crushed stone base course meaning in English

碎石底层
碎石块底盘

Study on construction technique of cement - stable - crushed stone base course
水泥稳定碎石基层施工技术探讨
Construction quality control of cement stabilized crushed stone base course
水泥稳定碎石基层施工质量控制
Design and control on mixture optimization of expressway cement and crushed stone base course
高速公路水泥稳定碎石基层混合料优化设计与施工控制