In order to discuss the buckling stability of super-long rock-socketed filling piles widely used in bridge engineering in soft soil area such as Dongting Lake, the second stability type was adopted instead of traditio...In order to discuss the buckling stability of super-long rock-socketed filling piles widely used in bridge engineering in soft soil area such as Dongting Lake, the second stability type was adopted instead of traditional first type, and a newly invented numerical analysis method, i.e. the element-free Galerkin method (EFGM), was introduced to consider the non-concordant deformation and nonlinearity of the pile-soil interface. Then, based on the nonlinear elastic-ideal plastic pile-soil interface model, a nonlinear iterative algorithm was given to analyze the pile-soil interaction, and a program for buckling analysis of piles by the EFGM (PBAP-EFGM) and arc length method was worked out as well. The application results in an engineering example show that, the shape of pile top load-settlement curve obtained by the program agrees well with the measured one, of which the difference may be caused mainly by those uncertain factors such as possible initial defects of pile shaft and the eccentric loading during the test process. However, the calculated critical load is very close with the measured ultimate load of the test pile, and the corresponding relative error is only 5.6%, far better than the calculated values by linear and nonlinear incremental buckling analysis (with a greater relative error of 37.0% and 15.4% respectively), which also verifies the rationality and feasibility of the present method.展开更多
A centrifuge modeling test and a three-dimensional finite element analysis（FEA）of super-long rock-socketed bored pile groups of the Tianxingzhou Bridge are proposed.Based on the similarity theory,different prototypi...A centrifuge modeling test and a three-dimensional finite element analysis（FEA）of super-long rock-socketed bored pile groups of the Tianxingzhou Bridge are proposed.Based on the similarity theory,different prototypical materials are simulated using different indicators in the centrifuge model.The silver sand,the shaft and the pile cap are simulated according to the natural density,the compressive stiffness and the bending stiffness,respectively.The finite element method（FEM）is implemented and analyzed in ANSYS,in which the stress field during the undisturbed soil stage,the boring stage,the concrete-casting stage and the curing stage are discussed in detail.Comparisons in terms of load-settlement,shaft axial force distribution and lateral friction between the numerical results and the test data are carried out to investigate the bearing behaviors of super-long rock-socketed bored pile groups under loading and unloading conditions.Results show that there is a good agreement between the centrifuge modeling tests and the FEM.In addition,the load distribution at the pile top is complicated,which is related to the stiffness of the cap,the corresponding assumptions and the analysis method.The shaft axial force first increases slightly with depth then decreases sharply,and the rate of decrease in rock is greater than that in sand and soil.展开更多
In order to study the mechanism of bearing behavior at the tip of a pile embedded in rock, the generalized nonlinear unified strength criterion and slip line principle for resolving the differential equation systems w...In order to study the mechanism of bearing behavior at the tip of a pile embedded in rock, the generalized nonlinear unified strength criterion and slip line principle for resolving the differential equation systems which govern the stress field were applied to derive the ultimate end beating capacity based on some reasonable hypothesis and failure plane model. Both numerical simulation and test results were compared with the theoretic solution. The results show good consistency with each other and verify the validity of the present approach. The depth effect with respective to embedment ratio and other influence factors like geological strength index, intermediate principal stress, overburden factor, and damage on end bearing capacity were discussed in the analytical solution. The results show that the proposed yield criterion can be much better for investigating the ultimate end bearing performance of rock-socketed pile. The end bearing capacity increases with embedment ratio and the increasing degree is influenced intensely by the above parameters. Furthermore, ignoring intermediate stress effect would underestimate the strength properties of the rock material and lead to a very conservative estimation value.展开更多
Based on the fictitious soil pile model, the effect of sediment on the vertical dynamic impedance of rock-socketed pile with large diameter was theoretically studied by means of Laplace transform technique and impedan...Based on the fictitious soil pile model, the effect of sediment on the vertical dynamic impedance of rock-socketed pile with large diameter was theoretically studied by means of Laplace transform technique and impedance function transfer method. Firstly, the sediment under rock-socketed pile was assumed to be fictitious soil pile with the same sectional area. The Rayleigh-Love rode model was used to simulate the rock-socketed pile and the fictitious soil pile with the consideration of the lateral inertial effect of large-diameter pile. The layered surrounding soils and bedrock were modeled by the plane strain model. Then, by virtue of the initial conditions and boundary