Monocolumn composite bucket foundation is a new type of offshore wind energy foundation.Its bearing characteristics under shallow bedrock conditions and complex geological conditions have not been extensively studied....Monocolumn composite bucket foundation is a new type of offshore wind energy foundation.Its bearing characteristics under shallow bedrock conditions and complex geological conditions have not been extensively studied.Therefore,to analyze its bearing characteristics under complex conditions-such as silty soil,chalky soil,and shallow bedrock-this paper employs finite element software to establish various soil combination scenarios.The load-displacement curves of the foundations under these scenarios are calculated to subsequently evaluate the horizontal ultimate bearing capacity.This study investigates the effects of shallow bedrock depth,the type of soil above the bedrock,the thickness of layered soil,and the quality of layered soil on the bearing characteristics of the monocolumn composite bucket foundation.Based on the principle of single-variable control,the ultimate bearing capacity characteristics of the foundation under different conditions are compared.The distribution of soil pressure inside and outside the bucket wall on the compressed side of the foundation,along with the plastic strain of the soil at the base of the foundation,is also analyzed.In conclusion,shallow bedrock somewhat reduces foundation bearing capacity.Under shallow bedrock conditions,the degree of influence on foundation bearing capacity characteristics can considerably vary on different upper soils.The thickness of each soil layer and the depth to bedrock in stratified soils also affect the bearing capacity of the foundation.The findings of this paper provide a theoretical reference for related foundation design and construction.In practice,the bearing performance of the foundation can be enhanced by improvingthe soil quality in the bucket,adjusting the penetration depth,adjusting the percentage of different types of soil layers in the bucket,and applying other technical construction methods.展开更多
The main objective of this study is to investigate the buckling analysis of CCSs reinforced by CNTs subjected to combined loading of hydrostatic pressure and axial compression resting on the twoparameter elastic found...The main objective of this study is to investigate the buckling analysis of CCSs reinforced by CNTs subjected to combined loading of hydrostatic pressure and axial compression resting on the twoparameter elastic foundation(T-P-EF).It is one of the first attempts to derive the governing equations of the CCSs reinforced with CNTs,based on a generalized first-order shear deformation shell theory(FSDST)which includes shell-foundation interaction.By adopting the extended mixing rule,the effective material properties of CCSs reinforced by CNTs with linear distributions are approximated by introducing some efficiency parameters.Three carbon nanotube distribution in the matrix,i.e.uniform distribution(U)and V and X-types linear distribution are taken into account.The stability equations are solved by using the Galerkin procedure to determine the combined buckling loads(CBLs)of the structure selected here.The numerical illustrations cover CBLs characteristics of CCSs reinforced by CNTs in the presence of the T-P-EF.Finally,a parametric study is carried out to study the influences of the foundation parameters,the volume fraction of carbon nanotubes and the types of reinforcement on the CBLs.展开更多
Under the combination of currents and waves, seabed scour occurs around offshore wind turbine foundations, which affects the stability and safe operation of offshore wind turbines. In this study, physical model experi...Under the combination of currents and waves, seabed scour occurs around offshore wind turbine foundations, which affects the stability and safe operation of offshore wind turbines. In this study, physical model experiments under unidirectional flow, bidirectional flow, and wave-current interactions with different flow directions around the pile group foundation were first conducted to investigate the development of scour around the pile group foundation.Additionally, a three-dimensional scour numerical model was established via the open-source software REEF3D to simulate the flow field and scour around the prototype-scale foundation. The impact of flow on scour was discussed.Under unidirectional flow, scour equilibrium was reached more quickly, with the maximum scour depth reaching approximately 1.2 times the pile diameter and the extent of the scour hole spanning about 4.9 times the pile diameter.Compared with those under unidirectional flow, the scour depths under combinations of currents and waves, as well as bidirectional flow, were slightly smaller. However, the morphology of scour holes was more uniform and symmetrical. The numerical simulation results show good agreement with the experimental data, demonstrating the impact of varying flow directions on the velocity distribution around the foundation, the morphology of scour holes, and the location of the maximum scour depth.展开更多
Two fundamental solutions for bending problem of Reissner's plates on twoparameter foundation are derived by means of Fouier integral transformation of generalized function in this paper.On the basis of virtual wo...Two fundamental solutions for bending problem of Reissner's plates on twoparameter foundation are derived by means of Fouier integral transformation of generalized function in this paper.On the basis of virtual work principles, three boundary integral equations which fit for arbitrary shapes, loads and boundary conditions of thick plates are presented according to Hu Haichang's theory about Reissner's plates. It provides the fundamental theories for the application of BEM. A numerical example is given for clamped, simply supported and free boundary conditions. The results obtained are satisfactory as compared with the analytical methods.展开更多
The problems noted in the structures built on wooden foundation piles in a lake environment required various works to strengthen over time.This work mainly consists of the recovery of the foundation mass by micropiles...The problems noted in the structures built on wooden foundation piles in a lake environment required various works to strengthen over time.This work mainly consists of the recovery of the foundation mass by micropiles due to the increase in loads on the structures,or the recovery of the foundation mass by injection,which is carried out when voids form between the ground and the wooden foundation elements.The high cost of foundation reinforcement methods led the National Agency for the Development of Tourist Heritage in Benin(ANPT)to replace the wooden foundation piles with reinforced concrete piles in the implementation of the project“reinventing the lakeside city of Ganvié”.This article presents an artisanal technology for the creation of reinforced concrete foundation piles in a lake environment.On-site examples made it possible to evaluate the performance of this artisanal implementation technique.The installation of these piles is carried out following manual drilling,followed by the installation of reinforcement and the pouring of concrete on site.The implementation of reinforced concrete foundation piles in place of the wooden ones studied in this article only impacted the infrastructure of the homes of the lakeside town of Ganviébut not the superstructure,which preserved the old traditional wooden architecture and thatched roofs.Thus,the ambition to move this city of Ganviéfrom the stage of a lake village to that of a floating city is very successful.This will contribute to improving the environment and living conditions of the populations and will promote economic development through tourism.展开更多
