Pipe Strain Research Articles

Response of perforated pipes buried in sand under lateral soil-pipe movements

The use of perforated pipes can be seen increasingly in many applications to facilitate drainage/infiltration of liquid through opening channels in the pipe wall. Design of perforated pipes lacks consideration for lateral soil-pipe interaction induced by differential ground movement, which can generate large pipe stresses and strains. In this study, in-air three-point bending tests were conducted on perforated pipes, which were subsequently evaluated through lateral dragging tests. The mechanical responses of perforated pipes with different hole diameters (d), spacings between holes (s), and layers of holes (l) were interpreted. It is found that the load-displacement curves for all tests generally did not show significant difference. The pipe wall thickness had a significant impact on midspan deflection, reflecting by the smallest midspan deflection due to a higher flexural rigidity. All tested perforated pipes were safe, since the maximum pipe strains were well below the linear elastic limit of 3% for polyvinyl chloride (PVC) material. Finally, the efficacy of two prediction methods was assessed. The approach of Cholewa et al. (2009) provided relatively close estimations, while the solution of Ye et al. (2023a) was suitable for use at relatively small pipe end displacements before the mobilization of peak soil resistance.

A simplified analytical solution of pipeline response under normal faulting

Buried pipelines are one of the critical lifeline structures, and the evaluation of pipeline performance under seismic faulting is essential for protection of pipeline networks. This paper explores an analytical solution incorporating implementation of Winkler models around a beam-type structure using the finite difference method to evaluate the pipeline response under normal faulting. The effectiveness of the analytical solution is assessed by comparing the calculated pipe strains with centrifuge and full-scale laboratory testing measurements. Subsequently, the effect of pipe size, faulting condition, and burial condition on pipe response are investigated. It can be found that a pipeline with a smaller pipe wall thickness or larger pipe diameter is generally more prone to failure. Larger pipe wall thickness or lower D/t ratio should be used for pipe design crossing an active fault. In geotechnically problematic areas, shallow burial depth and less stiff soil with lower modulus are recommended to reduce the probability of exceedance of allowable limit states due to normal faulting. In the end, empirical functions relating to critical D/t ratio are proposed to evaluate the critical states of fault displacement, burial depth, and spread of fault rupture with different diameter-to-thickness ratio considering the controlled limit of failure modes.

Long-term performance of concrete pipes under fatigue traffic loads

In recent years, there has been a concerning increase in road collapses triggered by failures in urban drainage systems. Concrete pipes, commonly uesd in urban drainage pipelines, endure prolonged cyclic loading from traffic above. However, the mechanisms governing the long-term performance and fatigue damage remain unclear. Through conducting fatigue model box tests on concrete pipes, the effects of different fatigue loading cycles on the circumferential strain of concrete pipes were investigated. A fatigue life prediction equation for concrete pipes was proposed, and the crack propagation under various fatigue loading cycles was observed. Additionally, corresponding 3D FE models of concrete pipe-soil interaction with bell-and-spigot joints and gaskets were constructed. These models were used to explore the vertical displacements, circumferential bending moments, and circumferential stresses of the concrete pipes under different fatigue loading cycles, the damage and failure mechanisms of the concrete pipes under fatigue loading were revealed. The results indicate that the potential failure location of concrete pipes is within the inner crown of the bell under the fatigue traffic loads. The circumferential strains and crack propagation exhibiting a three-stage evolution pattern under fatigue loads. The proposed fatigue life prediction equation accurately predicts the remaining life of concrete pipes. Upon reaching 21.89 million loading cycles, the strain at the inner crown of the bell reaches 575.0 με, resulting in complete failure. Cracks on the inner crown of the bell extend inward and to the right from the middle of the joint, forming a channel for crack propagation. The vertical displacements at the crown and the circumferential bending moments of the bell and spigot exhibit rapid increases, stabilization, and subsequent declines with the increasing loading cycles. When concrete pipes undergo fatigue fracture, the maximum vertical displacement and circumferential bending moment at the bell are measured as 2.26 mm and 17.82 kN·m/m, respectively. Stress concentration at the bell and spigot during fatigue loading leads to crack propagation and convergence, causing redistribution of stress fields characterized by an initial increase followed by a decrease in the inner crown and invert of the bell.

