Ensuring a safe foundation design in soft clay is always a challenging task to engineers.In the present study,the effectiveness of under-reamed piles in soft clay underlaid by stiff clay is numerically studied using t...Ensuring a safe foundation design in soft clay is always a challenging task to engineers.In the present study,the effectiveness of under-reamed piles in soft clay underlaid by stiff clay is numerically studied using the lower-bound finite element limit analysis(LB FELA).The bearing and uplift capacities of under-reamed piles are estimated through non-dimensional factors N_(cul)and Fcul,respectively.These factors increased remarkably and marginally compared to N_(cul)and Fcul of the piles without bulbs when the bulb is placed in stiff and soft clay,respectively.For a given ratio of undrained cohesion of stiff to soft clay(c_(2)/c_(1)),the factors N_(cul)and Fcul moderately increased with the increase in the length-to-shaft-diameter ratio(Lu/D)and adhesion factors in soft clay(α_(s1))and stiff clay(αs2).The variation of radial stress along the pile-soil interface,distribution of axial force in the under-reamed piles,and state of plastic shear failure in the soil are also studied under axial compression and tension.The results of this study are expected to be useful for the estimation of the bearing and uplift capacities of under-reamed piles in uniform clay and soft clay underlaid by stiff clay.展开更多
Recently,the use of deep foundations has increased as a result of the expansion in the construction of high-rise buildings,train tracks,and port berths.As a result of this expansion,it was necessary to use deep founda...Recently,the use of deep foundations has increased as a result of the expansion in the construction of high-rise buildings,train tracks,and port berths.As a result of this expansion,it was necessary to use deep foundations that have low cost,high bearing loads,low settlement,and construction time,and such foundations are subjected to different types of loads such as lateral,vertical compression,and tension loads.This research paper will present one of the most important types of deep foundations that are aptly used in such structures and the most important factors affecting their bearing capacity and settlement in stiff clay.This type of deep foundation is called an under-reamed pile.The factors used in this study are pile length to diameter ratio L/D=30,bulb diameter ratio(Du/D=1.5,2,2.25,and 2.5),number of bulbs(N=1,2,and 3),and spacing ratio(S/D=2 to 8).To investigate the effects of these parameters and obtain optimal results,the PLAXIS 3D was used.The analysis shows that the increase in bulb diameter increases the bearing load by 43%.Bulb spacing controls the failure mechanisms,whether cylindrical shear failure or individual failure and increases the capacity by 66%and 99%,respectively,for two and three bulbs when the bulb spacing becomes S/D=8.When the number of bulbs increases to three,the capacity increases by 90%.If each bulb works individually,the bearing capacity doubles.展开更多
基金The authors gratefully acknowledge the financial support from ISIRD,SRIC,Indian Institute of Technology Kharagpur(No.IIT/SRIC/CE/PPL/2015-16/108).
文摘Ensuring a safe foundation design in soft clay is always a challenging task to engineers.In the present study,the effectiveness of under-reamed piles in soft clay underlaid by stiff clay is numerically studied using the lower-bound finite element limit analysis(LB FELA).The bearing and uplift capacities of under-reamed piles are estimated through non-dimensional factors N_(cul)and Fcul,respectively.These factors increased remarkably and marginally compared to N_(cul)and Fcul of the piles without bulbs when the bulb is placed in stiff and soft clay,respectively.For a given ratio of undrained cohesion of stiff to soft clay(c_(2)/c_(1)),the factors N_(cul)and Fcul moderately increased with the increase in the length-to-shaft-diameter ratio(Lu/D)and adhesion factors in soft clay(α_(s1))and stiff clay(αs2).The variation of radial stress along the pile-soil interface,distribution of axial force in the under-reamed piles,and state of plastic shear failure in the soil are also studied under axial compression and tension.The results of this study are expected to be useful for the estimation of the bearing and uplift capacities of under-reamed piles in uniform clay and soft clay underlaid by stiff clay.
文摘Recently,the use of deep foundations has increased as a result of the expansion in the construction of high-rise buildings,train tracks,and port berths.As a result of this expansion,it was necessary to use deep foundations that have low cost,high bearing loads,low settlement,and construction time,and such foundations are subjected to different types of loads such as lateral,vertical compression,and tension loads.This research paper will present one of the most important types of deep foundations that are aptly used in such structures and the most important factors affecting their bearing capacity and settlement in stiff clay.This type of deep foundation is called an under-reamed pile.The factors used in this study are pile length to diameter ratio L/D=30,bulb diameter ratio(Du/D=1.5,2,2.25,and 2.5),number of bulbs(N=1,2,and 3),and spacing ratio(S/D=2 to 8).To investigate the effects of these parameters and obtain optimal results,the PLAXIS 3D was used.The analysis shows that the increase in bulb diameter increases the bearing load by 43%.Bulb spacing controls the failure mechanisms,whether cylindrical shear failure or individual failure and increases the capacity by 66%and 99%,respectively,for two and three bulbs when the bulb spacing becomes S/D=8.When the number of bulbs increases to three,the capacity increases by 90%.If each bulb works individually,the bearing capacity doubles.
