Transverse Pipe Research Articles

Field test and numerical simulation of ground settlement in super shallow buried station excavation supported by transverse pipe roof

The pipe roof is an effective means to control the surface settlement during the construction of the super-shallow buried subway station. The transverse pipe roof method can not only reduce the construction work surface, but also improve the construction efficiency by multi-stage flow construction. Based on the transfer station project of the Olympic Sports Center of Jinan Rail Transit Line 3, the ground settlement law caused by the excavation of ultra-shallow buried subway station under the action of transverse pipe roof is analyzed through field measurement. The mechanism of pipe roof controlling ground settlement and the influence of steel pipe spacing and steel pipe length on the bearing mechanism of pipe roof are analyzed by numerical simulation. The following conclusions are drawn. 1) The surface settlement curve caused by the excavation of the small pilot tunnel in the lateral direction of the station is a wavy U-shaped, and the surface settlement curve becomes a smooth U-shaped after the soil is broken. In the longitudinal direction of the station, the surface settlement is jagged, and the surface settlement above the pipe roof is less than the surface settlement between the pipe roofs. 2) After soil excavation, pipe roof can bear the load of surrounding rock and restrain the settlement of soil above, and soil arch effect is formed between pipes to restrain the relaxation of soil between pipes. With the increase of the spacing of the steel pipe, the height of the soil arch increases. After exceeding a certain spacing, the micro-soil arching effect disappears and the surface settlement increases. 3) The length and stiffness of pipe roof will affect the bearing capacity of pipe roof and there is an upper limit. When it exceeds the upper limit, increasing the length or stiffness of pipe roof has little effect on the control effect of ground settlement. The research can provide reference for shallow buried excavation station and other projects.

Study of deformation conditions at longitudinal pipes rolling from austenite steel grades

Stainless steels of austenite class 08–12Х18Н10Т have a high corrosion resistance, which stipulates for their wide application in various areas of industry. Technology of pipes production of the steels is rather specific and requires observation of some conditions. It was shown that temperature of a work-piece heating before deformation is an important parameter of the technology. It was noted that for the piercing of a steel work-piece with various chrome content, there is a rational temperature interval. Nonobservation of the temperature can lead to defects formation on internal pipe surface because of earlier destruction and opening of metal cavity during piercing. The choice of the rolling-out scheme has a direct effect on the work-piece forming in cross-sections. Results of hot rolling of Ø37×2,5 tube samples, manufactured of 08–12Х18Н10Т steel and carbon steel of grade 40 presented. The rolling was done at a laboratory mill. As a result of the experiment the lower limit of ovality of rolls grooves was specified for conditions of rolling of pipes from 08–12Х18Н10Т steels by 2-roll scheme. At the rolling with ovality B/H ≤1,07, defects appeared on the internal tube surface in the form of scratches caused by the mandrel. The rational range of ovality of grooves at multi-stand rolling can be from 1.08 to 1.15. According to criterion of groove overfilling by metal for steels 08–12Х18Н10Т, requirements were formed towards the groove width of the first stand of longitudinal rolling mill. The groove width must be larger than the sleeve diameter: for 3-roll scheme – at least by 2–3%, for 2-roll scheme – at least by 7.0–7.5%. Potential advantages of 3-roll scheme comparing with 2-roll scheme for rolling of 08–12Х18Н10Т steels were established as follows: lower probability of grooves overfilling by metal of the work-piece, absence of defects (scratches caused by mandrel), on the tube internal surface at minimal ovality level of 1.07, lower level of transverse pipe wall non-uniform thickness.

DEM simulations of transverse pipe–soil interaction on sand

Realistic modelling of transverse (i.e. vertical and lateral) pipe–soil interaction plays an important role in predicting the behaviour of untrenched offshore pipelines that are designed to undergo...

Dynamic analysis of large strain deformation of flexible pipes conveying two-phase fluids Part I: linear vibration analysis

This work presents dynamic response of large strain deformed subsea flowlines and jumpers conveying two-phase fluid. Large strain deformation theory is used to analyze the effects of high pressure-high temperature two-phase flow on critical velocity in flexible pipes. Starting with natural frequency of simply supported flexible pipes, corresponding nonlinear transport equations are derived and subsequently expanded using the method of multiple scales perturbation. Frequency response obtained from the linearized leading order equations established that buckling and flutter-like instabilities attend critical velocities. Furthermore, the buckling velocity of transverse pipe decreases with increasing temperature, pressure or tension. Clearly, the transverse buckling velocity is higher in large strain deformation model compared with small strain model. In addition; whereas the critical velocity in the longitudinal direction is independent of temperature, pressure and tension for small strain models; these variables determine the path to failure in large strain deformed pipes.Keywords: Large strain deformation, small strain deformation, simply supported pipe

