Double-row pile(DRP)retaining systems have been widely used in deep excavations in China.Soil between the front and back-row piles(FBP soil)is often improved to decrease the displacement of DRPs in soft soil areas,but...Double-row pile(DRP)retaining systems have been widely used in deep excavations in China.Soil between the front and back-row piles(FBP soil)is often improved to decrease the displacement of DRPs in soft soil areas,but the improvement efficiency has rarely been researched.A large and deep excavation supported by a DRP retaining system is introduced,and the effect of FBP soil improvement is discussed by comparing the finite element analysis and the monitoring results.Then,a parametric study of DRP using the finite element method considering the small strain of soil is conducted to investigate the effect of FBP soil improvement.It was shown that the pile deflection and bending moment decrease when the FBP soil is improved.Moreover,the most efficient way to minimize the pile deflection and bending moment is to improve the FBP soil around the excavation level.The FBP soil improvement 2-4 m below the pile head is not very useful for reducing the pile deflection and can be eliminated when the pile displacement limit is not very strict.展开更多
Understanding the factors triggering slope failure is essential to ensure the safety of buildings and transportation infrastructure on slopes. Specifically,the failure of stabilizing piles due to groundwater migration...Understanding the factors triggering slope failure is essential to ensure the safety of buildings and transportation infrastructure on slopes. Specifically,the failure of stabilizing piles due to groundwater migration and freeze–thaw(FT) cycles is a significant factor causing slope failure. This study aims to investigate the transmedia seepage characteristics at slope–concrete stabilizing pile interface systems by using silty clay and concrete with varying microstructure characteristics under FT cycles. To this end, a self-developed indoor test device for transmedia water migration, combined with a macro-meso-micro multiscale testing approach, was used to analyze the laws and mechanisms of transmedia seepage at the interface systems. The effect of the medium's microstructure characteristics on the transmedia seepage behavior at the interface systems under FT cycles was also assessed. Results indicated that the transmedia water migration exhibited particularity due to the migration of soil particles and the low permeability characteristics of concrete. The water content in the media increased significantly within the range of 1/3–2/3 of the height from the interface for soil and within 5 mm from the interface for concrete.FT cycles promoted the increase and penetration of cracks within the medium, enhancing the permeability of the slope-concrete stabilizing pile interface systems.With the increase in FT cycles, the porosity inside the medium first decreased and then increased, and the porosity reached the minimum after 25 FT cycles and the maximum after 75 FT cycles, and the water content of the medium after water migration was positively correlated with the porosity. FT cycles also significantly influenced the temporal variation characteristics of soil moisture and the migration path of water in concrete. The study results could serve as a reference for related research on slope stability assessment.展开更多
As a new kind of technology in retaining structures, the characteristics of double-row piles are significantly affected by spatial effects. In this paper, double-row piles as a retaining structure are simulated numeri...As a new kind of technology in retaining structures, the characteristics of double-row piles are significantly affected by spatial effects. In this paper, double-row piles as a retaining structure are simulated numerically in three-dimension by finite element software PLAXIS 3D FOUNDATION. The behavior differences of piles in different positions around the foundation pit are analyzed. By changing the parameters, including the length-width ratio, the excavation depth, the distance between rows and the diameter of piles, the variations of the lateral deformation, the bending moment and the earth pressure around the piles are determined. The reasonable values of parameters and some suggestions with consideration of earth pressure are proposed for the design of double-row piles as a retaining structure. The results show that the lateral deformation and bending moment are the largest in the middle of long side of the foundation pit, which is identified as the most unfavorable position. It is indicated that the earth pressure between rows above pit bottom is close to active earth pressure, while the earth pressure between rows under pit bottom is close to static earth pressure. It is suggested that 1/2-2/3 of pile length, 0.6-1.2 m, 3d-6d, and 2d-2.5d be chosen as embedded depth of piles, diameter of piles, distance between rows, and distance between piles, respectively, where d is the pile diameter.展开更多
This paper introduces a new prefabricated recyclable double-row piles retaining system for excavations in silty clay ground.Laboratory model test and numerical simulation are conducted to study the system behavior upo...This paper introduces a new prefabricated recyclable double-row piles retaining system for excavations in silty clay ground.Laboratory model test and numerical simulation are conducted to study the system behavior upon excavation.The horizontal displacement(δ_(h)),Von Mises stress(δ_(M)),strain(ε),ground surface settlement(δ_(v)),and earth pressure are systematically investigated.Furthermore,the monitoring data of 13 excavation cases supported by double-row piles retaining system are presented and discussed.The experimental results can basically match the numerical results,and the maximumδ_(M),maximum bending moment(M_(max)),maximum horizontal displacement(δ_(hm))of structural members are all less than the tolerance limits.The ground surface settlement model of double-row piles retaining system consists of three zones,i.e.,rebound influence zone,primary influence zone and secondary influence zone.The dhm values are 0.07%–1.42%of the excavation depth(He).The maximum ground surface settlement(δ_(vm))is generally less than dhm.The ratio ofδ_(vm)=δ_(hm)varies between 0.09 and 0.76,with an average value of 0.5.The observed earth pressure on the retained side of front pile(paf)is about 0.53–0.57γH below the excavation surface.Above the excavation surface,p_(af)decreases dramatically when getting closer to the ground surface.展开更多
With the construction of the Three Gorges Reservoir dam,frequent reservoir landslide events have been recorded.In recent years,multi-row stabilizing piles(MRSPs)have been used to stabilize massive reservoir landslides...With the construction of the Three Gorges Reservoir dam,frequent reservoir landslide events have been recorded.In recent years,multi-row stabilizing piles(MRSPs)have been used to stabilize massive reservoir landslides in China.In this study,two centrifuge model tests were carried out to study the unreinforced and MRSP-reinforced slopes subjected to reservoir water level(RWL)operation,using the Taping landslide as a prototype.The results indicate that the RWL rising can provide lateral support within the submerged zone and then produce the inward seepage force,eventually strengthening the slope stability.However,a rapid RWL drawdown may induce outward seepage forces and a sudden debuttressing effect,consequently reducing the effective soil normal stress and triggering partial pre-failure within the RWL fluctuation zone.Furthermore,partial deformation and subsequent soil structure damage generate excess pore water pressures,ultimately leading to the overall failure of the reservoir landslide.This study also reveals that a rapid increase in the downslope driving force due to RWL drawdown significantly intensifies the lateral earth pressures exerted on the MRSPs.Conversely,the MRSPs possess a considerable reinforcement effect on the reservoir landslide,transforming the overall failure into a partial deformation and failure situated above and in front of the MRSPs.The mechanical transfer behavior observed in the MRSPs demonstrates a progressive alteration in relation to RWL fluctuations.As the RWL rises,the mechanical states among MRSPs exhibit a growing imbalance.The shear force transfer factor(i.e.the ratio of shear forces on pile of the n th row to that of the first row)increases significantly with the RWL drawdown.This indicates that the mechanical states among MRSPs tend toward an enhanced equilibrium.The insights gained from this study contribute to a more comprehensive understanding of the failure mechanisms of reservoir landslides and the mechanical behavior of MRSPs in reservoir banks.展开更多