conditions of the soil pile system, the analytical solution of the vertical dynamic impedance at the head of rock-socketed pile was derived for the arbitrary excitation acting on the pile head. Lastly, based on the presented analytical solution, the effect of sediment properties, bedrock property and lateral inertial effect on the vertical dynamic impedance at rock-socketed pile head were investigated in detail. It is shown that the sediment properties have significant effect on the vertical dynamic impedance at the rock-socketed pile head. The ability of soil-pile system to resist dynamic vertical deformation is weakened with the increase of sediment thickness, but amplified with the increase of shear wave velocity of sediment. The ability of soil pile system to resist dynamic vertical deformation is amplified with the bedrock property improving, but the ability of soil-pile system to resist vertical vibration is weakened with the improvement of bedrock property.展开更多
Spiral pile foundations,as a promising type of foundation,are of significant importance for the development of offshore wind energy,particularly as it moves toward deeper waters.This study conducted a physical experim...Spiral pile foundations,as a promising type of foundation,are of significant importance for the development of offshore wind energy,particularly as it moves toward deeper waters.This study conducted a physical experiment on a three-spiral-pile jacket foundation under deep-buried sandy soil conditions.During the experiment,horizontal displacement was applied to the structure to thoroughly investigate the bearing characteristics of the three-spiral-pile jacket foundation.This study also focused on analyzing the bearing mechanisms of conventional piles compared with spiral piles with different numbers of blades.Three different working conditions were set up and compared,and key data,such as the horizontal bearing capacity,pile shaft axial force,and spiral blade soil pressure,were measured and analyzed.The results show the distinct impacts of the spiral blades on the compressed and tensioned sides of the foundation.Specifically,on the compressed side,the spiral blades effectively enhance the restraint of the soil on the pile foundation,whereas on the tensioned side,an excessive number of spiral blades can negatively affect the structural tensile performance to some extent.This study also emphasizes that the addition of blades to the side of a single pile is the most effective method for increasing the bearing capacity of the foundation.This research aims to provide design insights into improving the bearing capacity of the foundation.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
In the past two decades, numerous large-diameter rock-socketed piles were constructed in China to support foundations of skyscrapers, great bridges or to retain soil in potential geological hazard areas. However, dril...In the past two decades, numerous large-diameter rock-socketed piles were constructed in China to support foundations of skyscrapers, great bridges or to retain soil in potential geological hazard areas. However, drilling large-diameter rock-socketed pile holes with conventional drilling method such as rotary drilling or cable tool drilling is time-consuming and the cost is usually very high. In order to drill large-diameter rocksocketed pile holes faster at relatively low cost, the FGC15A large-diameter DTH air hammer drilling system was developed in 1987 and was given the second-clasa award by Ministry of Geology and Mineral Resources in 1991. Since it was innovated the drilling system has been used in more than twenty important and tough pro- jects on land, and wonderful results were acquired. At the same time the large-diameter DTH air hammer drilling system was improved continuously. The FGC15D is the latest version of the technique.展开更多
Reliability analysis of soil slopes under rainfall is an important task for landslide risk assessment.Previous studies rarely contribute to the probabilistic analysis of slope stability under rainfall with reinforceme...Reliability analysis of soil slopes under rainfall is an important task for landslide risk assessment.Previous studies rarely contribute to the probabilistic analysis of slope stability under rainfall with reinforcement.A new method is suggested for reliability analysis of soil slopes stabilized with piles under rainfall.First,an efficient numerical model is exploited for slope stability analysis,where two types of slope failure modes,i.e.,plastic flow and local failure are considered.To address the blocking effect of piles during seepage analysis,the equivalent hydraulic conductivity of the pile area is estimated according to the effective medium theory.The stabilizing force of piles is investigated by an analytical approach.For saving computational effort,the response surface is established based on a multi-class classification model to predict two types of slope failure modes.Finally,uncertainties in soil parameters and rainfall events are both modelled,and the failure probability of soil slopes within a given time period is assessed through Monte Carlo simulation.An illustrative example is used to demonstrate the performance of the suggested method.It is found that the slope is mainly controlled by local failure.As the pile spacing increases,the likelihood of plastic flow significantly increases.As the piles are located near the slope crest,plastic flow is effectively prevented and the slope is better stabilized against rainfall.If rainfall uncertainties are not considered,the slope failure probability is significantly overestimated.Overall,this study can provide a useful guidance for the design of pile-stabilized slopes against rainfall infiltration.展开更多
