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Viscoplastic solutions of time-dependent deformation for tunnels in swelling rock mass considering stress release

Journal of Rock Mechanics and Geotechnical Engineering 2023年第8期15卷 2053-2071页

作者： Gengyun liu Youliang chen HyonChol Rim Rafig Azzam Department of Geotechnical Engineering Tongji UniversityShanghai200092China Department of Civil Engineering University of Shanghai for Science and TechnologyShanghai200092China Department of Engineering geology and Hydrogeology RWTH Aachen UniversityLochnerstr.4-20 Haus AD-52064AachenGermany

Excavation and control of tunneling responses in swelling soft-rock tunnels of Sichuan-Tibet railway under seepage conditions were *** this,a fractional viscoplastic(FVP)model for swelling soft rocks was established by introducing Abel dashpot and unsteady viscosity coefficient,considering additional swelling deformation and damage of rock caused by humidity *** view of the FVP model,the viscoplastic deformation solutions for rock mass surrounding tunnel under seepage conditions were derived and long-term mechanical responses of swelling rocks upon tunnel excavation were ***,a stress release coefficient considering seepage and creep was proposed,based on which control responses considering stress release and failure mechanism of stress release measures were *** results showed that:(i)The one-dimensional(1.)FVP model has a good application for swelling rock and the three-dimensional(3D)FVP model could well describe the whole creep process of rock mass despite a much higher creep attenuation rate in the first stage of creep;and(ii)An appropriate stress release and deformation of surrounding rocks could effectively reduce the supporting ***,upon a large stress release,the radius of plastic region could increase significantly,and the strength of the surrounding rock mass decreases *** proposed solution could provide a theoretical framework for capturing the excavation and support responses for tunneling in swelling rock mass in consideration of time effect.

关键词： Sichuan-tibet railway Viscoplastic deformation Stress release Fractional model Tunneling engineering

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Paleoceanographic records in the Chukchi Basin, western Arctic Ocean during the late Quaternary

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Acta Oceanologica Sinica 2012年第1期31卷 83-94页

作者： WANG Rujian XIAO Wenshen SHAO Lei chen Jianfang GAO Aiguo State Key laboratory of {1. geology Tongji UniversityShanghai 200092China Second Institute of Oceanography State Oceanic AdministrationHangzhou 310012China Department of Oceanography Xiamen UniversityXiamen 361005China

The late Quaternary paleoceanographic changes in the western Arctic Ocean are revealed by quan- titative studies of foraminiferal abundance, ice-rafted detritus （IRD） and its mineralogical and petrological compositions, planktonic Neogloboquadrina pachyderma （sin.）（Nps）-δ1.O and -δ1.C, biogenic and non-biogenic components in Core M03 token from the Chukchi Basin during the Sec- ond Chinese National Arctic Expedition cruise. Seven IRD events appeared at MIS 7, 5, 3 and 1. These IRD were carried in massive icebergs, which were exported to the Beaufort Sea through the M＇Clure Strait Ice Stream, Canadian Arctic Archipelago, and then transported into the Chukchi Basin by the Beaufort Gyre. Low IRD deposition occurred during the glacial times when more extended ice cover and weakened Beaufort Gyre, while the open water condition and the intensified Beaufort Gyre during interglacial periods favored the IRD deposition. Therefore, the IRD events not only indicate the provenance of coarser detritus and ice export events, but also reflect the evolutionary histories of the Beaufort Gyre and North American ice sheet. Seven light Nps-δ1.O and -δ1.C excursions could respond to enhanced rates of sea ice formation resulting in the pro- duction and sinking of isotopically light brines, but was irrelevant to the warm Atlantic water and freshwater inputs. Whereas, the heavy Nps-δ1.O and -δ1.C values separately reflect the lessened Arctic freshwater and Pacific water, and well-ventilated surface water from the continental shelf and halocline water. Variations of CaCO3 content and planktonic foraminiferal abundance during the interglacial and glacial periods can demonstrate the incremental or diminishing input of the Atlantic water, while the total organic carbon （TOC） and opal contents increased and decreased during the glacial and interglacial periods, respectively, which could be related to the TOC degradation, opal dissolution and redox conditions of interface between the bottom wat

关键词： IRD events ice sheet light Nps-δ1.O and -δ1.C excursions surface productivity late Quaternary Arctic Ocean Chukchi Basin

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Magnetic minerals in Mid-Pleistocene sediments on the Caiwei Guyot,Northwest Pacific and their response to the Mid-Brunhes climate event

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Acta Oceanologica Sinica 2021年第12期40卷 1-11页

