Vertical impedance of tapered piles considering the vertical reaction of surrounding soil and construction disturbance     

Liu Gao  Si Xiao  Juntao Wu  Ning Wang 《Marine Georesources & Geotechnology》2017,35(8):1068-1076

The pile–soil system is divided into layers of sufficient number such that the shear stiffness at the pile–soil interface can be determined based on the complex stiffness transfer method. The vertical reaction of surrounding soil on the annular projections at the interface of adjacent pile segments is simplified using Voigt model, whose spring and damping coefficients are derived afterward, allowing an amended impedance function transfer method to be proposed. Using the amended impedance function transfer method, the dynamic equilibrium equation of the pile is solved to give an analytical solution for the impedance function at the pile top. By comparing the solution proposed in this paper with other solutions, the superiority of the bearing capacity of a tapered pile is further confirmed. A parameter study is then conducted to give insight into the coupled interaction of the vertical reaction of the surrounding soil with construction disturbance in the low-frequency range concerned in the seismic design of the pile foundations.  相似文献   

The spatial heterogeneity of riverbed saturated permeability coefficient in the lower reaches of the Heihe River Basin,Northwest China   总被引：1，自引：0，他引：1       下载免费PDF全文

Haiyang Xi  Lu Zhang  Qi Feng  Jianhua Si  Zongqiang Chang  Tengfei Yu  Jianguo Li 《水文研究》2015,29(23):4891-4907

In arid region, direct infiltration from rainfall contributes little to groundwater compared with localized recharge from streams. How to quantify riverbed infiltration to groundwater systems is an important area of research in hydrology. In this study, saturated permeability coefficient of a riverbed in an arid inland river basin located in the northwest of China was obtained by Guelph Permeameter and laboratory analysis methods. The characteristics of riverbed infiltration and its spatial patterns were analysed using geostatistical method and kriging method. The results showed that the saturated permeability coefficient varied from 0.089 to 2.802 m/d, indicating moderate degree of variability. The Guelph Permeameter and laboratory test methods provided consistent estimates of saturated permeability coefficient. There was a strong spatial correlation for K_fs of the riverbed in this study area when Range (A) was less than 0.276°, suggesting that the maximum sampling distance for saturated permeability coefficient of the riverbed was 0.276° under isotropic conditions. The K_fs near the centre of the riverbed was higher than the value near riverbank. The K_fs values decreased in the direction of upstream to downstream in the Heihe River Basin. The riverbed mechanical composition, initial soil water content and bulk density have significant influence up on the riverbed infiltration. Besides, the topographical factors including the width, altitude and distance factors of the riverbed together impacted the riverbed infiltration and the slope of the riverbed and also influenced the riverbed infiltration. Copyright © 2015 John Wiley & Sons, Ltd.  相似文献   

基于改进的风险矩阵法的生命线网络地震脆弱性分析          下载免费PDF全文

申思  张明媛  袁永博 《地震工程学报》2015,37(4):963-968

生命线网络的脆弱性不单单只表示地震发生后对网络作用而产生的后果,还应该包括网络的连通情况。本文在重新确定生命线网络脆弱性定义的基础上,运用风险评估理论中的风险矩阵方法综合考虑生命线网络的连通性能和失效后果两个方面来评价生命线网络的脆弱性,并以一个供气管网为例说明改进的风险矩阵法评价生命线网络脆弱性的有效性和合理性,找出供气管网中脆弱性等级最高的节点,分析其脆弱性等级最高的原因,以便于重点保护,并降低网络的脆弱性。  相似文献   

海拉尔地震台重力潮汐扰动分析     

熊峰  张起  查斯  杨彦明  赵星 《山西地震》2015,(2):21-23

基于前兆数据跟踪及分析应用,对海拉尔台重力潮汐滤波观测值在远震前后有向下扰动的现象进行分析,对海拉尔地震台和乌加河地震台的重力潮汐滤波观测值在全球Ms7.0以上地震、中国大陆Ms6.0以上地震的震后效应及同震响应进行统计。得出,海拉尔台重力潮汐滤波值中叠加向下扰动属非地球物理事件。  相似文献   

新建社区的地震应急避难规划研究   总被引：2，自引：2，他引：0  

赖俊彦  李亦纲  杜晓霞  刘传伟  许建华 《震灾防御技术》2015,10(3):629-638

人员密集、用地集约、功能混合是近年来新建社区的共同特点,一旦地震大灾在没有任何应急准备的情况下发生,社区居民的震时疏散和震后安置将面临很大困难。本文分析了新建社区的开发模式特点、脆弱性和应急避难需求,提出了新建社区地震应急避难规划设计的五点原则:安全第一、因地制宜、优化分区、有机整合和家喻户晓。通过大连市万科海港城一期地震安全示范社区"应急避难规划设计方案"实例,说明依据上述原则开展空间布局等"硬"规划和实施机制等"软"规划的具体方法,验证了规划原则的可操作性和对于管理、规划、建设防灾减灾城市的积极作用。  相似文献   

