bear in mind that we are also unclear as to how the black hole operates so all we can do is speculate...
well...i think gravitons absorb energy as they suck the stuff into the hole so as it gets energy, it in turn sucks other particles into the hole and converting the particle into massive gravitons also, which inturn sucks more particles in.
other way of thinkin it would be imagning a rope to the singularity. the bonding between the particles are strong enough to withstand the pull at the begining of the hole, which then is dragged into the hole pulling the other partivles into the hole. when the particles brk halfway thru the hole, the particles which remain unbroken continue to be dragged inside.
also the whirling energy of the star is also one to be remembered, imagine a tub filled with alot of water, water flows in easily with ease. its the same with a black hole, at the point of the black hole where gravitons still exist as gravitons, it is strong enough to pull the particles into the hole. nothin exists in space, a small amt of energy would be enough to drag a particle.
another way would perhaps be applying newtons law, an equal amt of force will exist in the opposite direction when a net force in a direction. since the black hole is pulling the gravitons downwards, the graviton requires energy to stay afloat, not to say outwards, it probably then sucks the energy from the particles and remains afloat. remember that particles in the hole can alternate between a state to another. also as a particle gets sucked into a hole, it will give out a last cry of X-rays, which is massive due the the gravity that splits it apart...maybe the gravitons absorb most of the energy and stay `afloat`.
perhaps the most logical theory would be spacetime. the surroundings BEND into the hole, which causes the particles around it to `slide` into the hole easily, in a vortex like motion, as the hole is spinning.