The geogrid materials and testing methods used in pavement reconstruction are the main problems to be solved in the process of pavement improvement. When the old road surface is relatively complete, due to a certain number of years of use, the service performance of the road surface is weakened, so the old road surface can be used as the subbase and paved with geogrid. It can make full use of the old road's more complete pavement, save cost and investment, and achieve the purpose of improving the use performance. When the design thickness of semi-rigid base is greater than the maximum thickness of construction rolling, rolling shall be carried out in layers. Generally, the maximum thickness is 20cm, and the thickness of semi-rigid base is slightly larger than that of rolling, so geogrid can be considered. So the semi-rigid base material can be saved and the project investment can be reduced.
The cement pavement will have transverse and longitudinal cracks due to maintenance, moisture and other reasons. First of all, if the cracks are large, it is necessary to grout first and then pave the geogrid on the cracks. The distance between the two sides of the geogrid and the cracks is 20cm or more. Secondly, if the crack is small, directly lay the geogrid. Pay attention that after laying the geogrid, it is better to pave it in full width, and then fix it with the cap steel nail. Basically, for the whole 8-meter-wide Road, a total of more than 8 capped steel nails shall be nailed on both sides of the geogrid, and then the sealing layer or asphalt layer shall be spread.
For the pavement with a large number of cracks, the method of paving Geogrid on the top of the original pavement can be adopted。 Fundamentally solve the problem of crack upward expansion of old pavement。 If the cracks are large, the original pavement shall be grouted and then geogrid shall be laid。 For different distribution of pavement cracks, different laying methods can be adopted。 If the crack distribution is sparse, geogrid with a certain length and width shall be laid according to the influence range of stress。 The road section with complex stress distribution can be paved in full width。 When the widened part is soil foundation, there will be longitudinal cracks at the joint of the old and the new。 The geogrid can be located on the top surface of the original road surface and the new soil foundation, so that it can be dispersed to a larger plane。 When the old road is widened, the widened subgrade shall be paved with fly ash semi-rigid base material。
The reflection crack itself has little effect on the performance of the covering layer, but the negative effects of environmental factors (rain, snow, oxidation, dust) often make the cracks expand rapidly and shorten the service life of the covering layer. In order to effectively slow down the reflection speed of old cement concrete pavement cracks or reduce the thickness of asphalt overlay, researchers at home and abroad have carried out a lot of tests, which not only accumulated successful experience, but also learned many failed lessons. In order to prevent reflection cracks, the method of thickening asphalt overlay is adopted abroad. However, there are some disadvantages of simply increasing the thickness of pavement layer: on the one hand, the increase of the thickness of overlay layer is limited by the height of street; moreover, the substantial increase of the thickness of overlay layer will increase the cost of pavement.
In addition, in summer, asphalt mixture will easily lead to rutting under high temperature, thus losing the advantage of the old cement concrete slab as a solid foundation and thin surface. Therefore, it is not advisable to use the method of thickening asphalt overlay. In view of this situation, on the basis of consulting a large number of data, theoretical analysis and demonstration, it is decided to lay the glass fiber grid reinforcement layer on the old cement concrete pavement, and then lay the asphalt concrete surface layer on it. The pavement paved by this method can prevent the reflection of the base cracks, reduce the ruts of the pavement, and extend the service life of the pavement. The glass fiber grid has the characteristics of high tensile strength, low elongation, no creep, good compatibility with asphalt mixture, stable physical and chemical properties, high temperature resistance, strong locking and strong limit effect. Its main function is to transmit the axial load uniformly. The stress of reflection crack changes from vertical to horizontal.
I believe that after reading the above content, you should also have some understanding of how to solve the road cracks in figure Gehan. I hope it will help you.