Selection of Water Transmission Method and Analysis of Pipe Network Zoning in Municipal Water Supply and Drainage Design

With the acceleration of urbanization,the demand for water supply and drainage pipe networks has increased significantly.In the planning of urban construction,it is necessary to optimize the design of the water supply and drainage system pipe network to effectively save energy while providing residents with more accessible water resources.Therefore,the municipal water supply and drainage system and the water transmission methods should be designed according to the geographical conditions of the city.In this paper,we mainly analyze the design of municipal water supply and drainage systems and the selection of water transmission methods.Besides,the optimization of the water supply and drainage network zoning process and pipe network maintenance is also discussed,so as to provide a reference for municipal water supply and drainage work.

Parametric resonance of axially functionally graded pipes conveying pulsating fluid

Based on the generalized Hamilton's principle,the nonlinear governing equation of an axially functionally graded(AFG)pipe is established.The non-trivial equilibrium configuration is superposed by the modal functions of a simply supported beam.Via the direct multi-scale method,the response and stability boundary to the pulsating fluid velocity are solved analytically and verified by the differential quadrature element method(DQEM).The influence of Young's modulus gradient on the parametric resonance is investigated in the subcritical and supercritical regions.In general,the pipe in the supercritical region is more sensitive to the pulsating excitation.The nonlinearity changes from hard to soft,and the non-trivial equilibrium configuration introduces more frequency components to the vibration.Besides,the increasing Young's modulus gradient improves the critical pulsating flow velocity of the parametric resonance,and further enhances the stability of the system.In addition,when the temperature increases along the axial direction,reducing the gradient parameter can enhance the response asymmetry.This work further complements the theoretical analysis of pipes conveying pulsating fluid.

An Efficient Reliability-Based Optimization Method Utilizing High-Dimensional Model Representation and Weight-Point Estimation Method

The objective of reliability-based design optimization(RBDO)is to minimize the optimization objective while satisfying the corresponding reliability requirements.However,the nested loop characteristic reduces the efficiency of RBDO algorithm,which hinders their application to high-dimensional engineering problems.To address these issues,this paper proposes an efficient decoupled RBDO method combining high dimensional model representation(HDMR)and the weight-point estimation method(WPEM).First,we decouple the RBDO model using HDMR and WPEM.Second,Lagrange interpolation is used to approximate a univariate function.Finally,based on the results of the first two steps,the original nested loop reliability optimization model is completely transformed into a deterministic design optimization model that can be solved by a series of mature constrained optimization methods without any additional calculations.Two numerical examples of a planar 10-bar structure and an aviation hydraulic piping system with 28 design variables are analyzed to illustrate the performance and practicability of the proposed method.

DIFFERENTIAL QUADRATURE METHOD TO STABILITY ANALYSIS OF PIPES CONVEYING FLUID WITH SPRING SUPPORT

It is a new attempt to extend the differential quadrature method(DQM) to stability analysis of the straight and curved centerlinepipes conveying fluid. Emphasis is placed on the study of theinfluences of several parameters on the critical flow velocity.Compared to other methods, this method can more easily deal with thepipe with spring support at its boundaries and asks for much lesscomputing effort while giving ac- ceptable precision in the numericalresults.

NUMERICAL SOLUTION OF FLUID-STRUCTURE INTERACTION IN LIQUID-FILLED PIPES BY METHOD OF CHARACTERISTICS

Fluid-structure interaction （FSI） is essentially a dynamic phenomenon and always exists in fluid-filled pipe system. The four-equation model, which has been proved to be effective to describe and predict the phenomenon of FSI due to friction coupling and Poisson coupling being taken into account, is utilized to describe the FSI of fluid-filled pipe system. Terse compatibility equations are educed by the method of characteristics （MOC） to describe the fluid-filled pipe system. To shorten computing time needed to get the solutions under the condition of keeping accuracy requirement, two steps are adopted, firstly the time step Δt and divided number of the straight pipe are optimized, sec-ondly the mesh spacing Δz close to boundary is subdivided in several submeshes automatically ac-cording to the speed gradient of fluid. The mathematical model and arithmetic are validated by com-parisons between simulation solutions of two straight pipe systems and experiment known from lit-erature.

