4.2 Technical requirements for post-grouting construction of cast-in-place piles
4.2. 1 control parameters of post-grouting construction
(1) The initial operation time of post-grouting can generally be carried out 2 days after the completion of the foundation pile, and the specific time can be adjusted according to the construction situation of the foundation pile, but generally it should not exceed 30 days after the pile is completed (in case of special circumstances, grouting can be carried out in advance); '
(2) The quality control of post-grouting adopts the double control method of grouting quantity and grouting pressure, with the grouting quantity as the main control and the pumping termination pressure as the auxiliary control;
(3) The cement is P.O 32.5 cement, and the grouting water-cement ratio is 0.60 ~ 0.75;
(4) Cement pressure and pumping termination pressure are as follows:
Pile type, pile diameter/effective pile length, grouting at each pile end and grouting at each pile side.
Cement pumping pressure
Grouting pile1000 mm/36.50 m&; 38.00m1600 ~1800kg ≮ 2.0mpa 600 ~ 800kg ≮1.5mpa.
Specific construction control standards:
A. The cement pressure reaches 70% of the design value in the table, and grouting can be stopped when the pumping pressure exceeds 6.0MPa;
B the cement injection amount reaches 70% of the design value in the table, and the pump pressure is less than 70% of the predetermined pressure in the table.
, should lower the water cement ratio, continue grouting to reach the predetermined pressure;
C. If the cement slurry overflows from the pile side, the water cement ratio should be reduced and the cement pressure should be poured intermittently until the cement pressure meets the requirements in the above table.
4.2.2 Post-grouting pipeline setting
(1) The grouting valve at the pile end and pile side shall be made according to the patented product pattern of Foundation Research Institute of China Academy of Building Research. There are two grouting pipe at the pile end and a grouting pipe at the pile side (see the grouting device diagram for details).
(2) The grouting conduit shall be a welded pipe for conveying low-pressure fluid in line with national standards. The nominal diameter of the grouting conduit at the pile tip is φ25( 1'), and the wall thickness is 3.25mm (note: the actual wall thickness of the steel pipe shall not be less than 3.25mm); Guide for grouting on pile side. The nominal diameter of the pipe is φ20(3/4') and the wall thickness is 2.75mm；; The nominal diameter of the welding sleeve of the grouting conduit at the pile end is φ32, and the wall thickness is 3.25mm.
(3) The setting of grouting conduit is shown in the detailed drawing, and the key points are as follows (see attached figure):
A, the upper end of a grouting conduit is provided with a pipe thread, a pipe hoop and a plug; G 1' thread and a pipe hoop for tightening the grouting valve at the pile end are arranged at the lower end of the pile end grouting conduit; The lower end of the pile-side grouting conduit is provided with G3/4' thread and a tee for inserting the pile-side grouting valve.
B. The connection of grouting conduit shall be welded by casing, and the welding shall be continuous and airtight, and the weld seam shall be full and uniform, and there shall be no air holes or sand holes (each solder joint shall be knocked off to check the welding quality, and the next working procedure can be carried out only after it meets the requirements).
C grouting conduit and reinforcing cage are fixed by 12 lead wire cross binding method. Binding should be firm, binding point should be uniform. The grouting conduit at the pile end is bound at the inner side of the stiffening hoop, and the binding fixing point is at each stiffening hoop; The grouting conduit at the pile side is bound on the outer side of the spiral stirrup, and the spacing between binding points is1.5m.
D the upper end of the grouting conduit shall be not less than 200mm under the pile construction floor (it can be slightly adjusted according to the specific situation); The lower end of the pile tip grouting conduit is 400mm away from the longitudinal cage bottom of the reinforcing cage. (Note: The bottom hoop of the reinforcing cage should also be adjusted here; The elevation of the lower end of the grouting conduit at the pile side is about -34.30m, which is 10m away from the cage bottom. )
E, inserting a grouting valve at the side of the pile in the process of hoisting the reinforcing cage into the hole, and welding the grouting conduit at the empty hole section of the pile before the reinforcing cage is finally positioned;
F the reinforcing cage shall not be twisted and collided downwards repeatedly during hoisting; The reinforcing cage must sink to the bottom, and cannot be suspended!
G. After the pile concrete is poured and the vertical holes are backfilled, obvious signs should be inserted, and vehicles are strictly prohibited from rolling.
4.2.3 Post-grouting mechanical equipment
(1) grouting pump adopts 3SNS high-pressure grouting pump with rated pressure not less than 8MPa, rated flow rate of 76L/min and power 18kW.
(2) grouting pump control monitoring pressure gauge is 2.5 16MPa seismic pressure gauge.
(3) The slurry mixer is YJ-340 slurry mixer matched by grouting pump, with a volume of 0.34m3 and a power of 4kW.
(4) The cement slurry conveying pipe shall be a high-pressure fluid pumping hose with rated pressure not less than 8MPa.
4.2.4 Post-grouting construction materials
The cement used for grouting is marked as P.O 32.5, and the cement shall meet the requirements of relevant technical specifications.