Steel sheet pile construction is not as simple as you think. If you want good construction results, details are indispensable.
1. General requirements
1. The location of the steel sheet piles must meet the design requirements to facilitate the earthwork construction of the trench foundation, that is, there is room for formwork support and removal outside the most prominent edge of the foundation.
2. The support plane layout shape of the foundation pit trench steel sheet piles should be as straight and neat as possible, and irregular corners should be avoided to facilitate the use and support setting of standard steel sheet piles. The surrounding dimensions should be combined with the board module as much as possible.
3. During the entire foundation construction period, during construction operations such as excavation, hoisting, reinforcing steel bars, and concrete pouring, it is strictly prohibited to collide with supports, arbitrarily dismantle supports, arbitrarily cut or weld on supports, and heavy equipment should not be placed on supports. things.
2. Support line measurement
According to the design cross-section width requirements for foundation pit and trench excavation, the steel sheet pile driving position line is measured and released, and the steel sheet pile driving position is marked with white lime.
3. Steel sheet pile entry and storage area
Organize the entry time of steel sheet piles according to the construction progress plan or site conditions to ensure that the construction of steel sheet piles meets the schedule requirements. The stacking positions of steel sheet piles are scattered along the support lines according to the construction requirements and site conditions to avoid centralized stacking together to cause secondary damage. portage.
4. Steel sheet pile construction sequence
Positioning and laying out – digging trenches – installing guide beams – driving steel sheet piles – dismantling guide beams – construction of purlins and supports – earth excavation – foundation construction (power transmission belt) – removal of supports – construction of the main structure of the basement – earthwork backfilling – Removal of steel sheet piles—treatment of gaps after steel sheet piles are pulled out
5. Inspection, hoisting and stacking of steel sheet piles
1. Inspection of steel sheet piles
For steel sheet piles, there are generally material inspections and appearance inspections in order to correct unsatisfactory steel sheet piles and reduce difficulties in the piling process.
(1) Appearance inspection: including surface defects, length, width, thickness, end rectangle ratio, straightness and lock shape, etc. Note:
a. Welding parts that affect the driving of steel sheet piles should be cut off;
b. Cut holes and section defects should be reinforced;
c. If the steel sheet pile is severely corroded, its actual section thickness should be measured. In principle, all steel sheet piles should be inspected for appearance quality.
(2) Material inspection: Conduct a comprehensive test on the chemical composition and mechanical properties of the steel sheet pile base material. Including chemical composition analysis of steel, tensile and bending tests of components, lock strength tests and elongation tests, etc. Each specification of steel sheet pile shall be subjected to at least one tensile and bending test: two specimen tests shall be conducted for each steel sheet pile weighing 20-50t.
2. Steel sheet pile lifting
The two-point lifting method should be used to load and unload steel sheet piles. When lifting, the number of steel sheet piles lifted each time should not be too many, and attention should be paid to protecting the lock to avoid damage. The lifting methods include bundle lifting and single lifting. Bundle lifting usually uses steel ropes, while single lifting often uses special spreaders.
3. Stacking of steel sheet piles
The place where the steel sheet piles are stacked should be selected on a flat and solid site that will not cause large settlement deformation due to pressure, and it should be easy to transport to the piling construction site. When stacking, please pay attention to:
(1) The order, location, direction and plane layout of stacking should be taken into consideration for future construction;
(2) Steel sheet piles are stacked separately according to model, specification and length, and signs are set up at the stacking place;
(3) Steel sheet piles should be stacked in layers, with the number of piles in each layer generally not exceeding 5. Sleepers should be placed between each layer. The spacing between the sleepers is generally 3~4m, and the upper and lower layer of sleepers should be on the same vertical line. The total height of stacking should not exceed 2m.
6. Installation of guide frame
In steel sheet pile construction, in order to ensure the correct position of the pile axis and the verticality of the pile, control the driving accuracy of the pile, prevent buckling deformation of the sheet pile and improve the penetration capacity of the pile, it is generally necessary to set up a certain stiffness, Strong guide frame, also called “construction purlin”.
The guide frame adopts a single-layer double-sided form, which is usually composed of guide beams and purlin piles. The spacing of the purlin piles is generally 2.5~3.5m. The distance between the double-sided fences should not be too large. It is generally slightly larger than the sheet pile wall. The thickness is 8~15mm. When installing the guide frame, you should pay attention to the following points:
(1) Use theodolite and level to control and adjust the position of the guide beam.
(2) The height of the guide beam must be appropriate, which is conducive to controlling the construction height of steel sheet piles and improving construction efficiency.
(3) The guide beam cannot sink or deform as the steel sheet piles are driven deeper.
(4) The position of the guide beam should be as vertical as possible and should not collide with the steel sheet piles.
