求翻译：由目标层（多年冻土区块碎石路基适用性）、准则层（外部气候条件、冻土内在因素和路基工程特点）和指标层（12个具体指标）三个层次结构体系组成是什么意思？

Criteria by the target layer (permafrost block gravel roadbed applicability), layer (external climatic conditions, specific indicators of permafrost internal factors and subgrade characteristics) and index layer (12) of the three levels of structural system

By the destination layer (multi-year frozen block gravel roadbed applicability criteria), layer (external climatic conditions, frozen in the underlying factors and Roadbed construction characteristics) and targets a specific level (12 indicators),3 a hierarchy system

By the target stratum (many year frozen earth sub-area broken stone ballast serviceability), the criterion level (exterior climatic conditions, frozen earth intrinsic factor and roadbed project characteristic) and the target level (12 concrete targets) three hierarchical structure system is composed

By the target layer (gravel roadbed in permafrost block fitness), guidelines (external climatic conditions, internal factors and characteristics of subgrade engineering in frozen soil) and indicators (12 indicators) composed of three layers structure

正在翻译，请等待...