陕北明长城夯土密度与雨蚀破坏的量化研究

为量化研究夯土性质对陕北明长城遗址雨蚀破坏模式的影响作用,采用室内模拟降雨试验的方法对夯土密度和雨蚀量间的关系进行定量化分析。研究结果显示,大到暴雨条件下,干湿作用产生的破坏是低强度夯土(密度1.5 g·cm^-3、1.6 g·cm^-3)最主要的雨蚀破坏模式,冲刷破坏造成的雨蚀量较小;水力侵蚀产生的冲刷破坏和重力侵蚀引起的小范围掉块是高强度夯土(密度1.7~1.9 g·cm^-3)最主要的破坏模式,冲刷破坏造成的雨蚀量较大;当土体含水率在3%~7%区间时,夯土的雨蚀量和密度呈指数函数关系,二者呈现正相关性。研究结果为探索多因素作用下夯土雨蚀的破坏机制提供方法借鉴,是土遗址病害研究的重要组成部分。     

Irrigated taro (Colocasia esculenta) farming in North Kohala,Hawai‘i: sedimentology and soil nutrient analyses

How did traditional farming transform the natural environment in the Hawaiian Islands? This question is one that has largely been addressed for rainfed farming of crops like sweet potato (Ipomoea batatas), but evidence is lacking for irrigated farming of the critical staple crop taro (Colocasia esculenta). We describe the results of soil nutrient and sedimentological analyses of deeply-stratified pondfield deposits representing a 600-year-long record of irrigated taro farming in the North Kohala District, Hawai‘i Island. Soil is categorized by particle size to determine modes of transport and deposition, and concurrent soil nutrient analyses were conducted to infer shifts in the source of sediments and changes associated with taro harvesting. The advent of farming is clearly detectable in sedimentology, the presence of charcoal found within sediments, and soil chemistry. However, diminished nutrient concentrations can be attributed largely to deposition of a mixture of upstream sediments. Overall, there is no clear evidence for nutrient draw-down by taro harvesting, but we cannot yet rule it out as a factor. This study demonstrates the inherent difficulty of correlating changes in soil nutrients evident in irrigated pondfields with the long term history of soil nutrient cycling.     

From pedologic indications to archaeological reconstruction: deciphering land use in the Islamic period in the Baida district (north-western Sicily)

The aim of this work was to detect imprints on soil properties from former Islamic land use (9th to 11th century) using a multi-method, soil-chemical approach. Four soil profiles (with buried horizons) found in the vicinities of former Islamic settlements in Sicily were analysed for phosphorus (total, organic and inorganic), nitrogen (total, NO₃⁻ and NH₄⁺), carbon compounds (δ¹³C, lipids, polycyclic aromatic hydrocarbons (PAH) and functional groups), physical and chemical C-fractions and the state of soil weathering. Two soil profiles contained ceramic sherds from the Islamic period. Inorganic nitrogen forms, phosphorous and the PAH content indicated strong impacts from traditional agriculture and/or burning. Radiocarbon dating of soil organic carbon (SOC) fractions from buried horizons showed that distinct changes must have occurred during the Islamic epoch. The isotopic composition of SOC indicated that land use was probably different in earlier times. C₄ plant cultivation was expected but surprisingly lipid analyses did not confirm this. A high amount of aliphates and low C/N ratio indicated a good, long-term SOC stabilisation under the native conditions combined with Islamic land use. The irrigation of the soils probably increased the production of weakly-crystalline Fe forms that helped to stabilise SOC.     

Holocene land-use evolution and associated soil erosion in the French Prealps inferred from Lake Paladru sediments and archaeological evidences

A source-to-sink multi-proxy approach has been performed within Lake Paladru (492 m a.s.l., French Prealps) catchment and a 6-m long sediment sequence retrieved from the central lacustrine basin. The combination of minerogenic signal, specific organic markers of autochthonous and allochthonous supply and archaeological data allows the reconstruction of a continuous record of past human disturbances. Over the last 10,000 years, the lacustrine sedimentation was dominated by autochthonous carbonates and the watershed was mostly forest-covered. However, seven phases of higher accumulation rate, soil erosion, algal productivity and landscape disturbances have been identified and dated from 8400 to 7900, 6000 to 4800, 4500 to 3200, 2700 to 2050 cal BP as well as AD 350–850, AD 1250–1850 and after AD 1970. Before 5200 cal BP, soil erosion is interpreted as resulting from climatic deterioration phases towards cooler and wetter conditions. During the Mid-Late Holocene period, erosion fluxes and landscape disturbances are always associated with prehistorical and historical human activities and amplified by climatic oscillations. Such changes in human land-used led to increasing minerogenic supply and nutrients loading that affected lacustrine trophic levels, especially during the last 1600 years. In addition, organic and molecular markers document previously unknown human settlements around Lake Paladru during the Bronze and the Iron Ages.     

