二维桩土模拟产生的问题

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本人进行二维桩土模拟，采用轴对称模型，加重力SOLVE时弹出“NEGATIVE RADIUS ELEMENT 2259”,但我的建模都是在XY第一象限内。实在不懂此问题的产生？请教斑竹及各位朋友！

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命令流如下：




FINISH
/CLEAR
/PREP7

APILE=0.3
HPILE=16
ASOIL=6
HSOIL=24

ET,1,PLANE82
KEYOPT,1,3,1
ET,2,169
ET,3,172
!KEYOPT,3,3,1
KEYOPT,3,9,0
KEYOPT,3,12,2

MP,EX,1,3.19E7         !桩
MP,PRXY,1,0.2
MP,DENS,1,2500

MP,EX,2,1E4           !土1
MP,PRXY,2,0.35
MP,DENS,2,1600

TB,DP,2
TBDATA,,1000,25,25

MP,MU,3,0.3

!
R,1
R,2,,,1,0.1

RECTNG,0,ASOIL,0,HSOIL
RECTNG,0,APILE,HSOIL-HPILE,HSOIL
ASBA,1,2

WPOFFS,,HSOIL-HPILE
WPROTA,,90
ASBW,ALL

WPCSYS,-1

WPOFFS,APILE
WPROTA,,,90
ASBW,ALL

NUMCMP,ALL
WPCSYS,-1

ASEL,ALL
AATT,2,1,1

LESIZE,4,0.15
LSEL,ALL
ESIZE,0.25

MSHKEY,1

AMESH,ALL

!
ASEL,NONE
RECTNG,0,APILE,HSOIL-HPILE,HSOIL
AATT,1,1,1
LESIZE,11,0.15
LESIZE,12,0.25
AMESH,ALL

LSEL,S,,,11,12,1        !生成目标单元
NSLL,S,1
REAL,2
TYPE,2
MAT,3
ESURF,ALL
ALLSEL,ALL

LSEL,S,,,4,5,1        !生成接触单元
NSLL,S,1
REAL,2
TYPE,3
ESURF,ALL
ALLSEL,ALL

!加约束
LSEL,S,LOC,Y,0
DL,ALL,,UY

LSEL,S,LOC,X,ASOIL
DL,ALL,,ALL
ALLSEL,ALL

!求解
/SOLU
ANTYPE,STATIC
ALLS
FCUM,ADD,,
ACEL,,9.8
DELTIM,0.2,0.05,0.4
AUTOTS,ON
PRED,ON
LNSRCH,ON
NLGEOM,ON
NROPT,FULL,,ON
KBC,0
TIME,1
OUTRES,BASIC,1
CNVTOL,F,,0.02,2,1
NSUBST,100,,20
SOLVE
SAVE

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不好意思问题已解决，忘记加对称约束。