Monopile response under undrained conditions in sand is gaining increasing interests owing to the recent development of offshore wind farms in seismic regions.Pore pressure evolution in liquefiable soil can significan...Monopile response under undrained conditions in sand is gaining increasing interests owing to the recent development of offshore wind farms in seismic regions.Pore pressure evolution in liquefiable soil can significantly reduce the strength and stiffness of the soil which in turn affects the structural dynamic response.Several numerical models have been developed in the last two decades to enhance understanding of the mechanism of monopile-soil interaction with the existence of pore water pressure.In this study,the effects of geometry and static vertical load on monopile lateral response were studied using three-dimensional finite element methods that consider the existence of lateral cyclic load-induced pore water pressure.To achieve reliable simulation results of pore pressure development and pile displacement accumulation during cyclic loading,the simple anisotropic sand model with memory surface for undrained cyclic behavior of sand was adopted.For piles with the same diameter,a accumulated pile head displacement during lateral cyclic loading decreased linearly with increasing pile embedded length but increased with increasing eccentricity.Static vertical load had minor effects on pile cyclic lateral response.The distributions of mean effective stress and pore water pressure in the soil domain were presented.The pile reaction curve(cyclic soil reaction against pile defection)of the monopile was extracted.The numerical results aim to provide reference for optimized engineering design procedures.展开更多
The nature of subsurface flow depends largely on hydraulic conductivity of the vadoze zone, permeability of the underlying bedrock, existence of soil layers differing in hydraulic properties and macropore content, soi...The nature of subsurface flow depends largely on hydraulic conductivity of the vadoze zone, permeability of the underlying bedrock, existence of soil layers differing in hydraulic properties and macropore content, soil depth, and slope angle.Quantification of flow pathways on forested hillslopes is essential to understand hydrological dynamics and solute transport patterns.Acrisols, with their argic Bt horizons, are challenging in this respect.To further elucidate flow pathways of water and short-term variability of soil moisture patterns in Acrisols, a field study was conducted on a forested hillslope in a sub-catchment of the Tie Shan Ping(TSP)watershed, 25 km northeast of Chongqing City, China.This catchment is covered by a mixed secondary forest dominated by Masson pine(Pinus massoniana).Soil saturated hydraulic conductivity(K sat) was significantly reduced at the interface between the AB and Bt horizons(2.6 × 10^(-5) vs.1.2 × 10^(-6) m s^(-1)), which led to that the flow volume generated in the Bt horizon was of little quantitative importance compared to that in the AB horizon.There was a marked decrease in porosity between the OA and AB horizons, with a further decrease deeper in the mineral subsoil.Especially, the content of soil pores > 300 μm was higher in the AB horizon(14.3%)than in the Bt horizon(6.5%).This explained the difference in soil K sat values.This study showed that Bt horizon had limited water transport capability, forcing part of the infiltrated rainwater as interflow through the OA and AB horizons.Thus, the topsoil responded quickly to rainfall events, causing frequent cycles of saturation and aeration of soil pores.展开更多
Blast-loaded reinforced concrete(RC)slabs should fail under a ductile bending mechanism enabling high energy absorption capacity.Hence,brittle shear failure must be avoided.However,due to the uncertainties related to ...Blast-loaded reinforced concrete(RC)slabs should fail under a ductile bending mechanism enabling high energy absorption capacity.Hence,brittle shear failure must be avoided.However,due to the uncertainties related to the materials,geometry,and resistance models,it may be difficult to predict which failure mode will prevail.This study analytically estimated the probability of premature flexural shear failure of slender RC one-way slabs subjected to blast loading considering such uncertainties and using the Monte Carlo(MC)method.The resistance models in Eurocode 2 were adopted.Specimens with and without shear reinforcement were analyzed.Bending failure was shown to be the most likely failure mode in the studied slabs.However,the probability of shear failure developing before bending failure was still relatively high,particularly for slabs without stirrups.To increase the confidence level concerning the preferred failure mechanism,the article proposes an overstrength factor to magnify the shear demand of the blast-loaded RC slab.Values of the overstrength factor for different target reliability levels were calculated.The study also found that the probability of premature shear failure increased with increasing amount of longitudinal reinforcement and decreasing slenderness.Likewise,greater impulse was found to enhance the risk for shear failure.展开更多
文摘Monopile response under undrained conditions in sand is gaining increasing interests owing to the recent development of offshore wind farms in seismic regions.Pore pressure evolution in liquefiable soil can significantly reduce the strength and stiffness of the soil which in turn affects the structural dynamic response.Several numerical models have been developed in the last two decades to enhance understanding of the mechanism of monopile-soil interaction with the existence of pore water pressure.In this study,the effects of geometry and static vertical load on monopile lateral response were studied using three-dimensional finite element methods that consider the existence of lateral cyclic load-induced pore water pressure.To achieve reliable simulation results of pore pressure development and pile displacement accumulation during cyclic loading,the simple anisotropic sand model with memory surface for undrained cyclic behavior of sand was adopted.For piles with the same diameter,a accumulated pile head displacement during lateral cyclic loading decreased linearly with increasing pile embedded length but increased with increasing eccentricity.Static vertical load had minor effects on pile cyclic lateral response.The distributions of mean effective stress and pore water pressure in the soil domain were presented.The pile reaction curve(cyclic soil reaction against pile defection)of the monopile was extracted.The numerical results aim to provide reference for optimized engineering design procedures.
