The project is located in Feixi Hotel, Shangpai Town, Feixi County. Project content: 1, retaining wall, foundation type is rubble foundation. 2, asphalt concrete pavement, stone cushion, three slag base, thickness of 30cm. 3, construction waste outbound. 4. Plant 4 trees-Cinnamomum camphora.
Second, the construction conditions:
(1) Preparation of machinery and tools:
Excavators, dumpers, trolleys, frog rammers, sledgehammers, hand hammers, crowbars, mud buckets, ropes, lifting rods, steel tape measures, steel wire pendants, chalk, steel wire pallets, scaffolding boards and shovels.
(2) Technical requirements of materials:
1, cement:
A, when entering the warehouse, should have the quality certificate;
B, should according to the variety, strength, delivery date, factory inspection and acceptance, and stacked separately, first come, first served;
C, bagged cement stacking height should not exceed 10 package;
D, should not be piled up in the open air. If stacked in the open air, there should be a damp-proof mat below and a tarpaulin above;
E, the service life should not exceed three months from the factory, and its strength should be tested first.
2. Sand:
Medium sand should be used. The quality requirement of sand should be greater than 2.5g/ m, its bulk density should be greater than 1400kg/m, and its porosity should be less than 45%. Visually, it should not contain grass roots, leaves, branches, plastics, coal blocks, slag and other sundries, and the silt content of sand should not exceed 5%.
3. Gravel:
Before rubble enters the site, check whether its strength grade (not less than Mu30) and durability meet the design requirements. According to the needs of engineering, when checking the mechanical properties of masonry, besides compressive strength, shear strength and impact toughness should also be considered. The durability of stone mainly includes frost resistance, weather resistance, fire resistance and acid resistance. Rubble used should be hard, without weathering, peeling and cracks; Before laying, impurities such as dirt and scale on the stone surface should be removed. Rubble should be massive, and the thickness of the middle part should not be less than 200 mm.
4, mortar:
Mortar should be tested before entering the site to ensure that the grade and strength of mortar must meet the design requirements. Cement and sand for mixing mortar shall meet the above technical requirements, and clean water without harmful substances shall be used as water. Mixing should be made in strict accordance with the weight of cement and sand.
Third, the construction steps and methods:
(1) process flow:
Surveying and setting out-earthwork excavation-retaining wall masonry-earthwork backfilling-drainage ditch-retaining wall jointing
(2) Operation technology:
1, positioning pay-off:
Before foundation pit excavation, level the excavation sideline with lime powder, drive horizontal piles in adjacent positions, and mark the excavation depth on the horizontal piles. During excavation, the foundation trench should be treated according to its groundwater level. If there is no obvious groundwater, the foundation trench shall be leveled and compacted according to the design requirements. If it is predicted that high groundwater will flood into the foundation pit, the excavation can be widened by 300mm along both sides of the foundation pit as the reserved construction face.
2. Excavation of foundation pit by sections and layers:
Excavation of retaining wall foundation pit is carried out by excavator from top to bottom, in layers, sections and along contour lines. Each section of the foundation pit is excavated in layers from top to bottom along the contour line, and the excavation depth of each layer is about 1m, and the excavation is carried out in layers to the required depth. Mechanically excavate to 200mm above the designed basement elevation, and then artificially deepen the leveling according to the reserved elevation difference to reach the designed basement depth, so as to prevent the basement soil layer from being disturbed.
3, retaining wall masonry:
A, retaining wall foundation and wall body are built with MU30 rubble and cement mortar.
B, before foundation masonry, should first check the size and elevation of foundation pit, remove sundry, ensure that there is no big protrusion at the bottom of the tank.
C, and then the foundation pay-off, draw the pay-off to release the foundation axis and sideline, and set up the basic skin pole, which marks the height of step and layered masonry, and the layered masonry height is 50 ~ 60 cm. Draw a straight line between the measuring rods.
D, build by laying bricks or stones the first layer of stones, the basement must first sit slurry, so that the bottom of the stones and foundation uniform contact.
Stone should be a large flat gravel, with the big face down. Choose more square stones, build by laying bricks or stones on each corner, as corner stones, the corner stones on both sides should be aligned, and the specifications of the corner stones on the four corners should be roughly equal.
