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centrifuge model test on performance of thermosyphon cooled sandbags stabilizing warm oil pipeline buried in permafrost

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Research in Cold and Arid Regions 2021年第3期13卷 234-255页

作者： GuoYu Li HongYuan Jing Nikolay Volkov Wei Ma PengChao Chen State Key Laboratory of Frozen Soil Engineering(SKLFSE) Northwest Institute of Eco-Environment and Resources(NIEER)Chinese Academy of Sciences(CAS)LanzhouGansu 730000China Da Xing'anling Observation and Research Station of Frozen-ground Engineering and Environment NIEERCASJiagedaqiHeilongjiang 165000China PipeChina North Pipeline Company LangfangHebei 065000China GEOINGSERVICE LLP(Fugro Group) 29 Vernadskogo AvenueMoscowRussia

The thaw settlement of pipeline foundation soils in response to the operation of the first China-Russia Crude Oil Pipeline along the eastern flank of the northern Da Xing'anling Mountains in Northeast China was simulated in a physical model test(with a similitude ratio of 1/73) in a geotechnical centrifuge. Two pipes of a supported and an unsupported section were evaluated over a testing period for simulating 20 years of actual pipeline operation with seasonal cyclically changing oil and ambient temperatures. The results show that pipe settlement of the supported pipe was 45% of settlement of the unsupported pipe. Settlement for the unsupported section was approximately 35% of the thaw bulb depth below the initial pipe elevation, only 30% of that for the supported pipe due to the influence of the supports. The final thaw bulbs extended approximately 3.6 and 1.6 times of the pipe diameter below the unsupported and supported pipe bottom elevations, respectively. The sandbag supports kept frozen during the test period because of cooling effect of the thermosyphons. The maximum bending stress induced over the 20 m span length from bearing of the full cover over the pipe would be equivalent to40% specified minimum yield strength(SMYS). Potential buckling of the pipe should be considered as the ground *** study also offers important data for calibration and validation of numerical simulation models.

关键词： centrifuge test oil pipeline frost heave thermosyphon thaw settlement permafrost engineering

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Experimental p-y curves for liquefied soils from centrifuge tests

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Earthquake Engineering and Engineering Vibration 2021年第4期20卷 863-876页

作者： Suresh R.Dash Subhamoy Bhattacharya School of Infrastructure Indian Institute of Technology BhubaneswarIndia Department of Civil and Environmental Engineering University of SurreyUK

The present study aims to obtain p-y curves(Winkler spring properties for lateral pile-soil interaction)for liquefied soil from 12 comprehensive centrifuge test cases where pile groups were embedded in liquefiable *** p-y curve for fully liquefied soil is back-calculated from the dynamic centrifuge test data using a numerical procedure from the recorded soil response and strain records from the instrumented *** p-y curves were obtained for two ground conditions:(a)lateral spreading of liquefied soil,and(b)liquefied soil in level *** ground conditions are simulated in the model by having collapsing and non-collapsing intermittent boundaries,which are modelled as quay *** p-y curves back-calculated from the centrifuge tests are compared with representative reduced API p-y curves for liquefied soils(known as p-multiplier).The response of p-y curves at full liquefaction is presented and critical observations of lateral pile-soil interaction are *** on the results of these model tests,guidance for the construction of p-y curves for use in engineering practice is also provided.

关键词： liquefaction pile foundation p-y curve centrifuge test

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centrifuge modelling of ground-borne vibrations induced by railway traffic in underground tunnels

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Earthquake Engineering and Engineering Vibration 2022年第2期21卷 517-528页

作者： Yang Wenbo Qian Zhihao Tu Jiulin Zhou Ziyang Yan Qixiang Fang Yong He Chuan Key Laboratory of Transportation Tunnel Engineering the Ministry of EducationSouthwest Jiaotong UniversityChengdu 610031China

