Geotechnical Engineering Online Library

In arid to semi-arid regions alluvial soil deposits can range from collapse-susceptible, variably cemented to indurated. In these soils, reliable estimation of soil properties based on penetration resistance indicators such as N-values from Standard Penetration Tests (SPTs) is difficult. Varying content of gravels and cobbles provides additional complexity. In such conditions, sample recovery from SPTs is limited and refusal N-values occur. This paper presents a database of 74 pressuremeter tests along portions of Interstate 10 (I10) through Tucson, Arizona, where soil conditions noted above were encountered. The results are used to evaluate the subsurface stratigraphy. Estimated side and base resistance for drilled shafts are presented and compared with recommendations by the American Association of State Highway and Transportation Officials (AASHTO) and the Federal Highway Administration (FHWA). Comparisons of estimated side and base resistances from pressuremeter tests with those from a large-scale load test are presented. Evaluation of the collapse potential of soils using pressuremeter tests is also discussed and the results compared with collapse potential based on 1-D laboratory tests.

The collapse of the soil structure due to wetting is called hydroconsolidation and it occurs only once under constant loading, in cases of perturbation of the soils moisture content. It is encountered usually in non-sedimentary soils such as anthropogenic fills and residual materials. This paper presents an interpretation of hydroconsolidation settlements in a building of the historical centre of Thessaloniki followed after a rise of the water table. The interpretation is based on the results of laboratory evaluation of hydroconsolidation properties, in conjunction with in situ measurements of settlements.

A 30-m long railroad embankment failure that occurred on May 25 2011 in the city of Ann Arbor, Michigan, is presented. Emphasis is given on the field observations of the failure, the characterization of the site conditions and the seepage and slope stability analyses, all of which represent important components of the training and practice of a geotechnical engineer. The failure occurred following a record wet season that resulted in ponding water against the embankment and high enough water pressures and exit gradients that resulted in instability of the railroad embankment. Detailed background material and the methodology for using the case history in geotechnical engineering education are presented.

Macroseismic observations in the meizoseismal area of the Achaia-Ilia, Greece, Mw 6.4 earthquake of 8 June, 2008, have shown that soil liquefaction occurred at a number of sites up to distances of 25 km from the causative fault. In one of these sites (SITE-I at coastal zone of Kato Achaia) the occurrence of liquefaction was extensive and was followed by lateral spreading. In another nearby site (SITE-II) only marginal liquefaction (or nonliquefaction) was observed. Following the macroseismic observations, a geotechnical investigation was carried out at SITE-I and SITE-II which included exploratory boreholes with continuous sampling, SPT measurements, CPT soundings, surface wave measurements (SASW, MASW, ReMi) and laboratory testing. Based on the results of geotechnical investigation, the soil stratigraphy and pertinent soil properties were evaluated in the liquefaction/nonliquefaction locations. The assessment of peak ground acceleration at the area of SITE-I and SITE-II was based on attenuation relations and shaking table tests performed to simulate the observed behavior of an overturned (during the main shock), barrel-shaped, plastic, water filled container sitting on the ground surface at SITE-I. It is believed that the data presented in this paper can be used to 1) check the validity of current liquefaction susceptibility criteria/liquefaction triggering relationships, and 2) establish a well documented liquefaction case history that can be part of future liquefaction databases.

Static loading tests, O-cell tests, were performed on two long, strain-gage instrumented, bored piles in HoChiMinh City, Vietnam, where a series of twelve apartment towers were to be constructed. The test piles were constructed to 76 and 91 m depth and tested to maximum O-cell loads of 10 and 18 MN, respectively. For both piles, the O-cell level was placed at a depth of about 20 % of the pile length above the pile toe. The soil profile consisted of very soft organic clay to about 10 to 15 m depth underlain by firm to stiff clayey soil to about 25 to 45 m depth. Hereunder, the soil consisted of a compact to dense sandy silt. Neither of the tests was able to fully engage the shaft resistance of the piles above the O-cell level, but did so below the O-cell level. Back-calculation of the load distributions determined from the strain-gage measurements showed the shaft resistance, even where fully mobilized, to be very small: the beta-coefficient applied in an effective stress analysis was only about 0.13 to 0.14. The evaluations of shaft resistance development showed a maximum shear resistance to occur after a movement of only 3 to 4 mm, after which the response became plastic and strain-softening. The toe resistance was very low because the construction had left soil debris at the bottom of the drilled hole. Ongoing regional settlement leads to concerns about the possibility for the production piles to have a similarly low toe resistance. This would locate the neutral plane of the shorter piles in settling soil and create a downdrag situation for the piled foundation.