Calculation method for ground bearing capacity of pile-supported reinforced cushion embankment

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1 41 3 ( ) Vol.41 No Journal of Central South University (Science and Technology) Jun , 2 1 ( ) 1 U A (2010) Calculation method for ground bearing capacity of pile-supported reinforced cushion embankment ZENG Ge 1, 2, ZHOU Zhi-gang 2 (1. College of Traffic and Transportation, Changsha University of Science and Technology, Changsha , China; 2. College of Civil Engineering, Hunan City University, Yiyang , China) Abstract: Based on the mechanic action mechanism and influence element of ground bearing capacity on pile-supported reinforced cushion embankment, considering synthetically foundation stiffness, rate of replacement, spreading action of cushion stress, pulling force of geogrid, earth suppress action of side slope, the calculation formula and inspection method were presented considering ground bearing capacity as pile compound foundation capacity under embankment and bearing capacity which is increased by reinforced cushion and earth suppress action of side slope on ground bearing capacity. The results show that ground bearing capacity increases with the decrease of foundation stiffness, the increase of rate of replacement, geogrid layer number and spreading action of cushion stress. Pulling force of geogrid is a chief element for increasing ground bearing capacity. Key words: pile-supported reinforced cushion embankment; ground bearing capacity; superimposing method; foundation stiffness; rate of replacement ( ) (07jj6093) (kfj080109) (1969 ) zengge6906@163.com

2 [1 5] [6 7] [8] [9] [5, 10 13] Catenary Carlsson BS8605 SINTEF d s ( ) [5, 14 15] 1 Fig.1 Scheme of pile-supported reinforced cushion embankment

3 1160 ( ) 41 [16] Ra fsp,k = m + β0β1β2(1 m) fs,k (1) Ap f sp,k (kpa) m R a (kn) A p (m 2 ) β ~0.95 β 1 1.2~2.0 β 2 1.1~1.6 f s,k (kpa) R a 2 k Ra = up qsii l + qpap (2) i= 1 u p (m) k q si q p i (kpa) l i i (m) f 1 f 2 f 3 2 (p T p z ) B L d s B=0.866sB=s [17] f 1 (L/B 10) f 1 2pZ tanθ f1 = γ Z B+ tanθ (1 L/B 10) f pz tan θ( B + L) + 4 pz tan θ f 1 = ( B+ tan θ)( L+ tan θ) γ Z Z (m) γ (kn/m 3 ) θ ( ) p (p 1 ) (p 2 ) (1) (p 1 ) p 1 n γ ihi i= 1 (3) (4) = (5) n γ i h i (2) (p 2 ) α q A(A=L) H p2 = q/( L+ 2H tan α) (6) p p = p1+ p2 (7) f 2 (L/B 10) f 2 2 Fig.2 Forces acting on geobelt reinforced cushion 2nT sinα0 f2 = (8) K( B+ (1 L/B 10)

4 f 2 2nT sin α0( B + L + 4Z f2 = K( B+ ( L+ (9) 3 α 0 ( ) 10 ~ 17 [18] θ ( )( ( ) ( ) 26 [4, 19] ) K 2.5 [19 20] n f 3 f 3 (1) n (2) f 3 (L/B 10) f 3 nt cosα0 2 ϕ f3 = tan 45 + KZ 2 (1 L/B 10) f 3 nt cosα0 2 ϕ 1 f3 = tan 45 + KZ B/ L ϕ ( ) 2.3 (10) (11) H 1/2 D f 4 f 4 = η d γ m ( D+ Z 0.5) (12) η d D 1/2(m) γ m (kn/m 3 ) 2.4 f f = fsp,k + f1+ f2 + f3 + f4 (13) p f (14) f (kpa) 3.2 p k +p cz p 0 (15) p 0 =f sp,k + f 4 (16) p cz (kpa) p k (kpa) p 0 (kpa) p k p 4 k BLp = (17) ( B+ ( L m 12.5 m ~5.1 m 1.5~3.5 m d 0.6 m s 1.5 m R a 400 kn 0.6 m 1 20 cm 2 20 cm

5 1162 ( ) B=1.299 m L=27 m γ m =19.0 kn/m 3 γ =22.0 kn/m 3 α =30 θ=36 α 0 =17 φ=6.95 T=107.0 kn/m K=2.5 m=0.145 β β β η d (1) f sp,k (3) (8) (10) (12) f 1 f 2 f 3 f 4 p f p k +p cz p f kpa (80.00 kpa) 7.14 p kpa Table 1 Physical and mechanical indices of soil layer h i / m γ i / (kn m 3 ) ω/% c/ kpa φ/( ) f s,k /kpa 1 0.5~ ~ ~ ~ Table 2 Calculation and inspection of bearing capacity of geobelt reinforced cushion f sp,k /kpa f 1 /kpa f 2 /kpa f 3 /kpa f 4 /kpa f/kpa p/kpa p f 3 Table 3 Calculation of bearing capacity of soil layer under reinforced cushion f sp,k /kpa f 4 /kpa p k /kpa p cz /kpa p/kpa (p k +p cz )/kpa p k +p cz p 0 4 Table 4 Elevated ground bearing capacity for every factor /kpa /%

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