The former use provides for equalization of stress as well as segregation of subsoil and fill; the later reduces cracking of the road base and asphalt surface and reduces the amount of asphalt required for good stability of the road surface.

• 前者可使应力均衡,也可隔离下层土与填充土；后者可减少路基及沥青面的断裂,降低为保证路面稳定所需的沥青用量