Points and Notices in Sheet Pile Construction Process

Use sheet pile construction process as clues, now let’s talk about some points and notices during construction.

1. Sheet Pile Sorting and Preparation

1) After sheet pile transported to the site, check its size, shape, locking. Whereever bending, deformation and locking incompatibility needs to be renovated. By circumstances use ways of cold form, heat knock (the temperature does not exceed 800 ℃ ~ 1000 ℃), welding, riveting up, removed, or take long.

2) According to bearing platform, cofferdam plane use rectangular layout, use special angle pile at the corner.

3) Before Inserting pile, clean debris inside the mouth of locking, and coat with butter, clay, sawdust and other dry mixture to reduce the inserting resistance and enhanced ability of seepage proof.

2. Production and Installation of Guide Device

In sheet pile Insertion process, to ensure the vertical and plane location of sheet pile, set oriented guide frame made by 80cm steel sheet pile and 25 “I-beam. If just need one pile hit for the design depth and sheet piling is only exposed water at 1.0m or so, use single-layer and double-sided guide frame with spacing 8-10cm more than thickness of sheet pile. In order to guarantee the verticality, in insertion,use total station and hanging plumb bob method to control its verticality.

3. Sheet Pile Insertion and Closing

Sheet pile insertion method is : block by block (group) and then insert to the design depth, then close.
Insertion order is : Start from navigable surface to the upstream side, then plug front shore surface, and finally pile in the downstream face for closure.

Specific Inserting and Piling Ways :

(1) Transport cleaned sheet pile to construction site.

(2) lift the first sheet pile in place, firstly make use of its own weight to sink into earth, then play with DZ60 Vibratory Pile hammer to hit it to the designed position. The first pile must strictly be controlled in its verticality. After piling one or several fix them with the guide frame firmly.

(3) Lift sheet pile and with the worker’s help, put it into the last piled one’s locking mouth, sink to earth under its own weight, and then pull the vibratory hammer to fight on the pile.

(4) As the locking friction, previously inserted steel sheet pile would sink along together and inserting difficulty, hand-pulled down or block and tackle hoist can be used to forcely pull and twist.

(5) Must strictly control the verticality in piling to reduce the closure error. When comes to the last side, review the side length, in theory, side length should be an integer multiple of the width of sheet pile. When a deviation can not be adjusted by pultrusion method, and remove to re-play in the prevention and correction is invalid, special wedge-shaped pile units could be used for circle closure.

4. Pumping and Installation of Purlins

Numbers or layers of purlin in sheet pile wall should depend on the water depth, inside and outside soil lateral pressure and other conditions, and these conditions can be used to test the support strength of sheet piling and purlins. Purlin use double 45 “and 63″ beam, the first layer of purlin should set as the water level, then pump water and set other purlins in order.

Here is the process:

(1) Pumping to the designed elevation of each purlins;

(2) Lifting purlin in place and weld it to the steel sheet pile;

(3) Install horizontal support members (short side);

(4) Add inclined bracing at the purlin and level support.

In purlin setting, should consider the location of cap and pier, and since the driven sheet pile components can not be same straight as purlin, so in gaps add additional wedge shape wood to tightly squeeze or use 3cm steel sheet pile to make T-shape and weld with purlin closely .

During pumping,sheet pile locking mouth inevitably leaks, at leak location in the outer sheet pile, toss cinder mixture of sawdust or bran and others to block the locking as water flow. As the third purlin set 1.6m under the riverbed, so after the second purlin set, continue pumping to clear base, when clear to the third purlin’s elevation set the third purlin, and then clean the base to the elevation of concrete back cover.

5. Base Clear

Bearting platform of main pier embedded under the riverbed, so must clean the riverbed soil to the designed location of back cover. According to the soil conditions at the riverbed, to reduce the disturbance casued by construction machinery against soil in clearance process, use artificial small excavator to clear base.

In the clearing process, arrange dedicated staff on duty, pay close attention to the sheet pile deformation and water level difference inside and outside for timely processing.

In the base clearing should do the following:

(1) Soil from clearing is prohibited to stack around sheet piles, should ship outward so as not to increase the dam’s outside pressure.

(2) After clearing the base, substrate flatness inside should be controlled at ± 10cm or so.

(3) Do not disturb the soil edge of sheet pile to avoid foundry.

(4) Equip four pumps for drainage, arrange staff by 24h rotation for inspection. When found sheet pile distortion or leakage and other serious irregularities, report to the manager department immediately and take timely measures.

6. Concrete Back Cover Casting

The sealing casting use car perfusion pump to pour directly, the back cover concrete thickness is 50 ~ 80cm, concrete slump requirements are in 18 ~ 22cm, before pouring get ready the pumping equipment.

This article comes from Sheet Pile's Blog edit released