E, after the corner stone is built, build by laying bricks or stones inside and outside, as a face stone, and finally build by laying bricks or stones to fill the middle part of the abdomen stone. When paving stones and filling abdomen stones, they should be staggered according to the natural shapes of the stones, so as to minimize the gaps between the stones, then fill the gaps with mortar, put appropriate pebbles according to the shapes and sizes of the gaps, and tap with a small hammer to make all the stones squeeze into the gaps.
F, build by laying bricks or stones more than two floors, each build by laying bricks or stones a stone, should be spread with mortar, mortar should be spread more and more thick, when the stone build by laying bricks or stones, just meet the requirements of the thickness, and just covered the whole mortar joint. Mortar joint thickness should be 20 ~ 30 mm, mortar should be full.
G, the top masonry foundation, appropriate chooses larger rubble masonry. The daily laying height of foundation shall be controlled within1.2m.
H, rubble masonry form should be "internal and external masonry, staggered joints, stone pulling and masonry staggered, rubble wall stone pulling should not be less than per meter of wall surface 1 block".
I, rubble wall must be set to pull stone. Pull stones should be evenly distributed and staggered, and at least one piece should be set every 0.7m2 wall as required, and the spacing within the same skin should not be more than 2m. For the wall part of 40 cm, the length of the pull stone should be equal to the wall thickness; For walls with a wall thickness of more than 40cm, two pull stones can be used for internal and external lap joint, with the lap length not less than 15cm and the length of one piece not less than 2/3 of the wall thickness.
J, before laying rubble retaining wall, you must check the axis position and hanging line on both sides of masonry, and relax10 mm; On each side; Generally, the height of masonry layer is 50 ~ 60 cm, and the daily masonry height is controlled at1.2m..
K, rubble masonry to layered masonry to the top, each layer height leveling, staggered joints between two layers of height shall not be less than 80mm, pull stones to stagger each other. Rubble masonry, there can be no contact between stones, mortar joint thickness should be 20 ~ 30 mm ... Because of the irregular shape of rubble, a part of mortar should be filled with small rubble first. Try to shake it after laying it. If it is unstable, it can be filled with small rubble, and stones may not be filled dry before grouting.
4. Backfill soil behind retaining wall:
A. The original soil (crushed stone soil) shall be used for the backfill of retaining wall, and no organic matter or other sundries shall be mixed in the fill. When filling the soil, the wall should be built while filling the soil, and the frog rammer should be used manually to tamp it in layers. The thickness of each layer is
B, before filling, the garbage and other sundries at the bottom of the foundation pit (groove) should be cleaned up; Before the fertilizer box is backfilled, it must be cleaned to the bottom elevation of the foundation, and the scattered loose garbage, mortar, stones and other sundries must be removed.
C, check whether there is any sundries on the quality of backfill soil, whether the particle size meets the requirements, and whether the water content of backfill soil is within the control range; If the water content is high, measures such as scarifying, airing or evenly mixing dry soil can be adopted; When the water content of backfill soil is low, measures such as watering and wetting can be taken in advance.
D, backfill soil should be layered paving. The paving thickness of each layer should be determined according to the soil quality, compactness requirements and mechanical properties.
E, general frog rammer each layer of soil thickness is 200 ~ 300mm；; Manual tamping is not more than 200 mm. After each layer is laid, it should be raked flat.
F, backfill soil each layer should be compacted at least three times. Tamping should be done once and a half times. Bad tamping should be connected in rows and crisscrossed. It is also forbidden to use the so-called "water rammer" method to sink the soil by pouring water.
G, the depth of the two foundation pits (slots) are connected, and the foundation should be filled first; When it is filled to the same elevation as shallow foundation pit, it will be compacted with shallow foundation. If it is necessary to tamp and fill in sections, the junction should be filled in a step shape, and the height-width ratio of the step is generally 1: 2. The staggered joint distance between upper and lower floors should not be less than1.0m.
H, finishing and drying: after the filling is completed, the surface shall be leveled with stay wires, and any place exceeding the standard elevation shall be leveled in time according to the line; Where the elevation is lower than the standard, it should be filled and compacted.
Masonry technology of retaining wall drainage ditch:
Step 5 Practice in detail
The top surface of retaining wall is 20 thick 1:2 plastered with cement mortar and calendered with virgin pulp.
