青藏公路路基变形分析

为研究青藏公路多年冻土人为上限在退化过程中对路基变形产生的影响过程和程度, 在唐古拉山以南选择了3处具有代表性的路面进行了为期2 a的路面变形观测. 资料表明, 在多年冻土人为上限退化过程中随着公路路基结构、冻土类型的不同, 路基变形从冻胀和融沉过程、冻胀量和融沉量、发生的时间都有很大的不同. 在高含冰量多年冻土区采用半挖半填结构产生的路基变形最为剧烈, 在含冰量相对少且采用较高路堤结构的地段路基变形过程相对平缓. 同时结合探地雷达的勘察结果对路基下的融化区、多年冻土区的内部结构进行了分析. 结果显示,多年冻土人为上限的下移、地下冰的融化会在多年冻土人为上限以上的地质体中导致较强烈的层间错动和扰动.     

厚层覆盖区综合物化探方法找金试验研究——以广西兴安金石金矿为例

在兴安金石金矿外围 4号分散流异常区 ,通过地电化学提取金测量法 ,查明测区存在 5个走向规模小于 5 0 m的金异常区 ,W( Au) 最大值为 72 .4× 10 - 9,高出背景值十几倍 ,并藉综合土壤吸附汞测量 ,高精度磁测和激发极化法等多种物化探方法来确定这些异常区的地质、地球化学和地球物理特征 ,提出金矿成矿的有利部位在金的地电提取高异常区、高汞量异常区、高磁性异常区、低视电阻率异常区和中等视极化率异常区的“三高一低一中”的找矿模式。确定测区的北北东角 (右下角 )一带具备有利的金矿成矿条件     

Variation in element release rate from different mineral size fractions from the B horizon of a granitic podzol

Far-from-equilibrium batch dissolution experiments were carried out on the 2000–500, 500–250, 250–53 and 53–2 μm size fractions of the mineral component of the B horizon of a granitic iron humus podzol after removal of organic matter and secondary precipitates. The different size fractions were mineralogically and chemically similar, the main minerals present being quartz, alkali and plagioclase feldspar, biotite and chlorite. Specific surface area increased with decreasing grain size. The measured element release rates decreased in the order 53–2>>>2000–500>500–250>250–53 μm. Surface area normalised element release rates from the 2000–500, 500–250 and 250–53 μm size fractions (0.6–77×10⁻¹⁴ mol/m²/s) were intermediate between literature reported surface area normalised dissolution rates for monomineralic powders of feldspar (0.1–0.01×10⁻¹⁴ mol/m²/s) and sheet silicates (100×10⁻¹⁴ mol/m²/s) dissolving under similar conditions. Element release rates from the 53–2 μm fraction (400–3000×10⁻¹⁴ mol/m²/s) were a factor of 4–30 larger than literature reported values for sheet silicates. The large element release rate of the 53–2 μm fraction means that, despite the small mass fraction of 53–2 μm sized particles present in the soil, dissolution of this fraction is the most important for element release into the soil. A theoretical model predicted similar (within a factor of <2) bulk element release rates for all the mineral powders if observed thicknesses of sheet silicate grains were used as input parameters. Decreasing element release rates with decreasing grain size were only predicted if the thickness of sheet silicates in the powders was held constant. A significantly larger release rate for the 53–2 μm fraction relative to the other size fractions was only predicted if either surface roughness was set several orders of magnitude higher for sheet silicates and several orders of magnitude lower for quartz and feldspars in the 53–2 μm fraction compared to the other size fractions or if the sheet silicate thickness input in the 53–2 μm fraction was set unrealistically low. It is therefore hypothesised that the reason for the unpredicted large release rate from the 52–3 μm size fraction is due to one or more of the following reasons: (1) the greater reactivity of the smaller particles due to surface free energy effects, (2) the lack of proportionality between the BET surface area used to normalise the release rates and the actual reactive surface area of the grains and, (3) the presence of traces quantities of reactive minerals which were undetected in the 53–2 μm fraction but were entirely absent in the coarser fractions.     

