地脉动测试技术若干问题的讨论

讨论了地脉动的测试技术以及测试工作中应该重视而且容易被忽视的问题 ,并就地脉动幅值域和频率域特性参数提出不同的看法     

灰-水混合过程的水文地球化学模拟研究

通过粉煤灰与水6种不同比例的混合实验,利用质量平衡模型模拟分析混合静置0,1,3,7,14,21d后的水化学组分,以揭示粉煤灰浸出液中水化学组分的形成机制。研究结果表明:灞桥电厂粉煤灰浸出液为高pH值溶液,浸出液pH值急剧上升是粉煤灰中碱性氧化物CaO水解的结果;粉煤灰-水反应系统中,矿物的溶解沉淀作用和阳离子交换作用是主要的水文地球化学作用。     

21世纪地球科学研究的重大科学问题

凝炼地球科学研究的重大科学问题,对推动地球科学基础研究的发展具有重要意义。美国国家研究理事会（National Research Council）2008年3月发布的研究报告《地球的起源和演化：变化行星的研究问题》提出了21世纪固体地球科学研究的10个重大科学问题：①地球和其他行星的起源;②地球早期的演化历史;③生命的起源;④地球内部的运动及其对地表的影响;⑤地球的板块构造与大陆;⑥地球的物质特性对地球过程的控制;⑦气候变化的原因与幅度;⑧地球—生命的相互作用;⑨地震、火山喷发等灾害及其后果的预测;⑩地球内外流体运动对人类环境的影响。这些重大科学问题对我国的地学发展战略研究及地球科学基础研究均将具有重要的借鉴和指导意义。主要依据NRC的《地球的起源和演化：变化行星的研究问题》报告,对这些重大科学问题进行了解读和分析。     

Fundamental Questions of Ocean Crust and the Dream for Mohole

Knowledge of ocean crust is one of bases to understand the deep and the surface of our planet. Since the definition of the Earth crust based on the geophysical discovery of Moho, marvelous efforts have been made to understand the geological significance of the Moho and the structure of the ocean crust. Up to date, it becomes clear that the Penrose model built up on ophiolite is unsuitable for the explanation of the ocean crust structure along slow and ultraslow spreading ridges, and probably also questionable for that of fast spreading ridges. The only effective way to solve the problem is to drill into the geophysical detected Moho and get samples. With the development of modern technology and more logic scientific strategy, that largely improved from the milestone Mohole projects carried out about half a century ago. The time to realize the Mohole dream seams coming.     

New basis for the constitutive modelling of aggregated soils

Natural and compacted soils are usually characterized by aggregation of particles. The mechanical behaviour of these materials depends on soil structure. The oedometric compression tests performed on aggregated samples presented here showed that these materials exhibit a yield limit depending not only on stress history and stress state but also on soil structure. Evidence is provided using the neutron tomography technique. These results revealed that soil structure modification occurs together with plastic deformations. The experimental results are used to propose a new state parameter to quantify the soil structure. Based on pore-scale experimental observations, an evolution law for this parameter is proposed as a function of associated plastic strains. Considering both soil fabric and inter-particle bonding effects, a new yield limit depending on stress state, stress history and soil structure is introduced for the aggregated soils. Accordingly, a new constitutive framework consistent with strain hardening plasticity is proposed to consider soil structure effects in the modelling of aggregated soils.     

Visualisation strategies for environmental modelling data

We present a framework that allows users to apply a number of strategies to view and modify a wide range of environmental data sets for the modelling of natural phenomena. These data sets can be concurrently visualised to find inconsistencies or artefacts. This ensures at an early stage that models set up for the simulation of hydrological or thermal processes will not give implausible results due to complications based on input data. A number of generally applicable visualisation techniques are provided by our framework to help researchers detect potential problems. We also propose a number of mapping algorithms for the integration of multiple data sets to resolve some of the most common issues. Techniques for the presentation of input- and modelling data in combination with simulation results are proposed with respect to the benefits of visualisation of environmental data within specialised environments. The complete workflow from input data to presentation is demonstrated based on a case study in Central Germany. We identify typical problems, propose approaches for a suitable data integration for this case study and compare results of the original and modified data sets.     

