Application of Geomaterials in Railway and Highway Subgrade

Application of Geomaterials in Railway and Highway Subgrade

Road and railway subgrade projects are built in saline soil areas and water-rich soft soil areas, and composite geomembrane is laid at the bottom of the subgrade, which can effectively limit the migration of salt and has waterproof effect. Geomembrane can form a barrier layer to limit or even completely block the movement of water in the soil, preventing the water in the foundation from moving upward into the subgrade. Simple geomembrane has thin thickness, low strength and easy puncture damage. Therefore, geomembrane combined with geotextile is mainly used in road subgrade waterproofing, saline soil isolation and other occasions. In railway engineering, sometimes in order to protect the integrity of subgrade materials and structures, geotextiles are also used to separate the subgrade and foundation in waterless areas, as shown in the figure below.

Construction methods and precautions

In order to reduce ultraviolet radiation and increase anti-aging performance, it is best to use the buried method. During construction, first use sand or clay with a smaller particle size to level the base surface, and then lay it. It should not be too tight when laying, and the buried soil at both ends is corrugated. A transition layer of about 10cm is laid on the membrane with fine sand or clay. During construction, the stones should be avoided to directly hit the film, and the film laying and the construction of the protective layer should be carried out simultaneously. The connection between the two cloths and one membrane and the surrounding structures should be anchored by expansion bolts and steel plate beading, and the connection parts should be coated with emulsified asphalt (thickness 2mm) to prevent leakage.

Construction joint treatment is a key process, which directly affects the anti-seepage effect. The general joint methods are: ① Overlap: the overlap width should be greater than 15cm; ② Heat welding: It should be used for slightly thicker geomembrane substrates, and the weld overlap width should not be less than 5cm.