Large-scale shaking table tests were conducted to study the dynamic response of a slope reinforced by double-row anti-sliding piles and prestressed anchor cables. The test results show that the reinforcement suppresse...Large-scale shaking table tests were conducted to study the dynamic response of a slope reinforced by double-row anti-sliding piles and prestressed anchor cables. The test results show that the reinforcement suppressed the acceleration amplification effectively. The axial force time histories are decomposed into a baseline part and a vibration part in this study. The baseline part of axial force well revealed the seismic slope stability, the peak vibration values of axial force of the anchor cables changed significantly in different area of the slope under seismic excitations. The peak lateral earth pressure acting on the back of the anti-sliding pile located at the slope toe was much larger than that acting on the back of the anti-sliding pile located at the slope waist. The test results indicate an obvious load sharing ratio difference between these two anti-slide piles, the load sharing ratio between the two anti-sliding piles located at the slope toe and the slope waist varied mainly in a range of 2-5. The anti-slide pile at the slope waist suppressed the horizontal displacement of the slope surface.展开更多
A rigorous analytical model is developed for simulating the vibration behaviors of large-diameter openended pipe piles(OEPPs)and surrounding soil undergoing high-strain impact loading.To describe the soil behavior,the...A rigorous analytical model is developed for simulating the vibration behaviors of large-diameter openended pipe piles(OEPPs)and surrounding soil undergoing high-strain impact loading.To describe the soil behavior,the soil along pile shaft is divided into slip and nonslip zones and the base soil is modeled as a fictitious-soil pile(FSP)to account for the wave propagation in the soil.True soil properties are adopted and slippage at the pile-soil interface is considered,allowing realistic representation of largediameter OEPP mechanics.The developed model is validated by comparing with conventional models and finite element method(FEM).It is further used to successfully simulate and interpret the behaviors of a steel OEPP during the offshore field test.It is found that the variation in the vertical vibrations of shaft soil along radial direction is significant for large-diameter OEPPs,and the velocity amplitudes of the internal and external soil attenuate following different patterns.The shaft soil motion may not attenuate with depth due to the soil slippage,while the wave attenuation at base soil indicates an influence depth,with a faster attenuation rate than that in the pile.The findings from the current study should aid in simulating the vibration behaviors of large-diameter OEPP-soil system under high-strain dynamic loading.展开更多
In an effort to investigate and quantify the patterns of local scour,researchers embarked on an in-depth study using a systematic experimental approach.The research focused on the effects of local scour around a set o...In an effort to investigate and quantify the patterns of local scour,researchers embarked on an in-depth study using a systematic experimental approach.The research focused on the effects of local scour around a set of four piles,each subjected to different hydromechanical conditions.In particular,this study aimed to determine how different attack angles—the angles at which the water flow impinges on the piles,and gap ratios—the ratios of the spacing between the piles to their diameters,influence the extent and nature of scour.A comprehensive series of 35 carefully designed experiments were orchestrated,each designed to dissect the nuances in how the gap ratio and attack angle might contribute to changes in the local scour observed at the base of pile groups.During these experimental trials,a wealth of local scour data were collected to support the analysis.These data included precise topographic profiles of the sediment bed around the pile groups,as well as detailed scour time histories showing the evolution of scour at strategic feature points throughout the test procedure.The analysis of the experimental data provided interesting insights.The study revealed that the interplay between the gap ratio and the attack angle had a pronounced influence on the scouring dynamics of the pile groups.One of the key observations was that the initial phases of scour,particularly within the first hour of water flow exposure,were characterized by a sharp increase in the scour depth occurring immediately in front of the piles.After this initial rapid development,the scour depth transitioned to a more gradual change rate.In contrast,the scour topography around the piles continuously evolved.This suggests that sediment displacement and the associated sculpting of the seabed around pile foundations are sustained and progressive processes,altering the underwater landscape over time.The results of this empirical investigation have significant implications for the design and construction of offshore multi-pile foundations,providing a critical reference for engineers and designers to estimate the expected scour depth around such structures,which is an integral part of decisions regarding foundation design,selection of structural materials,and implementation of scour protection measures.展开更多
During the construction of cast-in-place piles in warm permafrost,the heat carried by concrete and the cement hydration reaction can cause strong thermal disturbance to the surrounding permafrost.Since the bearing cap...During the construction of cast-in-place piles in warm permafrost,the heat carried by concrete and the cement hydration reaction can cause strong thermal disturbance to the surrounding permafrost.Since the bearing capacity of the pile is quite small before the full freeze-back,the quick refreezing of the native soils surrounding the cast-in-place pile has become the focus of the infrastructure construction in permafrost.To solve this problem,this paper innovatively puts forward the application of the artificial ground freezing(AGF)method at the end of the curing period of cast-in-place piles in permafrost.A field test on the AGF was conducted at the Beiluhe Observation and Research Station of Frozen Soil Engineering and Environment(34°51.2'N,92°56.4'E)in the Qinghai Tibet Plateau(QTP),and then a 3-D numerical model was established to investigate the thermal performance of piles using AGF under different engineering conditions.Additionally,the long-term thermal performance of piles after the completion of AGF under different conditions was estimated.Field experiment results demonstrate that AGF is an effective method to reduce the refreezing time of the soil surrounding the piles constructed in permafrost terrain,with the ability to reduce the pile-soil interface temperatures to below the natural ground temperature within 3 days.Numerical results further prove that AGF still has a good cooling effect even under unfavorable engineering conditions such as high pouring temperature,large pile diameter,and large pile length.Consequently,the application of this method is meaningful to save the subsequent latency time and solve the problem of thermal disturbance in pile construction in permafrost.The research results are highly relevant for the spread of AGF technology and the rapid building of pile foundations in permafrost.展开更多
