1. Prepare the next bearing layer:
The lower bearing layer must meet the corresponding quality indicators. The surface of the lower bearing layer should be smooth, and the elevation, cross slope and compaction degree should meet the requirements of the design specification. The surface must be thoroughly cleaned and sprayed with proper amount of water to keep the lower bearing layer wet. At the same time, mark two sideline lines with lime.
2. Construction lofting:
After the preparation of the lower bearing layer is completed and all the quality indexes meet the design requirements, the construction lofting will be carried out, and the center line of the subgrade and the left and right side piles will be restored. One pile will be set every 20 meters, and indicator piles will be placed outside the shoulders on both sides. Mark the design elevation of lime-soil edge with obvious marks on the indicating pile.
3. Soil preparation and dusting:
(1) Soil preparation: Calculate the amount of soil to be dried according to the width, thickness and maximum dry density of lime soil layer; Then, according to the water content of soil and the tonnage of trucks used, the stacking distance of each truck and the amount of lime required per square meter of lime soil are calculated, and the vertical and horizontal spacing of lime placement is determined. Spreading soil evenly according to loose thickness is beneficial to mechanized construction. After spreading the soil, it shall be roughly leveled by bulldozer first, and then leveled by grader, and the redundant part shall be removed to ensure uniform thickness and smooth surface.
(2) Paving for preparing ash: Before preparing ash, lightly press the paved loose soil 1-2 times with a roller to ensure that there is no big rut when preparing ash, and it is forbidden for heavy trucks to turn around in the operation section. Before making ash, the lime dosage per square meter should be calculated according to the ash dosage, the loose dry bulk density of lime under different water contents and the maximum dry bulk density of lime soil. Before preparing the ash, draw two gray lines at the position of the ash bar in advance to ensure that the ash bar is straight. Before laying lime, mark the edge of lime soil with a grid, and then spread lime evenly within the marked range manually.
4. Sprinkler drilling:
If the water content of the leveled soil is too small, water should be sprayed on the soil layer to stop the material. Sprinkle water evenly to prevent excessive local humidity. Sprinklers are strictly prohibited from stopping and turning around in the sprinkling section.
5. Leveling and gently pressing:
After the artificially paved soil layer is leveled, it will be rolled 1-2 times with a 6-8T double roller to make its surface smooth.
6. Unloading and lime sprinkling:
(1) According to the calculated vertical and horizontal spacing of lime for each vehicle, mark the soil layer with lime, and draw the edge line for laying lime at the same time.
(2) Sprinkle lime evenly. There should be no blank position on the surface after lime sprinkling. 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.
7. Mixing and watering:
Adopt special stabilized soil mixer for road mixing construction, assign special personnel to track the mixer, check the mixing depth at any time, and cooperate with the mixer operator to adjust the mixing depth. The mixing depth should reach the bottom of the stable layer, and it should invade the lower bearing layer by 5- 10mm to facilitate the bonding of the upper and lower layers. It is forbidden to leave a plain soil interlayer at the bottom of the mixed layer.
(1) The soil water content is small. First of all, we should turn over the soil with a plow to make the lime in the middle and lower layers, then sprinkle water to supplement the water, and continue to turn over the soil with a plow to make the water evenly distributed. Considering the loss of water in the process of mixing and leveling, the water content should be larger (depending on the climate and the length of mixing and leveling time), and the soil water content is too large, so it needs to be mixed and cooled with a plow.
(2) After the water content is appropriate, roughly level it with a grader, and then mix it with a lime-soil mixer for the first time. When mixing, assign special personnel to dig randomly, dig one place every 5- 10 meter to check whether the mixing is complete. For the paragraphs that are not mixed to the end, remind the mixer driver to return to remix in time.
(3) If the plasticity index of the soil is high and the clods are not easily crushed, the mixing times should be increased, and it should be noted that before the next mixing, the mixed lime soil should be roughly leveled and compacted, and then mixed, so as to achieve uniform mixing and meet the requirements of the specification.
8. deployment:
Use grader, combined with a small amount of manual leveling.
(1) After lime-soil mixing meets the requirements, it shall be roughly leveled with a grader to eliminate ridges, waves and grooves. Produced by mixing, making the surface roughly flat.
(2) Stabilize the voltage 1-2 times with vibratory roller or tire roller.