3D analysis of transverse pipe–soil interaction using 2D soil slices

Offshore pipelines are often laid directly on the seabed, particularly in deep water. Cyclic changes in the temperature and pressure of the pipe contents can lead to cyclic growth and contraction of (planned) lateral buckles. This results in severe plastic deformation of the near-surface soil as it is progressively scraped away and accumulated into berms by the lateral sweeping motion of the pipe. Quantifying the resistance offered by the soil is important in design, notably for fatigue calculations. This paper presents a new computational approach for modelling pipe–soil interaction during events dominated by large transverse pipe displacements. The main novelty is that a three-dimensional (3D) structural model of the pipe interacts with a series of discrete two-dimensional (2D) (plane strain) soil domains. Each ‘slice’ of soil is analysed using a coupled Eulerian–Lagrangian finite-element technique, though other large-displacement numerical methods could be employed. The concept is similar to recently developed macro-element approaches, except that the pipe–soil interaction at each (assumed) planar cross-section is captured by a 2D continuum model rather than by a 2D user-defined spring model. This is more efficient than a full 3D analysis of the pipeline and surrounding soil, yet it allows results of comparable accuracy to be obtained. This paper illustrates the new methodology with a simple calculation.

Predicting phase shift effects for vibrating fluid-conveying pipes due to Coriolis forces and fluid pulsation

Knowing the influence of fluid flow perturbations on the dynamic behavior of fluid-conveying pipes is of relevance, e.g., when exploiting flow-induced oscillations of pipes to determine the fluids mass flow or density, as done with Coriolis flow meters (CFM). This could be used in the attempts to improve accuracy, precision, and robustness of CFMs. A simple mathematical model of a fluid-conveying pipe is formulated and the effect of pulsating fluid flow is analyzed using a multiple time scaling perturbation analysis. The results are simple analytical predictions for the transverse pipe displacement and approximate axial shift in vibration phase. The analytical predictions are tested against pure numerical solution using representative examples, showing good agreement. Fluid pulsations are predicted not to influence CFM accuracy, since proper signal filtering is seen to allow the determination of the correct mean phase shift. Large amplitude motions, which could influence CFM robustness, do not appear to be induced by the investigated fluid pulsation. Pulsating fluid of the combination resonance type could, however, influence CFMs robustness, if induced pipe motions go unnoticed and uncontrolled during CFM operation by feedback control. The analytical predictions offer an immediate insight into how fluid pulsation affects phase shift, which is a quantity measured by CFMs to estimate the mass flow, and lead to hypotheses for more complex geometries, i.e. industrial CFMs. The validity of these hypotheses is suggested to be tested using laboratory experiments, or detailed computational models taking fluid–structure interaction into account.

FLUID TRANSPORT DUE TO NONLINEAR FLUID–STRUCTURE INTERACTION

This work considers nonlinear fluid-structure interaction for a vibrating pipe containing fluid. Transverse pipe vibrations will force the fluid to move relative to the pipe creating unidirectional fluid flow towards the pipe end. The fluid flow induced affects the damping and the stiffness of the pipe. The behavior of the system in response to lateral resonant base excitation is analysed numerically and by the use of a perturbation method (multiple scales). Exciting the pipe in the fundamental mode of vibration seems to be most effective for transferring energy from the shaker to the fluid, whereas higher modes of vibration can be used to transport fluid with pipe vibrations of smaller amplitude. The effect of the nonlinear geometrical terms is analysed and these terms are shown to affect the response for higher modes of vibration. Experimental investigations show good agreement with theoretical predictions.

Jet-drive mechanism in organ pipes

The analysis given by Elder [J. Acoust. Soc. Am. 54, 1554 (1973)] of the mechanism of interaction between a time-varying air jet flow velocity and a resonant organ pipe is extended to deal with the case in which a jet of fixed flow velocity is deflected to cut a sharp pipe lip. Similar terms arise in the analysis but the nonlinearities are less important than in Elder’s case. The generation of higher transverse pipe modes by the jet asymmetry is considered and it is concluded that such modes may play a significant part in coupling ordinary pipe modes to pipe-wall vibrations. Subject Classification: [43]75.60.

