Hiya Stigmond. Popping corks is typically caused by either
1. having bottled a wine that has not been allowed to sufficiently degas - so the CO2 in the wine has the possibility of nucleating as particles drop out of suspension and that gathering and collecting around the particles provides the gas with enough energy for it to drop out of suspension and so put enough pressure on the cork to pop! OR
2. bottling the wine before it has fully fermented allowing the available yeast to become active again and begin to ferment any available sugars that are still in the wine.
The easy solution for both these issues is ... patience. Once you think the wine is ready to bottle, rack it and wait another two months and when those two months have ended. repeat the action and after those two months have ended, repeat again.
A more mechanical solution for the first problem is to rack your wines using a vacuum pump pulling about 22 inches of vacuum and then before bottling pull the same vacuum for about 20 minutes.
For the second problem you need to allow the gravity of the wine to drop way below 1.000 - say , 0.096 or lower, allow the wine to age a few months, racking every couple of months (this removes the yeast) and then stabilize with K-meta and K-sorbate if you prefer a sweeter rather than drier wine. After stabilization you can then add sugar and the few available yeast cells won't be able to consume that sugar and they won't be able to reproduce...
Last point, You may want to check to see if the size of the cork you are using is the largest you can safely use with the bottles you have. I think a size 9 is wider than an 8 and as long as the bottle tops are relatively dry and the corks are dry (you should NOT soak them) the corks will not slip out. If you feel you need to sanitize corks you simply put them in a colander above an open container of K-meta and allow the SO2 gas to do its job. A wet cork offers less friction.
Hope that this helps.