With the increasing construction of port facilities,cross-sea bridges,and offshore engineering projects,uplift piles embedded in marine sedimentary soft soil are becoming increasingly necessary.The load-displacement c...With the increasing construction of port facilities,cross-sea bridges,and offshore engineering projects,uplift piles embedded in marine sedimentary soft soil are becoming increasingly necessary.The load-displacement curve of uplift piles is crucial for evaluating their uplift bearing characteristics,which facilitates the risk evaluation,design,and construction of large infrastructural supports.In this study,a load-displacement curve model based on piezocone penetration test(CPTU)data is proposed via the load transfer method.Experimental tests are conducted to analyze the uplift bearing characteristics and establish a correlation between the proposed model and CPTU data.The results of the proposed load-displacement curve are compared with the results from numerical simulations and those calculated by previous methods.The results show that the proposed curves appropriately evaluated the uplift bearing characteristics and improved the accuracy in comparison with previous methods.展开更多
This study investigates the load-bearing capacity of open-ended pipe piles in sandy soil, with a specific focus on the impact of soil plug constraints at four levels(no plug, 25% plug, 50% plug, and full plug). Levera...This study investigates the load-bearing capacity of open-ended pipe piles in sandy soil, with a specific focus on the impact of soil plug constraints at four levels(no plug, 25% plug, 50% plug, and full plug). Leveraging a dataset comprising open-ended pipe piles with varying geometrical and geotechnical properties, this research employs shallow neural network(SNN) and deep neural network(DNN) models to predict plugging conditions for both driven and pressed installation types. This paper underscores the importance of key parameters such as the settlement value,applied load, installation type, and soil configuration(loose, medium, and dense) in accurately predicting pile settlement. These findings offer valuable insights for optimizing pile design and construction in geotechnical engineering,addressing a longstanding challenge in the field. The study demonstrates the potential of the SNN and DNN models in precisely identifying plugging conditions before pile driving, with the SNN achieving R2 values ranging from0.444 to 0.711 and RMSPE values ranging from 24.621% to 48.663%, whereas the DNN exhibits superior performance, with R2 values ranging from 0.815 to 0.942 and RMSPE values ranging from 4.419% to 10.325%. These results have significant implications for enhancing construction practices and reducing uncertainties associated with pile foundation projects in addition to leveraging artificial intelligence tools to avoid long experimental procedures.展开更多
Seismic-induced landslides critically threaten infrastructure and human safety,especially in sandy slopes where conventional stabilization methods often fail under dynamic loading.This study evaluates circular open-en...Seismic-induced landslides critically threaten infrastructure and human safety,especially in sandy slopes where conventional stabilization methods often fail under dynamic loading.This study evaluates circular open-ended anti-slide pipe piles embedded in a two-layer sandy slope with differing geotechnical properties.Ten physical models,including five freefield and five pile-reinforced slopes,were tested on a shaking table.Key seismic responses—acceleration,soil displacement,and bending moments—were monitored using accelerometers,strain gauges,and Digital Image Correlation(DIC).Complementary numerical simulations using Abaqus with a Mohr–Coulomb model validated experimental results.Soil displacement in free-field models under 0.25g shaking was about 3.5 times greater than in reinforced slopes.Bending moments increased with seismic intensity,peaking at depths around five times the pile diameter.Limitations including simplified two-layer soil representation,idealized seismic inputs,and boundary effects inherent to laboratory models restrict direct field application but enable controlled analysis.By combining physical experiments with numerical modeling,the study provides a robust and validated framework for seismic slope stabilization.This integrated approach enhances understanding of soil–pile interaction under seismic loads and offers targeted insights for developing safer and more reliable geotechnical design strategies in earthquake-prone areas.展开更多
