In order to prevent the reflection cracks, the method of thickening asphalt overlay is often used in foreign countries, but the method of increasing the thickness has its disadvantages: on the one hand, increasing the thickness will increase the cost of pavement; moreover, under the high temperature in summer, the high temperature creep of asphalt mixture is easy to produce rutting, and there is no advantage of strong base and thin surface produced by old cement concrete slab as base One method is not advisable for high-grade highway.

In view of this situation, domestic and foreign road engineering experts have carried out a lot of research. The research results show that a layer of stress reinforced interlayer with high elastic modulus is paved between the old cement concrete pavement and asphalt overlay to absorb or cushion the stress concentration of cracks, which has a certain effect on restraining the generation and diffusion of reflection cracks. According to code for maintenance of highway cement concrete pavement, measures for reflecting cracks include laying geogrid, paving geotextile and pasting modified asphalt felt. Therefore, it is recommended to pave geogrid in this scheme. The grid has good high temperature resistance and will not deform when paving hot asphalt concrete, However, the construction requirements are relatively strict. Before laying the glass fiber geogrid, the old cement concrete pavement should be leveled first, so as to avoid hollowing under the grid and causing damage to the asphalt pavement. When paving the asphalt layer, it is strictly forbidden to turn around on the geogrid to prevent crushing the geogrid used in highway.

The pavement structure of the design scheme is simple and clear. In addition to paving 15cm asphalt concrete, only a layer of glass fiber and modified asphalt felt are added. The price of glass fiber is about 15 yuan / m2, so the cost of the whole structure is relatively cheap, and the construction technology is not complicated. Adding a layer of glass fiber and 15cm asphalt concrete does play a role in preventing reflection cracks, but the treatment requirements for the old cement board are high. In addition to the treatment of conventional structural diseases (refer to the technical specification for highway maintenance (jtj073-96 for the treatment of various diseases), the old concrete slab should also be reconstructed according to the special situation of the old road overlay structural layer The corresponding index requirements are put forward.

Simulation of deformation mode of interface between Geogrid and soil under dynamic load, there are four deformation modes of contact surface between Geogrid and soil

1. Bonding; 2. Dislocation; 3. Detachment; 4. Embedding. Generally, the embedding is ideal, and the construction effect is obvious, which meets the requirements of the design scheme. However, there are many unsatisfactory places in the actual construction of our country, so it is necessary to design and produce the geogrid according to the specific situation of our country in order to meet the expected design requirements.

Bonding mode: the geogrid can bond the asphalt surface layer, so that it is not easy to occur overall displacement. In this way, the high temperature stability of asphalt pavement is improved, and the probability of rutting is reduced. Under high temperature conditions, the deformation will not occur and the service life of asphalt pavement will be prolonged.

Dislocation mode: in the geogrid reinforced cushion, because of the great difference of elastic modulus between the two materials, under the condition of their common force, the inconsistency of deformation will cause the mutual dislocation of the two materials.

Separation mode: in order to avoid the end transverse rib being broken due to uneven stress at the end of geogrid during tensioning, the end of geogrid shall be bound with short pipe or short reinforcement head, and the end shall be wrapped on the short pipe and reinforcement head at least two times.

Embedding mode: the geogrid is embedded into the embankment as an embedded area, and the mutual sliding between the geogrid and the embankment can not be well considered. The stiffness of the grid is only added. However, this simulation may be accurate enough when the vertical stress is dominant.