ABSTRACT:

The paper refers to a field study performed to investigate the effectiveness of static preloading in improving soil conditions against excessive settlement and liquefaction. Resulted settlements were recorded and analysed. Soil conditions before and after preloading were compared through sample taking and performance of penetration tests. Test results were averaged over borings and over depth. These tests showed significant improvement of soil conditions and reduction of the liquefaction potential. Based on the results a preloading time before construction of permanent structures was recommended.

INTRODUCTION

The study described herein was carried out in the context of an engineering design study for a highway, the New Egnatia Road. Purpose of the study was to establish conclusions and draw quantitative results for (a) the degree of soil improvement and (b) the time required for this improvement to be used as guide for treating the problem of ground subsidence under the load of the permanent road embankment. The selection of the method (static preloading) was made on the basis of previous experience and its relatively low cost.

SITE AND PRELOADING STRUCTURES DESCRIPTION

The sites selected for the tests (Site 1 and Site 2) were located on the axis of the designed New Egnatia Road near the town of Lagadas, northeast of Thessaloniki, with almost 0o ground inclination and very near to openflow canals. Water table levels were, on average during the period of the tests, 3.50 m, 4.70 m below ground in the two sites respectively. It should be noted however that these levels are not the highest ones since they were taken in the beginning of winter season. The area is subjected to significant seismic activity. The study involved the construction of two experimental embankments at two different sites in order to monitor the settlement behavior of the ground.

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