土壤水力性质确定方法研究进展

介绍了确定土壤水力性质的各种直接方法(包括实验室方法和田间方法两大类)和间接方法如土壤转换函数方法、分形方法、形态学方法、数值反演方法和经验公式法等的研究进展和现状,指出了它们各自的优点和存在的不足.认为要不断地引入新的实验技术和改进测定设备,并把估计土壤水力性质的各种理论方法及实验信息有机地结合起来进行综合研究,以扩大它们的适用范围和提高预测精度.     

Engineering properties of unfired clay masonry bricks

The shortage of low cost and affordable housing in the UK has led to many investigations into new building masonry materials. Fired clay masonry bricks are conventionally used for mainstream masonry wall construction but suffer from the rising price of energy plus other related environmental problems such as high energy usage and carbon dioxide emission. The use of stabilised unfired clay bricks for masonry construction may solve these problems.This paper reports on the engineering properties of unfired clay bricks produced during the first industrial trial of unfired clay material development carried out at Hanson Brick Company, in Stewartby, Bedfordshire, under the Knowledge Exploitation Fund (KEF) Collaborative Industrial Research Project (CIRP) programme. The mixes were formulated using a locally available industrial by-product (Ground Granulated Blastfurnace Slag — GGBS) which is activated with an alkaline (lime or Portland cement) combined with clay soil. Portland cement was not used in the formulation of the unfired stabilised masonry bricks, except as a control, which is a significant scientific breakthrough for the building industry. Another breakthrough is the fact that only about 1.5% lime was used for GGBS activation. This level of lime is not sufficient for most road construction applications where less strength values are needed and where 3–8% lime is required for effective soil stabilisation. Hence, the final pricing of the unfired clay bricks is expected to be relatively low.The laboratory results demonstrate that the compressive strength, moisture content, rate of water absorption, percentage of void, density and durability assessment (repeated 24-hour freezing/thawing cycles) were all within the acceptable engineering standards for clay masonry units. The paper also discusses on the environmental performance of the unfired clay in comparison to the bricks, used in mainstream construction of today. The bricks produced using this technology can be used for low-medium cost housing and energy efficient masonry wall construction.     

柱状节理岩体渗透性模型试验研究

柱状节理岩体是一类典型的结构性岩体,具有柱状节理网络发育、岩体完整性差的特点,其力学和渗流特性呈现出显著的各向异性。在分析柱状节理成因的基础上,从现场试验、物理模型试验、数值试验和理论分析4个方面系统总结了柱状节理岩体力学和渗流各向异性的最新研究成果,分析了现有研究方法和研究成果的不足,探讨了今后柱状节理岩体力学和渗流各向异性特性研究的新方向,即：基于柱状节理冷却收缩形成机制研究一种模拟柱状节理岩体试件一次成型制备方法,在考虑柱状节理卸荷扩容特性的基础上重点开展卸荷条件下柱状节理岩体力学和渗流各向异性规律研究。     

Quantitative characterization of shale gas reservoir properties based on BiLSTM with attention mechanism

Evaluating the potential of shale gas reservoirs is inseparable from reservoir properties prediction. Accurate characterization of total organic carbon, porosity and permeability is necessary to understand shale gas reservoirs. Seismic data can help to estimate these parameters in the area crossing-wells. We develop an improved deep learning method to achieve shale gas reservoir properties estimation. The relationship between elastic attributes and reservoir properties is built up by training a deep bidirectional long short-term memory network, which is suitable for time/depth sequence prediction, on the logging and core data. Except some commonly used technologies, such as layer normalization and dropout, we also introduce attention mechanism to further enhance the prediction accuracy. Besides, we propose to carry on the normal scores transform on the input features, which aims to make the relationship between inputs and targets clear and easy to learn. During the training process, we construct quantile loss function, then use Adam algorithm to optimize the network. Not only the characterization results, but also the confidence interval can be output that is meaningful for uncertainty analysis. The well experiment indicates that the method is promising for reducing prediction errors when training samples are insufficient. After analyzing in wells, the established model is acted upon seismic inverted elastic attributes to characterize shale gas reservoirs in the whole studied area. The estimation results coincide well with the actual development results, showing the feasibility of the novel method on the characterization for shale gas reservoirs.     

