砂卵石地层土压盾构掘进掌子面稳定性室内试验与三维离散元仿真研究     

王俊  王闯  何川  胡雄玉  江英超 《岩土力学》2018,39(8):3038-3046

采用?800 mm模型土压盾构开展室内掘进试验,以探究砂卵石中土压盾构隧道掌子面失稳诱发地层变形特征。同时,补充开展三维离散元仿真以挖掘室内试验难以获取的掌子面失稳信息,并研究隧道埋深对掌子面稳定性的影响规律。研究结果表明：砂卵石地层中盾构隧道掌子面失稳发展到地表后,沉降曲面呈上大下小逐步收缩的沙漏状,影响范围小于砂土地层。考虑盾构动态掘进过程后,卵石颗粒接触关系变化十分剧烈,掌子面稳定性被削弱,极限支护压力随之增大。掌子面极限支护压力随隧道埋深基本呈线性增加,极限支护压力与初始支护压力之比则随埋深增大而减小。掌子面失稳机制可根据隧道埋深划分为3种模式。与既有研究相比,考虑了盾构动态掘进过程与实际工程更加接近,可为确保砂卵石地层土压盾构隧道施工掌子面稳定提供参考。  相似文献   

运营期水下盾构隧道管片接缝张开度变化规律     

李长俊  陈卫忠  杨建平  刘金泉 《岩土力学》2018,39(10):3783-3793

水下盾构隧道管片间接缝张开度对隧道防水及运营期结构安全有重要影响。以南京扬子江隧道结构健康监测系统中两个典型监测断面的接缝监测数据为基础,通过多元线性回归分析方法分析在两种不同地层组合下接缝张开度随水位、温度变化的规律;并对接缝张开度随水位变化的规律进行了有限元数值模拟,数值模拟结果与回归分析结果吻合较好。上述分析结果表明,纵缝张开度和横缝张开度随水位、温度的变化均呈现较好的线性关系,具体变化趋势如下：当盾构隧道穿越上砂下岩的上透下不透地层时,环内上半部分管片纵缝张开度随水位的增大而增大,受温度影响则相对较小;当盾构隧道穿越砂性全透水地层时,环内管片纵缝张开度随水位的增大而减小,受温度影响也相对较小;环间横缝张开度在上述两种地层下随水位、温度的变化趋势相同,均随水位增大而增大,随温度的升高而减小。  相似文献   

Shape and amount of the Quaternary uplift of the western Rhenish shield and the Ardennes (western Europe)     

A. Demoulin  E. Hallot 《Tectonophysics》2009,474(3-4):696-708

A good evaluation of the Quaternary uplift of the Rhenish shield is a key element for the understanding of the Cenozoic geodynamics of the western European platform in front of the alpine arc. Previous maps of the massif uplift relied on fluvial incision data since the time of the rivers' Younger Main Terrace to infer a maximum post-0.73 Ma uplift of ~ 290 m in the SE Eifel. Here, we propose a new interpretation of the incision data of the intra-massif streams, where anomalies in the terrace profiles would result from knickpoint retreat in the tributaries of the main rivers rather than from tectonic deformation. We also use additional geomorphological data referring to (1) deformed Tertiary planation surfaces, (2) the history of stream piracy that severely affected the Meuse basin in the last 1 Ma, and (3) incision data outside the Rhenish shield. A new map of the post-0.73 Ma uplift of the Rhenish shield is drawn on the basis of this enlarged dataset. It reduces the maximum amount of tectonic uplift in the SE Eifel to ~ 140 m and modifies the general shape of the uplift, namely straightening its E–W profile. It is also suggested that an uplift wave migrated across the massif, starting from its southern margin in the early Pleistocene and currently showing the highest intensity of uplift in the northern Ardennes and Eifel. These features seem to favour an uplift mechanism chiefly related to lithospheric folding and minimize the impact on the topography of a more local Eifel plume.  相似文献   

盾构法开挖地铁联络通道对地表沉降的影响研究     

孙龙飞  陈振雷  李坚成 《岩土工程技术》2019,(4):197-201,213

世界首条盾构法联络通道一宁波地铁联络通道已经将盾构法挖掘地铁联络通道变为现实,但对于盾构法联络通道挖掘对地表沉降的影响还缺乏足够的认识和积累。以宁波地铁3号线某区间的地铁联络通道开挖为例,对盾构法联络通道施工过程进行了试验测试及CAE(Computer Aided Engineering)仿真,并成功地完成了施工过程中各个工况地表沉降仿真与测试的标定分析,得到了沉降幅值在各工况下的变化规律,指出盾构地铁联络通道施工过程中需要关注的危险工况,据此形成了一套真实、可靠、先进的仿真流程,可为联络通道后续沉降监控及其它联络通道施工过程的沉降预测提供支持。  相似文献   

Numerical simulation of longitudinal settlement of shield tunnel in the coastal city Shanghai     

Li Yuan  Jun Tan 《Marine Georesources & Geotechnology》2017,35(3):365-370

Until now more than 14 subway lines are in operation and some new lines are being built in the coastal city Shanghai. The longitudinal settlement of shield tunnel has significant effect on the safety of the subway operation. In this paper, the deformation of the shield tunnel and the surrounding soil were analyzed by the establishment of a three-dimensional model. The vertical displacements of four paths (Path 1 is on the ground; Path 2 is at the top of the tunnel; Path 3 is in the middle of the tunnel; Path 4 is at the bottom of the tunnel) are affected by the nature of the soil. The horizontal displacement is smaller than the vertical displacement and horizontal displacement of the clay is larger than that of the sand. The distribution of the pore pressure changes with soil properties around the tunnel. The pore pressure of the sand layer is larger than that of the clay layer at the same depth of underlying soil.  相似文献   

