Design of tunnel linings in a creeping rock

Summary The effect of long term rock deformation on lining pressure is considered using different concepts of rock behaviour. These include the conventional characteristic-line or convergence-confinement method, modified to allow for rock ageing, and lining-rock interaction methods using models of linear-viscoelastic, linear-elastic linear viscous, and linear elastic non-linear viscous rock behaviour. Calculations of lining pressures show that the former tends to underestimate, compared with the latter.This paper was presented at the 28th US Symposium on Rock Mechanics in Tucson, Arizona, July 1987.     

低含水量粘土的加载速率效应与蠕变变形

通过对低含水量藤森粘土(Fujinomori clay)试样的单向固结试验,研究了低含水量粘土的加载速率效应与蠕变变形。所采用的藤森粘土土样有湿润(含水量小于15%)、风干(含水量小于4.5%)与烘干(含水量小于1%)3种。试验中,应变率逐步改变,同时进行了蠕变及加、卸载试验以及小幅度的循环加载试验。试验结果表明:湿润土样、风干土样与烘干土样都有明显的加载速率效应与蠕变变形;在大范围的卸载-重复加载过程中,蠕变变形会由卸载初期的正变形逐步发展为后期的负变形,在这个发展过程中存在着中性点(即蠕变为零,或者无蠕变的点);藤森粘土的加载速率效应随含水量的降低有所降低,即湿润藤森土样的加载速率效应更明显。     

Calculated and observed long term performance of Leneghans embankment

This paper presents the finite element (FE) analysis of the consolidation of the foundation of an embankment constructed over soft clay deposit which shows significant time dependent behaviour and was improved with prefabricated vertical drains. To assess the capability of a simple elastic viscoplastic (EVP) model to predict the long term performance of a geotechnical structure constructed on soft soils, a well documented (Leneghans) embankment was analyzed to predict its long term behaviour characteristics. Two fully coupled two dimensional (2D) plane strain FE analyses have been carried out. In one of these, the foundation of the embankment was modelled with a relatively simpler time dependent EVP model and in the other one, for comparison purposes, the foundation soil was modelled with elasto-plastic Modified Cam-clay (MCC) model. Details of the analyses and the results are discussed in comparison with the field performance. Predictions from the creep (EVP) model were found to be better than those from Elasto-plastic (MCC) analysis. However, the creep analysis requires an additional parameter and additional computational time and resources.     

荷载作用下黏性土坡位移场应变场分析

通过室内土坡模型试验,研究了在荷载作用下黏性土坡竖向位移随深度的变化规律、土坡大主应变与最大剪应变分布、土坡的蠕变特性及裂缝作用机制。结果表明,随着荷载的逐渐增大,土坡微结构蠕变不断增加,土体的蠕变过程实质上是土体损伤过程,是土坡微结构能量耗散的过程。土坡的蠕变和损伤积累随着加荷时间延续而增大,损伤各向异性更加明显。坡顶和斜坡面处的损伤程度较大,在坡顶和斜坡面出现裂缝,坡顶的竖向位移大于侧向位移,相反坡底处侧向位移大于竖向位移。     

基于灰色关联度和动态偏离-份额分析法的上海市海洋产业结构分析

上海市拥有良好的海洋资源禀赋,发展海洋经济具有相对优势。为加快上海市海洋经济建设以及优化其海洋产业结构,文章利用2010—2016年的相关数据,采用灰色关联度和动态偏离-份额分析法,分别对上海市海洋三次产业的贡献度以及核心层、支撑层和外围层的动态偏离情况进行量化分析,得出上海市海洋产业结构的相关特征并提出建议。研究结果表明:在三次产业结构方面,与上海市海洋经济关联度最大的是海洋第三产业,其次是海洋第一产业和海洋第二产业,其中海洋第三产业对上海市海洋经济发展发挥最核心的作用;在产业层类方面,上海市海洋经济的核心层、支撑层和外围层均具有较合理的产业结构,其中支撑层的产业结构具有深度优化的态势;建议上海市重点扶持交通运输业和滨海旅游业等海洋产业,保持海洋科研教育管理服务业的持续投入,并关注和培育外围层的海洋相关产业。     

西南极乔治王岛长城站地区第三纪火山岩地质、岩石学特征及岩浆的生成演化

本文根据四次南极考察所取资料,对西南极乔治王岛菲尔德斯半岛长城站地区第三纪火山岩进行了全面和系统的总结,在火山岩地层的划分、岩相学和矿物学特点、岩浆的生成演化等问题上提出了新的认识。 长城站所在的菲尔德斯半岛出露有一套层状的熔岩、火山碎屑岩和火山碎屑沉积岩,是第三纪岛弧火山作用的产物。长城组包括碧玉山段和玛瑙滩段,由熔岩和正常火山碎屑岩组成,同位素年龄测定证明其形成于古新世至始新世。化石组主要形成于渐新世,其下部化石山段的含有植物化石的火山碎屑沉积岩不整合在玛瑙滩段岩层之上,上部的岩块山段以集块熔岩、角砾熔岩为主体,火山活动可能持续到了中新世早期。整个半岛的火山活动有两个高潮,两次较强烈的火山作用之间是较长的喷发间断,造成半岛岩石被风化剥蚀和火山碎屑沉积岩的出现。次火山岩以岩颈、岩墙、岩脉和规模较小的岩株等形式产出,并受到古火山机构和基底断裂的控制,沿着北西西-南东东的方向有规律地分布。从火山喷发中心和火山岩分布特点分析,该区火山活动有从西向东逐渐迁移的趋势。 熔岩以高铝玄武岩和玄武安山岩为主,安山岩、英安岩数量较少。斜长石和普通辉石是最主要的造岩矿物。高铝玄武岩和玄武安山岩中斜长石斑晶的核部往往为倍长石或钙长石,边缘成份与     