Transcritical and supercritical fluids widely exist in aerospace propulsion systems,such as the coolant flow in the regenerative cooling channels of scramjet engines.To numerically simulate the coolant flow,we must ad...Transcritical and supercritical fluids widely exist in aerospace propulsion systems,such as the coolant flow in the regenerative cooling channels of scramjet engines.To numerically simulate the coolant flow,we must address the challenges in solving Riemann problems(RPs)for real fluids under complex flow conditions.In this study,an exact numerical solution for the one-dimensional RP of two-parameter fluids is developed.Due to the comprehensive resolution of fluid thermodynamics,the proposed solution framework is suitable for all forms of the two-parameter equation of state(EoS).The pressure splitting method is introduced to enable parallel calculation of RPs across multiple grid points.Theoretical analysis demonstrates the isentropic nature of weak waves in two-parameter fluids,ensuring that the same mathematical properties as ideal gas could be applied in Newton's iteration.A series of numerical cases validate the effectiveness of the proposed method.A comparative analysis is conducted on the exact Riemann solutions for the real fluid EoS,the ideal gas EoS,and the improved ideal gas EoS under supercritical and transcritical conditions.The results indicate that the improved one produces smaller errors in the calculation of momentum and energy fluxes.展开更多
The coastal region of Fujian contains numerous existing stone masonry structures,many of which are constructed on soft soil sites.Previous studies have shown that the soil-structure interaction(SSI)effect on soft soil...The coastal region of Fujian contains numerous existing stone masonry structures,many of which are constructed on soft soil sites.Previous studies have shown that the soil-structure interaction(SSI)effect on soft soil foundations can prolong the structure's natural vibration period and enhance its seismic response.We develops a soilstructure interaction system model and a comparative rigid foundation model using the finite element software LS-DYNA to investigate the impact of SSI on the dynamic characteristics and seismic response of stone structures.The results indicate that the SSI effect alters stone structures'dynamic properties and seismic response.This alteration is evident in the extended natural vibration period,which reduces overall stiffness,increases interstory displacement angles,and slightly decreases the acceleration response.Under both SSI and FIX systems,the structural failure mode is characterized by the external collapse of the second-story stone walls,which causes the roof stone slabs to lose support and fall,leading to overall collapse.The FIX system demonstrates better structural integrity and stability with slower crack development.In contrast,the SSI system exhibits cracks that appear earlier and develop more rapidly,causing more severe damage.The research findings provide a theoretical basis for the seismic reinforcement of existing stone structures on soft soil foundations.展开更多
In recent years,offshore wind turbines have rap-idly developed,and many pile foundations installed earlier are now approaching decommissioning.Thus,the efficient removal of pile foundations has become a critical issue...In recent years,offshore wind turbines have rap-idly developed,and many pile foundations installed earlier are now approaching decommissioning.Thus,the efficient removal of pile foundations has become a critical issue for the sustainable development of offshore wind energy.To ad-dress this issue,this paper systematically investigates three methods for the recovery of pile foundations using physical model experiments:water injection+lifting,air injection+lifting,and air retention+water injection.The experimental results show that the water injection+lifting method exhibits remarkable advantages in recovering large-diameter and in-clined pile foundations;however,realigning inclined piles during recovery remains challenging,and a risk of pile over-turning exists.The air injection+lifting method proves ef-fective for realigning inclined piles but presents a risk of air expulsion failure,which may affect the continuity and stabil-ity of the recovery process.By contrast,the air retention+water injection method combines the characteristics of water injection and air injection techniques,effectively avoiding air expulsion failure and exhibiting pronounced displacement jumps during pile uplift.These findings provide a valuable reference for future decommissioning practices of offshore wind pile foundations,offer important engineering applica-tion value,and contribute positively to the sustainable devel-opment of the offshore wind industry.展开更多
Four different types of film-forming agents were added to the foundation formulations,and their effects on the makeup-holding properties of the foundations on human facial skin were determined by Visia-CR.The study sh...Four different types of film-forming agents were added to the foundation formulations,and their effects on the makeup-holding properties of the foundations on human facial skin were determined by Visia-CR.The study showed that there was a significant difference between the sample group with film-forming agent and the blank control group,indicating that the addition of film-forming agent had an effect on the makeup-holding performance of the foundation;the makeup-holding effect of the foundation formulated with trimethylsiloxysilicate or(acrylates/dimethicone copolymer,cyclopentasiloxane)was better than that of the foundation formulated with polymethylsilsesquioxane or VP/hexadecene copolymer.This experiment is of guidance significance for the formulation design of long-lasting foundation.展开更多