6. The surface of retaining wall shall be marked with 1: 3 cement mortar. When jointing, keep the wall clean, firmly bonded, dense and tidy.
Four, quality control measures and safety technical measures
(a) quality problems and preventive measures:
1, the mortar strength is unstable: the material measurement should be accurate and the mixing time should meet the specified requirements. The production, maintenance and pressure test of test blocks shall comply with the regulations.
2. The horizontal mortar joint is uneven: the number of skin poles should be firm and the elevation should be consistent. When laying, the line should be tight, the wall should be leveled and the line should be laid.
3. Stone quality does not meet the requirements: strictly check the variety, specification and color of the stone entering the site. It's unnecessary to reject it if it doesn't meet the requirements.
4. Roughness of jointing: the mortar joint should be eliminated, so that the mortar joint depth is consistent, the mortar joint handover is smooth and the surface is clean.
5. Loose packing: Compaction shall be carried out in strict accordance with the requirements of packing soil quality, dryness, soil spreading thickness of each layer and compaction technology (overlapping soil spreading, compaction times, etc.). ).
(2) Potential safety hazards and preventive measures:
1. Before operation, you must check whether the working environment meets the safety requirements (whether the slope is stable), whether the roads are smooth, whether the machines and tools are intact and firm, and whether the safety facilities and protective equipment are complete. Only after inspection meets the requirements can construction be started.
2, build by laying bricks or stones foundation, should often check and pay attention to the change of foundation pit soil, cracks. Gravel materials piled up should be far away from the pit edge 1m or more.
3. When the wall masonry height exceeds 65438+ 0.2m above the ground, scaffolding shall be erected.
4. The stacking amount on the scaffold shall not exceed the specified load, and there shall be no more than two operators on the same scaffold.
5, scaffolding should take a ramp ladder. Don't stand on the wall to draw lines (hooks) and clean the wall.
6. Unstable tools or objects are not allowed to be used to lift the scaffold board.
7, chopped stone should face inward, to prevent the gravel jump out of cuts.
8. Hanging cages and ropes used for vertical transportation must meet the requirements and be firm and undamaged; Don't overload when lifting, and check it frequently, and handle it in time when problems are found.
9, in rainy days and after work every day, completes the rainproof measures, in case the rain washed away mortar, wall collapse.
10, when workers vertically transfer stones up and down, scaffolding should be set up, and the vertical plate width of the shelf should not be less than 60cm.
1 1. When hammering stones, check whether the hammer is broken and whether the hammer handle is firm. The hammer should be dropped along the pattern of the stone to avoid hurting people.
12, it is not allowed to decorate the stone on the top of the wall or on the shelf, so as not to shake the wall and affect the quality or the stone fragments fall off and hurt people.
13, it is forbidden to move stones on the wall by hand to avoid crushing or scratching fingers.
14. It is not allowed to build on the wall above the chest reluctantly, so as to avoid safety accidents caused by collision and collapse of the wall or accidental falling of stones.
As a basic structure, lime-fly-ash stabilized soil (hereinafter referred to as lime-fly-ash stabilized soil) has the advantages of strong integrity, high bearing capacity, high stiffness, good water stability and relative economy. Therefore, in municipal road engineering, grass-roots treatment is often used. This paper discusses the construction technology of lime-fly ash soil foundation from the aspects of construction preparation, on-site mixing, shaping, rolling and curing.
A, the construction preparation work
(1) Preparation of Road Trough
The quality of new road trench engineering should meet the standards of relevant municipal engineering construction. If it does not meet the requirements, it should be treated, and temporary drainage ditch should be dug in rainy season to facilitate drainage. When paving the old road, the soil and loose particles on the old road should be cleaned up; Dry areas need to be moistened with water; Local road grooves should be repaired and tamped first.
(2) Material requirements
1. Lime: finely ground quicklime powder or hydrated lime should be used, and the hydrated lime should be screened to remove ash blocks larger than 5 mm. The lime grade should be above Grade III, and the water content should not exceed 4%. Lime should be digested 5 ~ 7 days before using ash, and it is forbidden to use it with digestion. To digest lime, it is necessary to master the water consumption to fully digest lime, and keep the humidity (generally 20% ~ 35%) to avoid flying too dry or caking too wet (reference water consumption: the water consumption for digesting each ton of quicklime is generally 600 ~ 800 kg).