Geomorphology of the Barrington Tops area,New South Wales     

A. W. Webb 《Australian Journal of Earth Sciences》2013,60(1-2):187-193

K‐Ar total rock age determinations have been made on a sequence of metasedimentary rocks resting on a 2350 m.y.‐old basement in southern Eyre Peninsula, South Australia. The metasediments have an Rb‐Sr age of 1785 m.y., but K‐Ar isochrons suggest that relatively high temperatures persisted for a further 250 million years before the rocks became systems closed to K and Ar diffusion. A significant amount of ⁴⁰Ar was trapped in the metasediments at the time of closure of the K‐Ar system, 1550 million years ago.  相似文献   

Geochemistry and detrital modes of Proterozoic sedimentary rocks,Bayana Basin,north Delhi fold belt: implications for provenance and source-area weathering     

《International Geology Review》2012,54(1):111-129

Bayana Basin, sited along the eastern margin of the north Delhi fold belt of the Aravalli Craton, contains an ～3000?m-thick sequence comprising one volcanic and seven sedimentary formations of the Delhi Supergroup. The sedimentary units are the Nithar, Jogipura, Badalgarh, Bayana, Damdama, Kushalgarh, and Weir formations in order of decreasing age. Petrographic study of the sandstones as well as major and trace elements (including rare earth elements) and bulk-rock analyses of the shales and sandstones allow the determination of their provenance, source-rock weathering, and basinal tectonic setting. The sandstones are quartz rich and were derived mainly from exhumed granitoids typical of a craton interior. Geochemical patterns of the sandstones and shales are similar. However, trace element abundances are low in sandstones, probably due to quartz dilution. The coarser clastic Damdama and Weir sandstones, which occur at higher stratigraphic levels, have strikingly low trace element concentrations compared with the underlying Bayana and Badalgarh sandstones. All samples show uniform LREE-enriched patterns with negative Eu-anomalies (Eu/Eu*?=?0.16–0.23) and are similar to those of post-Archaean Australian shales (PAAS). However, the (La/Yb) _n ratios (averages 11–18) of all the sedimentary units are higher than those of PAAS, except for the Bayana Sandstone, which has low values (average 6.77). The chemical index of alteration (70–78) and the plagioclase index of alteration (87–97) values and the A–CN–K diagram suggest moderate to intense weathering of the source area.

The provenance analyses indicate that basin sedimentation was discontinuous. It received input from a terrain comprising granitoids, mafic rocks, sedimentary sequences, and tonalite-trondhjemite-granodiorite (TTG) suites. The Nithar and Badalgarh sandstones received input from a source consisting predominantly of granitoids. The succeeding Damdama and Weir sandstones received debris from granitoids and TTG in different proportions. The Kushalgarh shale was possibly derived from a source consisting granites and mafic rocks with a TTG component. The pre-existing sedimentary formations also contributed intermittently during the different phases of sedimentation.

Bulk-rock geochemical data suggest Mesoarchaean gneisses and late Archaean granites of BGC/BGGC (Banded Gneissic Complex/Bundelkhand Granitic Gneiss Complex) basement as possible source terrains. These data indicate deposition in a continental rift setting. The coeval formation of many rift-related Proterozoic sedimentary basins in the BGC/BGGC terrain suggests that the North Indian Craton underwent major intracratonic extension during Proterozoic time, probably triggering the break up of Earth's first supercontinent.  相似文献   

非常规电测深法在工程地质勘查中的应用   总被引：2，自引：2，他引：2       下载免费PDF全文

贾志宽  安西峰  李振峰  张少岭  任静 《地球物理学进展》2006,21(1):296-299

本文提出了“非常规电测深法”的概念及实际操作过程，阐述了其应用条件和效果.存在高阻屏蔽层时电法解释较为困难.针对这一情况，本文提出了高阻屏蔽层影响的校正方法，提高了电法解释的精度和效果.  相似文献   

地铁隧道盾构施工引起的工程性地面沉降研究   总被引：1，自引：0，他引：1  

杨天亮  严学新  王寒梅  詹龙喜 《上海国土资源》2010,31(Z1)

基于上海地区地铁隧道盾构施工引发的工程性地面沉降机理分析,采用数值分析和数学拟合方法,对盾构埋深、地层损失率、盾构半径和穿越土层性质等因素与地面沉降影响范围和最大沉降量之间的基本规律分别进行了深入的分析研究,给出了它们之间各自的定量关系式,并在盾构施工实例中进行了分析和验证。  相似文献   

软土隧道盾构出洞灾害的渗流应力耦合分析   总被引：2，自引：0，他引：2  

魏纲  郭志威  魏新江  陈伟军 《岩土力学》2010,31(Z1):383-387

对盾构出洞口涌水涌砂灾害问题作了分析。利用Midas-GTS软件,建立了盾构出洞施工的有限元模型。考虑盾构出洞施工的渗流-应力耦合效应,研究了盾构工作井外加固土体前方高水位工况下,地下水绕加固土体下卧土层的渗流规律以及加固土体前方原状土的沉降规律。研究结果表明,在假定井外加固土体完全隔水情况下,洞门涌水涌砂灾害的发生与否受到土体加固长度、井外地下水等因素影响;土体加固长度的增加对工程安全有利,但成本较高;地下水位的降低能有效减小盾构出洞洞门涌水灾害的发生,需综合考虑工程安全性、经济性和工期等来确定合理的施工参数。  相似文献