Clay deposits typically exhibit significant degrees of heterogeneity and anisotropy in their strength and stiffness properties.Such non-monotonic responses can significantly impact the stability analysis and design of...Clay deposits typically exhibit significant degrees of heterogeneity and anisotropy in their strength and stiffness properties.Such non-monotonic responses can significantly impact the stability analysis and design of overlying shallow foundations.In this study,the undrained bearing capacity of shallow foundations resting on inhomogeneous and anisotropic clay layers subjected to oblique-eccentric combined loading is investigated through a comprehensive series of finite element limit analysis(FELA)based on the well-established lower-bound theorem and second-order cone programming(SOCP).The heterogeneity of normally consolidated(NC)clays is simulated by adopting a well-known general model of undrained shear strength increasing linearly with depth.In contrast,for overconsolidated(OC)clays,the variation of undrained shear strength with depth is considered to follow a bilinear trend.Furthermore,the inherent anisotropy is accounted for by adopting different values of undrained shear strength along different directions within the soil medium,employing an iterative-based algorithm.The results of numerical simulations are utilized to investigate the influences of natural soil heterogeneity and inherent anisotropy on the ultimate bearing capacity,failure envelope,and failure mechanism of shallow foundations subjected to the various combinations of vertical-horizontal(V-H)and vertical-moment(V-M)loads.展开更多
To analyze the band gap characteristics of phononic crystals,a two-dimensional phononic crystal plate model with an elastic foundation was first established.The plane wave expansion method was used to compute the disp...To analyze the band gap characteristics of phononic crystals,a two-dimensional phononic crystal plate model with an elastic foundation was first established.The plane wave expansion method was used to compute the dispersion curves of this phononic crystal model,and the results were compared with those from the finite element method to verify their accuracy.Subsequently,a parameter study explored the effects of the elastic foundation coeffi-cient and coverage ratio on the band gap.The results indicate that as the coverage ratio of the elastic foundation increases,the band gap significantly expands,reaching its maximum value at 100%coverage.Additionally,as the elastic foundation stiffness increases,the band gap gradually widens and converges toward fixed boundary conditions.The study also investigated the band gap of phononic crystal plates with defects,finding that the vibrational energy concentrates at the defect unit cell.Furthermore,the defect band frequency can be effectively modulated by adjusting the coefficient of the elastic foundation,providing a theoretical basis for achieving efficient energy conversion.展开更多
To study the dynamic response rules of pile foundations of mega-bridges over faults in strong seismic areas,a finite element model of the pile foundation-soil-fault interaction of the Haiwen Bridge is established.The ...To study the dynamic response rules of pile foundations of mega-bridges over faults in strong seismic areas,a finite element model of the pile foundation-soil-fault interaction of the Haiwen Bridge is established.The 0.2-0.6 g peak acceleration of the 5010 seismic waves is input to study the effect of the seismic wave of different intensities and the distance changes between the fault and the pile foundation on the dynamic response of the pile body.The results show that the soil layer covering the bedrock amplifies the peak pile acceleration,and the amplifying effect decreases with increasing seismic wave intensity.However,bedrock has less of an effect on peak acceleration.The relative pile displacement shows the mechanical properties of elastic long piles.The pile foundation generates a large bending moment at the bedrock face and the upper soil layer interface,and a large shear force at the pile top and the soft-hard soil body interface.The relative displacement,bending,and shear bearing characteristics of the pile foundations on the upper and lower plates of the fault are significantly different.The deformation characteristics are affected by faults in a region ten times the pile diameter.Analysis of the dynamic p-y curves shows that the soil resistance on the pile side of the lower plate at the same depth is greater than that of the upper plate.Sensitivity of the dynamic response of pile foundations on either side of the fault to the effects of seismic intensity and distance between the pile foundation and the fault:distance l seismic intensity q.展开更多
In order to effectively improve the horizontal bearing capacity of pile foundations,this study proposes post-expanded arm grouting technology and associated pile foundations.The horizontal bearing characteristic of th...In order to effectively improve the horizontal bearing capacity of pile foundations,this study proposes post-expanded arm grouting technology and associated pile foundations.The horizontal bearing characteristic of the post-expanded arm grouting pile was explored through model tests.The test results indicate that the post-expanded arm grouting pile can increase the contact area between the pile and soil,and can improve the strength of the soil.The horizontal bearing capacity of the post-expanded arm grouting pile was approximately 3 times that of the conventional pile.It also shows that the larger the plate diameter ratio or grouting volume,the higher the horizontal bearing capacity of the post-expanded arm grouting pile.The maximum bending moment of the post-expanded arm grouting pile was located at the pile plate,and the displacement zero point of the new pile was higher than that of the conventional pile.The soil resistance at the pile plate was significantly higher than that of conventional piles,indicating that the pile plate effectively enhances the soil resistance.The improved p-y curve model and horizontal bearing capacity calculation method for the post-expanded arm grouting pile were proposed by considering the pile plate diameter factor.This method was finally verified by experimental results.The results of this study can provide a reference for calculating the horizontal bearing capacity of the post-expanded arm grouting pile.展开更多
The Euler-Bernoulli(E-B)beam theory is combined with Green-Lindsay's(G-L)generalized thermoelasticity theory to analyze the vibration of microbeams.The frequency control equation,based on the two-parameter Winkler...The Euler-Bernoulli(E-B)beam theory is combined with Green-Lindsay's(G-L)generalized thermoelasticity theory to analyze the vibration of microbeams.The frequency control equation,based on the two-parameter Winkler-Pasternak elastic foundation for simply-supported microbeams,is presented.This study investigates the effects of the side-to-thickness ratio and relaxation time parameters on the vibrational natural frequency of thermoelastic microbeam resonators.The frequencies derived from the present model are compared with those from Lord and Shulman's(L-S)theory.The fourthorder solutions for natural vibration frequencies are graphically displayed for comparison.Therefore,attention should be paid to the use of effective foundations to prevent microbeam damage caused by contraction and expansion problems caused by high temperatures.展开更多
