第四章 天然地基上的浅基础
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Transcript of 第四章 天然地基上的浅基础
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Shallow foundation on natural groundGB50007-20021 2 3 4 5 6. 7.
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() 5m5m
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3023b1.5b5m
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1 2 ()3 Shallow foundationRigid foundationSpread foundationMat foundationPile foundationIndividual footing(pad foundation) Strip footingCross strip footingBox foundation
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2 Rigid foundation ()()Spread foundation,1.1 1.5
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3 1: ,Individual footing, pad foundation
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2 , :,Strip foundation
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3 :,,
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4 ,,,,Mat foundation
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5
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6
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2 ():(1),(2),(3)()()
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3 :
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4 5 F G
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6
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1 (1) (2)2 3 SGK SQiK SQ1K
- fakpcrpu
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fa=Mbb+Md md+Mcck fa : p1/4=NB /2+Nq d+Ncc 2Mb Nb6m6m3m3m
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( D50cm, 10cm
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1 ,: F
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L/ H=1~2
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(1) ,(2) ,
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1 ,,2 (1) ()(2) (3) ,
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,h1IIh1< 2m h1=2m~4m,h1>4 m () I II III IVh1h1
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Pingo
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1 1 () ,,
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1 1928-1929 Casagrande,:45cm,13cm,=8%~12%, 60%~110%, 13cm
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(2) ,.0oc,-0.5~-30oc
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:,,+(),,,,
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2 1 2 3
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3 P32-33,25
Z0, 1.0m 2.0m 2.5m
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4 dmin z0 t dfrZ0 dfr
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4 /(%)hwZd (h -z)zzdh
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4 dmin > zd hmaxZd hmax
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693
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5 pk fa
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1A*Fk+Gk Gk=Ad, =20KN/m3*fa*Fk+Gk =Afa
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(2) ,blA, bb0+2htg, l l0+2htgd h+0.1mb, l h=45o (1:1) 30o (1:2)Fll0b0bbth
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Fhbb0+2htg h:b 60~70cm, b024,37,48cm b 50cm
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1A1(2)A=(1.1~1.4) A1 Abl
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.
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,() 1
b>6m 6m, < 3m 3m fa=Mbb+Md md+Mcck fa :
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2 Dbfa(1)
(2)
* *(,) *e>b/6, pmin
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2 (2)
* *(,)
*e>b/6, pmin
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3a 0.75b25%*A*l, b, A*
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() 1 pk=(Fk+Gk)/A 2 c03 p0=pk-c04 Es1/ Es2z/b
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5
2196
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() 1 5.3.4
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2 (1):,
:,e-p,logp, Es GB 50007-2002 K.0.1-2(2)S=Si s0.025S
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Ai = p0(izi- I-1 zi-1)si=Ai/Esis=s si
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(3)S=sSs,,s=1.4~0.2, (1)Es,,(2)p0/fk
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3 ,(p0)(p0),-
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() 1
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2 (2)(1)
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(1) G1.2 G1.35Q1.00.9(2) G1.00.9
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2 F1=A1pj[V]=0.7hpftamh0Alamamhp
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3 baIIIa1
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IIIIII
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Kobe earthquake, 1995()
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Concrete-frame structure with a mid-story collapse
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() () 1 pE=sf s=1~1.5(~),8-8 ,
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2 (),(1) GE, G FE M FE
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(2)
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3 FEFE=Geq Geq = Ge Geq =0.85 Ge~
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:. ().12 (1) (2) (3):..:M=logA,
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Tg ,**,,max
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4 bb/45
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() liquefaction1 :,,(),,,.,,,. u = 3, , C,
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2 (1)* Q3(10000),* >10~16%, 7~9* du,dw() : du > 6~9m, dw > 5~8m,
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2 (2),N63.5,,ds dw ds>dwcN0
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N0 7 8 9 6 10 16 8 12 /
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30030030080 150 150
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120200240 60 170240 60 150 150
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e=0.1Il=0.2w=0.1n=6()
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1
(A)2.00m(B)1.00m(C)1.40m(D)3.50m
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2.(A)180kPa(B)200kPa(C)250kPa(D)150kPa
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.3.(A)100kPa(B)80kPa(C)95kPa(D)112kPaw=38%;95kPaf 0.83279.0kPa
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4.1.51.7(A)220kPa(B)250kPa(C)300kPa(D)175kPafa=Mbb+Md md+Mcck5.2.5 k=18, Mb0.43, Md2.72, Mc=5.31, =9kN/m3, m=18.92kN/m3fa=0.4391.7+2.7218.921.5+5.3125217kPa
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5. 1.51.7(A)230kPa(B)210kPa(C)300kPa(D)175kPa
179.2kPab0.3 d=1.6,
fa179.2+1.618.921.50.5=209.5kPa
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6kPa)(A)50(B)100(C)70(D)8018.91.2+0.31994.7=70.7kPa
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7.P0)kPa):(A)155(B)166(C)177(D)200(300+19.61.71.5)/1.7-18.91.5177kPa
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8.kPa)(A)72(B)67(C )83(D)56z/b>0.5, 323oz(1771.7)/(1.7+24.7tan23o 53kPa
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9.(kPa)(A)100(B)120(C)140(D)15079.0kPa , d=1.1 m=11.4kN/m3fa79.+1.111.46.50.5=154.2kPa
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10.s=1.0)(cm):(A)20(B)30(C)10(D)35
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1 ABCD
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2?ABCD
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3 ABCD
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45000m5030m5060m4900m105A d=1.0mB d=1.3mC d=1.6mD d=1.45m
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5A d=1.0mB d=1.3mC d=1.6mD d=1.45m
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6 pe?A B C D
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5500