乌江下游岩溶地貌形态特征初探——以重庆武隆及其邻近地区为例

乌江下游为典型的亚热带岩溶中山峡谷地貌,主要以大型的岩溶峡谷、天生桥和大 的天坑以及大型溶洞、地下河及丰富多彩的次生沉积物为特征。本文主要分析了乌江下游的 岩溶个体形态特征及层状地貌面的岩溶形态组合特征,探讨了乌江下游岩溶地貌的演化过程,认为:（1）乌江下游地区的层状地貌分为两级夷平面、一级溶蚀面、五级水平溶洞和三 级阶地;（2）不同地区岩溶形态特征有明显差异:在鄂西期地面上,地面完整性较好,以低矮的峰丛和平坝、大的浅洼地相组合。山原期地面,不同地区岩溶形态组合特征有所差别: 在水系裂点以下地区,主要以峰丛-峡谷组合为主;河流裂点以上的上游地区,地面保存相对完整,为锥状峰丛、深洼地景观。盆地期溶蚀面以峰丛-槽谷、谷地为主。（3）乌江下游岩溶地貌的形成,经历了鄂西期、山原期、盆地期和峡谷期地貌演化阶段,并形成鄂西期、山原期岩溶夷平面、盆地期溶蚀面和深切峡谷。      

主TIN模式下面向拓扑的三维地质块体构建方法

当前普遍采用主TIN模式对层状地质体进行三维结构建模,然而在地质块体的构建方面还有所欠缺。考虑到由于尖灭、出露等现象引起的各地质块体间空间位置关系的复杂性,根据主TIN建模的特点,处理完地层相交与高程调整之后,通过对地层面中某个区域内的三角网与上下地层中对应区域内的三角网的重叠次数的不同,设置子面类型标记,从而分离出一个地层面中不同类型的子面。依据子面的类型可以快速建立地质块体与被引用的各子面之间的对应关系,最终自动分离出地层中的各个地质块体,并保证相邻块体在邻接处有唯一的公共子面,由此可建立各地质块体间的空间拓扑关系。     

浅部厚层粉性土分层中的一些问题

上海市沿江地区浅部粉性土具有厚度大、物理力学性质复杂多变的特征.文章就该层土的岩土工程分层进行专门讨论.     

层状岩体地下洞室变形影响因素分析

目前水电站建设多采用地下厂房,地下洞室围岩的变形特性是设计和施工关注的关键问题之一。采用有限元程序,结合正交试验设计方法,考虑多因素共同变化的影响,研究了各因素对地下洞室变形特性的影响显著程度．对各因素对洞室特征部位变形影响的显著性分别进行了排序。分析结果表明：拱顶位移受岩层厚度和洞室埋深的影响程度最大,左边墙中点位移受洞室埋深和洞室高度的影响最大．右边墙中点位移主要受洞室埋深的影响最大;洞室最大位移多发生在左边墙中点附近,受岩层厚度、洞室埋深、洞室高度的影响都非常显著。绘出了各因素对洞室特征部位位移的影响趋势。     

离心分层距离法——一种定量表征聚合物液体中矿物填料沉降性能的方法

研究聚合物等高粘度液体中矿物填料的沉降性能,可以为新型绝缘灌注胶以及矿物材料研究与应用提供科学依据,根据斯托克斯公式和离心沉降速度公式以及高速旋转离心实验特点,时自然沉降时间计算公式进行推导.并根据绝缘灌注胶特点以及不同粒度微晶白云母在环氧树脂中高速离心沉降实验,总结出一种能够对聚合物等高粘度液体中矿物填料的沉降性能进行快速定量表征的离心分层距离法;实验结果表明:微晶白云母在E-51环氧树脂中的沉降速度和分层比例都分别与其粒度大小呈正比关系,1 000目完全沉降(分层比例100%)需要7 068.7 d,其自然沉降速度为0.7×10-7mm·s-1,若要保持3个月内不发生明显的分层现象,应当采用1 000目或更细小的粒度.     

Transverse Dispersion of a Kinetically Sorbing Solute

A recursion formulation for the transverse spreading of a solute is developed, and under conditions of steady flow in a stratified aquifer, the transport of a linearly sorbing solute undergoing nonequilibrium sorption is studied. The effect of spatial variability in the velocity field and the sorption kinetics are modeled to see the combined effect of the two processes on the spreading of the solute injected at a point in the aquifer. The main result of this work is a transport model based on a discrete formulation that includes local dispersion and leads to nonasymptotic behavior in the spreading of the plume in a direction normal to the mean flow velocity.     

