Reaction force is zero, Stress is not zero.?

[Chen1]

I am modeling an underground excavation, i delete elements to represent the excavated area, then i study the stress distribution on some locations in the model called pillars.

the stress distribution is reasonable, however when i check the RF it is zero. i do not understand why the reaction force is zero?

I need to calculate the total load on the pillar, so in need to take sum of nodal RF.

Thanks.