How to Drive Steel Sheet Pile?

There are three typical sheet pile driving methods.

1. Single Pile Driving Method

From one of corners of sheet pile walls, drive the pile one by one until the end of the project. This method is convenient, fast and does not require auxiliary support, but pile easily incline during driving, and the error accumulation is not easy to correct.

2. Screen-Piling Method

Put 10~20 sheet piles in rows into the leading guide or frame to shape it like a screen wall, then pile driver play back and forth, first drive both ends to the required depth, then pile the middle sheet pile sequentially. This method prevents the sheet pile’s larger inclination by reducing the tilt error accumulation, and easy to close up after construction. But its drawback is that construction process is a bit slow, and need the erection of a higher pile frame.

3. Piling by Waling Piece Method

At a certain height on the ground some distance from the axis, firstly build single or double layers of circle waling pieces as bracing system, then insert sheet piling one by one inside. When four corners are closed up, gradually drive sheet piles block by block in steps’ way to the designed elevation. This approach ensures flat size of sheet pile wall, squareness and flatness, it is suitable for occasions requiring higher precision, fewer pile amounts. The disadvantage is the complexity and slowness in construction, and it requires shaped sheet pile in wall closure.

( Excerpted From Three Typical Sheet Pile Driving Methods  )

Sheet Pile Pit-Retaining Structure Design

Design of  sheet pile retaining structure in foundation pit can be divided into the following three categories:

1. Cantilever Support Structure – when the excavation is not very deep, the cantilever support structure can be used to block soils behind the wall.

2. Single Support Structure – when the excavation depth is larger, to ensure the retaining structure safety and reduce distortion, often set a support or an anchor near the top of the supporting structure.

3. Multi-support Structure – when the excavation depth is large, we can set multi-layers of support or anchors.

Design Contents of Steel Sheet Pile Retaining Structure

1. Select the sheet pile type and model cross-section;

2. Calculate and check sheet pile insertion depth, cross-section strength and deformation;

3. Consider the corresponding precipitation plan and its impact on the surrounding environment (including the vibration impact in pile recycling or removing)

(Excerpted From Steel Sheet Pile Pit-Retaining Structure Design Classification )

Calculation Points on Sheet Pile Wall Structure in Soft Soil Water

1. Three Types of Calculation

A. The whole sheet pile wall structure must meet construction requirements in strength and stablity. In calculation, we should consider the worst construction condition and flowing water pressure from above riverbed to river surface, water foce when ships passing by and in tide situation. Pressure from below the riverbed to sheet pile end is combined by hydrostatic pressur and positive earth pressure.

B.  Because of three layers steel waling system, the whole weight is on the sheet pile, we must calculate the vertical load of sheet pile wall.

C. Because of soft soil with deep excavation, the base of sheet pile wall must do stability calculation mainly including Pile Sand Welling and  Base Bumping Calculation.

2.   Establish Calculation Model

 

Use Infinite softwarelike Midas Civil, sheet pile is modeled or simulated by pile units, support and waling system is simulated by beam units.

3、Notes on Base Stability Calculation

 

3. 1　Pile Sand Welling in Base End Calculation

In the pumping of base end, it easily brings danger of pipe sand welling, we should calculate in simplized way. The rule of calculation is by the enough sheet pile embeded depth t to increase water flow length and reduce upward water force. The frequently used calculation formula for non-sandwelling is : K·i·γ≤γ

In this formula：

K-Safe Coeffcient (less than 2 is required) ;
I—hydraulic gradient;
i = h′/(h1+ t) ;
γ—Water Weight ;
γb —Soil Effective Weight

3.2  Base Bumping Calculation

After deep excavation in soft soil foundation pit, under the water pressure and unbalanced soil pressure inside and outside, there may be bumping situation at the end of soft base,  we can claculation by slip surface way, the frequently used fomula is :

Slip Moment：Md=γMH（x2/2）
Stable Moment：Mr=x∫π/2+α0 SM(xdθ), α＜π/2

In this formula：
α=atg(b/h);
h – the height of bottom inside support against to concrete casting height
b – Haft length of base end;
SM -shear strength without watering in slip surface

Note: the article is from  Calculation Points on Sheet Pile Wall Structure in Soft Soil Water

Patent Introduction: Method for securing sheet piles

Patent 6664509 Issued on December 16, 2003
Estimated Expiration Date:  September 27, 2022

Abstract

A method for securing sheet pile includes interlocking the two sheet piles by utilizing sheet pile interlocks having an axial groove formed between the sheet pile interlocks. The method further includes introducing a welding electrode into the axial groove and welding the interlocked sheet pile interlocks together.

Sheet Pile Support Construction Points

For construction projects that need sheet pile as support, here are nine main construction points to smooth the whole construction:

1. Inspect and correct sheet piles, including test its length, width and thickness, in addition to visual inspection, other deficiencies must be corrected too.

