What is the proper vinyl sheet pile driving method for different soil types?

“Pitch and drive” method is the most practical way of pile driving in loose soils especially when using short piles. Also called “set and drive”, this method installs piles one by one. However, with only one interlock in control, sheet piles have high tendencies of rotating from the axis and leaning forward or backward. Panel driving is recommended for the dense deposit of sands and compact cohesive soils such as heavy clay or in presence of obstructions. In this method, a number of piles are interlocked together before driving. The panel of piles is supported by guide frames and driven gradually in sequence, sometimes in a staggered manner. The method can achieve installations of longer piles in more difficult ground conditions with better results in sheet pile alignment and verticality. In cases of difficult ground conditions such as hard strata and the presence of obstructions, driving assistance is employed along with a proper selection of driving method and equipment. Jetting and drilling help by loosening or eliminating obstructions by creating pressure right under the tip of the sheet pile being driven. Long and slender PVC sheet piles require steel mandrels as supports when driven in such conditions. Mandrel, which shape is similar to sheet pile profiles, increases the rigidity of Plastic Sheet Pile and supports the weight of the driving equipment such as a vibro-hammer.

What is the proper machine to drive piles in different conditions?

Impact driving is suitable for all soil types but appears to create the highest degree of stress to sheet piles. It is more appropriate to cohesive soils and soft soils such as silts and peats, loose medium to coarse sand, and gravels free of rock inclusions. Drop hammers such as the hydraulic hammer are the common types of impact-driving machinery. Driving using vibratory hammers is ideal for non-cohesive or granular soils such as soft soils and round-grained sand or gravel. It has also shown satisfactory performance in sandy, silty, or softer clay soils. It is less effective in angular-grained materials and soils with a firm consistency. With the introduction of vibration, however, the sub-soil can be further compacted, increasing penetration resistance and ultimately-refusal. If this is the case, driving aids like jetting and drilling might be necessary.

What are the pvc sheet pile selection criteria for soil condition of different hardness?

General rule of the thumb: “the harder the soil, the stronger and stiffer sheet pile section should be used”. Driveability of a pile section is a consequence of its cross-sectional properties (thickness, depth, and width), designed shape, length, grade, and the applied load. Hardness of soil strata characterized by SPT or CPT values is used to predict soil resistance which is essential in the calculation of driving force to be applied. Knowing the range of force from the selected driving machine, corresponding sheet pile sections can be picked according to their yield strength and elastic modulus.

How should I choose a sheet pile section for soils with, say, SPT Value, N=30? Can I still consider using vinyl or shift to steel?

Every sheet pile material has a design purpose, strengths, and areas of improvement. The availability of different materials denotes the need for a special material for a specific application. Plastic or synthetic sheet piles for example are known for being light and corrosion-resistant; Steel sheet piles are recognized for their extraordinary strength and versatility; and so on.

Application of Steel Pipes in Marine Construction

Steel pipes are basically used in marine construction due to constructability reasons. Aside from its capability to be driven with ease to create deep foundations, it also durable and has high inertia that counters high pressure and heavy loads from different directions. Other than pipe piles, steel pipes such as structural components are fabricated off-site making them easier to install to form modules or sea-borne structures. Other steel pipes are also common and best suited in oilfields and shipbuilding.

However, exposure to highly corrosive environment has long been a challenge in using steel pipes in marine applications. To minimize the impact of corrosion, marine-grade steel pipes are preferred such as stainless steel, duplex steel coated carbon pipes, and hot-galvanadium-galvanized steel pipes. The specific type of steel pipe to be used is of course determined by the needs of the project or what is specified in the project design documents. Steel pipes are mostly used to construct foundation for bridges and other marine structures. Other specific usages are described as below.

Bridge Construction

Steel pipes have higher load bearing capacity and toughness compared to most construction materials. This makes it very suitable for construction of bridges especially those with longer spans. In most cases, steel pipes are used to construct foundations. Steel pipes can be driven piles that serves as the foundation itself or as encasement or caisson that facilitates pouring of concrete especially underwater. As a hollow section with strong walls, it is easy to drive steel pipes into layers of weak soil or into rock formations to achieve the desired integrity of foundation works.