Extending the strain path method analogy for modelling penetrometer installation

The Strain Path Method (SPM) is an approximate framework for simulating the disturbance caused by piles or penetrometers in soil. The key conceptual assumption of the SPM is that the deformation and strain fields caused during these penetration processes are strongly kinematically constrained (especially during undrained penetration of clays) and can be estimated independently from the actual constitutive properties of the surrounding soil. Previous applications of SPM have estimated strain fields for a variety of penetrometer geometries using velocity fields of ideal inviscid fluids. This paper refines the strain field for penetrometers with 60° conical tips using numerically computed velocity fields in viscous fluids with a variety of boundary conditions imposed on the penetrometer shaft. Following a parametric study, a set of flow conditions is selected which provides a best fit between computed soil deformations and physical displacement measurements made in three separate experiments. The approach is simple and rapid and, while highlighting some of the inaccuracies associated with the existing SPM solution, may also be used for comparative purposes to assist the development of other approaches to the deep penetration problem. Copyright © 2000 John Wiley & Sons, Ltd.     

Finite difference techniques for modelling geothermal reservoirs

Two finite difference algorithms suitable for long-time simulation of the exploitation of a two-phase geothermal reservoir are presented. One is based on the hopscotch method proposed by Saul'yev¹ and analysed further by Gordon² and Gourlay.³ The other is based on the well-known ADI method. Both methods use a Newton–Raphson iterative technique in order to obtain accurate solutions of the non-linear difference equations involved. Rapid convergence of the iterative schemes occurs both for single-phase and two-phase reservoir problems. One- and two-dimensional model problems are presented.     

A unifying framework for location-production interaction modelling

Unification of a wide class of spatial and industrial interaction models is accomplished by identifying three structural similarities which exist between different facets of urban and regional behaviour. The resulting conceptual framework for location-production interaction modelling is based upon satisfactory information content. The research problem is to identify a set of accounting and behavioural constraints which characterize the system of interest to an acceptable level of accuracy. In this form of model-building, standard measures of uncertainty and information play a fundamental role.     

Storm surge modelling for the Bay of Bengal and Arabian Sea

Most of the countries around the North Indian Ocean are threatened by storm surges associated with severe tropical cyclones. The destruction due to the storm surge flooding is a serious concern along the coastal regions of India, Bangladesh, Myanmar, Pakistan, Sri Lanka, and Oman. Storm surges cause heavy loss of lives and property damage to the coastal structures and losses of agriculture which lead to annual economic losses in these countries. About 300,000 lives were lost in one of the most severe cyclones that hit Bangladesh (then East Pakistan) in November 1970. The Andhra Cyclone devastated part of the eastern coast of India, killing about 10,000 persons in November 1977. More recently, the Chittagong cyclone of April 1991 killed 140,000 people in Bangladesh, and the Orissa coast of India was struck by a severe cyclonic storm in October 1999, killing more than 15,000 people besides enormous loss to the property in the region. These and most of the world’s greatest natural disasters associated with the tropical cyclones have been directly attributed to storm surges. The main objective of this article is to highlight the recent developments in storm surge prediction in the Bay of Bengal and the Arabian Sea.     

Spatial and scaling modelling for geochemical anomaly separation

A spatial and scaling approach with a user-friendly windows program is introduced which can be used to assist exploration geologists and geochemists in geochemical data analysis and anomaly separation. It can also be used for image enhancement and classification. Statistics are calculated and optimized within a variable-sized moving window centred at an arbitrary sample location. The moving window has both variable size and shape determined by three parameters: r (size), β (ratio of long and short axes), and θ (orientation). It calculates five optimal indexes for each sample location: the optimal statistic U(r₀,β₀,θ₀), optimal size r₀, shape indexes β₀ and θ₀, and scaling index α (singularity exponent). These indexes characterize the entities present in an image from different angles and, therefore, can be analyzed by means of multivariate techniques to assist in image enhancement and classification. The user-friendly program prepared can be used in conjunction with GIS (Geographic Information System) software such as ArcView to implement the spatial and scaling method. It has been applied to the stream sediment geochemical data set (923 grid samples) for gold mineral exploration in the Habahe map sheet, Altay Shan, Xinjiang, northwestern China. The spatial and scaling method provides better results than the ordinary moving average method.     

A critical state framework for modelling bonded geomaterials

A simple unified critical state constitutive model for bonded geomaterials is presented in this paper. The model, which is called CASM-n, is an enhancement of an existing unified critical state model for reconstituted geomaterials (CASM). Characteristic behaviours of a bonded geomaterial such as the pre-yield higher strength and stiffness and the cohesive–frictional shearing mode in the post-yield region are taken into account and included in the reference model. The salient feature of the proposed model is the incorporation of cohesive component into the stress–dilatancy relationship. Consideration of the contribution of cohesion to plastic flow allows the modelling of delayed dilatancy and softening–contraction behaviour, which are two interesting phenomena observed in bonded geomaterials.     