The behavior of rigid piles in sandy soils under one-way cyclic oblique tensile loading represents a critical design consideration for floating renewable devices.These piles,when moored with catenary or taut moorings,...The behavior of rigid piles in sandy soils under one-way cyclic oblique tensile loading represents a critical design consideration for floating renewable devices.These piles,when moored with catenary or taut moorings,experience one-way cyclic tensile loads at inclinations ranging from 0°(horizontal)to 90°(vertical).However,the combined effects of cyclic loading and load inclination remain inadequately understood.This study presents findings from centrifuge tests conducted on rough rigid piles installed in dense sand samples.The results demonstrate that load inclinations significantly influence both cyclic response and ultimate capacity of the piles.Based on the observed cyclic response characteristics,the vertical cyclic load amplitude should not exceed 25%of the ultimate bearing capacity to maintain pile stability.A power expression(with exponent m values ranging from 0.055 to 0.065)is proposed for predicting cumulative pile displacement under unidirectional cyclic loading at inclinations from 0°to 60°.The cyclic response exhibits reduced sensitivity to horizontal cyclic load magnitude,with m-value increasing from 0.06 to 0.14 as load magnitude increases from 0.3 to 0.9.For piles maintaining stability under oblique cyclic loading,the average normalized secant stiffness exceeds 1 and increases with decreasing inclination,indicating enhanced pile stiffness under cyclic loading.For load inclinations below 30°,pile stiffness can be determined using logarithmic function.展开更多
Laterally loaded piles,which are commonly used in sandy stratum foundations,are particularly susceptible to necking defects during cast-in-place installation due to borehole collapse risks.These construction-induced g...Laterally loaded piles,which are commonly used in sandy stratum foundations,are particularly susceptible to necking defects during cast-in-place installation due to borehole collapse risks.These construction-induced geometric imperfections substantially compromise pile safety under lateral loading conditions.To address this critical design challenge,we develop a reliability-based multi-objective optimization framework that simultaneously accounts for structural safety,construction economy,and design robustness.The proposed methodology integrates the p-y curve(where p is the soil pressure per unit length,and y is the lateral deflection of the pile)analysis with stochastic modeling,enabling efficient evaluation of pile performance considering uncertainties in soil parameters and depth and size variations of necking defects.A systematic design framework is implemented and validated through experimental case studies,successfully generating optimal designs along the Pareto front.The identified knee-point configurations serve as practical compromise solutions for engineering decisions.Parametric investigations further elucidate the influence of necking defect depth and sand friction angle variations on optimal design outcomes,offering insights into risk mitigation for pile construction.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
Long steel piles with large diameters have been more widely used in the field of ocean engineering. Owing to the pile with a large diameter, soil plug development during pile driving has great influences on pile drive...Long steel piles with large diameters have been more widely used in the field of ocean engineering. Owing to the pile with a large diameter, soil plug development during pile driving has great influences on pile driveability and bearing capacity. The response of soil plug developed inside the open-ended pipe pile during the dynamic condition of pile-driving is different from the response under the static condition of loading during service. This paper addresses the former aspect. A numerical procedure for soil plug effect prediction and pile driveabihty analysis is proposed and described. By taking into consideration of the pile dimension effect on side and tip resistance, this approach introduces a dimensional coefficient to the conventional static eqnihbrium equations for the plug differential unit and proposes an improved static equity method for the plug effect prediction. At the same time, this approach introduces a simplified model by use of one-dimensional stress wave equation to simulate the interaction between soil plug and pile inner wall. The proposed approach has been applied in practical engineering analyses. Results show that the calculated plug effect and pile driveabihty based on the proposed approach agree well with the observed data.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
基金Project(50378036) supported by the National Natural Science Foundation of China
文摘In order to discuss the buckling stability of super-long rock-socketed filling piles widely used in bridge engineering in soft soil area such as Dongting Lake, the second stability type was adopted instead of traditional first type, and a newly invented numerical analysis method, i.e. the element-free Galerkin method (EFGM), was introduced to consider the non-concordant deformation and nonlinearity of the pile-soil interface. Then, based on the nonlinear elastic-ideal plastic pile-soil interface model, a nonlinear iterative algorithm was given to analyze the pile-soil interaction, and a program for buckling analysis of piles by the EFGM (PBAP-EFGM) and arc length method was worked out as well. The application results in an engineering example show that, the shape of pile top load-settlement curve obtained by the program agrees well with the measured one, of which the difference may be caused mainly by those uncertain factors such as possible initial defects of pile shaft and the eccentric loading during the test process. However, the calculated critical load is very close with the measured ultimate load of the test pile, and the corresponding relative error is only 5.6%, far better than the calculated values by linear and nonlinear incremental buckling analysis (with a greater relative error of 37.0% and 15.4% respectively), which also verifies the rationality and feasibility of the present method.