Friction and Bearing Loads on Buried Pipes

Abstract Presented here are results of experimental and theoretical investigations of the behavior of downhole pipe, surrounded by Overton sand or gravel, when subjected to shock from nuclear explosion. The principal effects investigated arelongitudinal friction between the pipe and the stemming material andresistance offered by the stemming material to transverse motion of the pipe. Introduction Stemming materials such as Overton sand and pea gravel are widely used in underground nuclear pea gravel are widely used in underground nuclear testing to ensure containment of the explosion. Present-day theories of mechanics suitable for predicting stresses and displacements within an predicting stresses and displacements within an array of particles of such materials are rather limited because of the stress-strain-time behavior and complicated boundary conditions involved. Thus, measurements representing gross effects only and linearized models of analysis must be relied upon in making the majority of engineering decisions where soil-structure interactions are encountered. Furthermore, because of the number of variables and hardware constraints present in designing deep-hole emplacement systems, the emphasis should be on obtaining experimental data on fullscale or nearly full-scale structural components in association with stemming materials of actual field quality. The experiment discussed in this paper was directed toward the development of basic mechanical properties such as modulus of elasticity, friction characteristics during axial (longitudinal) pipe motion through stemming materials, resistance pipe motion through stemming materials, resistance of stemming materials to transverse pipe displacement, and related physical phenomena that may have further bearing on the usual mechanical properties employed in various design analyses. properties employed in various design analyses. During evaluation of the basic mechanical properties, an attempt was made to develop a properties, an attempt was made to develop a Poisson's ratio type of data for the stemming Poisson's ratio type of data for the stemming materials at hand by using both specialized equipment and standard test equipment normally employed in soil mechanics. The results of the study, however, should be interpreted with due regard to the particulate nature of stemming materials, which do not represent a continuum with well defined stress-strain relationships. To obtain meaningful data on friction and transverse resistance characteristics, a special test rig was designed with particular emphasis on minimizing the scale effects and experimental errors usually encountered. In mechanics the term "friction" is the resistance to motion of two moving objects or surfaces that touch. In this paper we speak of several different types of micron, and therefore some clarification is needed. The friction between sand or gravel and the down-hole pipe as we attempt to move the pipe is one type of friction. A similar type is the friction developed between sand or gravel and the steel block it rubs against in the direct shear test apparatus. Those two examples of friction are rather straightforward, however, the following two present some confusion because they are both referred to as internal friction:Internal friction as used by engineering scientists, physicists, and metallurgists may be defined as the conversion of the mechanical energy of a vibrating solid into heat. This is also referred to as the damping capacity and corresponds to a phase difference between the applied stress and phase difference between the applied stress and its resultant strain.b soil mechanics the concept of internal friction corresponds to friction between the surfaces of individual grains of sand or gravel. In granular materials, both kinds of internal friction occur. In this paper the term "internal friction" is referred to extensively and is used exclusively in the sense of friction between particles. particles. FUNDAMENTALS OF SOIL MECHANICS The mechanical behavior of earth materials such as sand or gravel can be described by suitable physical constants reflecting certain physical constants reflecting certain stress-deformation relations that may then be applied in customary engineering predictions. In dealing with the rigidity of rocks, Young's modulus, E, and Poisson's ratio, are commonly used, and soil Poisson's ratio, are commonly used, and soil mechanics utilizes basic concepts of the theory of elasticity. By analogy to this well established practice, related concepts utilizing elastic practice, related concepts utilizing elastic constants in loading and unloading can be made applicable to stemming materials. SPEJ P. 163

Heat Transfer between Metal Pipes and a Stream of Air

The paper describes measurements on the heat transfer from iron and copper pipes of diameters ranging from to 3 inches, at various temperatures up to 90 deg. C. in air moving with velocities up to 30 ft. per sec. when the axis of the pipe is placed transverse to the stream of air. An iron pipe of external diameter inches was also tested when placed longitudinally along the direction of the air stream and subdivided into sections, the heat loss from various sections being measured. This loss is greatest at the section where the air first meets the pipe, and gradually falls off along the pipe. If the air is artificially made turbulent, the loss from all the sections shows an increase, the greatest change being shown by the first section. The heat loss from a longitudinal pipe is of the order of one-half that from a transverse pipe. A number of similar iron pipes of inches diameter were studied when arranged in banks in square formation. In this case the second layer of pipes met by the air loses more heat than the first layer, the third layer losing the same as the second. It is suggested that this is due to the eddy motion set up in the air when it passes the first layer, no further increase in the eddy motion occurring afterwards. In the diagonal formation with rows inches apart, the first section again loses least heat. In this case not only is the loss in the second row greater than that in the first, but there is a further increase in passing from the second to the third row, after which the coefficient is constant. When air impinging on a bank in staggered formation is artificially made turbulent, the heat loss from every row is increased to such an extent that the first row loses more heat under these conditions than the third row when there is no artificial turbulence. In addition, an investigation was carried out with pipes below 0 deg. C. If there is no ice or snow deposit on the pipes, the curve connecting H/kθ with Vd/ v is the same as for hot pipes. Here H is the heat loss per unit length, d the external pipe diameter, and θ the temperature excess, whilst k, V, and v are the conductivity, velocity, and kinematic viscosity of the air. Pipes below 0 deg. C. may become covered with a deposit of ice or snow, and in this case the interpretation of the results is less straightforward. If d and θ in the above formulae refer to the actual pipe diameter and temperature difference between the pipe and the air, then the smooth curve through the observations is again identical, within experimental error, with that for hot pipes. This can only be a coincidence, the insulating value of the deposit being compensated by the greater area presented to the wind, since the effective pipe diameter has become larger, and has a higher surface temperature than that of the metal. From the result for dry pipes, it would be expected that if d′ refers to the overall diameter, and θ′ represents the difference between the air and the outer surface of the deposit, this new curve would coincide with that for hot pipes. The experimental results show that this is so if the outer surface of the deposit is dry, but that if the conditions are such that water is dripping off, the heat transfer may be 30 per cent greater than the normal amount.