Spatial variability characteristics of the effective friction angle of Crag deposits and its effects on slope stability

This study investigated the spatial variability characteristics of the effective friction angle of Crag deposits which are granular soils occur in the east of England. Cone Penetration Test data were obtained at 26 locations and interpreted statistically. The distribution characteristic of the effective friction angle of Crag deposits was derived with the mean value, the standard deviation and the correlation length calibrated. Illustrations were also shown on how factors such as ground water pressures and the existence of soft/organic soil zones affect the measurement of the autocovariance function and thus the correlation length. Bayesian inference technique was adopted alongside the method of moments to determine the correlation length. Based on the obtained statistical parameters, both semi-deterministic (based on standard geotechnical design codes) and probabilistic finite element limit analyses were carried out to investigate the stability of slopes in Crag deposits. Slopes of various inclined angles were considered and comparisons between the semi-deterministic and probabilistic results were conducted to improve the understanding of the stability of Crag slopes and to provide insight into the slope stability code used in practice.

Automated summary

This study investigated the spatial variability characteristics of the effective friction angle of Crag deposits in the east of England. Statistical analysis was conducted on Cone Penetration Test data to derive the distribution characteristic of the effective friction angle, including mean value, standard deviation, and correlation length. The study also examined how factors like groundwater pressures and soft/organic soil zones impact the measurement of autocovariance function and correlation length. The findings were used to conduct semi-deterministic and probabilistic finite element limit analyses on slope stability in Crag deposits, providing insight into the design codes used in practice.