Dock Construction

Just like in bridges, steel pipes can be driven deep into the ground in order to provide adequate support for docks, as a part of the foundation or to aid concrete pouring. Mostly steel pipe pilings with anti-corrosive coating are used for building docks. This is because they don’t just provide considerable load bearing capacity, but they also offer corrosion resistance enabling the dock to maintain its structural integrity and serve its designed life span.

Combi-wall Construction

A combi-wall is a combination of large-diameter steel pipes and sheet piles. It mostly serves as a retaining wall. Unlike secant or sheet pile walls combi-walls provide more strength and durability especially against heavy lateral pressure. The steel pipes make up most of the wall’s structure. The pipes provide resistance to overturning forces whereas the sheet piles serve as in-fill between the pipes. Some of the construction projects where combi-walls are employed include port expansion, quay wall and jetty construction, pier construction, lake filling, and other retaining wall structure construction.

Trestle Construction

Trestle mostly serves as a support structure during bridge construction. It is often a temporary structure. Where a trestle is intended to serve as a foundation, steel pipes are driven into the soil or seabed to create a strong foundation. To stay in place, the pipes are normally strengthened by reinforced concrete.

Berthing/Mooring Structure Construction

The so-called dolphin is a cluster of pipe piles driven through the seabed forming a tripod and extends above water surface that works as independent mooring point or as structure aligned with jetties to provide wider berthing surface. They are also used as structures to hold navigation aids and beacon lights. Coated carbon steel pipes are commonly utilized as dolphin piles due to corrosion-resistance requirements.

Offshore Structures

Steel pipes are widely used in offshore structures such as helipads, storage and offloading system platforms, oil rig & accommodation platforms, wind mills, and others. From driven piles to the smallest structural members, corrosion-resistant steel pipes are favourably useful in these applications because of their dynamic characteristics that has positive response to harsh environmental activities such as strong winds, tidal waves, and strong currents.

There are two types of pipes used in offshore structures: metal and non-metal. Among the metal pipes are copper-nickel alloy, stainless, hot-galvanadium-galvanized, & carbon steel pipes. Non-metal pipes are FRP and plastic composites.

Listed below are some information about different types of steel pipes:

Copper-nickel alloy pipe has good seawater corrosion resistance, good hydraulic performance, good resistance to growth of sea life, and long service life. However, copper-nickel alloy pipes are expensive and has poor mechanical strength.
Stainless steel pipe has good corrosion resistance and mechanical properties but prone to pitting corrosion which is easy to occur in seawater medium caused by sulphur.
Carbon steel pipes are often inexpensive. They hold high ductility, strength, workability, and they are safe and durable. Where the water is salty, they are likely to suffer from corrosion. Engineering measures such as epoxy coating and hot-dip galvanizing can solve the problem of carbon steel pipes in seawater but requires regular and effective maintenance program.
Hot-galvanadium-galvanized steel pipes are coated with zinc to prevent them from rusting.
Duplex stain-less steel pipes have a two phase-microstructure consisting of grains of ferritic and austenitic stainless steel hence the name duplex. Unlike traditional stain-less steel pipes, they are able to prevent pitting corrosion from sulphur in sea water.

SETTLE AND DISCUSS WITH ESC’S PROFESSIONAL

Choosing the right pipe material for marine application is crucial. Corrosion due to seawater exposure is a major concern that has to be taken care during material shortlisting. It is important to weigh the advantages and disadvantages of different types of steel pipes in terms of performance and economic feasibility.

ESC produces a wide range of steel pipes of up to 4,267mm diameter and 100mm thickness by LSAW, SSAW and ERW manufacturing processes. We are also a global provider of corrosion protection solutions that includes: Coal Tar Epoxy Coating, Glass Flake Epoxy Coating, Hot Dip Galvanizing, Cathodic Protection, and Duplex Coating System.

For professional assistance, please don’t hesitate to reach us escglobal@escpile.com

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Application of Steel Pipes in Marine Construction