Increased attention has been given to ground-borne vibrations induced by railway vehicles and to the effects of these vibrations as they propagate through the ground into nearby *** studies,mainly based on numerical methods as well as physical modelling,have been carried out to investigate this *** study the dynamic response of tunnels and the surrounding soil due to train-induced vibration loads,a centrifuge test was conducted with a small-scale model in 1 g and 50 g stress field *** aluminum tube was embedded in sand to model the underground tunnel.A small parallel pre-stressed actuator(PPA)was employed to apply vibration loads on the tunnel *** model responses were measured using *** time and frequency domain analyzes were *** test results demonstrated that electronic noise had a clear impact on the test results and should be *** also found that the dynamic response of both the tunnel and soil were affected by the stress ***,it is important to account for the stress field effects when assessing the ground-borne vibration from tunnels.

关键词： centrifuge test stress field frequency response function peak particle acceleration dynamic response

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Influence of erosion voids and traffic loads on buried large-diameter reinforced concrete pipes

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Underground Space 2024年第4期17卷 120-131页

作者： Ming Xu Dawei Shen Department of Civil Engineering Tsinghua UniversityBeijing 100084China Beijing Institute of Technology Beijing 100081China

Geotechnical centrifuge tests were conducted to examine the influence of invert voids and surface traffic loads on 1400 mm diameter reinforced concrete pipes buried with a shallow soil cover depth of 700 *** formation beneath the pipe was simulated during centrifuge *** test results revealed that before void formation,the surface load directly above the middle of the pipe caused a significant increase in not only the circumferential bending moments but also the longitudinal bending moments,the latter of which was considerable and could not be *** formation beneath the middle of the pipe led to a reduction in both the circumferential bending moments and longitudinal bending moments at all measuring positions,i.e.,crown,springline,and *** most significant reduction occurred at the invert,and there was even a reversal in the sign of the invert longitudinal bending moment.A comparison was made between centrifuge tests with erosion voids and surface loads at different horizontal positions,which had a marked influence even when the positions differed by half a pipe *** rotation played an important role in relieving large bending moments of pipe barrels in a jointed pipeline when the void and surface load were located at the joint.

关键词： centrifuge test Erosion void Reinforced concrete pipe Traffic loading Longitudinal bending moment Joint rotation

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Comparisons between centrifuge and numerical modeling results for slope toppling failure

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Science China(Technological Sciences) 2015年第9期58卷 1497-1508页

作者： CHEN ZuYu GONG WenJun MA GuoWei WANG Jie HE Lei XING YiChuan XING JianYing School of Transportation Science and Engineering Beihang University Department of Geotechnical Engineering China Institute of Water Resources and Hydropower School of Civil and Resource Engineering University of Western Australia Institute of Mechanics Chinese Academy of Sciences Department of Civil Engineering Monash University Yellow River Engineering Consulting Co. Ltd.

This paper presents series studies on the toppling mechanism by centrifuge tests and numerical simulations. Two different discrete element methods, i.e., the continuum-based discrete element method(CDEM) and the discontinuous deformation analysis(DDA), are adopted. The modeling results show that both the methods can accurately capture the failure modes of the centrifuge tests, including three distinct zones and two failure surfaces. Comparisons are made between the physical test and numerical simulation results. The critical inclination angle of the tilting table where the slope models are fixed on can be moderately predicted by the two methods, with different degrees of precision. The error between the test results and the simulated results is within 1% for the slope models without rock-bridges by both CDEM and DDA. However, it is amplified for the staggered-joint models that simulate the rock-bridges. With DDA, the average error is about 5%, and the maximum error is up to 17%. While with CDEM, the errors for the aligned-joint models are ranged from 1% to 6%, and it is from 10% to 29% for the staggered-joint models. The two numerical methods show the capability in simulating toppling failure of blocky rock mass with and without rock-bridges. The model with rock-bridges which provides a certain bending resistance is more stable than the one without any rock-bridge. In addition, the two failure surfaces were observed, which is different from the common understanding that only one failure surface appears.

