Development of a Speargun Projectile Penetrometer in Soil

This study investigates the applicability of a speargun projectile penetrometer (SPP) for offshore site investigation purposes using experimental testing. The SPP can shoot penetrometers using an elastic/pneumatic force. The speargun is easy to handle, can generate significant kinetic energy and requires a single operator to perform the test. A laboratory test platform was utilised to hold the SPP and ensure vertical launch, while a laser displacement sensor was employed to monitor the penetration depth and record the corresponding time history. The result demonstrated that the speargun-launched method achieves significantly higher embedment depth compared to an equivalent free-falling penetrometer. In particular, the new method produces sufficiently deep penetration in dense sand thus overcoming the typical penetrometer tilting issue caused by shallow penetration. These findings provide a preliminary insight into the speargun projectile penetrometer, allowing for exploration beyond the boundaries of traditional penetrometers in laboratory testing and offshore site investigation.