作者： liang Yi Haifeng Wang Geng liu Yanping chen Huiqiang Yao Xiguang Deng State Key laboratory of {1. geology Tongji UniversityShanghai 200092China Ministry of Natural Resources Key laboratory of {1. Mineral Resources Guangzhou Marine Geological SurveyChina Geological SurveyGuangzhou 510075China Southern marine Science and Engineering Guangdong {1.(Guangzhou) Guangzhou 510301China Second Institute of Oceanography Ministry of Natural ResourcesHangzhou 310012China

Seamounts are ubiquitous topographic units in global oceans,and their influences on local oceanic circulation have attracted great attention in physical oceanography;however,previous efforts were less made in paleoclimatology and *** Caiwei Guyot in the Magellan Seamounts of the western Pacific is a typical seamount,and in this study,we investigate a well-dated sediment core by magnetic properties to reveal the relationship between deep-sea sedimentary processes and global climate *** principal results are as follows:(1.the dominant magnetic minerals in the sediments are low-coercivity magnetite in pseudo-single domain range,probably including a biogenic contribution;(2)the variabilities of magnetic parameters can be clustered into two sections at~500 ka,and the differences between the two units are evident in amplitudes and means;(3)changes in the grainsize-dependent magnetic parameters can be well correlated to records of global ice volume and atmospheric CO;in the middle *** on these results,a close linkage was proposed between deep-sea sedimentary processes in the Caiwei Guyot and global climate *** linkage likely involves different roles of biogenic magnetite in the sediments between interglacial and glacial intervals,responding to changes in marine productivity and deep-sea circulation and displaying a major change in the MidBrunhes climate ***,we proposed that the sedimentary archives at the bottom of the Caiwei Guyot record some key signals of global climate changes,providing a unique window to observe interactions between various environmental systems on glacial-interglacial timescales.

关键词： Caiwei Guyot middle Pleistocene magnetic properties mid-Brunhes event abyssal sediments western Pacific Magellan Seamounts

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对福建海岸晚第四纪地质若干问题的商榷

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台湾海峡 1987年第1期6卷 40-45页

作者：李从先陈刚杨红君陆成斌韩昌甫同济大学海洋地质系

本文对福建海岸晚第四纪地质的“老红砂”、“海滩岩”、“海蚀地貌”、海平面变动和新构造运动等问題进行了讨论,提出了一些与前人不大一致的观点。

关键词：交错层理低角度泥炭层海滩岩碳酸盐岩老红砂碎屑岩碎屑沉积岩海滩沉积新构造运动晚第四纪地质福建若干问题

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Pitfalls of acid leaching method for determining organic and inorganic carbon contents in marine sediments

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Acta Oceanologica Sinica 2020年第8期39卷 96-102页

作者： chen {1.ng Zhifei {1.u Jingwen Zhang Yulong Zhao Yanwei Zhang Adrian RFernandez State Key laboratory of {1. geology Tongji UniversityShanghai 200092China

Organic and inorganic carbon contents of marine sediments are important to reconstruct marine productivity,global carbon cycle, and climate change. A proper method to separate and determine organic and inorganic carbons is thus of great necessity. Although the best method is still disputable, the acid leaching method is widely used in many laboratories because of its ease-of-use and high accuracy. The results of the elemental analysis of sediment trap samples reveal that organic and inorganic carbon contents cannot be obtained using the acid leaching method, causing an infinitely amplified error when the carbon content of the decarbonated sample is 1.%±1. according to a mathematical derivation. Acid fumigation and gasometric methods are used for comparison, which indicates that other methods can avoid this problem in organic carbon analysis. For the first time, this study uncovers the pitfalls of the acid leaching method, which limits the implication in practical laboratory measurement, and recommends alternative solutions of organic/inorganic carbon determination in marine sediments.

关键词： marine sediments organic carbon inorganic carbon acid leaching method limitation

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Geochemical characteristics of Oligocene-Miocene sediments from the deepwater area of the northern South{1. Sea and their provenance implications

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Acta Oceanologica Sinica 2018年第2期37卷 35-43页

作者： chen Shuhui QIAO Peijun ZHANG Houhe XIE Xiaojun CUI Yuchi SHAO Lei State Key laboratory of {1. geology Tongji University Shanghai 200092 China Shenzhen Branch of china National Offshore Oil Corporation Guangzhou 510240 China china National Offshore Oil Corporation Research Institute Beijing 100027 China

