THE SOUTH CHINA SEA SUMMER MONSOON AND THE SEASONAL MODALITY AND WEST EXTENDING OF THE NORTHERN HEMISPHERE PACIFIC SUBTROPICAL HIGH

~~THE SOUTH CHINA SEA SUMMER MONSOON AND THE SEASONAL MODALITY AND WEST EXTENDING OF THE NORTHERN HEMISPHERE PACIFIC SUBTROPICAL HIGH@张韧$Department of Marine Meteorology, Institute of Meteorology, PLA University of Sciences & Technology, Nanjing 211101 China @何金海$Department of Atmospheric Sciences, Nanjing Institute of Meteorology, Nanjing 210044 China @董兆俊$Department of Marine Meteorology, Institute of Meteorology, PLA Uni…     

Seismic reliability analysis of earth slopes under short term stability conditions

Different models were developed for evaluating the probabilistic three-dimensional (3-D) stability analysis of earth slopes and embankments under earthquake loading. The 3-D slope stability model assumed is that of a simple cylindrical failure surface. The probabilistic models evaluate the probability of failure under seismic loading considering the randomness of earthquake occurrence, and earthquake induced acceleration and uncertainties stemming from the discrepancies between laboratory-measured and in-situ values of shear strength parameters. The models also takes into consideration the spatial variabilities and correlations of soil properties. The probabilistic analysis and design approach is capable of obtaining the 2-D and 3-D static and dynamic safety factors, the probability of slope failure, the earthquake induced acceleration coefficient, the yield acceleration coefficient, the earthquake induced displacement, and the probability of allowable displacement exceedance taking into account the local site effect. The approach is applied to a well known landslide case: Congress Street Landslide in Chicago. A sensitivity analysis was conducted on the different parameters involved in the models by applying those models to the Congress Street landslide considering different levels of seismic hazard. Also, a sensitivity analysis was carried out to study the sensitivity of computed results to input parameters of undrained shear strength, and corrective factors. A comparison was made between the different models of failure. The parametric study revealed that the hypocentral distance and earthquake magnitude have major influence on the earthquake induced displacement, probability of failure and dynamic 2-D and 3-D safety factors.     

Mooring system reliability in tropical cyclone and North Sea winter storm environments

The characteristics of waves, winds and currents in a tropical cyclone environment differ significantly from those in a winter storm environment, like the North Sea. This can have a significant effect on the reliability of a mooring system that is designed to satisfy 100 yr conditions with specified Factors of Safety in accordance with ISO19901-7 or API RP 2SK. This paper presents reliability analysis of the mooring system of a permanently connected Floating LNG vessel, placed at two locations: (a) a tropical cyclone environment of the North West Shelf of Australia and (b) a winter storm environment of the North Sea. It is demonstrated that as a result of differences in the long term distribution of environmental parameters (waves, winds) between a North Sea environment and a tropical cyclone environment, the long term distribution of the mooring line response differs significantly in these two locations.This paper shows that a mooring system which is designed in accordance with ISO (or API), in these two environments, will achieve very different reliability levels because of the significant differences in environmental characteristics. In order to achieve the same reliability for the mooring system at these two geographical locations, Factors of Safety for use with 100 yr environmental conditions (Ultimate Limit State) were derived to achieve the same target probability of failure of 10⁻⁴/annum. It was found that for the North Sea environment, a factor of 1.5 is required for both the mooring chain and the pile, while for the tropical cyclone environment the required Factor of Safety has to be increased to 2.1. These differences are very significant and design standards need to be revised to reflect these findings.     

