Undrained Shear Strength of Offshore Sediments from Portable Free Fall Penetrometers: Theory, Field Observations and Numerical Simulations

2017 ◽  
pp. 391-399 ◽  
Author(s):  
N Stark ◽  
K Ziotopoulou
Keyword(s):  
Shear Strength ◽  
Numerical Simulations ◽  
Free Fall ◽  
Undrained Shear Strength ◽  
Field Observations ◽  
Undrained Shear ◽  
Offshore Sediments

Evaluating the sealing potential of young and thin mass-transport deposits: Lake Villarrica, Chile

2019 ◽  
Vol 500 (1) ◽  
pp. 129-146 ◽  
Author(s):  
Jasper Moernaut ◽  
Gauvain Wiemer ◽  
Achim Kopf ◽  
Michael Strasser
Keyword(s):  
Shear Strength ◽  
Mass Transport ◽  
Pore Pressure ◽  
Sediment Cores ◽  
Free Fall ◽  
Undrained Shear Strength ◽  
Excess Pore Pressure ◽  
Minor Role ◽  
Mass Transport Deposits ◽  
Undrained Shear

AbstractSubaqueous mass-transport deposits (MTDs) can be important elements in hydrocarbon systems, forming potential reservoirs or seals. Most research has targeted outcrops or moderately to deeply buried MTDs and, therefore, the petrophysical properties of near-seafloor MTDs, and their influence in the trapping and release of shallow fluids, is poorly studied. Here, we investigate shallow MTDs in Lake Villarrica (Chile) by combining sub-bottom profiles, free-fall penetrometer data, pore pressure dissipation tests and geotechnical properties of sediment cores. Low undrained shear strength under a surficial MTD indicates underconsolidation caused by sudden loading and rapid sealing. Larger, buried MTDs show acoustic signatures of free gas at their base, indicating effective sealing. This is supported by degassing core gaps just below MTDs and by excess pore pressure ratios c. 30–70% within MTDs. Acoustic windows below rafted blocks suggest local fluid escape. MTDs exhibit elevated undrained shear strength and reduced porosity compared to surrounding sediments, but are comparable to upslope source sequences. This suggests that MTD sealing capacity in Villarrica relates to the apparently overconsolidated nature of the slope sequence, leaving a minor role for shear densification. This study shows that shallow MTDs can form a relatively rapid seal for fluid migration, locally degraded by rafted blocks.

In situ undrained shear strength characterization using data from free fall ball penetrometer tests

2018 ◽  
Vol 104 ◽  
pp. 310-320 ◽  
Author(s):  
Divya S.K. Mana ◽  
Abhishek Ghosh Dastider ◽  
Prasenjit Basu ◽  
Santiram Chatterjee
Keyword(s):  
Shear Strength ◽  
Free Fall ◽  
Undrained Shear Strength ◽  
Using Data ◽  
Strength Characterization ◽  
Undrained Shear

Practical Design Process for Flowlines With Lateral Buckling

2010 ◽  
Author(s):  
Joe Jin ◽  
Jean M. Audibert ◽  
Wan C. Kan
Keyword(s):  
Shear Strength ◽  
Design Process ◽  
Undrained Shear Strength ◽  
Operating Conditions ◽  
Field Observations ◽  
Lateral Buckling ◽  
Design Guideline ◽  
Design Basis ◽  
Axial Resistance ◽  
Undrained Shear

In the past decade, lateral buckling has received growing attention in flowline design. Joint Industry Projects (JIPs) have led to publications of design guidelines, such as the SAFEBUCK design guideline and DNV recommended practice F110. Safe design of flowlines with lateral buckling involves complex considerations. Inadequate or late recognition of such complexities often results in major impacts on project execution. Experience gained in recent projects allowed us to improve the design process and design methods with incorporation of practical considerations. This paper presents three key aspects in developing robust flowline design with lateral buckling issues: 1) understand and reduce uncertainties in design basis for lateral buckling assessment, including operating conditions, characterization of geotechnical properties and flowline installation; 2) determine flowline-soil interactions with incorporation of field observations and engineering judgment; 3) manage impacts of lateral buckling through all project phases. This paper shares several key engineering considerations successfully used in recent flowline projects in deep waters where the seabed soil is characterized as soft clay. First, calculation of flowline embedment based on remolded shear strength instead of undrained shear strength eliminates the need to guess the embedment dynamic amplification factor. This approach is based on cyclic degradation of the soil shear strength and field observations. Second, a simple engineering model of axial resistance is proposed. The axial resistance is a cumulative behavior and hence only the average undrained shear strength is used for the calculation. Third, a robust engineering solution takes alignment in establishing quality design basis, engineering judgment to avoid unrealistic design load combinations, and trade-off among lateral buckling design effort, flowline construction and installation, and qualification of flowline capacities. And last, early recognition of lateral buckling issues and development of mitigation strategies are keys to project solutions. This paper also suggests that lateral buckling is very complex in reality and requires more investigations.

scholarly journals Evaluation of Undrained Shear Strength of Miocene Clay from the Weight Sounding Test (WST)

2017 ◽  
Vol 62 (2) ◽  
pp. 367-384
Author(s):  
Sebastian Olesiak
Keyword(s):  
Shear Strength ◽  
Field Testing ◽  
Field Investigation ◽  
Undrained Shear Strength ◽  
Cohesive Soils ◽  
Strength Parameters ◽  
Additional Measurement ◽  
Carpathian Foredeep ◽  
Innovative Solution ◽  
Undrained Shear

Abstract Soil strength parameters needed for the calculation of bearing capacity and stability are increasingly determined from field testing. This paper presents a method to determine the undrained shear strength cuWST of the soil, based on the Weight Sounding Test (WST). The innovative solution which allows for a significant reduction of equipment needed for geotechnical field investigation is presented. The proposed method is based on an additional measurement of the torque during testing. It then becomes possible to estimate the undrained shear strength, cuWST of the soil, using the correlation given in this paper. The research results presented in this paper were carried out on selected cohesive soils, Miocene clays from the Carpathian Foredeep.

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