Analysis and optimization design of internal pressure resistance of flexible composite pipe

Flexible composite pipes have the advantages of light weight, corrosion resistance, scale resistance, and low cost compared to carbon steel pipes, and have attracted much attention in the application of onshore oil and gas gathering and transportation systems. Understanding the relationship between the pressure-bearing mechanical properties of composite pipes and their structural characteristics is crucial for guiding their process application. To investigate the mechanical behavior of flexible composite pipes under internal pressure loads, discrete and combined finite element models were established to analyze the stress-strain characteristics of flexible composite pipes. The bursting strength was predicted, and the influence of winding angle and number of reinforcement layers on the pressure-bearing capacity of flexible composite pipes was revealed. The applicability of the two models in the analysis of internal pressure resistance of flexible composite pipes was evaluated using whole pipe strain testing and instantaneous hydrostatic burst experiments. The results showed that the reinforcement layer is the main pressure-bearing layer of flexible composite pipes, and the innermost reinforcement layer bears the highest pressure. The pressure-bearing capacity of flexible composite pipes significantly increases when the winding angle is greater than 53°, and the increase in pressure-bearing capacity slows down when the number of reinforcement layers exceeds 3. Under the combination model, the strain and bursting strength of flexible composite pipes were closer to the experimental results. The study clearly defines the stress-strain characteristics of flexible composite pipes under internal pressure load and the impact of process parameters, providing a basis for the optimization design of single well oil transmission pipelines in Xinjiang oilfield.

Analysis of Reinforced Concrete Pipe Strain Due to Jacking Force Case Study: Sudetan Ciliwung River Project to the East Flood Canal

Pipe Jacking is an innovation in trenchless technology that has been utilized in various sectors including municipal wastewater systems, oil and gas transportation, and hydraulic engineering. One of the critical aspects to ensure the success and safety of the pipe jacking process is strain monitoring. This study discussed the strain characteristics of reinforced concrete pipe structures during pipe jacking. The analysis was conducted using a numerical approach, which compared to field monitoring. Field strain monitoring was performed by strategically placing strain gauges along the pipe during the jacking operation, resulting in real-time data on deformation and pressure values. When the strain was monitored, the numerical test was conducted simultaneously using finite element analysis of Rocscience 3D. Those activities were done to consider the interaction between the reinforced concrete pipe and the surrounding soil. The strain analysis results indicated that the pipe responded during the pipe jacking process. The values of strain were various, depending on jacking force, condition of excavated soil layers, and distance between twin tunnels. The maximum stress occurred at the beginning of jacking process, when the pipe infiltrated into the soil with stress value of 512 kPa.

Static and dynamic responses of buried steel pipe under truck load: An experimental study

The behavior of a buried pipe under static and dynamic loading conditions has been investigated through full-scale field tests. A plain steel pipe with a diameter of 762 mm was gauged at the outer surface of two pipe sections. A dump truck was employed for the static and dynamic loading tests. Under static loading, the measured pipe strains increase with increasing axle load and decreasing cover depth. The measured strains under dynamic loading show three peaks, which correspond to the times at which the front, middle, and rear axles, respectively, reach the pipe centerline. The offset loading pattern produces greater strains than the non-offset one while keeping the axle load constant under both static and dynamic loads. It is discovered that the pipe strains caused by each truck axle vary with truck speed. Since the load transfer is influenced by a number of factors, including the truck load, road roughness, truck speed, and others, a moving truck load does not always result in higher pipe strains as compared to a static load. The complexity of dynamic pipe responses can be explained in part by a single-degree-of-freedom (SDOF) model.

