Micropiles are small diameter, cast-in-place replacement piles which are ideal for
building foundations on sites with poor ground conditions and they are well suited for
foundation underpinning, and increasing the capacity of existing foundations via
transfer the loads from weaker strata to strong deeper strata.
Building No.12 – Internal Dormitories for Women at Tikrit University are two
stories, constructed as bearing wall system. After a period of operation, several
aggressive cracks had been found in the superstructure due to excessive foundation
settlement. The borings for site investigation and geophysical exploration revealed that
the building was constructed on weak gypseous Silty Sand layer extended more than
6m. This layer exhibited a large collapse when it exposed to water.
In this research, the performance of micropiles grouted by gravity Type (A)
embedded in weak soils and socketed in the strong soil are investigated. The
micropiles are simulated in ABAQUS/CAE program with different length and diameters
ranged from 5m to 20m and 0.1m to 0.3m respectively, embedded in weak soil and
penetrate the strong layer with proportions of their total length. The parameters that
affect the ultimate capacity of the micropile foundation represented by the effect of
socketed lengths in dense soil were investigated. The main results show that for long
micropiles Type A socketed in dense layer, the load-settlement curve has no vertical
tangent and there is no defend failure load and its ultimate capacity ratio increased
with (1.029) to (1.487) as compare with these resting on dense soil. It has been found
that micropiles with diameter 0.2m socketed 20% of their length in dense soil distance
2m c/c spacing is recommended for rehabilitation which can transfer the building load
to the strong layer. Also, these micropiles can densify the surrounded soil.
Subjects: socketed, grouted, micropiles
Author: Ahmed A. Al-Obaidi, Ansam A. Al-Karawi
Publisher: ISM, DFI, ADSC