Introduction of pile foundation construction technology?

Speaking of pile foundation construction lofting, what is the technological process of pile foundation construction at this stage? What is the basic profile? The following is the related content of pile foundation construction technology compiled by Zhong Da Consulting Company, and the basic situation is as follows:

In order to help construction enterprise personnel understand the technological process of pile foundation construction, Zhong Da consulted and compiled relevant information, and the basic contents are as follows:

Construction process flow

The technological process of hammering pipe pile construction is as follows: measuring and setting out → rechecking pile position → positioning adjustment of pile driver → pile positioning, three-center alignment → two-way adjustment of verticality → pile sinking → pile connection → pile sinking → pile delivery → hammer retraction → pulling out the pile driver to block the pile mouth → completing an engineering pile.

work progress

Surveying and setting out: measure and locate the building according to the requirements of the red line, and it can only be used after the relevant personnel such as Supervisor A check and sign the survey baseline, leveling points, control points and pile positions.

According to the survey control points and design drawings provided by the construction unit, measure and calibrate the center points of each pile position, drive short steel bars supplemented by eye-catching signs, measure and release the site elevation, and report the measurement and positioning results to the supervisor or the construction unit for review and acceptance before starting work. The error of measuring and setting the pile position is not more than 20mm, and the surveyors should recheck the short steel bar head before pile sinking in the construction process, so as to avoid the soil uplift caused by pile sinking and pile driving by the pile machine from affecting the pile position accuracy. After the pile construction, it needs to be tracked for two to three days to determine whether the soil is displaced and whether the vibration squeezing effect is strong.

The construction process of hammering pipe piles is as follows:

(1), the pile driver moves to the designated pile position. Before piling, the pile platform must be leveled, and after it is in place, the pile crane should be placed in the pile cap to ensure that the hammer, the pile cap and the pile are in a vertical line, and the pile cap has good contact with the pile top. Check the verticality and pile position deviation of the pile. Only when the verticality is less than 0.5% and the deviation of pile position is not more than 20mm can the pile be sunk, and if necessary, the pile can be pulled out and inserted again.

(2) Start the diesel hammer to start piling; The pile pad should be made of paper pad or plastic products with the thickness of 100mm, so as to avoid stress concentration and damage to the pile head, and it should be replaced in time, and the pile should be driven with a heavy hammer at low spacing. After the first pile sinking process is completed, the pile is welded, and then the second and third pile sinking processes are repeated, thus completing the construction process of a pile. During the construction process, the adjustment and control of pile verticality are completed by the pile driver and the host operator. The pile driver observes the horizontal verticality of the pile through the vertical ball command, and the host operator observes the vertical verticality of the pile through the vertical ball. Check the verticality of pile body at any time during pile sinking. If the verticality is greater than 0.8%, find out the reason and try to correct it. When the pile tip reaches the hard soil layer, it is forbidden to correct the deviation by moving the pile frame. When the pipe pile encounters a thick silt layer or soft backfill soil as soon as it is inserted into the topsoil, a diesel hammer (empty hammer) without ignition should be used, and a hydraulic hammer should be used to make the pipe pile slowly sink. When pile sinking is difficult, check whether the drop hammer is inclined and eccentric, especially whether the pile pad and pile cap are suitable. If not, replace or supplement the cushion. Each pile should be driven continuously once, without interruption, so as not to be difficult to continue piling.

Pile connection: the pile foundation joint of this project adopts electric welding joint, and welding operation can only be carried out after the verticality adjustment of the upper pile is completed. Before welding, the steel brush shall be used to clean the oil, rust, dirt and other impurities on the surface of the end plate, and the groove shall be brushed until the metallic luster is exposed; When welding the upper and lower sections of piles, the lower section of pile head should be exposed to the ground for 50- 100mm for welding operation. When connecting piles, 4 ~ 6 points shall be fixed by spot welding first, and then welded symmetrically by two welders to ensure the quality and size of the weld. Welding downtime, plane deviation of upper and lower piles and flatness of pile top shall meet the following conditions:

(1), after welding, pile driving can only continue after natural cooling. It is forbidden to cool with water after welding and start pile sinking;

(2) Weld seam of electric welding pile: the undercut depth of weld seam is ≤0.5m, and the dislocation of upper and lower ends is ≤3mm. The appearance of welding quality of weld seam is: no air hole, no flash and no crack. See specification requirements (GB50202-2002) for details.

Pile delivery: according to the pre-measured site elevation, send it to the designed pile top elevation with an error of 5 cm. Measure and correct the verticality of the pile feeding device to avoid unnecessary bending moment caused by eccentric compression of the pile section. Check whether the pipe pile is full of water in advance when sending the pile or re-driving. If the pipeline is full of water, some water should be pumped out before driving.

Double control shall be strictly implemented in the hammer-receiving standard of engineering piles, with the last three rows 10 penetration at 20-40mm as the main control index and the depth of pile tip entering the bearing stratum as the reference. The stacker has been marked with scales. By observing the measuring scale at the later stage of pile delivery, the penetration of the last three rows 10 blow is calculated and filled in the construction record.

After the construction of the engineering pile is completed, the hole of the pipe pile is blocked with a wooden board slightly larger than the inner wall of the pipe pile to prevent the soil around the pile from falling into the hole.

In case of shutdown under special circumstances during construction, the person in charge of the project or technology will take the initiative to negotiate with the owner, design and supervision representatives on the spot for treatment measures: (1), sudden penetration; (2) The pile body suddenly inclines and shifts; (3) There is obvious crack, peeling or damage at the pile end of the pile body; (4) The ground is obviously uplifted, and the pile position marks are obviously displaced; (5) According to the determined pile length, it is expected that when the pile is delivered to the design elevation of the pile top, if the penetration cannot meet the requirements, the pile delivery should be suspended before the pile end is buried, and the machine should be stopped immediately. The builder or project leader should report to the owner, the design sheet supervision unit and other representatives to the site for textual research and processing, and make records. The pile body should not be moved in advance or handled without authorization.

Construction sequence arrangement: pile pressing sequence is an important prerequisite for reasonable pile pressing, which has a great relationship with pile piling and site layout. When determining the pile pressing sequence of this project, we have considered the factors such as the supply conditions of piles, lifting conditions, the movement of pile frame that does not hinder the swing space of crane, and the influence of pile pressing and soil squeezing on the surrounding area. In the whole pile pressing process, the pile driver adopts the straight-line walking route to make the construction quality and progress reach the best state. According to the engineering geological conditions of the site and the influence of pile sinking and soil squeezing effect, our company has formulated the following construction sequence: first construct the main building, then construct the engineering piles in the basement, and arrange them according to the basic principles of first deep and then shallow, first long and then short, first low and then high, and first group and then single. During the construction of engineering piles in the main building, the construction should be carried out from the west first, and then from the east to the back, so as to ensure that the soil squeezing effect caused by vibration during the construction of engineering piles is minimized.

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