Marital separation might be advisable in certain circumstances though it is not something to be considered lightly. Once separation has occurred, it is easier to do it again and again and could contribute to the dissolving of the marriage. However, there are times when separation is advisable. Let's take a look at a few of the examples.
Let's say that a couple is having problems and one of them is physically abusive (women can be abusive, too). Separation would be recommended in order to protect the other person.
Let's say that a couple has children and one of the parents is mistreating the children to such a degree that the safety of the children is a concern. We know that some parents sexually abuse their own children and/or beat them--resulting in injury. In this case, it is strongly recommended that the non-offending spouse leave with the children--or if possible, have the offending spouse leave and/or arrested.
Perhaps a husband or wife is committing adultery and refuses to repent. Then it would be advisable to separate since the other spouse would not want to risk sexually transmitted diseases. Also, such an unfaithful and unrepentant spouse would purposely be violating the covenant promise of fidelity and would in effect be denouncing his or her marriage vows.
Though there can be other situations that would justify separation, the ultimate goal is reconciliation of any marriage. But if such reconciliation cannot be obtained not only is separation recommended but also sometimes divorce should be sought.