Correlation of mineralogical and textural characteristics with engineering properties of selected granitic rocks from Turkey

Granitic rocks show a variety of engineering properties that may affect quarrying operations, tunneling, mining, slope stability and the use of rock as a construction material. The physical and mechanical properties are a function of the mineralogical and textural characteristics of the rock. The purpose of this study is to apply correlation analysis to investigate the relationships between petrographical and engineering properties of granitic rocks. A variety of granitic rock samples from different parts of Turkey were subjected to petrographic studies. The same samples were then tested to determine specific gravity, dry and saturated unit weight, water absorption, effective and total porosity, sonic velocity, Schmidt hardness, point load strength index, uniaxial compressive strength, tensile strength and modulus of elasticity. The relationships between these properties and the petrographical characteristics are described by simple regression analyses. The study revealed that the influence of the textural characteristics on the engineering properties appears to be more important than the mineralogy. It also determined that the types of contacts, grain (mineral) shape and size significantly influence the engineering properties of the granitic rocks.     

降压开采过程中含水合物沉积物的力学特性研究

天然气水合物是一种潜在的能源资源,开采过程中,水合物的分解会造成工程和地质等安全隐患。为研究降压开采过程中多因素综合影响条件下沉积物的力学性质,在自主研发的低温高压三轴仪上进行了不同围压条件下含水合物沉积物的剪切试验。试验结合常规三轴剪切及一个试样多级加荷的方法,并加入了水合物的降压分解过程。结果表明：水合物的存在可以显著提高沉积物的抗剪强度。在降压分解过程中,含水合物沉积物试样的力学强度受到有效围压和孔隙中水合物含量的综合影响。前期试样由于孔隙压力降低导致有效围压大幅增加,试样抗剪强度增大,后期由于水合物含量的大幅降低,试样在较高有效围压下抗剪强度下降。有效围压对含水合物沉积物试样的体积应变有较大的影响,较高的有效围压会导致含水合物试样产生显著的剪缩现象。     

An iterative ensemble Kalman filter for reservoir engineering applications

The study has been focused on examining the usage and the applicability of ensemble Kalman filtering techniques to the history matching procedures. The ensemble Kalman filter (EnKF) is often applied nowadays to solving such a problem. Meanwhile, traditional EnKF requires assumption of the distribution’s normality. Besides, it is based on the linear update of the analysis equations. These facts may cause problems when filter is used in reservoir applications and result in sampling error. The situation becomes more problematic if the a priori information on the reservoir structure is poor and initial guess about the, e.g., permeability field is far from the actual one. The above circumstance explains a reason to perform some further research concerned with analyzing specific modification of the EnKF-based approach, namely, the iterative EnKF (IEnKF) scheme, which allows restarting the procedure with a new initial guess that is closer to the actual solution and, hence, requires less improvement by the algorithm while providing better estimation of the parameters. The paper presents some examples for which the IEnKF algorithm works better than traditional EnKF. The algorithms are compared while estimating the permeability field in relation to the two-phase, two-dimensional fluid flow model.     

Effects of coarse-grained materials on properties of residual soil

Residual soils are generally characterised by a low coefficient of permeability and high shrinkage potential. Several soil improvement methods can be applied to overcome these problems, including mixing the residual soil with coarse-grained soils. In order to study the effects of varying coarse-grained materials on the hydraulic properties and shrinkage characteristics of residual soils, a local residual soil was mixed with different percentages of a gravelly sand and a medium sand. The hydraulic properties and shrinkage potential of the residual soil and the soil mixtures were investigated. The measurements showed that increasing the amount of coarse-grained materials increased the saturated permeability and reduced the shrinkage potential of the residual soil mixture. Increasing the amount of coarse-grained materials in the residual soil produced changes in several key parameters of soil-water characteristic curve (e.g., the slope, the air-entry value, the residual matric suction, and the residual volumetric water content), as well as the unsaturated permeabilities of the soil mixtures.     

Relationships between texture and mechanical properties of hybrid rocks from the Jaala–Iitti complex, southeastern Finland

The relationships between petrographical and mechanical properties of rock aggregate raw materials from the hybridised, subvolcanic Jaala–Iitti complex, southeastern Finland, were investigated. Petrography was quantified from polished thin sections with a polarising microscope to determine the modal composition and grain size distribution, and resistance to fragmentation and abrasion were determined. Abundance of fine-grained minerals (especially of hornblende), fine grain size-dominated grain size distribution, uniform spatial dispersion of hornblende crystals, and intense micrographic intergrowth texture with interlocking grain boundaries were found to have the greatest positive influence on the mechanical properties. The results showed the potentiality of hybridised rocks as raw materials for high quality aggregates that can resist fragmentation and abrasion.     

