On the response of a free span pipeline subjected to ocean currents

A mechanistic study is performed to examine the coupling between the in-line and the cross-flow motion of a cylindrical structure subjected to current forces. The structure represents a free span pipeline but concerns marine risers as well.A time domain model is formulated in which the in-line and cross-flow deflections are coupled through the axial tension which in turn is computed from the pipeline prolongation at any time. This formulation introduces time dependent tensions and non-linearity into the problem.Preliminary validation of the model simulations vs. physical test data are carried out for one specific case to ensure that the sag and the in-line deflection are correctly resolved by the model. Using this as the initial condition a series of calculations are carried out to examine cross-flow induced deflections induced by an in-line prescribed deflection and vice versa. Finally, an idealistic simulation of flow induced vibration is presented.The model simulations demonstrate that the coupling varies with the mode shape and with which component it is initially introduced into. However, it is evident that the coupling effects may be significant and not negligible.     

Estimation of scour around submarine pipelines with Artificial Neural Network

The process of scour around submarine pipelines laid on mobile beds is complicated due to physical processes arising from the triple interaction of waves/currents, beds and pipelines. This paper presents Artificial Neural Network (ANN) models for predicting the scour depth beneath submarine pipelines for different storm conditions. The storm conditions are considered for both regular and irregular wave attacks. The developed models use the Feed Forward Back Propagation (FFBP) Artificial Neural Network (ANN) technique. The training, validation and testing data are selected from appropriate experimental data collected in this study. Various estimation models were developed using both deep water wave parameters and local wave parameters. Alternative ANN models with different inputs and neuron numbers were evaluated by determining the best models using a trial and error approach. The estimation results show good agreement with measurements.     

空间管线间最短距离研究

空间管线是城市、矿山、石油等领域的重要基础设施。本文首先介绍了空间管线的抽象表示方法,建立了管线数据结构,然后论述了空间管线最短距离的计算过程和算法实现,最终提出了有效解决工程实际中空间异面管线最短距离问题的方法。     

我国非开挖行业现状与展望

概述了常用的各类非开挖施工技术方法及非开挖施工的主要优势;介绍了我国非开挖行业的3个发展阶段,目前的发展现状,以及存在的主要问题;对我国非开挖技术的市场前景进行了分析判断。     

感应法地下管线探测中的一个问题

通过对地下管线中的感应电流形成机理分析,本文认为,当地下介质导电性很差时,地下管线以磁偶极线为主;而当地下介质存在一定的导电性时,管线则等效于电流线。     

水平定向钻进铺设管线的测量技术

对于安全优质水平定向钻进铺设管线来说，测量技术至关重要。介绍了施工前对已有地下管线和土层的探测、钻进时对钻头的跟踪和导航、以及铺设管线前后的测量问题，还介绍了测量仪器的工作原理、基本性能和适用范围。     

Study on Model Tests and Hydrodynamic Force Models for Free Spanning Submarine Pipelines Subjected to Earthquakes

A test rig is built to model the dynamic response of submarine pipelines with an underwater shaking table in the State Key Laboratory of Coastal and Offshore Engineering, Dalian University of Technology, China. Model tests are carried out to consider the effects of exciting wave directions and types. Based on the experimental results, two hydrodynamic force models derived from Morison equation and Wake model are presented respectively. By use of hydrodynamic force models suitable for free spanning submarine pipelines under earthquakes, discretized equations of motion are obtained and finite element models are established to analyze dynamic response of free spanning submarine pipeline subjected to multi-support seismic excitations. The comparison of numerical results with experimental results shows that the improved Morison and Wake hydrodynamic force models could satisfactorily predict dynamic response on the free spanning submarine pipelines subjected to earthquakes.     

城市地下管线探测工程质量控制

在城市地下管线探测过程中,质量精度控制应建立在严谨的量化分析和数据表述基础上并贯穿于质量控制全过程,以确保探测成果满足现行技术标准的要求。     

深基坑施工周边管线变形监测分析和处理

在基坑开挖过程中,由于应力环境改变,造成附近管线位移较大。该工程进行了系统监测,根据监测数据对周边管线的变形进行较系统的分析和变形处理。