In recent years, the increasing demand for road transportation has greatly promoted the development of cement concrete roads. Some of the early-built cement pavement design standards are low and the use time is long. It is inevitable that various diseases such as damage and fracture will occur, which cannot meet the growing transportation needs. Reinforcement and widening of old roads, road reconstruction and other projects have sprung up one after another. When using old roads for reconstruction, if the width is insufficient, the old roads need to be widened unilaterally or bilaterally. Subgrade junctions are prone to uneven settlement, reflection cracks, and broken phenomena. How to solve these problems, improve traffic quality and traffic safety, and extend road life are the key points in road reconstruction.
1. Problems arising from the handover of new and old roads
At the junction of the new and old roadbeds, due to the uneven settlement of the new and old roadbeds, the original concrete slab is deformed under the action of temperature stress and load, resulting in the reflective cracking of the asphalt-like surface layer at the original joint. In order to solve these problems, many projects at home and abroad use reinforced technology to improve the performance of pavement. Among them, the use of geogrids for road reconstruction can basically reduce or delay the occurrence of pavement diseases. The role of development.
Second, the generation of reflective cracks when the new and old roads are handed over
Reflective cracks are mainly due to the combined effect of road temperature changes and road loads. Reflective cracks caused by temperature changes are called temperature-type reflective cracks, and reflective cracks caused by loads are called load-type reflective cracks.
3. The function of steel-plastic geogrid
Steel-plastic geogrid has the characteristics of high tensile strength, low elongation, no creep, good compatibility with asphalt mixture, stable physical and chemical properties, high temperature resistance, interlocking and restrictions, etc. Its main role is to reflect The crack stress is changed from vertical to horizontal. At the same time, the steel-plastic geogrid has higher tensile strength and tensile modulus, so it can spread the load and stress evenly in a larger area. This effectively prevents the occurrence of reflective cracks caused by cracks in the base layer of the road surface. Its role is mainly manifested in:
1. Disperse the cracks, so that the stresses that cause the cracks turn to the horizontal. The grid diffuses the stress caused by the repeated action of temperature and load in the asphalt layer to a larger range, so that the wide cracks are dispersed into several small cracks, which delays the diffusion and penetration of the cracks. The grille provides sufficient rigidity to change the direction of the crack. The crack propagates to the bottom of the interlayer, and then turns horizontally to prevent it from expanding vertically upward, improving the crack resistance and fatigue resistance of the pavement.
2. Resistant to deformation. When the local non-uniform external force acts on the grid, the mesh will be deformed accordingly, and its restraining effect is also displayed. Therefore, the geogrid has a good adaptability to the non-uniform load and transmits it uniformly.
3. Improve toughness. This kind of grid can play a more dense and continuous role than the steel bar. It will not lose the bearing capacity until the fiber breaks or is pulled out, showing higher toughness. Since the mesh of the steel-plastic geogrid restraint layer has the same shape, the shear resistance between the upper and lower particles is not affected, and the rigidity, tensile strength of the grating, and the interlocking effect of the mesh are complicated. The local displacement and deformation caused by the compaction of the load are prevented, thereby enhancing the compaction effect of the granular material.