周原遗址及鱼国墓地出土青铜器锈蚀研究

运用等离子体发射光谱（ＩＣＰ）、Ｘ射线衍射（ＸＲＤ）、扫描电镜（ＳＥＭ）、Ｘ射线电子能谱 （ＥＤＡＸ）、金相分析等现代仪器,对从周原遗址及宝鸡国墓地所采集的青铜残片的成分、结构进行 了剖析,比较了合金基体与表面层的成分变化及表面的结构形态。结果表明腐蚀呈现明显电化学特 性,有选择性腐蚀,高锡相优先被腐蚀,在完全矿化层与合金基体之间形成部分腐蚀区的过渡层。因 自然腐蚀导致表面层富集Ｓｎ、Ｐｂ、Ｓｉ、Ｆｅ。氯离子可穿过腐蚀层沉积于表面层并向基体延伸。     

澄城刘家洼遗址出土青铜器腐蚀成因研究

刘家洼遗址出土大量珍贵的青铜器对研究春秋早期芮国历史具有重要价值,但由于青铜器受到长期腐蚀影响,其蕴含的部分信息可能发生损失。为研究刘家洼青铜器的工艺、保存状况与稳定性,揭示关中东部黄土塬区出土青铜器的土壤腐蚀特征,并为文物保护修复提供参考依据,本工作对刘家洼青铜器腐蚀成因进行综合研究。本工作利用金相显微镜观察、扫描电镜-能谱、X射线衍射、拉曼光谱等分析手段对刘家洼遗址出土6件青铜器样品的锈蚀物相与锈层结构进行表征。结果表明,青铜器腐蚀产物以赤铜矿、孔雀石以及白铅矿为主。部分青铜器表面存在浅绿色粉状腐蚀产物,但并非含氯腐蚀产物。刘家洼青铜器锈层结构自金属基体向外依次为过渡层、原始表面内非金属层、原始界面、原始表面外原位沉积层及扩散沉积层。原始界面内非金属层Cu/Sn值低于基体,表明基体内的铜元素腐蚀后向外迁移以及锡元素腐蚀后形成锡石原位沉积。原始界面外Cu/Sn比值显著高于原始界面内非金属层,表明外迁的铜离子在埋藏环境作用下沉积。本工作通过对青铜器附着土壤样品pH值、氧化还原电位以及离子色谱分析,结果表明刘家洼青铜器埋藏环境为弱碱性氧化型环境,土壤中氯离子含量不高,这与出土青铜器的腐蚀...     

The risk of harm to archaeological artefacts in soil from dynamic subsurface pressures generated by agricultural operations: experimental studies

An investigation was made of the fracture risk to buried ceramic pots and bones from the subsurface pressures generated by agricultural operations. A method for generating subsurface pressures at 0.25 m depth in a soil bin was developed and used to explore fracture failure of modern replicates of ceramic pots corresponding to different archaeological periods and aged medieval human bone. Application of conductive traces to the objects’ surfaces allowed detection of fracturing in real‐time without excavation. Predictive models relating fracture of objects to subsurface pressure application were developed by relating the probability of fracture to observed survival statistics at increasing subsurface pressures. Subsurface pressures of above 100 kPa were sufficient to fracture the more fragile pots at a probability level of 90%. The lowest subsurface pressure causing bone fracture was 280 kPa; however, no relationship was observed between subsurface pressure and bone fracture, probably due to variation in bone material. The subsurface pressures generated and applied are within the range reported from field measurements during typical agricultural operations. They indicate that measures to control the generation of subsurface pressures would be necessary to mitigate risk of harm from agriculture to buried archaeology; for example, via low‐pressure tyres, tracks and appropriate tillage.     

One-Dimensional Ground Response as a Preliminary Tool For Dynamic Analyses in Geotechnical Earthquake Engineering

This article discusses how to calibrate some parameters of two-dimensional finite element models for numerical analyses in geotechnical earthquake engineering. The calibration was made through the simulation of the one-dimensional vertical propagation of S-waves in elastic layers, whose theoretical solutions are available in literature. The numerical results were compared with those obtained by frequency domain analyses. The influence of several sources of damping arising in the model, including that deriving from boundary conditions and numerical integration, was investigated. The proposed calibration procedure constitutes a useful preliminary step for performing advanced dynamic analyses of any geotechnical system.     

Probabilistic Seismic Design of Pile Foundations in Non Liquefiable Soil by Response Spectrum Approach

The behavior of pile foundations in non liquefiable soil under seismic loading is considerably influenced by the variability in the soil and seismic design parameters. Hence, probabilistic models for the assessment of seismic pile design are necessary. Deformation of pile foundation in non liquefiable soil is dominated by inertial force from superstructure. The present study considers a pseudo-static approach based on code specified design response spectra. The response of the pile is determined by equivalent cantilever approach. The soil medium is modeled as a one-dimensional random field along the depth. The variability associated with undrained shear strength, design response spectrum ordinate, and superstructure mass is taken into consideration. Monte Carlo simulation technique is adopted to determine the probability of failure and reliability indices based on pile failure modes, namely exceedance of lateral displacement limit and moment capacity. A reliability-based design approach for the free head pile under seismic force is suggested that enables a rational choice of pile design parameters.     

