Forensic Investigation of Structural Failure: Using Surgical Hydrodemolition Techniques for Sample Collection

Recently our expertise was called upon by a client seeking assistance in a forensic investigation to uncover the root cause of a structural failure. This intriguing project presented us with an opportunity to employ surgical hydrodemolition techniques, executed manually, to selectively remove concrete and extract rebar samples for laboratory testing. This marked the first instance where we applied our specialized skills to investigate such a scenario, revealing the remarkable efficiency of this demolition method for this specific type of investigation. Through precise sample extraction, we were able to uncover the necessary areas without inflicting any detrimental impact on the remaining concrete or rebar, ensuring the integrity of subsequent testing results. 

Surgical hydrodemolition is a highly controlled process that employs pressurized water jets to selectively remove specific sections of concrete. In this investigation, we meticulously utilized hand-operated lances, delivering water at an impressive pressure of 40,000 psi (pounds per square inch) and a flow rate of 3 gpm (gallons per minute). The decision to use a low gpm pump was strategic, as it minimized back thrust, enabling unparalleled precision during the concrete removal process.

Safety is paramount in such specialized investigations, particularly when operating at high pressures. In compliance with safety standards, our team used TST suits to protect against potential hazards arising from pressures exceeding 20,000 psi. These suits are constructed from an ultra-strong and lightweight fiber known as Dyneema®(1). This advanced material exhibits exceptional strength properties, boasting strength levels 15 times higher than steel and up to 40% stronger than aramids. By employing these cutting-edge suits, our team mitigated risks and ensured the safety and well-being of all personnel involved.

A critical aspect of the investigation involved the extraction of 14 samples within a single day, as per the client's request. This task was conducted meticulously and with great care, guaranteeing the integrity of the samples. The next day, the exposed samples were carefully removed from the concrete and promptly dispatched to the laboratory for comprehensive testing.

The successful application of surgical hydrodemolition techniques in this investigation highlights the significant advantages of this approach in sample collection and investigation precision. By using hand lances with optimized pressure and flow rates, we could isolate specific sample areas without compromising the remaining concrete or rebar. The incorporation of state-of-the-art TST suits ensured the safety of our team members during the operation. The outcome of this investigation demonstrates the valuable contribution of scientific methods in forensic engineering, enabling us to provide critical insights to our clients while ensuring the safety and integrity of our operations.

40,000 psi surgical hydrodemolition By Hand

Source:

1 (TST Sweden - Elite Operator, 2023)