关键词： rock slope model toppling failure rock-bridge centrifuge test continuum based discrete element method discontinuous deformation analysis

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Numerical Analysis and centrifuge Modeling of Shallow Foundations

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China Ocean Engineering 2014年第2期28卷 163-180页

作者：罗强栾茂田杨蕴明王忠涛赵守正 Institute of Geotechnical Engineering School of Civil EngineeringDalian University of Technology Academy of Civil Engineering and Architecture Nanyang Normal University State Key Laboratory of Geomechanics and Geotechnical Engineering Institute of Rock and Soil MechanicsChinese Academy of Sciences

The influence of non-coaxial constitutive model on predictions of dense sand behavior is investigated in this paper. The non-coaxial model with strain softening plasticity is applied into finite-element program ABAQUS, which is first used to predict the stress-strain behavior and the non-coaxial characteristic between the orientations of the principal stress and principal plastic strain rate in simple shear tests. The model is also used to predict load settlement responses and bearing capacity factors of shallow foundations. A series of centrifuge tests for shallow foundations on saturated dense sand are performed under drained conditions and the test results are compared with the corresponding numerical results. Various footing dimensions, depths of embedment, and footing shapes are considered in these tests. In view of the load settlement relationships, the stiffness of the load-displacement curves is significantly affected by the non-coaxial model compared with those predicted by the coaxial model, and a lower value of non-coaxial modulus gives a softer response. Considering the soil behavior at failure, the coaxial model predictions of bearing capacity factors are more advanced than those of centrifuge test results and the non-coaxial model results;besides, the non-coaxial model gives better predictions. The non-coaxial model predictions are closer to those of the centrifuge results when a proper non-coaxial plastic modulus is chosen.

关键词： non-coaxial model strain softening FEM analysis centrifuge test shallow foundation

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centrifuge study on behavior of raft foundation after tunnelling in soft clay

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Underground Space 2024年第4期17卷 161-169页

作者： Jian Yu Jiaming Liu Chun Fai Leung Maosong Huang Qi Wen Jorgin Tan Department of Geotechnical Engineering Key Laboratory of Geotechnical and Underground Engineering of Ministry of EducationTongji UniversityShanghai 200092China Centre for Offshore Research and Engineering Department of Civil and Environmental EngineeringNational University of Singapore119077Singapore Land Transport Authority 219428Singapore

Ground losses due to tunneling would induce settlement of nearby raft *** study the change in behavior of the raft foundations over time due to tunnel excavation in soft clay,a series of centrifuge model tests were *** results reveal that the raft stiffness has a significant influence on the development of the gap between the raft and the *** width of the gap beneath the flexible foundation would increase over time,leading to a further increase in tensile strain after excavation,whereas the gap for raft foundations with a large stiffness would reduce with time,causing a gradual decrease in tensile *** modification factor(MF)design approach is also evaluated with the test results and demonstrates that the MF design approach would underestimate the tensile strain of the flexible raft and provide a relatively conservative prediction for larger stiffnesses.

关键词： Tunnelling Raft Clay Deflection ratio centrifuge test

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Numerical modeling of centrifuge cyclic lateral pile load experiments

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Earthquake Engineering and Engineering Vibration 2009年第1期8卷 61-76页

作者： Nikos Gerolymos Sandra Escoffier George Gazetas Jacques Garnier Civil Engineering National Technical UniversityAthens Greece Laboratoire Central des Ponts et Chaussées Nantes France Lecturer Laboratoire Central des Ponts et Chaussées Nantes France

