Malibol Washer

An extra large, thick washer used when bolting docks or timbers together to spread the tension over a larger area. Helps curb the elongating of the bolt holes caused by loosening and flexing of the timbers.

Mandrel

A core that is inserted into a closed-end thin-shell tubular pile for driving; after installation the mandrel is contracted and withdrawn; (1) solid or semi-solid mandrel - a heavy tubular section that will transmit the hammer energy to either the casing point or for a step-tapered pile to the transition rings or plow rings and the point; (2) collapsible mandrel - a core, the outer diameter of which can be changed by mechanical or other means, capable of transmitting the hammer energy to the bottom of the pile and the periphery of the thin-shelled casing. It is inserted into the pile in a collapsed condition and then expanded to grip the inner surface of the pile with sufficient force to prevent slipping.

Marine Borer

One of several species of mollusks (Tered0 - "Shipworm," Bankia, Pholad) and crustaceans (Limnoria - tripunctata, quadripunctata, Lignorum) that bore into untreated wood and concrete. Preservative pressure treatment is effective in protecting wood from their attack.

Marlin Spike

A tapered tool of steel or wood used to separate strands of rope or wire cable for splicing.

Marline

A small fiber twine used for seizing.

Mast Lead

See European Lead.

Mastic

A putty-like adhesive that maintains a degree of elasticity after setting.

Mats

Heavy timbers bolted together for use as support and roadway for pile driver crane. Essential over soft or wet supporting soil and to protect pavement.

Matt Foundations

Used in soils of low bearing strength. This type of spread foundation consists of a solid slab of heavily reinforced concrete placed beneath the entire building area. In some cases 3' to 8' thick.

Maximum Rated Load

Largest amount of weight a structure can safely support.

McDermid Plate

A proprietary part of a pile hammer seated directly under the ram which receives the blow of the ram and transmits it to the pile. Normally used only with wood pile. See Anvil, Cap Block.

Mean Low Water

The average low elevation to which the surface of a body of water falls. Mean High Water is average high. In tidal areas Mean Low (High) Tide is the average daily minimum or maximum water surface elevation.

Mechanical Valve Hammer

A hammer in which the valve is thrown by a mechanical linkage with the ram.

Michigan Tests

A comprehensive field test, principally aimed at determining load bearing criteria for driven pile, conducted in 1961 by the State of Michigan Highway Department and the United States Bureau of Public Roads.

Micro Piles

Small diameter piles; most often used in underpinning.

MLT

Maintained Load Test. Load test accomplished by applying an increasing load in defined increments and holding each level until such time that the pile top (head) displacement stabilizes or a specified time period is attained. A force vs. Displacement curve is plotted to which may be applied a definition of failures. Covered in ASTM D 1143. See CRP.

Modulus of Elasticity (E)

Quotient obtained by dividing the stress per unit area by the change per unit length in the elastic region of material behavior. Also called Young's Modulus (when unconstrained laterally).

Monkey

See Pile Monkey.

Monkey Stick

A spud lead system in which the lead column passes through a slide box at the top of the crane boom. The lead column elevation is controlled with a crane line and a brace is not normally used, the lead base being set on the ground. The hammer is mounted on the back side of the lead with cables coming directly from the crane boom point sheaves. See Spud Lead.

Monolithic Pour

A continuous mass of concrete cast as a single piece. Only construction joints are used.

Monotube

An open top, longitudinally-fluted tapered steel tupe, driven without a mandrel and filled as a cast-in-place concrete pile.

Montee Caisson

A steel caisson with sawtooth cutting edge, which is rotated to cut its way through rock. Loosened material is washed out of the caisson. More powerful motors and better cutting steels have brought a redevelopment of this once popular procedure.

Moonbeam

A curved or horizontal beam attached to the end of the brace on a pile hammer which allows the lead to be moved sideways and held fixed during the driving of side batter piles (right angle to the crane boom).

Mooring Cell

Individual sheet-pile cells built generally along river banks and used as a dock for mooring barges.

Mooring Pile

Usually a treated or greenheart wood pile, driven out from a pier or dock to steady marine vessels from wind and wave action, or to hold a floating dock in position. See Doplhin, King Pile.

Moraine

See Glacial Till.

Motive Fluid

See Fluid Power.

Mousing

The lashing around the open jaw of a lifting hook on a crane to prevent a sling or chocker from being detached when the line is slackened.

Moveable Jaw

Jaw on a vibratory pile driver/extractor that moves open or closed to lock onto the pile via a hydraulic cylinder. In some cases the jaw may move via a mechanical arm that is leveraged to provide the cylinder a mechanical edge.

Muck

1. A very soft or watery vlay.
2. A term used for material removed from an excavation, especially in tunneling.

Muck Bucket

Cylindrical tool used for cleaning drilled shafts of muck and water.

Mud Line

River bed at interface of water soil.

Mud Mat

A thin cover of crushed stone or concrete placed over a muddy area below the planned structure to provide a work platform and keep reinforcing clean.

Mud Wall

1. An earth diaphram or impervious cut-off-wall in a dam.
2. The wall above the beam seats of a bridge abutment, designed to support the approace slab and retain the earth behind the abutment.

Mudding-In

The technique of stirring in bentonite powder and/or water to facilitate the installation of a temporary casing or to expedite drilling into an augered or otherwise drilled hole.

Mudsill

A timber inbedded in the ground to support a framed bent.