广富林遗址(2008年)浸水植物遗存分析

广富林遗址2008年度浸水保存的这批样品,从中发现了种类较丰富的植物遗骸,包括有葫芦、桃核、芡实、甜瓜、水稻、葎草、楝树果实等,通过量化统计和植物利用方式分析,我们认为遗址至少在广富林文化时期形成了包括粮食种植和瓜果蔬菜栽培的园圃农业经济体系,并在周代进一步地发展。     

Microtremor HVSR Study of Site Effects in the Ilirska Bistrica Town Area (S. Slovenia)

The region of Ilirska Bistrica is one of the most seismically active areas of Slovenia, where 15 damaging earthquakes with maximum intensity equal or greater than V EMS-98 have occurred in the last 100 years. These earthquakes have shown that strong site effects are characteristic of the parts of the town that are built on soft Pliocene clay and sand overlain by Quaternary alluvium. Since there is a lack of boreholes and geophysical and earthquake data, the microtremor horizontal-to-vertical spectral ratio (HVSR) method was applied to a 250 m dense grid of free-field measurements over an extended area and to a 200 m dense grid in the town area in order to assess the fundamental frequency of the sediments. Measurements were additionally performed in ten characteristic houses to assess the main building frequencies. The effects of wind and artificial noise on the reliability of the results were analyzed. The map of the fundamental frequencies of sediments shows a distribution in a range of 1–20 Hz. The lower frequency range (below 10 Hz) corresponds to the extent of Pliocene clays and sand overlain by alluvium, which form a small basin, and the higher frequencies to flysch rocks, but variations within short distances are considerable. The measurements inside the buildings of various heights (2–6 stories) showed main longitudinal and transverse frequencies in the range 3.8–8.8 Hz. Since this range overlaps with the fundamental frequency range for Pliocene and Quaternary sediments (2–10 Hz), the danger of soil-structure resonance is considerable, especially in the northern part of the town. Soil-structure resonance is less probable in the central and southern part of the town, where higher free-field frequencies prevail. These observations are in agreement with the distribution of damage caused by the 1995 earthquake (M_L?=?4.7, I_max?=?VI EMS-98), for which a detailed damage survey data is available.     

Site Effects at Long Periods from Digital Strong Motion Records of the KiK-net,Japan

The high-quality digital records of the Japanese KiK-net were examined, with the aim of studying the influence of local site conditions on the displacement spectral ordinates at long periods. The attention was limited to those records for which the velocity profiles up to 100–200 m depth were known, and corresponding surface and borehole accelerograms were available. Based on the available records and with the support of 1D numerical simulations, different aspects that may have an influence on the amplification of long period spectral ordinates were studied, including the bedrock velocity profile, the site classification using V_s,30, and the earthquake magnitude.

Small amplification factors at long periods were found, ranging from 1 to 1.3, with median value from 1.05 to 1.1, for Eurocode 8 site classes B and C, respectively. Only for two records on soft soils (at the boundary between Eurocode 8 classes C and D), from small magnitude earthquakes, large amplification factors were obtained, up to about 4. A good correlation was found of the amplification levels with the response spectral ratio D(T₀)/D(10), where D(T₀) and D(10) are displacement spectral ordinates of the input signal at bedrock, at the fundamental period T₀ of the soil profile and at T = 10 s, respectively.     

Site Classification Using Horizontal-to-vertical Response Spectral Ratios and its Impact when Deriving Empirical Ground-motion Prediction Equations

