北京地铁浅埋暗挖施工坍塌的预防与处理

文章根据北京地质环境状况,介绍浅埋暗挖施工坍塌的预防及处理措施。     

汽车与不同形式高速公路护栏碰撞的试验研究

汽车与高速公路护栏碰撞事故中,护栏不仅有拦截、导向作用,还要有良好的缓冲吸能特性,以减小由于乘坐空间过度变形以及人与车内物体二次碰撞对乘员的伤害。通过实车与两种不同形式护栏的碰撞试验,研究车辆、护栏碰撞中的动态响应,分析护栏、汽车和乘员的特性以及相互关系;护栏的不同结构形式与安装方式对乘员的安全性的影响,为高速公路护栏的设计、施工以及在不同地点的设置提供有益的借鉴。     

泥水盾构过江工程江底塌方风险的应对及处理

泥水盾构过江工程的重大挑战之一是江底塌方的处理,正确地分析坍方的原因和采取有效的措施是应对风险的关键。文章结合工程实例对江底坍方的应对及处理进行了分析研究。     

公路隧道围岩塌方离散元模拟

以秦岭III号隧道为工程实例,根据围岩类别及围岩内地质构造发育状况,将断面划分为2 173个块体单元,采用离散单元法对该隧道的塌方过程进行了二维数值仿真模拟,得出了隧道顶部和侧壁块体的塌落距离、塌落轨迹及隧道塌方量,并得出了块体塌落过程中跟踪块体的合力曲线,反映了块体的运动过程。     

船用永磁同步电动机矢量控制系统仿真

随着大功率交流电机控制技术的快速发展,电力推进技术逐渐取代了传统的船舶动力装置。本文对船用永磁同步电动机矢量控制系统进行仿真研究,通过在二维旋转坐标系中建立船用永磁同步电动机的数学模型,计算出电机在正常工作时的各项参数,搭建船用永磁同步电动机的闭环仿真模型。最后用Matlab对该模型进行模拟仿真。仿真结果表明,该模型能够充分反映实际系统,能够给实物开发提供正确的思路。     

Experimental study on dynamic response of a floating offshore wind turbine under various freak wave profiles

This study performed experimental investigation on the dynamic response of an in-place floating offshore wind turbine (FOWT) under freak wave actions. Based on the method of wave profile modulation, various freak wave profiles embedded in unidirectional Gaussian seas were generated in wave basin and the action of these waves on the FOWT was measured and analyzed, which has not been done before. The motions of FOWT were analyzed in time domain as well as time-frequency domain. The effect of freak wave parameters on FOWT motions was addressed, i.e., freak wave height, freak wave period, large crest, and deep trough. The dynamic response of FOWT was observed as a spike at the occurrence of freak wave in a conventional random wave, where the impact of freak wave can last for 17 spectral peak periods of wave. Data analysis shows that the motions of FOWT increased linearly with the freak wave height. In addition, the occurrence of freak wave induced the coupled effect on surge and pith, which was strengthen with the increase of freak wave height and wave period. Compared to a large crest, a deep trough of freak wave led to stronger motions and was supposed to be a key concern on the safety of the FOWT. The novel findings in this study provided a reference for the design of survival load on a FOWT and benchmarks for validating numerical models.     

Numerical investigation of the collapse pressure of concentric tubes with frictionless and tied interface

The understanding and study of the mechanical behavior of submarine pipes have significant relevance in ocean exploration, allowing the application of these structures in adverse conditions. In this sense, protecting the tube's internal surface is vital for the transportation of corrosive materials, threatening structural integrity. Usually, the external surface is at constant hydrostatic pressure, leading to possible structural failure if the project does not consider all failure modes. Within the framework of Metallurgically Cladded Pipes (MCP) and Mechanically Lined Pipes (MLP), Corrosion-Resistant Alloys (CRAs) are inserted in the internal surface of pipelines. However, they are not typically deemed in the structural analysis as an integrant part of the mechanical resistance for the external load. This work presents an initial analytical proposal to calculate the collapse pressure of concentric tubes incorporating the rigidity provided by the CRA. Tied or frictionless numerical models are assumed to describe the interaction between the two bodies at the interface region. These two scenarios establish the upper and lower boundaries for cases where friction is part of the problem. The methodology applies a least-square minimization function based on nonlinear finite element simulations to extract analytical expressions that estimate the collapse pressure. An effort is made to reduce the number of sensitive parameters involved in the analytical proposals and minimize the complexity of the formulation. This process allows the analyst to visualize which parameters are more relevant in various scenarios. Nevertheless, the main goal is to evaluate how the variables are coupled and develop a methodology that can be adapted to reproduce the analyst's necessities.