2. In sheet pile insertion and play,  put line by measurement and try to pile vertically. The pile position deviation should be less than 50mm, the vertical degree of deviation less than 1%. Should start by the river, and finally be closed far from the river, so as to prevent the small toe mouth of sheet pile leaks by the river side.

3. At the lockings of two sheet piles, put on some butter to facilitate the play and pull, while prevent water seepage.

4. In sheet pile cofferdam, excavation needs a long time, there is large soil lateral pressure. In order to ensure sheet pile stability, according to the design , excavation depth should be 50cm lower than that in each purlin support. Timely add purlin bracing for support. Until the reinforcement completed at this layer, start excavation for stability.

5. Make sure level status for inside support to prevent accident from local deformation by the force discontinuity.

6. Inside the cofferdam, components within the support must be welded solid. Non-dense places between sheet piling and purlin need to work closely with the steel packing to avoid local buckling.

7. When excavate to the end of pile cushion, should immediately pour concrete manor to prevent boiling occurs in substrate by the constant term of water soaking, which would affect the overall pit stability.

8. At the four sides of base should set drains, water wells to ensure the water can flow out of the pit timely.

9. Do not remove sheet pile untill main structure construction  and soil’s backfilling completed. But also consider the impact of pile-removing at the surrounding environment, timely adjust the removal rate. Cavity after pile removal should be timely compacted by yellow sands to prevent the surrounding soil subsidence.

Note : the article is excerpted from Sheet Pile Support Construction Points

Sheet Pile Construction Monitoring Methods

Sheet Pile Displacement Monitoring

1) Vertical position monitoring
Surveying use Trimble DINI12 Digital Precision  Levels and WILD NA2 + GPM3 precision optical levels. The vertical deformation point error is more than + 0.5 mm in control. To ensure the monitoring accuracy, according to the specifications in the dock construction impacts outside the security and stability, in the good visual area, they set the two elevation reference points and three point field levels, composed of vertical displacement of the control network,taking1 to 2 months once Regular individual test to  test its stability and ensure the quality of test facilities. The elevation of each monitoring point is composed of a close working standard line level loop, the vertical displacement of the monitoring points is calculated by the twice measured height difference of the monitoring points. The amount of vertical displacement is calculated to mm.

2) Horizontal displacement monitoring 
They use LeicaTC402 Total Station and the United States Ashtech Z-survey dual-frequency GPS receiver. Benchmark test for the monitoring network together once a month. Monitoring point observation use the measured edge intersection, the intersection angle controls between 60 ° ~ 120 °. Monitoring point’s prism used to force the final heart devices to boost the accuracy. Deformation point relative to the operating point of the position error control ≤ ± 2.0 mm.

The horizontal displacement of monitoring points is calculated by the difference between two measured data. The amount of horizontal displacement is to mm.

Sheet Pile Deformation (inclinometer) Monitoring
Steel sheet pile and the soil type inclinometer and domestic use U.S. Geokon603 CN-1-type inclinometer, bottom-up by 1.0 m equidistant measurement, automatic storage records, forward-backward two readings of 180 ° observed.  To ensure the accuracy of observation, each measurement, the test sensor isto be placed in the bottom of the hole to 10 ~ 15 min, to ensure that the temperature balance. Monitoring the value of precision is ± 0.1 mm.

Stresses and Pressure Monitoring
The test of stresses, earth pressure, pore water pressure use the domestic XP05-type vibrating wire frequency (temperature) readout and XP99-type vibrating wire multi-frequency instrument, taking the readings and automatic direct-reading.Thereading accuracy  is ± 0.5Hz, ± 0.5 ℃.. Monitoring accuracy: steel sheet pile stress is ± 0.01 Mpa and earth pressure is± 1 Kpa and pore water pressure value is± 1 Kpa.

Groundwater Monitoring
The underground water level observation use SWJ-8090 type selection of domestic electricity type ruler over the two DaXun and typhoon period. Practice has proved that the water level gauge to monitor selected to take direct readings, the smallest ruler depicts 1 mm. Monitoring methods is appropriate and monitoring points layout is reasonable and the value of the sensor accuracy is ± 2 mm. Scale design and observational accuracy are to meet the requirements of the project, playing a guiding role in the construction.

Underwater Slope Stability Monitoring
Underwater slope stability monitoring uses U.S. AshtechZ-survey, based on the monitoring of large-span steel sheet pile cofferdam works double frequency GPS receivers with choke-type antenna with domestic HY1700 bathymetric features, increasing the lateral earth pressure of steel sheet pile, inside and outside the row of steel sheet pile deformation detection instrument on board operations, automatic continuous record storage measuring with the stress changes of the standards supporting  process  and pore-water pressure outside the cofferdam and the steel rod depth rod method. The former measurement accuracy≤±the stress and guide beam stress. Monitoring, testing is very comprehensive The latter accuracy ≤ ± 5 cm, similar to hydraulic engineering at home and abroad is rare.

How to Do Sheet Pile Finite Element Analysis

In sheet pile construction, by Finite Element Method, we should establish analysis model first.Then calculate and analyze sheet pile security and stability.