Dynamic Analysis of Deep-Ocean Mining Pipe System by Discrete Element Method

The dynamic analysis of a pipe system is one of the most crucial problems for the entire mining system. A discrete element method （DEM） is proposed for the analysis of a deep-ocean mining pipe system, including the lift pipe, pump, buffer and flexible hose. By the discrete element method, the pipe is divided into some rigid elements that are linked by flexible connectors. First, two examples representing static analysis and dynamic analysis respectively are given to show that the DEM model is feasible. Then the three-dimensional DEM model is used for dynamic analysis of the mining pipe system. The dynamic motions of the entire mining pipe system under different work conditions are discussed. Some suggestions are made for the actual operation of deep-ocean mining systems.

Methods for assessing the grooving corrosion of high-frequency electric resistance welded pipes

Grooving corrosion is a major form of corrosion and is prone to occur when high-frequency electric resistance welded （HFW） pipes are being used. Therefore,grooving corrosion is one of the performance indexes of HFW products. Grooving corrosion usually occurs along the welding fusion line, resulting in one or more corrosion grooves. The main factors affecting grooving corrosion include the contents of alloying elements and impurities （especially sulphur） in the steel,the microstructure of the welds and the steel substrate, welding parameters and the service environment as well. In this study, the existing methods for assessing grooving corrosion were systematically reviewed, improvements and new methods were proposed and developed to overcome the shortcomings of the existing methods, such as inaccuracy and excessive research time. By comparison with the existing methods, the operational procedures and the characteristics of the new methods are introduced, and issues regarding the behavior of grooving corrosion and their assessment methods, which both need further research,are discussed in this study.

Effect of pipe characteristics in umbrella arch method on controlling tunneling-induced settlements in soft grounds

Recent developments in tunneling have stimulated design practitioners to more effectively utilize the underground spaces.However,tunneling at shallow depth in soft grounds gives rise to concerns associated with tunnel instability.Umbrella arch method(UAM),as a pre-reinforcement approach of tunnels in complex geological conditions,is widely used to maintain the tunnel stability.Quantitative assessment of the impacts of the entire approach and forepoling pipe features on tunnel stability remains challenging due to the complex nature of the UAM application.This study aimed to assess the effect of pipe design parameters on reinforcing the tunnels excavated in soft grounds.This practical investigation considered the actual field conditions attributed to the tunneling procedure and UAM deployment.Then,the tunneling process was modeled and the tunnel excavation-induced settlements were calculated.The post-processed results confirmed that deploying the UAM substantially reduced the tunnel crown and ground surface settlements by 76%and 42%,respectively.Investigation of various design parameters of pipes underscored the significance of incorporating the optimum value for each individual parameter into design schemes to more effectively control the settlements.Additionally,contrasting the settlement reduction rates(SRRs)for pipe design variables showed that the tunnel stability is more sensitive to the changes in the values of diameter and length,compared to values of the installation angle and center-tocenter distance of the pipes.

Effect of Application of Pipe Roof Method by Using Pipe Jacking on Behavior of Surrounding Soil

Tunnels in an urban area, in many cases, are constructed in soft ground which contains underground water, near existing facilities and structures. Structural stability for the tunnel and also the nearby structures and facilities is vital in this kind of work. Slurry pipe jacking was firmly established as a special method for the non-disruptive construction of underground pipelines of sewage systems. This method utilizes mud slurry that is formed around the pipes in order to stabilize the surrounding soil. In the pipe roof method the tubing elements that are constructed by slurry pipe jacking are near each other longitudinally, and create a rigid and stable lining before the excavation of the main tunnel. This paper discusses ＇the application of a slurry pipe jacking system on ＇the pipe roof method by means of numerical analysis. Because of the rigid behavior of the lining, the results show little subsidence, making this method a reliable method of constructing large tunnels with small cover in an urban area.

