陷落柱地震响应特征分析

通过分析研究陷落柱地震响应特征,提出判别陷落柱的依据,并与实例进行验证比较,对于今后正确分辨和圈定陷落柱具有一定指导意义。      

Dynamic collapse analysis for a reinforced concrete frame sustaining shear and axial failures

Shaking table test results from a one‐story, two‐bay reinforced concrete frame sustaining shear and axial failures are compared with nonlinear dynamic analyses using models developed for the collapse assessment of older reinforced concrete buildings. The models provided reasonable estimates of the overall frame response and lateral strength degradation; however, the measured drifts were underestimated by the models. Selected model parameters were varied to investigate the sensitivity of the calculated response to changes in the drift at shear failure, rate of shear strength degradation, and drift at axial failure. For the selected ground motion, the drift at shear failure and rate of shear strength degradation did not have a significant impact on the calculated peak drift. By incorporating shear and axial‐load failure models, the analytical model is shown to be capable of predicting the axial‐load failure for a hypothetical frame with three nonductile columns. Improvements are needed in drift demand estimates from nonlinear dynamic analysis if such analyses are to be used in displacement‐based performance assessments. Copyright © 2008 John Wiley & Sons, Ltd.     

巢湖塌岸的特征及其规律

巢湖是我国五大淡水湖之一,资源丰富,然而其岸带地质环境问题严重地影响了巢湖资源优势的发挥,本文通过调查研究,分析塌岸产生的基本规律和机制,并提出相应的防灾减灾对策。     

安徽省枞阳县高峰村同咀崩塌稳定性分析与评价

通过实地踏勘并辅以钻探等技术手段,对枞阳县高峰村同咀崩塌的边坡地形地貌、地层岩性、地质构造、水文地质条件、工程地质条件以及人类工程活动等条件进行调查,并在进行变形位移监测的基础上,对研究区崩塌灾害的发育特征、影响因素以及形成机制进行了分析,并采用极限平衡法对崩塌灾害的稳定性进行了评价。研究结果表明:2处崩塌灾害规模等级均属小型,破坏方式均为滑移式;影响因素主要包括人工切坡,钾长花岗岩强烈风化,构造裂隙、风化裂隙和卸荷裂隙发育和强降雨等; 2处崩塌在天然工况下处于基本稳定状态,在暴雨工况下处于欠稳定状态,需采取相关治理措施。依据分析评价结果对崩塌灾害治理提出了防治方案建议。     

南海北部陆缘张裂—岩石圈折沉的地壳响应

南海北部陆缘在中生代晚期曾形成宏伟的华夏陆缘造山带。火成岩岩石学、岩相古地理学和地球物理学证据显示，该造山带不仅具有巨厚（50－60km)的陆壳，而且还有巨厚（160－180km)的岩石圈根，在地势上曾出现过高3500－4000m的华夏山系。陆缘裂陷盆地的形成发育历史、地壳－岩石圈深部结构、火成岩地球化学特征及理论计算均表明，南海北部陆缘从晚白垩世以来发生的张裂作用起始于华夏陆缘造山带的拉伸塌陷，岩石圈折沉是南海北部陆缘张裂的重要的引发机制。因此，南海北部陆缘张裂既不同于弧后扩张，也不受控于大西洋式的海底扩张，而是该区大陆构造演化和深部壳幔相互作用的结果。     

莱芜市矿山排水对地质环境的影响分析

莱芜市煤炭和铁矿资源丰富,开采历史悠久,矿山排水量较大。煤矿矿坑水中SO4^2-、总硬度、矿化度、F^-等组分较高,对地下水水化学场构成影响,矿区附近SO4^2-含量大于300mg／L的孔隙水分布面积9.98km^2。铁矿排水具有高强度、大降深、强烈疏干的特征,导致矿山背斜东翼已形成水位降落漏斗,其中水位标高120m的漏斗面积达27．5km^2,由于矿坑排水加之水源开采,1973年以来赵庄、孟家庄、西泉河地段共发生岩溶塌陷220处,塌陷总面积8880m^2。     

泰安市泰山区岩溶塌陷成因分析及防治措施

泰安市泰山区为岩溶塌陷易发区。通过对该区岩溶塌陷现状和成因的分析研究,认为岩溶洞隙的开口程度是影响岩溶塌陷形成的重要因素;松散盖层是岩溶塌陷形成的物质基础,而厚度、岩性结构则对其稳定性起着明显的控制作用;地下水动力条件的改变是岩溶塌陷形成的诱发因素。加强地下水合理规划开采,建立完善的监测网络可以有效减少塌陷所造成的危害。     

地质灾害危险性评估在规划建设中的应用实例

各类地质灾害对城市规划建设具有重要影响。本文以济南市高新区孙村片区规划建设项目为例,分析了当地地质环境条件特征,对其危险性进行了评估,对区内进行工程建设的适宜性进行了评估,并提出了防治措施及建议。     

Collapse of a nonductile concrete frame: Shaking table tests

Post‐earthquake reconnaissance has reported the vulnerability of older reinforced concrete (RC) columns lacking details for ductile response. Research was undertaken to investigate the full‐range structural hysteretic behavior of older RC columns. A two‐dimensional specimen frame, composed of nonductile and ductile columns to allow for load redistribution, was subjected to a unidirectional base motion on a shaking table until global collapse was observed. The test demonstrates two types of column failure, including flexure‐shear and pure flexural failure. Test data are compared with various simplified assessment models commonly used by practicing engineers and researchers to identify older buildings that are at high risk of structural collapse during severe earthquake events. Comparison suggests that ASCE/SEI 41‐06 produces very conservative estimates on load–deformation relations of flexure‐shear columns, while the recently proposed ASCE/SEI 41‐06 update imposes significant modifications on the predictive curve, so that improved accuracy has been achieved. Copyright © 2008 John Wiley & Sons, Ltd.     

Procedure to predict the storey where plastic drift dominates in two‐storey building under strong ground motion

A procedure is presented to predict the storey where plastic drift dominates in two‐storey buildings under strong ground motion. The procedure utilizes the yield strength and the mass of each storey as well as the peak ground acceleration. The procedure is based on two different assumptions: (1) the seismic force distribution is of inverted triangular form and (2) the rigid‐plastic model represents the system. The first and the second assumptions, respectively, lead to lower and upper estimates of the base shear coefficient under which the drift of the first storey exceeds that of the second storey. The efficiency of the procedure is verified by dynamic response analyses using elasto‐plastic model. Copyright © 2008 John Wiley & Sons, Ltd.