The feasibility of constructing shallow foundations on saturated sands remains uncertain.Seismic design standards simply stipulate that geotechnical investigations for a shallow foundation on such soils shall be condu...The feasibility of constructing shallow foundations on saturated sands remains uncertain.Seismic design standards simply stipulate that geotechnical investigations for a shallow foundation on such soils shall be conducted to mitigate the effects of the liquefaction hazard.This study investigates the seismic behavior of strip foundations on typical two-layered soil profiles-a natural loose sand layer supported by a dense sand layer.Coupled nonlinear dynamic analyses have been conducted to calculate response parameters,including seismic settlement,the acceleration response on the ground surface,and excess pore pressure beneath strip foundations.A novel liquefaction potential index(LPI_(footing)),based on excess pore pressure ratios across a given region of soil mass beneath footings is introduced to classify liquefaction severity into three distinct levels:minor,moderate,and severe.To validate the proposed LPI_(footing),the foundation settlement is evaluated for the different liquefaction potential classes.A classification tree model has been grown to predict liquefaction susceptibility,utilizing various input variables,including earthquake intensity on the ground surface,foundation pressure,sand permeability,and top layer thickness.Moreover,a nonlinear regression function has been established to map LPI_(footing) in relation to these input predictors.The models have been constructed using a substantial dataset comprising 13,824 excess pore pressure ratio time histories.The performance of the developed models has been examined using various methods,including the 10-fold cross-validation method.The predictive capability of the tree also has been validated through existing experimental studies.The results indicate that the classification tree is not only interpretable but also highly predictive,with a testing accuracy level of 78.1%.The decision tree provides valuable insights for engineers assessing liquefaction potential beneath strip foundations.展开更多
On the afternoon of May 3Oth,the parallel forum"Strengthening the Judicial Foundations of Shared Values of Mankind,"as a component of the 4th Dialogue on Exchanges and Mutual Learning among Civilisations,was...On the afternoon of May 3Oth,the parallel forum"Strengthening the Judicial Foundations of Shared Values of Mankind,"as a component of the 4th Dialogue on Exchanges and Mutual Learning among Civilisations,was held in Dunhuang.More than 50 experts and scholars from nine countries,including China,Germany and the United Kingdom,engaged in in-depth discussions on the topic.展开更多
With the continuous development of the offshore wind industry,the design concept of composite foundation has been given attention in the past decade.This paper presents an accurate method for investigating the horizon...With the continuous development of the offshore wind industry,the design concept of composite foundation has been given attention in the past decade.This paper presents an accurate method for investigating the horizontal vibration of monopile-friction wheel composite foundations in layered saturated soil.Firstly,the three-dimensional continuum mechanics theory with the range of linear elasticity is introduced to calculate the frictional resistance distributed on the upper soil surface.Then,the resistances of multilayered soils and inviscid seawater to the pile shaft under horizontal harmonic excitation are obtained using Novak's plane strain model,Biot's porous media theory and radiationwave theory.Thirdly,the expressions for the deformation,bending moment and internal force of the Euler-Bernoulli pile are derived using the boundary conditions with definitephysical meaning and transfer matrix method.By comparing with the results of 1g laboratory test and the idealized formula reported by the literature,the rationality and accuracy of the developed dynamical model can be verified.Finally,this paper conducts a series of worked examples to investigate the influencesof the elastic modulus and thickness of three-layer saturated soil and the location of interlayer soil on the horizontal dynamic vibration of composite foundation.The results show that an increase in elastic modulus of the surface soil is an effective way to improve the dynamic stability of the composite foundation in service conditions.The conclusions drawn from the numerical examples can develop some guidelines for the current foundation design of offshore wind turbines.展开更多
Conventionally,foundations have been classified as shallow or deep in routine civil engineering practice.However,due to recent developments,two other approaches,semi-deep and ground modification foundations,are now av...Conventionally,foundations have been classified as shallow or deep in routine civil engineering practice.However,due to recent developments,two other approaches,semi-deep and ground modification foundations,are now available,complicating foundation categorization.Accordingly,a new concept for foundation categorization is introduced in this paper based on insights into the theory of structure analysis.Based on the form aspect,foundation systems can be categorized as one-dimensional(linear),two-dimensional(planar),and threedimensional(volumetric).Based on the load transfer aspect,foundations can also be categorized as vector-acting(piles),section or surface-acting(rafts and shells),and block-acting(piled rafts).As a step toward implementing this new categorization scheme,a database of 22 cases has been compiled,symbolizing novel introduced foundation systems.This compilation involves structures such as offshore jackets,high-rise buildings,towers and storages,and diverse geomaterials.Among them,a few have been selected for detailed evaluation,emphasizing influential factors in foundation selection,comprising superstructure,subsoil condition,foundation system,circumferential conditions,and supplementary considerations,that is,constructional and sustainability-based issues.Lessons learned from experience and these knowledge-based cases have described for foundation selection and implementation.Geotechnical and practical aspects with critical components have been realized as major performance assessment and comparison factors.Foundation systems have been compared and ranked using the improved analytic hierarchy process approach.Finally,four categories of buildings,from low-rise to towers and four prevailing levels of soil strength,from soft to very hard,have been considered to propose a perspective for building substructure implementation,adapted via relevant cases.Overall,the introduced categorization is recognized as an efficient algorithm for the experimentation of appropriate foundations for specific structures and subsoil conditions.展开更多