An improved outer pipe method for expansive pressure measurement of static cracking agents

Static cracking agent(SCA)is actively investigated as an alternative to explosive blasting for rock breakage due to its immense expansion property.SCA can eliminate the negative effects of shock,noise and harmful gases encountered in explosive blasting processes.Accurate measurement and deep understanding of the expansive properties of SCAs are important in their industrial application.An improved outer pipe method(OPM),termed the upper end surface method(UESM),is proposed in this paper to overcome the shortcomings of the OPM in the expansive pressure measurement of SCAs.Numerical simulation is used to proof the concept and a mathematical model established to relate the internal pressure and the radial strains at different positions in the upper end surface method test equipment.The new equipment is calibrated using oil pressure and strain measurements.The calibrated equipment is then used to measure the expansion pressure of SCA at three different water contents to proof its potential.The differences in the measurements with OPM and UESM at three different moisture contents are less than 4%.The experimental results confirm the accuracy and applicability of the more user friendly and less expensive UESM in the measurement of the expansive pressures of SCAs.

Adjacent mode resonance of a hydraulic pipe system consisting of parallel pipes coupled at middle points

The coupling vibration of a hydraulic pipe system consisting of two pipes is studied.The pipes are installed in parallel and fixed at their ends,and are restrained by clips to one bracket at their middle points.The pipe subjected to the basement excitation at the left end is named as the active pipe,while the pipe without excitation is called the passive pipe.The clips between the two pipes are the bridge for the vibration energy.The adjacent natural frequencies will enhance the vibration coupling.The governing equation of the coupled system is deduced by the generalized Hamilton principle,and is discretized to the modal space.The modal correction is used during the discretization.The investigation on the natural characters indicates that the adjacent natural frequencies can be adjusted by the stiffness of the two clips and bracket.The harmonic balance method(HBM)is used to study the responses in the adjacent natural frequency region.The results show that the vibration energy transmits from the active pipe to the passive pipe swimmingly via the clips together with a flexible bracket,while the locations of them are not node points.The adjacent natural frequencies may arouse wide resonance curves with two peaks for both pipes.The stiffness of the clip and bracket can release the vibration coupling.It is suggested that the stiffness of the clip on the passive pipe should be weak and the bracket should be strong enough.In this way,the vibration energy is reflected by the almost rigid bracket,and is hard to transfer to the passive pipe via a soft clip.The best choice is to set the clips at the pipe node points.The current work gives some suggestions for weakening the coupled vibration during the dynamic design of a coupled hydraulic pipe system.

Thermal field in water pipe cooling concrete hydrostructures simulated with singular boundary method

The embedded water pipe system is often used as a standard cooling technique during the construction of large-scale mass concrete hydrostructures. The prediction of the temperature distribution considering the cooling effects of embedded pipes plays an essential role in the design of the structure and its cooling system. In this study, the singular boundary method, a semi-analytical meshless technique, was employed to analyze the temperature distribution. A numerical algorithm solved the transient temperature field with consideration of the effects of cooling pipe specification, isolation of heat of hydration, and ambient temperature. Numerical results are verified through comparison with those of the finite element method, demonstrating that the proposed approach is accurate in the simulation of the thermal field in concrete structures with a water cooling pipe.

Transmission loss simulation based on rectangular-pulse method and experimental evaluation of acoustic performance of perforated intake pipe

Exact simulation of the acoustic performance is essential to the engineering application for a vehicle intake system. The rectangular-pulse method based on the computational fluid dynamics approach was employed for calculating the transmission loss. Firstly, the transmission loss of the single-cavity element was simulated without any airflow, and the effects of different structural parameters on the acoustic performance were investigated comprehensively. Secondly, the static transmission loss of the perforated intake pipe was obtained by the rectangular-pulse method, which is proved to be accurate enough compared with the result by finite element method. Thirdly, under the different conditions of the mean airflow and the operating temperature, the specific transmission loss was acquired respectively. In general, the peaks of the transmission loss are shifted to the lower frequency range because of the reverse airflow, but the amplitudes are irregularly changed. Besides, when the operating temperature increases, the peaks are shifted to the higher frequencies. Finally, with the designed perforated pipe installed to the intake system, the road tests were proceeded to evaluate the actual acoustic performance, and the result indicates that the intake sound pressure level is greatly attenuated. Typically in the range of 600–1500 Hz, the insertion loss of the intake noise at the decelerating moment is almost 20 d B(A), and the overall noise is reduced more than 14.2 d B(A). In conclusion, the perforated intake pipe has been proved excellent in improving the acoustic performance of intake system and could provide the guidance for the automotive engineering application.

