Effectiveness of Micro-Pile Installation Configuration for Increasing the Ultimate Shallow Foundation Bearing Capacity on Soft Clay Soil

Abstract

Soft clay soil is known for low bearing capacity and is prone to soil collapse under shallow foundations through Local Shear Failure. An approach to enhance the load-bearing capacity of such soil is by adopting micro-piles as reinforcement. This study aims to determine the effectiveness of micro piles in strengthening shallow foundations on soft clay soil through laboratory-scale testing. The soft soil used comes from kaolin clay characterized by a cohesion (cu) of 20.692 kN/m 2 and water content (wc) of 58.631%. These properties guided the crafting of test specimens, formed with a diameter (ds) of 0.33m and a height (Hs) of 0.185m. Micropiles were constructed from bamboo with varying numbers (n = 4, 9, 16, 25), lengths (L1= 1.33B, L2= 1.73B, L3= 2.13B), and diameters (d1= 0.03B, d2 = 0.04B, d3= 0.07B). The shallow foundation model with a square shape of BxB (where B=0.075 m), incorporated diverse configurations for the installation of micro-piles (K1, K2, K3). The results showed that more micro-piles (n) led to a higher bearing capacity ratio at a 0.1B reduction (Rqult-mp). The most significant enhancements occurred with the longest micro-piles (L3 = 2.13B), the highest number (n4 = 25), and a diameter of 0.04 B. Additionally, configurations including micro-piles installed beneath and extending up to the foundation's edge (K1 and K2) exhibited significant enhancement in Rq0.1B for identical micro-piles numbers (n). The installation of micro-piles beyond the foundation perimeter did not yield substantial increases in Rq0.1B and, therefore, is not recommended.