기존의 엄지말뚝 간격을 3.4m로 늘리고하고 strut의 간격을 줄였습니다.

그런데 step 4에서 계산을 다시하라는 문구가 나오는데요. 그러나 말뚝의 간격을 3.1m까지로 할 경우에는 원활한 계산이 수행됩니다. 말뚝의 간격와 strut의 어떤 연관이 있는지.. 검토 부탁드립니다.
PROJECT 환기구관연결부

SOIL 1 매립토층
1.8 0.9 0 30 1500 0 0
2 풍화암
2 1.1 3 33 4000 0 0
3 연암
2.1 1.6 5 35 6000 0 0
4 경암
2.3 1.8 8 40 8000 0 0
PROFILE 1 3.79 1
2 9.31 2
3 17.19 3
4 35.0 4

VWALL 1 25.67 0.01348 0.000215 2.1E+07 3.40 0.0 0.0 0 0

STRUT 1 0.2 0.02355 17.045 2 0 0 0 0
2 2.51 0.01348 17.045 2.5 5 0 0 0
3 4.11 0.01348 17.045 2.5 5 0 0 0
4 5.51 0.01348 17.045 2.5 5 0 0 0
5 6.71 0.01348 17.045 2.5 5 0 0 0
6 8.91 0.01348 17.045 2.5 5 0 0 0
7 10.31 0.01348 17.045 2.5 5 0 0 0

anchor 1 14.61 0.0005067 30 4 4 21.455 0 0
2 17.61 0.0005067 30 4 4 21.455 0 0
3 20.11 0.0010134 0 4 2 5 0 0
4 22.11 0.0010134 0 4 2 5 0 0

Division 0.5

STEP 1 to 0.7 and strut 1
output 0
iteration 10 0.1
rankine 1.0 0.0
surcharge 1.0
excavation 0.7

STEP 2 strut 1 and to 3.01
const strut 1
excavation 3.01

STEP 3 strut 2 and to 4.61
const strut 2
excavation 4.61

STEP 4 strut 3 and to 6.01
const strut 3
excavation 6.01

STEP 5 strut 4 and to 7.21
const strut 4
excavation 7.21

STEP 6 strut 5 and to 9.41
const strut 5
excavation 9.41

STEP 7 strut 6 and to 10.81
const strut 6
excavation 10.81

STEP 8 strut 7 and to 15.11
const strut 7
excavation 15.11

STEP 9 anchor 1 and to 18.11
const anchor 1
excavation 18.11

STEP 10 anchor 2 and to 20.61
const anchor 2
excavation 20.61

STEP 11 anchor 3 and to 22.61
const anchor 3
excavation 22.61

STEP 12 anchor 4 and to 24.17
const anchor 4
excavation 24.17
ground settlement
depth check

END