Installing internal bulkheads in a composite bucket foundation alters the rotational symmetry characteristic of a single-compartment bucket foundation,consequently influencing the stress distribution within the bucket...Installing internal bulkheads in a composite bucket foundation alters the rotational symmetry characteristic of a single-compartment bucket foundation,consequently influencing the stress distribution within the bucket and surrounding soil.During the seabed penetration of a spudcan from a jack-up wind turbine installation vessel,an angle may form between the spudcan’s axis and the axis of symmetry of the adjacent composite bucket foundation in the horizontal plane.Such a misalignment may affect load distribution and the non-uniform interaction between the foundation,soil,and spudcan,ultimately influencing the foundation’s stability.This study employs physical model tests to ascertain the trends in end resistance during spudcan penetration in sand,the extent of soil disturbance,and the backflow condition.The finite element coupled Eulerian-Lagrangian method is validated and utilized to determine the range of penetration angles that induce alterations in the maximum vertical displacement and tilt rate of the composite bucket foundation in sand.The differential contact stress distribution at the base of the bucket is analyzed,with qualitative criteria for sand backflow provided.Findings demonstrate that the maximum vertical displacement and tilt rate of the composite bucket foundation display a“wave-like”variation with the increasing spudcan penetration angle,peaking when the angle between the spudcan and bulkhead is the smallest.Stress distribution is predominantly concentrated at the base and apex of the bucket,becoming increasingly uneven as the penetration angle deviates from the foundation’s symmetry axis.The maximum stress gradually shifts to the junction of the bulkhead and bucket bottom on the side with the shortest net distance from the spudcan.Considering the in-place stability and stress state of the composite bucket foundation is therefore imperative,and particular attention should be paid to the foundation’s state when the angle between the spudcan and bulkhead is small.展开更多
文摘Monocolumn composite bucket foundation is a new type of offshore wind energy foundation.Its bearing characteristics under shallow bedrock conditions and complex geological conditions have not been extensively studied.Therefore,to analyze its bearing characteristics under complex conditions-such as silty soil,chalky soil,and shallow bedrock-this paper employs finite element software to establish various soil combination scenarios.The load-displacement curves of the foundations under these scenarios are calculated to subsequently evaluate the horizontal ultimate bearing capacity.This study investigates the effects of shallow bedrock depth,the type of soil above the bedrock,the thickness of layered soil,and the quality of layered soil on the bearing characteristics of the monocolumn composite bucket foundation.Based on the principle of single-variable control,the ultimate bearing capacity characteristics of the foundation under different conditions are compared.The distribution of soil pressure inside and outside the bucket wall on the compressed side of the foundation,along with the plastic strain of the soil at the base of the foundation,is also analyzed.In conclusion,shallow bedrock somewhat reduces foundation bearing capacity.Under shallow bedrock conditions,the degree of influence on foundation bearing capacity characteristics can considerably vary on different upper soils.The thickness of each soil layer and the depth to bedrock in stratified soils also affect the bearing capacity of the foundation.The findings of this paper provide a theoretical reference for related foundation design and construction.In practice,the bearing performance of the foundation can be enhanced by improvingthe soil quality in the bucket,adjusting the penetration depth,adjusting the percentage of different types of soil layers in the bucket,and applying other technical construction methods.
文摘The main objective of this study is to investigate the buckling analysis of CCSs reinforced by CNTs subjected to combined loading of hydrostatic pressure and axial compression resting on the twoparameter elastic foundation(T-P-EF).It is one of the first attempts to derive the governing equations of the CCSs reinforced with CNTs,based on a generalized first-order shear deformation shell theory(FSDST)which includes shell-foundation interaction.By adopting the extended mixing rule,the effective material properties of CCSs reinforced by CNTs with linear distributions are approximated by introducing some efficiency parameters.Three carbon nanotube distribution in the matrix,i.e.uniform distribution(U)and V and X-types linear distribution are taken into account.The stability equations are solved by using the Galerkin procedure to determine the combined buckling loads(CBLs)of the structure selected here.The numerical illustrations cover CBLs characteristics of CCSs reinforced by CNTs in the presence of the T-P-EF.Finally,a parametric study is carried out to study the influences of the foundation parameters,the volume fraction of carbon nanotubes and the types of reinforcement on the CBLs.
基金financially supported by the National Key Research and Development Program of China (Grant No. 2021YFB2601100)the National Natural Science Foundation of China (Grant No. 51979190)。
文摘Under the combination of currents and waves, seabed scour occurs around offshore wind turbine foundations, which affects the stability and safe operation of offshore wind turbines. In this study, physical model experiments under unidirectional flow, bidirectional flow, and wave-current interactions with different flow directions around the pile group foundation were first conducted to investigate the development of scour around the pile group foundation.Additionally, a three-dimensional scour numerical model was established via the open-source software REEF3D to simulate the flow field and scour around the prototype-scale foundation. The impact of flow on scour was discussed.Under unidirectional flow, scour equilibrium was reached more quickly, with the maximum scour depth reaching approximately 1.2 times the pile diameter and the extent of the scour hole spanning about 4.9 times the pile diameter.Compared with those under unidirectional flow, the scour depths under combinations of currents and waves, as well as bidirectional flow, were slightly smaller. However, the morphology of scour holes was more uniform and symmetrical. The numerical simulation results show good agreement with the experimental data, demonstrating the impact of varying flow directions on the velocity distribution around the foundation, the morphology of scour holes, and the location of the maximum scour depth.
文摘Two fundamental solutions for bending problem of Reissner's plates on twoparameter foundation are derived by means of Fouier integral transformation of generalized function in this paper.On the basis of virtual work principles, three boundary integral equations which fit for arbitrary shapes, loads and boundary conditions of thick plates are presented according to Hu Haichang's theory about Reissner's plates. It provides the fundamental theories for the application of BEM. A numerical example is given for clamped, simply supported and free boundary conditions. The results obtained are satisfactory as compared with the analytical methods.
