Middle–Late Holocene Paleoclimate and Weathering History in the Norra Storfjället Mountains,Sweden: Deglacial Record and Soil Stratigraphy Applied to Neoglaciation in Lower Latitudes     

William C. Mahaney  Volli Kalm 《Geografiska Annaler: Series A, Physical Geography》2013,95(2):145-158

The retreat record of the Stabre Glacier into the Norra Storfjället mountains, after separation from the massive Tärnaån Glacier at some undetermined time in the Atlantic Chron, is documented by recessional moraines in the foreland. While poorly constrained by radiometric dating, the age of the middle group of moraines averages out to less than 4000 cal ¹⁴C yr BP, the older moraine group probably of Late Atlantic age, with the youngest deposits of Little Ice Age (LIA). Soils/paleosols range from Entisols (youngest) and Inceptisols (middle group) to mature Spodosols (outer group), existing either as single‐story profiles or within pedostratigraphic columns, buried pedons either surfaced with weathered glacial or mass wasted deposits. Some profiles exhibit convoluted properties which could place them in the Cryosolic order. The physico‐mineral‐chemical properties of soils/paleosols in recessional deposits across this sequence provide weathering indices over the mid to Late Holocene in the Swedish sub‐Arctic climate. It is likely the middle group of deposits represents stillstand of the retreating glacier offset by climatic deterioration with the onset of Early Neoglacial climate which altered the glacial mass balance, at least until termination of the LIA. Correlation to other alpine areas in the middle and tropical latitudes with similar records is attempted and discussed. While the Stabre Glacier disappeared after the LIA, the nearby Tärna Glacier remains extant on the land surface, a presumed result of slight elevation differences between the two cirques which affects storm tracks and resultant variations in glacial mass balances.  相似文献   

浅析钻孔灌注桩后注浆技术在河流冲积地层高层建筑中的应用     

邱玲智  王健 《中国勘察设计》2012,(8):77-80

介绍了钻孔灌注桩后注浆(桩端后注浆)在河流冲积地层高层建筑工程中的应用,并和钻孔灌注桩作了对比分析,通过现场单桩竖向抗压静载荷试验和现场低应变试验结果表明,钻孔灌注桩后注浆在此工程中是可行的,并具有较好的经济效益和社会效益。  相似文献   

Numerical simulation of the seismic behavior of self-centering steel beam-column connections with bottom flange friction devices     

Tong Guo  Lianglong Song  Guodong Zhang 《地震工程与工程振动(英文版)》2011,10(2):229-238

A new type of steel moment resisting frame with bottom ? ange friction devices (BFFDs) has been developed to provide self-centering capacity and energy dissipation, and to reduce permanent deformations under earthquakes. This paper presents a numerical simulation of self-centering beam-column connections with BFFDs, in which the gap opening /closing at the beam-column interfaces is simulated by using pairs of zero-length elements with compression-only material properties, and the energy dissipation due to f...  相似文献   

Petrology and Geochemistry of Post-Collisional Early Miocene Volcanism in the Karacada? Area (Central Anatolia, Turkey)     

Kür?ad ASAN  Hüseyin KURT 《《地质学报》英文版》2011,85(5):1100-1117

Early Miocene (ca.?21–18 Ma) volcanism in the Karacada? area comprises three groups of volcanic rocks: (1) calcalkaline suite (andesitic to rhyolitic lavas and their pyroclastics), (2) mildly-alkaline suite (alkali basalt, hawaiite, mugearite, benmoreite and trachydacite), and (3) a single trachyandesitic flow unit. Field observations, 40Ar/39Ar ages and geochemical data show that there was a progressive temporal transition from group 1 to 3 in a post-collisional tectonic setting. The calcalkaline suite rocks with medium-K in composition resemble those of subduction-related lavas, whereas the mildly-alkaline suite rocks having a sodic tendency (Na2O/K2O=1.5–3.2) resemble those of within-plate lavas. Incompatible element and Sr-Nd isotopic characteristics of the suites suggest that the lithospheric mantle beneath the Karacada? area was heterogeneously enriched by two processes before collision: (1) enrichment by subduction-related processes, which is important in the genesis of the calcalkaline volcanism, (2) enrichment by small degree melts from the astenosphere, which dominates the mildly alkaline volcanism. Perturbation of the enriched lithosphere by either delamination following collision and uplift or removal of the subducted slab following subduction and collision (i.e., slab breakoff) is the likely mechanism for the initiation of the post-collision volcanism.  相似文献   

苏通大桥超长桩桩底后压浆试验及效果          下载免费PDF全文

彭仕奇 《探矿工程》2011,38(11):54-58

在苏通大桥松散软弱的地层条件,实施超长（〉100 m）、超大（2.5 m）摩擦桩桩底后压浆工程,在我国是首次运用。结合工程实践,就压浆工程的设计、施工的技术要点进行全面介绍。通过对钻孔取样分析,指出浆液初凝时间地表实验与地下实际存在较大差异;通过施工体验,结合取样显示的浆液扩散渗透状况,提出可渗透地层以注浆量为控制参数,压力不列为控制参数的思路。  相似文献   

