1. Construction of bio-enzyme soil solidified layer

　　(1) Determination of operation scope and quality preparation

The contents include: delimiting the construction red line range, setting up traffic blocking safety signs, and clearing the factors affecting the construction in the operation surface. Check the quality of the subgrade at the severely damaged area, and treat the subgrade that does not meet the requirements according to the specifications. Nail the middle pile and the side pile at the distance not greater than the requirements of the subgrade construction specification, lay the side line, and set the standard pile within every 0.3~0.5m outside the edge of the shoulder on both sides.

　　(2) Construction of bio-enzyme soil solidified layer

　　1) Material paving

① On the subgrade that has passed the test, set the pile stay to control the paving thickness of the subbase.

② According to the design thickness, the weathered gravel soil is laid in layers (the maximum particle size is not more than 20% of the thickness of the single layer), and the admixture such as gravel aggregate is added. The paving principle is that the thick layer is on the bottom and the thin layer is on the top.

③ After the weathered gravel is paved, mix it with a road mixer to reach the depth of the top surface of the subgrade bed. The weathered gravel soil is preliminarily mixed, and then adjusted by a grader to enter the next construction process.

④ Leveling and light pressing: use a grader to reshape the vehicle. During the reshaping process, no vehicle is allowed to pass, and the segregation of coarse and fine materials should be removed by manual cooperation. The filling width of each side exceeds the design width by 30cm to ensure that the edge of the embankment after trimming the slope has sufficient compaction degree. After the filling is leveled and qualified, use a 22t two-wheel roller to roll for 1~2 times to make the surface level off. The purpose of this procedure is to facilitate the uniform spreading and mixing of other admixtures.

⑤ According to the calculated amount of cement, the box method is used to control the uniformity of curing agent and cement paving. Manually cooperate with the loader to spread the cement evenly, and the surface shall be free of white spots, and the curing agent shall not exceed the midpoint of the set.

　　2) Mixing

① Dry mixing: road mixer shall be used for mixing. The mixing machine shall move at a uniform speed and smoothly. During mixing, attention shall be paid to the overlapping width of each lane not less than 30cm to ensure that there is no leakage in the working area. The mixing depth shall reach the bottom of the improved soil layer. The mixing shall be sufficient. It is strictly prohibited to leave a "plain soil" interlayer at the mixing bottom. After mixing, if necessary, the construction top shall be leveled again.

② Preparation of biological enzyme solution: Before wet mixing, prepare biological enzyme solution with appropriate concentration according to the design requirements, and the concentration of biological enzyme solution shall be determined according to the moisture content of the on-site materials.

③ Spraying bio-enzyme solution: Spraying the bio-enzyme solution evenly by spraying vehicle. The main point of spraying is to spray more than three times before the mixer. For each spraying, the road mixer will follow to turn over the materials and carry out the combined operation of spraying and mixing.

④ Wet mixing: every time the bio-enzyme solution is sprayed, the road mixer will follow the mixing; the bio-enzyme solution will be sprayed again, and the road mixer will mix again; until the bio-enzyme solution is sprayed.

⑤ Finally, the road mixer shall be fully mixed until the soil color is uniform.

　　3) Leveling

① Initial leveling: after the completion of mixing, the grader shall be leveled, and the road shoulder shall be included in leveling. The width of the shoulder must be guaranteed, which is the key point to ensure that the edge of the bio-enzyme solidified soil can be compacted.

② Jingping: the road roller shall first be statically grinded from low to high, and the grader shall be operated in combination to carry out Jingping. After leveling, re-check and deal with local poor moisture content, material segregation, bulge, depression and other issues.

　　4) Rolling

Moisture content is the basic premise of ensuring compaction, and controlling moisture content is the technical key point and technical difficulty of soil solidification and road construction. It must be ensured that the biological enzyme is fully diluted by water, and at the same time, the moisture content of road mix must be well controlled, and this index must be well controlled during construction.

① Compacting and rolling

The bump roller shall be subjected to static pressure, vibration and strong vibration until the compaction degree of rolling completely meets the requirements. Timely treatment of local material segregation, bulge, depression and other local problems in rolling, including the shoulder part.

② Surface rolling and light collection

It is operated by the combination of grader and roller, leveling and static grinding. The upper base course shall be leveled by 2 ~ 3% cross slope, and then the roller shall be subjected to static pressure, vibration and strong vibration until the compaction degree completely meets the requirements.

When rolling, the roller overlaps l/2 wheel width, first slow and then fast, the vibration frequency is first weak and then strong, rolling from both sides to the middle, the rolling sequence should be "static pressure 1 strong vibration 3~5 times static pressure 1 time" (the specific rolling times shall be subject to the compaction degree detected on site in the test section), and the maximum rolling speed of the roller shall be ≤ 4 km/h, it is strictly forbidden for the road roller to turn around or brake suddenly on the road section being rolled, so as not to damage the surface of the solidified soil layer. Usually, in the process of waiting for the compaction of the newly paved section, the road roller has been pressed for many times and repeatedly.

5) Treatment of joints

The joint of two working sections constructed on the same day shall be overlapped and mixed; after the first section is mixed, leave 5~8m without rolling, and roll together with the latter section.

Every day the last paragraph of work seam processing. At the end of the compacted bio-enzyme soil solidified layer, dig a groove with a width of about 30cm across the full width of the paving layer to the top surface of the lower bearing layer. The groove shall be perpendicular to the center line of the line, and the side of the soil solidified layer by the biological enzyme shall be made into a vertical surface, and two square timbers with the same thickness as the compaction thickness and a width of half the width of the excavated groove shall be placed close to its vertical surface, and the rest of the groove shall be backfilled with excavated soil; the next day, the square timbers shall be removed and backfilled with the mixture. There shall be no longitudinal joints during the construction of solidified soil.

