Cyclic loads generated by environmental factors,such as winds,waves,and trains,will likely lead to performance degradation in pile foundations,resulting in issues like permanent displacement accumulation and bearing c...Cyclic loads generated by environmental factors,such as winds,waves,and trains,will likely lead to performance degradation in pile foundations,resulting in issues like permanent displacement accumulation and bearing capacity attenuation.This paper presents a semi-analytical solution for predicting the axial cyclic behavior of piles in sands.The solution relies on two enhanced nonlinear load-transfer models considering stress-strain hysteresis and cyclic degradation in the pile-soil interaction.Model parameters are calibrated through cyclic shear tests of the sand-steel interface and laboratory geotechnical testing of sands.A novel aspect involves the meticulous formulation of the shaft loadtransfer function using an interface constitutive model,which inherently inherits the interface model’s advantages,such as capturing hysteresis,hardening,degradation,and particle breakage.The semi-analytical solution is computed numerically using the matrix displacement method,and the calculated values are validated through model tests performed on non-displacement and displacement piles in sands.The results demonstrate that the predicted values show excellent agreement with the measured values for both the static and cyclic responses of piles in sands.The displacement pile response,including factors such as bearing capacity,mobilized shaft resistance,and convergence rate of permanent settlement,exhibit improvements compared to non-displacement piles attributed to the soil squeezing effect.This methodology presents an innovative analytical framework,allowing for integrating cyclic interface models into the theoretical investigation of pile responses.展开更多
This paper investigates the interface mechanical behavior of flexible piles with L_p/D>10 under lateral load and an overturning moment in monotonic loading conditions.To modify the beam-on-Winkler-foundation model ...This paper investigates the interface mechanical behavior of flexible piles with L_p/D>10 under lateral load and an overturning moment in monotonic loading conditions.To modify the beam-on-Winkler-foundation model of piles in offshore wind farms,the energy-based variational method is used.The soil is treated as a multi-layered elastic continuum with the assumption of three-dimensional displacements,the pile modeled as an Euler-Bernoulli beam.A series of cases using MATLAB programming was conducted to investigate the simplified equations of initial stiffness.The results indicated that the interaction between soil layers and the applied force position should be taken into account in calculating the horizontal soil resistance.Additionally,the distributed moment had a limiting effect on the lateral capacity of a flexible pile.Moreover,to account for the more realistic conditions of OWT systems,field data from the Donghai Bridge offshore wind farm were used.展开更多
Anti-slide piles are one of the most important reinforcement structures against landslides,and evalu-ating the working conditions is of great significance for landslide mitigation.The widely adopted analytical methods...Anti-slide piles are one of the most important reinforcement structures against landslides,and evalu-ating the working conditions is of great significance for landslide mitigation.The widely adopted analytical methods of pile internal forces include cantilever beam method and elastic foundation beam method.However,due to many assumptions involved in calculation,the analytical models cannot be fully applicable to complex site situations,e.g.landslides with multi-sliding surfaces and pile-soil interface separation as discussed herein.In view of this,the combination of distributed fiber optic sensing(DFOS)and strain-internal force conversion methods was proposed to evaluate the working conditions of an anti-sliding pile in a typical retrogressive landslide in the Three Gorges reservoir area,China.Brillouin optical time domain reflectometry(BOTDR)was utilized to monitor the strain distri-bution along the pile.Next,by analyzing the relative deformation between the pile and its adjacent inclinometer,the pile-soil interface separation was profiled.Finally,the internal forces of the anti-slide pile were derived based on the strain-internal force conversion method.According to the ratio of calculated internal forces to the design values,the working conditions of the anti-slide pile could be evaluated.The results demonstrated that the proposed method could reveal the deformation pattern of the anti-slide pile system,and can quantitatively evaluate its working conditions.展开更多