基金supported by the Norwegian Research Council(Nos.193725/S30 and 209696/E10)Chinese Academy of Science(CAS)(No.209696/E10)
文摘The nature of subsurface flow depends largely on hydraulic conductivity of the vadoze zone, permeability of the underlying bedrock, existence of soil layers differing in hydraulic properties and macropore content, soil depth, and slope angle.Quantification of flow pathways on forested hillslopes is essential to understand hydrological dynamics and solute transport patterns.Acrisols, with their argic Bt horizons, are challenging in this respect.To further elucidate flow pathways of water and short-term variability of soil moisture patterns in Acrisols, a field study was conducted on a forested hillslope in a sub-catchment of the Tie Shan Ping(TSP)watershed, 25 km northeast of Chongqing City, China.This catchment is covered by a mixed secondary forest dominated by Masson pine(Pinus massoniana).Soil saturated hydraulic conductivity(K sat) was significantly reduced at the interface between the AB and Bt horizons(2.6 × 10^(-5) vs.1.2 × 10^(-6) m s^(-1)), which led to that the flow volume generated in the Bt horizon was of little quantitative importance compared to that in the AB horizon.There was a marked decrease in porosity between the OA and AB horizons, with a further decrease deeper in the mineral subsoil.Especially, the content of soil pores > 300 μm was higher in the AB horizon(14.3%)than in the Bt horizon(6.5%).This explained the difference in soil K sat values.This study showed that Bt horizon had limited water transport capability, forcing part of the infiltrated rainwater as interflow through the OA and AB horizons.Thus, the topsoil responded quickly to rainfall events, causing frequent cycles of saturation and aeration of soil pores.
基金supported by Trafikverket(Swedish Transport Administration)Fortifikationsverket(Swedish Fortifications Agency)Myndigheten för samhällsskydd och beredskap(Swedish Civil Contingencies Agency).
文摘Blast-loaded reinforced concrete(RC)slabs should fail under a ductile bending mechanism enabling high energy absorption capacity.Hence,brittle shear failure must be avoided.However,due to the uncertainties related to the materials,geometry,and resistance models,it may be difficult to predict which failure mode will prevail.This study analytically estimated the probability of premature flexural shear failure of slender RC one-way slabs subjected to blast loading considering such uncertainties and using the Monte Carlo(MC)method.The resistance models in Eurocode 2 were adopted.Specimens with and without shear reinforcement were analyzed.Bending failure was shown to be the most likely failure mode in the studied slabs.However,the probability of shear failure developing before bending failure was still relatively high,particularly for slabs without stirrups.To increase the confidence level concerning the preferred failure mechanism,the article proposes an overstrength factor to magnify the shear demand of the blast-loaded RC slab.Values of the overstrength factor for different target reliability levels were calculated.The study also found that the probability of premature shear failure increased with increasing amount of longitudinal reinforcement and decreasing slenderness.Likewise,greater impulse was found to enhance the risk for shear failure.