Despite the continuous advancements of engineering construction in high-intensity areas,many engineering landslides are still manufactured with huge thrust force,and double-row piles are effective to control such larg...Despite the continuous advancements of engineering construction in high-intensity areas,many engineering landslides are still manufactured with huge thrust force,and double-row piles are effective to control such large landslides.In this study,large shaking table test were performed to test and obtain multi-attribute seismic data such as feature image,acceleration,and dynamic soil pressure.Through the feature image processing analysis,the deformation characteristics for the slope reinforced by double-row piles were revealed.By analyzing the acceleration and the dynamic soil pressure time domain,the spatial dynamic response characteristics were revealed.Using Fast Fourier Transform and half-power bandwidth,the damping ratio of acceleration and dynamic soil pressure was obtained.Following that,the Seism Signal was used to calculate the spectral displacement of the accelerations to obtain the regional differences of spectral displacement.The results showed that the overall deformation mechanism of the slope originates from tension failure in the soil mass.The platform at the back of the slope was caused by seismic subsidence,and the peak acceleration ratio was positively correlated with the relative pile heights.The dynamic soil pressure of the front row piles showed an inverted"K"-shaped distribution,but that of the back row piles showed an"S"-shaped distribution.The predominant frequency of acceleration was 2.16 Hz,and the main frequency band was 0.7-6.87 Hz;for dynamic soil pressure,the two parameters became 1.15 Hz and 0.5-6.59 Hz,respectively.In conclusion,dynamic soil pressure was more sensitive to dampening effects than acceleration.Besides,compared to acceleration,dynamic soil pressure exhibited larger loss factors and lower resonance peaks.Finally,back row pile heads were highly sensitive to spectral displacement compared to front row pile heads.These findings may be of reference value for future seismic designs of double-row piles.展开更多
Square piles of reinforced concrete(RC)in marine environments are susceptible to chloride-inducedcorrosion.A novel reverse-seepage technique(RST)is applied to square piles to block the intrusion of chlorides.Thisresea...Square piles of reinforced concrete(RC)in marine environments are susceptible to chloride-inducedcorrosion.A novel reverse-seepage technique(RST)is applied to square piles to block the intrusion of chlorides.Thisresearch introduces a computational model designed to predict the lifespan of corrosion initiation in reinforced concretesquare piles when applied reverse-seepage pressure.The model considers the impacts of chloride binding and the tripletime-dependence property among the permeability,the corrected surface chloride concentration,and the diffusioncoefficient.The proposed numerical model is solved using the alternating direction implicit(ADI)approach,and itsaccuracy and reliability are evaluated by contrasting the computational outcomes with the analytical solution andexperimental results.Furthermore,the primary factors contributing to the corrosion of reinforced concrete square pilesare analyzed.The results indicate that applying RST can decrease the chloride penetration depth and prolong the lifespanof corrosion initiation in square piles.The water-cement ratio and reverse seepage pressure are the most influentialfactors.A water pressure of 0.4 MPa can double the life of concrete,and the durable life of concrete with a water-cementratio of 0.3 can reach 100 years.展开更多
To adress the problems of insufficient consideration of charging pile resource limitations,discrete-time scheduling methods that do not meet the actual demand and insufficient descriptions of peak-shaving response cap...To adress the problems of insufficient consideration of charging pile resource limitations,discrete-time scheduling methods that do not meet the actual demand and insufficient descriptions of peak-shaving response capability in current electric vehicle(EV)opti-mization scheduling,edge intelligence-oriented electric vehicle optimization scheduling and charging station peak-shaving response capability assessment methods are proposed on the basis of the consideration of electric vehicle and charging pile matching.First,an edge-intelligence-oriented electric vehicle regulation frame for charging stations is proposed.Second,continuous time variables are used to represent the available charging periods,establish the charging station controllable EV load model and the future available charging pile mathematical model,and establish the EV and charging pile matching matrix and constraints.Then,with the goal of maximizing the user charging demand and reducing the charging cost,the charging station EV optimal scheduling model is established,and the EV peak response capacity assessment model is further established by considering the EV load shifting constraints under different peak response capacities.Finally,a typical scenario of a real charging station is taken as an example for the analysis of optimal EV scheduling and peak shaving response capacity,and the proposed method is compared with the traditional method to verify the effectiveness and practicality of the proposed method.展开更多
Ensuring the reliability of pipe pile designs under earthquake loading necessitates an accurate determination of lateral displacement and bending moment,typically achieved through complex numerical modeling to address...Ensuring the reliability of pipe pile designs under earthquake loading necessitates an accurate determination of lateral displacement and bending moment,typically achieved through complex numerical modeling to address the intricacies of soil-pile interaction.Despite recent advancements in machine learning techniques,there is a persistent need to establish data-driven models that can predict these parameters without using numerical simulations due to the difficulties in conducting correct numerical simulations and the need for constitutive modelling parameters that are not readily available.This research presents novel lateral displacement and bending moment predictive models for closed and open-ended pipe piles,employing a Genetic Programming(GP)approach.Utilizing a soil dataset extracted from existing literature,comprising 392 data points for both pile types embedded in cohesionless soil and subjected to earthquake loading,the study intentionally limited input parameters to three features to enhance model simplicity:Standard Penetration Test(SPT)corrected blow count(N60),Peak Ground Acceleration(PGA),and pile slenderness ratio(L/D).Model performance was assessed via coefficient of determination(R^(2)),Root Mean Squared Error(RMSE),and Mean Absolute Error(MAE),with R^(2) values ranging from 0.95 to 0.99 for the training set,and from 0.92 to 0.98 for the testing set,which indicate of high accuracy of prediction.Finally,the study concludes with a sensitivity analysis,evaluating the influence of each input parameter across different pile types.展开更多
To investigate the seismic performance of the double-row pre-stressed anchor piles （DRPAPs） on the Yuxi-Mengzi railway, FLAC3D was used to construct a three-dimensional model. Using Koyna earthquake records as input...To investigate the seismic performance of the double-row pre-stressed anchor piles （DRPAPs） on the Yuxi-Mengzi railway, FLAC3D was used to construct a three-dimensional model. Using Koyna earthquake records as input motions, dynamic time-history analyses were carried out. In the analyses, we compared earth pressure on the front and back of the piles and deformation of the piles under different seismic forces with or without anchor cables. With the anchor cable present, the earth pressure on the back of the pile＇s free section increases, but that on the back of the pile＇s anchorage section decreases. Also, with anchor cables, the earth pressure on the front of the upper pile decreases, and that on the back of the lower pile decreases.展开更多
