(1) Material preparation.
Polymerization, stew. When preparing soil materials, materials should be collected from top to bottom within the cutting depth, and it is not advisable to collect them in layers, and unqualified materials should not be collected together. In the site with smooth cutting, the earth materials are stacked in layers with bulldozers, loaders and excavators, and the square of the earth material pile is calculated. Add 2% quicklime, turn it over several times with two excavators, stir it evenly, and stew it for 2 ~ 3 days. Load the dump truck and transport the soil to the construction site. Oversize particles in the material should be screened out.
(2) Material consumption.
When the water content of aggregate is large, lime can be added twice. First, add 2% quicklime to the soil yard, stew for 2 ~ 3 days, and you can go on your way. According to the water content of excavated aggregate and the tonnage of trucks, the stacking distance of each truck is calculated. After evenly spreading soil on the subgrade, add 2% ~ 3% hydrated lime. According to the loose paving thickness, roadbed paving width and compaction degree adopted in the test section, the amount of lime needed in this section is calculated. According to the thickness of lime soil layer, predetermined dry bulk density and lime dosage of 2% ~ 3%, the required lime weight per square meter of lime soil is calculated, and the paving area of lime per vehicle is calculated. If bagged lime powder is used, calculate the spreading area of each bag of lime. Calculate the unloading position of each truck of lime, that is, the vertical and horizontal spacing, or calculate the vertical and horizontal spacing of each bag of lime.
(3) Transportation, paving and mixing.
1) transportation and distribution of earth materials.
The loose laying thickness should be thin but not thick, generally 20 ~ 25 cm, and the compaction thickness is 15 ~ 20~25cm. Using thin-layer rapid filling technology can improve the first pass rate, without rework, and the progress is fast, which is a successful experience in lime-soil subgrade construction.
Attention should be paid when transporting materials: sprinkle water on the lower bearing layer the day before stacking and paving to make it wet, but it should not be too wet to cause mud; When using dump trucks to transport earth materials, the capacity of each vehicle should be basically equal; Use lime to lay a grid for filling each car, and unload the soil in the grid.
2) Earthwork shall be smooth.
After the completion of soil loading, it should be paved in time, and the stacking time of soil materials on subgrade should not be too long. Set elevation control points at both sides and center of each section respectively. The loose laying thickness can be controlled at 25cm. First, use bulldozers for rough leveling. If it is excessive or insufficient, use manpower to cooperate with grader for leveling. Hang lines at the edge of subgrade to control the thickness of pavement, and then hang lines at each section to check the thickness of pavement. Check it several times until it is qualified. The surface shall be as flat as possible, and the road arch shall be set as required. In the process of paving, attention should be paid to removing clods, oversized particles and other sundries. If there are more clods in the aggregate, they should also be crushed; Check whether the thickness of loose paving material layer meets the expected requirements (loose paving thickness = compacted thickness × loose paving coefficient). When necessary, materials should be reduced or supplemented.
3) Laying and curing lime.
When spreading lime, if the soil is too dry, water should be sprayed in advance to make the soil water content slightly less than the optimal value. The excavation section is fine-grained soil, which will be stuffy for one night; Medium-grained soil and coarse-grained soil can be drilled 1 ~ 2h depending on the content of fine soil. On the artificially paved aggregate layer, according to the calculated vertical and horizontal spacing of lime for each car, mark the unloading position of lime on the aggregate layer with lime, and draw the edge line of paving lime at the same time, and manually pave the discharged lime evenly. After the completion of lime paving, there should be no blank position on the surface. Measure the loose laying thickness of lime, and check whether the lime dosage is appropriate according to the water content and loose laying density of lime.
4) Stir and add water.
① Mixing with rotary tiller, agricultural plough, pavement mixer and grader can ensure reasonable collocation and is economical and applicable. After ploughing with an agricultural plough for one time, line it up with a rotary tiller for 2-3 times according to the width of the working surface, then plough it to the end, continue to grind it with a rotary tiller for 2-3 times, and finally mix it with a BMW road mixer for 1-2 times, which can generally achieve uniform ash content and ensure that the bottom layer of "plain soil" is turned up, and there is no plain soil interlayer and clods larger than 5cm. It is forbidden to leave a layer of "plain soil" between the soil layer and the lower bearing layer, and it is also necessary to prevent it from being too deep and damaging the surface of the lower bearing layer too much.
(2) In the process of mixing, check the water content in time. Sprinkle water with a sprinkler to make the water content of the mixture equal to or slightly greater than the optimal value (depending on the soil type, it can be about 1%), and the sprinkling distance is longer. The sprinkler and the corner at the other end of the waterwheel should exceed the mixing section by more than 2m. Sprinklers should not turn around and stay on the road surface that is being mixed and planned to be mixed that day to prevent local water accumulation from being too large. Mixing machinery should follow the sprinkler for mixing, especially in the sections with large longitudinal slopes, so as to reduce water loss.
(3) In the process of sprinkling water, oversize particles are picked out by manual cooperation, and the "nest" of coarse and fine stones and excessively wet parts are removed. The marks of mixing completion are: the color of the mixture is consistent, there are no ash strips, ash blocks and flower faces, there is no "nest" of coarse and fine stones, and the moisture is appropriate and uniform.
5) Plastic surgery.
Grader shaping. After the mixture is stirred evenly, it will be leveled and reshaped by grader. In a straight section, the grader should level the center of the road from both sides. In the flat curve section, the grader should be leveled from the inside out. Go back and shave again if necessary. Use vibratory roller to quickly static press 1 ~ 2 times. Before leveling with a grader, the surface of low-lying areas should be leveled with a toothed rake of more than 5 cm to avoid thin-layer repair on a smoother surface. After shaping with a grader, roll it again. For local low-lying areas, loosen the soil 5cm below the surface with a rake, repair and level it with the newly mixed lime mixture, and then reshape it again with a grader. Every plastic surgery should be carried out according to the specified slope and road arch. Pay special attention to the smoothness of joints, which must be smooth.
6) Rolling.
After molding, when the mixture is at the optimum water content 1% (if the surface water content is insufficient, water should be sprayed appropriately), the mixture will be rolled by YZ 18C vibratory roller within the full width of subgrade immediately. Straight line segment, rolling from shoulders on both sides to road center. A horizontal curve segment extending from the inside shoulder to the outside shoulder. The edge of the vibrating roller's rolling route must overlap half a wheel, and it shall be carried out when the road surface is full width. The second light vibration, the driving speed is controlled at 2 km/h; For the third time, the vibratory roller is used for strong vibration, and the driving speed is controlled at 3 km/h; After polishing, measure points as required, and measure the compactness and water content of each point respectively; After the fourth rolling, repeat the above test; For the fifth and sixth time, the vibrating drum is used for strong vibration, and the above detection test is repeated; If there is unevenness, level it with a grader to ensure uniformity and compactness. After the roller is pressed for the third time, after each rolling, the construction technicians, operators and other relevant personnel shall conduct self-inspection.
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