Enhancing Pile Interface Shear Resistance in Loose Sand Using Tofu Wastewater Biocementation

Abstract

Loose sandy soils exhibit low relative Density and internal friction angle, rendering them unsuitable for stable foundation support. Meanwhile, tofu wastewater (TW), a byproduct of household-scale tofu industries in Kediri, Indonesia, contains natural urease enzymes and active organic compounds with potential as eco-friendly biocementation agents. This study aims to evaluate the effect of TW treatment on the enhancement of skin resistance (Q_s) and interface shear resistance (δ) of pile foundations in loose sand. The methodology involved TW treatment for 30 days, axial load testing, and analysis based on Meyerhof’s bearing capacity theory supported by ANOVA validation. The results indicate a substantial increase in Q_s of 553%, rising from 0.0103 kN to 0.0675 kN after TW treatment. The δ/φ coefficient reached 2.98 at a depth of 0.015 m (D/B=1.5), representing a 156% improvement over untreated sand and indicating enhanced mobilization of pile–soil interface friction. ANOVA confirmed the improvement was statistically significant (p<0.05). A correction factor δ of 2.27–2.56 was proposed to represent TW contribution to interface strength. Utilizing tofu wastewater enhances load transfer efficiency in loose sandy soils. It offers a sustainable alternative, while the corrected δ coefficient refines classical bearing capacity models under biologically improved soil–structure interaction conditions.

Keywords: Biocementation; Interface Shear Resistance; Loose Sandy; Skin Resistance; Soil Improvement; Tofu Wastewater (TW).