West Toronto Diamond Grade Separation: Definitions

Interlocking steel pipe piles: Pipe piles make up the majority of the piles required for the West Toronto Grade Separation. They provide the structural strength and the required water tightness for the walls that will make up the structure for the lowered track section.

Impact hammers: Impact hammers are the fastest, most effective and reliable means of installing pipe piles. They provide a high level of accuracy, which is important because of the tight corridor dimensions and surrounding operational tracks. Impact hammers are also the noisiest.

(Conventional) vibratory hammers: In the industry, vibratory hammers are currently mostly used to remove piles out of alignment and/or temporary piles, but can also be used for pile driving. Vibratory hammers use vibration rather than impact to advance the pile; therefore, they have more difficulty getting through dense soil conditions at depth. Vibratory hammers are also less accurate with the sites soil conditions and depths of piles required for this project. Vibratory hammers do produce less noise; however, the vibration they produce is constant and can be unsettling to residents of the neighbourhood. The vibration levels produced by the vibratory hammer are also more difficult to control. For these reasons, the conventional vibratory hammer is only used for pre-work setup, and has not ever been used on the project for actual pile installation.

Computer-controlled (French or PTC) vibratory hammer:A unique computer-controlled vibratory hammer was brought in from Europe for this project. This machine allows much greater control of vibration levels, although when in use has caused some disruption in the neighbourhood. Progress with the machine has been slow, and often it has not been able to fully drive piles to the required depth.

Giken unit (or technology): This technology uses a hydraulic press-in method. The machine is one of two in the world with sufficient capacity to install the size of piles required for this project. The Giken unit has some significant limitations. The machine was brought in from Japan and was untested in the type of soil conditions at this site. With a maximum production rate of up to two piles per day, the project schedule will be significantly extended.

Shrouds: Hydraulically operated enclosures around the impact hammer that muffle the noise from the hammer impacting the pile, and the hammer itself. The shrouds are made using special sound absorbing material resistant to high temperatures, and were custom developed and fabricated for this project.

Noise walls: Sections of sound absorbing noise barrier (used along highways) mounted on a moveable frame.

Depowering of the impact hammer: Reducing the power produced by the hammer to soften the blow.This reduces the noise level by up to 10 decibels (50 per cent), but increases the number of blows needed to install the pile.