2. 1 Prepare the lower bearing layer
(1) The surface of the lower bearing layer of lime-fly ash stabilized soil is smooth and solid, without potholes, and the elevation and road arch meet the design and specification requirements.
(2) The subgrade shall be subjected to vibration compaction test. During the rolling process, if it is found that the soil is too dry and the surface layer is loose, sprinkle water properly before loading the soil; Excavate the existing pit or partial pit 10cm, then replace it with lime soil and tamp it.
(3) Roadbed slopes on both sides of the construction section shall be trimmed and drained.
2.2 Construction lofting
(1) Restore the center line on the soil foundation, set out the middle pile spacing 10m, set up indicator piles 0.5m outside the shoulder edge on both sides, and set out the lime-fly ash soil sideline.
(2) Mark the design height of the top edge of lime-fly ash stabilized soil with red reflective paper on the indicator piles on both sides.
2.3 Material preparation and soil spreading
2.3. 1 material preparation:
(1) Fly ash is transported to the subgrade near the construction section three days in advance. Fly ash delivered to the site should contain enough moisture to prevent dust. When it is dry and windy, the surface of the material pile should be watered to keep it moist. Cover the fly ash stacked in batches with plastic paper to avoid excessive humidity in the rain; After the lime soil layer is paved, it will be directly transported to the construction site; Lime fly ash soil is transported from the soil yard to the construction site. When digging in the soil yard, trees, turf, silt and other miscellaneous soil should be removed first, and excessive particles in the soil should be screened out.
(2) Calculation of lime-fly ash soil aggregate quantity:
Lime-fly ash aggregate per square meter:
Earthwork quantity = length × width × thickness × maximum dry density × percentage of soil aggregates × compactness/soil density × compactness.
Lime quantity = length × width × thickness × maximum dry density × percentage of lime aggregate × compactness/lime density.
Fly ash content = length × width × thickness × maximum dry density × percentage of fly ash aggregate × compactness/loose dry density of fly ash.
(3) Sprinkle water on the subgrade before loading to make its surface wet, but not too wet to cause mud.
When loading soil, control the material quantity of each vehicle to be basically equal, and prepare materials according to the calculated earthwork quantity and unloading distance to avoid insufficient or excessive materials in some sections.
(4) In order to facilitate the maintenance of lime-fly ash stabilized soil subgrade, lime-fly ash stabilized soil shall be paved immediately after the completion of subgrade acceptance, and the paving soil shall include the shoulder width, with a total paving width of 30. 18m.
Laying soil
(1) Determine the positions of the three sections before paving, measure the top elevation of the lower bearing layer, the elevation after paving and the elevation after rolling, and check the thickness of loose soil layer, which meets the expected requirements. Calculate the paving area of each vehicle, and then make a gray line grid with white ash on the subgrade that has been inspected, and arrange the soil neatly into the grid. When the bulldozer loosens the soil, measure the elevation control points with a level, and level the soil according to the height of the control points. After the bulldozer is roughly leveled, measure the elevation, level it to the specified elevation and road arch with a grader, and test the compactness and water content. The paved soil surface should be smooth and without potholes, and the elevation of road arch should meet the specified requirements.
(2) The soil laying operation shall be completed the day before lime and fly ash are laid. Control the paving length according to the daily schedule, and complete the mixing, mixing and rolling of fly ash and lime the next day.
(3) In the process of paving materials, clods, oversized particles and other sundries should be removed.
(4) If there are many clods in the soil, the mixer will crush them.
2.4 Watering and drilling materials
According to the detected water content, if the leveled soil water content is too small, spray water on the soil layer [supplementary water content v = ρ * (w0-w)/(kloc-0/-w) in advance 12 hours, where ρ is the density of the soil before rolling (kg/m3); W-natural water content of soil; W0- optimum water content of soil]. Sprinkle water evenly to prevent excessive local moisture. Sprinklers are strictly forbidden to stop and turn around on the sprinkler section.
2.5 Set the center line, edge line and grid line.
Before laying fly ash and lime, set out the center line, side line and frame line with white ash according to the indicated pile.
2.6 Laying lime and fly ash
(1) Sprinkle lime and fly ash: sprinkle fly ash first, mix stably, then sprinkle lime, and the lime dosage will increase 1%.
(2) According to the calculated loose square dosage of fly ash per linear meter, make a trapezoidal square yard with 3cm×3cm angle steel, and level the fly ash at the half center line of lime-fly ash soil. Fly ash is transported to the construction section by car, and the fly ash is coded into trapezoidal ash area according to the ash consumption per linear meter, and coded into two ash areas according to the actual construction needs, and the ash strips are straight. After the acceptance of the supervisor, the fly ash shall be spread evenly by hand according to the required width. If the water content of the fly ash is small, water shall be sprayed appropriately.
(3) After the mixed fly ash is leveled and rolled, the frame line is paved, and the bagged lime is transported to the construction site with a small truck. According to the lime dosage required in the frame area, the dosage per square meter is calculated and put into the frame. After the quantity acceptance of the supervision engineer is completed, it will be spread evenly in the grid manually.