　　2. Construction of multiple modified roller compacted cement concrete surface layer

　　(1) Base course surface treatment before surface course construction

On the basis that the base meets the design requirements, the surface layer shall be prepared before construction, and the surface of the base layer shall be carefully cleaned, washed and dried. The surface shall be free of any loose impurities and other foreign matters.

　　(2) Spraying through-sealing slurry

According to the design ratio of the modulation of enzyme glue cement modified adhesive sealing liquid, according to the design dosage to the grass-roots surface evenly spray slurry. At the same time, the paving operation of the first enzyme glue fiber modified roller compacted cement concrete mixture is carried out.

　　(3) Construction of main structure layer

　　1) Initial modification and mixing

The quantity of the mixture in each kettle shall be calculated and determined according to the construction mix ratio and the capacity of the mixer, and shall meet the following requirements:

① Strictly control the water content of the mixture. The natural water content of sand and crushed stone shall be detected before each commencement, and the construction mix proportion of water addition shall be adjusted and calibrated on site according to the weather change. Accurately adjust the water metering.

② The feeding equipment and metering tools shall be checked by a special person, and the intake proportion of water, cement, sand, crushed stone, flexible fiber and polymer modified mortar in each kettle shall be consistent.

③ The feeding of aggregate, cement and water shall be consistent with the mixing of ordinary cement concrete. When the paving layer of the surface course is different, the gradation of the aggregate needs to be adjusted properly.

④ Feeding sequence during mixing: Aggregate, cement and fiber are added to the mixing kettle in the hopper for dry mixing for about 30 to 40 seconds, and then fully dissolved rubber powder solution and water that can make the mixture reach the best moisture content are added, and the mixture is mixed until it is fully and evenly out of the warehouse. Inject materials from the hopper to the mixing kettle until the mixing is completed and the time is about 3 minutes.

　　2) Transportation

During transportation, slurry running and segregation of mixed materials caused by repeated bumping of vehicles shall be avoided as much as possible. The initial setting time of cement shall be controlled from discharging to completion of construction. Under high temperature weather, the transportation vehicles shall be covered with tarpaulin to prevent water evaporation. The height of discharging and unloading shall not exceed 1.5m. In case of segregation, the vehicles shall be remixed and evenly before paving.

　　3) Paving

Paver shall be used for paving operation, and the elevation shall be controlled by loose paving coefficient. The production capacity of mixing and paving machinery shall be matched. Paver must be slow, uniform, continuous uninterrupted paving, not arbitrarily change speed, in order to improve the flatness, reduce the segregation of the mixture. The paving speed should be controlled at 2~4 m/min, and manual assistance can make the paving reach full corners.

　　4) Rolling

① The length of the rolling section shall be determined timely according to the climatic conditions, and the paving length of 100~150m is generally taken as the rolling length. If the climate is dry, the rolling length can be appropriately shortened, otherwise the rolling length should be appropriately extended.

② Use manual plate tamper for the corner position, accompanied by compaction operation. However, it is also necessary to achieve the requirements of compactness and smooth and beautiful surface of vibrating slurry.

③ The rolling sequence is generally static pressure twice → low frequency vibration rolling twice → high frequency vibration rolling twice (to achieve vibration slurry lifting) → static pressure twice to make the surface smooth and beautiful. The compactness after final pressing shall reach more than 97%. If the pulp lifting condition is poor and the pulp replenishment operation is required, the workload and cost will increase.

④ The overlapping width of wheel track during roller operation shall be greater than 30cm; the rolling speed shall be controlled at 2~6 m/min.

⑤ The joint between each two rolling sections shall be turned back to the elevation by wood square, so as to be natural, smooth and beautiful without obvious joint phenomenon.

⑥ If cross-grain cracking occurs during rolling due to the influence of moisture content or excessive drying caused by weather, the modified liquid shall be sprayed manually and tamped with manual plate compactor.

　　(4) Secondary modification construction

The second modification construction shall be carried out immediately after the rolling of the main structural layer is completed after each paving. After paving and compaction, the secondary modified through-viscous slurry shall be sprayed in time according to the design ratio. The spraying shall be uniform and saturated, and the slurry flow on the surface shall prevail.

The upper layer is sprayed with modified through-sealing slurry according to the design formula and dosage, and the uneven parts are manually roller sprayed.

　　(5) Health maintenance and cutting

After the secondary modification construction of the upper layer, the film is covered and cured, and the film is uncovered for 3 days for the next process construction. The surface of the main structural layer is carefully checked, and the phenomena of poor slurry lifting and material segregation shall be fully disposed. An expansion joint is cut every 10m to a depth of 1/3 of the total thickness. One expansion joint shall be set every 200m, and the filling and sealing material shall be filled with high-density foam board and enzyme glue modified slurry, which shall be tightly bonded with the modified roller compacted concrete joint wall without water seepage and obvious gap.

　　(6) Three times modified construction

Every time one layer is added, the modified through-adhesive slurry shall be sprayed. The third time of spraying the modified through-sealing slurry shall be carried out after the secondary modified spraying of the upper layer is completed for 3 days. The slurry shall be evenly sprayed according to the design formula and dosage, and the uneven parts shall be evenly coated by manual roller. Special attention should be paid to the filling of extension and contraction joints, so that they are full and smooth, and there is no obvious trace on the road surface.