Defects in cast-in-situ piles have an adverse impact on load transfer at the pile‒soil interface and pile bearing capacity. In recent years, thermal integrity profiling (TIP) has been developed to measure temperature ...Defects in cast-in-situ piles have an adverse impact on load transfer at the pile‒soil interface and pile bearing capacity. In recent years, thermal integrity profiling (TIP) has been developed to measure temperature profiles of cast-in-situ piles, enabling the detection of structural defects or anomalies at the early stage of construction. However, using this integrity testing method to evaluate potential defects in cast-in-situ piles requires a comprehensive understanding of the mechanism of hydration heat transfer from piles to surrounding soils. In this study, small-scale model tests were conducted in laboratory to investigate the performance of TIP in detecting pile integrity. Fiber-optic distributed temperature sensing (DTS) technology was used to monitor detailed temperature variations along model piles in sand. Additionally, sensors were installed in sand to measure water content and matric suction. An interpretation method against available DTS-based thermal profiles was proposed to reveal the potential defective regions. It shows that the temperature difference between normal and defective piles is more obvious in wet sand. In addition, there is a critical zone of water migration in sand due to the water absorption behavior of cement and temperature transfer-induced water migration in the early-age concrete setting. These findings could provide important insight into the improvement of the TIP testing method for field applications.展开更多
The interface mechanical behavior of a monopile is an important component of the overall offshore wind turbine structure design.Understanding the soil-structure interaction,particularly the initial soil-structure stif...The interface mechanical behavior of a monopile is an important component of the overall offshore wind turbine structure design.Understanding the soil-structure interaction,particularly the initial soil-structure stiffness,has a significant impact on the study of natural frequency and dynamic response of the monopile.In this paper,a simplified method for estimating the interface mechanical behavior of monopiles under initial lateral loads is proposed.Depending on the principle of minimum potential energy and virtual work theory,the functions of soil reaction components at the interface of monopiles are derived;MATLAB programming has been used to simplify the functions of the initial stiffness by fitting a large number of examples;then the functions are validated against the field test data and FDM results.This method can modify the modulus of the subgrade reaction in the p-y curve method for the monopile-supported offshore wind turbine system.展开更多
The resilient modulus,accumulated plastic strain,peak shear stress,and critical shear stress are the elastoplastic behaviors of frozen sand–concrete interfaces under cyclic shear loading.They reflect the bearing capa...The resilient modulus,accumulated plastic strain,peak shear stress,and critical shear stress are the elastoplastic behaviors of frozen sand–concrete interfaces under cyclic shear loading.They reflect the bearing capacity of buildings(e.g.highspeed railways)in both seasonal frozen and permafrost regions.This study describes a series of direct shear experiments conducted on frozen sand–concrete interfaces.The results indicated that the elastoplastic behaviors of frozen sand–concrete interfaces,including the resilient modulus,accumulated plastic strain,and shear strength,are influenced by the boundary conditions(constant normal loading and constant normal height),initial normal stress,negative temperature,and cyclic-loading amplitude.The resilient modulus was significantly correlated with the initial normal stress and negative temperature,but not with the cyclic-loading amplitude and loading cycles.The accumulated plastic shear strain increased when the initial normal stress and cyclic-loading amplitude increased and the temperature decreased.Moreover,the accumulated plastic shear strain increment decreased when the loading cycles increased.The accumulated direction also varied with changes in the initial normal stress,negative temperature,and cyclic-loading amplitude.The peak shear stress of the frozen sand–concrete interface was affected by the initial normal stress,negative temperature,cyclic-loading amplitude,and boundary conditions.Nevertheless,a correlation was observed between the critical shear stress and the initial normal stress and boundary conditions.The peak shear stress was higher,and the critical shear stress was lower under the constant normal height boundary condition.Based on the results,it appears that the properties of frozen sand–concrete interfaces,including plastic deformation properties and stress strength properties,are influenced by cyclic shear stress.These results provide valuable information for the investigation of constitutive models of frozen soil–structure interfaces.展开更多
The effects of stabilizing piles on the stability of an embankment slope are analyzed by numerical simulation. The shear strength reduction method is used for the analysis, and the soil - pile interaction is simulated...The effects of stabilizing piles on the stability of an embankment slope are analyzed by numerical simulation. The shear strength reduction method is used for the analysis, and the soil - pile interaction is simulated with zero-thickness elasto-plastic interface elements. Effects of pile spacing and pile position on the safety factor of slope and the behavior of piles under these conditions are given. The numerical analysis indicates that the positions of the pile have significant influence on the stability of the slope, and the pile needs to be installed in the middle of the slope for maximum safety factors. In the end, the soil arching effect closely associated with the space between stabilizing piles is analyzed. The results are helpful for design and construction of stabilizing piles.展开更多
基金the financial support provided by the National Natural Science Foundation of China(Grant No.42272310).