文摘The problems noted in the structures built on wooden foundation piles in a lake environment required various works to strengthen over time.This work mainly consists of the recovery of the foundation mass by micropiles due to the increase in loads on the structures,or the recovery of the foundation mass by injection,which is carried out when voids form between the ground and the wooden foundation elements.The high cost of foundation reinforcement methods led the National Agency for the Development of Tourist Heritage in Benin(ANPT)to replace the wooden foundation piles with reinforced concrete piles in the implementation of the project“reinventing the lakeside city of Ganvié”.This article presents an artisanal technology for the creation of reinforced concrete foundation piles in a lake environment.On-site examples made it possible to evaluate the performance of this artisanal implementation technique.The installation of these piles is carried out following manual drilling,followed by the installation of reinforcement and the pouring of concrete on site.The implementation of reinforced concrete foundation piles in place of the wooden ones studied in this article only impacted the infrastructure of the homes of the lakeside town of Ganviébut not the superstructure,which preserved the old traditional wooden architecture and thatched roofs.Thus,the ambition to move this city of Ganviéfrom the stage of a lake village to that of a floating city is very successful.This will contribute to improving the environment and living conditions of the populations and will promote economic development through tourism.
基金Project supported by the National Natural Science Foundation of China(No.12525202)。
文摘Transcritical and supercritical fluids widely exist in aerospace propulsion systems,such as the coolant flow in the regenerative cooling channels of scramjet engines.To numerically simulate the coolant flow,we must address the challenges in solving Riemann problems(RPs)for real fluids under complex flow conditions.In this study,an exact numerical solution for the one-dimensional RP of two-parameter fluids is developed.Due to the comprehensive resolution of fluid thermodynamics,the proposed solution framework is suitable for all forms of the two-parameter equation of state(EoS).The pressure splitting method is introduced to enable parallel calculation of RPs across multiple grid points.Theoretical analysis demonstrates the isentropic nature of weak waves in two-parameter fluids,ensuring that the same mathematical properties as ideal gas could be applied in Newton's iteration.A series of numerical cases validate the effectiveness of the proposed method.A comparative analysis is conducted on the exact Riemann solutions for the real fluid EoS,the ideal gas EoS,and the improved ideal gas EoS under supercritical and transcritical conditions.The results indicate that the improved one produces smaller errors in the calculation of momentum and energy fluxes.
基金jointly sponsored by Fujian Province construction science and technology development research project(2023-B-07,2023-K-47,2022-K-118)。
文摘The coastal region of Fujian contains numerous existing stone masonry structures,many of which are constructed on soft soil sites.Previous studies have shown that the soil-structure interaction(SSI)effect on soft soil foundations can prolong the structure's natural vibration period and enhance its seismic response.We develops a soilstructure interaction system model and a comparative rigid foundation model using the finite element software LS-DYNA to investigate the impact of SSI on the dynamic characteristics and seismic response of stone structures.The results indicate that the SSI effect alters stone structures'dynamic properties and seismic response.This alteration is evident in the extended natural vibration period,which reduces overall stiffness,increases interstory displacement angles,and slightly decreases the acceleration response.Under both SSI and FIX systems,the structural failure mode is characterized by the external collapse of the second-story stone walls,which causes the roof stone slabs to lose support and fall,leading to overall collapse.The FIX system demonstrates better structural integrity and stability with slower crack development.In contrast,the SSI system exhibits cracks that appear earlier and develop more rapidly,causing more severe damage.The research findings provide a theoretical basis for the seismic reinforcement of existing stone structures on soft soil foundations.
基金The National Natural Science Foundation of China (No. 52171274)。
文摘In recent years,offshore wind turbines have rap-idly developed,and many pile foundations installed earlier are now approaching decommissioning.Thus,the efficient removal of pile foundations has become a critical issue for the sustainable development of offshore wind energy.To ad-dress this issue,this paper systematically investigates three methods for the recovery of pile foundations using physical model experiments:water injection+lifting,air injection+lifting,and air retention+water injection.The experimental results show that the water injection+lifting method exhibits remarkable advantages in recovering large-diameter and in-clined pile foundations;however,realigning inclined piles during recovery remains challenging,and a risk of pile over-turning exists.The air injection+lifting method proves ef-fective for realigning inclined piles but presents a risk of air expulsion failure,which may affect the continuity and stabil-ity of the recovery process.By contrast,the air retention+water injection method combines the characteristics of water injection and air injection techniques,effectively avoiding air expulsion failure and exhibiting pronounced displacement jumps during pile uplift.These findings provide a valuable reference for future decommissioning practices of offshore wind pile foundations,offer important engineering applica-tion value,and contribute positively to the sustainable devel-opment of the offshore wind industry.
文摘Four different types of film-forming agents were added to the foundation formulations,and their effects on the makeup-holding properties of the foundations on human facial skin were determined by Visia-CR.The study showed that there was a significant difference between the sample group with film-forming agent and the blank control group,indicating that the addition of film-forming agent had an effect on the makeup-holding performance of the foundation;the makeup-holding effect of the foundation formulated with trimethylsiloxysilicate or(acrylates/dimethicone copolymer,cyclopentasiloxane)was better than that of the foundation formulated with polymethylsilsesquioxane or VP/hexadecene copolymer.This experiment is of guidance significance for the formulation design of long-lasting foundation.
文摘Clay deposits typically exhibit significant degrees of heterogeneity and anisotropy in their strength and stiffness properties.Such non-monotonic responses can significantly impact the stability analysis and design of overlying shallow foundations.In this study,the undrained bearing capacity of shallow foundations resting on inhomogeneous and anisotropic clay layers subjected to oblique-eccentric combined loading is investigated through a comprehensive series of finite element limit analysis(FELA)based on the well-established lower-bound theorem and second-order cone programming(SOCP).The heterogeneity of normally consolidated(NC)clays is simulated by adopting a well-known general model of undrained shear strength increasing linearly with depth.In contrast,for overconsolidated(OC)clays,the variation of undrained shear strength with depth is considered to follow a bilinear trend.Furthermore,the inherent anisotropy is accounted for by adopting different values of undrained shear strength along different directions within the soil medium,employing an iterative-based algorithm.The results of numerical simulations are utilized to investigate the influences of natural soil heterogeneity and inherent anisotropy on the ultimate bearing capacity,failure envelope,and failure mechanism of shallow foundations subjected to the various combinations of vertical-horizontal(V-H)and vertical-moment(V-M)loads.