Strain analysis of acrylic pipe under liquid storage pressure

Pipeline transportation is an important engineering component, which is widely used in transporting gas and liquid resources. The safety of the pipeline became the central point of this study. Pipeline deformation caused by liquid storage pressure is of great significance to the safety of pipeline engineering. Previous studies mainly focused on pipe deformation under ring force and less on deformation caused by internal liquid. In this paper, the theoretical results of strain distribution are derived based on elastic mechanics, and the strain distribution equation is established. The effects of the liquid storage pressure, pipe diameter, and pipe length on pipe strain are investigated experimentally. The experimental results are in agreement with the equation. It is found that the strain increases linearly with the increase in reservoir pressure. Under the same length, the larger the pipe diameter is, the larger the pipe strain is when the pipe diameter is 5–10 mm. In the range of 10–15 mm, the average strain is basically unchanged. Under the same pipe diameter, the pipe length has little effect on the average strain. The strain is greatest in the middle of the pipeline and decreases gradually to both sides. The results have important guiding significance for pipeline protection and stress corrosion prevention.

Seismic and dynamic response characteristics of flax fiber-reinforced epoxy pipes

Dynamic and seismic response characteristics of free-spanning above-ground flax fibre-reinforced epoxy (FFRE) pipes with various diameters of 38, 60, 100, 160, and 205 mm and different fabric layers of 2, 3, and 4 (thickness of 3.4 mm–6.65 mm), and a free span of 3870 mm were investigated experimentally and numerically. The FFRE pipes were subjected to harmonic ground motions with peak ground acceleration of 0.1g, 0.2g, and 0.3g, vibration frequency of 2, 4, and 6 HZ, and a duration of 40 s, and a record from the 2011 Christchurch earthquake when the pipe was empty, half-filled or completely-filled with water to establish the effect of peak ground acceleration, vibration frequency, pipe water content, diameter and thickness on pipe displacement, acceleration, strain, and internal pressure. FFRE pipes underwent larger displacements and strains and higher transverse accelerations when the pipe was completely-filled, while the pipe underwent higher vertical acceleration and higher internal pressure when the pipe was half-filled. The pipe strain increased by up to 719% by increasing the peak ground acceleration from 0.1g to 0.3g, up to 452% by increasing the vibration frequency from 2 to 6 Hz, and up to 1358% by increasing the pipe water content from empty to completely-filled. FFRE pipes remained below their material ultimate limits, and no service or structural failure in the form of seepage or excessive deformation was detected in the pipe body, indicating great potential for using FFRE pipes as an alternative option to conventional pipes at seismic zones.

Performance Analysis of Buried Natural Gas Pipeline under Uneven Settlement Action

This paper uses ABAQUS software, considering the nonlinear contact of pipe soil and buried soil material, and studies the simulation experiment of X100 steel pipe under uneven settlement conditions. The influence of settlement, internal pressure and wall thickness on the strain of steel pipe are discussed. The results show that compared with the internal pressure, the wall thickness has a greater impact on the deformation, the increased wall thickness can effectively reduce the maximum pressure strain, and the maximum pressure strain position will move to the axial direction. Deformation analysis and prevention of X100 steel pipe under uneven settlement conditions are very important, which will play a positive role in improving the safety and reliability of the pipeline and avoiding potential safety accidents.

Performance of buried pipeline under reverse fault in permafrost region

Long-distance pipelines may pass through areas of frozen soil sometimes, such as the Trans-Alaska pipeline and the Chinese Northeast pipeline. This work intends to analyze the performance of buried pipeline under reverse fault motion in such regions. A pipe-soil system model was established, and the thermo-mechanical coupling analysis was carried out. The temperature distribution of the soil near the ground and around the pipe is affected by them apparently, especially by ground. For the true temperature field (TTF) and the simplified one (STF), the pipe strain peak value and developing laws differ hugely, because of different soil mechanical properties distribution. The peak strains of the pipe are the largest at +0 °C of the ground, and the local buckling of the pipe appears earlier than the tensile failure. TTF should be obtained, and the peak compressive strain at +0 °C should be taken as the main criterion for seismic design or check calculation, for compressive bearing capacity usually determines pipe mechanical properties.

