浙江拔茅破火山岩浆作用：开放体系多机制复合演化   总被引：1，自引：3，他引：1  

薛怀民  陶奎元等 《岩石学报》2001,17(3):403-412

拔茅火山杂岩的成分变化范围广泛，包括玄武质，玄武粗安质，粗面安山质，粗面英安质，流纹英安质到流纹质和高硅流纹质岩石都有，它们不是由单一母岩浆演化而来，也不是由单一岩浆房喷发形成的，而是来自多种类型的岩浆房，并经历过复杂的演化过程，为开放体系多机制复合演化，其中早期双峰式基性端元是由上地幔部分熔融形成的，而酸性端无则是地壳物质边熔融边喷发（分离熔融）的结果，作为火山杂岩主体的粗面英安质岩石，其岩浆是在高位主岩浆房内由玄武质岩浆与流纹英安质岩浆混合形成的，发生混合的流纹英安质与玄武质岩浆的比例为57：43，而粗面安山质岩浆则是溶部岩浆房内由玄武质岩浆分离结晶形成的，晚期侵出－侵入的流纹英安质岩穹和高硅流纹斑岩株则分别代表高位次级岩浆房的成分及其硅质帽。  相似文献   

人工快速渗滤复合系统处理洗浴污水的试验研究   总被引：22，自引：0，他引：22  

张金炳  陈鸿汉  钟佐燊  马生明  张达政  宁志勇 《水文地质工程地质》2001,28(6):30-32,42

针对传统污水快速渗滤土地处理系统水力负荷低，占地面积大的弱点，提出了采用人工砂和天然砂作为渗滤介质建立复合系统的试验方案，并以洗浴污水为研究对象进行了5个月的室内试验研究。结果表明，复合系统具有较高的水力负荷和较好的去污效果，其COD，BOD5，SS和阴离子洗涤剂（以MBAS代表）的平均去除率分别为86.25%,86.75%,98.95%和90.86%。处理出水中COD，BOD5，SS和阴离子洗涤剂的平均浓度分别为17.30,5.84,0.3和0.18mg/l。  相似文献   

Emplacement and arrest of sheets and dykes in central volcanoes   总被引：1，自引：0，他引：1  

Agust Gudmundsson   《Journal of Volcanology and Geothermal Research》2002,116(3-4)

Sheet intrusions are of two main types: local inclined (cone) sheets and regional dykes. In Iceland, the inclined sheets form dense swarms of (mostly) basaltic, 0.5–1 m thick sheets, dipping either at 20–50° or at 75–90° towards the central volcano to which they belong. The regional dykes are (mostly) basaltic, 4–6 m thick, subvertical, subparallel and form swarms, less dense than those of the sheets but tens of kilometres long, in the parts of the volcanic systems that are outside the central volcanoes. In both types of swarms, the intrusion intensity decreases with altitude in the lava pile. Theoretical models generally indicate very high crack-tip stresses for propagating dykes and sheets. Nevertheless, most of these intrusions become arrested at various crustal depths and never reach the surface to supply magma to volcanic eruptions. Two principal mechanisms are proposed to explain arrest of dykes and sheets. One is the generation of stress barriers, that is, layers with local stresses unfavourable for the intrusion propagation. The other is mechanical anisotropy whereby sheet intrusions become arrested at discontinuities. Stress barriers may develop in several ways. First, analytical solutions for a homogeneous and isotropic crust show that the intensity of the tensile stress associated with a pressured magma chamber falls off rapidly with distance from the chamber. Thus, while dyke and sheet injection in the vicinity of a chamber may be favoured, dyke and sheet arrest is encouraged in layers (stress barriers) at a certain distance from the chamber. Second, boundary-element models for magma chambers in a mechanically layered crust indicate abrupt changes in tensile stresses between layers of contrasting Young’s moduli (stiffnesses). Thus, where soft pyroclastic layers alternate with stiff lava flows, as in many volcanoes, sheet and dyke arrest is encouraged. Abrupt changes in stiffness between layers are commonly associated with weak and partly open contacts and other discontinuities. It follows that stress barriers and discontinuities commonly operate together as mechanisms of dyke and sheet arrest in central volcanoes.  相似文献   

Plasticity model for sand under small and large cyclic strains: a multiaxial formulation   总被引：1，自引：0，他引：1  

Achilleas G. Papadimitriou  George D. Bouckovalas 《Soil Dynamics and Earthquake Engineering》2002,22(3):15

