9427163156

10.1515/sggw-2016-0001

Annals of Warsaw University of Life Sciences - SGGW Land Rcclamation No 48 (1), 2016: 5-12

(Ann. Warsaw Univ. Life Sci. - SGGW, Land Reclam. 48 (1), 2016)

Prediction of free field heave using C_w and C_n indices

KARINA NIEDŹWIEDZICA, KAZIMIERZ GARBULEWSK1, MARZENA LENDO-SIWICKA

Department of Geotechnical Engineering, Warsaw University of Life Sciences - SGGW

Abstract: Prediction offreefiehl heave using C_w and C_H indices. In order to predict free heave in expansive silty clays two methods were applied: CLOD test and double-swelling methods. In both methods C_w and C„ indices are required respec-tively to dctcrminc the soil hcave. The C„. index is determined as a slope of straight linę of shrinkage curve obtained with a use of CLOD test. In casc of double-swelling method two oedometer tests were carricd out to determine C_H index: constant-volume and consolidation-swell oedometer tests. Comparison between heave values calculated using C„. and C„ indcxcs indicatcd slighl differ-ences.

Key words: expansive soil, free field heave, swell-ing

INTRODUCTION

A geotechnical design of buildings and road infrastructurcs in dcvclopcd urban areas is generally regarded as a difficull engineering task, especially when highly expansive soils are distinguished in the ground. Already at the stage of designing the foundation of buildings the sensitiv-ity of ground to changes in water content should be taken into account, particular-ly in the superficial zonę, wherc water content fluctuations are great. Accurate diagnosis of soil heave, prediction of ex-pansive properties of soil (likc values of swelling index or swelling pressurc) and identification of geo-hazards are essen-tial to design of the adcąuate measures to completely eliminale or remarkable reduce a potential of damaging the design building (Garbulewski 2000).

Researches invented several differ-ent proccdures for hcavc prediction with a various degrees of accuracy, howcvcr the majority of previous methods only predict soil heave in terms of “Iow”, “medium”, “high” and “very high” (Van der Mcrwc 1964, Chcn 1988). Rcccntly, two methods for prediction of total heave were proposed: CLOD test method (Miller et al. 1995) and double-swelling method (Nelson et al. 2012). The CLOD method requires the soil samples to be covered by a liquid resin, which allows volume mcasurcmcnts to be conductcd for vari-ous moisture content of the soil. In this method CLOD index C_w is determine as a slope of straight linę of shrinkage curve (Fig. 1) using the following formula: where:

Ae - change of void ratio [-J

A,,, - changc of moisture content [%].

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