To gain insight into the inelastic behavior of piles, the response of a vertical pile embedded in dry sand and subjected to cyclic lateral loading was studied experimentally in centrifuge tests conducted in Laboratoire Central des Ponts et Chaussees. Three types of cyclic loading were applied, two asymmetric and one symmetric with respect to the unloaded pile. An approximately square-root variation of soil stiffness with depth was obtained from indirect in-flight density measurements, laboratory tests on reconstituted samples, and well-established empirical correlations. The tests were simulated using a cyclic nonlinear Winkler spring model, which describes the full range of inelastic phenomena, including separation and re-attachment of the pile from and to the soil. The model consists of three mathematical expressions capable of reproducing a wide variety of monotonic and cyclic experimentalp-y curves. The physical meaning of key model parameters is graphically explained and related to soil behavior. Comparisons with the centrifuge test results demonstrate the general validity of the model and its ability to capture several features of pile-soil interaction, including： soil plastification at an early stage of loading, ＂pinching＂ behavior due to the formation of a relaxation zone around the upper part of the pile, and stiffness and strength changes due to cyclic loading. A comparison of the p-y curves derived from the test results and the proposed model, as well as those from the classical curves of Reese et al. （1974） for sand, is also presented.

关键词： centrifuge test Winkler model p-y curves cyclic loading pile-soil separation/gapping nonlinear response experimental validation

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centrifuge modelling of landslides and landslide hazard mitigation:A review

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Geoscience Frontiers 2023年第1期14卷 372-401页

作者： Kun Fang Huiming Tang Changdong Li Xuexue Su Pengju An Sixuan Sun Faculty of Engineering China University of GeosciencesWuhan 430074China Badong National Observation and Research Station of Geohazards China University of GeosciencesWuhan 430074China

Landslides are serious geohazards that occur under a variety of climatic conditions and can cause many casualties and significant economic *** modelling,as a representative type of physical modelling,provides a realistic simulation of the stress level in a small-scale model and has been applied over the last 50 years to develop a better understanding of *** recent developments in this technology,the application of centrifuge modelling in landslide science has significantly ***,we present an overview of physical models that can capture landslide processes during centrifuge *** review focuses on(i)the experimental principles and considerations,(ii)landslide models subjected to various triggering factors,including centrifugal acceleration,rainfall,earthquakes,water level changes,thawing permafrost,excavation,external loading and miscellaneous conditions,and(iii)different methods for mitigating landslides modelled in centrifuge,such as the application of nails,piles,geotextiles,vegetation,*** behaviors of all the centrifuge models are discussed,with emphasis on the deformation and failure mechanisms and experimental *** on this review,we provide a best-practice methodology for preparing a centrifuge landslide test and propose further efforts in terms of the seven aspects of model materials,testing design and equipment,measurement methods,scaling laws,full-scale test applications,landslide early warning,and 3D modelling to better understand the complex behaviour of landslides.

关键词： centrifuge test Landslide Slope stability Scaling law Mitigation strategy

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Application of Geotextile Bag Dehydrated Soil to Dike Construction

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Transactions of Tianjin University 2004年第4期10卷 297-303页

作者：朱平闫澍旺刘润 Geotechnical Research Institute Tianjin University Tianjin 300072 China

Using geotextile bag dehydrated soil to construct dikes for land reclamation to substitute conventional straw bags is an urgent need in Tianjin New Harbor, China. This paper introduces the method to build a dike for hydraulic filling. The soil for filling the geotextile bags was tested in wave trench; the stress developed during construction was calculated by establishing a numerical model and compared with the tensile strength of the geotextile; the stability and settlement of the dike were estimated by performing centrifuge tests. Through this study, the following information was obtained: 1) The cohesionless silt with plasticity index less than 10 is suitable for filling the geotextile bags. The geotextile bag dehydrated soil consolidated very quickly even under the action of wave force. 2) A numerical model was devised to find the limit injection height and to calculate the tensile stress developed in the geotextile bags when they were piled up to form the dike. The calculated stress was compared with the strength of the geotextile, showing that the design is reasonably safe. 3) centrifuge test results show that the designed dike will be stable and the settlement of dike will be less than the design requirement.

关键词： geotextile bag dehydrated soil silt dike reclamation centrifuge test

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