Feasibility of Using Green Laser in Monitoring Local Scour around Bridge Pier

Abstract

Scour around bridge piers is considered as one of the major factors which causes failure of bridges in the United States. An undetected scour can affect the stability of the bridge, eventually leading to the collapse of the bridge. The experimental investigation of scour around a pier using a non-contact measuring method is carried out in this research. A green laser-based non-contact ranging technique is performed on a prefabricated scour hole to study the factors influencing the ability to reconstruct the shape of a scour hole. The experiment was conducted in a 10 ft diameter pool and Leica scan station II was used for the scanning of the scour hole. The turbidity of the water was changed by adding Kaolinite powder to the water. The turbidity was varied from 1.2 NTU to 20.8 NTU by adding Kaolinite. The lab experiments involved changing the turbidity of water to simulate real world conditions. The results from the experimental study show that the turbidity of the water has a direct dependence on the efficiency of the green laser to map the underwater scour profile. The ability of the green laser to capture the fabricated scour hole and pool bed topography were decreased as the turbidity was increased even when the water depth of the pool was reduced. The results from the study show that the green laser is effective in underwater scanning and can be also used for bathymetry profiling and the detection of underwater objects. The method of underwater scanning using a green laser for detecting scour around bridge pier is safe, efficient, and economical.

Feasibility of Using Green Laser for Underwater Infrastructure Monitoring: Case Studies in South Florida

“…Scour needs to be monitored in a timely manner as around 80% of the railroad and highway bridges in the US are built over water bodies [1,2]. Natural disasters like earthquakes associated with heavy rain and flooding can severely damage bridges [3].…”

“…Scour around bridge piers are usually measured using in-contact and non-contact scour measuring devices. Some examples of in-contact sensors include float-out devices, tethered buried switches, piezoelectric sensors, buried rods, and radar devices [2,7]. A float-out device measures the scour when it is disconnected from the ground.…”

“…In recent years, there has been a shift towards non-contact scour measuring equipment and this equipment does not require the support of a diver and can be operated without being in direct contact with the scour. Some of the non-contact scour measuring devices are GPR (Ground Penetrating Radar), SONAR (Sound Navigation and Ranging), echo sounder, seismic profiler, and laser devices [2,7]. GPR sends electromagnetic waves to the scour profile, which are reflected to the device [17], whereas SONAR uses soundbased ranging for underwater and scour mapping [2,7].…”

“…Some of the non-contact scour measuring devices are GPR (Ground Penetrating Radar), SONAR (Sound Navigation and Ranging), echo sounder, seismic profiler, and laser devices [2,7]. GPR sends electromagnetic waves to the scour profile, which are reflected to the device [17], whereas SONAR uses soundbased ranging for underwater and scour mapping [2,7]. Sound waves sent by the SONAR device gets reflected from the scour hole, and its dimensions are measured [18,19].…”

Scour Detection with Monitoring Methods and Machine Learning Algorithms—A Critical Review

“…A recent and successful study managed to locate and measure scour depths by combining SONAR data and a deep convolutional network [10]. Furthermore, it was revealed that although it performs worse in high turbidity, green laser technology was able to detect scour around bridge piers in an economic and safe way [11].…”