The external force is mainly hydrostatic pressure and water pressure, by the force expectations and calculations the combined load in each condition can be drawn. Using ANSYS Finite Element software to build a solid model, define the real constants and material properties, take four-node shell element Shell Elastic 4Node63 to divide unit for the model, respectively calculate the deflection, stress, bending moment in the model under these N kinds of loading conditions.

Combining loading conditions, calculate by finite element to get force map, and then by the post-processing data to get the maximum stress on sheet pile. Taking into account stress reduction factor 0.7 for the old or used sheet pile, the stress’s expansion factor 1.3 for the temporary structure and the sheet pile materials, calculate sheet pile actual allowable stress.

Similarly, from the analysis obtain the sheet pile deflection diagram in the X and Y direction, from the map we can intuitively know the location of maximum deflection under the wost condition. Compare the distance with the actual allowable sheet pile deflection.

If the maximum stress obtained through finite element analysis is less than the actual allowable stress, the maximum deflection less than the actual alloable deflection, it indicates that the strength and stiffness of the selected sheet pile in this condition meet the design requirements.

In the same way, we can also calculate maps of the displacement, deflection, bending moment and the axis of purlin and inside-support, compare the maximum value with the actual allowable one, to determine if the strength,stiffiness and stability of purlin and inside-support meet the design requirements.

How to Select Piling Vibratory Hammer?

To form sheet pile retaining wall, we need vibratory hammer to drive piles into the soil. Then how to select the hammer?

Vibratory hammer selection should meet three basic conditions :

1) Excitation force of vibratory hammer P0 should be equal to or greater than the sinking components being vibrated and soil’s dynamic lateral friction Tv ;

2) The total weight of vibratory hammer system Q0 should be greater than the driven components’ dynamic tip resistance Rv ;

3) Work rate of vibratory hammer system A0 should be greater than the minimum required amplitude A0 when driven components go through soil layers.

Note: For more information, please read Vibratory Hammer in Sheet Pile Driving

Sheet Pile Wall Design

Generally in sheet pile wall design, normally we need to calculate all kinds of loads, scour depth, length of sheet pile (including pile embeded depth, the concrete cover thickness) through test algorithm. According to different construction conditions in process aselect sheet pile sections, supporting layers and structure, at last check the overall stability of sheet pile wall.

1. Data Collection
Collect and analyze geological maps, the highest water level, the highest level of construction and so on.

2. Determine Geometry Size
Plane size is often dermined by upper structure and its foundation size. Sheet pile wall construction should be in accordance with the whole project construction and template installation, so the wall’s size should be at least 1.5m greater than the basic outline. It must also consider the needed size of pumping equipment and wells’ installation.

Dimensional size is usually influenced by water level, scour depth, the depth of excavation inside wall and factors such as stability in the pit end. But the most direct impact is water level.

3. Calculate Sheet Pile Wall Lateral Pressure

Assume sheet pile’s embedment depth first, then calculat lateral pressures hydrostatic pressure, water impact, ice pressure, wind, wave power and earth pressure.

4. Force Checking by Constructin Conditions

5. Stability Checking
Need to analyze wall’s overall stability and soil stability at the end of the foundation such as arch, water well-out and sand-cast.

Article Source:   Sheet Pile Wall Design Steps

Sheet Pile Driving Frequently Problems

Hard to insert Sheet Pile by large resistance force

There are two main reasons : solid and gravel sand layer; corrosion and deformation of connected sheet pile lockings. For the former case, in the pile tip's forwarding direction, cut the side angle to the slope of 1:2 to 1:4, and pile by high-pressure water flush or vibration method instead of hard hit with a hammer only; for the latter one, remove rust, grease and correct lockings to reduce resistance.

Pile tilting in driving direction

When pile larsen sheet pile, the connection resistance is relatively large. And the unbalanced given forces at both sides of cross section make piles easily to incline. To prevent such a tilt, in the piling direction set clip plates at the interlockings of steel sheet pile. At the same time, pre-calculate the position of every plates on purlin for calibration at any time. If the tilt is inevitable, the correction method is to use wire rope and hoist to reversely pull the sheet pile and then hammer, or use a special wedge-shaped sheet pile to correct.

Sinking of both sheet pile and neighborhood inserted piles

The reason is caused by the increasing resistance force of steel sheet pile bending notch. The treatment measure is promptly correct the tilting piles, use angle steel to fix the problem piles temporarily by welding with inserted pile(s).

Using of Corner Pile

For the need of pit structure, often we need corner pile, a special shaped pile to change the piling axis direction. Corner pile is normally made by larsen sheet pile cut along the midline, then combine and weld by actual needs.

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Article Source:

Sheet Pile China Manufacturer, Supplier - Shunli Sheet Piling Industrial Co., Ltd.

Instructions on Sheet Pile Construction

Instructions on Sheet Pile Driving

In construction, to reduce the water impact against steel sheet piles, first should drive piles starting from the upstream and inside of river, then pile the river downstream and outside. In piling, use construction techniques combined with press and drive way.

