Significance of Geological Parameters for Predicting Water Inflow in Hard Rock Tunnels

One of the most challenging aspects of tunnelling is prognostication of water inflows. More reliable prediction of groundwater inflow may give considerable economical saving for future tunnel projects and may also prevent damage of environment and installations on the surface. This paper is discussing the significance of eight hypotheses regarding geological parameters for predicting water inflow in tunnels. The respective hypotheses have been tested as part of a recent research project in Norway. Six Norwegian tunnels with different geological conditions were selected for the research; the Romeriksporten, Frøya, T-baneringen, Lunner, Skaugum, and Storsand tunnels. Based on detailed study of these tunnels, the hypotheses are tested by comparing water inflow with geological parameters and factors such as Q value, faulting, rock stress orientation, rock cover, thickness of permeable soil or depth of lake/sea above the tunnel, rock type, and width of weakness zones. It is found that four out of the eight tested hypotheses are supported, two have low to medium support and two are not supported. One unexpected result is that for the tunnels covered by this study, the water inflow was found to increase with rock cover.     

AutoCAD在隧洞地质展示图编制和空间分析中的应用

绘制隧洞地质展示图是施工过程中客观反映洞室围岩地质条件的有效方法,但由于其表示的信息较简单且采集不便,难以进行深入的空间地质信息分析。应用ＡｕｔｏＣＡＤ内嵌语言ＡｕｔｏＣＡＤ,编制和于切制横剖面和高程平切面图的程序,供ＡｕｔｏＣＡＤ调用。在洞群区,分别在各洞室切制统一的横剖面图和其一高程的平切面图,构成洞群区三维空间地质信息系统的模型,为进一步的空间分析提供依据。     

Practical Estimate of Deformations and Stress Relief Factors for Deep Tunnels Supported by Shotcrete

Summary. Even though ground-support interaction in the vicinity of the tunnel face is a typical 3D problem, tunnel support design is usually based on simplified plane strain models, which are strongly dependent on the assumed degree of ground stress relief at the time of lining installation. The paper focuses on tunnels supported by shotcrete close to the face, where the interaction between the loading process and progressive hardening of the green shotcrete makes the problem time-dependent. A constitutive law characterized by the time-dependent stiffness and strength of the shotcrete is employed herein. The results of an extensive parametric study based on 3D axisymmetric models are presented in the form of non-dimensional design charts, which can provide guidance to a preliminary evaluation of convergences and support loadings. Moreover a strategy is proposed to enhance the capability of simplified design methods (2D models, Convergence-Confinement Method). This consists in a “guided estimate” of stress relief factors, which again is based on the results of 3D time-dependent analyses. Finally, by way of example, the proposed method is applied to two well-documented case-histories.     

梁河锡矿矿床地质特征及成因探讨

梁河锡矿床是滇西锡矿带西亚带的主要的矿床类型之一。该矿床位于印度板块与欧亚板块碰撞带前缘的腾冲一梁河弧形构造的转折部位,东邻三江构造带。通过对矿床地质背景、矿床地质特征、控矿因素、成矿物质来源及矿床成因等研究,结果表明该矿床与喜山期的花岗岩岩浆活动有着密切的时空关系和成因联系,表明成矿物质来源于喜山期深部花岗岩浆,矿床属于与花岗岩岩浆活动有关的热液矿床。     

四川九寨沟地质遗迹保护探讨

世界自然遗产九寨沟地质遗迹资源景观丰富。以湖泊、瀑布、钙华津流、钙华彩池等为代表的地质遗迹景观具有极高的科研、观赏价值。应从加强地质遗迹本底调查,加强系统科研,特别是水循环的研究,加强对地质灾害的监测和预防治理等以进一步做好保护工作。     

试论构建铀矿地质工作的新格局

党中央、国务院作出调整电力结构,加快核电发展的决定,并对铀矿资源保障形势十分关注。据此,中核集团公司提出“铀资源大基地”战略设想。为实施这一战略,需要构建铀矿地质工作新格局,加强管理和队伍建设,深化改革,使我国铀矿地质事业不断迈向新高潮。     

四川地质环境信息化工作的探讨

地质环境工作是一个典型的信息密集型行业。分析当前四川省地质环境信息化工作现状,结合四川国土的实际情况,对目前工作中存在的一些问题进行了梳理,对地质环境信息化建设的进一步完善提出了建议。     

