Enzyme-induced　carbonate　precipitation　(EICP)　has　emerged　as　a　promising　eco-friendly　biotechnology　for　soil　stabilization.　The　mechanical　properties　of　bio-cemented　sands　are　largely　determined　by　particle　size　characteristics.　However,　the　influencing　mechanism　of　particle　size　characteristics　on　bio-cemented　sands　remains　unclear.　In　this　study,　a　series　of　bio-cemented　sand　column　tests　were　conducted　to　explore　particle　size　effects.　Different　particle　size　(coarse,　medium,　fine)　were　treated　with　different　numbers　of　cycles　(6,　8,　10).　Multiple　key　parameters　of　the　bio-cemented　sands　were　measured,　including　permeability,　unconfined　compressive　strength　(UCS),　calcium　carbonate　content　(CCC),　and　wave　velocity.　The　SEM　imaging　technique　was　employed　to　demonstrate　the　impact　of　sand　particle　size　on　cementation　effect　in　bio-cemented　specimens.　Linear　relationships　were　established　between　wave　velocity,　permeability,　UCS,　and　CCC　with　different　particle　size.　The　results　showed　that　particle　size　significantly　influences　the　CCC,　UCS,　wave　velocity,　and　permeability　of　EICP-treated　sands.　Medium-grained　sands　exhibited　the　highest　UCS　and　wave　velocity　under　EICP　treatment.　This　is　attributed　to　medium　sands　can　achieve　a　good　balance　between　the　efficiency　of　pore-filling　by　calcium　carbonate　crystals　and　the　infiltration　of　the　EICP　solution.　Fine　sands　suffered　from　inhomogeneous　CaCO3　distribution　due　to　the　clogging　of　pores,　which　hindered　the　uniform　penetration　of　the　EICP　solution.　Coarse　sands　showed　limited　cementation　owing　to　oversized　pores,　which　impeded　the　effective　interparticle　bonding　mediated　by　precipitated　calcium　carbonate.　These　findings　establish　particle　size　thresholds　for　EICP　efficacy,　providing　critical　guidelines　for　particle　size　selection　in　field-scale　biocementation　projects.　©　2025