂地应力测量分析研究

汉中盆地位于龙门山断裂带东北段的末端,汶川MS8.0地震发生以后,地震活动存在沿龙门山断裂带向NE向发展的趋势.在汉中盆地西缘进行了两个钻孔的水压致裂地应力测量,来分析震后该区地应力状态,以期为该区的地震危险性研究提供实际资料.这两个钻孔深度均为300m左右,相距33m,取得了较好的地应力测试结果.通过对地应力测试结果的综合分析研究,得到以下认识:①在汉中盆地西缘300m深度地层内,最大水平主应力值为5.69—19.52MPa,最小水平主应力值为3.81—10.90 MPa,垂直主应力值约为1.25—7.03MPa,水平主应力占主导地位,垂直应力为最小应力,该地应力状态有利于逆断层的活动;②汉中盆地西部现今最大水平主应力方向为WNW或近EW向;③汶川地震后,目前汉中盆地及其西部地区仍处于构造应力调整阶段,总体相对稳定.     

根据钻孔崩落椭圆确定唐山地区深部地壳应力方向

本文论述了钻孔崩落椭圆与地应力之间的关系,指出崩落椭圆的形成,是由于孔壁附近应力集中而引起的崩落现象,其长轴方向与最小水平主应力方向相平行。 根据在唐山地区2000—4000米深度范围内的三口石油钻孔中的测量结果,得出钻孔崩落椭圆的平均长轴方向为 N 7°W,由此确定的区域地壳最大水平主应力方向为 N 83°E。 最后,我们把钻孔崩落椭圆的结果同该区的震源机制、地应力解除和水力压裂的结果进行了比较,表明均具有良好的一致性。     

Changes in sediment transport in the Kuye River in the Loess Plateau in China

In this paper, the changes in sediment transport over 51 years from 1955 to 2006 in the Kuye River in the Loess Plateau in China are assessed. Key factors affecting sediment yield and sediment transport, such as precipitation depth, discharge, and human activities are studied. To investigate the changes in sediment yield in this watershed, a trend analysis on sediment concentration, precipitation depth, and discharge is conducted. Precipitation depths at 2 Climate Stations （CSs）, as well as discharge and sediment transport at 3 Gauging Stations （GSs） are used to assess the features of sediment transport in the Kuye River. The rtmoff modulus （defined as the annual average discharge per unit area, L/（s·km^2）） and the sediment transport modulus （defined as the annual suspended sediment transport per unit area, t/（yr km^2）） are introduced in this study to assess the changes in runoff and sediment yield for this watershed. The results show that the highest average monthly discharge during the study period in the Kuye River is 66.23 m^3/s in August with an average monthly sediment concentration of 88.9 kg/m^3. However, the highest average monthly sediment concentration during the study period in the Kuye River is 125.34 kg/m^3 and occurs in July, which has an average discharge of 42.6 m^3/s that is much less than the average monthly discharge in August. It is found that both the runoff modulus and sediment transport modulus at Wenjiachuan GS on the Kuye River has a clear downward trend. During the summer season from July to August, the sediment transport modulus at Wenjiachuan GS is much higher than those at Toudaoguai and Longmen GSs on the Yellow River. The easily erodible loess in the Kuye River watershed and the sparse vegetation are responsible for the extremely high sediment yield from the Kuye River watershed. The analyses of the grain size distribution of suspended load in the Kuye River are presented. The average monthly median grain size of suspended load in the Kuye River is largest in February and then decreases until June. In July, the average monthly median grain size of suspended load approaches another peak and decreases until September. Then, the median grain size of suspended load starts to increase until February of the following year. However, the average monthly median grain size of suspended load in the Yellow River at Toudaoguai and Longmen GSs is the smallest between early summer and late fall The median grain size in the Yellow River starts to increase in November and approaches the largest size in January.     

TritiogenicHe in groundwater in Takaoka

³He/⁴He ratios up to 3.5 times the ratio of atmospheric He were found in groundwater samples. The³He enrichment can be attributed to radiogenic³He produced by in-situ beta-decay of³H. This shows that tritiogenic³He is accumulating in confined waters. From tritiogenic³He and³H concentrations, ages of groundwaters can be calculated. Detection of tritiogenic³He gives a tool to trace a tritium contamination which occurred in the past and cannot be assessed only by the³H counting method.     

