桥梁墩台施工变形观测与分析

在桥梁施工过程中经常需要对桥梁墩台进行沉降观测。本文结合某大桥墩台各施工期间的多次沉降观测，讨论了桥梁墩台施工检测过程中控制网布设，及其沉降规律，为较大型桥梁的施工或桥梁拓宽拼接提供较为科学的沉降规律，也为桥梁墩台灌注桩抛高提供依据。     

Evaluation of substructuring method for seismic soil-structure interaction analysis of bridges

This paper evaluates the commonly used substructuring method for analysis of bridge systems where the bridge is divided into two sub-systems: the bridge superstructure and the substructure including the pile foundations, abutments, and soil. Modeling of the soil-structure interaction (SSI) in the system is simplified by replacing the pile foundations, abutments, and soil with sets of independent equivalent linear springs and dashpots at the base of the superstructure. The main objective of the paper is to examine how well the substructuring method simulates the seismic response of a bridge system. The baseline data required for the evaluation process is derived from analyzing a fully-coupled continuum bridge model, already validated for the instrumented two-span Meloland Road Overpass. The same bridge system is also simulated using the substructuring method. The results from both approaches are compared, and it is shown that the differences between them can be significant. The substructuring method consistently overestimates the pier base shear forces and bending moments and the pier top deflections. Moreover, the spectral response of the bridge structure is mispredicted. The analyses are repeated for a three-span bridge system subjected to several ground motions, leading to a similar observation as before. Hence, the current state of practice for simulating seismic SSI in bridges using the substructure model is shown to be too simplified to capture the major mechanisms involved in SSI.     

云南腾冲黑空山、马鞍山和打莺山火山粗安岩显微结构特征及其火山学意义

火山喷发物记录了岩浆的整个活动历史,对火山喷发物的研究可以了解大量的岩浆活动特征信息。本文对腾冲火山区的三座全新世火山——黑空山、马鞍山和打莺山火山熔岩进行了详细的研究,包括熔岩和斑晶的成分、显微结构特征和斑晶的晶体大小分布(CSD)分析。研究发现,黑空山、马鞍山和打莺山火山熔岩以粗安岩为主,三座火山粗安岩中的斑晶成分范围接近,但它们的显微结构特征具有一定的差异,反映了不同的岩浆环境,推测来自不同的岩浆囊。黑空山粗安岩中斜长石斑晶的CSD曲线呈微上凹形,反映了小规模的岩浆混合作用。马鞍山和打莺山粗安岩的微斑晶CSD曲线呈很好的线性关系,说明微斑晶形成时的环境相对稳定,推测这些微斑晶是在岩浆上升过程中,停留在地壳的某处并形成一个小型的岩浆囊后受围岩的冷却作用形成。根据以上的分析,认为腾冲火山区下在横向和纵向上均至少存在两个岩浆囊。     

北祁连山寒山金矿成矿时代讨论

寒山大型金矿是近年来在北祁连山西段发现的与基性火山岩有关的构造蚀变岩型金矿.作者利用Rb-Sr同位素方法测得寒山金矿的成矿时代为339 Ma,属华力西期.指出寒山金矿的成矿时代应为(303～339)Ma,有多期热液叠加,多期成矿作用.因此,作者认为寒山金矿的热液很可能是青山斜长花岗岩(370±25Ma)、寒山辉长岩(347.1±6.4Ma)共同提供的.由于该区有较多的中酸性岩体存在,现成矿时代的确定对于该区在寻找华力西期-加里东晚期蚀变岩型金矿具有重要意义.     

陕西周至马鞍桥金矿床地质特征及成因分析

阐述了马鞍桥金矿区的地层、构造、岩浆岩特征，总结了金矿床矿体、矿石及化学成分的基本特点，分析了围岩、剪切构造带、中酸性岩体与金矿化的关系，认为马鞍桥金矿的成矿物质来源于围岩泥盆系罗汉寺岩群，成矿作用严格受脆性剪切变形变质带控制，剪切同期中酸性岩浆活动为含矿热液上升迁移和富集成主矿体提供了必要的热能。含矿热液与韧性剪切变质岩之间交代作用的强度是导致金的沉淀和富集形成金矿体的关键。矿床为韧性剪切带蚀变岩型金矿。     

Cretaceous amber inclusions of Spain and Myanmar demonstrate early diversification and wide dispersal of Cephenniitae (Coleoptera: Staphylinidae: Scydmaeninae)