When need to prolong steel sheet piles by welding, must use same type, same strength. In welding, firstly butt welding or seam-weld interlockings, then weld sheet piles. Joints of the adjacent steel sheet piles must be dislocated more than 6m and shall not exceed 50% in the same plane.

Instructions on Purlin and Support Installation

Cofferdam is the sheet pile walls that form into a circle. For safe and stable sheet pile project , usually it requires steel purlin and inside steel support. Producing and processing of purlin and inside support should be combined by the situation in plant and construction site. And should be uniform and in accordance with universal standard. When items or parts made by factory transported to the construction scene, must be assembled as a whole at the site in order to ensure accurate structure and size.

Processing of steel purlin parts must be finalized to complete on the model pedestal .

Basic methods to install purlin is to use steel casing with concrete piles to support pole beams, use pole beams, jacks and mandrel hanger system to layered lift and decentralize purlin and finally fix it to the casing.

Permeability Proof and Anti-Leakage Treatments

A. In all processes of steel sheet pile driving, must use guide and oriented device, strictly control the vertical degree at both sides to make interlockings connected very closely between piles. Because assurance of sheet pile’s vertical degree and be close around the purlin are the key points to avoid permeability and leakage.

B. In pit’s pumping, for leakage from loose interlockings, use cotton with rich fiber to plug and block.

C. For wide slit between piles, use flax roots mixed with butter to stuff and seal the seam to aovid permeability and leakage, or use fly ash, saw wood foam and expansive cement to scatter along the pile surface in the flow direction outside the cofferdam.

Technology Notes on Smooth Sheet Pile Construction

In sheet pile project, usually we need to set guide device, pump water, install support and weld piles. In order to ensure smooth construction process, there are some important notices.

Notes on Sheet Pile Welding

Elevation of supports’ faces must be consistent, each node should be welded by the node map, strengthen the connection, welding rods shall meet the construction specifications.

Steel support, spliced by welding, must use way of tear welding by regulations, like should fully weld the seam, at welding seam surface, welding wave is required uniform, not allow any pores, slag, cracks, sarcoma and so on. The quality of welding and inspection system should be strictly enforced.

Setting Guide or Oriented Device

Use two section steels as oriented control clamp, place and fix it in position. In case of shock must re-adjust to fix. In the driving of steel sheet pile, generally we need to send pile to the required elevation first, at this time, should remove the fixture first then gradually lift pile.

Setting oriented devices is to ensure the right sheet pile axis after construction, oriented pile or guide beam could be replaced by profile steel or wood, the spacing between the beams is just the width of sheet pile walls. In order to maintain accurate distance, between the beams, we can embed a temporary skids at certain intervals. After use, oriented devices can be removed for next section’s use.

Notes on Pumping

In steel sheet pile cofferdam, not pump until strength of concrete back cover is more than 90%. When the water level pumped inside the cofferdam is 0.5m below the steel support, stop pumping until support’s installation is completed. When pumping, pay  attention to the force status between steel sheet pile and support.

Notes on Support Installation

Welded purlin as a whole should be at the same line from upper to lower part in order to enhance the overall stability of the support system. Before steel support’s installation,  pull through the twine first and mark the midline on the purlin.

Steel support and steel sheet piles should against each other very tightly, between each bars connections should be pretty solid, in the construction process of bearing platform, should always check force conditions between pile and support.

Article Source : sheet pile manufacturer, supplier - shunli sheet piling industrial co.,Ltd

Why Need Guide Device in Sheet Pile Wall Construction

Setting guide or oriented devices is to ensure the right sheet pile axis after construction, oriented pile or guide beam could be replaced by profile steel or wood, the spacing between the beams is just the width of sheet pile walls. In order to maintain accurate distance, between the beams, we can embed a temporary skids at certain intervals. After use, guide or oriented devices can be removed for next section’s use.

How to set ?

Use two section steels as oriented control clamp, place and fix it in position. In case of shock must re-adjust to fix it. In the driving of steel sheet pile, generally we need to send pile to the required elevation first, at this time, should remove the fixture first then gradually lift the pile.

How to Check Sheet Pile Deformation

Use inclinometer to measure sheet pile. 

Take steel sheet pile for example, firstly weld a φ75mm steel pipe in the groove of steel sheet pile and pile the pipe together with steel sheet pile. Insert inclinometer to the tube fixed with sand filled in. 

Although inclinometer can measure the horizontal displacement, it means little to distinguish safety of steel sheet pile, because the cofferdam allow a great amount of displacement (up to 100 ~ 300 mm). 

What means alot here is the sheet pile bending measurement, which could be obtained by numerical differentiation of curvature from inclinometer data. This is the reliable results to determine whether the steel sheet pile meet deformation requirements. It can also be used to compare with the moment from calculation results to indirectly get stiffness information of sheet pile wall.

