The original urban roads are mostly cement concrete pavement. With the increase of service life, road traffic and vehicle load, the damage of old cement pavement structure is more and more serious. How to repair the old cement concrete pavement has become a problem to be solved. It is not only time-consuming and laborious to reconstruct the traditional slab pavement, but also has many people's opinions.

The good inlaying and occluding effect between cement soil two-way plastic geogrid and soil particles makes it more flexible in engineering application, which is different from other forms of geogrid, and also reflects the superiority of cement geogrid. The two-way Plastic geogrid of cement and soil has the advantages of small volume of excavation and replacement of fill, eliminating the disadvantages of conventional replacement method, large volume of fill, large amount of land occupied by excavation and replacement of waste soil, and soil erosion and environmental damage caused by disposal of waste soil after construction. Because of its simple process, low cost, convenient construction and ideal effect, the construction period can be shortened to a certain extent, It has gradually become the first choice of foundation treatment for multi-layer and middle high-rise buildings.

However, due to the particularity of two way plastic geogrid and its wide application, the current design theory is mainly based on semi empirical results. Based on the practice of cement soil two-way plastic geogrid structure composite foundation, this paper analyzes and studies its reinforcement mechanism, construction technology, quality control measures and application benefits.

The reinforcement mechanism of cement soil two-way Plastic Geogrid to foundation soil is the interaction between geogrid and soil, which can be summarized as follows: (1) friction between geogrid surface and soil particles; (2) passive impedance of soil particles to grid ribs; (3) inlay and occlusion of geogrid holes to soil. The above three kinds of actions can fully restrain the lateral displacement of soil particles. The mosaic and bite action between cement soil two-way plastic geogrid and soil particles is more superior than other forms of geogrid, thus greatly increasing the self-supporting stability of soil. At the same time, due to the existence of three kinds of actions, the pull-out resistance of the two-way plastic geogrid in the soil or the reinforcement effect of the grid on the soil are also significantly improved.

The main function of two way plastic geogrid is to even the upper settlement and reduce the amount of lateral deformation, limit the lateral displacement and reduce the differential settlement, so that the stress deformation of the lower pile is more uniform, reduce the stress concentration of the pile, and then increase the bearing capacity of the foundation. When the foundation may be damaged by punching (wedging), the two-way plastic geogrid will prevent the failure surface and improve the bearing capacity of the foundation. When the foundation may produce large deformation, the two way plastic geogrid increases the lateral limit and prevents the lateral extrusion due to its bearing tension and friction with the soil, so as to reduce the lateral deformation and increase the stability of the foundation. The bi-directional Plastic geogrid of cement soil makes full use of the high bearing capacity of cement soil and the side limitation of two way plastic geogrid, and greatly displays the performance of materials.