Analytical modelling of hammer impact for pile driving

Estimation of the drivability of piles requires modelling of the hammer impact in order to provide the input force wave at the pile head. Historically, this has been achieved through a numerical model of the hammer components (ram, cushion and anvil), which is then linked with that of the pile in order to effect the drivability analysis. This paper presents an analytical model of hammer impact, based on lumped ram and anvil masses separated by a cushion with internal damping, and connected to the pile which is modelled as a dashpot. Force–time responses derived from the analytical model are compared with actual field data, and also with results from commercially available numerical models of hammer impact. The analytical model is then used to explore the characteristics of hammer impact, with particular attention to combinations of parameters that lead to hammer bounce and, hence, significant loss of energy transferred to the pile.     

Evaluation of alternative conceptual models for groundwater modelling

This study evaluates the alternative conceptual models for groundwater modelling. A true model was created with a synthetic alluvial fan-plain hydrogeological framework. Various alternative conceptual models were evaluated for groundwater flow simulations. The first alternative model is a single aquifer layer model; the second alternative model is a 3-layer aquifer model; and the third model is a 5-layer model consisting of 3 aquifers separated by 2 aquitards. All models could fit very well to the observations with optimized values of hydraulic conductivities. However, the single aquifer layer model can only compute water balance components with good accuracy. The 3-layer aquifer model can be used for water balance computation and groundwater head simulation with small errors. The 5-layer model is capable of simulating water budget, groundwater head distribution and travel times with high accuracy. Multi-model analysis found only the 3rd alternative model superior.     

Numerical modelling for clays with internal discontinuity surfaces

A numerical model capable of performing deformation analysis of a medium containing discontinuity surfaces is presented. The discontinuity can be either a crack, which can be open or closed, or a shear band. The model consists of two separate numerical algorithms, which are coupled together by means of the principle of superposition. In particular, an integral equation scheme based on the theory of dislocations is adopted for modelling the discontinuity, while a finite element discretization is used for the continuous medium. In this paper the discontinuity modelling is illustrated in detail, together with the specific formulation of the principle of superposition adopted, and some simple examples of application are presented. The well-known modelling approach based on Fracture Mechanics theory is also briefly discussed. The two models are compared and some advantages and drawbacks of each are pointed out, comments are made regarding their applicability in the specific case of soil mechanics, and conclusions are drawn as regards the conditions under which one or the other is appropriate. Finally, a full-scale example of deformation analysis using the proposed model is presented. Copyright © 1999 John Wiley & Sons, Ltd.     

Hydromechanical modelling of the SEALEX experiments

Numerical modelling of coupled physical processes in bentonite–sand mixtures under the geological conditions is significant for designing and constructing sealing systems in deep underground repositories for highly radioactive nuclear waste. Within the framework of DECOVALEX 2015, Task A, this work presents the model validation of OpenGeoSys by numerical modelling of coupled hydromechanical (HM) processes in bentonite–sand mixtures. Parameters used in the HM model were determined by modelling the laboratory tests of the sealing experiment (SEALEX). Afterwards these parameters were applied for the modelling of a small-scale mock-up test considering the influence of technological gap and incidental fail of the seal in the sealing system. In order to investigate the availability of employing these HM parameters and numerical models directly to field predictions, the modelling results and measured data of an in situ SEALEX experiment were analysed comparatively. The modelling results reproduced well the main features in HM behaviour of the compacted bentonite–sand mixture, which denotes that the adopted HM models and parameters are adequate for describing the HM processes in the sealing system. It is necessary to take the elastoplastic behaviour and evolution of the permeability of bentonite–sand mixtures into account when using the adopted models to reproduce the HM processes of a sealing system.     

关于冰期演变三个问题的讨论

施雅风和李吉均（1994）在总结80年代以来中国冰川学研究的新进展中,提出了3个有待深化和争论的问题：1）不同地区最大冰期出现先后差别的原因尚不清楚;对是否存在一种与季风区相反的模式,即冰期与雨期同步;3）在冰期变化中"气候因素与构造因素何者为主".这3个问题也可以说是本世纪冰川学研究留给下世纪的3个问题．它的解决只有冰川学、气候学和地球动力学等的结合才有可能文章拟对此3个问题提点看法,以期"抛砖引玉"．     

固体地球科学研究的重大科学问题

应美国能源部、美国国家科学基金会、美国地质调查局和美国宇航局的要求,美国国家科学委员会组织专家,研讨驱动固体地球科学研究的重大科学问题。这些问题的研究将深刻影响我们对地球的理解。