We classify sites based on their predominant period computed using average horizontal-to-vertical (H/V) response spectral ratios and examine the impact of this classification scheme on empirical ground-motion models. One advantage of this classification is that deep geological profiles and high shear-wave velocities are mapped to the resonance frequency of the site. We apply this classification scheme to the database of Fukushima et al. [2003] Fukushima, Y., Berge-Thierry, C., Volant, P., Griot-Pommera, D. A. and Cotton, F. 2003. Attenuation relation for west Eurasia determined with recent near-fault records from California, Japan and Turkey. Journal of Earthquake Engineering, 7(3): 1–26.  [Google Scholar], for which stations were originally classified as simply rock or soil. The calculation of average H/V response spectral ratios permits the majority of sites in the database to be unambiguously classified. Soft soil conditions are clearly apparent using this technique. Ground-motion prediction equations are then computed using this alternative classification scheme. The aleatoric variability of these equations (measured by their standard deviations) is slightly lower than those derived using only soil and rock classes. However, perhaps more importantly, predicted response spectra are radically different to those predicted using the soil/rock classification. In addition, since the H/V response spectral ratios were used to classify stations the predicted spectra for different sites show clear separation. Thus, site classification using the predominant period appears to be partially mapped into the site coefficients of the ground-motion model.     

The Response of Isolated Bridges Accounting for Spatial Variability of Ground Motion

The effects of the spatial variability of ground motion (loss of coherence, wave passage, and local site conditions) on the response of isolated bridges are investigated.

Therefore, a statistical approach is adopted to represent uncertainties in both the bridge configuration and the ground motion variability. The response of isolated bridges, designed for a standard input motion, under a spatially varying ground motion, is evaluated by nonlinear time-history analyses; the system performance is measured by the displacement demand on isolators.

Results show that the phenomenon affects the structural response considerably; the demand increases for the majority of isolators, irrespective of bridge configuration.     

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.     

Numerical Evaluation of Seismic Soil Pressures on Rigid Walls Fixed to the Bedrock

Seismic soil pressures developed on a 7 m rigid retaining wall fixed to the bedrock are investigated using a finite element model that engages nonlinear soil intended materials available in OpenSees. This allows incorporation of the inelastic behavior of the soil and wave propagation effects in the soil-wall system seismic response. The nonlinear response of the soil was validated using the well-stablished, frequency-domain, linear-equivalent approach. An incremental dynamic analysis was implemented to comprehensively examine the effect of soil nonlinearity and input motion on the induced seismic pressures and to evaluate current code equations/methodologies at different levels of earthquake intensity. The results show that soil nonlinearity and seismic wave amplification may play an important role in the response of the soil-wall system. Therefore, methodologies that rely only on peak ground acceleration may introduce large bias on the estimated seismic pressures in scenarios where high nonlinearity and site amplification are expected.     

对文物保护单位保护规划的几点认识

保护规划是文物保护单位管理的基本手段之一。经过多年实践,文物保护单位保护规划逐渐形成了自己的特色。作为一种以文物保护为主要目的,以空间控制为主要手段,以文物综合利用展示为主要途径,致力于实现文物保护与区域经济社会发展相协调的专项规划,文物保护单位保护规划正在被行业所接受。然而,现阶段的文物保护单位保护规划仍然存在着对文物特性考虑不足,对现实发展回应不足,对实际工作指导不足等问题,亟需通过提升法律地位,完善规划体系,重视规划执行等措施来进一步完善,以更好地发挥应有的作用。     

西安鱼化寨遗址仰韶文化土坑墓发掘简报

一、遗址概况鱼化寨遗址位于西安市雁塔区鱼化寨街道鱼化寨村西北侧,皂河西岸的二级台地上,今西安外事学院北校区西北部。遗址东、北两侧被皂河环绕,地势中心高,周围低(图一)。2002年～     

2000～2001年随州厉山佘家老湾遗址试掘报告

佘家老湾遗址位于湖北省随州市北约24公里处,隶属随州市随县厉山镇王岗乡同心村八组佘家老湾。2000年上半年,在配合汉丹-宁西铁路联接线建设工程的考古调查中发现该遗址,遗址面积约10万平方米。2000年11～12月及2001年5～6月,湖北省文物考古研究所对遗址进行了试掘,发掘面积324平方米。该遗址文化层堆积较单一,主要是新石器时代晚期遗存。从出土的遗物特征看,属江汉地区石家河文化系统,但又具有河南龙山文化王湾三期的特点。该遗址对于研究这两大文化的相互碰撞及交流提供了极好的范例,同时也使我们对于这一特殊地理区域内的石家河文化晚期的面貌有了较深入的了解。