Data from laboratory testing of specimens from near the Barry Arm, Alaska, landslide

We performed ring shear strength tests of three specimens from a flysch unit involved in a large landslide that occupies a hillslope above the north side of Barry Arm in Prince William Sound, Alaska. A contract laboratory performed additional ring shear strength tests and index property tests. The test specimens are referred to as 22BABC001, 22BABC002, and RMC-02-220723. Ring shear tests used apparatus DPRI-5 at Kyoto University, Japan (Sassa and others, 2004), and test results are presented herein. Some tests were performed under controlled shear stress that simulated coseismic ground motions calculated from the Kyoshin Network (K-NET) MYG012 seismogram of the M 9.0 2011 Tohuku, Japan Trench earthquake (https://www.kyoshin.bosai.go.jp/en/ accessed July 22, 2026). Other controlled shear stress tests involved shear stress increased at ~0.5-1 kPa/s until failure occurred, and failure continued for decimeters to meters of cumulative shear displacement. These tests were performed on previously unfailed material and on shear gouge that developed during failure in the shear apparatus. Other tests were performed on shear gouge under constant shear displacement rates of ~0.0004–10 cm/s. Tests were performed in the undrained condition (specimen chamber water lines closed) or in the naturally drained condition (specimen chamber water lines open). Normal stress was controlled during all tests. Cumulative shear displacement, normal stress, shear stress, pore-water pressure, and specimen thickness were continuously measured during each test.

File names for ring shear test results obtained by using DPRI-5 sequentially indicate: specimen name_”consolidation”_approximate normal stress_sample number of the given specimen-test number for that sample_drainage condition_test type_”hold” or “consolidation”_sample condition.

”Consolidation” follows specimen name in file names for consolidation that followed the test performed immediately prior; that test name remains in the file name. ”Hold” or “consolidation” follows test type if the file contains data from immediately following the test; “hold” indicates that pore-water drain lines were closed during this period, whereas “consolidation” indicates that the drain lines were opened. Many files do not include data from a subsequent hold or consolidation period. Test types include “increased shear stress,” which involved applying shear stress at a constantly increasing rate (~0.5-1 kPa/s) to cause failure; “seismic” for simulated coseismic loading that may or may not have caused failure; and constant shear displacement rate tests with “#-### cms” indicating the average displacement rate in centimeters per second (for example, 1-004 cms for a test performed at 1.004 cm/s). Sample condition was either “unfailed” (not yet sheared) or “gouge” that developed during previous shearing in the apparatus.

Data columns in the ring shear test results obtained by using DPRI-5 are “time (s)” indicating elapsed time, “cumulative shear displacement (cm),” “total normal stress (kPa),” “shear stress (kPa),” “pore-water pressure (kPa),” and “specimen thickness (mm)” measured perpendicular to the plane separating the upper and lower parts of the specimen chamber, which is where shear displacement initiates.

A contract laboratory performed ring-shear tests using a standard Bromhead ring shear apparatus (for example, Meehan and others, 2007) to shear 22BABC002 specimens under naturally drained conditions at speeds of ~0.01-0.00001 cm/s. The laboratory also performed tests to measure particle size distribution (ASTM International, 2017a; 2021) and Atterberg limits (ASTM International 2017b) on each specimen. Shear test results are provided in 22BABC002_Bromhead_shear_strength.xlsx; particle size distribution results are provided in 22BABC001_particle_size_distribution.pdf, 22BABC002_particle_size_distribution.pdf, and RMC-02-220723_particle_size_distribution.pdf; and Atterberg limit results are provided in 22BABC001_Atterberg_limits.pdf, 22BABC002_Atterberg_limits.pdf, and RMC-02-220723_Atterberg_limits.pdf.

References
ASTM International, 2017a, Standard test methods for particle-size distribution (gradation) of soils using sieve analysis: ASTM D6913/D6913M-17, West Conshohocken, PA.

ASTM International, 2017b, Standard test methods for liquid limit, plastic limit, and plasticity index of soils: ASTM D4318-17e1, West Conshohocken, PA.

ASTM International, 2021, Standard test method for particle-size distribution (gradation) of fine-grained soils using the hydrometer analysis: ASTM D7928-21e1, West Conshohocken, PA.

Meehan, C. L., Brandon, T. L., and Duncan, J. M., 2007, Measuring drained residual strengths in the Bromhead ring shear: Geotechnical Testing Journal, ASTM, vol. 30, no. 6, p. 466-473.

Sassa, K., Fukuoka, H., Wang, G., and Ishikawa, N., 2004, Undrained dynamic-loading ring-shear apparatus and its application to landslide dynamics: Landslides, vol. 1, p. 7–19.

Acknowledgements
We thank Peter Jacke (Benchmark Geotechnical Labs) for sample preparation and testing. We thank the Kyoshin Network (K-NET) for providing seismograms. Any use of trade, firm, or product names is for descriptive purposes only and does not imply endorsement by the U.S. Government.