基金The Natural Science Foundation of Hubei Province(No.2007ABA094)
文摘A centrifuge modeling test and a three-dimensional finite element analysis（FEA）of super-long rock-socketed bored pile groups of the Tianxingzhou Bridge are proposed.Based on the similarity theory,different prototypical materials are simulated using different indicators in the centrifuge model.The silver sand,the shaft and the pile cap are simulated according to the natural density,the compressive stiffness and the bending stiffness,respectively.The finite element method（FEM）is implemented and analyzed in ANSYS,in which the stress field during the undisturbed soil stage,the boring stage,the concrete-casting stage and the curing stage are discussed in detail.Comparisons in terms of load-settlement,shaft axial force distribution and lateral friction between the numerical results and the test data are carried out to investigate the bearing behaviors of super-long rock-socketed bored pile groups under loading and unloading conditions.Results show that there is a good agreement between the centrifuge modeling tests and the FEM.In addition,the load distribution at the pile top is complicated,which is related to the stiffness of the cap,the corresponding assumptions and the analysis method.The shaft axial force first increases slightly with depth then decreases sharply,and the rate of decrease in rock is greater than that in sand and soil.
基金Project(2007AA11Z134) supported by the National High-tech Research and Development Program of ChinaProject(10JJ4035) supported by Hunan Provincial Natural Science Foundation of ChinaProject(04SK2008) supported by Hunan Provincial Science and Technology Department,China
文摘In order to study the mechanism of bearing behavior at the tip of a pile embedded in rock, the generalized nonlinear unified strength criterion and slip line principle for resolving the differential equation systems which govern the stress field were applied to derive the ultimate end beating capacity based on some reasonable hypothesis and failure plane model. Both numerical simulation and test results were compared with the theoretic solution. The results show good consistency with each other and verify the validity of the present approach. The depth effect with respective to embedment ratio and other influence factors like geological strength index, intermediate principal stress, overburden factor, and damage on end bearing capacity were discussed in the analytical solution. The results show that the proposed yield criterion can be much better for investigating the ultimate end bearing performance of rock-socketed pile. The end bearing capacity increases with embedment ratio and the increasing degree is influenced intensely by the above parameters. Furthermore, ignoring intermediate stress effect would underestimate the strength properties of the rock material and lead to a very conservative estimation value.
