Cohesionless... like sand. Sand will pile up, and, yes, there will be a particular angle (the angle of internal friction which is dertermined by the "slippage factor" between the particles as Robin has mentioned) to the exterior of the slope.

An example of a cohesive material would be clay, as in, say, a clay brick.

Seems like few people are interested in this, so I'll spill the beans now

In addition to the "slippage factor" ("friction factor") within the sand pile, there is a friction between the sand and the dock. This friction exerts a tensile force on the dock acting from centre of the plie toward the edge of the pile. When this tensile force exceeds the tensile strength of the dock, the dock is pulled apart in the horizontal direction.

Failure analysis is some cool, eh?