The state has always attached great importance to the construction of expressway, especially in the case of rapid economic development, paying more attention to the construction of road closure projects. However, some roads have also experienced settlement, which occurred when many roads were just put into use. Especially the filling part. The main feature is that the higher the filling position, the more serious the settlement in this section. Even the road will be broken. Once it breaks, the road section can't be used any more and the traffic is interrupted. Therefore, in order to ensure the normal road traffic, it is necessary to deal with the filling problem. Understand subgrade filling technology and control construction quality. The construction requirements before 1 filling (1) shall be carried out in strict accordance with relevant construction specifications and acceptance specifications. If problems are found, contact the design institute in time. (2) Roots, turf or humus on the surface of the filled subgrade shall be removed, and the earthwork shall be rolled in layers with a thickness of about 30cm. Each layer should have a density test report, and the next working procedure can be started only after it meets the design requirements. (3) The compaction degree of soil foundation adopts heavy compaction. After the completion of subgrade earthwork, the resilience modulus test should be carried out along the line according to the specification requirements. Cement stabilized stone powder and slag layer shall be constructed according to relevant local requirements, requiring mechanical mixing, not manual mixing. (4) The concrete structure shall be constructed in strict accordance with the requirements of design drawings. Precast components of sidewalk slabs and kerbs shall be prefabricated by cement products factory, and the construction unit shall not ram them by itself. (5) During the construction period, settlement observation shall be carried out according to the design requirements, and observation records shall be made. During embankment construction, in order to ensure subgrade width and slope compactness, each side should be over-filled with 30cm width and compacted together with the embankment. After the subgrade is completed, the slope should be brushed according to the design standard. After the earthwork of subgrade is basically completed, the elevation of the center line of subgrade bed surface, the width of subgrade and the slope gradient should be measured, and subgrade shaping should be carried out after the measurement is qualified. 2 key points of subgrade filling construction 2. 1 preparation for construction subgrade filling requires construction personnel, construction equipment and mechanical tools. Therefore, these preparations should be made before construction, and some equipment needed for construction should be prepared. At the same time, it is necessary to determine the construction center at the construction location, release the corner position of subgrade, reserve the position of side ditch, and design the depth of side ditch excavation and earthwork filling. Do the experiment well in advance, select the construction section of 200m as the construction section, and then carry out the experiment. The compaction method, compaction times and construction speed of subgrade are determined through experiments. After the experiment, it is necessary to investigate the site construction situation and understand the construction geological conditions. Then, the subgrade is lofting to determine the positions of side ditches and boundary markers in the subgrade. If it is an ordinary road surface, it is necessary to clean up the weeds on the road surface and make good drainage facilities. If the road surface under construction has a slope, it is necessary to rebuild a step with a width of 1m on the road surface, and then compact the road surface until it meets the construction requirements. 2.2 Selection and construction of fillers Before the earthwork filling and reconstruction, some soil samples should be taken from the subgrade for testing, so that the water content in the soil can be known and the composition of the soil can also be understood. When the soil meets the construction requirements, the subgrade will be filled. The filler is relatively heavy, so the loader is used to transport the filler from other places to the road section to be filled. And when unloading the filler, someone must be in charge. The unloading volume should not be too large, and it is best to unload one layer at a time. Paving after unloading. 2.3 The foundation treatment can only be filled after weeds are removed, and weeds and trees need to be removed manually. The construction of subgrade base should be carried out in accordance with the specifications. At the same time, it is necessary to do a good job of loosening the soil at this position. After the construction site is cleaned, horizontal and vertical steps should be dug in the site, and the steps should be tamped with a small rammer. Ensure that the compactness of the base position exceeds that of the subgrade. 2.4 When filling by layers, the main filling method is layered filling, and the compactness of subgrade edge should be consistent with the set compactness. The thickness of horizontal fill should be 30cm to facilitate machine operation. 2.5 Rolling work is very complicated. Vibrating roller is mainly used for rolling, and all the work should be carried out in sequence during compaction. First, we should start from the edge of subgrade, and then concentrate in the middle. At the beginning of compaction, it should be done slowly, and then the compaction speed should be accelerated. Ensure that the compaction work has no edges and corners, and achieve uniform compaction. Check the flatness after compaction. The initial pressure is static pressure, after which Zhendong compaction begins. 2.6 Detection: After the rolling is completed, measure with an instrument to ensure that the instrument has certain accuracy. When measuring, the compacted pavement should be smooth and ensure the compaction effect. After testing, it is proved that the compaction effect is qualified, and the next step of construction can be carried out. If the test results show that the degree of compaction can not meet the construction standards, it will be re-rolled. The moisture content of subgrade should not be too much, only 2% can float up and down. After exceeding this specified value, the moisture in the subgrade will evaporate. 3. Construction method of road fill subgrade engineering 3. 1 For high fill embankment, except layered filling and layered compaction, subgrade settlement period should be reserved before pavement engineering construction, and reserved settlement should be set to widen and heighten during construction. The method of widening and heightening the reserved settlement is as follows: (1) In addition to widening as designed, the settlement can be reserved at 0 ~ 1.5% of the average embankment height. (2) During the construction period, select representative sections for settlement observation. Observation points are buried in 1P3, 2P3 and bed surface respectively. When the settlement curve of observation point shows that the settlement tends to be stable, the reserved settlement height can be appropriately reduced or increased according to the height of subgrade bed. (3) Determine the slope ratio according to the design drawings, and reserve the platform width and position according to the design drawings. 3.2 The embankment at the junction of filling and excavation is the most prone to settlement at the junction. Therefore, in the process of subgrade construction, every joint should be properly handled, excavated as required, and treated according to the specifications. When pressing, it should be compacted evenly. Similarly, filling can only be carried out after the relevant supervisors check the quality. If the distance between subgrade and pavement during filling is only 1.5m, it is necessary to ensure that the design requirements can be met when the position is changed. At the same time, there must be someone who is responsible for quality management. Every time you fill it out, you should have information such as influence and words, and then save it together for others to consult. When you have any questions, you should find the person in charge. 4 Fill subgrade construction quality control (1) For the control of fill soil quality, fill areas should be filled with fillers that have passed the test inspection, and fillers that do not meet the requirements are strictly prohibited from entering the site; (2) Combined with the permanent drainage of subgrade, the drainage work in the construction process is the best. The horizontal slope of 2% ~ 4% should be set on the filling level to facilitate drainage, and temporary drainage ditches should be set at intervals of about 15m on the slopes on both sides of the subgrade to timely eliminate road water and ensure smooth drainage of the slopes; (3) The quality of layered embankment filling is the key point of the whole subgrade quality control, so the loose paving thickness of each layer of subgrade filling must be inspected before compaction. When compacting subgrade filler with roller, we should follow the principles of light before heavy, two sides before middle, static pressure before vibration, and rolling from low to high.
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