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.