不同顶管组合方式的管幕冻结温度场模型试验

拱北隧道作为港珠澳大桥珠海连接线的关键性工程, 在国内外首次成功运用了管幕冻结技术。以此为背景, 为更加全面地掌握饱和软土地层中管幕冻结温度场的分布特点, 开展了不同顶管组合方式下的管幕冻结温度场模型试验研究。试验结果表明： 各测点温度曲线在积极冻结期前4 h急剧下降, 随后逐渐减缓, 降至砂土冰点后趋于平稳, 三种布管方式均满足冻结设计要求; 冻结管中低温盐水提供的冷量首先传递给顶管管壁, 再以“面”的形式均匀地传递给周围土体; 积极冻结21 h后, 采用四根空顶管组合的C区冻结壁竖向范围最大, 空管管壁正上方冻结壁平均厚度约为105 mm, 在满足管幕刚度设计要求的前提下, 可采此布管方式以达到快速形成冻结帷幕的目的。限位管开启后的4 h内, 实顶管中线垂直距离100 mm范围内测点温度曲线虽有明显回升但仍维持在冻土冰点以下, 超出此范围后温度变化影响逐渐减弱, 且顶管间冻结壁稳定存在, 表明限位管在满足管间有效封水的条件下, 能在一定范围内起到定向限制地层冻胀的作用。优化后的双圆形冻结管在满足冻结设计要求的同时, 更加便于安装且经济环保。     

基于可达性分析的高速公路投资空间溢出效应

基于可达性分析方法,探讨新建交通基础设施投资给邻近地区带来的空间溢出效应及其特征。以2005-2009年江苏省各市新建高速公路为例,通过GIS 空间分析模型、经济潜力指数及情景分析法,得到江苏各市新建高速公路投资建设带来的经济潜力收益值,并在此基础上应用平均溢出效应模型得到区际可达性溢出矩阵,结合各地交通投资与溢出效应货币化模型将区际溢出矩阵货币化,得到区际交通投资矩阵来重新分配各市交通投资成本,以此表示交通投资空间溢出效应。结果显示：可达性溢出效应传递基本上随着到新建高速公路距离增加而衰减,然而各市新建高速公路在邻近地区产生非均衡性的溢出效应,新建高速公路方向、区位以及高速公路网络体系影响了溢出效应强度分布。中间地区交通建设更有助于推动边缘地区可达性水平提高,其交通投资溢出效应普遍比边缘地区规模大,溢出投资占实际投资比重高,区域边缘地区多数为溢出效应的输入地区。     

Modeling reactive transport in non-ideal aqueous–solid solution system

The numerical simulation of reactive mass transport processes in complex geochemical environments is an important tool for the performance assessment of future waste repositories. A new combination of the multi-component mass transport code GeoSys/RockFlow and the Gibbs Energy Minimization (GEM) equilibrium solver GEM-Selektor is used to calculate the accurate equilibrium of multiple non-ideal solid solutions which are important for the immobilization of radionuclides such as Ra. The coupled code is verified by a widely used benchmark of dissolution–precipitation in a calcite–dolomite system. A more complex application shown in this paper is the transport of Ra in the near-field of a nuclear waste repository. Depending on the initial inventories of Sr, Ba and sulfate, non-ideal sulfate and carbonate solid solutions can fix mobile Ra cations. Due to the complex geochemical interactions, the reactive transport simulations can describe the migration of Ra in a much more realistic way than using the traditional linear K_D approach only.     

汶川地震(Ms8.0）地表建筑体变形特征及其构造意义

通过汶川地震震区大量的实地考察已证实沿着早先活动断裂主要发育了两条地表破裂带：一条是沿着映秀－北川断裂产生的逆冲伴随右旋走滑破裂带,长275km,最大垂直位移达11m,水平位移达12m; 另一条纯逆冲性质的破裂带,沿着灌县－安县断裂发育,最大垂直位移达4m。活动断裂之上的地表破裂带是野外工作中确定地震断裂性质的重要现象。另外,在活动断裂相邻区域和远离区域的路面以及建筑体还大量存在变形现象。通常沿活动断裂产生的地表破裂是典型的同震破裂,相邻区域的地表路面及建筑体发育的变形属于次生变形,远离区域发育的变形则属于震后变形。对次生变形和震后变形测量数据的应用容易影响活动断裂特征的确定和性质的判断,因为路面等建筑体上的挤压拱起、叠置以及水平错断等现象多是受到地震过程中通过断裂活动突然释放的巨大能量作用在局部地表建筑体产生的变形。但是,分布广泛的挤压现象暗示了区域上挤压应力场环境,有利于地表同震破裂位置的推测及地震断裂性质的判断。     

Evidence for Tibetan Plateau Uplift in Qaidam Basin before Eocene-Oligocene Boundary and Its Climatic Implications

