Consistent parameter constraints for soil hydraulic functions

Parameters of functions to describe soil hydraulic properties are derived from measurements by means of parameter estimation. Of crucial importance here is the choice of correct constraints in the parameter space. Often, the parameters are mere shape parameters without physical meaning, giving flexibility to the model. A fundamental requirement is that the hydraulic functions are monotonic: the retention function and the conductivity function can only decrease as the capillary suction increases. A stricter physical requirement for the conductivity function is that its decrease with respect to saturation is at least linear. This linear decrease would occur if all pores of a capillary bundle had an equal radius. In the first part of this contribution, we derive constraints for the so-called tortuosity parameter of the Mualem conductivity model, which allow highest possible flexibility on one hand and guarantee physical consistency on the other hand. In combination with the retention functions of Brooks and Corey, van Genuchten, or Durner, such a constraint can be expressed as a function of the pore-size distribution parameters. In the second part, we show that a common modification of retention models, which is applied to reach zero water content at finite suction, can lead to the physically unrealistic case of increasing water content with increasing suction. We propose a solution for this problem by slightly modifying these models and introducing a correct parameter constraint.     

Widespread overspill from a saline density‐current channel and its interaction with topography on the south‐west Black Sea shelf

Seaward of the Bosphorus Strait, the south‐west Black Sea shelf is dominated by the world's largest channel network maintained by a quasi‐continuous saline (ca 35 → 31 psu) underflow. Calculations indicate that >85% of the initial discharge of ca 10⁴ m³s^?1 spills overbank before the shelf edge. This paper documents interaction of the overspill with sea bed topography using multibeam bathymetry, echo‐sounder images of the water column, conductivity–temperature–depth profiles and sediment cores. Overbank spill is widespread, particularly through crevasse channels and on the middle shelf where confinement by channel banks is negligible. Towards the outer shelf, the wind‐driven Rim Current advects mud along the shelf, contributing to levée successions and deposition on stoss sides of elongate transverse ridges. Echo‐sounder profiles reveal metre‐scale eddies over megaflutes, and breaking lee waves and internal hydraulic jumps over ridges. Megaflutes reach 600 m long and 7 m deep, yet form where the underflow, outside the flute, is no thicker than ca 2 to 5 m. Two types of elongate seaward‐facing ridges are recognized. Type 1 ridges, 2 to 5 m high, consist of bivalve‐rich muddy sand in low‐angle (3·5° to 6°) cross‐sets created by the underflow. Type 2 ridges, ca 5 m high, have crests up to 2 km long and a buried wedge‐shaped foundation (the ‘ridge‐core’) comprised of facies similar to Type 1 ridges. These ridge‐cores are blanketed on the landward side by stratified muds, and are capped by obliquely oriented ribs supporting a diverse benthic community. This facies distribution is interpreted to result from stoss‐side and lee‐side velocity and turbulence fluctuations induced by internal hydraulic jumps and breaking lee waves in overspilling portions of the underflow. Experimental results published by W.H. Snyder and co‐workers effectively explain ridge evolution and flow across the ridges, and therefore can be applied with confidence to less easily studied deep‐marine settings swept by turbidity currents.     

钻孔灌注桩泥浆流变特性及水力参数研究分析

钻孔灌注桩泥浆主要功能是稳定孔壁、悬浮和携带钻渣,其泥浆流变特性和水力参数对泥浆作用至关重要。本文首先实验研究了钻孔灌注桩泥浆的流变特性;然后推导出了钻孔灌注桩泥浆流变参数的计算公式;最后分析了钻孔灌注桩泥浆稳定孔壁、携带和悬浮钻渣的特性,对评价和优化钻孔灌注桩泥浆具有重要理论和实践意义。     

Discussion: Stratigraphy and structural summary of the Cooma metamorphic complex

Field and petrographic studies on granitic, hematitic and chloritic breccias in the central portion of the Mount Painter Inlier, South Australia, indicate that: (i) breccias and brecciated basement extend to depths exceeding 400 m and have gradational contacts; (ii) clasts are mainly autochthonous and contain fine‐scale hematite, chlorite or quartz veinlets and fractures; (iii) K‐metasomatism preceded hematitisation and chloritisation; (iv) hematitic breccia intrudes a pegmatite dyke correlated with the Ordovician Arkaroola Pegmatite; and (v) U, F and REE‐containing minerals are present in the Proterozoic basement rocks, and concentrated in the breccias.

