The Biblical grounds for divorce in the case of abuse is that abuse is desertion:
Marriage vows (contracts) can be destroyed by adultery or desertion. We maintain that biblical desertion is not only effected by literal leaving one’s spouse, but also by abuse. Abuse is desertion because it is a refusal to live with one’s spouse as husband or wife in the context of marriage, as defined by the vows of the marriage covenant (297).
Pastor Crippen explains that this type of desertion is “constructive desertion:”
Constructive desertion occurs when one partner’s evil conduct ends the marriage because it causes the other partner to leave. But it is the abuser who is to be construed as the deserter, not the victim. The victim bears no blame (304).
It’s important to remember Pastor Crippen’s definition of abuse here. This is not just someone having a bad day or the typical arguments that all couples have:
Abuse then, is a mentality of entitlement and superiority in which an abuser uses various tactics to obtain and enforce unjustified power and control over another person (18).
Also, we should remember that Pastor Crippen’s conclusion is that abusers, as defined in his book, are unregenerate:
Therefore, we must necessarily conclude that an abuser simply cannot be a Christian, no matter how convincing his masquerade of Christianity might be. His very mindset remains unchanged, as his perseverance in his abuse demonstrates (243).
See also this series on “Grace widows:” http://yoursacredcalling.com/blog/2013/12/grace-widows-hope-and-healing-for-the-forsaken-part-1/
One of the requirements of divorce in Canada is living “separate and apart” for a specified period of time. Interestingly, the courts have ruled that a couple can live “separate and apart” even while living under the same roof. That seems to be a recognition of a situation similar to what Crippen describes.