Mechanical response of concrete pipe rehabilitated by liner under external load: Analytical solution

AbstractUsing pipe lines to rehabilitate concrete drainage pipes is a popular trenchless technique. In this paper, the concrete pipe and liner are equivalent to a symmetrical structural mechanics problem, and the mechanical solution of the composite structure is obtained using the force method. Subsequently, the analytical solutions are compared with the test and finite element results. The distribution law of axial force, bending moment, and shear force of the composite structure are obtained, and the circumferential strain law of the inner and outer surfaces of the host pipe is analyzed. Lastly, the influence of pipe diameter and liner thickness on the bearing capacity of the host pipe is examined. The results indicate that the axial and shear force distribution of the composite structure remains the same for different pipe diameters, as the distribution diagrams of shear and axial force along the circumferential direction coincide. While the elastic modulus and thickness of the liner have no effect on the internal force distribution of the composite structure, they do directly affect the stress state of the host pipe. Additionally, the bottom support causes abrupt changes in the bending moments and strains of the host pipe.

ANALISA KEKERASAN MATERIAL HASIL ANNEALING PADA PIPA LONG ELBOW MATERIAL STAINLESS STEEL ASTM 304 L MENGGUNAKAN HARDNESS TESTER

Bending is a process of mixing materials which results in convexity while other parts become concave due to the influence of force or bending moment. During the bending process, it results in different pipe strains, which cause permanent strains. The annealing process (heat treatment) is a process for changing the metal structure by heating the specimen. The aim of this research is to analyze the material hardness of the ASTM 304 L stainless steel long elbow pipe after the annealing process is carried out, the test is carried out at various angles, namely (0°, 90°, 180°, and 270°) using the Hardness Tester. The method used in this research is an experimental method, a research procedure carried out to determine the effects of the annealing treatment given to the material. The research results from the 0° angle have a material hardness of 156 HB, from the 90° angle the material hardness is 140 HB, from the 1800 angle the material hardness is 164 HB, from the 2700 angle the material hardness is 159 HB, the conclusion is that the annealing process and the inner angle of the long elbow pipe has a significant influence on the hardness of stainless steel materials. Keywords: elbow pipe, annealing, hardness tester.

Centrifuge test of large-diameter segmented ductile iron pipes crossing strike-slip faults

Seismic ground faults are severe hazards for buried pipes. To explore and model the failure mechanisms of segmented pipes crossing faults, a centrifuge test of a socket-type ductile iron pipe crossing a strike-slip fault is conducted. In the test, a segmented ductile iron pipe with five segments is buried in a soil box. Then, at a centrifugal gravity level of 30.7 g, 60 mm ground displacements are applied through translation of half of the test soil box. Thus, a 2646.2 mm-diameter pipe with a length of 27.4 m subjected to a 1.84 m-long strike-slip fault is simulated. The responses of the joint deformation and the pipe strain are obtained. Results show that the joint deformation is the main response of the pipes subjected to strike-slip faults, the joint near the fault trace is vulnerable, the pipe strain is relatively small, and the peak pipe strain occurs at a certain distance from the fault. Lastly, a theoretical method is presented to obtain the joint deformation of the pipes crossing a strike-slip fault, and a good agreement between the test and theoretical results is observed. The test can be a benchmark for theoretical and numerical models. Meanwhile, the proposed theoretical method has clear physical mechanisms and can obtain the pipe joint deformation effectively.

