Gravel Foundation
1 scope
This technology is applicable to industrial and civil construction of gravel Foundation, Foundation treatment and ground cushion (solid and rolling method).
2 construction preparation
2.1 materials and equipment:
2.1.1 naturally graded gravel or graded gravel: should be adopted hard sand, coarse sand coarse sand, gravel sand, crushed (eggs) stone, stone chips or other industrial waste aggregates. In lack, coarse sand and gravel areas, sand can be used, but should be at the same time adding a certain amount of gravel or pebbles, its content should comply with the design requirements. Particle size distribution should be good.
2.1.2 graded gravel materials shall not contain roots, leaves, organic debris and plastic bags and other garbage. When used as drainage consolidation, mud weight should not be more than 3%. Maximum particle size must not be greater than gravel or pebbles cushion thickness 2/3 or virtual shops, and should not be greater than 50mm.
2.1.3 equipment: General should have wooden Rammer, frog or diesel ramming machine, bulldozer, road roller (6~10T), trolleys, a flat shovel, spray hose, 2m feet, small lines or fine wire, steel or wood joint by joint, and so on.
2.2 operating conditions:
2.2.1 setting control the thickness of paving flags, such as standard stakes or elevation or fixed on the walls of buildings, tanks and missile level elevation on the slope of the ditch line or Gao Mu jue horizontally on the nail.
2.2.2 in Foundation pit of underground water level is higher than (tank) of under side of engineering construction, drainage or lowering the underground water level of the measures should be taken to make pit (Groove) remain in the anhydrous State.
2.2.3 before paving, common inspection units should be organized, including level of axis dimensions, elevation, geology, if there are no holes, ditches, wells, tombs, etc. Prior to the Foundation should be disposed of and the hidden check formalities.
2.2.4 checking the base channel (pit), the stability of the trench slope and clear the surface of the substrate and water.
3 operational processes
3.1 process:
Inspection quality sprinkler → → → place in layers of sand gravel compacted or rolling → leveling acceptance
3.2 technical identification of graded gravel, artificial graded gravel, gravel should be mixed evenly, it shall meet the design requirements or the norms of quality.
3.3 place in layers of sand
3.3.l thickness of each gravel paving, usually 15~20 cm, should not exceed 30 cm, layer thickness control. Depending on the conditions, the choice of tamping or compacting method. A large area of sand-gravel cushion, paving thickness up to 35cm, 6~10T roller compaction should be adopted.
3.3.2 sand and gravel base should be laid on the same level, if the depth is not at the same time, soil should be dug into steps and slopes, Cha should take note (RAM) it. The construction should be carried out in the deep after the first order.
Subparagraph 3.3.3 when Cha should ramp, each branch office should be staggered, the horizontal distance of 0.5~1.0M and full pressure (RAM) it.
3.3.4 paved-gravel grading should be uniform. If sand pit/stone piles, the sand or stones should be excavated, filled respectively with a good sand.
3.4 water: paving grading gravel compacted before rolling, according to their level of wet and dry and weather conditions, watering appropriately in order to maintain optimum moisture content of the sand, usually 8%~L2%.
3.5 rammed or rolled; rammed or rolled a few times, determined by field tests. Water RAM or frog-type ramming machines should keep falling from 400~500mm, a dynamic compaction to a half RAM, line, and full tamp, normally no less than 3 times. Using roller rolling back and forth, rolling in no less than 4 times the track lap not less than 50cm. Edges and corners of artificial or frog-type ramming machine complement tamping.
3.6 find peace and acceptance:
3.6.l leveling construction should be layered and dynamic compaction-compacting and pure sands should be set check points, with 200cm3 cutting ring sampling; determination of density of dry sand. After passing the lower density, upper construction cancan be carried out. Penetration method for the determination of quality, penetrometer, bar checks or fork to penetration, less than the penetration tests to determine qualified.
3.6.2 final lamination (RAM) is completed, the surface should be line level, and should comply with the design requirements of the elevation.
4 quality criteria
4.1 project:
4.1.1 substrate soil must meet the design requirements.
4.1.2 pure sand dry sand mass density of the checkpoint, you must meet the requirements of specification for design and construction.
4.2 Basic project:
4.2. the right of ingredients with 1 sand, mix evenly, virtual shop thickness to comply with the requirements dynamic compaction-compacting.
4.2.2 Cha place hierarchy is correct, reasonable Cha dynamic compaction-compacting and leveling.
4.3 allowable deviation, as shown in table 2-4.
Gravel Foundation of tolerance table 2-4
Project tolerance (mm) test method
1
2 top level
Surface flatness of ± 15
20 level or cable and check
2m on foot and wedged feeler Gage check
5 finished product protection
5.1 when the backfill gravel, axis should pay attention to protect the site, standard height pile displacement for preventing collisions and should be repeated frequently.
5.2 should not leave holes within the Foundation. Completed without technical measures shall not affect the stability of excavations in the region.
5.3 construction must ensure slope stability, prevent the collapse.
5.4 night-time construction, should arrange the construction sequence, with adequate lighting; prevent super thick graded gravel or paving is not allowed.
After 5.5 survival of graded gravel should be continuous upper construction; or sprinkling water should frequently wet.
6 quality problems to be noticed
6.1 an area of sink: the main is not complying with the quality requirements, place in layers too thick, rolled a few times is not enough, the lack of water, and so on. To enforce a rigid process requirements.
6.2 local subsidence: edge and corner tamping is not solid, Cha wasn't required and tamp. On the corner of RAM may not be missing.
6.3 poor grading: should be equipped with special Casserole in a timely manner, issues such as stone, sand gradation is good.
6.4 in the foundations of sandstone below the underground water level, its paving thickness of the bottom can be adjusted 50mm.
6.5 the density does not meet the requirements: adhere to the layer check the quality of sand Foundation. Each layer of pure sand dry sand mass density of check points. Must conform to the rules, cannot be a layer of sand and construction.
6.6-gravel cushion thickness should not be less than 100mm; frozen natural sandstone may be used.
7 quality records
The standards should have two quality records:
7.1 report of the survey of the construction site.
7.2 ground rod sounding records
7.3 ground covert acceptance record.
7.4 test report of the sand.