(3) Use level or hanging line to lay control piles, mark them with lime powder, and determine the distribution density of sample points according to the level of grader drivers.
(4) The grader should be leveled from outside to inside.
(5) Repeat steps (3)-(4) until the elevation and flatness meet the requirements.
9. rotate
(1) According to the road width, wheel width and wheel pitch of the road roller, the rolling scheme shall be made, and the rolling times of each part shall be the same as far as possible, and the two sides shall be pressed 2-3 times more.
(2) After the leveling is completed, first use vibratory roller to roll from both sides of the road to the center of the road. When rolling, the rear wheel should overlap 1/2 wheel width, generally rolling for 6-8 times. The rolling speed of the roller should be 1.5- 1.7 km/h for the first two times, and then 2.0-2.5 km/h until there is no obvious wheel track. In a word, the roller should follow the principle of "from the edge to the middle, first light and then heavy"
(3) It is forbidden for the roller to turn around or suddenly brake on the completed or rolling road section, and the surface of the stable soil layer shall be guaranteed not to be damaged.
(4) In the rolling process. The surface of calcareous soil should always be wet. If the water evaporates too fast, a small amount of water should be added in time, but it is forbidden to sprinkle water to crush it.
(5) In the rolling process. In case of "bouncing, loosening and peeling", it should be opened in time for re-mixing (adding appropriate amount of water) or treated by other methods to meet the quality requirements.
(6) Before the end of rolling, the grader shall be used for final leveling again, so as to make it longitudinal and comfortable, and the road arch and superelevation shall meet the design requirements. The final leveling should be carried out carefully, and the local higher parts must be scraped off and swept clean.
Key points: Rolling must be completed continuously without stopping halfway. There should be enough rollers to reduce the rolling forming time. Vibrating roller and three-wheel roller should be reasonably equipped. During the rolling process, you should go straight and drive at a low speed, and roll horizontally within the range of bridgehead 10 meter.
10. Check:
(1) Operators should pay close attention to the construction site. After the rolling passes are completed, immediately sample and check the compaction degree (take out the test results in time). If the compaction is insufficient, immediately replenish the pressure until the compaction requirements are met.
(2) Check the flatness, elevation, cross slope, width and thickness within two days after molding, and take measures to deal with nonconforming products.
(3) Key points: those with appearance defects such as boiling, obvious wheel tracks, loose surface, serious peeling, and excessive mud blocks are not allowed to be accepted, and should be thoroughly handled; If the elevation is not suitable, the higher part shall be scraped off by grader, and the lower part shall not be repaired, and the elevation shall be controlled by left, middle and right three lines; Compaction and strength must meet the requirements, or rework.
1 1. Treatment of joint and eversion:
(1) The joints of two working sections constructed on the same day shall be in the form of lap joint. After mixing and molding in the previous section, leave it for 5-8m without rolling. When the latter section is constructed, it will be mixed with the uncompacted part left in the previous section.
(2) Mixing machinery and other machinery are not allowed to turn around on the broken ash soil layer. If it is necessary to turn around, measures should be taken to protect the turning part so that the surface of lime soil will not be destroyed.
12. Health:
If the lime soil of the upper structure layer cannot be covered in time, the curing period should be no less than 7 days. Sprinkling curing method is adopted, and the surface of lime soil is often kept moist during curing. Traffic should be closed during the maintenance period, and all vehicles except sprinklers are prohibited. Clear signs must be set.
Technical requirements for construction of lime industrial waste residue stabilized soil
1. Construction shall be organized in late spring and summer. During the construction period, the daily minimum temperature shall be above 5℃, and it shall be completed 1- 1.5 months before the first heavy freezing (-3℃ ~-5℃).
2. The ingredients should be accurate. Expressed by the mass ratio of lime: fly ash: aggregate.
3. Urban roads are mixed by centralized plants and transported to the site for paving.
4. During the construction of lime-fly ash macadam base, leveling with thin-layer repair method is prohibited, and it should be removed appropriately.
5. It must be kept moist for health, so as not to dry the surface of lime-fly ash gravel layer. Traffic should be closed before pu seal or surface layer, and protective measures should be taken when traffic is temporarily opened.
It can be summarized as firm, stable, uniform, clean and dry.