Vis‐Near IR Reflectance Spectroscopy for Soil Organic Carbon Content Measurement in the Canadian Prairies          下载免费PDF全文

Wei Hu  Henry Wai Chau  Bing Cheng Si 《洁净——土壤、空气、水》2015,43(8):1215-1223

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浅海悬沙浓度观测方法的对比研究   总被引：4，自引：0，他引：4  

魏晓  汪亚平  杨旸  陈坚  高建华  王爱军  李东义  胡国栋 《海洋地质与第四纪地质》2013,(1):161-170

在动力和沉积条件复杂的浅海海域获取水-体的悬沙浓度有多种方法,目前较先进的主要是声学和光学浊度测量方法,但均需通过现场采集水样进行浊度标定;水样的分析方法主要有抽滤法和沉淀干燥法。根据2010年3—4月在厦门九龙江口获取的光学(OBS、LISST-100X)和声学(ADCP、ADP和ADV)浊度数据,以及现场同步水样,对这两种获取悬沙浓度的方法进行了比较;2011年2—3月在长江口北支获取水样,分别使用抽滤法和沉淀干燥法获取悬沙浓度数据进行比对分析。结果表明,声学和光学方法都具有较高的精度,在同一观测层位,光学与声学仪器的相对误差均较小;由于声波在水体中传播距离较远,声学方法可获得沿水深的整个剖面的信息,因而比光学仪器具有更高的空间分辨率和测量范围。对比发现,抽滤法获得的悬沙浓度数值略低于沉淀干燥法获得的结果,可能与沉淀干燥法难以洗净盐分有关。  相似文献   

Analysis Procedure of the Cyclic Bearing Capacity for Suction Anchors in Soft Clays     

Jianhua Wang  Shuzhao Li 《Marine Georesources & Geotechnology》2013,31(6):546-555

This article presents a procedure to calculate the bearing capacity of suction anchors subjected to inclined average and cyclic loads at the optimal load attachment point using the undrained cyclic shear strength of soft clays based on the failure model of anchors proposed by Andersen et al. The constant average shear stress of each failure zone around an anchor is assumed and determined based on the static equilibrium condition for the procedure. The cyclic shear strength of each failure zone is determined based on the average shear stress. The cyclic bearing capacity is finally determined by limiting equilibrium analyses. Thirty-six model tests of suction anchors subjected to inclined average and cyclic loads were conducted, which include vertical and lateral failure modes. Model test results were predicted using the procedure to verify its feasibility. The average relative error between predicted and test results is 1.7%, which shows that the procedure can be used to calculate the cyclic bearing capacity of anchors with optimal loading. Test results also showed that the anchor was still in vertical failure mode under combined average and cyclic loads if an anchor was in vertical failure mode under static loads. The anchor failure would depend on the vertical resistance degradation under cyclic loads if an anchor was in lateral failure mode under static loads. Cyclic bearing capacities associated with the number of load cycles to failure of 1000 were about 75% and 80% of the static bearing capacity for vertical failure anchors and lateral failure anchors, respectively.  相似文献   

Dynamic response of a large-diameter pile with variable section in layered saturated soil considering construction disturbance effect     

Si Xiao  Kuihua Wang  Juntao Wu  Liu Gao 《Marine Georesources & Geotechnology》2013,31(3):339-348

ABSTRACT

An analytical solution is developed in this paper to investigate the vertical time-harmonic response of a large-diameter variable-section pile, and it considers the radial inhomogeneity of the surrounding soil caused by construction disturbance. First, the saturated soil surrounding the pile is described by Biot’s poroelastic theory and a series of infinitesimally thin independent layers along the shaft of the pile, and the pile is represented by a variable-section Rayleigh–Love rod. Then, the dynamic equilibrium equations of the soil and pile are solved to obtain an analytical solution for the impedance function at the pile top using the complex stiffness transfer method and impedance function transfer method. Finally, the proposed solution is compared with previous solutions to verify its reliability, and a parameter study is conducted to provide insights into the sensitivity of the vertical dynamic impedance of the pile and velocity response in low-strain integrity testing on defective piles.  相似文献   

赤峰市地下水位评估及影响分析   总被引：2，自引：2，他引：0  

胡桂杰  包云辉  赵新城  王志春  吴建华 《内蒙古气象》2012,(3):21-22

文章从赤峰市2005—2010年地下水位监测数据及同一时期降水、气温等气象资料,评估地下水位变化情况,分析了降水量、气温等对地下水位变化的影响,地下水位下降对生态环境的影响,并提出了应对地下水位下降的建议及对策。  相似文献