A control strategy of repetitive control without inductorance decoupling was proposed to address the problem of high total harmonic distortion(THD)rate of the network-side current caused by the reduced stability of th...A control strategy of repetitive control without inductorance decoupling was proposed to address the problem of high total harmonic distortion(THD)rate of the network-side current caused by the reduced stability of the rectifier module of the DC charging pile under weak grid as well as the dead zone and nonlinearity of switching devices during charging.Firstly,the parallel repetitive control was constructed in the inner current loop,and the proportional-integral(PI)+repetitive controller based on parallel structure was designed.For system compensation,a second-order low-pass filter was selected to correct the system,and the network-side current harmonics were actively suppressed without increasing the filtering device,which effectively improves the quality of grid-connected current.Secondly,based on the synthetic vector method,the controller parameters were designed to realize the elimination of main pole by establishing two synchronous rotation coordinate system vector differential equations,so as to realize the inductanceless decoupling to cope with the influence of network-side inductance fluctuation on the stability of the control system under weak grid.By theoretical analysis and simulation,the proposed control strategy was embedded into the self-developed digital signal processor for the rectifier module of DC charging pile,simulated dynamic and steady-state operation experiments were conducted,and comparative analysis was performed to prove the feasibility of the proposed control strategy.展开更多
Response surface method is used to study the reliability analysis of laterally loaded piles in sloping ground. A development load-displacement （p-y） curve for laterally loaded pile response in sloping ground is used...Response surface method is used to study the reliability analysis of laterally loaded piles in sloping ground. A development load-displacement （p-y） curve for laterally loaded pile response in sloping ground is used to model the pile-soil system, both the pile head displacement and the maximum bending moment of the piles are used as the performance criteria in this study. The reliability analysis method of the laterally loaded pile in sloping ground under the pile head displacement and the maximum bending moment failure modes is proposed, which is in good agreement with the Monte Carlo method. The influences on the probability index of failure by a number of parameters are discussed. It is shown that the variability of pile head displacement increases with the increase in the coefficients of variation of ultimate bearing capacity factor （Npu）, secant elastic modulus at 50%（E50） and level load （H）. A negative correlation between Npu and non-dimensional factor （λ） leads to less spread out probability density function （PDF） of the pile head displacement;in contrast, a positive correlation between Npu andλgives a great variation in the PDF of pile head displacement. As for bearing capacity factor on ground surface （Npo） and λ, both negative and positive correlations between them give a great variation in the PDF of pile head displacement, and a negative correlation will obviously increase the variability of the response.展开更多
This paper discusses a new technique to improve soft ground with grouting piles and deep mixing piles. The bearing capacity of composite ground and the stress ratio between piles and soil is discussed by means of the ...This paper discusses a new technique to improve soft ground with grouting piles and deep mixing piles. The bearing capacity of composite ground and the stress ratio between piles and soil is discussed by means of the static test. Based on Mindlin solution and Boussinesq solution, the additional stress and settlement of the composite ground are acquired.Compared the practical value with calculation, a better calculating method is confirmed.展开更多
The methodology of predicting pile shaft skin ultimate friction has been studied in a systematic way. In the light of that, the analysis of the pile shaft resistance for bored and cast in situ piles in cohesive soil...The methodology of predicting pile shaft skin ultimate friction has been studied in a systematic way. In the light of that, the analysis of the pile shaft resistance for bored and cast in situ piles in cohesive soils was carried out thoroughly in the basis of field performance data of 10 fully instrumented large diameter bored piles (LDBPs) used as the bridge foundation. The undrained strength index μ in term of cohesive soils was brought forward in allusion to the cohesive soils in the consistence plastic state, and can effectively combine the friction angle and the cohesion of cohesive soils in undrained condition. And that the classical ' α method' was modified much in effect to predict the pile shaft skin friction of LDBPs in cohesive soils. Furthermore, the approach of standard penetration test (SPT) N value used to estimate the pile shaft skin ultimate friction was analyzed, and the calculating formulae were established for LDBPs in clay and silt clay respectively.展开更多
The impact of excavation on the reliability of anti- pull piles is studied, and three cases of reliability analysis, named reliability of ultimate limit state （ULS）, reliability of serviceability limit state （SLS）...The impact of excavation on the reliability of anti- pull piles is studied, and three cases of reliability analysis, named reliability of ultimate limit state （ULS）, reliability of serviceability limit state （SLS） and reliability of system （SYS） are studied. The reduction factor of the pile capacity is used to calculate the reliability indices for the three cases. The ratio ξ of the pile capacity of SLS to the pile capacity of ULS has a significant influence on the reliability indices of SLS and SYS. The mean value μξ of the ratio ξ： is considered as a random variable to study the reliability indices of SLS and SYS. The numerical example demonstrates that the excavation depth and the excavation diameter are proved to have significant influences on the reduction factor of the pile capacity and the reliability indices. The reliability indices decrease with the increase in the excavation depth, and the excavation diameter has a considerable influence on the reliability index when the excavation is relatively deep. In addition, μξ has a significant influence on the reliability indices of SLS and SYS. For a more accurate estimation of μξ, further research should be conducted to study μξ.展开更多
Two full-scale experiments using controlled blasting were conducted in the Port of Tokachi on Hokkaido Island, Japan,to assess the behavior of piles and pipelines subjected to lateral spreading.Test specimens were ext...Two full-scale experiments using controlled blasting were conducted in the Port of Tokachi on Hokkaido Island, Japan,to assess the behavior of piles and pipelines subjected to lateral spreading.Test specimens were extensively instrumented with strain gauges to measure the distribution of moment during lateral spreading.This allowed us to compute the loading condition,as well as to conduct damage and performance assessments on the piles and pipelines.This paper presents the test results and discussions on the response of single piles and pipelines observed from the full-scale experiments.Based on the test results,it can be concluded that using controlled blasting successfully liquefied the soil,and subsequently induced lateral spreading.The movements of the single pile,as well as the transverse pipelines,were approximately the same as the free field soil movement.Observed moment distribution of the single pile indicated that global translation of the liquefied soil layer provided insignificant force to the pile.In addition,the degree of fixity at the pile tip significantly affected the moment along the pile as well as the pile head displacement.The pile with a higher degree of fixity at the pile tip had smaller pile head displacement but larger maximum moment.展开更多
基金the Key Research Program of Shanghai Construction Group(No.17JCSF-37)。
文摘Double-row pile(DRP)retaining systems have been widely used in deep excavations in China.Soil between the front and back-row piles(FBP soil)is often improved to decrease the displacement of DRPs in soft soil areas,but the improvement efficiency has rarely been researched.A large and deep excavation supported by a DRP retaining system is introduced,and the effect of FBP soil improvement is discussed by comparing the finite element analysis and the monitoring results.Then,a parametric study of DRP using the finite element method considering the small strain of soil is conducted to investigate the effect of FBP soil improvement.It was shown that the pile deflection and bending moment decrease when the FBP soil is improved.Moreover,the most efficient way to minimize the pile deflection and bending moment is to improve the FBP soil around the excavation level.The FBP soil improvement 2-4 m below the pile head is not very useful for reducing the pile deflection and can be eliminated when the pile displacement limit is not very strict.