基金Projects(51109084/E09070151308234/E08061) supported by the National Natural Science Foundation of China+1 种基金Project(2013J05079) supported by the Natural Science Foundation of Fujian Province,ChinaProject(Z012002) supported by the Open Research Fund of State Key Laboratory of Geomechanics and Geotechnical Engineering(Institute of Rock and Soil Mechanics,Chinese Academy of Sciences),China
文摘Based on the fictitious soil pile model, the effect of sediment on the vertical dynamic impedance of rock-socketed pile with large diameter was theoretically studied by means of Laplace transform technique and impedance function transfer method. Firstly, the sediment under rock-socketed pile was assumed to be fictitious soil pile with the same sectional area. The Rayleigh-Love rode model was used to simulate the rock-socketed pile and the fictitious soil pile with the consideration of the lateral inertial effect of large-diameter pile. The layered surrounding soils and bedrock were modeled by the plane strain model. Then, by virtue of the initial conditions and boundary conditions of the soil pile system, the analytical solution of the vertical dynamic impedance at the head of rock-socketed pile was derived for the arbitrary excitation acting on the pile head. Lastly, based on the presented analytical solution, the effect of sediment properties, bedrock property and lateral inertial effect on the vertical dynamic impedance at rock-socketed pile head were investigated in detail. It is shown that the sediment properties have significant effect on the vertical dynamic impedance at the rock-socketed pile head. The ability of soil-pile system to resist dynamic vertical deformation is weakened with the increase of sediment thickness, but amplified with the increase of shear wave velocity of sediment. The ability of soil pile system to resist dynamic vertical deformation is amplified with the bedrock property improving, but the ability of soil-pile system to resist vertical vibration is weakened with the improvement of bedrock property.
基金The National Natural Science Foundation of China(No.52171274).
文摘Spiral pile foundations,as a promising type of foundation,are of significant importance for the development of offshore wind energy,particularly as it moves toward deeper waters.This study conducted a physical experiment on a three-spiral-pile jacket foundation under deep-buried sandy soil conditions.During the experiment,horizontal displacement was applied to the structure to thoroughly investigate the bearing characteristics of the three-spiral-pile jacket foundation.This study also focused on analyzing the bearing mechanisms of conventional piles compared with spiral piles with different numbers of blades.Three different working conditions were set up and compared,and key data,such as the horizontal bearing capacity,pile shaft axial force,and spiral blade soil pressure,were measured and analyzed.The results show the distinct impacts of the spiral blades on the compressed and tensioned sides of the foundation.Specifically,on the compressed side,the spiral blades effectively enhance the restraint of the soil on the pile foundation,whereas on the tensioned side,an excessive number of spiral blades can negatively affect the structural tensile performance to some extent.This study also emphasizes that the addition of blades to the side of a single pile is the most effective method for increasing the bearing capacity of the foundation.This research aims to provide design insights into improving the bearing capacity of the foundation.
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In the past two decades, numerous large-diameter rock-socketed piles were constructed in China to support foundations of skyscrapers, great bridges or to retain soil in potential geological hazard areas. However, drilling large-diameter rock-socketed pile holes with conventional drilling method such as rotary drilling or cable tool drilling is time-consuming and the cost is usually very high. In order to drill large-diameter rocksocketed pile holes faster at relatively low cost, the FGC15A large-diameter DTH air hammer drilling system was developed in 1987 and was given the second-clasa award by Ministry of Geology and Mineral Resources in 1991. Since it was innovated the drilling system has been used in more than twenty important and tough pro- jects on land, and wonderful results were acquired. At the same time the large-diameter DTH air hammer drilling system was improved continuously. The FGC15D is the latest version of the technique.
基金supported by the National Key Research and Development Program of China(Grant No.2021YFB2600504)the National Natural Science Foundation of China(Grant No.42072302)the Postdoctoral Fellowship Program of CPSF(Grant No.GZB20240533).
文摘Reliability analysis of soil slopes under rainfall is an important task for landslide risk assessment.Previous studies rarely contribute to the probabilistic analysis of slope stability under rainfall with reinforcement.A new method is suggested for reliability analysis of soil slopes stabilized with piles under rainfall.First,an efficient numerical model is exploited for slope stability analysis,where two types of slope failure modes,i.e.,plastic flow and local failure are considered.To address the blocking effect of piles during seepage analysis,the equivalent hydraulic conductivity of the pile area is estimated according to the effective medium theory.The stabilizing force of piles is investigated by an analytical approach.For saving computational effort,the response surface is established based on a multi-class classification model to predict two types of slope failure modes.Finally,uncertainties in soil parameters and rainfall events are both modelled,and the failure probability of soil slopes within a given time period is assessed through Monte Carlo simulation.An illustrative example is used to demonstrate the performance of the suggested method.It is found that the slope is mainly controlled by local failure.As the pile spacing increases,the likelihood of plastic flow significantly increases.As the piles are located near the slope crest,plastic flow is effectively prevented and the slope is better stabilized against rainfall.If rainfall uncertainties are not considered,the slope failure probability is significantly overestimated.Overall,this study can provide a useful guidance for the design of pile-stabilized slopes against rainfall infiltration.