2. Fly ash: fly ash of grade 2 or above should be used, and the content of SiO2 _ 2, Al _ 2O _ 3 and Fe _ 2O _ 3 in fly ash should not exceed 70%, and the loss on ignition should not exceed 20%; The specific surface area of fly ash should be greater than 2500cm2/g or the total amount passing through 0.075mm sieve holes should be not less than 70%, and the total amount passing through 0.3mm sieve holes should be not less than 90%. When using wet fly ash, the water content should not exceed 35%. Wet fly ash should be delivered several days before use, so as to drain water and prevent rain or fly ash. When transporting dry fly ash, it is best to add a proper amount of water or transport it in a closed car to avoid ash.
3. Soil: cohesive soil with plasticity index of 10 ~ 20 is suitable; When lime is used to stabilize graded macadam, graded macadam and unscreened macadam without plasticity index, about 15% cohesive soil should be added; When testing cohesive soil with large plasticity index, it should be crushed. The maximum particle size of crushed soil should not be greater than 15 mm, the soil organic matter content is less than 10%, and it is not suitable to stabilize it with lime when the sulfate content exceeds 0.8%. Use special types of soil, such as graded gravel, sandstone, miscellaneous fill, etc. It should be decided by experiment. The crushing value of crushed stone or gravel shall meet the following requirements: the base of urban expressway and main road shall not be greater than 30%; The base used for secondary roads should not exceed 35%.
(3) Machines and equipment
(1) When the paver is used for construction: paver, vibratory roller, waterwheel, forklift, truck, etc. (2) When using grader for construction: bulldozer, grader, vibratory roller, waterwheel, forklift, truck, etc. (3) Tools: wheelbarrow, shovel, sieve, string, ruler, scraper, etc. (4) Measuring instruments: level, theodolite, steel rule, etc. (5) Testing instruments: sand filling bucket, deflectometer, core drilling machine, etc.
(4) batching
Generally speaking, batching methods can be divided into three types: (1) gravimetric method. According to the total dry weight of the mixed mixture and the water content of various materials, calculate the required wet weight of various materials, and then mix according to each wet weight. The gravimetric method is suitable for factory mixing. (2) Volume method. According to the weight ratio of the mixture, it is converted into a volume ratio, and the volume of various materials is measured in a container to mix the mixture. Volume method is suitable for factory mixing and artificial road mixing. (3) Layering method. According to the maximum dry bulk density of the mixture, the bulk density and water content of various materials and the compaction thickness of the mixture base, the loose paving thickness of various materials is calculated to control the paving thickness. Layered paving method is suitable for mechanical road mixing.
Second, the construction process
The construction process of lime-fly ash stabilized soil base is: material preparation, mixing, paving and shaping, compaction, testing, curing and acceptance.
(1) mixing
Manual mixing should adopt strip mixing method, that is, after the mixture is paved into strips, it moves forward while stirring. After stirring for 2 ~ 3 times, sprinkle the mixture evenly along the line according to the amount of water needed to approach the recent water content of the mixture, and then stir until it is uniform. Road and trough mixing should be carried out after layered paving. Tractors with multi-share plows and tractors with rotary plows or slotted disc harrows should be adopted, and the two machines should cooperate with cross mixing. When lime fly ash and lime fly ash soil are mixed, first turn it over with a tractor with multiple plows, and then break it up again with a rotary cultivator or slotted disc harrow to make it turn evenly. When lime and fly ash are mixed into the mixture, it is advisable to mix the fine materials first, then spread the coarse particles, and then mix them separately with a multi-plough. If the local mixing is uneven or the mixing is not in place, it can be assisted by manpower. Forced mixers, pulverizers, belt conveyors and forklifts are used for mechanical factory mixing. During operation, fly ash and lime (and soil) are first sent to the pulverizer by a belt conveyor according to a certain proportion, and then pulverized and mixed evenly. Then, fly ash and lime and a certain proportion of coarse particles (such as crushed stone) are sent to a forced mixer by a belt conveyor, and mixed evenly when the water content is slightly higher, and then the evenly mixed mixture is discharged to the yard for transportation. Uniformly mixed lime fly ash mixture should not contain soil, fly ash and lime particles larger than 25mm.
