rockfill

Rockfill refers to an embankment fill composed primarily of rock fragments, used in civil engineering for structures such as dams, levees, retaining walls, and road or railway fills. In rockfill applications, the fill is typically formed from crushed or quarried rock and is placed in layers, compacted to achieve stability and interlocking of the particles. Where an impermeable barrier is required, a core of clay, concrete, or a low-permeability material is placed within the rockfill, with outer shells of rock to provide strength and drainage.

In rockfill dams, the design often includes a central impermeable core and two surrounding shells made of rockfill. Drainage is provided by filters and drainage layers to control seepage and prevent piping, along with toe drains and upstream drainage blankets to manage pore pressures during operation. The rockfill's permeability allows water to flow through the outer shells while the core restricts leakage, enabling controlled stability under various loading conditions, including seismic events.

Materials used range from coarse to fine rock fragments with good gradation. The presence of small fractions of fines can improve interlock but excessive fines can reduce drainage. Proper filtration between the core and shell materials is essential to prevent erosion of fine particles through the rockfill.

Advantages of rockfill include the ability to utilize locally available rock, good deformability to accommodate settlement, and favorable performance in seismic regions. Disadvantages involve the need for careful seepage control and filtration design to prevent internal erosion.

Rockfill is widely used for dams, retaining structures, river levees, and certain road or rail embankments, particularly where competent rock is abundant and drainage is a priority.