基金supported by the China Postdoctoral Science Foundation(Grant No.2024M760734)National Science Fund for Distinguished Young Scholars(Grant No.42225206)the National Natural Science Foundation of China(Grant Nos.41877231 and 42072299).
文摘With the increasing construction of port facilities,cross-sea bridges,and offshore engineering projects,uplift piles embedded in marine sedimentary soft soil are becoming increasingly necessary.The load-displacement curve of uplift piles is crucial for evaluating their uplift bearing characteristics,which facilitates the risk evaluation,design,and construction of large infrastructural supports.In this study,a load-displacement curve model based on piezocone penetration test(CPTU)data is proposed via the load transfer method.Experimental tests are conducted to analyze the uplift bearing characteristics and establish a correlation between the proposed model and CPTU data.The results of the proposed load-displacement curve are compared with the results from numerical simulations and those calculated by previous methods.The results show that the proposed curves appropriately evaluated the uplift bearing characteristics and improved the accuracy in comparison with previous methods.
文摘This study investigates the load-bearing capacity of open-ended pipe piles in sandy soil, with a specific focus on the impact of soil plug constraints at four levels(no plug, 25% plug, 50% plug, and full plug). Leveraging a dataset comprising open-ended pipe piles with varying geometrical and geotechnical properties, this research employs shallow neural network(SNN) and deep neural network(DNN) models to predict plugging conditions for both driven and pressed installation types. This paper underscores the importance of key parameters such as the settlement value,applied load, installation type, and soil configuration(loose, medium, and dense) in accurately predicting pile settlement. These findings offer valuable insights for optimizing pile design and construction in geotechnical engineering,addressing a longstanding challenge in the field. The study demonstrates the potential of the SNN and DNN models in precisely identifying plugging conditions before pile driving, with the SNN achieving R2 values ranging from0.444 to 0.711 and RMSPE values ranging from 24.621% to 48.663%, whereas the DNN exhibits superior performance, with R2 values ranging from 0.815 to 0.942 and RMSPE values ranging from 4.419% to 10.325%. These results have significant implications for enhancing construction practices and reducing uncertainties associated with pile foundation projects in addition to leveraging artificial intelligence tools to avoid long experimental procedures.
基金the support from the Outstanding Youth Foundation of Shandong Province(ZR2021YQ31)the National Natural Science Foundation of China(42277135)+5 种基金National Foreign Experts Individual Program(Category Y)(Grant No.Y20240084)the National Natural Science Foundation of China Joint Fund Key Project(U2006225)Special Fund for Taishan Scholar Projectthe Youth Project of Open Funding from Engineering Research Center of Concrete Technology under Marine Environment,Ministry of Education(Grant No.TMduracon202217)the funding from Key Laboratory of Ministry of Education for Coastal Disaster and Protection,Hohai University(Grant No.202206)Shandong Provincial Overseas High-Level Talent Workstation,China。
文摘Seismic-induced landslides critically threaten infrastructure and human safety,especially in sandy slopes where conventional stabilization methods often fail under dynamic loading.This study evaluates circular open-ended anti-slide pipe piles embedded in a two-layer sandy slope with differing geotechnical properties.Ten physical models,including five freefield and five pile-reinforced slopes,were tested on a shaking table.Key seismic responses—acceleration,soil displacement,and bending moments—were monitored using accelerometers,strain gauges,and Digital Image Correlation(DIC).Complementary numerical simulations using Abaqus with a Mohr–Coulomb model validated experimental results.Soil displacement in free-field models under 0.25g shaking was about 3.5 times greater than in reinforced slopes.Bending moments increased with seismic intensity,peaking at depths around five times the pile diameter.Limitations including simplified two-layer soil representation,idealized seismic inputs,and boundary effects inherent to laboratory models restrict direct field application but enable controlled analysis.By combining physical experiments with numerical modeling,the study provides a robust and validated framework for seismic slope stabilization.This integrated approach enhances understanding of soil–pile interaction under seismic loads and offers targeted insights for developing safer and more reliable geotechnical design strategies in earthquake-prone areas.