(2) Paving the road
The water content of the evenly mixed mixture is generally 2% of the optimal water content before paving and molding. According to the design section and loose paving thickness, the mixture will be spread evenly in the road groove. Its loose laying thickness is the compaction thickness multiplied by the compaction coefficient. The value of compaction coefficient shall be determined by trial paving. Generally, you can refer to the following ranges: (1) manual mixing and manual paving, and the mixture without coarse particles is1.7 ~ 2.0; The mixture containing coarse particles is 1.4 ~ 1.6. (2) Mechanical mixing and paving, the mixture without coarse aggregate is1.4 ~1.7; The mixture containing coarse particles is 1.2 ~ 1.4. When multi-layer paving, the upper mixture should be paved immediately after the lower layer is compacted. Before spreading the upper mixture, the lower surface can be wetted with water (continued on page 132) (continued on page 16 1). There are two paving methods, namely paver paving and grader paving.
(3) Compaction
Compaction thickness of lime fly ash mixture, the maximum is 20cm, and the minimum is 10cm. (1) When the water content of the mixture is appropriate, the rolling can be divided into three stages: initial rolling, secondary rolling and final rolling. (2) Initial compaction, secondary compaction and final compaction shall be carried out by steel wheel vibratory roller, and the tonnage of the roller shall be above 12t. (3) After paving and molding, the mixture shall be rolled within the full width immediately. Adopt tire type single steel wheel vibratory roller. The straight section is rolled from both sides to the middle, and the ultra-high section is rolled from the inside out. Each roller compaction shall overlap the previous roller compaction by 30mm, so that the entire thickness and width of each layer are completely and uniformly compacted to the specified density. (4) After compaction, the surface should be smooth, without wheel tracks or bulges, cracks, washboards and loose peeling, and the degree of compaction should meet the specified requirements. In the process of rolling, the surface of the mixture should always be moist. If the surface water evaporates too fast, a small amount of water should be added in time. (5) After each layer is rolled, the tester will measure the degree of compaction, and the surveyor will measure the elevation and make records. If it fails to meet the requirements, mechanical or manual leveling shall be adopted according to the actual situation to make it meet the requirements. (6) During the rolling process, the surface should always be moist, and the water content of aggregate should be controlled at the optimal water content 1% ~ 2%. After final pressing, the compaction degree and design elevation shall be inspected, and the next step of construction shall be carried out after meeting the requirements.
(4) medical care
After the completion of rolling, water should be sprayed immediately for health preservation, and the number of watering depends on the temperature, so as to keep the base surface moist. The curing period is usually 7 days. During the maintenance period, traffic should be closed, caterpillar vehicles are prohibited from passing, and motor vehicles are prohibited from turning around or braking at the grass-roots level.
Third, the special season construction measures
(1) winter construction
(1) The base shall stop construction one month before the first heavy freezing (-3℃ ~-5℃) to ensure that it will not be frozen before reaching the design strength. (2) When necessary, measures can be taken to improve the early strength and prevent the base from freezing. For example, 2% ~ 5% cement is added to the mixture instead of lime; Increase aggregate consumption within the specified range of mixture structure composition; Compaction shall be carried out with the lowest water content of rolling forming, and the lowest water content shall be less than the optimal water content 1% ~ 2%.
(2) Construction in rainy season
(1) Arrange the construction reasonably according to the weather forecast, so as not to construct in rainy days. (2) During construction in rainy season, lime, fly ash, etc. Should be covered, the material site should be well drained to prevent raw materials from being soaked by rain. (3) Reasonably arrange the length of the construction section, closely link each working procedure, concentrate on paving in sections, and take rain lime-fly ash stabilized soil (hereinafter referred to as lime-fly ash soil) as the base structure, which has the advantages of strong integrity, high bearing capacity, high rigidity, good water stability and relative economy. Therefore, in municipal road engineering, grass-roots treatment is often used. This paper discusses the construction technology of lime-fly ash soil foundation from the aspects of construction preparation, on-site mixing, shaping, rolling and curing.
A, the construction preparation work
(1) Preparation of Road Trough
The quality of new road trench engineering should meet the standards of relevant municipal engineering construction. If it does not meet the requirements, it should be treated, and temporary drainage ditch should be dug in rainy season to facilitate drainage. When paving the old road, the soil and loose particles on the old road should be cleaned up; Dry areas need to be moistened with water; Local road grooves should be repaired and tamped first.
