Imrovement of loose sandy soil deposits using micropiles

Abstract

Micropiles are being used today for a variety of applications. The increased awareness of the sound performance of micropiles especially under seismic conditions has led to the widespread use of this technology for ground treatment. Micropiles have been used effectively in many applications of ground improvement to increase the bearing capacity and reduce the settlements particularly in strengthening the existing foundations. This paper describes a case study in which 350 micropiles of 75 mm diameter and 15–20 m long have been used for the improvement of loose sandy soil deposits. The effect of micropile injection on liquefaction remedation and improving of soil stress-displacement behavior are evaluated using the results of Standard Penetration Tests (SPT) and Plate Load Tests (PLT) on a real site before and after micropile installation. The load-displacement responses of micropiles under tensile axial loading are also presented in this paper. The results show that, by using micropiles, the response of loose silty sand soils under surface loading can be significantly improved and the bearing capacity of loose sandy soil increased considerably. Also, the modulus of subgrade reaction of the soil (KS) is increased. The SPT values of soil layers are increased after soil improvement with micropile installation. Therefore, the liquefaction resistances of sandy soil are also improved.