A Frost Heaving Prediction Approach for Ground Uplift Simulation Due to Freeze-Sealing Pipe Roof Method

Freeze-sealing pipe roof method is applied in the Gongbei tunnel,which causes the ground surface uplift induced by frost heave.A frost heaving prediction approach based on the coefficient of cold expansion is proposed to simulate the ground deformation of the Gongbei tunnel.The coefficient of cold expansion in the model and the frost heaving rate from the frost heave test under the hydration condition can achieve a good correspondence making the calculation result closer to the actual engineering.The ground surface uplift along the lateral and longitudinal direction are respectively analyzed and compared with the field measured data to validate the model.The results show that a good agreement between the frost heaving prediction model and the field measured data verifies the rationality and applicability of the proposed model.The maximum uplift of the Gongbei tunnel appears at the center of the model,gradually decreasing along with the lateral and longitudinal directions.The curve in the lateral direction presents a normal distribution due to the influence of the constraint of two sides,while the one along the lateral direction shapes like a parabola with the opening downward due to the temperature field distribution.The model provides a reference for frost heaving engineering calculation.

Discrete Tracer Point Method to Evaluate Turbulent Diffusion in Circular Pipe Flow

Diffusion of a solute in turbulent flows through a circular pipe or tunnel is an important aspect of environmental safety. In this study, the diffusion coefficient of turbulent flow in circular pipe has been simulated by the Discrete Tracer Point Method (DTPM). The DTPM is a Lagrangian numerical method by a number of imaginary point displacement which satisfy turbulent mixing by velocity fluctuations, Reynolds stress, average velocity profile and a turbulent stochastic model. Numerical simulation results of points’ distribution by DTPM have been compared with the analytical solution for turbulent plug-flow. For the case of turbulent circular pipe flow, the appropriate DTPM calculation time step has been investigated using a constantβ, which represents the ratio between average mixing lengths over diameter of circular pipe. The evaluated values of diffusion coefficient by DTPM have been found to be in good agreement with Taylor’s analytical equation for turbulent circular pipe flow by givingβ=0.04 to 0.045. Further, history matching of experimental tracer gas measurement through turbulent smooth-straight pipe flow has been presented and the results showed good agreement.

A novel way for vibration control of FGM fluid-conveying pipes via NiTiNOL-steel wire rope

In this study,a coupling model of fluid-conveying pipes made of functionally graded materials(FGMs)with NiTiNOL-steel(NiTi-ST)for vibration absorption is investigated.The vibration responses of the FGM fluid-conveying pipe with NiTi-ST are studied by the Galerkin truncation method(GTM)and harmonic balance method(HBM).The harmonic balance solutions and the numerical results are consistent.Also,the linearized stability of the structure is determined.The effects of the structure parameters on the absorption performance are also studied.The results show that the NiTi-ST is an effective means of vibration absorption.Furthermore,in studying the effect of the NiTi-ST,a closed detached response(CDR)is first observed.It is noteworthy that the CDR may dramatically change the vibration amplitude and that the parameters of the NiTi-ST may determine the emergence or disappearance of the CDR.This vibration absorption device can be extended to offer more general vibration control in engineering applications.

Development of New Methodology for Distinguishing Local Pipe Wall Thinning in Nuclear Power Plants

To manage the wall thinning of carbon steel piping in nuclear power plants, the utility of Korea has performed thickness inspection for some quantity of pipe components during every refueling outage and determined whether repair or replacement after evaluating UT data. Generally used UT thickness data evaluation methods are Band, Blanket, and PTP (Point to Point) methods. Those may not desirable to identify wall thinning on local area caused by erosion. This is because the space between inspecting points of those methods are wide for covering full surface being inspected components. When the evaluation methods are applied to a certain pipe component, unnecessary re-inspection may also be generated even though wall thinning of components does not progress. In those cases, economical loss caused by repeated inspection and problems of maintaining the pipe integrity followed by decreasing the number of newly inspected components may be generated. EPRI (Electric Power Research Institute in USA) has suggested several statistical methods such as FRIEDMAN test method, ANOVA (Analysis of Variance) method, Monte Carlo method, and TPM (Total Point Method) to distinguish whether multiple inspecting components have been thinned or not. This paper presents the NAM (Near Area of Minimum) method developed by KEPCO-E & C for distinguishing whether multiple inspecting components have been thinned or not. In addition, this paper presents the analysis results for multiple inspecting ones over three times based on the NAM method compared with the other methods suggested by EPRI.

