A new shared miniature cone penetrometer for centrifuge testing

Model Tests and Numerical Simulations of Liquefaction and Lateral Spreading

Stone

et al. 2019

This paper compares experimental results from every facility for LEAP-UCD-2017. The specified experiment consisted of a submerged medium-dense clean sand with a 5-degree slope subjected to 1 Hz ramped sine wave base motion in a rigid container. The ground motions and soil density were intentionally varied from experiment to experiment in hopes of defining the slope of the relational trend between response (e.g., displacement, pore pressure), intensity of shaking, and density or relative density. This paper is also intended to serve as a useful starting point for overview of the experimental results and to help others find specific experiments if they want to select a subset for further analysis. The results of the experiments show significant differences between each other, but the responses show a significant correlation, R 2~0 .7-0.8, to the known variation of the input parameters.

Section: Densities and Penetration Resistancesmentioning

confidence: 99%

LEAP-UCD-2017 Comparison of Centrifuge Test Results

Kutter

Model Tests and Numerical Simulations of Liquefaction and Lateral Spreading

Stone

et al. 2019

“…The load cell and the hollow sleeve are attached to a rigid aluminum block, which allows for simultaneous advancement of both the rod and sleeve. Carey et al (2018) calculated for a vertical effective stress of 100 kPa and a maximum allowable tip force of 900 N, the device could safely penetrate sand with a relative density of about 100% to a depth of 4 m prototype scale without yielding the cone rod in compression.…”

Section: Designmentioning

confidence: 99%

“…Located just above the cone tip is a slightly larger tip O-ring with a 4 mm inner diameter and 1 mm cross section to prevent sand from filling the gap between the rod and sleeve. Preloading the tip O-ring is performed using a procedure described by Carey et al (2018). Carey et al (2018) performed a series of calibration experiments to test (1) load transfer from the tip O-ring into the sleeve, (2) the influence of lateral force on cone tip forces, and (3) cycling loading to check if the internal O-rings had changing hysteresis during repeat cycles of loading.…”

Section: Designmentioning

confidence: 99%

“…To eliminate variability that would be encountered by using different CPT designs at each centrifuge laboratory, a new CPT was designed with the goal that it will be low cost and not require specialty machining (Carey et al 2018). Total cost for the device, including the load cell, is less than $2000 US.…”

Section: Introductionmentioning

confidence: 99%

“…The devices were fabricated at a machine shop at UC Davis and distributed to each of the centrifuge laboratories. Carey et al (2018) discussed the design and calibration and provided a cross and direct comparison of results using the LEAP CPT. This paper will briefly review the design of the device and provide additional analysis of the results from the LEAP-UCD-2017 exercise.…”

Section: Introductionmentioning

confidence: 99%

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Comparison of LEAP-UCD-2017 CPT Results

Model Tests and Numerical Simulations of Liquefaction and Lateral Spreading

Gavras

Kutter

2019

A cone penetrometer was specifically designed for the LEAP project to provide an assessment of centrifuge model densities independent from mass and volume measurements. This paper presents the design of the CPT and analyses of the results. Due to uncertainty in the specifications about how to define zero depth of penetration, about 20% of the CPT profiles were corrected to produce more accurate results. The procedure for depth correction is explained. After these corrections, penetration resistances at the representative depths of 1.5, 2, 2.5, and 3 m (prototype depth) are correlated to the reported specimen dry densities by linear regression. Using the inverse form of the linear regression equations, the density of each specimen could be estimated from the penetration resistance. Kutter et al. (LEAP-UCD-2017 comparison of centrifuge test results. In Model Tests and Numerical Simulations of Liquefaction and Lateral Spreading: LEAP-UCD-2017, 2019b) found that the density determined from penetration resistance was a more reliable predictor of liquefaction behavior than the reported density itself. Finally, the centrifuge tests at different LEAP facilities modeled the same prototype in different containers using different length scale factors (1/20 to 1/44); thus the ratio of layer thickness to cone diameter was different in each experiment. It appears that the penetration resistances are noticeably affected by container width and, to a lesser extent, resistance is affected by the length scale factor.

LEAP-UCD-2017 Centrifuge Test at University of California, Davis

Model Tests and Numerical Simulations of Liquefaction and Lateral Spreading

Stone

Hajialilue-Bonab

et al. 2019

Three centrifuge experiments were performed at the University of California, Davis, for LEAP-UCD-2017. LEAP is a collaborative effort to assess repeatability of centrifuge test results and to provide data for the validation of numerical models used to predict the effects of liquefaction. The model configuration used the same geometry as the LEAP-GWU-2015 exercise: a submerged slope of Ottawa F-65 sand inclined at 5 degrees in a rigid container. This paper focuses on presenting results from the two destructive ground motions from each of the three centrifuge models. The effect of each destructive ground motion is evaluated by accelerometer recordings, pore pressure response, and lateral deformation of the soil surface. New techniques were implemented for measuring liquefaction-induced lateral deformations using five GoPro cameras and GEO-PIV software. The methods for measuring the achieved density of the as-built model are also discussed.