A discrete element approach to elastic properties of layered geomaterials

Discrete element methods (DEMs) are used for layered geomaterials to investigate the dependency of traditional engineering constants on material properties and loading conditions. Shear deformations and compression tests parallel and perpendicular to layering are conducted on samples of varying kerogen volume fractions, confining pressures, porosities, and layer geometries. The goal of this article is to develop a method to better characterize oil shale (a transversely isotropic layered geomaterial) while eliminating high experimental costs. The DEM simulations conducted in this study demonstrate strong dependencies of Young's modulus, Poisson's ratio, and shear modulus on kerogen volume fraction and porosity. Furthermore, a rule of thumb for layer thickness and particle resolution is proposed for simulation design. Results agree well with robust effective medium theories, solidify the ability of DEM to model the mechanical properties of layered heterogenous materials, and encourage the use of DEM to study more complicated layered media and material failure. Copyright © 2011 John Wiley & Sons, Ltd.     

浸矿开采对离子型稀土基岩力学特性的影响研究

为研究原地浸矿母液对离子型稀土矿收液底板的侵蚀影响,以离子型稀土矿基岩（半/弱风化花岗岩）为研究对象,开展了室内浸矿模拟试验。对比分析了不同浸矿时间岩样的应力−应变曲线、峰值应力、峰值应变和弹性模量,获取了不同浸矿历时岩样的孔隙度和细观形貌特征,并运用盒维法对岩样的非线性裂纹特征进行了定量化描述。结果表明：浸矿侵蚀作用对离子型稀土矿底板基岩力学性质的影响主要表现在前150 d,破坏形式由贯穿破坏转变为贯穿破坏与片状剥落并存;浸矿母液侵蚀作用下,基岩力学特性呈现先大幅减小后大幅回升,其后在小范围波动现象,浸矿约60 d对基岩力学特性的影响程度最大;浸矿母液侵蚀造成基岩内小孔隙增长,导致表面出现腐蚀及孔洞现象;浸矿时间不同将造成岩石不同的微观结构变化。     

Effects of coarse-grained material on hydraulic properties and shear strength of top soil

Sidewalk failures associated with top soil of low shear strength are a common problem in urban areas. Mixing top soil with granite chips can be used to increase its permeability and shear strength. The effects of mixing granite chips with top soils on the hydraulic properties and shear strength under saturated and unsaturated conditions were investigated in this study. The results showed that the mixing top soils with granite chips caused changes in several key parameters of the soil–water characteristic curve (e.g., the air-entry value, the residual matric suction, and the residual volumetric water content) and the unsaturated permeability of the top soils. The saturated permeability and shear strength of the soil mixture increased with increasing content of granite chips.     

Modification of physical, mechanical and hydraulic properties of bentonite by thermo-hydraulic gradients

The conditions of the bentonite in an engineered barrier for high-level radioactive waste disposal have been simulated in a series of tests. Cylindrical cells with an inner length of 60 cm and a diameter of 7 cm have been constructed. Inside the cells, six blocks of FEBEX bentonite have been piled-up, giving rise to a total length similar to the thickness of the clay barrier in a repository according to the Spanish concept. To obtain the blocks, the clay with its hygroscopic water content has been uniaxially compacted at a dry density of 1.65 g/cm³. The bottom surface of the material was heated at 100 °C and the top surface was injected with granitic water. The duration of the tests was 6, 12 and 24 months. The temperatures inside the clay and the water intake were measured during the tests and, at the end, the cells were dismounted and the dry density, water content and some hydro-mechanical properties of the clay (permeability, swelling pressure and swelling under load) were measured at different positions. The values obtained are compared to those of the untreated FEBEX bentonite. The injection of water provokes in the vicinity of the hydration surface an increase of the water content and a decrease of the dry density due to the swelling of the clay, while heating gives rise to an increase of the dry density and a reduction of the water content in the 18 cm closest to the heater, even after 2 years of thermo-hydraulic (TH) treatment. The swelling capacity and the hydraulic conductivity after TH treatment are mainly related to the dry density and water content attained during it. No major irreversible modifications of these properties with respect to those of the untreated clay have been detected.     