Spatial and temporal variation of picoplanktic cyanobacteria population in a density stratified estuary,and the introduction of a cellular gradient number

Spatial and temporal variations in the distribution of the marine picoplanktic cyanobacteria population and mixing conditions were found in the Ebro River estuary outflow to the Mediterranean Sea in Spain. Six sampling surveys were undertaken between July 1999 and February 2000 for distances up to 15 km from the river mouth. Measurements were taken of flow velocity, salinity, temperature, depth and picocyanobacteria (PCB) abundances. Gradient Richardson (Rig) and Reynolds (Re) numbers were determined to evaluate hydrodynamics. In summer, large values of Rig arise from the small flow rates, and small values of velocity shear between the surface fresh water layer and the bottom saline layer; conversely, in winter the large flow rates and attendant large velocity shears between the layers give rise to small values of Rig. Flow conditions in the fall are an intermediate case between the summer and winter cases. Vertical abundance distributions were resolved through the river water, interfacial region, and the bottom salt wedge; longitudinal gradients of PCB abundances were also resolved. Seasonal differences in the PCB abundance values were observed. Analysis of cell numbers (C) showed that the variable dC/dS, the dependence of cell number upon salinity gradient (dS) was critical. A non-dimensional number; the cellular gradient number (Cg) is introduced. Cg has useful biological interpretations that can potentially be included in ecological modeling. For example, Cg = 1 pertains to perfect adaptability of the organism to adjust to changing environmental conditions, whereas Cg = 0 describes total mortality. For a system with strong advection there is insufficient time for cells to adapt to the changing environment, and so those cell counts are unchanged. This is the case for the Ebro estuary in winter as advection of salinity (and hence PCB abundance) dominates the other loss processes for large flow rates.     

Three-Dimensional Lagrangian Simulation of Suspended Particles in the Neutrally Stratified Atmospheric Surface Layer

A three-dimensional (3-D) inertial particle – Lagrangian stochastic model for heavy particles in turbulent flows has been constructed. In this model, particle velocities are computed by adopting a non-linear drag law, while fluid velocity in the vicinity of a particle is calculated using a 3-D Langevin equation. Our model results have shown that the inclusion of the horizontal fluid velocity fluctuation computations and a non-linear drag law have an impact on the statistics of both fluid and particles when compared with our earlier one-dimensional (1-D) model with a linear drag law. Model results are compared and contrasted with Businger’s 1965 theory in terms of effective settling velocity.     

分层液化土中桩基侧向动力反应机理的试验研究

饱和砂土中的桩基侧向动力响应研究一直是岩土工程界与地震工程领域关注的热点,尤其是群桩侧向动力响应机制是需要重点研究的课题之一。基于振动台试验,通过输入2种不同的波形,采用FBG光栅传感系统对饱和砂土中的单桩与群桩侧向动力响应特性和典型测试点的桩土动力p—y滞洄曲线进行研究。研究结果表明：振动初期,单桩和群桩试验孔压增长不大,随后单桩孔压迅速上升,振动后期逐渐下降至0.5,而群桩孔压则上升缓慢;单桩试验土表加速度在振动初期逐步升高后又迅速降低,且加速度放大值略大于台面加速度值,群桩试验土表加速度在振动初期逐渐升高时就达到了最大,且随着孔压比的升高,加速度没有继续放大,而是逐渐减小,直到后期与单桩试验土表加速度重合;饱和砂土液化对单桩承台加速度和位移的影响较大,群桩承台侧向动力响应对液化的敏感程度略低于单桩承台;在振动输入和承台输入相同的条件下,液化后的群桩基础比单桩基础能更好地抵抗侧向力的作用。     

Petrogenesis of Mafic Inclusions in Rhyolitic Lavas from Narugo Volcano, Northeastern Japan

Mafic inclusions present in the rhyolitic lavas of Narugo volcano,Japan, are vesiculated andesites with diktytaxitic texturesmainly composed of quenched acicular plagioclase, pyroxenes,and interstitial glass. When the mafic magma was incorporatedinto the silica-rich host magma, the cores of pyroxenes andplagioclase began to crystallize (>1000°C) in a boundarylayer between the mafic and felsic magmas. Phenocryst rim compositionsand interstitial glass compositions (average 78 wt % SiO₂) inthe mafic inclusions are the same as those of the phenocrystsand groundmass glass in the host rhyolite. This suggests thatthe host felsic melt infiltrated into the incompletely solidifiedmafic inclusion, and that the interstitial melt compositionin the inclusions became close to that of the host melt (c.850°C). Infiltration was enhanced by the vesiculation ofthe mafic magma. Finally, hybridized and density-reduced portionsof the mafic magma floated up from the boundary layer into thehost rhyolite. We conclude that the ascent of mafic magma triggeredthe eruption of the host rhyolitic magma. KEY WORDS: mafic inclusion; stratified magma chamber; magma mixing; mingling; Narugo volcano; Japan