This paper presents the multiaxial formulation of a plasticity model for sand under cyclic shearing. The model adopts a kinematic hardening circular cone as the yield surface and three non-circular conical surfaces corresponding to the deviatoric stress ratios at phase transformation, peak strength and critical state. The shape of the non-circular surfaces is formulated in accordance with the experimentally established failure criteria, while their size is related to the value of the state parameter ψ. To simulate cyclic response under small and large shear strain amplitudes without a change in model parameters, it was found necessary to introduce: (a) a non-linear hysteretic (Ramberg–Osgood type) formulation for the strain rate of elastic states and (b) an empirical index of the effect of fabric evolution during shearing which scales the plastic modulus. This index is estimated in terms of a macroscopic second-order fabric tensor, which develops as a function of the plastic volumetric strain increment and the loading direction in the deviatoric plane. Comparison of simulations to pertinent data from 27 resonant column, cyclic triaxial and cyclic direct simple shear tests provide a measure for the overall accuracy of the model.  相似文献   

重庆轻轨大堰基地挡土墙变形原因分析     

胡志耘  周庆人  成维新  李成敏  刘世杰 《水文地质工程地质》2002,29(6):64-65,68

通过观察挡墙变形裂缝和分析测量数据，对大面积堆载引起的地基不均匀沉降的原因进行了阐述，指出填土地基在压实处理时的不均匀性，造成局部地基强度偏低，雨季地表水体下渗，降低了土体强度是引起挡墙局部不均匀沉降的主要原因。根据实际情况，提出了立即封闭地表，减少水体下渗，适当增加挖孔桩配筋量，建立观测网、实施有效监测的处理措施。  相似文献   

喷粉桩复合地基的群桩效应的探讨及其载荷试验研究   总被引：3，自引：1，他引：3  

潘纪顺  吕芝全等 《地质与勘探》2002,38(2):85-87

从复合地基的基本原理出发，讨论了群桩效应现象在复合地基存在的可能性，并通过喷粉桩复合地基的单桩，多桩复合地基载荷试验的对比研究，揭示了复合地基中的群桩效应现象。  相似文献   

THE USE OF THREE-DIMENSIONAL EOF TECHNIQUE TO ANALYZE CLIMATIC CHARACTERISTICS OF PRECIPITATION IN CHINA   总被引：1，自引：0，他引：1  

Su Bingkai  Xu Guiyu  Fu Congbin 《Acta Meteorologica Sinica》1991,5(5):617-627

In this paper,a three-dimensional EOF technique is used to analyze the precipitation and its anomalyover whole China and sanely selected regions,i.e.the Changjiang Valley,the Huanghe Valley and the Southpart of China in last decades.The structural characteristics of spacial distribution,seasonal and interannualvariation are revealed.As a better technique than 2-D EOF,the 3-D EOF alse provides a way to expose interac-tions between temporal and spacial variations.  相似文献   

黄石台ORBES-81型伸缩仪观测结果的调和分析及海潮改正   总被引：1，自引：1，他引：1  

周坤根  B. Ducarme  胡延昌 《地球物理学报》1991,(4)

本文对黄石台ORBES-81型石英伸缩仪的应变固体潮观测资料作了分析计算,其调和分析结果为:对O_1波,振幅因子0.4219,相位滞后6°36＇;对M_2波,振幅因子0.4256,相位滞后-4°42＇.同时,讨论了海潮引起的负荷潮汐应变的改正问题.模拟计算发现负荷潮汐应变与体潮应变大致为同一量级,文中列出了海潮改正后的结果,并作了讨论.最后,对黄石台伸缩仪的架设方位作了评价.  相似文献   

初论安徽沿江地区成矿系统的深部构造-岩浆控制   总被引：15，自引：2，他引：13  

吴言昌  曹奋扬  常印佛 《地学前缘》1999,6(2):285-296

深部构造岩浆作用对长江中下游成矿带安徽沿江地区成矿系统的控制表现为：（１）地幔隆起带与成矿系统的总体地质背景的演变密切相关;（２）源于地幔隆起带不同部位（幔脊与幔坡）的原始岩浆,其生成方式和物质组成不尽相同,它们分别产生相应的不同岩浆岩系列和成矿亚带;（３）不同深度的构造岩浆房组成中心式网格式环带式“三层结构”,是控制区内不同岩浆岩系列及有关矿床集中分布的主要因素;（４）源于地幔隆起带脊部的碱性玄武岩浆,由于与下地壳物质发生的ＡＦＣ作用强度不同,形成了高钾钙碱性岩浆和橄榄安粗岩浆,分别与铜、金成矿亚系统和铁、硫成矿亚系统有关  相似文献   

建筑物负荷引起的地面和大地水准面形变研究     

汪孔政  王解先 《大地测量与地球动力学》1999,19(2):46-52

根据地球固体潮的有关理论,从物理大地测量的角度推导了建筑物负荷引起的地面和大地水准面的形变量的计算公式,并通过模拟计算,对单幢高层建筑、城市建筑群以及环形高架桥引起的附近地面和大地水准面的形变情况进行了定量分析。计算结果表明：建筑物负荷引起的地面垂直形变量要比水平形变量和大地水准面形变量大,城市建筑群引起的附近地面和大地水准面的形变量可达几毫米,对实际测量结果有一定的影响。  相似文献