5.2. RUBBLE-MOUND STRUCTURES
193
rubble-mound structure testing as carried out at the former Hydraulics
Research Station in Wallingford.
The following three sections briefly discuss some of the procedures that
have been used or recommended by experienced modelers. The discussion
is by no means complete, but instead is intended to provide the reader with
an appreciation of this special application of physical modeling in coastal
engineering.
Rubble-Mound Model Construction
Once model scales have been determined, the model structure designed, and
the test facility chosen, then model construction can commence. The first
step in model construction is to re-create the bathymetry in the vicinity
of the structure out to the depth adjacent to the facility’s wave generator.
For 2-d stability models a representative profile or slope is constructed in
the flume; for 3-d models accurate bathymetry is reproduced in all areas
that might influence the incident waves as they approach the structure.
It would be best to place the model structure on foundation material
similar to prototype, but this is seldom done because of difficulties in establishing correct similitude for foundation materials and because of the
additional efforts required in model operation. Using fixed-bed bathymetry
will not adversely affect armor layer stability studies because most damage occurs in the vicinity of the still water level; however, studies of toe
protection stability should consider the impacts of modeling on a fixed-bed.
Depending on the prototype situation, model bathymetry may be simply
a sloping bottom or complex topography. A common method for constructing fixed-bed bathymetry consists of making bottom elevation templates
that are affixed to the floor of the wave facility. The space between the
templates is filled with compacted sand and capped with a concrete veneer about 50-70-cm thick. Figure 5.4 shows 3-d model bathymetry under
construction at the Waterways Experiment Station.
Lillevang, et al. (1984) described a particularly detailed breakwater
stability physical model study where complex bathymetry was constructed
using bathymetric charts that had been enlarged to model size and glued
to the basin floor. Templates were placed on the chart depth contours,
and the space between templates was filled with sand and capped with a
concrete crust. Contours were separated by about 20 cm on average.
Hudson and Davidson (1975) and Hudson, et al. (1979) described how
rubble-mound structure models are constructed at the Waterways Experiment Station. The first step in model construction is to prepare the material
to be used in the rubble-mound model. Core material is generally crushed
basalt or limestone that has been sieved to the proper size distribution us-
193
rubble-mound structure testing as carried out at the former Hydraulics
Research Station in Wallingford.
The following three sections briefly discuss some of the procedures that
have been used or recommended by experienced modelers. The discussion
is by no means complete, but instead is intended to provide the reader with
an appreciation of this special application of physical modeling in coastal
engineering.
Rubble-Mound Model Construction
Once model scales have been determined, the model structure designed, and
the test facility chosen, then model construction can commence. The first
step in model construction is to re-create the bathymetry in the vicinity
of the structure out to the depth adjacent to the facility’s wave generator.
For 2-d stability models a representative profile or slope is constructed in
the flume; for 3-d models accurate bathymetry is reproduced in all areas
that might influence the incident waves as they approach the structure.
It would be best to place the model structure on foundation material
similar to prototype, but this is seldom done because of difficulties in establishing correct similitude for foundation materials and because of the
additional efforts required in model operation. Using fixed-bed bathymetry
will not adversely affect armor layer stability studies because most damage occurs in the vicinity of the still water level; however, studies of toe
protection stability should consider the impacts of modeling on a fixed-bed.
Depending on the prototype situation, model bathymetry may be simply
a sloping bottom or complex topography. A common method for constructing fixed-bed bathymetry consists of making bottom elevation templates
that are affixed to the floor of the wave facility. The space between the
templates is filled with compacted sand and capped with a concrete veneer about 50-70-cm thick. Figure 5.4 shows 3-d model bathymetry under
construction at the Waterways Experiment Station.
Lillevang, et al. (1984) described a particularly detailed breakwater
stability physical model study where complex bathymetry was constructed
using bathymetric charts that had been enlarged to model size and glued
to the basin floor. Templates were placed on the chart depth contours,
and the space between templates was filled with sand and capped with a
concrete crust. Contours were separated by about 20 cm on average.
Hudson and Davidson (1975) and Hudson, et al. (1979) described how
rubble-mound structure models are constructed at the Waterways Experiment Station. The first step in model construction is to prepare the material
to be used in the rubble-mound model. Core material is generally crushed
basalt or limestone that has been sieved to the proper size distribution us-