(2) Material requirements
1. Lime: finely ground quicklime powder or hydrated lime should be used, and the hydrated lime should be screened to remove ash blocks larger than 5 mm. The lime grade should be above Grade III, and the water content should not exceed 4%. Lime should be digested 5 ~ 7 days before using ash, and it is forbidden to use it with digestion. To digest lime, it is necessary to master the water consumption to fully digest lime, and keep the humidity (generally 20% ~ 35%) to avoid flying too dry or caking too wet (reference water consumption: the water consumption for digesting each ton of quicklime is generally 600 ~ 800 kg).
2. Fly ash: fly ash of grade 2 or above should be used, and the content of SiO2 _ 2, Al _ 2O _ 3 and Fe _ 2O _ 3 in fly ash should not exceed 70%, and the loss on ignition should not exceed 20%; The specific surface area of fly ash should be greater than 2500cm2/g or the total amount passing through 0.075mm sieve holes should be not less than 70%, and the total amount passing through 0.3mm sieve holes should be not less than 90%. When using wet fly ash, the water content should not exceed 35%. Wet fly ash should be delivered several days before use, so as to drain water and prevent rain or fly ash. When transporting dry fly ash, it is best to add a proper amount of water or transport it in a closed car to avoid ash.
3. Soil: cohesive soil with plasticity index of 10 ~ 20 is suitable; When lime is used to stabilize graded macadam, graded macadam and unscreened macadam without plasticity index, about 15% cohesive soil should be added; When testing cohesive soil with large plasticity index, it should be crushed. The maximum particle size of crushed soil should not be greater than 15 mm, the soil organic matter content is less than 10%, and it is not suitable to stabilize it with lime when the sulfate content exceeds 0.8%. Use special types of soil, such as graded gravel, sandstone, miscellaneous fill, etc. It should be decided by experiment. The crushing value of crushed stone or gravel shall meet the following requirements: the base of urban expressway and main road shall not be greater than 30%; The base used for secondary roads should not exceed 35%.
(3) Machines and equipment
(1) When the paver is used for construction: paver, vibratory roller, waterwheel, forklift, truck, etc. (2) When using grader for construction: bulldozer, grader, vibratory roller, waterwheel, forklift, truck, etc. (3) Tools: wheelbarrow, shovel, sieve, string, ruler, scraper, etc. (4) Measuring instruments: level, theodolite, steel rule, etc. (5) Testing instruments: sand filling bucket, deflectometer, core drilling machine, etc.
(4) batching
Generally speaking, batching methods can be divided into three types: (1) gravimetric method. According to the total dry weight of the mixture and the water content of various materials, calculate the required wet weight of various materials, and then mix according to each wet weight. The gravimetric method is suitable for factory mixing. (2) Volume method. According to the weight ratio of the mixture, it is converted into a volume ratio, and the volume of various materials is measured in a container to mix the mixture. Volume method is suitable for factory mixing and artificial road mixing. (3) Layered method. According to the maximum dry bulk density of the mixture, the bulk density and water content of various materials and the compaction thickness of the mixture base, the loose paving thickness of various materials is calculated to control the paving thickness. Layered paving method is suitable for mechanical road mixing.
Second, the construction process
The construction process of lime-fly ash stabilized soil base is: material preparation, mixing, paving and shaping, compaction, testing, curing and acceptance.
(1) mixing
Manual mixing should adopt strip mixing method, that is, after the mixture is paved into strips, it moves forward while stirring. After stirring for 2 ~ 3 times, sprinkle the mixture evenly along the line according to the amount of water needed to approach the recent water content of the mixture, and then stir until it is uniform. Road and trough mixing should be carried out after layered paving. Tractors with multi-share plows and tractors with rotary plows or slotted disc harrows should be adopted, and the two machines should cooperate with cross mixing. When lime fly ash and lime fly ash soil are mixed, first turn it over with a tractor with multiple plows, and then break it up again with a rotary cultivator or slotted disc harrow to make it turn evenly. When lime and fly ash are mixed into the mixture, it is advisable to mix the fine materials first, then spread the coarse particles, and then mix them separately with a multi-plough. If the local mixing is uneven or the mixing is not in place, it can be assisted by manpower. Forced mixers, pulverizers, belt conveyors and forklifts are used for mechanical factory mixing. During operation, fly ash and lime (and soil) are first sent to the pulverizer by a belt conveyor according to a certain proportion, and then pulverized and mixed evenly. Then, fly ash and lime and a certain proportion of coarse particles (such as crushed stone) are sent to a forced mixer by a belt conveyor, and mixed evenly when the water content is slightly higher, and then the evenly mixed mixture is discharged to the yard for transportation. Uniformly mixed lime fly ash mixture should not contain soil, fly ash and lime particles larger than 25mm.
