you must

1-(step: part / part manager / draw your model) first draw your model in one  layer (without  separating layers)

2- then separate that  layer to some  layers (2 or more) "each partition can be one soil layer with any geometry "

guidance :  (step:part / go to tools : partition / face/ sketch/draw your layers )

3-Assign soil properties  to each partition ( the partition = a soil layer)

Best

Hi Dear Hiba 

i think you shouldn't define soil layers separated, you must suppose the layers united and  then separate them with define partition(Geometry).

Best Regards

Alireza

Thanks Ali,but each layer has its properties could you please explain for more details?

you must

1-(step: part / part manager / draw your model) first draw your model in one  layer (without  separating layers)

2- then separate that  layer to some  layers (2 or more) "each partition can be one soil layer with any geometry "

guidance :  (step:part / go to tools : partition / face/ sketch/draw your layers )

3-Assign soil properties  to each partition ( the partition = a soil layer)

Best

I appreciate  your explination Ali ...Thanks