文摘Cyclic loads generated by environmental factors,such as winds,waves,and trains,will likely lead to performance degradation in pile foundations,resulting in issues like permanent displacement accumulation and bearing capacity attenuation.This paper presents a semi-analytical solution for predicting the axial cyclic behavior of piles in sands.The solution relies on two enhanced nonlinear load-transfer models considering stress-strain hysteresis and cyclic degradation in the pile-soil interaction.Model parameters are calibrated through cyclic shear tests of the sand-steel interface and laboratory geotechnical testing of sands.A novel aspect involves the meticulous formulation of the shaft loadtransfer function using an interface constitutive model,which inherently inherits the interface model’s advantages,such as capturing hysteresis,hardening,degradation,and particle breakage.The semi-analytical solution is computed numerically using the matrix displacement method,and the calculated values are validated through model tests performed on non-displacement and displacement piles in sands.The results demonstrate that the predicted values show excellent agreement with the measured values for both the static and cyclic responses of piles in sands.The displacement pile response,including factors such as bearing capacity,mobilized shaft resistance,and convergence rate of permanent settlement,exhibit improvements compared to non-displacement piles attributed to the soil squeezing effect.This methodology presents an innovative analytical framework,allowing for integrating cyclic interface models into the theoretical investigation of pile responses.
基金financially supported by the National Natural Science Foundation of China (Grant Nos.52201324,52078128,and 52278355)the Natural Science Foundation of the Jiangsu Higher Education Institution of China (Grant No.22KJB560015)。
文摘This paper investigates the interface mechanical behavior of flexible piles with L_p/D>10 under lateral load and an overturning moment in monotonic loading conditions.To modify the beam-on-Winkler-foundation model of piles in offshore wind farms,the energy-based variational method is used.The soil is treated as a multi-layered elastic continuum with the assumption of three-dimensional displacements,the pile modeled as an Euler-Bernoulli beam.A series of cases using MATLAB programming was conducted to investigate the simplified equations of initial stiffness.The results indicated that the interaction between soil layers and the applied force position should be taken into account in calculating the horizontal soil resistance.Additionally,the distributed moment had a limiting effect on the lateral capacity of a flexible pile.Moreover,to account for the more realistic conditions of OWT systems,field data from the Donghai Bridge offshore wind farm were used.
基金The authors gratefully acknowledge the financial support pro-vided by the Young Scientists Fund of the National Natural Science Foundation of China(Grant No.41907232)the National Science Fund for Distinguished Young Scholars of China(Grant No.42225702)the State Key Program of National Natural Science Foundation of China(Grant No.41230636).
文摘Anti-slide piles are one of the most important reinforcement structures against landslides,and evalu-ating the working conditions is of great significance for landslide mitigation.The widely adopted analytical methods of pile internal forces include cantilever beam method and elastic foundation beam method.However,due to many assumptions involved in calculation,the analytical models cannot be fully applicable to complex site situations,e.g.landslides with multi-sliding surfaces and pile-soil interface separation as discussed herein.In view of this,the combination of distributed fiber optic sensing(DFOS)and strain-internal force conversion methods was proposed to evaluate the working conditions of an anti-sliding pile in a typical retrogressive landslide in the Three Gorges reservoir area,China.Brillouin optical time domain reflectometry(BOTDR)was utilized to monitor the strain distri-bution along the pile.Next,by analyzing the relative deformation between the pile and its adjacent inclinometer,the pile-soil interface separation was profiled.Finally,the internal forces of the anti-slide pile were derived based on the strain-internal force conversion method.According to the ratio of calculated internal forces to the design values,the working conditions of the anti-slide pile could be evaluated.The results demonstrated that the proposed method could reveal the deformation pattern of the anti-slide pile system,and can quantitatively evaluate its working conditions.
基金The authors grate fully acknowledge the financial support provided by the National Natural Science Foundation of China(Grant Nos.42225702 and 42077235)the Open Research Project Program of the State Key Laboratory of Internet of Things for Smart City(University of Macao),China(Grant No.SKUoTSC(UM)-2021-2023/0RP/GA10/2022).
