01782032

Component

https://doi.org/10.1177/03611981211037895

Standard penetration tests (SPTs) have been used to estimate strength parameters of soils and weak rocks when it is difficult to obtain high-quality samples for laboratory shear testing. SPTs require 45?cm (18?in.) of split-spoon sampler penetration to determine the blowcounts per 0.3?m (1?ft), which is difficult to impossible to obtain in weak rock, that is, intermediate geomaterials. As a result, a modified SPT is presented here for sampler penetrations less than 45?cm (18?in.) in weak rocks. This new procedure is termed the modified standard penetration test (MSPT) and uses the penetration rate, not the sum of penetration blowcounts per 0.3?m, to estimate the unconfined compressive strength for the design of drilled shafts in weak fine-grained rocks. The penetration rate is the inverse of the linear slope of the penetration depth versus blowcount relationship. With this new test and interpretation procedure, 45?cm (18?in.) of sampler penetration is no longer required to estimate the unconfined compressive strength of weak rocks. An empirical correlation between MSPT penetration rate and laboratory-measured unconfined compressive strength is presented here for weak Illinois shale. This correlation could be used to estimate the unconfined compressive strength for the design of drilled shafts in weak rocks.

Timothy D. Stark https://orcid.org/0000-0003-2384-1868 © National Academy of Sciences: Transportation Research Board 2021.

English

0000-0003-2384-1868

0000-0001-6599-004X

0000-0002-3156-7670

pp 176-185

2022-2

Transportation Research Record: Journal of the Transportation Research Board

Web

References (15)

Compressive strength; Design; Rock drilling; Shaft sinking; Shale; Soil penetration test; Weak rock

Bridges and other structures; Design; Geotechnology; Highways

TRIS, TRB, ATRI

Sep 17 2021 3:13PM