All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Him, and that Muhammad, sallallaahu ‘alayhi wa sallam, is His slave and Messenger.
Each ‘Umrah requires an individual [intention for] Ihraam, exactly as every prayer requires its own Takbeerat Al-Ihraam (opening act of prayer, with the utterance Allaahu Akbar (Allaah is Great)). It is not permissible for a Muslim to offer more than one prayer with a single Takbeerat Al-Ihraam. Similarly, he cannot perform more than one ‘Umrah while in the same Ihraam. There is no scholar – to the best of our knowledge – who has allowed this.
In order for the ‘Umrah to be complete, a pilgrim must end his Ihraam by shaving his head or shortening his hair. Only when he does that would he have done an ‘Umrah and no longer be in Ihraam. After that, he can perform another ‘Umrah with the same garb, [but a new intention] for Ihraam.
However, if he neither shaves nor shortens his hair, his first ‘Umrah would not be complete. Accordingly, even if he made [the intention for] Ihraam for another ‘Umrah, this state would be invalid and his Tawaaf would be just a voluntary act of worship, not part of the ‘Umrah. Also, his Sa’ee would not be [accepted as] one of its rites, because it is a pillar of ‘Umrah; and, it is not possible for the pilgrim to perform two same pillars for two different rituals with one Ihraam. Every ritual has its own ruling. Nevertheless, if he ended his Ihraam of the first ‘Umrah, he could go outside the Sanctuary and don Ihraam for another ‘Umrah.
Allaah Knows best.