基金The National Natural Science Foundation of China(No.12002086)。
文摘To analyze the band gap characteristics of phononic crystals,a two-dimensional phononic crystal plate model with an elastic foundation was first established.The plane wave expansion method was used to compute the dispersion curves of this phononic crystal model,and the results were compared with those from the finite element method to verify their accuracy.Subsequently,a parameter study explored the effects of the elastic foundation coeffi-cient and coverage ratio on the band gap.The results indicate that as the coverage ratio of the elastic foundation increases,the band gap significantly expands,reaching its maximum value at 100%coverage.Additionally,as the elastic foundation stiffness increases,the band gap gradually widens and converges toward fixed boundary conditions.The study also investigated the band gap of phononic crystal plates with defects,finding that the vibrational energy concentrates at the defect unit cell.Furthermore,the defect band frequency can be effectively modulated by adjusting the coefficient of the elastic foundation,providing a theoretical basis for achieving efficient energy conversion.
基金funded by National Natural Science Foundation of China Projects(51708040)Hainan Provincial Transportation Science and Technology Project(HNZXY2015-045R)Changan University Central University Basic Research Business Fund Special Funds(No.300102218115).
文摘To study the dynamic response rules of pile foundations of mega-bridges over faults in strong seismic areas,a finite element model of the pile foundation-soil-fault interaction of the Haiwen Bridge is established.The 0.2-0.6 g peak acceleration of the 5010 seismic waves is input to study the effect of the seismic wave of different intensities and the distance changes between the fault and the pile foundation on the dynamic response of the pile body.The results show that the soil layer covering the bedrock amplifies the peak pile acceleration,and the amplifying effect decreases with increasing seismic wave intensity.However,bedrock has less of an effect on peak acceleration.The relative pile displacement shows the mechanical properties of elastic long piles.The pile foundation generates a large bending moment at the bedrock face and the upper soil layer interface,and a large shear force at the pile top and the soft-hard soil body interface.The relative displacement,bending,and shear bearing characteristics of the pile foundations on the upper and lower plates of the fault are significantly different.The deformation characteristics are affected by faults in a region ten times the pile diameter.Analysis of the dynamic p-y curves shows that the soil resistance on the pile side of the lower plate at the same depth is greater than that of the upper plate.Sensitivity of the dynamic response of pile foundations on either side of the fault to the effects of seismic intensity and distance between the pile foundation and the fault:distance l seismic intensity q.
基金supported by the National Natural Science Foundation of China(Grant Nos.52208333 and 52378328)China Communications Construction Company Ltd.(Grant No.2023-ZJKJ-01).
文摘In order to effectively improve the horizontal bearing capacity of pile foundations,this study proposes post-expanded arm grouting technology and associated pile foundations.The horizontal bearing characteristic of the post-expanded arm grouting pile was explored through model tests.The test results indicate that the post-expanded arm grouting pile can increase the contact area between the pile and soil,and can improve the strength of the soil.The horizontal bearing capacity of the post-expanded arm grouting pile was approximately 3 times that of the conventional pile.It also shows that the larger the plate diameter ratio or grouting volume,the higher the horizontal bearing capacity of the post-expanded arm grouting pile.The maximum bending moment of the post-expanded arm grouting pile was located at the pile plate,and the displacement zero point of the new pile was higher than that of the conventional pile.The soil resistance at the pile plate was significantly higher than that of conventional piles,indicating that the pile plate effectively enhances the soil resistance.The improved p-y curve model and horizontal bearing capacity calculation method for the post-expanded arm grouting pile were proposed by considering the pile plate diameter factor.This method was finally verified by experimental results.The results of this study can provide a reference for calculating the horizontal bearing capacity of the post-expanded arm grouting pile.
基金the Deanship of Research and Graduate Studies at King Khalid University for funding this work through a large research project(No.RGP2/80/45)。
文摘The Euler-Bernoulli(E-B)beam theory is combined with Green-Lindsay's(G-L)generalized thermoelasticity theory to analyze the vibration of microbeams.The frequency control equation,based on the two-parameter Winkler-Pasternak elastic foundation for simply-supported microbeams,is presented.This study investigates the effects of the side-to-thickness ratio and relaxation time parameters on the vibrational natural frequency of thermoelastic microbeam resonators.The frequencies derived from the present model are compared with those from Lord and Shulman's(L-S)theory.The fourthorder solutions for natural vibration frequencies are graphically displayed for comparison.Therefore,attention should be paid to the use of effective foundations to prevent microbeam damage caused by contraction and expansion problems caused by high temperatures.
文摘The feasibility of constructing shallow foundations on saturated sands remains uncertain.Seismic design standards simply stipulate that geotechnical investigations for a shallow foundation on such soils shall be conducted to mitigate the effects of the liquefaction hazard.This study investigates the seismic behavior of strip foundations on typical two-layered soil profiles-a natural loose sand layer supported by a dense sand layer.Coupled nonlinear dynamic analyses have been conducted to calculate response parameters,including seismic settlement,the acceleration response on the ground surface,and excess pore pressure beneath strip foundations.A novel liquefaction potential index(LPI_(footing)),based on excess pore pressure ratios across a given region of soil mass beneath footings is introduced to classify liquefaction severity into three distinct levels:minor,moderate,and severe.To validate the proposed LPI_(footing),the foundation settlement is evaluated for the different liquefaction potential classes.A classification tree model has been grown to predict liquefaction susceptibility,utilizing various input variables,including earthquake intensity on the ground surface,foundation pressure,sand permeability,and top layer thickness.Moreover,a nonlinear regression function has been established to map LPI_(footing) in relation to these input predictors.The models have been constructed using a substantial dataset comprising 13,824 excess pore pressure ratio time histories.The performance of the developed models has been examined using various methods,including the 10-fold cross-validation method.The predictive capability of the tree also has been validated through existing experimental studies.The results indicate that the classification tree is not only interpretable but also highly predictive,with a testing accuracy level of 78.1%.The decision tree provides valuable insights for engineers assessing liquefaction potential beneath strip foundations.
