Favorable of grouted micropiles for the load transfer in weak sandy soils

¹ Tikrit University, Tikrit, Iraq
² Cihan University, Erbeil, Iraq

^* Corresponding author: dr.obaidi.a.h@tu.edi.iq

Abstract

Micropiles are defined as small diameter piles, implemented as a cast-in-place replacement or injected grout. Generally assumed with a diameter less than 300 mm. The axial capacity of micropiles develops primarily through the bond between gravity grouted (Type A) or post grouted (Type B, C or D) and soil in bonded zone of the micropile. Because of this, micropiles are useful in a variety of applications. Micropiles (Type D) indicate a two-step process of grouting, neat cement grout is placed under gravity head, then, additional grout is injected via a sleeved grout pipe at a specified pressure. In this research, a numerical model was developed to simulate the properties of the micropile (Type D), in addition to micropile (Type A). A general finite element program ABAQUS was selected for the numerical analysis method and for generating the solution. The parameters that affect the load transfer and ultimate capacity of the micropile foundation, which includes micropile length, diameter, grouted length and weak soil type, were investigated. The main results show that the pressure grouting micropile provides better load transfer mechanism as it makes surrounding soil strength to be fully mobilized upon axial loading. Micropiles (Type D)show more favorable in a capacity where the increment range is up to 50% as compared with groundgrouted micropiles (Type A). In addition, the results indicate that the ultimate capacity of micropile increases as the grouted length increases.