How to Check Sheet Pile Before Construction

Firstly,  after the arrival of sheet piles, check whether the model is consistent as design, if not, re-calculate the strength and support of sheet pile.

Secondly, when go into the construction site, all sheet piles are required for inspection first, only a complete and straight sheet pile can be brought into the scene. For used-piles (like steel sheet pile), particularly should emphasis on inspection.  Because used sheet piles in Pile, transportation and stacking process are easily deformed by external factors. If do not check, some may not easy to pile or drive.

Inspection method

Use a little flat car with a 1.5 ~ 2.0m long standard sheet pile put on, check sheet piles going along with the standard pile from start to finish. Once a defect is discovered adjust it asap.

After this checking, when in the transport and stacking, make sure not bend them, avoid the collision, in particular, do not break the continuous lockings. Stack space should be flat and solid not producing a large settlement. At the bottom of sheet pile stack, should pad wood blocks. Piles with different sections should be separated in different stacks, between each stacks should set aside certain channels to facilitate the moving for crane or transport vehicle.

Sheet Pile Design in One of Beijing-Shanghai High-Speed Railway Projects

Based on the hydrological and geological conditions around the main bridge of Jinan Yellow River Bridge of Beijing-Shanghai High-Speed Railway Project in China, for sheet pile cofferdam design and construction, we introduced the thinking of design, comparison of two sheet pile design proposals and reasons for selection.

Project Description

The length of Jinan Yellow River Bridge, one of sections of Beijing-Shanghai High-Speed Railway project,  is 5.143km. The main bridge is 112+3*168+112m supported by continuous steel with same height. A  stiffened arch was set in the middle, height of truss is 16m and width 30m, distance between sections is 14.0m. The main piers are No. 0 ~ 5, in which No.1,2,3 and 4 Pier all use 28 pieces of Φ2.5m bored piles, the bearing platform is 6.0m in thickness and 42.5m*23.3m in plane size. While No.0 and 5 Pier use 21 pieces of Φ2.0m bored piles, bearing platform is 4.5m in thickness and size 34.6m*13.8m. Concrete of bearing platform is C45 type.

Bearing platforms of No.1 and 2 pier of main bridge are in the main river cap (year-round water), others are in the south shallow beach area. Elevation of top surface of pier No.0 pier is +33 m (ground elevation is +33.50 m), No.1 pier +27 m, No.2 Pier +27 m, No.3 +27 m (ground elevation +30.14 m), No.4 +27 m (ground elevation +29.91 m), No.5 +30 m (ground elevation +30.92 m).

Thinking of Design

 

According to detailed information on geological exploration, No.3,4 and 5 Pier Yellow River main bridge is located in the floodplain south of Yellow River, silt and silt layers are rich in water within 19m below the ground surface, and there is a a hard plastic-like clay layer 2m below (elevation is about +9 ~ + 11 m) with relative complete and uniform distribution. The main bridge’s No. 1 and 2 pier is located in main channel of Yellow River, the riverbed’s elevation is + 17 ~ 24 m, the surface is covered by loose silt,  between +9 ~ +11 m there is a 2m thick layer of hard plastic-like clay. And this layer is confirmed in the piling or driving construction of steel casing and bored pile, the soil samples removed are sticky and large hard plastic-like clay block. So based on detailed construction surveys, the bearing platform of main Bridge’s No.1,2,3 and 4 Pier will use steel sheet pile cofferdam program. For No.0 and 5 pier, because of shallow excavation depth, method of open-excavation and protection in porcess will be used.

 

Comparison and Selection

 

Option One : Long Steel Sheet Pile Program

The flat surface of steel sheet pile cofferdam is rectangular for the base of the main bridge, the inner mouth size is 46.5m*28.3m, steel sheet pile is 24m each.

Mouth elevation at the end of steel sheet pile cofferdam for No.1 and 2 pier in water is 7.0m, top elevation 31m (top elevation of bearing platform add 27 m, flood elevation is +30.5 m), Mouth elevation at the end of steel sheet pile cofferdam for No.3 and 4 pier at beach is +6.5 m, the top surface elevation +30.5 m.

Use German Larsen IV (or shunli cold formed type) steel sheet pile . The cofferdam is made by single layer steel sheet pile, 3 layers of steel tubes and inside steel support formed by beams. Inside ring-support (purlin) for steel sheet piles use I56 compsite structure and internal support use 630mm steel pipe.

For sheet pile wall construction on land, pile by hydraulic vibratory hammer with the help of 50t crawler crane; for sheet pile wall construction in water, use 40t gantry crawler crane for water platform and hydraulic vibratory hammer.

For excavation and soil clear inside cofferdam on land,  use long arm excavation machine and high-pressure water jetting for soil suction method; for the ones in water, use method of high-pressure water jetting for dredging. Considering  the end of steel sheet pile will be piled or drove into the hard plastic-like clay layer between +9 ~ +11 m deep, after soil clear or dredging, sheet pile wall or cofferdam could not do bottom sealing, instead directly drain the water inside the cofferdam, and then pour 20 cm thick concrete pads, then remove steel casing, chisel trailer coupling and start construction of bearing platform.

