Experience with Interface Shear Box Testing for Pipe-Soil Interaction Assessment on Sand

This paper is a companion paper to OTC 28671, titled "Experience with Interface Shear Box Testing for Axial Pipe-Soil Interaction Assessment on Soft Clay", and presents a similar range of experience and best practice recommendations for geotechnical laboratory testing to determine soil properties relevant to pipeline-seabed friction on sandy seabeds. The paper is underpinned by a new database that demonstrates the driving parameters that influence interface friction in granular materials. By accurately quantifying shear resistance along the pipe-soil interface under low normal stresses imposed by subsea pipelines, design ranges in friction can be narrowed and/or tailored to specific pipeline conditions. These improved geotechnical inputs to pipe-soil interaction can alleviate unnecessary axial expansion mitigation and lateral stabilization measures, unlocking cost savings otherwise unavailable through conventional testing. A large database is presented, compiled from both previously published research and unpublished recent industry experience with low normal stress interface shear testing using various modified direct shear box devices. The test database comprises several coarse-grained soil types of both silica and carbonate minerology tested against pipeline coatings of various material, hardness and roughness. The database populates a framework for assessing frictional pipe-soil interaction response, illuminating key trends from normal stress, interface roughness and hardness, and particle angularity, which otherwise remain elusive when examined through individual test datasets. This database and the populated framework provides guidance to pipeline and geotechnical engineers in the form of a basis for initial estimates of axial and lateral friction of pipelines on sand and an approach for improving these estimates via focused site-specific testing. The test database includes previously unreleased project data collected over the past few years for offshore oil and gas projects. Similar to its predecessor paper on soft clays (OTC 28671), this paper shares the authors’ collective experience providing guidance on the planning, execution and interpretation of low stress interface shear tests in sands. The combined databases across both papers provide a significant improvement in early stage guidance for characterization of geotechnical soil properties for subsea pipeline design.

Object gripping algorithm for robotic assistance by means of deep learning

This paper exposes the use of recent deep learning techniques in the state of the art, little addressed in robotic applications, where a new algorithm based on Faster R-CNN and CNN regression is exposed. The machine vision systems implemented, tend to require multiple stages to locate an object and allow a robot to take it, increasing the noise in the system and the processing times. The convolutional networks based on regions allow one to solve this problem, it is used for it two convolutional architectures, one for classification and location of three types of objects and one to determine the grip angle for a robotic gripper. Under the establish virtual environment, the grip algorithm works up to 5 frames per second with a 100% object classification, and with the implementation of the Faster R-CNN, it allows obtain 100% accuracy in the classifications of the test database, and over a 97% of average precision locating the generated boxes in each element, gripping successfully the objects.

Re-Evaluation of Fatigue Thickness Effect Based on Fatigue Test Database

This paper reassesses the detrimental effect on fatigue performance of welded structural steel joints due to thicker sections based on an extensive fatigue strength test database, taken from research programmes worldwide over the past half century, mostly from the offshore oil and gas and marine industries. The data entries in the database were evaluated to ensure its data integrity. Statistical analyses on these S-N data were performed with or without the thickness correction at different exposure levels to a corrosive environment, in order to re-evaluate the suitability of current standards in regard to the thickness effect. The study concentrated on T-joints, transverse butt-welded joints and tubular joints, as these are the most commonly used joint types in the offshore wind industry. The analysis indicates a general agreement of fatigue strength with the thickness effects in current standards for in-air conditions, but great conservatism for corrosive environments. In addition, the statistical models determined in this study can be used for a broader range of studies, such as probabilistic fatigue analysis.