文摘On the afternoon of May 3Oth,the parallel forum"Strengthening the Judicial Foundations of Shared Values of Mankind,"as a component of the 4th Dialogue on Exchanges and Mutual Learning among Civilisations,was held in Dunhuang.More than 50 experts and scholars from nine countries,including China,Germany and the United Kingdom,engaged in in-depth discussions on the topic.
基金supported by the National Natural Science Foundation of China(Grant No.52178329),the China Scholarship Council(Grant No.202306130155)the Postgraduate Scientific Research Innovation Project of Hunan Province,China(Grant No.CX20230442).
文摘With the continuous development of the offshore wind industry,the design concept of composite foundation has been given attention in the past decade.This paper presents an accurate method for investigating the horizontal vibration of monopile-friction wheel composite foundations in layered saturated soil.Firstly,the three-dimensional continuum mechanics theory with the range of linear elasticity is introduced to calculate the frictional resistance distributed on the upper soil surface.Then,the resistances of multilayered soils and inviscid seawater to the pile shaft under horizontal harmonic excitation are obtained using Novak's plane strain model,Biot's porous media theory and radiationwave theory.Thirdly,the expressions for the deformation,bending moment and internal force of the Euler-Bernoulli pile are derived using the boundary conditions with definitephysical meaning and transfer matrix method.By comparing with the results of 1g laboratory test and the idealized formula reported by the literature,the rationality and accuracy of the developed dynamical model can be verified.Finally,this paper conducts a series of worked examples to investigate the influencesof the elastic modulus and thickness of three-layer saturated soil and the location of interlayer soil on the horizontal dynamic vibration of composite foundation.The results show that an increase in elastic modulus of the surface soil is an effective way to improve the dynamic stability of the composite foundation in service conditions.The conclusions drawn from the numerical examples can develop some guidelines for the current foundation design of offshore wind turbines.
文摘Conventionally,foundations have been classified as shallow or deep in routine civil engineering practice.However,due to recent developments,two other approaches,semi-deep and ground modification foundations,are now available,complicating foundation categorization.Accordingly,a new concept for foundation categorization is introduced in this paper based on insights into the theory of structure analysis.Based on the form aspect,foundation systems can be categorized as one-dimensional(linear),two-dimensional(planar),and threedimensional(volumetric).Based on the load transfer aspect,foundations can also be categorized as vector-acting(piles),section or surface-acting(rafts and shells),and block-acting(piled rafts).As a step toward implementing this new categorization scheme,a database of 22 cases has been compiled,symbolizing novel introduced foundation systems.This compilation involves structures such as offshore jackets,high-rise buildings,towers and storages,and diverse geomaterials.Among them,a few have been selected for detailed evaluation,emphasizing influential factors in foundation selection,comprising superstructure,subsoil condition,foundation system,circumferential conditions,and supplementary considerations,that is,constructional and sustainability-based issues.Lessons learned from experience and these knowledge-based cases have described for foundation selection and implementation.Geotechnical and practical aspects with critical components have been realized as major performance assessment and comparison factors.Foundation systems have been compared and ranked using the improved analytic hierarchy process approach.Finally,four categories of buildings,from low-rise to towers and four prevailing levels of soil strength,from soft to very hard,have been considered to propose a perspective for building substructure implementation,adapted via relevant cases.Overall,the introduced categorization is recognized as an efficient algorithm for the experimentation of appropriate foundations for specific structures and subsoil conditions.
文摘Installing internal bulkheads in a composite bucket foundation alters the rotational symmetry characteristic of a single-compartment bucket foundation,consequently influencing the stress distribution within the bucket and surrounding soil.During the seabed penetration of a spudcan from a jack-up wind turbine installation vessel,an angle may form between the spudcan’s axis and the axis of symmetry of the adjacent composite bucket foundation in the horizontal plane.Such a misalignment may affect load distribution and the non-uniform interaction between the foundation,soil,and spudcan,ultimately influencing the foundation’s stability.This study employs physical model tests to ascertain the trends in end resistance during spudcan penetration in sand,the extent of soil disturbance,and the backflow condition.The finite element coupled Eulerian-Lagrangian method is validated and utilized to determine the range of penetration angles that induce alterations in the maximum vertical displacement and tilt rate of the composite bucket foundation in sand.The differential contact stress distribution at the base of the bucket is analyzed,with qualitative criteria for sand backflow provided.Findings demonstrate that the maximum vertical displacement and tilt rate of the composite bucket foundation display a“wave-like”variation with the increasing spudcan penetration angle,peaking when the angle between the spudcan and bulkhead is the smallest.Stress distribution is predominantly concentrated at the base and apex of the bucket,becoming increasingly uneven as the penetration angle deviates from the foundation’s symmetry axis.The maximum stress gradually shifts to the junction of the bulkhead and bucket bottom on the side with the shortest net distance from the spudcan.Considering the in-place stability and stress state of the composite bucket foundation is therefore imperative,and particular attention should be paid to the foundation’s state when the angle between the spudcan and bulkhead is small.