Geometry analysis of the Hongsanhan (红三旱) Section in the northwestern Qaidam basin illustrates the typical growth strata in the Xiaganchaigou (下干柴沟) Formation. The age and sedimentation rates of the Xiaganchaigou and the Shangganchaigou (上干柴沟) formations were determined by the high-resolution magnetostratigraphy. This result shows that the growth strata began to form at ca. 38.0 Ma and increased sedimentation rates occurred at ca. 37.0 Ma. The uplift of the Tibetan plateau before the Eocene-Oligocene boundary is confirmed, which enables us to better understand the relationship between climatic changes and the tectonic uplift. This uplift event could have resuited in the regional drying by blocking the moisture and contributed to the Eocene-Oligocene boundary global cooling event due to the declining atmospheric CO2 concentrations by increased weathering of the mountains.     

Magneteostratigraphy of Yumen Conglomerate in the Yumushan Region and Its Implication for Deformation and Uplift of the NE Tibetan Plateau

青藏高原新生代变形隆升过程是青藏高原新生代构造演化研究的热点问题,地处于高原东北部祁连山东北缘的榆木山是研究高原变形隆升时空过程的关键研究区之一.榆木山地区发育了一套粗砾相磨拉石——玉门砾岩,磁性地层研究表明其底部地质年代约为3.58 Ma.经古水流、磁化率、野外考察等推断玉门砾岩可能主要为构造隆升的产物,同时在榆木山地区还发育3个与玉门砾岩有关的不整合面,其跨越年龄分别约为:5.23～3.58Ma、2.88～2.58 Ma和＜1.77～0.8 Ma.综合分析认为该地区变形隆升不晚于3.58 Ma,之后至少经历两期构造变形隆升,该结果比北东向分步生长变形隆升模式推测的变形隆升时间明显早约1Ma,应该是对高原东北部青藏-昆黄运动的响应结果.     

Comments on “Two-dimensional concentration distribution for mixing-controlled bioreactive transport in steady-state” by O.A. Cirpka and A.J. Valocchi

In this comment we present a re-analysis of the analytical solution presented by Cirpka and Valocchi for steady-state concentrations of dissolved bioreactive compounds and bacterial biomass in porous media. We discuss the validity range of the analytical solution. In particular, the criterion used to determine the sustainability of biomass is revisited. This re-analysis shows that the ω$\omega$ criterion used by Cirpka and Valocchi is only a necessary but not a sufficient criterion to determine the bioreactive zones. As a consequence, the analytical solution does not provide the exact distribution of compounds throughout the domain, but can serve as upper or lower boundaries for species concentrations at a given location. These conclusions are supported by the simulation results obtained from an established reactive transport model.     

沉积物的地震及古地震效应*

古地震是依据地层中保留的沉积物变形记录而确定的。系统归纳总结地震诱发沉积物变形将为古地震研究提供理论基础,也有助于野外调查辨认这些记录。作者提出了一个初步的、供讨论与补充修正的地震触发沉积物变形分类的方案。变形的成因机制是分类的基础。这些特殊沉积物变形主要与地震有关,但其中一些变形往往也受其他多种因素的影响,因此要确定地震成因变形必须详尽研究相关的区域地质背景构造。     

Types of Enclaves and Their Features and Origins in Intermediate-Acid Intrusive Rocks from the Tongling District, Anhui Province, China

Enclaves in intermediate-acid plutons from Tongling can be divided into three types: xenoliths, relics and magmatogenic enclaves. The magmatogenic enclaves consist of cumulates, micrograined dioritite mixtite and dioritic chilled border enclaves. Petrologically, relics with eyed and meta-poikilitic texture are characterized by high content of biotite (>80%) and low content of cordierite and grossular. The cumulates with accumulate texture consist of a great amount of pyroxene, hornblende and minor spinel and phlogopite. The micrograined dioritic mixtite is composed of more hornblendes and feldspar and less needle apatites and an ellipsoid basic core included in plagio-clase. The chilled border enclaves have the same mineral association, but more dark minerals than the host rocks consisting of plagioclase, quartz, alkaline feldspar, hornblende and biotite. Geochemically, the relics exhibit high REE content (455.8×10-6) and high ratio of LREE/HREE, more obvious Eu negative anomaly and are rich in Cr and     

新疆境内塔拉斯-费尔干纳断裂早侏罗世走滑的古地震证据

在野外考察过程中,于新疆乌恰地区早侏罗世康苏组沼泽相砂岩层中,发现并识别出软沉积物液化变形层,变形包括负载构造,球-枕构造及卷曲变形构造。通过模拟试验的对比研究认为,该软沉积物变形机制与液化作用有关,触发沉积物液化的动力是古地震,并且根据地震震级与液化最大震中距的关系,推测出造成早侏罗世软沉积物变形的里氏地震震级为6相似文献