(2) Paving the road
The water content of the evenly mixed mixture is generally 2% of the optimal water content before paving and molding. According to the design section and loose paving thickness, the mixture will be spread evenly in the road groove. Its loose laying thickness is the compaction thickness multiplied by the compaction coefficient. The value of compaction coefficient shall be determined by trial paving. Generally, you can refer to the following ranges: (1) manual mixing and manual paving, and the mixture without coarse particles is1.7 ~ 2.0; The mixture containing coarse particles is 1.4 ~ 1.6. (2) Mechanical mixing and paving, the mixture without coarse aggregate is1.4 ~1.7; The mixture containing coarse particles is 1.2 ~ 1.4. When multi-layer paving, the upper mixture should be paved immediately after the lower layer is compacted. Before spreading the upper mixture, the lower surface can be wetted with water (continued on page 132) (continued on page 16 1). There are two paving methods, namely paver paving and grader paving.
(3) Compaction
Compaction thickness of lime fly ash mixture, the maximum is 20cm, and the minimum is 10cm. (1) When the water content of the mixture is appropriate, the rolling can be divided into three stages: initial rolling, secondary rolling and final rolling. (2) Initial compaction, secondary compaction and final compaction shall be carried out by steel wheel vibratory roller, and the tonnage of the roller shall be above 12t. (3) After paving and molding, the mixture shall be rolled within the full width immediately. Adopt tire type single steel wheel vibratory roller. The straight section is rolled from both sides to the middle, and the ultra-high section is rolled from the inside out. Each roller compaction shall overlap the previous roller compaction by 30mm, so that the entire thickness and width of each layer are completely and uniformly compacted to the specified density. (4) After compaction, the surface should be smooth, without wheel tracks or bulges, cracks, washboards and loose peeling, and the degree of compaction should meet the specified requirements. In the process of rolling, the surface of the mixture should always be moist. If the surface water evaporates too fast, a small amount of water should be added in time. (5) After each layer is rolled, the tester will measure the degree of compaction, and the surveyor will measure the elevation and make records. If it fails to meet the requirements, mechanical or manual leveling shall be adopted according to the actual situation to make it meet the requirements. (6) During the rolling process, the surface should always be moist, and the water content of aggregate should be controlled at the optimal water content 1% ~ 2%. After final pressing, the compaction degree and design elevation shall be inspected, and the next step of construction shall be carried out after meeting the requirements.
(4) medical care
After the completion of rolling, water should be sprayed immediately for health preservation, and the number of watering depends on the temperature, so as to keep the base surface moist. The curing period is usually 7 days. During the maintenance period, traffic should be closed, caterpillar vehicles are prohibited from passing, and motor vehicles are prohibited from turning around or braking at the grass-roots level.
Third, the special season construction measures
(1) winter construction
(1) The base shall stop construction one month before the first heavy freezing (-3℃ ~-5℃) to ensure that it will not be frozen before reaching the design strength. (2) When necessary, measures can be taken to improve the early strength and prevent the base from freezing. For example, 2% ~ 5% cement is added to the mixture instead of lime; Increase aggregate consumption within the specified range of mixture structure composition; Compaction shall be carried out with the lowest water content formed by rolling, and the lowest water content shall be less than the optimal water content 1% ~ 2%.
(2) Construction in rainy season
(1) Arrange the construction reasonably according to the weather forecast, so as not to construct in rainy days. (2) During construction in rainy season, lime, fly ash, etc. Should be covered, the material site should be well drained to prevent raw materials from being soaked by rain. (3) Reasonably arrange the length of the construction section, closely link each working procedure, and concentrate on paving in sections to achieve compaction before rain.
Do compaction before.