盾构隧道下穿高铁路基变形影响规律及加固优化研究

为研究盾构隧道下穿高铁路基施工时对路基的影响规律,探究在隧道开挖过程中运用不同加固措施对既有高铁路基的影响程度。以西安市某地铁工程为依托,利用室内模型试验对比分析盾构隧道下穿高铁CFG桩复合路基过程中,无加固、超前管幕工法加固与地表袖阀管注浆加固3种隧道施工条件下,地表沉降值和沉降槽的空间分布规律;采用数值模拟分析验证超前管幕工法加固工况下盾构隧道下穿时,高铁路基、道床的位移变化规律。室内模型试验结果表明:盾构隧道施工中采用管幕工法加固后复合地基正上方的地表沉降最大值减小28.6%,采用袖阀管注浆加固后减小18.0%,并且采用两种加固措施后的CFG桩最大附加轴力均减小20%以上。因此,在隧道掘进过程中采用一定加固措施,可改善围岩稳定性,其中管幕工法加固效果更为显著。数值模拟分析表明:采取管幕工法加固施工与不采取加固措施相比,路基最大沉降量减少33.78%,道床最大沉降量减少45.08%。因此,管幕工法加固能够有效减小对既有高铁路基的影响。

重庆官栈河大桥主桥主墩基础锁口钢管桩围堰加固

重庆官栈河大桥主桥为(62+110+62)m三跨连续刚构桥,主墩基础采用锁口钢管桩围堰施工。围堰施工正常水位+325.300 m,施工期控制水位+330.500 m。在该桥主墩围堰完成四周锁口钢管桩插打及前4道内支撑安装后,因极端天气原因,长寿湖水位上涨到+332.200 m,危及围堰安全。为解决钢管桩围堰的安全问题,提出采用水下施工内支撑的加固方案。待围堰内部水头与外部保持一致后,将已经插打的锁口钢管桩加高至标高+334.000 m,拆除已安装好的4道内支撑,重新安装6道内支撑。采用MIDAS Civil软件分别建立加固前、后钢管桩围堰结构有限元模型,分析钢管桩及内支撑的受力安全与稳定性。结果表明:施工控制水位+330.500 m下,围堰结构最大正应力由加固前的162.6 MPa下降到加固后的82.3 MPa,下降了49.3%;承载水位可从施工控制水位+330.500 m增加到目标控制水位+333.500 m,且强度和刚度等均留有一定储备。水下施工内支撑的加固方案可提升围堰的承载能力。该桥围堰加固后整体受力效果良好,已顺利完成承台浇筑施工。

反拉式顶管法施工联络通道对地铁盾构隧道力学性能影响

为探究采用反拉式顶管法施工盾构隧道联络通道过程中主隧道的力学响应机制,依托北京地铁某盾构区间,建立模拟联络通道施工过程的有限元模型,通过与现场监测数据对比验证模型的准确性。继而研究联络通道施工对主隧道管片间错台位移、特殊管片应力及变形、螺栓受力的影响,并分析反力模式对主隧道管片力学特性的影响。结果表明:1)始发管片破除对主隧道力学性能影响较大,随着联络通道进一步开挖,主隧道受力和变形缓慢增大。2)管片间最大错台位移为1.17 mm,发生在特殊管片与普通管片接缝底部。特殊管片最大拉应力为18.6 MPa,出现在开口的顶、底部;最大压应力为27.0 MPa,出现在开口的腰部;最大横向扩张位移和竖向收敛位移分别为2.13 mm和4.56 mm。主隧道管片环间螺栓最大拉应力为213 MPa。3)背推式反力模式更利于控制开口处的横、竖向位移,反拉式反力模式更利于控制开口对面管片应力变形及其接缝处错动位移。