Advantages : No bottom sealing reduces the risk of concrete construction in large area and construction investment, reduces the dredging depth of the cofferdam and saves lot of sealing concrete. At the same time, within the cofferdam, excavation, dredging, construction of concrete pads are all in dry place, improves the efficiency and speed up the construction schedule.

Disadvantages : Length of steel sheet pile added 6m increases the cost in itself.

Option two : Short Sheet Pile Program

Use 18m long steel sheet pile, the others are same as Option One. Considering the steel sheet pile cofferdam is in relative loose silt layer, bottom sealing in water will be carried out after soil clear within cofferdam, then until strength of the sealing concrete meet requirements drain the water, and then remove the steel casing, chisel pile head, and start construction of bearing platfrom.

Advantages : Length of steel sheet pile reduced 6 m will lower investment in itself.

Disadvantages : Because of bottom concrete sealing in water, it increases the construction difficulty of excavation in water and dredging within the cofferdam, reduces construction efficiency. And bottom concrete sealing construction in large area and generous amount would bring high risk and difficulty, a lot of extra sealing concrete also increases the uncertainty and costs on construction.

 

Program Selection

 

Through repeated investigations on site and programs’ comparison, option one is determined to use. From the construction technology, safety and reliability considerations, if by option one,  though water can not be drained inside the cofferdam, can also continue with Option two, there is not much risk. Also from an economic point of view, construction cost of the option one is much lower than Option two, the successful implementation would mean significant cost savings.

Sheet Pile Cofferdam Design with 6 Layers of Inside Support

Construction process of sheet pile cofferdam with six-layer inside support is generally divided into six steps of pumping and excavation down and five steps of concrete pouring and support demolition. The most dangerous condition is excavation to the end. For design, key points are as follows:

1. First set the guide frame of sheet pile, insert and play, then install the first layer purlin and support (to avoid high tide). Then try pumping water and plug pile joints in water over the riverbed. 

 
2. From layer 2 to 6, pump or excavate one by one to the position 0.5m lower than the elevation of support to be installed, then install purlin and support.

 
3. From the 5th layer, gradually narrow the excavation surface layer to form slope. 

 
4. Excavate by divided area to the end of cushion, pouring concrete pads, and ultimately form a complete flat construction surface. 

 
5. Pouring cap by four-layer, backfill sands from nearby and remove a support layer as soon as each layer’s pouring completed. 

 
6. For the last 2 layers’ support, should consider the construction situation for support removal or change when pouring the upper parts of bridge piers.

In addition, in the calculation and design, select datas of drilling holes in the place with poor geological conditions. Then refer to section diagram, analyze and calculate the displacement and bending moment of sheet pile in the six steps’ pumping and excavation.

Sheet Pile Wall Structure Designs on Seriously Weathered Rock Layer

For sheet pile wall or cofferdam construction, normally we need to drive piles to the required depth. But for shallow layer especially seriously weathered rock layer, it is very difficult to drive piles. For instance, top surface of highly weathered rock and sand layer is 1-4m lower than cushion base, and some part is even near the cushion base. Because the driving depth is not enough as required, the displacement at the pile-end will be larger, sheet piles in some project sections would easily get damaged like "kicking damage".

For this problem, we must take some measures on structural design first.

For structral desgin of sheet pile wall, there are mainly three plans to solve the problem :

1. Enlarge the wall or cofferdam and put slope inside;

2. Increase inside support layers;

3. Reinforce the bottom of sheet piles;

Sheet Pile Wall or Cofferdam

Comparing three plans above, if only by plan 1, because the wall or cofferdam is normally large enough, it will cost extra money or time. And if there are more wall or cofferdams in construction at the same time, it will influence other projects too; Just by plan 2, if we increase inside support layers when excavation near the end, supports' changing process will be more complicated when it comes to the back concrete cover; If just by plan 3, although it is applicable in theory, it is not enough for pratical construction.

The best way actually is to combine the strong points of the three plans. For instance, firstly, we can set the axis line of sheet pile wall near the cap side which will proive a certain slope space and is useful for sheet pile reinforcement.Secondly, set 6 layers of inside support,make the space wider at the upper 4 layers. At last, at the location higher than layer elevation of 7.0m, set steel tubular pile (or called steel pipe pile) as support foot right near the driving-hole of sheet piles.

Sheet Pile Repair and Reinforcement

At present in the world methods of sheet pile repair and reinforcement mainly include two categories : Local Repair and Reinforcement Method and Set Alternative Retaining Structure Method.

Local Repair and Reinforcement Method includes : Steel Repair and Weld Method, local Outside Cover Reinforcing Method, Lower Beam Cover Elevation Method and Improve Soil Properties behind the Wall Method;

For Method of Setting the Alternative Retaining Structure includes : Add Underground Continuous Wall Method and Add Alternative Steel Sheet Pile Method.

