Geosynthetics are separated by placing them between two different materials, or between different sizes of the same material, or between foundations. When external loading occurs, it is not intermingled or lost, maintaining the overall structure and function of the material. In general, the roadbed and roadbed are constructed sequentially, and the road begins to operate after the completion of the construction. The roadbed, roadbed materials and general materials are mixed together because of the passing of load pressure and rainwater. Although this is a local phenomenon, it weakens the original design strength, drainage and filtration function. In order to prevent this phenomenon, geosynthetics can be set between two kinds of materials which do not have the characteristics of mixing, but maintain a unified role.

In Railway Engineering, geosynthetic materials are used to maintain track stability and reduce maintenance costs. In road engineering, it can play the function of permeable membrane to prevent the soft soil layer from invading the gravel of the roadbed, otherwise it will cause mud and mud, and finally reduce the design thickness of the roadbed and roadbed, resulting in road damage. For foundation reinforcement, the new foundation can be separated from the original foundation, which can enhance the bearing capacity of the foundation, and is conducive to drainage and acceleration of soil consolidation. The permeability of geosynthetics for isolation should be greater than that of the isolated soil, and the geosynthetics should also have sufficient wear resistance under dynamic load. When there is no water flow between the isolated material or the soil layer, it is also impossible to use water and soil membrane.