With a single exception, δ³⁴S values for pyrite from the breccias and brecciated granites fall in the narrow range —2.9% to +3.5%, implying formation from magmatic emanations or reducing fluids that leached sulphide minerals of magmatic derivation. δ³⁴S values for three barite samples are all close to +16%o, and firm conclusions cannot be drawn from these data. Calcites from the same rock‐types as the pyrite have δ¹³C values of — 22.3%o to —4.2%o and δ¹⁸O values of —4.0%o to +23.1%., with an inverse δ¹³C/δ¹⁸O relationship. The more ¹³C‐depleted calcites probably incorporated CO₂ from organic C, and their δ¹⁸O values are compatible with precipitation from magmatic or metamorphic fluids; mixing of such fluids with meteoric waters is implied by the calcites with variably lower δ¹⁸O values.

The above features indicate that the major processes leading to brecciation and associated metasomatism were hydraulic fracturing and hydrothermal activity resulting from ascent of granitic magmas to shallow crustal levels during late stages (late Ordovician‐?Silurian) of the Delamerian Orogeny. Tectonic and sedimentary processes appear to have played relatively minor roles in breccia formation.     

土壤饱和导水率的多尺度预测模型与转换关系

运用联合多重分形方法研究不同土层土壤饱和导水率与土壤基本物理特性的多尺度相关性,建立不同土层土壤饱和导水率的多尺度预测模型,构建不同土层土壤饱和导水率之间的转换关系。结果表明:不同土层土壤饱和导水率与土壤基本物理特性的相关程度排序不同;在单一尺度和多尺度上,0~20 cm土层土壤饱和导水率与土壤基本物理特性的相关程度排序相同,20~40 cm土层土壤饱和导水率与土壤基本物理特性的相关程度排序不同;土壤饱和导水率多尺度预测模型的预测精度较高,0~20 cm土层和20~40 cm土层拟合值的均方根误差分别为0.035 0和0.029 0;0~20 cm土层和20~40 cm土层土壤饱和导水率转换关系的计算精度较高,拟合值的均方根误差为0.037 5。     

地面高精度磁测基点联测与数据拼接方法

本文对地面高精度中同年度使用同一基点、同年度使用不同基点、不同年度使用同一基点和不同年度使用不同基点等四种情况进行了讨论,提出了解决办法,并通过实例进行对比,最后对问题进行了归纳和总结.     

新型液压活塞取样钻具的研制

江、河、湖、泊等水域取样是环境科学研究与资源勘查必不可少的工作。本项研究提供了一种适合水域取样的新型钻具——液压活塞取样钻具。与传统的活塞钻具相比,具有取样效率高、对地层适应能力强的特点。主要介绍了该钻具的结构及工作原理。     

HC600型全液压动力头便携式钻机在陇东南山区生产应用效果及经济性分析

通过HC600型全液压动力头便携式钻机在武山温家沟金矿区、文县筏子坝外围铜矿区进行NQ、BQ型金刚石绳索取心钻探的效果,分析了全液压动力头便携式钻机相对于立轴式钻机的优点、不足及其经济性,提出全液压动力头便携式钻机在陇东南山区的适用性及我国地质岩心钻机发展的趋向。     

绳索取心液动锤在中国岩金勘查第一深钻的应用和最新进展

在中国岩金勘查第一深钻ZK96—5钻孔的深部施工中,应用绳索取心液动锤技术在破碎复杂地层中钻进,增加回次进尺,提高时效,延长钻头寿命;在比较完整地层中提高钻速,减少辅助时间,体现了绳索取心液动锤技术的优越性,目前3911．34m的使用深度创造了绳索取心液动锤适应孔深的最新记录。对绳索取心液动锤在深部钻进的优势和易出现的问题进行了分析总结。     

应用水力空化射流技术提高灰岩地层钻速

水力空化射流技术具有安全、可靠、效果好等特点,在石油钻井中得到了推广应用。针对伊朗Y油田中下部中硬灰岩地层可钻性差、机械钻速低的情况,试验应用了水力空化射流工具。研究了试验油田的地层强度及可钻性参数,优选了水力脉冲空化射流装置和下部钻具组合,优化了机械及水力参数。现场实钻资料表明,水力空化射流工具提高钻速明显,对中硬地层的灰岩具有良好的钻进效果。