Natural hazards in British Columbia: an interdisciplinary and inter-institutional challenge

 Although British Columbia experiences many natural hazards, there is as yet no unified policy to promote natural hazard management in the province. The problem is not in the quantity and quality of geoscience assessment of natural hazards, but instead, it is suggested, in the isolation of that work from broader risk perspectives and in the lack of clarity of division of responsibilities between various levels of government. The example of recent changes in perception of the terrain stability problem illustrates how natural hazard problems are driven by social and political priorities rather than by geoscience priorities. Received: 22 November 1998 / Accepted: 22 November 1998     

常州地区含水层系统土层压缩变形特征研究

根据近十几年来分层标和含水层水位观测资料分析了常州地区土层压缩变形特征,表明承压含水砂层中的压缩变形不容忽视,且含水砂层的压缩变形与弱透水层的粘土、粉质粘土相似,均表现出明显的变形滞后现象.为此从水位与时间关系、土层变形与时间关系和水位与变形关系出发,结合室内试验方法,通过选取常州地区含水层系统中第一、二、三承压含水层以及二、三承压含水层间弱透水层和第三承压含水层下覆弱透水层的原状土样,采用单轴侧限压缩试验,分析了常州地区砂土和粉质粘土的次固结（蠕变）特性.试验结果表明常州地区不论是粉质粘土还是砂土,均存在一定的次固结变形,从而启示我们该地区地面沉降模拟中应同时考虑含水砂层的蠕变特性.     

金川软岩蠕变破坏机理电镜实验研究

为探讨金川矿岩石蠕变破坏机理,应用微观扫描电镜(SEM)对蠕变受力情况下岩石破坏断口微观形态进行了观察研究,并分析了其产生的微观破坏机制。结果表明:岩石蠕变断裂的微观机制主要是拉伸、剪切作用下岩石发生脆性断裂,从岩石断裂微观形态研究岩石蠕变断裂,可以更好的揭示岩石断口微观形貌特征、裂纹生核、扩展、及断裂方式与岩石蠕变演进过程的联系。     

双轴压缩条件下绿片岩的蠕变规律研究

在锦屏二级水电站辅助洞绿片岩的双轴压缩蠕变试验结果的基础上,研究了应力路径对双轴压缩蠕变变形的影响。结果表明:当侧向应力相同时,随着轴向应力的增加,轴向稳态蠕变阶段的变形速率逐渐增加;当轴向应力相同时,随着侧向应力的增加,轴向稳态蠕变阶段的变形速率逐渐减小。     

软岩的强度—变形—时间之间关系的试验分析

对软岩和有不连续面的软岩试样进行一系列固结不排水三轴压缩和蠕变试验,测定并分析了它们在正常固结和超固结状态下的应变软化性状、蠕变特性和残余强度的变化规律。探讨了软岩中存在的不连续面对应力－应变关系、残余强度特性和蠕变应变速率的影响。     

Process identification at a slow‐moving landslide in the Vorarlberg Alps

A fine‐grained slope that exhibits slow movement rates was investigated to understand how geohydrological processes contribute to a consecutive development of mass movements in the Vorarlberg Alps, Austria. For that purpose intensive hydrometeorological, hydrogeological and geotechnical observations as well as surveying of surface movement rates were conducted during 1998–2001. Subsurface water dynamics at the creeping slope turned out to be dominated by a three‐dimensional pressure system. The pressure reaction is triggered by fast infiltration of surface water and subsequent lateral water flow in the south‐western part of the hillslope. The related pressure signal was shown to propagate further downhill, causing fast reactions of the piezometric head at 5·5 m depth on a daily time scale. The observed pressure reactions might belong to a temporary hillslope water body that extends further downhill. The related buoyancy forces could be one of the driving forces for the mass movement. A physically based hydrological model was adopted to model simultaneously surface and subsurface water dynamics including evapotranspiration and runoff production. It was possible to reproduce surface runoff and observed pressure reactions in principle. However, as soil hydraulic functions were only estimated on pedotransfer functions, a quantitative comparison between observed and simulated subsurface dynamics is not feasible. Nevertheless, the results suggest that it is possible to reconstruct important spatial structures based on sparse observations in the field which allow reasonable simulations with a physically based hydrological model. Copyright © 2004 John Wiley & Sons, Ltd.     