Which Method to Use

Due to technical conditions, the actual project cases of steel sheet pile structure repair and reinforcement are very few.  For research, we suggest use ANSYS software to build simulation models for structure reinforced, compare deformation, internal force and stress produced by all reinforcement methods to discuss and analyse the technical feasibility and reliability of these repair and reinforcement methods.

Why Need Sheet Pile Reinforcement and Repair

With strong capacity, watertight and simple to use and good durability etc., sheet pile of steel become the mainstream materials in modern construction industry.In the harbor or port's shore structure which used to connects wharf structure and slope as sheet pile retaining,steel sheet pile itself is vulnerable to erosion and damage. So we need to repair and reinforce sheet piles.

Rockfill Cofferdam and Steel Sheet Pile Cofferdam

Rockfill Cofferdam, that is, use local available building materials as the main filling material;

It is a traditional earth-rock cofferdam. The local earth and rock materials can be used, taking into account the main pumping station was built after the project finished as a permanent sea wall, so that it could be a part of eastern  north berm project.

But if we use solutions of ordinary rockfill cofferdam and rockfill cofferdam in the heart of sheet piling wall , there does not have enough space in such a narrow range of grading. 

Secondly, cofferdam construction required fast speed in building, but in these types of programs, large amount of rock and serious slippery preloading can not be too high too fast. 

Thirdly, as pit depth is down to -20.8m, according to requirements from excavation design unit , the seepage control depth of cofferdam is better to deep clay layer to -13m,  slope can not be stabilized within the ordinary rockfill cofferdam and excavation can not meet requirements. 

Furthermore, outside the cofferdam, the water is deeper so that velocity and wave is more serious and erosion is more severe, so outside of the slope, it is not stable either. Especially if cofferdam foundation is not treated on soft ground, combining with the ebb and flow, it easily results in land shifts, slides and collapse. Then we have to fill and repair frequently because of poor security.

Steel Sheet Pile Cofferdam, that is,use cold-formed steel sheet pile wall to form a cofferdam, and then fill the clay.

Use cold-formed steel sheet pile wall to form a cofferdam. When leaving an appropriate distance from the excavation lines of pumping station, dig out the original loading layer of riprap and drive two rows of cold-formed steel sheet pile . 

The program has advantages of high strength in material, arbitrary length, lower price, light weight per unit, fast construction speed, short project cycle, good security and stability and effectively guard against moisture,waves and seepage.

Steel Sheet Pile Cofferdam by Deep Truss Method

Construction Process of Deep Truss in Steel Sheet Pile Cofferdam

Picking Steel Sheet Pile→Driving Pile Lead → Construction of Inside Support and Purlin → Sheet Piling Insert and Hit→Excavate the Excessed Stuff Inside → Pouring Back Cover Concrete → Pumping Inside Cofferdam → Cutting Steel Casing → Pile Head Chisel → Steel Rod Tie → Pouring Concrete on the Flat → Pier Construction → →Removal of Steel Sheet Pile

Notice : during the process, we should always prevent leakage, plugging and deformation.

Advantages of Deep Truss Method in Steel Sheet Pile Cofferdam

Deep truss method can be safely applied to large-scale steel sheet pile cofferdam in deep water and bad geological condition. It is able to overcome difficulties by the traditional steel sheet pile cofferdam construction technology when in the pumping mode and large spacing between the soil stays and cofferdam inside support, like steel sheet pile can not afford to the external water pressure in pumping mode. Deep truss method has a wide range of applications. In this article, we elaborates on the new truss method and its calculations in steel sheet pile cofferdam construction and construction process. We can also accumulate more new technical information on the application of steel sheet pile cofferdam.

Project Overview

Changsha Harbor Bridge is located in the south of Huizhou-Chaozhou section of Xiamen-Shenzhen Railway in China. The main bridge 55 # -88 # pier is in the water, 63 # -67 # pier is at the deepest level and has worst geological condition. The flat caps there is at the maximum size of 8.2 * 12.5m, a thickness of 2.5m. The end caps from the deepest water is calculated 9.0m; The water level of the Bridge construction is +1.528 m, consider the water level as +3.0m in calculation.

Using the German Larsen IV locking type steel sheet pile, to improve the state of force when steel sheet piles in deep water , use Deep Truss Method for steel sheet pile cofferdam construction：

Firstly make the inside support of steel sheet pile cofferdam as truss system, use decentralization device on steel casing to place it to designed elevation, and then use truss support system as the frame guide to play and insert play steel sheet pile.

This method can be applied to large-scale cofferdam in deep water and with bad geological conditions, and it is very safe. The cofferdam is using the structure of purlin and internal support. (see Figure ), for the purlin, use beam 2145b, internal support use Φ300mm (thickness δ 6mm) steel, diagonal steel connection use channel 18 . Between layers of circuit purlin use beam 2136b.

