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.

ESC Group
- Oct 1, 2022
- 4 min read

Which Is Better, Steel or Aluminum Trench Shield?

Name: ESC Group (Middle East)
Address: Industrial Area City of Abu Dhabi, Abu Dhabi, 131355, AE
Telephone: +971 2550 6188
Price range: AED

Trench shields or trench boxes are usually made of steel or aluminum because both are strong and durable metals besides being abundant, recyclable, and cost-effective. In excavation and trenching works, steel and aluminum trench shield equally shares critical contribution in improving safety, quality, and productivity at construction sites. However, there are comparisons between the two with reference to their economical and overall performance.

The best way to understand or compare the two is possibly by establishing their features as raw materials and citing their pros and cons as finish products. It is important to dig into their features against the essentials of trench protection system like weight, cost, strength, and lifespan.

AS RAW MATERIALS:

Strength to Weight Ratio

Aluminum has a tensile strength of 100 MPa and a density of 2.70g/cm3. Structural steel has a tensile strength of 350 MPa and a density of 8.0g/cm3.

Therefore, aluminum is lighter than steel. Steel is stronger than aluminum.

Cost

At same weight, aluminum is more expensive than stainless steel. However, aluminum is about 3X lighter than structural steel.

Therefore, at same volume, steel is generally cheaper but can be more expensive than aluminum at some point.

Hardness/Malleability

Grade 5052 aluminum is very soft or malleable. Grade 6061 is likely to crack if bent. Steel is less likely to warp or bend from force, impact, or heat.

Therefore, aluminum is weaker than steel and more prone to dents and scratches.

Corrosion Resistance

Aluminum has excellent corrosion resistance and does not rust. Aluminum alloys comes in different classifications such as 6061 and 5052 which is considered a marine grade. Structural steel with iron as main composition triggers oxidation when exposed to oxygen, thus, prone to rust.

Therefore, steel must be equipped with a superior coating system to inhibit good corrosion resistance next to aluminum.

AS TRENCH SHIELD PRODUCT:

Weight

Steel trench shield is typically 2X heavier than aluminum shield. Density of a material corresponds to its strength, making steel as the stronger between the two. However;

Due to its weight, steel shields requires larger plant or equipment to mobilize and install them. Lightweight aluminum shields at the other hand can be lifted by small machineries or by manpower.

Application

Steel shields as denser equipment has higher pressure ratings. Steel shields has standard or custom sizes up to 10ft high x 32ft long. Aluminum shields are available in sizes up to 8ft high x 16ft long. Steel cages or boxes are best suitable for deep and extensive excavation works.

Aluminum shields are ideal for smaller jobs such as emergency repairs and routine maintenance. They are also applicable for jobsites and situations where heavy equipment is not available or restricted.

Cost-effectivity

At a given size, steel shields are generally cheaper than aluminum shields although overall cost, say total project cost, may be different due to many contributing factors. Besides the cost of trench box unit, other expenditures like mobilization, installation, and labor cost adds up to the summary of actual price.

Steel shields requires larger machineries, more manpower, and bigger area to carry out assembly and installation. The bigger extent of operation also requires higher level of safety precautions. Aluminum trench boxes at the other hand, are easier to install but are limited to lower range of pressure ratings and area coverage. Aluminum shields when built to serve higher depth ratings may incur uneconomical prices or weight-strength imbalance.

Lifespan

Steel shields are tough and designed to endure extreme site conditions but they are prone to corrosion which greatly affects their performance and lifespan. Aluminum does not corrode but are weak against impact and abrasions.

Longevity of steel shields therefore varies from every circumstance. It is a matter of having different strengths and weaknesses. Their lifecycle depends on many conditions such as intensity of usage, manner of handling, maintenance & preservation routine, and more. It also depends upon engineering methods and techniques used to protect the metals from the adverse effects of the environment. Steel requires effective protective coating to counter corrosion while aluminum can be equipped with steel frames to withstand impacts and scratches.

WHICH METAL WINS?

The answer is NONE. Each material has distinct strengths suitable for every particular application.

Trenches and excavations comes in different magnitudes and configurations, they can be wide, deep, narrow, or shallow. Whichever is the case, it is important to employ the optimum, most practical trench protection solution available. While steel trench boxes are suitable for bigger jobs, the amount of work and money that goes into the installation process makes them impractical for smaller scopes. And while aluminum shields are ideal for smaller errands, the cost of upgrading them to achieve the robustness required for large applications is unjustifiable.

ESC OFFERS BOTH STEEL AND ALUMINUM TRENCH SHIELDS

Because of having a deep understanding and experience in the business, ESC offers both steel and aluminum trench shields in standard and custom sizes. Our equipment is cost effective, safe and versatile, relied upon by underground utility professionals, municipalities and private contractors, locally and international. All of our products are certified by Engineering Professionals and are compliant to OSHA’s excavation and trench safety standards.

Call us today at +971 2550 6188 or visit us at www.escpiling.com