川滇菱形块体边界的现今地壳形变

依据川滇菱形块体边界带上所有跨断层测量资料，分析了各场地所处断裂的近期形变特征，结果表明；川滇菱形块体北段形变活动逐渐减弱，南段逐渐加强，各条断裂分别显示出不同的变形特征；菱形块体的现今水平形变以左旋走滑运动为主，垂直形变速度较低，且呈上盘抬升与下降交替出现的运动特征，部分场地的形变异常变化与其邻近的地震活动密切相关。     

A model of equilibrium bed topography for meander bends with erodible banks

Channel curvature produces secondary currents and a transverse sloping channel bed, along which the depth increases towards the outer bank. As a result deep pools tend to form adjacent to the outer bank, promoting bank collapse. The interaction of sediment grains with the primary and secondary flow and the transverse sloping bed also causes meanders to move different grain sizes in different proportions and directions, resulting in a consistent sorting pattern. Several models have been developed to describe this process, but they all have the potential to over‐predict pool depth because they cannot account for the influence of erodible banks. In reality, bank collapse might lead to the development of a wider, shallower cross‐section and any resulting flow depth discrepancy can bias associated predictions of flow, sediment transport, and grain‐size sorting. While bed topography, sediment transport and grain sorting in bends will partly be controlled by the sedimentary characteristics of the bank materials, the magnitude of this effect has not previously been explored. This paper reports the development of a model of flow, sediment transport, grain‐size sorting, and bed topography for river bends with erodible banks. The model is tested via intercomparison of predicted and observed bed topography in one low‐energy (5·3 W m^?2 specific stream power) and one high‐energy (43·4 W m^?2) study reach, namely the River South Esk in Scotland and Goodwin Creek in Mississippi, respectively. Model predictions of bed topography are found to be satisfactory, at least close to the apices of bends. Finally, the model is used in sensitivity analyses that provide insight into the influence of bank erodibility on equilibrium meander morphology and associated patterns of grain‐size sorting. The sensitivity of meander response to bank cohesion is found to increase as a function of the available stream power within the two study bends. Copyright © 2002 John Wiley & Sons, Ltd.     

1996年包头6.4级地震的地壳应变特征

根据GPS观测资料求出的水平地应变和由跨断层垂直形变计算出的速率强度累积率，研究了包头-大同地区1992～1995年、1995～1996年和1996～1999年的各时期的应变特征，并对包头6.4级(1996年5月3)地震前后的地应变进行对比，认为以压应变为主导的高值区可能是未来强震孕育的地区．面应变、主压应变、剪应变和趋势累积率同时较高的地区，强震危险性较大．一般低应变区和张应变为主导的地区，孕育强震的可能性小，属于比较稳定的地区．1992～1999年包头-大同地区的GPS水平应变的演变，反映了1996～1998年地震幕的孕育发展及结束的全过程．以压应变为主的高应变区和应变梯度带可作为未来强震危险区的判定标志之一．      

南北地震带强震复发间隔的估计

通过对南北地震带各主要断裂带历史强震的时空特点研究 ,试图寻找出带内各主要构造带强震的复发和填充特征 ,并在此基础上研究其差异性 ,对未来各带发生强震的危险性作出估计     

两个冰期-间冰期旋回的黄土记录及其古气候意义

北京邻区枣沟、斋堂和赤峰黄土－古土壤剖面粒度和磁化率变化在幅度和相位上都有明显的差异。在两个冰期－间冰期旋回，磁化率记录具有冰量变化模式，而粒度记录具有轨道周期特点，粒度和磁化率之间的相位关系在从冰期向间冰期转换和冰期向间冰期过渡的过程中，既有滞后也有超前的表现，很难单纯以成土作用来解释。由于黄土粒度主要反映粉尘源区环境和古风场强度的变化，而磁化率主要记录的是沉积区的成壤作用，反映夏季风的强度变化，因此剖面粒度和磁化率变化的不协调说明古风场和粉尘源区变化与粉尘沉积区气候变化之间不统一。这可能意味着控制夏季风强度变化和控制冬季风强度变化的机制存在差异。     

坝上高原安固里淖粒度年纹层与环境变化

在安固里淖湖心区获取一未扰动沉积物样柱，分析发现了由冬季风搬运物与湖心沉积共同形成的粒度年纹层，建立了纹层年表，恢复了安固里淖湖区8507aB.P，以来的环境变化过程。8507-5429aB.P。冬季风活动较弱，后期的所波动；5429-3244aB.P.冬季风活动较强，3244-2494aB.P。冬季风活动减弱；2494-1165aB.P。冬季风活动略有增强；1165aB.P以来，冬季风活动减弱。安固里小淖粒度年纹层反映的冬季风变化情况与我国北方地区同期的环境变化和海平面变化有很好的对应关系。