基金financially supported by Jilin Provincial Natural Science Foundation (No.20220101164JC)。
文摘Understanding the factors triggering slope failure is essential to ensure the safety of buildings and transportation infrastructure on slopes. Specifically,the failure of stabilizing piles due to groundwater migration and freeze–thaw(FT) cycles is a significant factor causing slope failure. This study aims to investigate the transmedia seepage characteristics at slope–concrete stabilizing pile interface systems by using silty clay and concrete with varying microstructure characteristics under FT cycles. To this end, a self-developed indoor test device for transmedia water migration, combined with a macro-meso-micro multiscale testing approach, was used to analyze the laws and mechanisms of transmedia seepage at the interface systems. The effect of the medium's microstructure characteristics on the transmedia seepage behavior at the interface systems under FT cycles was also assessed. Results indicated that the transmedia water migration exhibited particularity due to the migration of soil particles and the low permeability characteristics of concrete. The water content in the media increased significantly within the range of 1/3–2/3 of the height from the interface for soil and within 5 mm from the interface for concrete.FT cycles promoted the increase and penetration of cracks within the medium, enhancing the permeability of the slope-concrete stabilizing pile interface systems.With the increase in FT cycles, the porosity inside the medium first decreased and then increased, and the porosity reached the minimum after 25 FT cycles and the maximum after 75 FT cycles, and the water content of the medium after water migration was positively correlated with the porosity. FT cycles also significantly influenced the temporal variation characteristics of soil moisture and the migration path of water in concrete. The study results could serve as a reference for related research on slope stability assessment.
文摘As a new kind of technology in retaining structures, the characteristics of double-row piles are significantly affected by spatial effects. In this paper, double-row piles as a retaining structure are simulated numerically in three-dimension by finite element software PLAXIS 3D FOUNDATION. The behavior differences of piles in different positions around the foundation pit are analyzed. By changing the parameters, including the length-width ratio, the excavation depth, the distance between rows and the diameter of piles, the variations of the lateral deformation, the bending moment and the earth pressure around the piles are determined. The reasonable values of parameters and some suggestions with consideration of earth pressure are proposed for the design of double-row piles as a retaining structure. The results show that the lateral deformation and bending moment are the largest in the middle of long side of the foundation pit, which is identified as the most unfavorable position. It is indicated that the earth pressure between rows above pit bottom is close to active earth pressure, while the earth pressure between rows under pit bottom is close to static earth pressure. It is suggested that 1/2-2/3 of pile length, 0.6-1.2 m, 3d-6d, and 2d-2.5d be chosen as embedded depth of piles, diameter of piles, distance between rows, and distance between piles, respectively, where d is the pile diameter.
基金supported by the National Key Research and Development Program of China(Grant No.2021YFC3100803)the National Natural Science Founda tion of China(Grant Nos.52208380 and 52078506)+2 种基金the Guangdong Basic and Applied Basic ResearchFoundation,China(Grant No.2023A1515012159)Open Research Fund of State Key Laboratory of Geomechanics and Geotechnical Engineering,Institute of Rock and Soil Mechanics,Chinese Academy of Sciences(Grant No.SKLGME021022)the Science and Technology Program of Guangzhou Municipal Construction Group Co.,Ltd.,China(Grant No.2022-KJ004).
文摘This paper introduces a new prefabricated recyclable double-row piles retaining system for excavations in silty clay ground.Laboratory model test and numerical simulation are conducted to study the system behavior upon excavation.The horizontal displacement(δ_(h)),Von Mises stress(δ_(M)),strain(ε),ground surface settlement(δ_(v)),and earth pressure are systematically investigated.Furthermore,the monitoring data of 13 excavation cases supported by double-row piles retaining system are presented and discussed.The experimental results can basically match the numerical results,and the maximumδ_(M),maximum bending moment(M_(max)),maximum horizontal displacement(δ_(hm))of structural members are all less than the tolerance limits.The ground surface settlement model of double-row piles retaining system consists of three zones,i.e.,rebound influence zone,primary influence zone and secondary influence zone.The dhm values are 0.07%–1.42%of the excavation depth(He).The maximum ground surface settlement(δ_(vm))is generally less than dhm.The ratio ofδ_(vm)=δ_(hm)varies between 0.09 and 0.76,with an average value of 0.5.The observed earth pressure on the retained side of front pile(paf)is about 0.53–0.57γH below the excavation surface.Above the excavation surface,p_(af)decreases dramatically when getting closer to the ground surface.
基金funded by Chongqing Natural Science Key Program of China(Grant No.cstc2020jcyj-zdxmX0019)China Geological Survey Program(Grant No.DD20190637/DD20221748).