Estimate for bearing capacity of a prismatic pillar

SummaryEstimate for Bearing Capacity of a Prismatic Pillar The upper bound theorem of the generalized theory of perfect plasticity is applied in conjunction with a simple curve fitting scheme to estimate the average vertical bearing capacity of a rectangular pillar with variable width-to-height and width-to-length ratios. The general solutions for the two collapse mechanisms that were found to yield the most critical bearing pressures are presented in a dimensionless form whereby the pillar bearing pressure is normalized with respect to the unconfined compressive strength of the pillar rock. In general, it was found that the pillar bearing pressure depends linearly on the pillar width-to-length ratio. Accordingly, it was possible to develop design charts for various ratios of the unconfined compressive strength to the uniaxial tensile strength by plotting the normalized average bearing pressure versus the pillar width-to-height ratio for the two limiting values of zero and one for the pillar width-to-length ratio. For the infinitely long pillar, the bearing pressures obtained by this approach are compared with those obtained by the Sokolovskii slip line solution, and the latter are generally found to be higher, although results depend on the pillar width-to-height ratio.

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ZusammenfassungTragfähigkeit von Felspfeilern Der obere Grenzfall der allgemeinen Theorie der idealen Plastizität erlaubt es, mit Hilfe vereinfachter Diagramme für den Bruchmechanismus die mittlere vertikale Tragfähigkeit eines rechteckigen Felspfeilers für ein veränderliches Verhältnis von Breite zu Höhe und von Breite zur Länge abzuschätzen. Die generelle Lösung von zwei Bruchmechanismen bilden die Grundlage für die Bestimmung der für die Tragfähigkeit des Pfeilers maßgebenden kritischen Druckspannungen. Letztere werden in dimensionsloser Form bezogen auf die Gesteins-Druckfestigkeit des Pfeilers bei unbehinderter Querdehnung ausgedrückt.

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RésuméRésistance à la rupture des piliers rocheux Le cas de la limite supérieure de la théorie générale de la plasticité par faite est appliqué à fin de déterminer la résistance moyenne à la rupture des piliers rocheux à sections rectangulaires soumis à une charge verticale (coefficients variables: largeur-hauteur et largeur-longueur) à l'aide des diagrammes simples. Les solutions générales pour les deux mécanismes de rupture déterminant pour la résistance à la compression (pression critique) du pilier sont représentées sans dimensions en effet, cette résistance est rapportée à la résistance de la roche du pilier. En général, on a constaté que la résistance du pilier est une fonction linéaire du coefficient largeur-longueur. De ce fait, il a été possible de développer des diagrammes pour différents rapports entre la résistance à la compression (déformation latérale libre) et la résistance à la traction uniaxiale en rapportant la résistance moyenne du pilier à la compression en fonction du rapport largeur-hauteur pour deux valeurs limites du rapport largeur-longueur, zéro et un. Pour le pilier infiniment long, les résistances à la compression ainsi obtenues sont comparées à celles de la solution de lignes de glissement selon Sokolovskii; cette solution donne en général des valeurs de résistance plus grandes, bien que les résultats dépendent du rapport largeur-hauteur du pilier.

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With 8 Figures     

特大跨度小净距隧道中间岩柱可靠度分析及其加固处理措施

魁岐2号隧道位于福卅I国际机场高速公路二期工程A3标段,隧道跨度达到19．9m,中间岩柱最小净距为11．7m,为国内首座双向八车道小净距隧道工程。针对魁岐2号隧道工程的特殊性,利用离散单元法对节理岩体中特大断面小净距隧道的受力情况进行了分析,根据可靠度理论,通过对魁岐2号特大断面小净距隧道中间岩柱的可靠性分析发现,对于特大断面小净距隧道,中间岩柱最薄弱的部位主要集中在岩柱上部,因此,埘于特大断面小净距隧道施工过程中宜重点对岩柱上部进行加固处理。同时,根据不同围岩级别中中间岩柱的可靠度值显示,魁岐2号特大断面小净距隧道的净距取值基本上是合理的,整体上二能满足稳定性的要求。     

基性、超基性岩: 二氧化碳地质封存的新途径

CO₂地质封存是控制全球CO₂净排放量的有效手段.自然界存在大量基性、超基性岩石的碳酸盐风化作用, 与CO₂反应生成稳定的碳酸盐矿物.影响基性、超基性岩石与CO₂反应速率的因素有温度、压力、pH值、流体流动速率以及与矿物接触的表面积等.矿物在反应过程中放热可以使碳酸盐化体系进入自我加热的良性循环, 同时控制流体的流动速率可以保持最佳温度并使反应速率最大化.蛇绿岩中的橄榄岩、大陆玄武岩和深海玄武岩在地球表层广泛分布, 可贮存大量CO₂.目前研究表明此方法在技术上可行, 经济成本上有优势.因此, 基性、超基性岩石具有封存CO₂的巨大潜力, 可以作为地质封存CO₂的新途径.      