An analytical solution for landslide impact on buried continuous pipelines

Transverse permanent ground deformation (PGD) induced by landslide can exert excessive soil restraints on buried pipelines and threaten the pipeline safety. However, there is a lack of effective analysis model to assess the landslide-pipeline interaction. In this work, an analytical solution for calculating the responses of an existing continuous pipeline affected by landslide is presented, in which the pipeline and the subgrade are modelled as a Timoshenko beam and Winkler foundations, respectively. The proposed approach is evaluated by well-documented results of model testing on laterally loaded pipes and finite element analyses on landslide-pipeline interaction. Subsequently, safety assessments of pipelines are parametrically studied with respect to the dimension of transverse PGD, pipe size, and relative rigidity factor. It is found that the pipe deflection and strain depend greatly on the width of PGD zone. Pipeline could appear local buckling for all power parameter (N) values, and tensile rupture appears in the pipe when N ≥ 2.2. The unsafe condition of the pipeline occurs when the maximum PGD is δ ≥ 1.1 m. For the safety pipe design, the pipe diameter is a key factor rather than the pipe wall thickness, and the relative rigidity factor should be controlled at a lower value.

Experimental study on the mechanical behavior of buried steel pipeline subjected to the local subsidence

Localized subsidence of soil layer is a typical geological disaster for buried long-distance oil and gas pipelines, which seriously threatens the safe operation of oil and gas pipelines. Therefore, a series of large-scale model tests are performed to investigate the mechanical response of the buried pipe induced by surrounding soil when the localized soil layer sinks. Results indicate that the subsidence height has a relatively greater impact on pipe strain and soil pressure than the subsidence range. Moreover, the distribution of the pipeline strain presents obvious regional characteristics and is divided into subsidence regions, non-subsidence affected regions, and non-subsidence unaffected regions. With the increasing moisture content of the backfill, the strain of the pipeline and the earth pressure around the pipe was reduced. In addition, the modified Marston earth pressure formula is proposed to estimate the vertical earth pressure on the top of the pipeline. The vertical earth pressure calculated using the proposed method fits well with the test results.

Determination of Blast Vibration Safety Criteria for Buried Polyethylene Pipelines Adjacent to Blast Areas, Using Vibration Velocity and Strain Data.

In order to ensure the safe operation of buried polyethylene pipelines adjacent to blasting excavations, controlling the effects of blasting vibration loads on the pipelines is a key concern. Model tests on buried polyethylene pipelines under blasting loads were designed and implemented, the vibration velocity and dynamic strain response of the pipelines were obtained using a TC-4850 blast vibrometer and a UT-3408 dynamic strain tester, and the distribution characteristics of blast vibration velocity and dynamic strain were analyzed based on the experimental data. The results show that the blast load has the greatest effect on the circumferential strain of the polyethylene pipe, and the dynamic strain response is greatest at the section of the pipe nearest to the blast source. Pipe peak vibration velocity (PPVV), ground peak particle velocity (GPPV), and the peak dynamic strain of the pipe were highly positively correlated, which verifies the feasibility of using GPPV to characterize pipeline vibration and strain level. According to the failure criteria and relevant codes, combined with the analysis of experimental results, the safety threshold of additional circumferential stress on the pipeline is 1.52 MPa, and the safety control vibration speed of the ground surface is 21.6 cm/s.

Machine learning‐based prediction of the seismic response of fault‐crossing natural gas pipelines

AbstractHerein, we utilized machine‐learning (ML) and data‐driven (regression) techniques to tackle a critical infrastructure engineering problem—namely, predicting the seismic response of natural gas pipelines crossing earthquake faults. Such a 3D nonlinear problem can take up to 10 h to solve by performing finite element analysis (FEA), considering the length of the pipeline and a large number of pipe and soil elements. However, the ML and data‐driven techniques can learn the projection rule of input‐output and predict the pipeline response instantaneously given a set of input features. In addition, the well‐trained ML model can be implemented for regional‐scale risk and rapid post‐event damage assessments. In this study, the input for ML comprised approximately 217K nonlinear FEAs, which covered a wide range of combinations of soil, structural and fault properties and yielded critical pipe strain responses under fault‐rupture displacements. We adopted various regression models and physics‐constrained neural networks, which can accurately and rapidly predict the tensile and compressive strains for a broad range of probable fault‐rupture displacements. Performances of various ML and conventional statistical models were systematically examined. Not surprisingly, neural networks exhibited the best performance for this multi‐output regression problem, in whichR2 > 0.95 was achieved for a wide range of fault displacement (FD) levels. Further, we used the trained neural network with 14.5 million Monte‐Carlo‐generated input samples to predict the maximum tensile and compressive strain curves of pipelines. This new dataset aimed at filling the missing input‐output points from the 217K FEAs, and improved the accuracy of the prediction of probability of failure for natural gas pipelines under FD hazards.

