Experimental Study On The Stress Concentration Factor And The Ultimate Bearing Capacity Of Tapered-poled Pipe-pile With Hole

The inclined side of tapered pipe-pile with hole increases the contact area between the pile and the soil,so that it is more reasonable,and can exert the lateral friction of the soil around the pile;At the same time,as the vertical reinforcement of composite foundation,the size of the upper end of the tapered pipe-pile with hole becomes larger;the replacement ratio of the composite foundation area is increased and thus the bearing capacity of the composite foundation can be improved.However,in the process of static sinking-pile,there are many problems such as inconvenient pile,insufficient treatment depth and obvious soil squeezing effect.In order to increase the depth of foundation treatment and make the excess pore water enter into the inner cavity of the pipe pile,a kind of technology of tapered-poled pipe-pile with hole is put forward.Tapered-poled pipe-pile with hole can accelerate the excess pore water pressure to accelerate the dissipation and reduce the maximum pore water pressure and the soil compaction effect,thus improving the shear strength of the soil.However,the opening will lead to the destruction of the geometric continuity of the structure,resulting in obvious stress concentration,thus reducing the bearing capacity and service life of the structure.Therefore,this paper is focused on the stress concentration factor and the ultimate bearing capacity reduction law of tapered-poled pipe-pile with hole.By using the method of model test and numerical simulation,the distribution law of the stress concentration factor and the reduction of the ultimate bearing capacity of the pile are studied under the condition of one way,two way and star shaped opening.This paper provides the experimental basis for the application and popularization of the technology of tapered-poled pipe-pile with hole.The main research results are as follows:(1)Experimental study on the stress concentration factor of tapered-poled pipe-pile with hole shows: In three ways of opening,the distribution of the stress concentration factor of the star shaped pile is the smallest,and the pile bearing force is uniform.The stress concentration factor of pile diameter of 5mm is generally lower than that of 6mm pile.The size of the stress concentration factor is mainly affected by the pore size.There is no obvious influence on the distribution of the stress concentration factor and the value of the system.The mechanical behavior of the star shaped pile with the middle diameter of 5mm is the best.(2)Experimental study on ultimate bearing capacity of pile shows: The ultimate bearing capacity of the star shaped pile is the best in the three methods.The ultimate bearing capacity of each pile type with the pore diameter of 5mm is obviously lower than that of the pile with the pore diameter of 6mm.The larger the pore diameter is,the more improved the ultimate bearing capacity of the pile is.The best performance of the ultimate bearing capacity of tapered-poled pipe-pile with hole is the opening of the5 mm diameter taper 1/80 star pile.(3)Numerical simulation of stress concentration coefficient of pile shows: The value of stress concentration in the column section of tapered-poled pipe-pile with hole is higher than that of conical section.The change of the taper of the pile has little effect on the stress concentration factor.The pore size is the main factor that affects the stress concentration factor.The distribution of stress concentration factor is affected by the way of opening.In the way of the three holes,the distribution of the stress concentration factor of the star shaped tapered-poled pipe-pile is the most concentrated.The smaller the pore diameter is,the smaller the stress concentration coefficient is.The smallest value of the stress concentration of each pile is 5mm.The mechanical behavior of the star shaped pile with the medium pore diameter of 5mm is the best.(4)The experimental results show that the numerical value of stress concentration is smaller than that of numerical simulation;However,the distribution law of stress concentration coefficient factor is basically the same,and the stress concentration factor of the column section is higher than that of the tapered section.The larger the diameter is,the greater the stress concentration factor is.The main factors that affect the stress concentration factor are the pore size and the opening mode.Numerical simulation shows that the stress concentration of the pile is consistent with the experimental process.