浅海导管架平台结构损伤诊断试验研究

基于模型试验研究了浅海导管架平台的结构损伤诊断,采用标量型ARMA模型识别出结构的三阶模态参数,分别采用遗传算法和模态应变能法对试验模型不同模拟损伤工况进行了损伤诊断。基于遗传算法,提出了采用不同自由度一阶模态参数的损伤诊断方法。研究表明,由于海洋平台的前三阶模态分别为不同自由度的一阶模态,采用两阶或三阶模态识别损伤时,损伤杆件影响较小的自由度方向的模态参数对结构的损伤诊断将产生不利的影响,成为识别噪声。因此,可分别采用不同自由度的一阶模态进行结构损伤诊断。     

渗流诱发套损机制与数值计算

油田套损是石油工程中的一大技术难题,多年来困扰着各油田。大量的现场调查和理论分析表明,油田套损与油藏渗流场动态变化密切相关。无论是剪切套损、拉伸套损还是挤压套损,都是渗流引起应力场调整,最终导致套管受力损伤。基于油藏流固耦合理论,分析了油田渗流诱发套损的机制,建立了油藏渗流-应力耦合计算的数学模型,并介绍了利用流固耦合进行套损预测计算的算例,对于套损防控具有重要的理论指导意义。     

2018年9月8日云南墨江M5.9地震震害综述

2018年9月8日10时31分29秒,云南省墨江县(23.28°N,101.53°E)发生M5.9地震。根据现场调查情况,详细阐述地震灾区房屋建筑结构特点、房屋建筑及生命线工程震害特征,给出房屋建筑震害矩阵,对其震害成因进行分析,并与省内近年相似震级的地震震害进行对比分析,结果表明:本次地震波及范围广、总体震害轻、无人员死亡、地质灾害轻。     

A study on relation between acoustic emission and characteristic displacement field on the sample with multi en echelon structures — The theoretic and experimental explorations of strain gap

Based on the phenomena that the deformation gap was observed before the great Tangshang earthquake, this paper discusses the strain gap according to test and theory. The (strain) patterns were recorded photographically by realtime holographic interferometry and shadow optical method of caustics, as soon as the loading process started. In the meantime, the AE (acoustic emission) signals were recorded by a micro crack information storage-analysis system. According to damage theory and location of micro fracture, we have studied the stain gap and gained: a) It is necessary that strain gap appears under the condition of linear elasticity theory, and its situation is relatively stable, corresponding to stress concentration. b) Micro fractures, which appear initially at area of high stress, occur rarely at the strain gap, and their locations are finally in the zone between the stress concentration area and the strain gap, which indicate the clusters or groups. However, the major macro fracture (final rupture) started from the shadow areas, and then grew quickly towards the strain gaps, which resulted in failure of sample. Foundation item: The Dual Project of China Seismological Bureau (9691309020301), the Specialized Funds for National Key Basic Study (G1998040704), the project for the MOST under contract (2001BA601B02) and Youth Funds for applied basic study of the Science and Technology Bureau of Yunnan Province (98D019Q).     

Ecologically based landscape pattern optimization in northwest of Beijing

Supported by the technologies of remote sensing (RS) and geographical information system (GIS), we chose northwest of Beijing as a study area and gave priority to understanding of the spatial-temporal characteristics of landscape pattern change through visually interpreted Landsat TM images of 1989, 1996 and 2005. It is believed that there were a series of landscape ecological problems caused by city expansion: landscape ecological connectivity was low; landscape structure was simplified; the fragmentation of green land patch was more obvious on the plain areas, moreover, spatial distribution of green land was unbalanced. For this reason, this study adopted accumulative cost distance model, combined with ecosystem services and spatial interactions of landscape types, analyzed the spatial difference of the ecological function and the compactness of landscape structure in the study area, and further discussed the landscape pattern optimization proposal. We find that it is essential to protect and establish ecological sources, to establish urban ecological corridors, and to establish ecological nodes at the landscape ecological strategic positions so as to intensify spatial relationships among landscape elements and maintain continuity of landscape ecological process and pattern in the course of city expansion. The methods and final results from this study are expected to be useful for landscape ecological planning in Beijing region.     