Strain assessment of polyethylene pipes in dense sand subjected to axial displacement

Buried polyethylene pipes used in gas distribution systems can experience excessive wall strain when exposed to ground movement that can affect the performance of the pipes in service. This paper presents full-scale laboratory tests performed to investigate the responses of medium-density polyethylene (MDPE) gas-distribution pipes in dense sand when subjected to axial ground movement. Pipes buried in sand in a large test box were pulled at the rates of 0.5 mm/min, 1 mm/min, and 2 mm/min to simulate relative ground movement in the longitudinal direction. The test facility was instrumented to measure pulling force, pipe wall strain, and soil stress. The measured pullout force was significantly higher than predicted using the equations recommended in current design guidelines, which is attributed to the increase of normal stress on the pipe wall by shear-induced dilation of interface soil. The cavity expansion theory was successfully applied to calculate the normal stress increase. The distribution of measured strains was nonlinear along the pipe length. Assuming a parabolic distribution of the strains, simplified equations were developed to calculate pullout resistance and pipe wall strain from the relative ground displacement. The developed method reasonably predicted the pipe strain measured during the tests.

Response of UPVC pipes buried in sand under lateral ground movement

As a key part of global lifeline infrastructure, buried pipelines play a vital role in transporting products for the daily life of human beings. However, the ultimate soil resistance and yield displacement are only derived for rigid pipes in current design guidelines, which are difficult to guide the analysis of flexible pipes. This investigation presents large-scale laboratory tests on flexible UPVC pipes subjected to lateral ground movements. The soil failure mechanism and pipe deformation were tracked. The reaction developing on UPVC pipe was measured as a function of pipe lateral displacement, embedment depth, sand bed density and pipe wall thickness. Analysis results reveal that the failure mode of soil changed from the general shear failure to the local shear failure, in which the soil arching effect occurred in both the active and passive loading areas, as the embedment ratio increased. Current design approaches could overestimate or underestimate the ultimate soil resistance of UPVC pipe heavily under various conditions, while the measured yield displacement was 2 to 3 times the prediction from the design guidelines. Finally, a simplified design method was proposed based on the pipe yield displacement for predicting the maximum longitudinal strain of UPVC pipes under lateral loading.

The ratcheting effect on the SS316L U-shaped pipe under internal pressure and bending cycle

The ratcheting behavior refers to the progressive accumulation of strains resulting from the cyclic loading applied to the specimens. Nowadays, much attention has been devoted to ratcheting pipelines. Hence, the ratcheting behavior of the SS316L U-shaped pipe subjected to internal pressure and cyclic bending force is investigated here. The experiments use the Servo-hydraulic device of Zwick/Roell Amsler HB 100. The local strains at the internal, external, and lateral bending points are specified using the pipe strain gauges. Then, the effect of the internal pressure, average force, and force amplitude on the ratcheting strains are examined and compared. The numerical simulation also employs the Abaqus software and the isotropic/kinematic nonlinear hardening model. It was revealed that ratcheting strain in the axial direction is more critical than in the pipe's peripheral direction. The effect of amplitude and average pressure on thin-wall the ratcheting behavior of thin-wall pipe in the axial direction during four thousand cycles are investigated. According to the observed results, increasing amplitude and average bending force while the internal pressure is constant increases the ratcheting strain. Besides, the variation of the force amplitude affects the ratcheting strain more significantly than the variation of the average force. In order to validate the obtained results, a careful comparison was made between the numerical and experimental results, and a good agreement was observed between them. Notably, the novelty of this study lies in the comprehensive analysis of the ratcheting behavior of the SS316L U-shaped pipe conducted here.