Shear-enhanced compaction during non-linear viscous creep of porous calcite-quartz aggregates

In this paper, we extend the previous studies of semi-brittle flow of synthetic calcite-quartz aggregates to a range of temperatures and effective pressures where viscous creep occurs. Triaxial deformation experiments were performed on hot-pressed calcite-quartz aggregates containing 10, 20 and 30 wt% quartz at confining pressure of 300 MPa, pore pressures of 50-290 MPa, temperatures of 673-1073 K and strain rates of 3.0×10⁻⁵/s, 8.3×10⁻⁵/s and 3.0×10⁻⁴/s. Starting porosity varied from 5 to 9%. We made axial and volumetric strain measurements during the mechanical tests. Pore volume change was measured by monitoring the volume of pore fluid that flows out of or into the specimen at constant pore pressure. Yield stress increased with decreasing porosity and showed a dependence on effective pressure. Thus, the yield stress versus effective pressure can be described as a yield surface with negative slope that expands with decreasing porosity and increasing strain hardening, gradually approaching the envelope of strength at 10% strain, which has a positive slope. Creep of porous rock can be modeled to first order as an isolated equivalent void in an incompressible nonlinear viscous matrix. An incremental method is used to calculate the stress-strain curve of the porous material under a constant external strain rate. The numerical simulations reproduce general trends of the deformation behavior of the porous rock, such as the yield stress decreasing with increasing effective pressure and significant strain hardening at high effective pressure. The drop of yield stress with increasing porosity is modeled well, and so is the volumetric strain rate, which increases with increasing porosity.     

青藏高原鲜水河活动断裂带蠕变斜坡地质灾害InSAR识别研究

断裂带附近往往是蠕变斜坡地质灾害的多发区,微小变形是指示蠕变斜坡地质灾害的一项重要标志。本文以青藏高原鲜水河活动断裂带为研究区,选用多期ALOS/PALSAR合成孔径雷达数据进行时序干涉(InSAR)观测,获得了毫米级的地表变形量,结合现场调查、遥感解译和地质条件综合分析,揭示了该区域蠕变斜坡地质灾害的类别、变形特征和空间发育规律:(1)断裂沿线主要发育了蠕变滑坡、蠕变泥石流物源和冰碛物流动3种类型蠕变斜坡地质灾害;(2)蠕滑滑坡具有"错乱的等高线状台阶",凸凹不平的主滑方向地形剖面,舌状地貌,无基岩裸露滑床等特征;(3)鲜水河断裂北段古滑坡、历史地震滑坡和震裂斜坡发育,与断裂带直接相交的,大部分存在蠕滑变形,未相交的往往无蠕滑变形,体现了活动断裂对地质灾害发育的控制作用;(4)发育"土石林型"和"坡面松散堆积物型"两种泥石流,识别特征是物源区有分散的缓慢变形体,流域范围内变形体的数量和速率是重要标志;(5)鲜水河断裂带附近4200m高程以上区域广泛存在现代冰碛物沿冰川槽谷滑动变形,其分布范围广、单体规模大、运动速率高,是现今研究区最主要的地表剥蚀形式之一。研究结果也表明,InSAR技术结合地质条件能有效地识别蠕变斜坡地质灾害,适于山区地质灾害众多、调查不便的工作环境,是地质灾害调查技术未来重要发展方向。     

2011年日本9.0级地震的同震位错以及震后应力松弛过程对中国大陆的影响

本文基于日本GEONET的GPS观测资料, 对日本2011年9.0级地震的同震和震后形变过程进行了研究。 结果表明, 日本9.0级地震使中国大陆出现了显著的同震位移, 几乎对整个中国大陆都有影响。 位移量在中国东北地区最大, 接近甚至超过该地区的年运动速率。 震后1年观测到的形变基本上可由沿着断层面的蠕滑进行模拟, 粘弹松弛的贡献不大。 根据所得到的震后蠕滑模型, 震后1年形变所释放的能量等同于发生一个8.7级地震, 其影响主要在东部地区, 最大位移约为年运动速率的30%。 预测在未来2年, 该地震的影响范围将逐渐减小。 地震造成的粘弹松弛在未来50~100年的尺度上, 对东北地区有拉张效应。 日本9.0级地震整体上起到了卸载中国大陆在板块间挤压过程中所累积应变能的作用, 因此该地震发生后的几个月, 中国大陆东部的地震活动水平较震前明显降低。     

鲜水河断裂带跨断层形变测量及其地震学意义

通过对鲜水河断裂带多年跨断层形变测量资料的分析，揭示出鲜水河断裂带不同部位的形变特征，断裂带破裂区表现为较高速率的蠕滑运动，其运动速率又以极震区为中心向两侧衰减，“闭锁区”则具有运动停滞的特点，并有明显的分段性。断层形变的特殊形态还与地震有一定的关系，如每当形变出现“Ｖ”（或倒“Ｖ”）字型时，会有中小地震对应；断层扭动反向与变化也与地震有关