Steel sheet pile inspection.

Material and appearance inspections are conducted for sheet pile construction, and for welded sheet piles, the welding joints must also be checked. Sheet piles in the foundation pit are used for temporary support structures, primarily through visual inspections to correct sheet piles that do not meet shape requirements, in order to reduce difficulties in pile foundation construction.

(1) Appearance inspection.

Including surface defects, length, width, height, thickness, rectangular proportions, flatness, and lock mouth shape. During inspection, attention should be paid to: Weldments affecting the steel sheet pile when immersed should be cut off and reinforced if there are cuts or defects in the cross-section. If the steel sheet pile has severe rust, measure its actual cross-sectional thickness to determine whether further calculations for reduction are necessary. The principle is to conduct an external inspection of all steel sheet piles.

Material Inspection.

The company tested the chemical composition and mechanical properties of steel sheet pile billets. The main contents include steel chemical composition analysis, tensile tests of components, bending tests, steel sheet pile construction locking strength tests, and elongation tests. Each specification of steel sheet pile must undergo at least one tension-bending test. Two tests are conducted for every 25-50t steel sheet pile.

2. Sheet pile installation.

Steel pile positions should facilitate foundation construction, meaning that, beyond the edges of infrastructure connections, formwork space should be left. If steel sheet piles are used as the outer box formwork, it is necessary to employ other isolation materials such as fiberboard. When removing the steel sheet piles, their flat layout should be as even and orderly as possible, avoiding irregular tilt angles, to ensure the full utilization of the steel sheet piles and facilitate support. (Detailed location see Figure)

3. Sheet pile repair.

Sheet pile construction is a material that is used in multiple cycles and can deform, sustain damage, or exceed the deviations listed in the table below. It should be corrected and repaired before use.

The method is as follows:

Surface Defect Repair.

Surface rust and oil stains near the defects should be thoroughly cleaned, followed by welding repairs, and then sanded with a grinding wheel.

(2) End face correction.

In typical cases, the ends of some piles are cut using oxygen-acetylene, ensuring the end face is perpendicular to the axis, followed by smoothing the cut surface with a grinding wheel. In cases with minimal trimming, the grinding wheel can also be used directly for repairs.

(3) Correction of桩身弯曲.

Cold bending correction of the protrusions on steel sheet piles is typically performed on a specialized correction platform, utilizing jacks on the overhead gantry beam to achieve the correction.

(4) Pile Distortion Correction

This correction is more complex and can be addressed using the methods outlined in point 3 above.

Local deformation correction of piles.

Local deformation areas are corrected using oxygen-acetylene hot baking, jacking with a jack, and hammering with a sledgehammer.

(6) Locking Mechanism Deformation Correction.

The sheet pile construction is used as a lock-forming mold, with adjustments made using a slow-lifting winch or by employing oxygen-acetylene heat treatment, hammer striking to push the mold straight.

4. Guide rail installation.

Guideways are typically composed of guide beams and guide piles, coming in single-sided and double-sided configurations in the plane, and in single-layer and double-layer heights. The commonly used type is the single-layer double-sided guide rail (as shown in the figure below). The spacing of the guide frame is generally 2.5-3.5 meters, with the double-sided guide frame spacing usually 8-15mm higher than the pile height.

Guidance frames must not come into contact with steel sheet piles. The guidance frame cannot be sunk or deformed on top of steel sheet piles. Use an appropriate beam height, control the construction height of the steel sheet piles reasonably, improve work efficiency, and use theodolites and levels to control the position and elevation of the guidance beam.

5. Steel sheet pile driving and removal.

The entry method for single-row pile selection is to start from one corner of the pile and continue driving them piece by piece until the project is completed. This method is simple, fast, and does not require additional supporting structures, but it is prone to tilting the piles to one side and cumulative errors are difficult to correct. Therefore.

Suitable for applications with minimal requirements for sheet piles and where the pile length is not extensive.

(1) Sheet pile driving construction as shown in the figure below):

First, use a crane to lift the steel sheet piles to the pile point, then align the lock during the insertion. After each sheet pile is inserted, fit a pile cap and gently hammer it. For the second round of piling, to ensure the verticality of the steel sheet piles, use two theodolites to control in two directions. To prevent the centerline of the lock from shifting in the plane, place a stopper at the lock of the sheet piles during the piling direction to prevent displacement. At the same time, the position of each sheet must be pre-calculated for easy checking and adjustment at any time.

**The segment pile should be driven in stages; the insertion position and direction of the segment pile must ensure accuracy. It can serve as a template guide, and generally, a measurement should be taken after every 1-meter drive.**

(2) Sheet Pile Extraction Method.

Vibration piles are extracted by mechanically exciting the vibration of steel sheet piles, overcoming or weakening the pile pull-out resistance, and pulling the piles out. For pile extraction, 11~15KW steel rebars, U-shaped steel sheet piles, and lengths of 6 meters are used.

Please note the following precautions when removing steel piles:

Understand the detailed soil conditions and pile driving status prior to steel sheet pile construction. After excavation of the foundation pit, judge the difficulty of pile removal based on the deformation of the sheet piles.

Following the completion of the excavation pit construction, backfilling should be carried out to balance the soil pressure on both sides of the sheet piles as much as possible, which is conducive to the pull-out operation.

The pile puller has a certain weight and its structural bearing capacity below is calculated. For instance, when subjected to pressure in soil layers, due to the large ground load, it is necessary to place a subgrade box or sleepers underneath the equipment when required.

d. Important pipelines and high-voltage cables within the scope of work should be carefully monitored and protected.

Sheet pile removal can create voids that must be filled promptly to prevent displacement of structures and facilities nearby, as well as ground settlement.

f. If the steel plate cannot be removed, the following measures can be taken:

(a) Perform a second strike with a vibration hammer to overcome resistance caused by the adhesion to soil and rust between the striking face and the bit.

(b) In the reverse order of the pile driving sequence.

(c) The soil layer on one side of the sheet pile is denser and is driven alongside another sheet pile nearby, allowing the original sheet pile to be easily extracted.

(d) Slots are cut on both sides of the pile, and the expansive soil slurry is placed to reduce resistance during pile extraction.

Common Issues and Solutions in Sheet Piling Construction