quicksand

1. N-UNCOUNT Quicksand is deep, wet sand that you sink into if you try to walk on it. 流沙[also N in pl]

The sandbank was uncertain, like quicksand under his feet. 这个沙丘不结实，像他脚下的流沙一样。

2. N-UNCOUNT You can refer to a situation as quicksand when you want to suggest that it is dangerous or difficult to escape from, or does not provide a strong basis for what you are doing. 危机情形; 难以逃脱的情形; 无法为所做之事提供基本保障的情形[also N in pl]

The research seemed founded on quicksand. 该研究仿佛建立在一盘散沙基础上的。