文摘With the construction of the Three Gorges Reservoir dam,frequent reservoir landslide events have been recorded.In recent years,multi-row stabilizing piles(MRSPs)have been used to stabilize massive reservoir landslides in China.In this study,two centrifuge model tests were carried out to study the unreinforced and MRSP-reinforced slopes subjected to reservoir water level(RWL)operation,using the Taping landslide as a prototype.The results indicate that the RWL rising can provide lateral support within the submerged zone and then produce the inward seepage force,eventually strengthening the slope stability.However,a rapid RWL drawdown may induce outward seepage forces and a sudden debuttressing effect,consequently reducing the effective soil normal stress and triggering partial pre-failure within the RWL fluctuation zone.Furthermore,partial deformation and subsequent soil structure damage generate excess pore water pressures,ultimately leading to the overall failure of the reservoir landslide.This study also reveals that a rapid increase in the downslope driving force due to RWL drawdown significantly intensifies the lateral earth pressures exerted on the MRSPs.Conversely,the MRSPs possess a considerable reinforcement effect on the reservoir landslide,transforming the overall failure into a partial deformation and failure situated above and in front of the MRSPs.The mechanical transfer behavior observed in the MRSPs demonstrates a progressive alteration in relation to RWL fluctuations.As the RWL rises,the mechanical states among MRSPs exhibit a growing imbalance.The shear force transfer factor(i.e.the ratio of shear forces on pile of the n th row to that of the first row)increases significantly with the RWL drawdown.This indicates that the mechanical states among MRSPs tend toward an enhanced equilibrium.The insights gained from this study contribute to a more comprehensive understanding of the failure mechanisms of reservoir landslides and the mechanical behavior of MRSPs in reservoir banks.
基金financially supported by the National Key R&D Program of China(No.2018YFC1508601)the Fundamental Research Funds for the Central University(20822041B4038)
文摘Large-scale shaking table tests were conducted to study the dynamic response of a slope reinforced by double-row anti-sliding piles and prestressed anchor cables. The test results show that the reinforcement suppressed the acceleration amplification effectively. The axial force time histories are decomposed into a baseline part and a vibration part in this study. The baseline part of axial force well revealed the seismic slope stability, the peak vibration values of axial force of the anchor cables changed significantly in different area of the slope under seismic excitations. The peak lateral earth pressure acting on the back of the anti-sliding pile located at the slope toe was much larger than that acting on the back of the anti-sliding pile located at the slope waist. The test results indicate an obvious load sharing ratio difference between these two anti-slide piles, the load sharing ratio between the two anti-sliding piles located at the slope toe and the slope waist varied mainly in a range of 2-5. The anti-slide pile at the slope waist suppressed the horizontal displacement of the slope surface.
基金support from the Exploring Youth Project of Zhejiang Natural Science Foundation (Grant No.LQ24E080009)the Key Project of Natural Science Foundation of Zhejiang Province (Grant No.LXZ22E080001)the National Natural Science Foundation of China (Grant No.52108347).
文摘A rigorous analytical model is developed for simulating the vibration behaviors of large-diameter openended pipe piles(OEPPs)and surrounding soil undergoing high-strain impact loading.To describe the soil behavior,the soil along pile shaft is divided into slip and nonslip zones and the base soil is modeled as a fictitious-soil pile(FSP)to account for the wave propagation in the soil.True soil properties are adopted and slippage at the pile-soil interface is considered,allowing realistic representation of largediameter OEPP mechanics.The developed model is validated by comparing with conventional models and finite element method(FEM).It is further used to successfully simulate and interpret the behaviors of a steel OEPP during the offshore field test.It is found that the variation in the vertical vibrations of shaft soil along radial direction is significant for large-diameter OEPPs,and the velocity amplitudes of the internal and external soil attenuate following different patterns.The shaft soil motion may not attenuate with depth due to the soil slippage,while the wave attenuation at base soil indicates an influence depth,with a faster attenuation rate than that in the pile.The findings from the current study should aid in simulating the vibration behaviors of large-diameter OEPP-soil system under high-strain dynamic loading.
基金financially supported by the National Natural Science Foundation of China(Grant No.51890913)the Natural Science Foundation of Sichuan Province of China(Grant No.2023YFQ0111)。
文摘In an effort to investigate and quantify the patterns of local scour,researchers embarked on an in-depth study using a systematic experimental approach.The research focused on the effects of local scour around a set of four piles,each subjected to different hydromechanical conditions.In particular,this study aimed to determine how different attack angles—the angles at which the water flow impinges on the piles,and gap ratios—the ratios of the spacing between the piles to their diameters,influence the extent and nature of scour.A comprehensive series of 35 carefully designed experiments were orchestrated,each designed to dissect the nuances in how the gap ratio and attack angle might contribute to changes in the local scour observed at the base of pile groups.During these experimental trials,a wealth of local scour data were collected to support the analysis.These data included precise topographic profiles of the sediment bed around the pile groups,as well as detailed scour time histories showing the evolution of scour at strategic feature points throughout the test procedure.The analysis of the experimental data provided interesting insights.The study revealed that the interplay between the gap ratio and the attack angle had a pronounced influence on the scouring dynamics of the pile groups.One of the key observations was that the initial phases of scour,particularly within the first hour of water flow exposure,were characterized by a sharp increase in the scour depth occurring immediately in front of the piles.After this initial rapid development,the scour depth transitioned to a more gradual change rate.In contrast,the scour topography around the piles continuously evolved.This suggests that sediment displacement and the associated sculpting of the seabed around pile foundations are sustained and progressive processes,altering the underwater landscape over time.The results of this empirical investigation have significant implications for the design and construction of offshore multi-pile foundations,providing a critical reference for engineers and designers to estimate the expected scour depth around such structures,which is an integral part of decisions regarding foundation design,selection of structural materials,and implementation of scour protection measures.
基金supported by the National Natural Science Foundation of China(Grant No.42071095)the Program of the State Key Laboratory of Frozen Soil Engineering(Grant No.SKLFSE-ZQ-59)+1 种基金the Science and Technology Project of Gansu Province(Grant No.22JR5RA086)the Science and Technology Research and Development Program of the Qinghai-Tibet Group Corporation(Grant No.QZ2022-G02).
文摘During the construction of cast-in-place piles in warm permafrost,the heat carried by concrete and the cement hydration reaction can cause strong thermal disturbance to the surrounding permafrost.Since the bearing capacity of the pile is quite small before the full freeze-back,the quick refreezing of the native soils surrounding the cast-in-place pile has become the focus of the infrastructure construction in permafrost.To solve this problem,this paper innovatively puts forward the application of the artificial ground freezing(AGF)method at the end of the curing period of cast-in-place piles in permafrost.A field test on the AGF was conducted at the Beiluhe Observation and Research Station of Frozen Soil Engineering and Environment(34°51.2'N,92°56.4'E)in the Qinghai Tibet Plateau(QTP),and then a 3-D numerical model was established to investigate the thermal performance of piles using AGF under different engineering conditions.Additionally,the long-term thermal performance of piles after the completion of AGF under different conditions was estimated.Field experiment results demonstrate that AGF is an effective method to reduce the refreezing time of the soil surrounding the piles constructed in permafrost terrain,with the ability to reduce the pile-soil interface temperatures to below the natural ground temperature within 3 days.Numerical results further prove that AGF still has a good cooling effect even under unfavorable engineering conditions such as high pouring temperature,large pile diameter,and large pile length.Consequently,the application of this method is meaningful to save the subsequent latency time and solve the problem of thermal disturbance in pile construction in permafrost.The research results are highly relevant for the spread of AGF technology and the rapid building of pile foundations in permafrost.
