Micropiles are generally used when there are difficult ground conditions,limited access and low headroom and adjacent structures. Micropiles are recognized as a common remedial option for underpinning structures with foundation problems and common foundation option.
Micropiles are a deep foundation system consisting of small diameter (150 mm to400 mm), drilled, replacement elements consisting of high strength steel and cement grout, that transfer axial loading to the earth via grout-to-ground sidewall friction. Micropiles are typically used in situations where above-ground or below-ground conditions render the use of conventional deep foundations impractical.
Micropiles are classified as per soil conditions by numerous sub-types, each determined by the combination of widely varying drilling and grouting/concreting installation processes. Drilling methods used DTH, Odex, double-head duplex, rotary percussion, continuous grout flushing with bentonite/polymer flushing. Grouting methods include straight tremie injection, dynamic grouting, pressure grouting during casing retraction, and tremie-injection with Concreting.
Total Foundation has designed and constructed more than 80 micropile projects across Mumbai (Maharashtra). The vast majority of these projects included at least one static compression load test to 150% of micropile design loading.
The piles should be installed in such a sequence that the load carrying capacity of previously installed pile is not reduced. The sequence of piling shall be as per working drawings. In a pile group, the sequence of installation of piles normally be from the centre to the periphery of the group or from one side to that the soil is restrained from the flowing out during operations.