Pic Note: Three-dimensional and floor plans of steel sheet pile cofferdam

Core Calculation Parameters of Steel Sheet Pile Cofferdam

Steel Sheet Pile Embedment Depth Calculation

 

External Forces of Steel sheet pile mainly are active ground-breaking pressure, passive earth pressure, water pressure and wave pressure.

When calculating the core parameters are :

M: external torque on the base surface
Ea: Pressure on the center line of cofferdam
B = 8.0m, inside friction angle = 20 °
Calculated, Shear K = 0.74> 0.7

Anti-Overtuning and Stability Calculation

 

Core parameters:
G: weir body weight per meter
T: friction per meter of sheet pile soil with the base
Calculated, Tilt K = 11.97 > 1.4

The sliding Stability Calculations

 

Core parameters:
S: the shear strength of each steel sheet pile, S = Aτ
A: steel sheet piles per meter of basal area
τ: is the ultimate shear strength of pile
Calculated, Slip K = 16.24> 1.4

Steel Sheet Pile Inner Force Calculation

 

Inner Force calculation of determine the location of steel sheet pile when the shear is zero, then calculate the point’s moment, the maximum bending moment of steel sheet pile.

According to the structural type of steel sheet pile, we can get W = 850cm³, [σ] = 200MPa

From calculation, the internal forces for the steel sheet pile is 62.37MPa which meets strength requirements.

Sheet Pile Design and Sheet Pile Section: Sheet Pile Design and Sheet Pile Section

Sheet Pile Design and Sheet Pile Section: Sheet Pile Design and Sheet Pile Section: "U type sheet pile U type sections have been widely used for various types of permanent and temporary structures, an..."

Sheet Pile Design and Sheet Pile Section

U type sheet pile

U type sections have been widely used for various
types of permanent and temporary structures, and
one of the most familiar sheet piles among designers
as well as users.

 

FSP-II,III,IV are solidly designed.
These sections are especially suitable for
repeated use, and have acquired high market
acceptance from users.

 

U type sections offer section modulus ranging from
874 cm3 to 3820 cm3 per linear meter of wall.

 

 

Box type sheet pile

Box type sections are made of two U type sections welded together into a box shape. Appropriate combination
of sheet piles makes available a wide range of section modulus, and depending upon design requirements,
the most suitable and economical combination can be selected.

Having section modulus ranging from 4170 cm3 to 8750 cm3 per linear meter of wall, Box type sections are
suited in large quay walls.

The length of each U type sheet pile welded together into a box section can be changed to meet design
conditions, and this means great economy. 

Z Steel Sheet Pile Sections

Normally, there are AZ, PZ sections. The unique characteristics of the Z sheet pile are the continuous form of the web and the specific location of the interlocks on the outside of the profile, presenting the following advantages:

• an extremely competitive relation section modulus/mass;
• an increased inertia reducing the deflection;
• no reduction of bending moment due to oblique bending or displacement of the neutral axis.

 

 
 

All of our sheet piles according ASTM A 328, ASTM A 690 standards

with continuous form of the web and the location of the interlock symmetrically on each side of the eneutral axis. It has great improvement on the section modulus. Following are the main advantages:

1. Large width, good installation performance

2. Extremely competative of section-modulus to mass ratio

3. Increased inertia for reduced deflection

4. Good corrosion resistance 

About Shunli Steel Sheet Pile

Shunli Steel Group, consisted of Jiangsu Shunli Cold-formed Steel Industrial Co., Ltd, Jiangsu Shunli Racking Industrial Co., Ltd and Nanjing Channel (International) Trading Co., Ltd, is a leading manufacturer of cold-formed steel products in China. Shunli Steel Group established in 1996 ,and now occupies land area of 260, 000m2, with stuff of more than 700 people. The annual output is USD 1.3billion.

Shunli Steel Group is integrated with research, design, manufacture and development activity, project implementing and international business. The manufacture capability of cold-fromed steel products of the whole group is about 500,000tons per year and covers more than 4000 different kinds of products.

Shunli Steel Group is one of the main suppliers of government invested projects like Three Gorge project, Shanghai-Beijing express railway, capital airport, Jingtang steel bridge and beijing Olympic stadium, three gorge project, Shanghai Pudong international airport, Lian Yuangang nuclear power station and Xichang satellite launching center, etc. And the products also be sold all over the world and earned high reputation.

The main export products of Shunli Steel Group covers sheet pile, h-beam, ERW, pallet racking and steel structure and different kinds of steel channel. The products are popular applicated in all of the world.

For More information, please contact us :

Website : http://www.sheetpiling-china.com
Sale Manager : Joanna Shaw
Mobile : 86-(0)-13905190622
Phone : 86-25-84722733
Fax : 86-25-84730966
Email : 13905190622@139.com admin@shunlisteel.cn
Address : Apt.3405 Building B of New World Center, No.88 Zhujiang Road, Nanjing, China.
Add. of factory : No.2 Shuli Road, Jiangning Riverside Economy and Technology Development Zone, Nanjing, China.