基金the financial support by the National Key R&D Program of China(No.2018YFC1504901)Gansu Province Youth Science and Technology Fund program,China(Grant No.21JR7RA739)+1 种基金Natural Science Foundation of Gansu Province,China(Grant No.21JR7RA738)Natural Science Foundation of Gansu Province,China(No.145RJZA068)。
文摘Despite the continuous advancements of engineering construction in high-intensity areas,many engineering landslides are still manufactured with huge thrust force,and double-row piles are effective to control such large landslides.In this study,large shaking table test were performed to test and obtain multi-attribute seismic data such as feature image,acceleration,and dynamic soil pressure.Through the feature image processing analysis,the deformation characteristics for the slope reinforced by double-row piles were revealed.By analyzing the acceleration and the dynamic soil pressure time domain,the spatial dynamic response characteristics were revealed.Using Fast Fourier Transform and half-power bandwidth,the damping ratio of acceleration and dynamic soil pressure was obtained.Following that,the Seism Signal was used to calculate the spectral displacement of the accelerations to obtain the regional differences of spectral displacement.The results showed that the overall deformation mechanism of the slope originates from tension failure in the soil mass.The platform at the back of the slope was caused by seismic subsidence,and the peak acceleration ratio was positively correlated with the relative pile heights.The dynamic soil pressure of the front row piles showed an inverted"K"-shaped distribution,but that of the back row piles showed an"S"-shaped distribution.The predominant frequency of acceleration was 2.16 Hz,and the main frequency band was 0.7-6.87 Hz;for dynamic soil pressure,the two parameters became 1.15 Hz and 0.5-6.59 Hz,respectively.In conclusion,dynamic soil pressure was more sensitive to dampening effects than acceleration.Besides,compared to acceleration,dynamic soil pressure exhibited larger loss factors and lower resonance peaks.Finally,back row pile heads were highly sensitive to spectral displacement compared to front row pile heads.These findings may be of reference value for future seismic designs of double-row piles.
基金Projects(52178371,52108355,52178321)supported by the National Natural Science Foundation of ChinaProject(202305)supported by the Research Project of Engineering Research Centre of Rock-Soil Drilling&Excavation and Protection,Ministry of Education,China。
文摘Square piles of reinforced concrete(RC)in marine environments are susceptible to chloride-inducedcorrosion.A novel reverse-seepage technique(RST)is applied to square piles to block the intrusion of chlorides.Thisresearch introduces a computational model designed to predict the lifespan of corrosion initiation in reinforced concretesquare piles when applied reverse-seepage pressure.The model considers the impacts of chloride binding and the tripletime-dependence property among the permeability,the corrected surface chloride concentration,and the diffusioncoefficient.The proposed numerical model is solved using the alternating direction implicit(ADI)approach,and itsaccuracy and reliability are evaluated by contrasting the computational outcomes with the analytical solution andexperimental results.Furthermore,the primary factors contributing to the corrosion of reinforced concrete square pilesare analyzed.The results indicate that applying RST can decrease the chloride penetration depth and prolong the lifespanof corrosion initiation in square piles.The water-cement ratio and reverse seepage pressure are the most influentialfactors.A water pressure of 0.4 MPa can double the life of concrete,and the durable life of concrete with a water-cementratio of 0.3 can reach 100 years.
基金supported by the Science and Technology Project of State Grid Jiangsu Electric Power Company(J2023114).
文摘To adress the problems of insufficient consideration of charging pile resource limitations,discrete-time scheduling methods that do not meet the actual demand and insufficient descriptions of peak-shaving response capability in current electric vehicle(EV)opti-mization scheduling,edge intelligence-oriented electric vehicle optimization scheduling and charging station peak-shaving response capability assessment methods are proposed on the basis of the consideration of electric vehicle and charging pile matching.First,an edge-intelligence-oriented electric vehicle regulation frame for charging stations is proposed.Second,continuous time variables are used to represent the available charging periods,establish the charging station controllable EV load model and the future available charging pile mathematical model,and establish the EV and charging pile matching matrix and constraints.Then,with the goal of maximizing the user charging demand and reducing the charging cost,the charging station EV optimal scheduling model is established,and the EV peak response capacity assessment model is further established by considering the EV load shifting constraints under different peak response capacities.Finally,a typical scenario of a real charging station is taken as an example for the analysis of optimal EV scheduling and peak shaving response capacity,and the proposed method is compared with the traditional method to verify the effectiveness and practicality of the proposed method.
文摘Ensuring the reliability of pipe pile designs under earthquake loading necessitates an accurate determination of lateral displacement and bending moment,typically achieved through complex numerical modeling to address the intricacies of soil-pile interaction.Despite recent advancements in machine learning techniques,there is a persistent need to establish data-driven models that can predict these parameters without using numerical simulations due to the difficulties in conducting correct numerical simulations and the need for constitutive modelling parameters that are not readily available.This research presents novel lateral displacement and bending moment predictive models for closed and open-ended pipe piles,employing a Genetic Programming(GP)approach.Utilizing a soil dataset extracted from existing literature,comprising 392 data points for both pile types embedded in cohesionless soil and subjected to earthquake loading,the study intentionally limited input parameters to three features to enhance model simplicity:Standard Penetration Test(SPT)corrected blow count(N60),Peak Ground Acceleration(PGA),and pile slenderness ratio(L/D).Model performance was assessed via coefficient of determination(R^(2)),Root Mean Squared Error(RMSE),and Mean Absolute Error(MAE),with R^(2) values ranging from 0.95 to 0.99 for the training set,and from 0.92 to 0.98 for the testing set,which indicate of high accuracy of prediction.Finally,the study concludes with a sensitivity analysis,evaluating the influence of each input parameter across different pile types.