广东“南澳Ⅰ号”明代沉船出水铜器腐蚀产物分析

由于海水环境中含有大量氯化物,海洋出水铜器在出水前已发生腐蚀,生成铜的氧化物及氯化物等。本文以广东"南澳Ⅰ号"明代沉船出水的22件铜器残片为研究对象,运用X-射线荧光仪(XRF)、X-射线衍射仪(XRD)和扫描电镜与能谱仪(SEM-EDS)等分析其腐蚀产物和矿物组成,结果表明腐蚀产物主要为铜的碱式氯化物,如Cu2(OH)3Cl和Cu(OH)Cl等,与国外已有研究成果类似,但Cu(OH)Cl在国外海洋出水铜器腐蚀产物中并不常见。     

QUICK ESTIMATES OF SOFT SEDIMENT THICKNESSES FROM AMBIENT NOISE HORIZONTAL TO VERTICAL SPECTRAL RATIOS: A CASE STUDY IN SOUTHERN ITALY

An approach devoted to quickly assess the thickness of soft sedimentary cover in areas of unknown subsurface morphology is applied in this study. In particular, soil thickness (h) is derived by combining estimates of the resonance frequency (f _r ) relative to soft sediments with the local shear-wave velocity (V_s) profile. For this purpose, (f _r ) values are assessed from horizontal to vertical (H/V) spectral ratios of seismic noise recordings and the (V _s ) profile is obtained by considering information from shallow seismic surveys. Results obtained for a Quaternary sedimentary basin in Southern Italy are discussed. Since in the investigated area only weak independent constraints are available, special emphasis is given to the assessment of uncertainties involved in this estimate of soil thickness.     

Spectral Attenuation Relations at Soft Sites Based on Existing Attenuation Relations for Rock Sites

A simple and general method based on well-known random vibration theory is used to compute spectral attenuation relations at soft sites based on existing spectral attenuation relations at rock sites. The method consists of: (1) computation, for given magnitude and distance, of the expected Fourier amplitude spectrum associated with the median rock response spectrum computed with the attenuation relation; (2) inclusion of site effects characterized by a frequency-dependent, linear, or nonlinear transfer function; and (3) computation of the response spectrum at the soft site.     

Evaluation of the Nonlinear Seismic Response of an Earth Dam: Nonparametric System Identification

A system identification framework is proposed to investigate the nonlinear dynamic response of massive earth dams using the seismic motion recorded by a sparse array of accelerometers. The framework includes a methodical step of nonparametric analyses to characterize the involved loading conditions and response mechanisms. This nonparametric step provides essential information to reduce the indeterminacy of the associated parametric identificatin problem and ensure a proper model selection, calibration, and validation. The proposed framework was applied to the Long Valley earth dam (California) and benchmarked using records of a series of 1980 earthquakes. This article presents the conducted correlation, spectral motion reconstruction, and nonparametric stress-strain analyses. These analyses revealed a complex three-dimensional dynamic response marked by non uniform boundary conditions and a shear stress-strain behavior slightly less nonlinear than what was observed in triaxial tests of soil samples taken from the dam core.     

Effect of Shaft Diameter of Pile on Lateral Winkler Springs' Stiffness

Soil was modelled with linearly elastic three-dimensional finite elements. Lateral spring stiffness was calculated from FE results. Spring stiffness is shown varying linearly with shaft diameter. It is also found that spring stiffness is inversely proportional to powers (less than unity) of pile flexural rigidity. Scaling factors for shaft diameter and pile flexural rigidity are introduced. Basic stiffness of lateral spring is studied considering both full vertical slippage and zero slippage between the soil and the pile. Relevant relationships for stiffness are proposed. Some applications are suggested.     

Reburial and Analyses of Archaeological Remains in the Marine Environment — Investigations into the Effects on Metals

Abstract

The treatment and long-term storage of recovered cultural material from underwater heritage sites is becoming less cost effective, and reburial of archaeological sites and the associated artefacts in the marine environment is becoming increasingly common practice in managing the submerged cultural resource. Following recent large-scale underwater archaeological excavations in Marstrand harbour, Sweden, the majority of recovered finds were reburied in defined trenches in the harbour sediment. Subsequently, the Studio of the Western Sweden Conservators in conjunction with the Bohus County Museum initiated a fifty-year research project to evaluate reburial as an appropriate method of preserving waterlogged archaeological artefacts in the long term. The research project, entitled ‘Reburial and Analyses of Archaeological Remains’, was launched in 2002 and consists of six sub-projects. The main aims of these sub-projects are to analyse the extent of deterioration of the most common material types found on underwater archaeological sites, assess the stability of packing and marking materials used in archaeological documentation, and monitor the reburial environment.

The aim of the metals sub-project is to investigate the short- to long-term corrosion behaviour of metals buried in the marine environment by examining the deterioration of reburied and exposed modern metal coupons and eventually compare these results to the analysis of actual shipwreck artefacts. The environmental monitoring sub-project is designed to complement the other sub-projects by assessing the physico-chemical changes occurring in the reburial environment over time and the effect on the deterioration of the different reburied material types. In comparing the results obtained over the past seven years from both the metals and monitoring sub-projects, it should be possible to more accurately evaluate the effectiveness of reburial as a long-term in situ preservation strategy for metallic archaeological remains.