Proceedings - 13th International Workshop on Micropiles - 2017, Vancouver, BC, Canada, (ISM, DFI, ADSC)
PERFORMANCE OF SOCKETED MICROPILES IN WEAK SOILS
Ahmed A. Al-Obaidi, Ansam A. Al-Karawi
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.
|article #2633; publication #1033 (ISM- 2017)|