Geochemical and detrital zircon U-Pb dating data for drilled sediments from the Baiyun deepwater area of the northern South china Sea demonstrate a change of sedimentary sources from the O{1.gocene to the *** ages of the pre-rift Eocene sequences are dominated by Yanshanian ages with various peak values（1.0–1.5 Ma for U1.35 and L21. 1.0 Ma for H1., indicating local sediment supply from the pre-existing Mesozoic magmatic belt. For the O{1.gocene sediments in the northern part of the basin, the rare earth elements show different distribution characteristics, indicating sediment supply from the paleo-Zhujiang River（Pearl River）, as also confirmed by the multimodal zircon age spectra of the Lower O{1.gocene strata in Well X28. By contrast, a positive Eu anomaly characterizes sediments from the western and southern parts of the basin, indicating potential provenances from intermediate to basic volcanic rock materials. The Baiyun Movement at the end of the O{1.gocene contributed to a large-scale subsidence in the deepwater area and also a northward retreat of continental shelf break, leading to deepening depositional environment in the basin. As a result, all the detrital zircon ages of the Upper O{1.gocene strata from Wells X28, L1., and L21.share a similar distribution, implying the possible control of a common source {1.ke the Zhujiang River. During the Miocene, whereas sediments in the northern area were mainly sourced from the Zhujiang River Delta, and those in the southern deepwater area continued to be affected by basic volcanic activities, the Dongsha Up{1.ft could have contributed as the main source to the eastern area.

关键词： geochemistry zircon U-Pb age provenance South china Sea Baiyun deepwater area

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The evidence for the existence of methane seepages in the northern South china Sea:abnormal high methane concentrations in bottom waters

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Acta Oceanologica Sinica 2008年第6期27卷 62-70页

作者： YIN Xijie ZHOU Huaiyang YANG Qunhui WANG Hu chen Jian Guangzhou Institute of Geochemistry Chinese Academy of Sciences Guangzhou 510640 China Graduate School Chinese Academy of Sciences Beijing 100049 China State Key laboratory of {1. geology Tongji University Shanghai 200092 China Third Institute of Oceanography State Oceanic Administration Xiamen 361005 China

The methane concentration of water samples at five stations collected by the CTD rosette water sampler in the areas of southwest Dongsha Islands and the Xisha Trough was analyzed by the gas-stripping method on aboard ship. It shows abnormal high methane concentrations in near bottom water samples at three stations. In the southwest Dongsha Islands area, the methane *** of 4. 25 and 1.. 64 nmol/dm3 occurs in near bottom water samples at Stas E1.5A and El06, respectively. In the Xisha Trough area, the high methane concentrations of 5. 1., 8.48 and 8.70 nmol/dm3 in water depths of 1.750, 1.900 and 2 050 m, respectively, have been observed at Sta. F41.. It is believed that the abnormal high methane concentrations are generated from the leakage of methane from sediments. Combining with previous geophysical and geochemical data from these two areas, this was probably related to the sub{1. gas hydrates decomposition and cold seep system. In May 2007, gas hydrate samples were successfully obtained by the drilling in the Shenhu Sea area located in the southwest Dongsha Islands area. It is called for further drilling surveys to confirm the existence of gas hydrate and cold seep system in the Xisha Trough as early as possible.

关键词： gas hydrates bottom sea waters methane plume

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Spatiotemporal variations of deep-sea sediment components and their fluxes since the last glaciation in the northern South china Sea

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Science china Earth Sciences 2017年第7期60卷 1368-1381页

作者： ZHAO ShaoHua liU ZhiFei {1. Quan WANG XingXing SHI JiangNan JIN HaiYan liU JingJing JIAN ZhiMin State Key laboratory of {1. geology Tongii University Shanghai 200092 China

Sediment components and their fluxes of Cores MD1.-3428(water depth: 903 m), MD1.-3433(water depth: 21.5 m),and MD1.-3434(water depth: 2995 m), obtained along a transect on the continental slope of the northern South china Sea, have been conducted to reveal the spatiotemporal variations and the control{1.ng factors of the sediment components and of their *** show that deep-sea sediments in the northern South china Sea are composed mainly of terrigenous(59–89%) and carbonate(6–38%) particles, with minor components of opal(1.6–9.4%) and organic matter(0.7–1.9%). Fluxes of terrigenous and carbonate particles reach up to 2.4–21.8 and 0.4–6.5 g cm–2 kyr–1. respectively, values that are one to two orders of magnitude higher than the fluxes of opal and organic matter. Temporal variations of the percentages and fluxes of deep-sea sediment components have displayed clear glacial-interglacial cyc{1.city since the last glaciation. Terrigenous, opal, and organic matter percentages and their fluxes increas clearly during marine isotope stage 2, while carbonate percentages and fluxes show an opposite variation pattern or are characterized by an unremarkable increase. This imp{1.es that deep-sea carbonate in the South china Sea is affected by the dilution of terrigenous inputs during the sea-level lowstand. With increasing water depth along the transect, the terrigenous percentage increases but with largely decreased fluxes. Both the percentage and flux of carbonate decrease, while the percentages and fluxes of opal and organic matter display much more comp{1.cated variational features. The spatiotemporal variations of deep-sea sediment components and of their fluxes since the last glaciation in the northern South china Sea are strongly controlled by sea-level fluctuations. Simultaneously, terrigenous supply associated with monsoonal rainfall, marine primary productivity,and the dilution effect between terrigenous and biogenic particles, also play interconnected roles in th