文摘To investigate the seismic performance of the double-row pre-stressed anchor piles （DRPAPs） on the Yuxi-Mengzi railway, FLAC3D was used to construct a three-dimensional model. Using Koyna earthquake records as input motions, dynamic time-history analyses were carried out. In the analyses, we compared earth pressure on the front and back of the piles and deformation of the piles under different seismic forces with or without anchor cables. With the anchor cable present, the earth pressure on the back of the pile＇s free section increases, but that on the back of the pile＇s anchorage section decreases. Also, with anchor cables, the earth pressure on the front of the upper pile decreases, and that on the back of the lower pile decreases.
基金supported by National Natural Science Foundation of China(No.61903291)Shaanxi Province Key R&D Program(No.2022GY-134)。
文摘A control strategy of repetitive control without inductorance decoupling was proposed to address the problem of high total harmonic distortion(THD)rate of the network-side current caused by the reduced stability of the rectifier module of the DC charging pile under weak grid as well as the dead zone and nonlinearity of switching devices during charging.Firstly,the parallel repetitive control was constructed in the inner current loop,and the proportional-integral(PI)+repetitive controller based on parallel structure was designed.For system compensation,a second-order low-pass filter was selected to correct the system,and the network-side current harmonics were actively suppressed without increasing the filtering device,which effectively improves the quality of grid-connected current.Secondly,based on the synthetic vector method,the controller parameters were designed to realize the elimination of main pole by establishing two synchronous rotation coordinate system vector differential equations,so as to realize the inductanceless decoupling to cope with the influence of network-side inductance fluctuation on the stability of the control system under weak grid.By theoretical analysis and simulation,the proposed control strategy was embedded into the self-developed digital signal processor for the rectifier module of DC charging pile,simulated dynamic and steady-state operation experiments were conducted,and comparative analysis was performed to prove the feasibility of the proposed control strategy.
基金Projects(5147847951322403)supported by the National Natural Science Foundation of China+3 种基金Project(2015CX005)supported by Innovation Driven Plan of Central South University,ChinaProject(14JJ4003)supported by Hunan Provincial Natural Science Foundation,ChinaProject(SKLGP2014K008)supported by Opening Fund of State Key Laboratory of Geohazard Prevention and Geoenvironment Protection,Chengdu University of Technology,ChinaProject(2015CB060200)supported by the National Basic Research Program of China
文摘Response surface method is used to study the reliability analysis of laterally loaded piles in sloping ground. A development load-displacement （p-y） curve for laterally loaded pile response in sloping ground is used to model the pile-soil system, both the pile head displacement and the maximum bending moment of the piles are used as the performance criteria in this study. The reliability analysis method of the laterally loaded pile in sloping ground under the pile head displacement and the maximum bending moment failure modes is proposed, which is in good agreement with the Monte Carlo method. The influences on the probability index of failure by a number of parameters are discussed. It is shown that the variability of pile head displacement increases with the increase in the coefficients of variation of ultimate bearing capacity factor （Npu）, secant elastic modulus at 50%（E50） and level load （H）. A negative correlation between Npu and non-dimensional factor （λ） leads to less spread out probability density function （PDF） of the pile head displacement;in contrast, a positive correlation between Npu andλgives a great variation in the PDF of pile head displacement. As for bearing capacity factor on ground surface （Npo） and λ, both negative and positive correlations between them give a great variation in the PDF of pile head displacement, and a negative correlation will obviously increase the variability of the response.
文摘This paper discusses a new technique to improve soft ground with grouting piles and deep mixing piles. The bearing capacity of composite ground and the stress ratio between piles and soil is discussed by means of the static test. Based on Mindlin solution and Boussinesq solution, the additional stress and settlement of the composite ground are acquired.Compared the practical value with calculation, a better calculating method is confirmed.
文摘The methodology of predicting pile shaft skin ultimate friction has been studied in a systematic way. In the light of that, the analysis of the pile shaft resistance for bored and cast in situ piles in cohesive soils was carried out thoroughly in the basis of field performance data of 10 fully instrumented large diameter bored piles (LDBPs) used as the bridge foundation. The undrained strength index μ in term of cohesive soils was brought forward in allusion to the cohesive soils in the consistence plastic state, and can effectively combine the friction angle and the cohesion of cohesive soils in undrained condition. And that the classical ' α method' was modified much in effect to predict the pile shaft skin friction of LDBPs in cohesive soils. Furthermore, the approach of standard penetration test (SPT) N value used to estimate the pile shaft skin ultimate friction was analyzed, and the calculating formulae were established for LDBPs in clay and silt clay respectively.
基金The National Natural Science Foundation of China(No. 50978112)
文摘The impact of excavation on the reliability of anti- pull piles is studied, and three cases of reliability analysis, named reliability of ultimate limit state （ULS）, reliability of serviceability limit state （SLS） and reliability of system （SYS） are studied. The reduction factor of the pile capacity is used to calculate the reliability indices for the three cases. The ratio ξ of the pile capacity of SLS to the pile capacity of ULS has a significant influence on the reliability indices of SLS and SYS. The mean value μξ of the ratio ξ： is considered as a random variable to study the reliability indices of SLS and SYS. The numerical example demonstrates that the excavation depth and the excavation diameter are proved to have significant influences on the reduction factor of the pile capacity and the reliability indices. The reliability indices decrease with the increase in the excavation depth, and the excavation diameter has a considerable influence on the reliability index when the excavation is relatively deep. In addition, μξ has a significant influence on the reliability indices of SLS and SYS. For a more accurate estimation of μξ, further research should be conducted to study μξ.
文摘Two full-scale experiments using controlled blasting were conducted in the Port of Tokachi on Hokkaido Island, Japan,to assess the behavior of piles and pipelines subjected to lateral spreading.Test specimens were extensively instrumented with strain gauges to measure the distribution of moment during lateral spreading.This allowed us to compute the loading condition,as well as to conduct damage and performance assessments on the piles and pipelines.This paper presents the test results and discussions on the response of single piles and pipelines observed from the full-scale experiments.Based on the test results,it can be concluded that using controlled blasting successfully liquefied the soil,and subsequently induced lateral spreading.The movements of the single pile,as well as the transverse pipelines,were approximately the same as the free field soil movement.Observed moment distribution of the single pile indicated that global translation of the liquefied soil layer provided insignificant force to the pile.In addition,the degree of fixity at the pile tip significantly affected the moment along the pile as well as the pile head displacement.The pile with a higher degree of fixity at the pile tip had smaller pile head displacement but larger maximum moment.
