In　the　context　of　subway　station　foundation　pit　engineering,　the　terminal　joints　of　the　internal　support　system　are　crucial　for　overall　bearing　capacity.　Traditional　joint　designs　exhibit　shortcomings　in　terms　of　stiffness,　integrity,　and　stress　distribution.　This　paper　introduces　a　novel　internal　support　joint　known　as　the　Mold-Bag　Concrete　Clamped　Joint　(MCCJ),　discussing　its　structural　features　and　operational　mechanism.　To　quantify　the　load-bearing　and　load-retention　capabilities　of　MCCJ,　two　MCCJ　specimens　were　fabricated　and　subjected　to　axial　compression　tests　and　dwell　tests,　the　failure　modes,　load-displacement,　load-strain,　and　axial　force-time　curves　were　analyzed.　Furthermore,　the　finite　element　analysis　was　employed　to　verify　the　test　results,　leading　to　computational　studies　on　40　MCCJ　models　with　varying　parameters.　Based　on　the　structural　attributes　and　load-bearing　behavior　of　MCCJ,　the　calculated　formulas　for　the　yield　load　and　compressive　stiffness　under　axial　compression　were　developed　and　refined　through　numerical　simulation.　Finally,　the　calculated　formula　results　were　compared　with　simulation　and　experimental　datas,　confirming　their　accuracy　and　reliability　in　predicting　the　load-bearing　performance　of　MCCJ.　©　2025　Institution　of　Structural　Engineers