Mechanics of Fungi-Induced Biocementation in Soils and Rocks

Nature-based engineered processes, such as microbes, enzymes, biopolymers, and most recently fungi, have emerged as effective solutions for ground improvement by altering the mechanical behavior of geomaterials. Among these approaches, fungi have attracted growing interest due to their ability to form interconnected mycelial networks that modify pore structure while remaining metabolically active across diverse environmental conditions; however, the if , how , and why fungi modify the mechanical behavior of geomaterials (soils and rock) underground, from near-surface (soils) to deeper (bedrock and rock masses) strata, remains unexplored. Therefore, this novel study investigates the mechanical response (compressive strength, UCS ) and microstructural characteristics across both rocks and soils modified by fungal-induced biocementation and further explores the potential of engineered fungal biocementation for ground improvement across underground strata of soils and bedrock. Treatment was conducted using the fungus Trichoderma virens under two treatment regimes for 10 days, spore-dominant and nutrient-dominant fungal-inoculation conditions, to assess how spore density or nutrient availability influences fungal growth and geomaterial modification. Next, uniaxial compression tests were conducted on treated and untreated soil and rock specimens, and microstructural analyses were performed to characterize the geomaterial changes due to fungal biocementation within the pore networks. Results show that while fungal biocementation enhanced rock strength ( UCS ), with improvements up to +12% and +15% under spore-dominant and nutrient-dominant conditions, respectively, the soil UCS after treatment exhibited variable and more complex responses. Individual soil specimens showed heterogeneous reinforcement due to oxygen-limited fungal colonization at soil specimen depth, with some specimens showing increased strength and others remaining comparable to controls. Nevertheless, the treated soils exhibited moderate average UCS increases of approximately +6% and +9%. Microstructural analysis revealed continuous mycelial networks within nutrient-dominant rocks and localized hyphal growth under spore-dominant conditions, whereas soils exhibited sparse and discontinuous colonization that limited reinforcement continuity. These findings provide new insight into fungal-enhanced modification of the mechanical properties and structure of geomaterials, highlighting the potential of fungal biocementation as a nature-based strategy for ground improvement from soils in near-surface to the bedrock and deeper rock strata.