2.7 Mixing and watering
(1) The stabilized soil mixer is used for mixing, and the mixing is carried out twice. After the fly ash is paved, the lime-soil mixer performs the first mixing. After the first mixing, the tractor is leveled and stabilized, lime is laid, and the second mixing is carried out after the laying is completed. Before mixing, the water content of lime-fly ash should be detected. If the water content loss is too large, a proper amount of water should be sprayed, and the mixer should follow the sprinkler to stir. The mixing depth reaches the bottom of the stable layer, and invades the lower bearing layer by about 5-65438 00 mm ... Designate a special person to follow the mixer, check the mixing depth at any time, and coordinate with the mixer operator to adjust the mixing depth to avoid plain soil interlayer. When the water content is too high and the stabilized soil mixer slips, first mix the pears with rotary tillage. According to the uniformity and water content of aggregate mixing, the mixing times are determined.
(2) After mixing, test the water content of the mixture, which should be greater than the optimal water content of 65438 0%. If the water content is low, spray water evenly on the mixed mixture with a nozzle sprinkler, and the sprinkling distance should be longer, and the watering place and corner at the other end of the sprinkler should exceed the mixing section by more than 2m. Sprinklers are not allowed to turn around and stay on the road section where mixing is going on and planned on that day, and local water volume should be prevented from being too large.
(3) In the process of mixing, the mixing depth should be checked in time when mixing lap 10cm, and every 5 meters. The marks of the completion of mixing are: the color of the mixture is consistent, there are no ash strips, ash blocks and flower surfaces, there are no "nests" or "bands" of coarse and fine particles, and the moisture is appropriate and uniform. In case of uneven mixing and interlayer, notify the mixer to return to stir again.
(4) After mixing is completed, manually level the local uneven parts, and the tractor should stabilize the voltage, and pay attention to overlapping when stabilizing the voltage to prevent pressure leakage.
2.8 plastic surgery
(1) After releasing the center line, survey the elevation control points according to the loose paving coefficient, and set the leveling reference point of the grader. The grader should be leveled from both sides to the center of the road, and the grader should be leveled from the inside out when the ultra-high curve section is set. If necessary, go back and shave again. It is not allowed to discard the surplus lime-fly ash soil on the slope during scraping. For the last leveling, if the surface water content is low, use a sprinkler to spray water, which is convenient for rolling forming, and at the same time, use a soil grader to level it, so as to scrape it without repairing it.
(2) For local low-lying areas, level the surface layer by more than 5cm with a tooth rake, and repair and level the newly mixed lime-fly ash graded macadam.
(3) Every plastic surgery should be carried out according to the specified slope and road arch, and special attention should be paid to the smoothness and smoothness of joints.
(4) During the plastic surgery, no vehicles are allowed to pass.
2.9 rolling
(1) Rolling combination: the combination of vibratory roller, three-wheel roller and tire roller.
(2) Rolling sequence and number of times: firstly, use a vibratory roller for static pressure 1 time, then use a vibratory roller for low vibration 1 time and high vibration twice, then use a three-wheel roller for static pressure twice, and finally use a rubber-tyred roller for rolling twice. When the road surface is rolled from the shoulders on both sides to the center of the road, the rolling process will be straight and low-speed, with the overlap of 1/2 wheel width, and the rear wheel must exceed the joint of the two sections. When the rear wheel is pressed to the full width of the road, repeat it (twice more on both sides). The rolling speed of the roller is 1.5~ 1.7km/h for the first two times, and then it is 2.0 ~ 2.5 km/h.. When rolling, the compaction degree should be detected in time, and the rolling scheme should be adjusted in time according to the growth situation. The soil shoulder shall be rolled together with the subbase. Rolling work must be completed continuously, and it is not allowed to stop halfway. .
(3) In the process of lime-fly ash soil rolling, it is forbidden for the roller to turn around and brake suddenly on the completed or rolling road section to ensure that the surface is not damaged.
(4) For the boiling in the rolling process, it should be opened in time to dry and rolled to the specified degree of compaction. Due to the high temperature, in order to prevent peeling, the rolling time should be controlled before 10 am or after 4 pm. If it is found that the peeling is serious, use a rotary tiller to mix and re-roll to the specified degree of compaction.
(5) The bridge head shall be rolled within the range of10m, and the surface of the stabilized soil shall always be wet during the rolling.
(6) Treatment of joints and bridge heads: After the lime fly ash is crushed, immediately cut off the hanging lines of the parts with uneven mixing, large elevation error or poor flatness to keep the joints straight and tidy. At the joint of the next operation section, the general soil and mixture are suspended for 2m, and leveling shall be carried out according to the loose laying thickness at ordinary times.
2. 10, health preservation
Curing shall be carried out immediately after the completion of rolling, and the curing time shall be no less than 7 days. If the next structural layer is not constructed after 7 days of curing, the curing should be continued to keep the surface of lime-fly ash soil moist. Prevent lime-fly ash soil from losing strength due to lack of water. Don't be wet or dry during the health-keeping period, and close the traffic except the sprinkler during the health-keeping period. Non-woven geotextile is used for curing by spraying water.
2. 1 1 lime fly ash soil testing project