将我国深海大洋研究推向新阶段

1998年春,我国正式参加大洋钻探国际合作计划(ODP),成为大洋钻探计划的第一个“参与成员”(associatemember),迄今正好5周年,这是令我难忘的5年。1999年2月6日～4月12日,在汪品先院士和WarrenPrell两位首席科学家的共同主持下,在我国南海实施了大洋钻探184航次(ODPLeg184),使我国真正从学术上进入深海研究的国际行列。在那个航次的28位上船科学家中有9位中国人,这是自1968年实施深海钻探计划(DSDP,ODP的前身)的第一次,使我感到特别振奋。ODP184航次及其随后的实验室研究,取得的学术成就包括:(1)建立起西太平洋区近3000万年来最…     

甘肃省合作市早子沟金矿床地质模型的建立及资源总量估算

早子沟金矿位于西秦岭褶皱带北部断褶带与中部裂陷槽之间的过渡部位,通过对早子沟金矿矿床地质特征、矿体地质特征及矿体品位变化特征的研究,建立了该矿床描述性模型、变异函数模型及金品位分形分布模型,探讨了矿区深部勘查的方向,并对矿区资源总量进行了估算。     

Relationality/territoriality: Toward a conceptualization of cities in the world

The paper contributes to the conceptualization of cities in the world by first outlining the conceptual and empirical challenges of theorizing the urban/global nexus in both relational and territorial terms. It argues that the most useful and appropriate approach to understanding contemporary urban governance in global context is to develop a conceptualization that is equally sensitive to the role of relational and territorial geographies, of fixity and flow, of global contexts and place-specificities (and vice versa), of structural imperatives and embodied practices, in the production of cities. In order to illustrate the benefits of this conceptualization, the paper will apply it to the case of how downtown development is governed in many contemporary cities. The role of the Business Improvement District (BID) program and New Urbanist planning models in shaping downtowns will be examined in terms of: (1) how and by whom these models are developed in a global-relational context and are set in motion through scaled circuits of policy knowledge and (2) how the mobilization of these models are conditioned by their territorialization in specific spatial and political economic contexts. The paper emphasizes that the ‘local globalness’ of policy models like BIDs and New Urbanism and their consequences for cities can best be understood through a combined focus on relationality and territoriality.     

Toward a 10' resolution geoid for South America: a comparison study

Since the creation of the Sub-Commission for the Geoid in South America (SCGSA) in 1993, many efforts have been carried out in the different countries in order to improve the geoid computations. The validation of the gravity data in Brazil, Uruguay, Argentina and Chile has improved many of the gravity surveys in those countries. GPS observations carried out on benchmarks of the geometric levelling have been facilitated by the SIRGAS (Geocentric Reference System for South America) project and can contribute for testing the gravimetric determination of the geoid. Several countries made available GPS data for SCGSA like Brazil, Argentina, Venezuela and Chile. The Digital Terrain Model (DTM) has been improved considerably in Brazil and Argentina. A great number of topographic maps has been digitized to generate a DTM grid of 3′ resolution (DTM3). New gravity surveys in the Amazonas region have been in progress along Rio Negro and its tributaries. Many different organizations in most of the countries in South America have been involved with local or national geoid computations. This fact has brought attention to the data in several countries facilitating the efforts for a continental geoid. All these activities are strongly supported by Geophysical Exploration Technology (GETECH) — University of Leeds. The objective envisaged at the moment is to produce a 10′ resolution geoid for South America using FFT and to compare the result with that of the numerical integration of the modified Stokes integral.     

河南省许昌县灵井铁矿床地质特征及深部找矿前景分析

河南许昌县灵井铁矿床是近几年来在许昌铁成矿区发现的又一个大型铁矿床,属火山一沉积变质型。矿体赋存于登封群武庄岩组二段,矿体主要呈似层状,受太古界登封群武庄岩组控制,矿体与围岩产状一致,受矿区古断隆构造控制,其形态呈北西向带状展布。笔者在研究前人成果的基础上,通过对该区高磁异常特征和矿床地质特征的综合分析,认为该区深部找矿前景较好,矿体沿倾向向深部仍有较大的延伸空间,经进一步深部勘查,可以大幅度提高矿床资源储量。     

Toward a standard stratigraphical classification practice for the Baltic Sea sediments: the CUAL approach

