(1) Main technical requirements
1, the drilling rig or jet grouting machine should sit upright and steady, the vertical shaft or rotary table should be aligned with the hole position, and the inclination angle and design error should generally not be greater than 0.5.
2. Before jet grouting, check the high-pressure equipment and piping system. The pressure and displacement of the equipment must meet the design requirements. The sealing ring of pipeline system must be good. There shall be no sundries in each channel and nozzle.
3. Attention should be paid to the preparation work during jet grouting, and the grouting pump should be started. It is estimated that after the cement mortar striker has flowed out of the nozzle, the grouting pipe will be pushed. Jet grouting is carried out from bottom to top.
4, jet grouting, boot sequence should also comply with the provisions of article 3. At the same time, the hole section of the jet grouting hole should overlap the front section by 0. 1m to prevent the consolidated body from overlapping.
5. After the jet grouting operation, due to the water diversion of the slurry, it will generally shrink in different degrees, resulting in a cavity at the top of the solid. Therefore, the cement slurry with water cement ratio of 0.6~ 1 should be replenished in time, and dirt or sundries excluded from other drilling holes should be prevented from entering.
6. In order to increase the size of the consolidated body, or to avoid the reduction of the size of the consolidated body in deep hard soil, measures such as increasing grouting pressure, pumping capacity or reducing rotation and lifting speed can be adopted, and reinjection technology can also be adopted.
7, technical requirements and quality standards
(1) In the process of construction, the quality of grout should be checked frequently. Under normal circumstances, during the construction of each pile, the slurry concentration should be sampled and detected twice with a slurry hydrometer, and the detection records should be made.
② During construction, the length of drill pipe should be measured for each pile to control the pile length to meet the design requirements.
(3) after construction, the integrity, uniformity and unconfined compressive strength of single pile should meet the design requirements. Check the number of not less than 2‰ of the total number of piles, and not less than 3.
④ After the construction of high-pressure jet grouting pile is completed, the bearing capacity of its composite foundation should meet the design requirements. Check the number of not less than 2‰ of the total number of piles, and not less than 3.
⑤ The allowable deviation of finished piles meets the standard inspection requirements.
Allowable deviation, inspection quantity and inspection of high-pressure jet grouting pile construction
No. Inspection Item Allowable Deviation Inspection Quantity Inspection Method 1 Pile location (vertical and horizontal direction) 50mm pressed into the pile. 10% of the total number of inspections, and each inspection skin shall be no less than 5 theodolite or steel ruler to measure the verticality of 2 piles 1% theodolite or messenger wire to measure the inclination of drill pipe 3. The effective diameter of the pile is not less than the design value. After the excavation depth is 50- 100cm, measure with steel ruler (2) Key points of construction quality control.
1, the construction shall be carried out in strict accordance with the determined parameters and technical requirements, and the process parameters shall not be changed without the consent of technicians.
According to the process test, in view of the geological conditions in this area, combined with the construction machinery and equipment, the construction method of drilling and grouting with geological drilling rig first, and then drilling and grouting with VY-60 drilling rig was determined. Several key process parameters are determined as follows. Construction shall be carried out in strict accordance with the approved test parameters, and the process parameters shall not be changed at will.
(1) When grouting, the lifting speed of drill pipe is 20 cm/min;
(2) When grouting, the rotation speed of drill pipe is 20r/min；;
(3) grouting high pressure grouting pump pressure 35MPa, catheter pressure 0.8MPa.
2. The design depth of pile completion refers to the drilling depth determined by the bearing stratum that meets the design requirements according to the geological conditions determined by geological drilling recheck. 50cm pile head should be reserved during grouting and spraying construction to prevent slurry solidification and shrinkage from affecting the elevation of construction pile top.
3. Pay attention to continuous and even lifting during jet grouting. No matter what causes the jet grouting to stop, it is necessary to drill more than 500mm for connection during jet grouting to prevent the pile body from being out of touch with mud and sand.
4, in the process of high-pressure jet grouting, when the pressure suddenly increases or decreases, a large number of slurry leakage or no slurry, should stop jet maintenance in time, find out the reason, take corresponding measures.
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