pull the rug out from under your feet(The Government of China has once again reminded all private entrepreneurs that no matter how rich and successful you are it can pull the rug out from under your feet at any time.Alex_Odeychuk)
soften up the ground(Artillery from both sides constantly fired shells on the trenches, a rain of steel that attempted to shatter the morale of the defenders and soften up the ground for future attacks.4uzhoj)
the bottom has fallen out of something(You realize that the bottom is falling out of the fight game? – Вы понимаете, что бокс будет не в моде? / Харди "Власть без славы" Bobrovska)
the bottom has dropped out of something(He was wondering how the fact that the bottom was going to drop out of local street-railways would affect Cowperwood so seriously. – Он недоумевал, каким образом близящийся крах местной трамвайной компании может серьёзно затронуть Купервуда. / Драйзер "Финансист" Bobrovska)