后注浆桩单桩极限承载力与其影响因素的分析     

杨子民  康宪泉  边胜宅 《岩土工程技术》2011,25(2):90-94

随着城市开发的速度越来越快,土地也日益变得珍贵,高层建筑得到了快速发展,为了满足高层建筑物越来越大的结构荷载的需要,桩长和桩直径也变得越来越大。在不大幅增加成本的前提下,后注浆技术提高了钻孔灌注桩的单桩承载力,并降低了建筑物的沉降,因此得到了更广泛的应用。简要介绍了后注浆工艺的承载力提高机理及几个工程实例,分析了注浆前后单桩极限承载力变化情况及部分影响因素,为普及应用积累了一些素材。  相似文献   

Regional Tectonic Transformation in East Kunlun Orogenic Belt in Early Paleozoic: Constraints from the Geochronology and Geochemistry of Helegangnaren Alkali-feldspar Granite   总被引：4，自引：0，他引：4  

LI Ruibao  PEI Xianzhi  LI Zhuochen  SUN Yu  PEI Lei  CHEN Guochao  CHEN Youxin  LIU Chengjun  WEI Fanghui 《《地质学报》英文版》2013,87(2):333-345

The Helegangnaren feldspar granite exposed in the eastern part of East Kunlun, is characterized by high concentrations of SiO2 and alkaline, low abundances of Fe, Mg and Ca, metaluminous-weak peraluminous. Trace elements analysis shows that the granite is depleted extremely in Ba, Sr and Eu, and rich in some large-ion lithophile elements and high field strength elements. Besides, the granite has high Ga contents, the values of 104(Ga/Al) vary from 2.50 to 2.77, which is mainly greater than the lower limit of A-type granites (2.6), and is higher than the I- and S-type granites’ average (2.1 and 2.28, respectively). Rare earth element (REE) is characterized by relatively high fractionations of light REE (LREE) and heavy REE (HREE) (LREE/HREE=9.3–13.60, (La/Yb)N=10.92–18.02), pronounced negative Eu anomalies (δEu=0.08–0.13), and exhibits right-dipping gull pattern. Major elements, rare elements and trace elements features show the granite is ascribed to A-type granite and A2 subtype in tectonic genetic type. They are plotted into post-collision or within-plate area in a variety of tectonic discriminations. Geological and geochemical data comprehensively suggest that the granite is formed in a post-collision extensive tectonic setting. Laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) zircon U-Pb dating yields a weighted mean age of 425?Ma, belonging to Middle Silurian, which is similar to the age of the post-collision geological events in the region. The differences of magmatic rocks in formation age, rocks assemblage and rocks series systematically indicate that the regional tectonic stress regime in the East Kunlun orogenic belt experienced a major transformation from compress to extension in Middle Silurianin, and the Helegangnaren feldspar granite intruded in the early stage of tectonic transformation.  相似文献   

Post‐quake decision analysis using dynamic programming     

Gee Liek Yeo  C. Allin Cornell 《地震工程与结构动力学》2009,38(1):79-93

We introduce a general decision analysis procedure based on stochastic dynamic programming in the post‐quake aftershock environment. The damage sustained by the building due to the mainsheet, the time‐varying aftershock rates and the potential for further damage progression in the post‐quake environment are all factors taken into consideration in the proposed methodology. This procedure enables the optimal decision after the mainshock to be selected based on the minimization of expected financial losses, subject to a constraint on a minimal level of individual life‐safety, using a consistent probabilistic framework to explicitly quantify the uncertainties in the variables. Copyright © 2008 John Wiley & Sons, Ltd.  相似文献   

Transition from arc‐ to post‐collision extensional setting revealed by K–Ar dating and petrology: an example from the granitoids of the Eastern Pontide Igneous Terrane,Araklı‐Trabzon,NE Turkey     

Sabah Yilmaz‐ahi&#x;n 《Geological Journal》2005,40(4):425-440

  相似文献   

Seismic self‐centering steel beam‐to‐column moment connections using bolted friction devices     

Keh‐Chyuan Tsai  Chung‐Che Chou  Chi‐Lon Lin  Pei‐Ching Chen  Sheng‐Jhih Jhang 《地震工程与结构动力学》2008,37(4):627-645

This paper first presents the force–deformation relationship of a post‐tensioned (PT) steel beam‐to‐column connection constructed with bolted web friction devices (FDs). This paper then describes the test program conducted in the National Center for Research on Earthquake Engineering, Taiwan, on four bolted FDs and four full‐scale PT beam‐to‐column moment connection subassemblies using the FDs. Tests confirm that (1) the hysteretic behavior of four bolted FDs is very stable, (2) the friction coefficient between the steel plate and the brass shim is about 0.34, (3) the proposed force–deformation relationships reasonably predict the experimental responses of the PT connections under cyclically increasing deformations up to a beam peak rotation of 0.05 rad, and (4) the decompression moments do not degrade as beam cyclic deformations increase. Copyright © 2007 John Wiley & Sons, Ltd.  相似文献