Common Problems in Construction of Steel Sheet Pile and the Solutions thereo

1 Penetration is difficult due to excessive pile driving resistance
This problem may occur for two reasons. First, due to the deformation and corrosion of steel sheet pile connecting lock notch, steel sheet pile fails to move downwards along interlock smoothly; in such a case, steel sheet pile body and interlock of steel sheet pile shall be inspected and treated before piling; second, the piling resistance is excessively high in solid sand layer; if that is the case, it is necessary to perform detailed analysis of geology, make study on possibility of penetration and drive the pile while injecting water to facilitate the sinking.
2 Sector-shaped inclination of sheet pile in travel direction
This kind of inclination would largely decrease when "folding screen method for pile sinking" is employed. Because the resistance at interlock connection with previous sheet pile is higher than the resistance of soil mass around empty interlock to the pile at the other side during the travel of sheet pile, the sheet pile cap moves in the direction of travel. In such a case, be sure to keep the steel sheet pile interlock unhindered and apply grease inside interlock so as to reduce resistance; mount steel sheet pile "stop" at surrounding purlin for construction in order to limit the movement of steel sheet pile cap in travel direction.
After the formation of sector-shaped inclination of steel sheet-pile wall body, adjustment shall be performed at the earliest opportunity using a wedge-shaped pile (narrow top, wide bottom) fabricated according to measured inclination data (adjust the straightness and smoothness of this pile and interlock).
3 Neighboring sheet pile is dragged in
The top cause of this problem is the excessive resistance at interlock connection. This problem could be solved by taking measures as stated in the section named "sector-shaped inclination of sheet pile in travel direction". Once the tendency of "neighboring pile drag-in" is detected, the dragged pile shall be connected to finished pile through welding so as to prevent drag-in.
4 Twisting of pile body
Since steel sheet pile interlock employs hinged connection, twisting may occur during insertion and hammering. Hence, it is necessary stop and rectify the twisting, or the deflection of central axis of sheet-pile wall may occur. To prevent the twisting of pile body, a "stop" could be mounted on surrounding purlin in travel direction of pile and compose a "limit" together with surrounding purlin so as to lock the position of interlock at the other installation side of steel sheet pile that is sinking. It should be noted that this "stop" shall be firmly lapped with surrounding purlin and that grease shall be applied to notch groove of this "stop" in a timely manner so as to facilitate the sinking of pile body.
5 Interlock leakage
After the establishment of steel sheet-pile wall, slight leakage may occur at hinged connection of interlock and is not allowable for permanent structure requiring high-level leakage resistance. Fill interlock with the mixture of butter, asphalt and dry sawdust (equal volume) before pile sinking so as to improve leakage resistance and facilitate the driving of sheet pile. In recent years, polyurethane based water expandable putty has been widely used to fill interlock during steel sheet-pile wall construction at ship yard so as to improve the leakage resistance.
6 Interlock slip-off
When steel sheet pile interlock is damaged or driving is not stopped when obstacle is met with, interlock slip-off may occur. Hence, all interlocks shall be inspected strictly before construction. When piling meets with obstruction, be sure to find out the causes and stop the driving immediately. Besides, squashing of pile bodies that occur when "folding screen method" is used may bring about interlock slip-off. To solve this problem, the "stop" of terminal steel sheet pile and the stiffening sheet and clamping sheet of Z-shaped built pile could be removed before pile driving by "folding screen method" so as to relieve the compression force of sheet-pile wall.
7 Difficulty of pile pulling
The top cause of difficulty in pile pulling during removal of temporary steel sheet pile structures is interlock corrosion and deformation and the insertion of steel sheet pile into hard soil etc. To ensure the successful pile pulling, it is necessary to keep steel sheet pile and interlock smooth, straight and unhindered and to apply butter inside interlock during pile driving. If built pile is used during piling, the number and position of built pile shall be recorded; welding between pile bodies shall also be recorded for reference at pile pulling. When removing the first pile of wall body, be sure to turn aside the inter-connected pile bodies. Once the first pile is pulled out, the subsequent pile pulling would be smooth since the interlock resistance at one side disappears. Estimate pullout force of pile according to geological data collected before pile pulling and the degree of difficulty of piling and select corresponding pile pulling machine (vibratory hammer) and auxiliary equipment. The first pile is normally difficult to pull out. Knock the pile with hammer to make the interlock connection loose; you can also insert a steel tube at both sides of sheet pile and then inject water and air to destroy the side pressure of soil mass on pile to be pulled. Pile body can be pulled out in most cases after above-noted measures are taken.