bedrock; foundation rock
Technical term used in geology and civil engineering for the solid rock underlying surface materials.
Investigation of the foundation rock is essential for dam construction.
The bedrock in this area is made of granite.
岩盤 is a general term for rock mass or bedrock, while 基礎岩盤 specifically refers to the rock that serves as a foundation for structures.
Compound of 基礎 (foundation) and 岩盤 (rock mass, bedrock).