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.

Understanding Mono-Extruded and Co-extruded Vinyl Sheet Pile

Vinyl sheet pile or also called synthetic and plastic sheet pile is an innovative earth-retention and excavation-support material alongside steel, concrete, and treated wood. Besides its high level of durability and aesthetics, it is proven to be the most sufficient and cost-effective option for hydrotechnical engineering and construction applications especially seawalls & waterfronts, flood control, and bulkheads.

Vinyl sheet pile is made from modified PVC (polyvinyl chloride). It is produced by grinding and melting recycled PVC compounds along with refining ingredients (hardness modifiers and thermal or UV stabilizers), forcing it through a mold where it takes shape, cooled, and then cut to desired lengths. The forming process is called extrusion.

Extrusion of vinyl is done in two ways – mono extrusion and co-layer extrusion. Both mono-

extruded and co-extruded vinyl sheet pilings creates high-quality sheet pile walls. In a glance, they may appear the same but actually have significant difference to both manufacturer and consumer’s end.

Mono-extruded Vinyl Sheet Pile

Mono-extrusion is a traditional process of forming different shapes and sizes of vinyl sheet profiles from single layer of material. From the word “mono”, it is composed of only one material from the core to its surfaces.

Advantages:

1. It only requires one extruder so fixed-asset investment is less.

2. Involving only one material and extruding machine requires lesser technical expertise to run production.

3. When scratched, the color remains the same because of its consistent composition from outer layer to the core.

Disadvantages:

1. Due to one-material composition, the core of the sheet pile has the same ingredient as in its outside surface. This makes mono-extruded vinyl profiles considered unnecessarily expensive because ultraviolet (UV) inhibitors, typically the most expensive ingredient in the mix, are present in the core where they are actually useless.

2. Color of mono-extruded vinyl sheet piles can vary from batch to batch of production due to variety of raw material sources.

Co-layer or Co-extruded Vinyl Sheet Pile

Co-extrusion is a modern process in producing vinyl sheet piles that works by extruding two compounds at the same time to form a desired profile. It typically involves using a cheaper substrate material to give the sheet its mass and a more superior outer layer called “capstock” to protect the exposed surfaces primarily from UV radiation.

Advantages:

1. The capstock provides a high degree of UV protection to the sheet pile. Due to the optimized formulation of the protective layer, some manufacturers guarantees their co-extruded plastic sheet pile products to beyond 50 years of of lifespan.

2. Co-extruded vinyl sheet piles are cheaper because the core material does not necessarily contain ingredients such as UV inhibitor. The core is formulated to develop more of impact-resistance rather than UV resistance.

3. The combination of high-strength substrate and high-performance UV protection layer allows construction of taller walls and enhanced drivability of sheet piling into deeper and more difficult grounds. This is basically the principle of extruding two different materials, focusing strength to the core and protection to the outside layer.

4. High-quality capstock provides color consistency unlike mono-extruded materials which has tendencies to vary in color or shade by batch.

5. Overall, they are more cost-effective than mono-extruded sheet piles due to the strategic concentration of two materials with different strengths.

Disadvantages:

1. When scratched, the damaged portion reveals a different color which is the color of the substrate.

Which Material is Better for the Consumers?

Key features such as strength, durability, and UV performance are considered equal for both extruded profiles. Manufacturers of mono-extruded and co-extruded vinyl sheet piles also offers the same length of warranty as a result of the confidence built upon the promising track records of both materials. However, there is one aspect that separates the two finished products - cost. Co-extruded plastic sheet piles appears to be slightly more economical with the added consolation of long lasting beautiful appearance.

However, there are other critical factors that may affect the product cost and concerns both manufacturers and consumers. They are as follows:

1. Co-extrusion requires bigger investment in equipment which also affects the market price of end-products.

2. Mono-extrusion requires smaller equipment cost but higher material cost. In this case, fixed asset cost is low but raw material prices are volatile, thus, product prices can also be unpredictable.

3. Co-extrusion has more complexed operations and requires higher level of expertise. Manpower skill in this case is a critical criteria that controls quality and safety matters.

ESC is a world-leading provider of all kinds of sheet piles – vinyl, steel, and FRP. Yes, we have it all, plus we have our highly-experienced professionals to attend all your sheet piling needs and queries. Let us be of help to provide the best option and value to your project. Please contact us at www.escpiling.com