The taxonomic status of previously misplaced species of an ant-like stone beetle from Spanish amber (Albian) is clarified. Specimens of Kachinus magnificus (originally placed as incertae sedis within Scydmaenitae) were re-examined and their characters were found different from those of the type species of Kachinus from Myanmar amber. Consequently, Archeutheia gen. nov. is proposed to accommodate the Spanish species, resulting in Archeutheia magnifica comb. nov. Moreover, in a comprehensive phylogenetic analysis Archeutheia was placed as a sister group to extant Eutheia, within the tribe Eutheiini of Cephenniitae. A specimen of an undetermined genus from Myanmar amber clearly belonging in Cephenniini is also recorded. Both taxa represent the first definite Cretaceous Cephenniitae, a supertribe whose recent members are distributed on all continents but are especially diverse in the Oriental and East Palaearctic regions. This finding demonstrates a diversification of two presently most species-rich tribes of Cephenniitae already in Early Cretaceous. Archeutheia is strikingly similar to the extant species of Eutheia and Veraphis, showing male dimorphic characters (modified protrochanters) and antennal cavities characteristic of Palaearctic Eutheiini. This fact suggests a long morphological stability in the supertribe. A previously proposed hypothesis of an early presence of the Cephenniitae in the Northern Hemisphere is for the first time supported by the fossil record, and the palaeolocalities (western Europe and Southeast Asia) demonstrate a wide distribution of Cephenniitae in the Cretaceous and an early split of its ancestral lineage.     

Honvang serpentinite body of the Song Ma fault zone, Northern Vietnam: A remnant of oceanic lithosphere within the Indochina–South China suture

The Honvang serpentinite body in the Song Ma fault zone consists mainly of massive serpentinite, altered gabbro and rare chromitite. The serpentinite preserves relict chromian spinel with rare olivine inclusions. The compositional relationship between the Fo content of olivine (Fo_90–92) and Y_Cr [atomic ratio Cr / (Cr + Al) = 0.43–0.44] of chromian spinel suggests that the original peridotite was spinel-bearing lherzolitic harzburgite. Chromitite is typically a high-Al type, consisting of chromian spinel with Y_Cr = 0.43–0.44. Saussuritized fine-grained gabbros display nearly flat rare earth element patterns, suggesting MORB-like affinity. Considering this petrotectonic information, we suggest that the serpentinite body of the Song Ma fault zone represents a remnant of paleo-oceanic lithosphere between the Indochina and South China blocks. The lherzolitic harzburgite may have formed in an environment with low degrees of melt depletion in a slow-spreading setting similar to some Tethyan paleo-oceanic lithospheres.     

是可疑化石还是化石：一论洛南生物群

当前人们普遍认为地球生物史上最早的后生动物是伊迪卡拉动物群，由软躯印痕化石组成，多数学者认为是刺胞动物，年代约６￣７亿年前，而多门类骨骼化石的出现则是寒武系底界的标志。震旦晚期虽有少量报道，但其层位不低于陆山陀组。但是，陈耳化石因其年代古老（１２亿年）而又显示多样的贝壳或骨骼的性质，学术界反映谨慎，认为将其归为可疑化石较为可靠。笔者从化石的保存特征、形态组合面貌、有机与无机成分分析和结构构造研究等     

考虑梁体—挡块碰撞效应的桥梁地震响应数值计算

地震中桥梁梁体和挡块之间的碰撞是导致挡块破坏的直接因素.为定量研究由碰撞带来的横桥向地震响应的变化,采用Kelvin接触单元模型和SSH法数值计算方法,推导了考虑梁体—挡块碰撞效应的桥梁地震响应的数值计算方法和步骤,并用MATLAB编制了相应程序.通过对比计算结果和有关文献的试验数据可以看到,本文提出的计算方法计算效率高,结果准确.最后通过一个例子说明了本方法的实用性.     

Influence of large woody debris on sediment scour at bridge piers

Large woody debris(LWD) reduces the flow area,deviate the flow and increases the velocity in correspondence of the bridge pier,therefore increases the maximum scour hole depth and accelerates sediment removal.Logs and drifts accumulated on bridge piers are of different dimensions.According to logs characteristics and river morphology,drift accumulations can either extend downstream the bridge pier or they can accumulate totally upstream.This paper aims to analyze the effect of drift accumulation planimetry on bridge pier scour.The experimental investigation has been carried out at the PITLAB hydraulic centre of Civil Engineering Department,University of Pisa,Italy.Drift accumulation was characterized by different relative longitudinal lengths,flow area occlusions,length of longitudinal drift and downstream planimetrical positions relative to the pier center.The experimental investigation has been carried out in clear-water conditions.Several pier sizes,channel widths and sediment materials have been tested.Maximum scour hole in presence of drift accumulation have been compared to the maximum scour hole for an isolated pier.Finally,data were compared with previous literature findings,which highlight the effect of the downstream extension of drift accumulation on bridge pier scour.New relationships have been proposed to predict the effect of drift accumulation on bridge pier scour,both in terms of relative maximum scour and temporal scour evolution.