基金supported by Fundamental Research Funds for the Central Universities(Grant No.B200202050)Open Funds of Key Laboratory of Navigation Structure。
文摘The behavior of rigid piles in sandy soils under one-way cyclic oblique tensile loading represents a critical design consideration for floating renewable devices.These piles,when moored with catenary or taut moorings,experience one-way cyclic tensile loads at inclinations ranging from 0°(horizontal)to 90°(vertical).However,the combined effects of cyclic loading and load inclination remain inadequately understood.This study presents findings from centrifuge tests conducted on rough rigid piles installed in dense sand samples.The results demonstrate that load inclinations significantly influence both cyclic response and ultimate capacity of the piles.Based on the observed cyclic response characteristics,the vertical cyclic load amplitude should not exceed 25%of the ultimate bearing capacity to maintain pile stability.A power expression(with exponent m values ranging from 0.055 to 0.065)is proposed for predicting cumulative pile displacement under unidirectional cyclic loading at inclinations from 0°to 60°.The cyclic response exhibits reduced sensitivity to horizontal cyclic load magnitude,with m-value increasing from 0.06 to 0.14 as load magnitude increases from 0.3 to 0.9.For piles maintaining stability under oblique cyclic loading,the average normalized secant stiffness exceeds 1 and increases with decreasing inclination,indicating enhanced pile stiffness under cyclic loading.For load inclinations below 30°,pile stiffness can be determined using logarithmic function.
基金supported by the Fundamental Research Funds for the Central Universities of China(No.226-2024-00197)the National Natural Science Foundation of China(No.42277129)+1 种基金the Key R&D Project of Zhejiang Province(No.2021C03159)the Natural Science Foundation of Zhejiang Province(No.LR24E080004),China.
文摘Laterally loaded piles,which are commonly used in sandy stratum foundations,are particularly susceptible to necking defects during cast-in-place installation due to borehole collapse risks.These construction-induced geometric imperfections substantially compromise pile safety under lateral loading conditions.To address this critical design challenge,we develop a reliability-based multi-objective optimization framework that simultaneously accounts for structural safety,construction economy,and design robustness.The proposed methodology integrates the p-y curve(where p is the soil pressure per unit length,and y is the lateral deflection of the pile)analysis with stochastic modeling,enabling efficient evaluation of pile performance considering uncertainties in soil parameters and depth and size variations of necking defects.A systematic design framework is implemented and validated through experimental case studies,successfully generating optimal designs along the Pareto front.The identified knee-point configurations serve as practical compromise solutions for engineering decisions.Parametric investigations further elucidate the influence of necking defect depth and sand friction angle variations on optimal design outcomes,offering insights into risk mitigation for pile construction.
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.
基金supported by the National Natural Science Foundation of China (Grant No.50309009)the National High Technology Research and Development Program of China(863 Program,Grant No.2004AA616100)
文摘Long steel piles with large diameters have been more widely used in the field of ocean engineering. Owing to the pile with a large diameter, soil plug development during pile driving has great influences on pile driveability and bearing capacity. The response of soil plug developed inside the open-ended pipe pile during the dynamic condition of pile-driving is different from the response under the static condition of loading during service. This paper addresses the former aspect. A numerical procedure for soil plug effect prediction and pile driveabihty analysis is proposed and described. By taking into consideration of the pile dimension effect on side and tip resistance, this approach introduces a dimensional coefficient to the conventional static eqnihbrium equations for the plug differential unit and proposes an improved static equity method for the plug effect prediction. At the same time, this approach introduces a simplified model by use of one-dimensional stress wave equation to simulate the interaction between soil plug and pile inner wall. The proposed approach has been applied in practical engineering analyses. Results show that the calculated plug effect and pile driveabihty based on the proposed approach agree well with the observed data.
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.