1998年张北6.2级地震宏观烈度

充分利用震害评估和宏观考察的资料 ,采用震害程度和震害指数 2个标准共同确定了1 998年张北 6.2级地震的宏观烈度。极震区烈度为 度 ,呈 NWW和 NNE双向分布 ,以NWW为主 ,面积 1 35km2 。 度区呈 NE、NW双向伸展图象 ,但是 SE方向伸展不足 ,面积约340 km2。地震重伤人员普遍集中在 度区和 度区。 度区亦呈 NE、NW双向伸展图象 ,但是 NW、SW方向延伸长 , 度区面积约 1 0 0 0 km2 。宏观震中 :北纬 41°0 9′,东经 1 1 4°2 7′。在极震区的 NNE、SSW和 NWW方向 ,存在 3个烈度异常区 ,它们分别在极震区 3个分支的延伸方向上。文中讨论了烈度不高而震后较重的原因。震区没有发现地表破裂带 ,也没有发现第四纪强烈活动的大型断裂。极震区为主的 NWW方向和震前存在的小地震条带吻合 ,暗示可能存在成因上的联系     

Damage investigation of girder bridges under the Wenchuan earthquake and corresponding seismic design recommendations

An investigation of girder bridges on National Highway 213 and the Doujiangyan-Wenchuan expressway after the Wenchuan earthquake showed that typical types of damage included： span collapses due to unseating at expansion joints; shear key failure; and damage of the expansion joint due to the slide-induced large relative displacement between the bottom of the girder and the top of the laminated-rubber bearing. This slide, however, can actually act as a form of isolation for the substructure, and as a result, the piers and foundation of most of the bridges on state route 213 suffered minor damage. The exception was the Baihua Bridge, which suffered severe damage. Corresponding seismic design recommendations are presented based on this investigation.     

Fracture characteristics in Cretaceous platform and overlying ramp carbonates: An outcrop study from Maiella Mountain (central Italy)

This article focuses on field- and laboratory-based characterization of vertically persistent fractures that are part of oblique-slip normal fault zones and crosscut the Cretaceous platform and overlaying ramp carbonates outcropping at Maiella Mountain (central Italy). The achieved results show that: (i) fault damage zones are wider and more densely fractured in the platform carbonates than in the ramp ones; (ii) joints and sheared joints composing the fault damage zones are taller, better connected and less spaced within the former rocks than in the ramp carbonates. The aforementioned structural differences are interpreted to be a consequence of the different mechanical properties of the platform and ramp carbonates during failure. At Maiella Mountain, platform carbonates are, indeed, made up of overall stiffer (higher Uniaxial Compressive Strength values) and less porous rocks, due to more abundant intergranular void-filling cement and presence of matrix.In terms of hydrocarbon flow and recovery, geometric and dimensional attributes of fractures suggest that the well-connected network of closely spaced fractures cutting across the platform carbonates may form efficient pathways for both vertical and horizontal hydrocarbon flow. In contrast, the relatively poorly connected and low-density fracture network affecting the ramp carbonates is likely less efficient in providing fairways for flowing hydrocarbons.     

How much does an extreme rainfall event cost? Material damage and relationships between insurance,rainfall, land cover and urban flooding

This research aims to understand how insurance, rainfall, land cover and urban flooding are related and how these variables influenced the material damage in the Lisbon Metropolitan Area (LMA) during the 2000–2011 period. Correlation coefficients show strong relationships between built-up areas and claims (0.94) and payouts (0.88). Despite no significant relationships being found between rainfall and the amount of material damage per event, three likelihood levels of flooding were determined for hourly rainfall. Unlike the studied period, the number of claims and their spatial distribution during the 2008 extreme rainfall event were strongly dependent on rainfall. Flooding related to the old watercourses assumed greater importance during this extreme event, recovering a more natural/ancient hydrological behaviour. In the LMA, the greatest material damage was the result of high-magnitude/low-probability rainfall events. Lower magnitude events can trigger numerous claims in heavily built-up areas, but they are hardly capable of producing large material damage.     

基于动态CT识别的冻土单轴压缩损伤本构模型

采用连续介质力学与热力学方法,建立了冻土单轴压缩损伤本构模型。以兰州冻结黄土为例,基于冻土单轴压缩动态CT试验,对冻土附加损伤的2个阶段,即塑性损伤和微裂纹扩展损伤分别采用硬化曲线法和动态CT识别方法进行了损伤计算,在此基础上给出了冻土附加损伤与弹性应变的对应关系,建立了基于试验的冻土损伤演化方程,并进行了有效应力的计算。