近似对称矩阵的直接解法及其应用

所谓近似对称矩阵是指矩阵中仅有极少一部分元素是非对称的,在将对角线以上的非对称元素用其对角线以下的对称元素替代后,该矩阵就变成了一个对称矩阵。在求解非线性连续介质力学问题时常常会遇到近似非对称矩阵。基于Sherman-Morrison定理,给出了一种新的近似非对称矩阵的分解算法。在确保数值稳定性的前提下,无论在求解效率还是在内存开销方面新算法都优于一般的非对称稀疏矩阵的求解器,且仅需对传统的基于LDLT分解的求解器略做修改,即可开发出适应于对称和非对称稀疏矩阵的求解器。最后用一个摩擦接触算例,显示了新算法的优越性。     

Optical properties of pseudovitrinite; implications for its origin

A set of Pennsylvanian coals from the North American coal basins, ranging in vitrinite reflectance from 0.65% to 1.75%, was examined, with special emphasis on the optical properties of pseudovitrinite. The results suggest that pseudovitrinite originates from the same material as telocollinite. Slits in the pseudovitrinite seem to have originated in situ due to low-temperature oxidation of woody material; their opening might have been facilitated by devolatilization during coalification. The dominant orientation of the slits is perpendicular to bedding. The intensity and orientation of the slits in pseudovitrinite could be important factors in predicting coalbed gas extraction from coal.     

Evaluation of geotechnical properties of overburden dump for better reclamation success in mining areas

Coal-mining activities are precursors to land degradation, a part of which is directly related to the generation of huge quantity of overburden (OB) material. The problem of managing OB is mitigated through reclamation, which is directly associated with the geotechnical properties of these dumps. The main objective of this study was to assess the potential of an alternative management plan of OB by analyzing physical properties of these dumps. This alternative management plan of OB could enhance reclamation success by fostering conditions conducive for vegetation growth. This is especially required in old mining areas, where salvaging of topsoil was not done, and as a result, reclamation was affected. For the present study, 12 representative OB samples were collected from two open-cast coal mines (OCP-A and OCP-B) of Bastacolla area in Jharia Coalfield, Dhanbad, India. The samples were analyzed for different geotechnical properties. The results revealed that optimization of these parameters could help in enhancing the reclamation success of the area. From land-use classification, it was observed that about 242 ha of the study area was OB dump; if these areas are reclaimed successfully, then they can act as a potential source of carbon sequestration, and furthermore, they will improve the esthetics and the overall environmental quality at these degraded areas.     

基于重置神经网络在油气储层预测方面的应用

神经网络在地质、油气储层方面有着极其广泛的应用,但是神经网络的结构不仅直接影响到网络性能的优劣,而且较大的影响了其现实应用的效果。这里尝试着将与重置算法相结合的BP神经网络应用于油气储层预测方面,并证实重置神经网络具有更好的应用前景和现实意义。     

Development of an infinite element boundary to model gravity for subsurface civil engineering applications

The accurate modelling of gravity is of crucial importance for a variety of issues including, but not restricted to, the identification of buried objects. Gravity is an unbounded problem, which causes challenges when applying numerical models, i..e.., it results in computational difficulties when specifying the relevant boundary conditions. In order to address this, previous research has tended to generate artificial boundary conditions, e.g., truncating the simulated domain and adding many unrealistic zero-density layers, which introduces more unknown parameters and unnecessarily excessive computational time. In order to overcome such inaccuracies, this paper proposes an innovative development of the finite element modelling technique, which represents a step change in the field of gravity forward modelling. A comprehensive formulation of an infinite element to reproduce the far-field boundary effect using only one layer of infinite elements is presented. The developed model considerably reduces the computational time while obtaining high degrees of accuracy. The model is validated against the exact solution of the problem, and its results show an excellent performance. The proposed method can significantly improve the postprocessing and interpretation stages of data analysis relevant to micro-gravity sensors. The new method is applied to subsurface civil engineering although its applicability is manifold.     

准噶尔盆地陆东—五彩湾地区石炭系火山岩储集性能及影响因素

准噶尔盆地陆东-五彩湾地区石炭系火山岩油气藏勘探近年来取得了重要进展.该区火山岩主要由中-基性火山熔岩和中-酸性火山碎屑岩组成.火山岩的储集空间可以分为原生孔隙和次生孔隙两类.火山岩储集性能主要受岩性与岩相、风化和次生溶蚀作用、构造作用和形成环境等多种因素的共同影响.最有利的储集岩为火山角砾岩和流纹岩,其次为安山岩,而最有利的储集部位为石炭系顶面较厚的风化壳.此外,研究区火山岩岩石类型、火山岩的储集性能及储集空间组合类型等都具有区域性的差异.其中,陆东地区火山岩的储集性能最理想,五彩湾地区火山岩的储集性能略差,三个泉地区火山岩的储集性能最差.