文摘Defects in cast-in-situ piles have an adverse impact on load transfer at the pile‒soil interface and pile bearing capacity. In recent years, thermal integrity profiling (TIP) has been developed to measure temperature profiles of cast-in-situ piles, enabling the detection of structural defects or anomalies at the early stage of construction. However, using this integrity testing method to evaluate potential defects in cast-in-situ piles requires a comprehensive understanding of the mechanism of hydration heat transfer from piles to surrounding soils. In this study, small-scale model tests were conducted in laboratory to investigate the performance of TIP in detecting pile integrity. Fiber-optic distributed temperature sensing (DTS) technology was used to monitor detailed temperature variations along model piles in sand. Additionally, sensors were installed in sand to measure water content and matric suction. An interpretation method against available DTS-based thermal profiles was proposed to reveal the potential defective regions. It shows that the temperature difference between normal and defective piles is more obvious in wet sand. In addition, there is a critical zone of water migration in sand due to the water absorption behavior of cement and temperature transfer-induced water migration in the early-age concrete setting. These findings could provide important insight into the improvement of the TIP testing method for field applications.
基金financially supported by the National Natural Science Foundation of China(Grant Nos.52201324,52078128,and52278355)the Natural Science Foundation of the Jiangsu Higher Education Institution of China(Grant No.22KJB560015)the Postgraduate Research&Practice Innovation Program of Jiangsu Province(Grant No.SJCX21_1794)。
文摘The interface mechanical behavior of a monopile is an important component of the overall offshore wind turbine structure design.Understanding the soil-structure interaction,particularly the initial soil-structure stiffness,has a significant impact on the study of natural frequency and dynamic response of the monopile.In this paper,a simplified method for estimating the interface mechanical behavior of monopiles under initial lateral loads is proposed.Depending on the principle of minimum potential energy and virtual work theory,the functions of soil reaction components at the interface of monopiles are derived;MATLAB programming has been used to simplify the functions of the initial stiffness by fitting a large number of examples;then the functions are validated against the field test data and FDM results.This method can modify the modulus of the subgrade reaction in the p-y curve method for the monopile-supported offshore wind turbine system.
基金supported by the National Natural Science Foundation of China(No.41731281)the Key Foundation of Guangdong Province(No.2020B1515120083),China。
文摘The resilient modulus,accumulated plastic strain,peak shear stress,and critical shear stress are the elastoplastic behaviors of frozen sand–concrete interfaces under cyclic shear loading.They reflect the bearing capacity of buildings(e.g.highspeed railways)in both seasonal frozen and permafrost regions.This study describes a series of direct shear experiments conducted on frozen sand–concrete interfaces.The results indicated that the elastoplastic behaviors of frozen sand–concrete interfaces,including the resilient modulus,accumulated plastic strain,and shear strength,are influenced by the boundary conditions(constant normal loading and constant normal height),initial normal stress,negative temperature,and cyclic-loading amplitude.The resilient modulus was significantly correlated with the initial normal stress and negative temperature,but not with the cyclic-loading amplitude and loading cycles.The accumulated plastic shear strain increased when the initial normal stress and cyclic-loading amplitude increased and the temperature decreased.Moreover,the accumulated plastic shear strain increment decreased when the loading cycles increased.The accumulated direction also varied with changes in the initial normal stress,negative temperature,and cyclic-loading amplitude.The peak shear stress of the frozen sand–concrete interface was affected by the initial normal stress,negative temperature,cyclic-loading amplitude,and boundary conditions.Nevertheless,a correlation was observed between the critical shear stress and the initial normal stress and boundary conditions.The peak shear stress was higher,and the critical shear stress was lower under the constant normal height boundary condition.Based on the results,it appears that the properties of frozen sand–concrete interfaces,including plastic deformation properties and stress strength properties,are influenced by cyclic shear stress.These results provide valuable information for the investigation of constitutive models of frozen soil–structure interfaces.
基金Supported by Young Teacher Foundation of Tianjin University(No.5110104)
文摘The effects of stabilizing piles on the stability of an embankment slope are analyzed by numerical simulation. The shear strength reduction method is used for the analysis, and the soil - pile interaction is simulated with zero-thickness elasto-plastic interface elements. Effects of pile spacing and pile position on the safety factor of slope and the behavior of piles under these conditions are given. The numerical analysis indicates that the positions of the pile have significant influence on the stability of the slope, and the pile needs to be installed in the middle of the slope for maximum safety factors. In the end, the soil arching effect closely associated with the space between stabilizing piles is analyzed. The results are helpful for design and construction of stabilizing piles.