饱和黄土液化标准的试验研究

根据饱和黄土在动荷载振动作用下的试验结果提出了以黄土的3%应变为主要考虑因素的液化破坏标准。试验表明:在固结不排水的动三轴试验中,黄土结构连接强度随循环次数的增加而逐渐丧失,体积收缩,在不排水条件下转化为孔隙水压力的上升和有效应力的下降,最终可能出现初始液化和循环活动性现象。3%轴应变一定出现在初始液化前;3%轴应变后应变大幅增加,孔压有可能达到初始有效固结围压,也有可能在初始液化前破坏。3%轴变形是黄土稳定变形和大幅变形的临界点。     

直剪强度指标的可靠度统计方法

矩法和线性回归法能得到较为准确的岩土抗剪强度指标的均值,但是在统计标准差或变异系数时,矩法常常面临样本容量偏小而导致变异系数偏大的困难,而常规线性回归法无法给出实际所需的抗剪强度指标的标准差。本文从可靠度理论出发,利用正交标准化变量空间中原点到极限状态线最短距离为可靠指标的原理,提出了一种利用Excel规划求解功能求解抗剪强度参数的简便方法。将这一方法应用于91组404个水利水电岩土工程二类岩体与混凝土胶结面大型直剪试验结果的统计中,并将结果与其它方法进行了对比。     

用断裂力学校核带裂纹的船舶螺旋浆轴

本文以实船带裂纹螺旋浆轴为例,应用断裂力学分析方法校核其剩余强度和裂纹扩展速率,判别可用性,然后提出防断裂措施;为断裂力学在船舶机械修理技术中的应用作了一个尝试,补充了船舶机械轴件常规强度校核方法的不足。     

2013年芦山7.0级地震一年尺度预测的回顾性研究——基于三性法、静中动和垂震底继模式

对2013年中期地震预测的研究结果(一年尺度)进行了阐述与分析。该预测综合了三性法判据、静中动判据和垂震底继模式,给出了2013年左右在鲜水河断裂带上发生7级以上大震的可能性很大的结论。重点预测了两个具体发生的区域,预测的区域与2013年4月20日芦山7.0级地震的震源区相差70～80km左右。预测结果震级与时间吻合,但地点上发生了偏离。文中重点回顾研究了基于三性法,静中动、垂震底继方法的预测过程。     

利用Yabuki & Matsu'ura反演方法计算 2011年日本东北地区太平洋海域Mw9.0级地震同震滑动分布

Yabuki & Matsu'ura反演方法是利用ABIC最佳模型参数选取方法和平滑的滑动分布作为约束条件,由形变观测数据计算发震断层滑动分布.本文基于日本列岛同震GPS观测数据和发震断层曲面构造模型,利用Yabuki & Matsu'ura反演方法计算2011年日本东北地区太平洋海域M_w9.0级地震的发震断层同震滑动分布.反演结果表明,断层面上的最大滑动量为35 m,较大滑动分布在浅于30 km的震源中心上部,最大破裂集中在20 km深度的地方.其地震矩约为3.63×10²²N·m,对应的矩震级为M_w9.0.模拟结果显示Yabuki & Matsu'ura反演方法更适用于倾角低于40°的断层模型反演.最后,本文基于上述方法获得的发震断层滑动模型,利用地球体位错理论正演计算该地震在中国及其邻区产生的远场形变,正演计算结果基本可以解释由中国GPS陆态网络观测到的同震形变.     

基于MATLAB的均质土坡稳定可靠度的蒙特卡罗模拟

根据Bishop条分法建立均质土坡的可靠度计算模型,利用MATLAB进行蒙特卡罗方法模拟的程序实现,进行均质土坡的可靠度模拟计算.结果表明土性参数c、ψ在正态分布或对数正态分布情况下,对于边坡可靠度基本没有影响.并将其应用于工程实例分析,取得良好效果,说明可靠度分析方法是对传统的确定性分析方法的有益补充.     

Hybrid particle swarm optimization for first-order reliability method

A reliability analysis method based on the combination of the first-order reliability method (FORM) and hybrid particle swarm optimization (SACPSO) is presented for the reliability optimization calculation. The new reliability method, named as SACPSO-FORM, can be utilized for those complex reliability problems with correlated non-normal variables and implicit performance functions. Three examples are performed to verify its validation, and stability reliability analysis on the complicated rock foundation of a practical gravity dam is demonstrated. The results show that the proposed method is accurate, stable, flexible and efficient for reliability analysis in engineering applications.