Validation of impact penetrometer data by cone penetration testing and shallow seismic data within the regional geology of the Southern North Sea

Abstract

This study presents the assessment of total cone resistance from in situ deceleration measurements using the Lance Insertion Retardation meter (LIRmeter) in the Southern North Sea. The penetrometer is equipped with a measurement lance that is up to 6 m in length. The aim was to validate LIRmeter data interpretation within the regional geological context by comparison with static velocity cone penetration testing (CPT) and sub-bottom profiles. In total, 13 datasets were taken, in addition to preexisting hydroacoustical and static velocity CPT datasets. The dynamically acquired data were processed and compared to the reference static velocity data. The validation encourages the use of acceleration-based dynamic penetration tests, since a high degree of agreement was demonstrated between independently acquired dynamic and static cone resistance data. Moreover, the results reveal evidence of two successive formations with different geotechnical properties, consistent with existing knowledge on the regional setting. Additionally, there is novel indication of an incised glacial valley with muddy low-permeability sediments extending much further than reported to date, which would necessitate updating of older maps. The main advantage of penetrometer-based deceleration measurements lies in the robustness of the method, and the reliability of the sensors. However, penetration depth is, for dimensioning reasons, limited to the order of a few meters. Additionally, data processing includes the dependency of knowledge about the soil type to correct the dynamic data. These limitations can be satisfactorily outweighed by combination with reference data from static velocity tests, as demonstrated by integrating these data into a soil classification scheme.

Application of portable free-fall penetrometer for geotechnical investigation of Arctic nearshore zone

“…and an empirical factor K ranging from 1-1.5 based on the results by Stoll et al (2007), Stark et al (2012b, and Stephan et al (2015) for high velocity impact penetrometers. K is expected to depend on the soil type and behavior during penetration.…”

“…A goal for these tests is to relate K to a property measured directly by the penetrometer (e.g., a combination of deceleration over penetration depth and/or pore pressure). For the current data set, an uncertainty in quasi-static bearing capacity of about 15% results from the uncertainty related to K, allowing the ranging of K based on studies by Stoll et al (2007), and Stephan et al (2015) for high velocity impact D r a f t penetrometers. It should also be noted that a different choice of K would have little impact on the final conclusion drawn in this study, which are also supported by the measured deceleration records (Stoll et al 2007;Stark and Wever 2009).…”

Rapid sediment mapping and in situ geotechnical characterization in challenging aquatic areas

“…Dayal and Allen () proposed to correct the dynamic sediment strength (dynamic refers to changing penetration velocity and strain rate) for the strain rate effect, leading to a quasi‐static strength equivalent to measurements conducted at a chosen constant penetration velocity (industry standard for Cone Penetration Testing: 2 cm/s). The strain rate factor chosen for this study, f sr , is based on an empirical relation between the dynamic penetrometer penetration velocity v , which was determined from the first integration of the deceleration‐time profile, and a constant penetration rate v ref (Dayal and Allen ): where K is an empirical constant that can be assumed to range from 1.0 to 1.5 (Stoll et al ; Stark et al ; Stephan et al ). K = 1.25 ± 0.25 was used in this study to account for the range of suggested values.…”

“…where K is an empirical constant that can be assumed to range from 1.0 to 1.5 (Stoll et al 2007;Stark et al 2012;Stephan et al 2015). K 5 1.25 6 0.25 was used in this study to account for the range of suggested values.…”

Advances in Projectile Penetration Mechanism in Soil Media

“…There are two types of impact penetrometers available, i.e., lightweight devices for near-surface investigations [147] and huge penetrometers [148] for anchor performance evaluation. From field testing and laboratory observations, Lunne et al [146] and Stephan [149] show that quantitative measures, such as cone resistance, bearing capacity, shear strength, or void ratio, can be extracted through further processing of qualitative penetrometer data. "Chow and Airey [150] present an empirical model based on model penetrometer tests and reference triaxial tests to determine undrained shear strength of clayey soil targets and the influence of penetrator mass, penetrator tip shape, impact velocity, and the strain rate on undrained shear strength".…”