According to the actual situation of the construction site, the reasonable determination of the rock filling collection site is carried out. The maximum dry density and the optimum water content of the filler are determined under the construction condition, which is also the standard to measure the compaction degree in the construction of roller compacted filler. Select the position of the slope of mesh bag packing masonry construction, and put the green grass seeds on the slope into the mesh bag on the slope. When unloading, the spacing between the tool and the slope should be controlled within 1.5m. If the geogrid is not covered with the filler, the machine should not drive above it to avoid disturbance to the lower grille. When paving, manual + mechanical method can be selected to ensure that the paving thickness is the same, with a flat surface, and more than 3% of the cross slope. In the construction of mechanical paving, it is required that the driving direction of the machine be parallel to the slope, and that the car should not be parked in the grille without filler. When the distance between machinery and slope is less than 1.5m, the paving method can be changed to manual. Rolling construction should be carried out in time after paving and leveling each layer of filler. Rolling construction machinery is mainly vibratory roller, according to the sequence of "light pressure - heavy pressure, middle grille - tail - slope position" construction. When the distance between the rolling machinery and the slope is only 1 m, small machinery should be selected for rolling construction. It is required that the slope be first lightly compacted and then gradually compacted to the middle of the route, and disturbance of the slope surface is strictly prohibited. According to the design requirements, the compactness of subgrade should be controlled above 95%.
6. Transition Treatment of Different Settlements of Subgrade
1. Subgrade filling and excavation joint. The two-way geogrid over 40KN/M is chosen as the main construction method of subgrade filling-excavation joint. The general geogrid type is GSZ60-60. In roadbed widening construction, geogrids should be set at the step position where the old roadbed contacts with the new roadbed and the top layer of the roadbed, so as to effectively enhance the cohesion between the new and old roadbed, and ensure the rapid formation of the overall structure of the new and old roadbed under the condition of reduced uneven settlement and lateral displacement.
2. Widening the joint of old and new roadbed. Usually, when the embankment filling height is over 3 meters, the steel-plastic composite grille should be set at the position 20 centimeters away from the top of the embankment to ensure that the ultimate longitudinal tension of the steel-plastic geogrid is above 60 KN/M, the ultimate transverse tension is above 20 KN/M, and the elongation must be controlled below 5%.
Key Points of Quality Control
1. The quality of the material itself needs to be guaranteed, and regular channels should be adopted to purchase goods to ensure that there are regular quality inspection reports. The physical and mechanical properties of the materials are sampled after purchase, and the quality control of the materials is well done.
2. The construction site should do a good job of site leveling and compaction, prevent the occurrence of hard objects causing damage to the grille, and deal with uneven areas.
3. Attention should be paid to the quality control of the effect of grid laying. Reinforcement materials should be flat and compact, avoid overlapping and distortion, and the laying direction should be vertical to the vertical wall. Its paving length, width, connection mode and strength should meet the design requirements.
4. Filling blocks should not be too large, generally not more than 2/3 of the thickness of layers; paving thickness should not be less than 30 cm, after compaction should not be less than 15 cm, compaction degree should also meet construction requirements.
5. To sum up, whether the overlap of old and new roadbed is reasonable will directly affect the quality of roadbed widening in road reconstruction. The most common way is to excavate steps on the slope of the old roadbed or lay geogrids on the steps to promote the new and old roadbed to form a whole. When widening the highway roadbed, the settlement deformation of the new widened roadbed is more serious because of the problems of compaction deformation of the embankment and foundation settlement. In this case, the settlement difference between the new and the old roadbed will be increased. The application of geogrid reinforcement technology in highway roadbed construction can effectively reduce the settlement of new and old roadbed, improve the stability of roadbed, and provide a reliable guarantee for the improvement of the overall quality of highway engineering construction.
With the rapid development of social economy, the traffic volume of our country is increasing. In order to meet the current traffic demand, we must widen and rebuild the highway with large traffic volume. In highway subgrade construction, geogrids are often used as reinforcement materials for reinforced earth structures or composite materials. They are generally divided into four categories: plastic geogrids, steel-plastic geogrids, glass fiber geogrids and glass fiber polyester geogrids. Geogrid is a square grid plate formed by stretching polymer. Geogrids can be divided into different types according to different criteria. For example, according to the material quality, they mainly include two kinds: plastic geogrids and glass fiber grids. According to the processing method, it is divided into single and two-way geogrids. Geogrid is mainly used in embankment, retaining wall, soft foundation and other aspects. The application of this technology can effectively improve the stability and bearing capacity of subgrade and other structures.