The Late Pleistocene and Holocene glacial and postglacial sediments of the Baltic Sea basin are conventionally classified into units according to the so‐called Baltic Sea stages: Baltic Ice Lake, Yoldia Sea, Ancylus Lake and Litorina Sea. The Baltic Sea stages have been identified in offshore sediment cores by fundamentally different criteria, precluding detailed comparisons of the sediment units amongst different sea areas and studies. Here, long sediment cores and reflection seismic and pinger sub‐bottom profiles were studied from an offshore area in the Gulf of Finland, northern Baltic Sea. The strata are divided on the basis of sedimentological criteria into three allostratigraphical formations with subordinate allostratigraphical members and lithostratigraphical formations, following the combined allostratigraphical and lithostratigraphical (CUAL) approach. Sedimentological features are recommended as the primary stratigraphical classification criteria because they do not require the palaeoenvironmental inferences of salinity and water level that are inherent in the conventional classification practice. The presented stratigraphical division is proposed as a flexible template for future stratigraphical work on the Baltic Sea basin, whereby lower‐rank allounits and lithounits can be included and removed locally, while the alloformations will remain at the highest hierarchical level and guarantee regional correlatability. The stratigraphical division is compatible with international guidelines, facilitating communication to the wider scientific community and comparison with other similar basins.     

Prediction of the Bullet Effect for Rockfall Barriers: a Scaling Approach

The so-called “bullet effect” refers to the perforation of a rockfall protection mesh by impact of a small block, which has a kinetic energy lower than the design value, where the design value is determined through tests with relatively large blocks. Despite playing a key role in the overall performance of a flexible rockfall barrier, this phenomenon is still poorly understood at present. An innovative approach for quantitatively characterizing this effect based on dimensional analysis is proposed in this paper. The analysis rests on a hypothesis that the relevant variables in the impact problem can be combined into three strongly correlated dimensionless parameters. The relationship between these dimensionless parameters (i.e., the scaling relationship) is subsequently investigated and validated by means of data generated with a finite element model. The validation process shows that the dimensionless parameters are apt and that the proposed scaling relationship characterizes the bullet effect with a reasonable level of accuracy. An example from the literature involving numerical simulation of a full rock barrier is considered, and satisfactory agreement between the calculated performance of the barrier and that predicted by the established scaling relationship is observed.     

Value of Climate Forecasts for Adjusting Farming Strategies in Sub-Saharan Africa

Sustaining and increasing crop production and productivity has to be a major policy thrust for developing countries. Using a simulation approach different production strategies were evaluated conditioned on climate information to derive optimal strategies to help farmers reduce risk and increase productivity. By examining the existence of options in this case planting dates the study provides an analyses of the expected value and risks associated with changing decisions based on the availability of climate forecasts. The 15-March planting date produced the highest mean yield for the two cultivars examined although 1-April, 15-April and 1-May plantings had one to zero probability of crop failures compared to 15-March with crop failures in 4 out of 20 years. Results indicate losses of between 25 and 35 kg/day due to delays in planting from 15-March planting to 1-June planting for the 120- and 150-day cultivar. El niño years were associated with positive yield deviations for both cultivars and most planting dates. Farmers are known to make tactical adjustments to their management in light of information perceived relevant to the prospects of forthcoming crop. Although in its present form most current forecast products do not provide information on onset of the rainfall, however the information they do provide could play a crucial role in helping farmers reduce the risks posed by climatic variability.     

Value of Climate Forecasts for Adjusting Farming Strategies in Sub-Saharan Africa

Sustaining and increasing crop production and productivity has to be a major policy thrust for developing countries. Using a simulation approach different production strategies were evaluated conditioned on climate information to derive optimal strategies to help farmers reduce risk and increase productivity. By examining the existence of options in this case planting dates the study provides an analyses of the expected value and risks associated with changing decisions based on the availability of climate forecasts. The 15-March planting date produced the highest mean yield for the two cultivars examined although 1-April, 15-April and 1-May plantings had one to zero probability of crop failures compared to 15-March with crop failures in 4 out of 20 years. Results indicate losses of between 25 and 35 kg/day due to delays in planting from 15-March planting to 1-June planting for the 120- and 150-day cultivar. El niño years were associated with positive yield deviations for both cultivars and most planting dates. Farmers are known to make tactical adjustments to their management in light of information perceived relevant to the prospects of forthcoming crop. Although in its present form most current forecast products do not provide information on onset of the rainfall, however the information they do provide could play a crucial role in helping farmers reduce the risks posed by climatic variability.