7. Steel sheet pile driving
The construction of steel sheet piles is related to construction water tightness and safety, and is one of the most critical processes in the construction of this project. During construction, the following construction requirements should be paid attention to:
(1) Steel sheet piles are driven by a crawler excavator. Before driving, you must be familiar with the conditions of underground pipelines and structures, and carefully lay out the accurate center line of the supporting piles.
(2) Before piling, inspect the steel sheet piles one by one and remove the rusted and severely deformed steel sheet piles at the connecting locks. They can only be used after they have been repaired and integrated. Those that are still unqualified after repairs are prohibited.
(3) Before piling, grease can be applied to the lock of the steel sheet pile to facilitate the driving and pulling out of the steel sheet pile.
(4) During the driving process of steel sheet piles, the slope of each pile is monitored along with the measurement. When the deflection is too large and cannot be adjusted by the pulling method, it must be pulled out and driven again.
(5) Tightly fasten and ensure that the soil is not less than 2 meters after excavation to ensure that the steel sheet piles can be closed smoothly; especially corner steel sheet piles should be used at the four corners of the inspection well. If there are no such steel sheet piles, use old tires or rotten steel sheet piles. Auxiliary measures such as plugging seams should be properly sealed to prevent water leakage from taking away sediment and causing ground collapse.
(6) During the excavation of the foundation trench, observe the changes of the steel sheet piles at any time. If there is obvious overturning or uplift, immediately add symmetrical supports to the overturned or uplifted parts.
8. Removal of steel sheet piles
After the foundation pit is backfilled, the steel sheet piles must be removed for reuse. Before removing steel sheet piles, the sequence and time of pulling out piles and soil hole treatment should be carefully studied. Otherwise, due to the vibration of pile pulling out and too much soil on the pile pulling out, it will cause ground settlement and displacement, which will bring harm to the constructed underground structure and affect the safety of nearby original buildings, buildings or underground pipelines. , it is very important to try to reduce the soil removal of piles. At present, water and sand filling measures are mainly used.
(1) Pile pulling method
This project can use a vibrating hammer to pull out piles: the forced vibration generated by the vibrating hammer is used to disturb the soil and destroy the cohesion of the soil around the steel sheet piles to overcome the pile pulling resistance, and rely on the additional lifting force to pull out the piles.
(2) Things to note when pulling out piles
a. The starting point and sequence of pulling out piles: For closed steel sheet pile walls, the starting point for pulling out piles should be at least 5 away from the corner piles. The starting point for pile extraction can be determined according to the situation during pile sinking, and the jumping method can also be used if necessary. It is best to pull out the piles in the reverse order to driving them.
b. Vibration and vibration pulling: When pulling out piles, you can first use a vibrating hammer to vibrate the sheet pile lock to reduce soil adhesion, and then pull out while vibrating. For sheet piles that are difficult to pull out, you can first use a diesel hammer to vibrate the pile down 100~300mm, and then alternately vibrate and pull out the pile with a vibrating hammer.
c. The crane should be gradually loaded with the start of the vibrating hammer. The lifting force is generally slightly less than the compression limit of the shock absorber spring.
d. The power supply for the vibrating hammer is 1.2~2.0 times the rated power of the vibrating hammer itself.
(3) If the steel sheet pile cannot be pulled out, the following measures can be taken:
a. Hit it again with a vibrating hammer to overcome the resistance caused by the adhesion to the soil and the rust between the bites;
b. Pull out piles in the reverse order of sheet pile driving;
c. The soil on the side of the sheet pile that bears soil pressure is denser. Driving another sheet pile near it will allow the original sheet pile to be pulled out smoothly;
d. Make grooves on both sides of the sheet pile and put in soil slurry to reduce resistance when pulling out the pile.
(4) Common problems and solutions during steel sheet pile construction:
a. Incline. The reason for this problem is that the resistance between the pile to be driven and the lock mouth of the adjacent pile is large, while the penetration resistance in the direction of pile driving is small. The treatment methods include: using instruments to check, control and correct at any time during the construction process; using steel wire ropes when tilting occurs. Pull the pile body, pull and drive, and gradually correct; make appropriate allowances for the sheet piles that are driven first.
b. Twist. The reason for this problem: the lock is a hinged connection; the solution is: use a clamping plate to lock the front lock of the sheet pile in the direction of piling; set up a pulley bracket in the gap on both sides between the steel sheet piles to stop the sheet pile Rotation during sinking; fill in both sides of the locking hasps of the two sheet piles with shims and wooden tenons.
c. Commonly connected. The cause: the steel sheet pile tilts and bends, which increases the resistance of the notch; the treatment methods include: correcting the tilt of the sheet pile in time; temporarily fixing the adjacent driven piles with angle iron welding.
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Post time: Nov-29-2023