30 Sep 04
(c) Velocities can be determined in the laboratory using scale model hydraulic testing. These models
are scaled at typically 1:120 but can range down to 1:50 if required. This laboratory method requires the
construction of a scale navigation model at the U.S. Army Engineer Research and Development Center
(ERDC). Figure B-8 shows a typical navigation model used for barge impact testing. An overhead record-
ing system is used to track the barge train in XYZ space on the navigation model. The data are collected
by a computerized acquisition system and then processed to determine the velocities and angles during
the entire approach to the lock. When performed in conjunction with a navigation study, these types of
experiments are cost-effective.
(d) After the construction of the model is complete, testing is conducted using a scale model barge
and towboat. The barge trains used for the experiments can be sized to fit the current and future trends of
navigation traffic. In addition, the testing can model the approach of the barge train at a variety of flow
conditions. Obtaining impact data at different hydraulic conditions should be an integral part of any
model test matrix. Velocities in the approaches should cover a minimum of three flow conditions where
probabilities can be defined by hydraulic curves for the site. A typical range of flows should not exceed
probabilities of 2, 50, and 99 percent. The hydraulic engineer on the design team should furnish these
values. A testing matrix for the project should also be developed for each flow condition that requires
testing. To provide a statistically significant sample size, a minimum of 30 experiments should be con-
ducted for each flow condition. Also, using two or more model barge train operators for the range of
experiments would yield better information on the range of impact velocities and angles.
(e) Caution should be exercised when interpreting the raw data from the experiments due to the scale
model effects of water near the structure. This cushioning effect of the barge train as it approaches the
lock wall creates a slowing in the velocity prior to impact into the wall. A solution to offset this effect
would be to use a time averaging scheme for the values of velocity 3 m (10 ft) prior to and 3 m (10 ft)
past (in scale) the point of impact.
(f) Another method to collect data on velocities is using time-lapse videotape or Time-Lapse Data
Acquisition (TLDAQ) system. These systems were first developed and utilized to collect velocity and
impact data for concrete deterioration models for the Upper Mississippi River Illinois Waterway
Navigation Study in Patev, Mlakar, and Bryant (2000). Additional research was conducted in the TLDAQ
systems to develop a PC-based computer data collection system that could incorporate needed measure-
ments (i.e., wind, flows, etc.) in the field. These systems were recently developed under the Innovations
for Navigation Projects R&D Program Barge Impact Work Unit and have been used in a wide variety of
navigation projects including, most recently, Kentucky Lock and J. T. Myers Lock and Dam. Figure B-9
shows the installation of this TLDAQ equipment at Kentucky Lock. This type of data collection system is
a very useful tool both to document the existing approach and examine any potential future needs or
design changes that might be required. While this methodology is most useful if the navigation conditions
are not drastically changed, it can still be applied to examine approach conditions of barge trains sub-
jected to the effects of hazardous outdrafts and existing current conditions at the site.
(g) TLDAQ systems require the installation of a video camera and computer acquisition system or
time-lapse VHS recorder. The camera is mounted to either a light standard on the existing approach wall or
lock chamber or a bridge over the approach. The recording device is placed either in a weatherproof case or
within a secure building. These systems are set up to record the motion of the barge trains as they navigate
the approach to the lock. These systems capture a wide variety of data and information that can be pro-
cessed later from the recorded media using different interpretational techniques to get velocities and angles.
(h) Table B-3 shows typical ranges of impact velocities for approach conditions to navigation lock
walls that are appropriate for preliminary analyses only. Accurate determination of velocities for final
design should be made using one of the methods presented above that may be appropriate.