Variations in trace gas concentrations in different environments in India

Observations of trace gases (SO₂, NH₃, NO₂ and O₃) were made during the period 1981 to 1984 at 6 different locations representative of urban industrial, urban, nonurban, thermal power plant and marine environment. Diurnal variations of the trace gases were studied in an urban environment. Except in the urban industrial environment, the concentration of NH₃ was found in the range of background values. Also, the average concentrations of NO₂ and O₃ at the different environments were in the order of background values. However, the concentrations of SO₂ were substantially higher by about 7 times, in urban industrial and thermal power plant environments. The diurnal variations of SO₂, NH₃ and NO₂ showed anitphase relationship with surface temperature at the urban environment station which is relatively free of industrial pollution. Discussion is centred on trace gas variations in different environments in India together with the values reported for various countries in the world.     

Projected changes in flood indices in selected catchments in Poland in the 21st century

The aim of this study is to estimate likely changes in flood indices under a future climate and to assess the uncertainty in these estimates for selected catchments in Poland. Precipitation and temperature time series from climate simulations from the EURO-CORDEX initiative for the periods 1971–2000, 2021–2050 and 2071–2100 following the RCP4.5 and RCP8.5 emission scenarios have been used to produce hydrological simulations based on the HBV hydrological model. As the climate model outputs for Poland are highly biased, post processing in the form of bias correction was first performed so that the climate time series could be applied in hydrological simulations at a catchment-scale. The results indicate that bias correction significantly improves flow simulations and estimated flood indices based on comparisons with simulations from observed climate data for the control period. The estimated changes in the mean annual flood and in flood quantiles under a future climate indicate a large spread in the estimates both within and between the catchments. An ANOVA analysis was used to assess the relative contributions of the 2 emission scenarios, the 7 climate models and the 4 bias correction methods to the total spread in the projected changes in extreme river flow indices for each catchment. The analysis indicates that the differences between climate models generally make the largest contribution to the spread in the ensemble of the three factors considered. The results for bias corrected data show small differences between the four bias correction methods considered, and, in contrast with the results for uncorrected simulations, project increases in flood indices for most catchments under a future climate.     

Copper in natural waters in Transbaikalia

Cu concentrations in surface (river and lake) and subsurface waters are determined. The geographic pattern of Cu distribution in natural water is identified. This pattern is controlled by the difference between its concentrations in drained rocks and soils and the geochemical redox conditions of its migration. Territories with low, medium, and elevated Cu concentrations in natural waters are identified. The concentrations of Cu in natural waters of the region are found to be generally lower than the Clarke values.     

Changes in thermal extremes in Poland

Changes in thermal extremes of the climate of Poland in 1951–2010 are examined. Warm extremes have become more frequent, while cold extremes have become less frequent. In the warming climate of Poland, the increase in the number of extremely warm days in a year and the decrease in the number of extremely cold days in a year have been observed. Also the increase of the maximum number of consecutive hot days in a year and the decrease of the maximum number of consecutive very cold and extremely cold days in a year have been observed. However, the trends are not of ubiquitous statistic significance, as the natural variability is strong.     

Hydrological changes in the Ganges system in Bangladesh in the post-Farakka period

Abstract

The basin area of the Ganges River in Bangladesh is extremely dependent on a regular water supply from upstream to meet requirements for agriculture, fisheries, navigation, salinity control, and domestic and industrial sectors. In 1975, India commissioned a barrage on the Ganges River at Farakka to divert a significant portion of the dry season flow in order to make the Calcutta Port navigable. Statistical analyses of discharge and water level data have been carried out to determine if significant changes have occurred in the hydrology of the Ganges system in Bangladesh in the post-Farakka period. Siltation of the Gorai River (an offtake of the Ganges River) has also been examined using the stage-discharge relationship and regression analysis. The analyses show that the diversion has caused considerable hydrological changes in the Ganges system in Bangladesh. The water supply in the dry season has been reduced substantially, while siltation of the Gorai River has increased significantly.