Study On Mechanical Characteristics And Bearing Capacity Of Multiple Convex Blocks Soil Anchor

In order to improve the bearing capacity of the existing equal-diameter soil anchor,a new multiple convex blocks soil anchor is proposed in this paper.In order to study the bearing characteristics of multiple convex blocks soil anchor,FLAC3 D software was used to conduct numerical simulation analysis from the aspects of ultimate bearing capacity,lateral friction,horizontal displacement and shaft axial force.(1)A cavity forming tool for soil anchor with multiple convex blocks is presented.The tool mainly includes inner tube,air bag,pressure plate,convex block and retraction rubber ring.The air bag inflates to push the pressure plate outward,making the convex block fixed on the pressure plate press into the side wall of the drilling hole,and the rubber ring set on the outside of the pressure plate shrinks when the air bag exhausts,making the pressure plate reset.Therefore,a plurality of cavities are formed on the side wall of the borehole;Move the cavity forming tool along the borehole to a new position and repeat the above process to form a number of cavities on the borehole wall;Put in steel strand;Grouting mortar or cement slurry,solidified to obtain multiple convex blocks soil anchor.(2)In the numerical simulation analysis,the diameter of multiple convex blocks soil anchor is 150 mm and the length of anchor bolt is 6.9m,convex block group are set at 150 mm intervals along the length direction of anchor bolt,there are 32 convex block groups in total,and each convex block group is distributed with 8 convex blocks at equal intervals in the circumferential direction,totaling 256 convex blocks,each block is 30 mm high,35 mm axial length and 35 mm circumferential length.Numerical simulation analysis of multiple convex blocks soil anchor and equal-diameter soil anchor was carried out at the same time,and the simulation results showed that: the ultimate bearing capacity of multiple convex blocks soil anchor of the same length is increased by 63.6% compared with that of equal-diameter soil anchor;the load shared by the convex block reaches 76% of the total load;under the ultimate bearing capacity of equal-diameter soil anchor,the head displacement of multiple convex blocks soil anchor decreases by 51.4%compared with that of equal-diameter soil anchor.(3)The control variable method was used to study the influence of the spacing of anchor bolt axial convex block group and the number of convex blocks on the convex block group on the bearing capacity of multiple convex blocks soil anchor,a total of 18 groups of comparison models were set,and the numerical simulation was carried out with FLAC3 D software to compare and analyze the soil anchor displacement and ultimate bearing capacity of each model group.The results show that when controlling the same number of convex blocks on the convex block group and changing the convex block group spacing,the number of convex block groups decreases and the number of convex blocks decreases with the increase of the convex block group spacing,and the ultimate bearing capacity of multiple convex blocks soil anchor decreases;when the convex block group spacing is the same,the number of convex blocks on the convex block group is changed,with the increase of the number of convex blocks on the convex block group,the ultimate bearing capacity of the multiple convex blocks soil anchor increases,but the increases are different.When there are enough blocks on the multiple convex blocks soil anchor,the anchor tends to be equal diameter anchor,and its ultimate bearing capacity increases little.It is concluded that in a certain range,the ultimate bearing capacity of multiple convex blocks soil anchor increases with the increase of the number of convex blocks on the surface of anchor bolt.(4)According to the displacement nephogram and stress nephogram output in FLAC3 D software,the displacement and stress variation of soil mass around the multiple convex blocks soil anchor under horizontal drawing load are analyzed.When the drawing load is small,the lateral friction resistance of the multiple convex blocks soil anchor bears most of the load and plays the main role;at this time,the convex block has little squeezing effect on the surrounding soil,the soil compressive stress is small,and the anchor head displacement is small;With the increase of drawing load,the displacement of anchor head increases,and the load borne by the convex block is gradually greater than the lateral friction resistance,at this time,the convex block continuously compresses the soil mass,and the compressive stress of the soil mass is larger.(5)Control variable method was used to study the influence of different length and buried depth of anchor on the bearing characteristics of multiple convex blocks soil anchor,12 groups of comparison models were set and analyzed according to the load-displacement curve output by software.The results show that the ultimate bearing capacity of multiple convex blocks soil anchor increases gradually with the increase of anchor length and embedment depth.Figure [56] Table [13] Reference [61]...