关键词： Sediment component Accumulation rate Spatiotemporal variation Last glaciation Sea-level fluctuation South china Sea

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Evolution of the East china Sea sedimentary environment in the past 1. kyr: Insights from tetraethers-based proxies

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Science china Earth Sciences 2016年第5期59卷 927-938页

作者： GE HuangMin ZHANG ChuanLun VERSTEEGH Gerard J.M. chen {1.ng{1.ng FAN DaiDu DONG {1.ang {1.U JingJing State Key laboratory of {1. geology Tongji University Hadal Science and Technology Research Center (shanghai Engineering Research Center of Hadal Science and Technology) Shanghai Ocean University Heisenberg Group on marine Kerogen Center for Marine Environmental Sciences (MARUM) Bremen University

We reconstruct the environmental evolution of the East china Sea in the past 1. kyr based on glycerol dialkyl glycerol tetraethers(GDGTs) in a sediment core from the subaqueous Yangtze River Delta. Two primary phases are recognized. Phase I(1..8–8 cal kyr BP) reflects a predominantly continental influence, showing distinctly higher concentrations of branched GDGTs(averaged {1. ng/g dry sediment weight, dsw) than isoprenoid GDGTs(averaged 36 ng/g dsw), high BIT index(branched vs. isoprenoid tetraethers) values(>0.78) and a fluctuating GDGT-0/crenarchaeol ratio(R_(0/5), varied from 0.52 to 3.81.. Within this interval, temporal increases of terrestrial and marine influence are attributed to Younger Dryas(YD)(ca. 1..9–1..2 cal kyr BP) cold event and melt-water pulse(MWP)-1.(1..5–1..1.cal kyr BP), respectively. The prominent transition from 8 to 7.9 cal kyr BP shows a sharp decrease in BIT index value(likely reflects the flooding history of the region. The TEX_(86)(Tetra Ether Index of tetraethers consisting of 86 carbons) proxy is not applicable in phase I because of an excess terrestrial influence; but it seems to be valid for revealing the annual SST in phase II(21.6±0.9°C, n=49). In contrast, the MBT'/CBT(Methylation of Branched Tetraethers and Cyclization of Branched Tetraethers) proxy appears to faithfully record the annual mean air temperature(MAT)(1..3±0.63°C, n=68) and presents an integrated signal over the middle and lower Yangtze River drainage basin.

关键词： GDGTs Proxies Sedimentary environment evolution Holocene East china Sea

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南黄海海相地层速度的提取及其特征

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海洋地质与第四纪地质 2018年第3期38卷 175-185页

作者：施剑陈春峰陈建文刘俊雷宝华中国地质大学(武汉)地球物理与空间信息学院武汉430074 中国地质科学院北京100037 海洋国家实验室海底矿产资源评价与探测技术功能实验室青岛266071 中国地质调查局青岛海洋地质研究所青岛266071 中海石油(中国)有限公司上海分公司上海200335

南黄海盆地特殊的地震地质条件导致准确获得海相地层速度存在困难。基于本区的多道地震资料,联合使用多数据质控速度分析、初至波层析反演及层控网格层析反演3种方法,提取出了较为可靠的海相中-古生界速度信息。结合提取的地震速度及下... 详细信息

南黄海盆地特殊的地震地质条件导致准确获得海相地层速度存在困难。基于本区的多道地震资料,联合使用多数据质控速度分析、初至波层析反演及层控网格层析反演3种方法,提取出了较为可靠的海相中-古生界速度信息。结合提取的地震速度及下扬子区已有钻井信息,总结了南黄海主要海相地层的速度分布。本区海相地层速度整体呈高低相间分布结构,存在速度的突变和倒转。海相下构造层速度高,不同地层间速度差异较小。由于海相下构造层无钻井资料约束,获得的速度信息仍存在不确定性。

关键词：地震波速速度谱层析反演海相地层南黄海盆地

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