Insufficient　soil　compressibility　and　high　adhesion　in　earth　pressure　balance　(EPB)　tunneling　can　elevate　cutterhead　thrust　resistance,　clogging　risks,　and　equipment　wear,　significantly　reducing　efficiency　and　safety.　Proper　soil　conditioning　serves　as　an　effective　solution　for　enhancing　tunneling　performance;　however,　its　effectiveness　in　dynamic　tunneling　requires　comprehensive　evaluation　of　compression–adhesion　behavior.　In　this　study,　laboratory　experiments　were　conducted　using　an　improved　push–pull　dynamometer　to　examine　the　effects　of　gravimetric　water　content　(w),　foam　injection　ratio　(FIR),　fines　content　(FC),　and　clay　mineralogy,　focusing　on　clay,　sand,　and　binary　mixture.　Complementary　microstructural　characterization　using　both　optical　microscopy　and　field　emission　scanning　electron　microscopy　provides　mechanistic　understanding　into　the　mechanical　behavior　at　particulate　scales.　The　experimental　results　demonstrate　that　the　generalized　compression　modulus　(Es)　of　clay,　sand,　and　binary　mixture　is　significantly　reduced　by　foam　conditioning.　Quantitative　analysis　reveals　exponential　dependencies　of　Es　on　void　ratio,　FIR,　and　FC.　Kaolinite–rich　mixtures　exhibit　an　exponential　decrease　in　Es　with　increasing　FC,　while　montmorillonite–rich　ones　show　polynomial　dependence　with　a　critical　FC　threshold.　Regarding　normal　adhesion　stress　(NA),　the　effectiveness　of　foam　conditioning　is　found　to　be　dependent　on　both　w　and　FC.　Binary　mixtures　display　an　exponential　correlation　between　NA　and　FC,　whereas　clay　follows　a　rational　function　relationship　between　NA　and　w.　All　measured　NA　peaks　are　consistently　observed　within　the　consistency　index　range　of　0.00–0.50　across　the　full　spectrum　of　tested　FIR　conditions　(0–120　vol%).　This　study　provides　valuable　insights　for　optimizing　soil　conditioning　parameters　in　EPB　shield　tunneling　under　varying　geological　conditions,　while　demonstrating　the　potential　of　in–situ　fine–grained　soils　as　effective　conditioning　agents.　©　2025　Elsevier　Ltd