Dynamic Response of Saturated Soil - Foundation System Acted upon by Vibration

In this study, the response and behavior of machine foundations resting on dry and saturated sand was investigated experimentally. In order to investigate the response of soil and footing to steady state dynamic loading, a physical model was manufactured to simulate steady state harmonic load at different operating frequencies. Total of 84 physical models were performed. The footing parameters are related to the size of the rectangular footing and depth of embedment. Two sizes of rectangular steel model footing were tested at the surface and at 50 mm depth below model surface. Meanwhile the investigated parameters of the soil condition include dry and saturated sand for two relative densities 30% and 80%. The response of the footing was elaborated by measuring the amplitude of displacement by the vibration meter. The response of the soil to dynamic loading includes measuring the stresses inside the soil using piezoelectric sensors as well as measuring the excess pore water pressure using pore water pressure transducers. It was concluded that the maximum displacement amplitude response of the foundation resting on dry sand models is more than that on the saturated sand by about 5.0–10%. The maximum displacement amplitude of footing is reduced to half when the size of footing is doubled for dry and saturated sand. The final settlement (St) of the foundation increases with increasing the amplitude of dynamic force, operating frequency and degree of saturation. Meanwhile, it is reduced with increasing the relative density of sand, modulus of elasticity, and embedding inside soils. The excess pore water pressure increases with increasing the relative density of the sand, the amplitude of dynamic loading and the operating frequency. In contrast, the rate of dissipation of the excess pore water pressure during dynamic loading is more in the case of loose sand.     

Lead concentrations in bones and soil

Lead concentrations were measured in 41 rib samples from the Romano-British cemetery at Poundbury and in two sets of soil samples from the graves yielding up the bones. The levels of lead in the soil were in no way exceptional (means for the two series were 16·7 and 24·8 μg/g dry weight) and there was no correlation between soil lead and bone lead concentrations.Since bone lead concentrations vary independently of those in the soil, it is unlikely that the bones are contaminated by lead in the soil, at least under the conditions prevailing at this particular site.     

Nanozonation in Dense Cities: Testing a Combined Methodology in Barcelona City (Spain)

Microzonation is widely used in seismic risk evaluations to define the predominant period values, which are usually associated with extended areas of a few hundred meters. However, the representative values corresponding to these areas are obtained from few measurements in each area. Thereby, results are accurate only in the case of depth-dependent soils. However, not detected narrow and sharp lateral changes in soil are potentially the cause of imprecision and could be a source of specific errors. This article aims to present several tests conducted in order to emphasise the importance of accurate selection of points, to underscore the necessity of more precise and detailed evaluations, and to suggest a possible methodology to select the most appropriate data acquisition points. Results highlight the need to divide microzonation areas into smaller zones for a precise evaluation in locations where sudden changes in soil characteristics exist. Therefore, in such sites the requirement of nanozonation appears; defining zones with the same soil response. Distance between vibration measurements could be the main problem for nanozonation; data acquisition in areas with irregular geology can be time consuming when a precise analysis is required. In the most complicated environments or in dense cities, it could even be unfeasible. Consequently, it is necessary to establish a functional methodology to adequately distribute the measurement points throughout the area. On this occasion, three sites in Barcelona city were studied. This city is surrounded by mountains at NW, W, and S, and by the Mediterranean Sea at N and E. As a consequence, the shallow geology is characterized by many paleochannels and streams that are currently buried. These geological structures most likely affect the soil response. Several tests were carried out to determine this dependence. The tests were based on Ground Penetrating Radar (GPR) surveys to define the paleochannels position and on vibration measurements in order to define properly the soil response. The results from both methods were compared to the known geology to accurately define the effect of the shallow geological structures in the predominant period and in the GPR images. Areas with the same geological unit but different materials were identified in the GPR images, allowing the selection of the most appropriate distance between vibration measurements in each place. As a final result, predominant periods that were measured over the same geological unit but over different material showed changes higher than the 40% in short distances. This procedure could improve the soil response maps, including nanozonation.     

一件中国国家博物馆馆藏铜雕塑锈蚀产物的分析研究

铜雕塑作为现代艺术品因其历史价值、文化价值、审美价值、科技价值和时代价值被越来越多的博物馆收藏。经过岁月的洗礼,雕塑上有时也会出现锈蚀产物,锈蚀产物或影响艺术品的美感或进一步损害雕塑,因此需要对锈蚀产物进行鉴别,然后采取适合的方法将其去除。为此,通过超景深三维视频显微观察、扫描电子显微镜-能谱仪、显微激光拉曼光谱和傅立叶变换显微红外光谱对一件中国国家博物馆馆藏铜雕塑锈蚀产物进行取样分析。能谱结果表明该锈蚀产物中没有氯离子,再结合拉曼光谱和显微红外光谱结果可以确定锈蚀产物是蓝铜钠石[Na₂Cu(CO₃)₂·3H₂O]和含有钠离子和氧离子的水合甲酸铜[Cu₄Na₄O(HCOO)₈(OH)₂·4H₂O],这种铜锈蚀产物在国内报道较少。为防止它们进一步腐蚀和损害雕塑,选择使用物理方法将锈蚀产物清除。科学的检测方法和分析手段为铜雕塑保护方案的制定提供了重要信息支撑和理论依据。