Creep of saturated materials as a chemically enhanced rate‐dependent damage process

Material behaviour that exhibits characteristics of creep induced by a spontaneous mineral dissolution enhanced by material damage is studied. It is believed that the characteristic rates of the chemical processes involved determine the time‐rate dependence of the resulting strain. A basic model of a combined chemo‐plastic softening and chemically enhanced deviatoric strain hardening for saturated geomaterials is presented. Chemical softening is postulated to occur as a consequence of the net mass removal resulting from dissolution and precipitation of specific minerals occurring at the damage‐generated inter‐phase interfaces. Closed and open systems are discussed. In the former case, deformation at constant stress results entirely from a local compensation mechanism between the chemical softening and strain hardening. The classical three stages of creep are interpreted in terms of mechanisms of dissolution and precipitation, as well as the variation in the reaction surface areas involved in the mass exchange. In an open system, the above local mechanism is enhanced by the removal of mass via diffusion of species affecting the mass balance. Such a system is addressed via a boundary value problem as shown in an example. Copyright © 2007 John Wiley & Sons, Ltd.     

The relationship between rock glacier and contributing area parameters in the Front Range of Colorado

Rock glaciers are an end unit of the coarse debris system that links frost weathering and rockfall to debris transport in mountainous environments. By examining topographic and climatic controls on creep, a better understanding of rock glacier formation and evolution could be obtained. A series of statistical tests were run comparing contributing area parameters (width, length, area, slope, headwall height, etc.) and rock glacier variables (width, length, area, thickness, slope, creep and temperature) in the Front Range of Colorado. Results showed that rock glacier width had the strongest correlation with contributing area width due to an abundance of lobate rock glaciers (r = 0.78). Rock glacier area and contributing area size were also related (r = 0.74), but are also a function of talus production factors. Mean surface velocity appears to be better correlated with thickness (r = 0.58) and length (r = 0.62), rather than slope (r = 0.33). Mean annual air temperature had a stronger exponential relationship with maximum velocities (r = 0.76) compared to mean annual velocity (r = 0.60). Front Range rock glacier velocities tend to decrease with warming, suggesting that the volume of ice and debris, rates of shear in plastic layers, or melt water may have a greater influence on deformation. Copyright © 2007 John Wiley & Sons, Ltd.     

Discrete modelling of time‐dependent rockfill behaviour

This modelling study deals with the time‐dependent behaviour of rockfill media, which is of particular interest during the life of rockfill dams. Breakage of rock blocks and crack propagation are the main processes responsible for rockfill creep and collapse. The modelling procedure presented here is performed on two scales: on the rock block scale, where the grain is taken to be an assembly of rigid particles initially endowed with cohesive bonds, and on the rockfill scale, which is taken to involve a set of breakable grains interacting via contact and friction processes. The grain breakage process is described in term of a thermodynamically consistent damage interface model, where the damage is a gradual delayed process. This model was implemented in a non‐smooth contact dynamics code. The effects of the main parameters involved were analysed by performing numerical studies. The ability of the model to predict the creep behaviour of rockfill media is confirmed by presenting several simulations. Copyright © 2008 John Wiley & Sons, Ltd.     

中原油田高压注水诱发的油水井套管损坏原因分析

中原油田高压注水开发35年,套管损坏严重,严重的影响了油田的开发效果。据研究,油田水井套管损坏主要有错断、变形及破漏等三类,平面上主要分布在断层发育区、高地层水矿化度区、泥岩层和盐膏层发育区,剖面上主要分布在盐膏层段和主力生产井段。提出断层活动、地应力非均质演化、盐岩蠕变、油田开发历程和开采方式及油气流场、化学场演化是中原油田套损的主要控制因素,建立油田油藏油井多参数动态模式,优选与油藏模式匹配的开采方式及增产措施,改造套管动力学环境和化学环境将能防治套损地质灾害的发生。