Adding two-way geogrid to the soft soil foundation can improve the overall rigidity of the embankment, the internal stability, and the uniformity and anti deformation ability of the foundation. The two-way geogrid has certain rigidity and better ductility, which makes the load from the road spread, improves the bearing capacity of the foundation, and prevents the uneven settlement of the foundation. The tensile strength of two-way geogrid is large, which can increase the stability of subgrade. Because the two-way geogrid can well adapt to the deformation of the foundation, the composite of the two-way geogrid and the soil will produce deformation under the action of load, which makes the two-way geogrid and the foundation soil bear the external load together. The mesh of the two-way geogrid and the friction between the upper and lower layers of the soil limit the lateral deformation of the soil and increase the shear strength of the soil.

Construction sequence: clearing Subgrade_ →manual laying of two-way geogrid →lapping, binding and fixing →laying of subgrade soil →compaction. First, lay the first layer of grid on the foundation, starting from one end, and advance one by one along the route. The horizontal laying shall be connected with the longitudinal drainage ditch on both sides of the embankment. The two-way geogrid shall be reliably connected. The overlapping side shall be fixed with anchor nails. The laying shall be smooth without wrinkles and shall be tensioned as much as possible. When the grid is laid and positioned, it shall be filled and covered in time, and the construction sequence of laying while backfilling and compaction shall be adopted.

Next, the geotextile shall be laid on the gravel layer, and finally the layered filling and rolling shall be started. The filling shall be compacted layer by layer, and the light roller shall be used to vibrate and roll, and the compaction degree shall be controlled not less than 0.92. When filling, it is strictly prohibited to dump the materials in high lift, and it is not allowed to directly unload the earth and stone materials to the grid. The materials shall be unloaded and leveled at the same time. Before paving the two-way geogrid, the gravel cushion shall not be used as a temporary access road, so as to prevent the cushion from being crushed by the vehicle load, which is not conducive to the construction of the upper grid, and the vehicle shall not be directly rolled on the grid which has been paved and tensioned and positioned.

During the construction, the filling speed of embankment shall be controlled and the observation of settlement and lateral displacement shall be strengthened to prevent the embankment from losing stability. After the completion of construction, the width, thickness and compactness of the two-way geogrid meet the design requirements through field inspection, and the integrity and rigidity of the roadbed after reinforcement are greatly improved. After the upper Graded Crushed Stone Subbase is paved, the construction vehicles can pass smoothly without causing deformation and damage of the subgrade section, which ensures the smooth implementation of the section. After the completion of the project, the pavement is in good condition, without surface cracks caused by uneven settlement and other phenomena, and the treatment effect is obvious.

In order to ensure the safety of the pavement structure, it is necessary to reinforce the soft foundation. However, it is difficult to completely remove the soft soil layer in this section, because the silt layer is thick, the construction period is long and the construction is difficult. Through repeated analysis and comparison, the two-way geogrid is designed to reinforce the soft roadbed in this section, so as to improve the bearing capacity and reduce the uneven settlement.

The construction of two-way geogrid treatment of soft soil subgrade is simple and easy with strong operability, which effectively improves the bearing capacity of subgrade, reduces uneven settlement, enhances the stability of subgrade, and greatly saves the engineering cost. Engineering practice shows that this new technology plays an important role in highway engineering.