Accurate　modeling　of　soil　deformation　depends　on　the　consideration　of　both　frost　heave　deformation　in　the　frozen　zone　and　consolidation　deformation　in　the　unfrozen　zone.　Pore　water　pressure　investigations　are　important　for　revealing　these　two　deformation　behaviors.　Herein,　we　aim　to　reveal　the　consolidation　process　by　measuring　and　analyzing　changes　in　pore　water　pressure　in　the　unfrozen　zone.　Using　a　custom-made　pore　water　pressure　gauge,　we　performed　a　series　of　real-time　pore　water　pressure　measurements　in　the　unfrozen　zone　of　silty　clay　and　sandy　soil　samples　that　were　exposed　to　closed　and　open　freezing　systems.　The　results　show　that　the　pore　water　pressure　in　the　unfrozen　zone　generally　increases　at　first　and　then　decreases.　The　temperature　changes　in　the　unfrozen　zone　have　no　significant　influence　on　the　changes　in　pore　water　pressure,　and　the　variations　of　the　pore　water　pressure　are　mainly　controlled　by　the　stress　and　hydraulic　boundary　(changes　in　pore　water　pressure)　conditions　at　the　freezing　front.　Furthermore,　changes　in　the　pore　water　pressure　are　affected　by　several　parameters,　including　soil　type,　water　supply　condition,　initial　moisture　content,　measured　soil　layer　depth,　and　hydraulic　conductivity.　Soil　consolidation　is　mainly　caused　by　change　in　effective　stress,　which　results　from　increase　in　total　stress　or　decrease　in　pore　pressure.　Based　on　the　observed　pore　water　pressure　variations　and　its　numerical　simulations,　we　propose　that　consolidation　in　the　unfrozen　zone　during　soil　freezing　includes　compression-induced　consolidation,　which　results　from　an　increase　in　frost　heaving　stress,　and　vacuum　induced　consolidation,　which　results　from　a　decrease　in　pore　water　pressure.　Each　consolidation　pattern　plays　an　important　role　in　the　different　stages　of　soil　freezing.　Compression-induced　consolidation　primarily　occurs　during　the　early　stage　of　soil　freezing,　while　vacuum-induced　consolidation　mainly　occurs　during　the　later　stage　of　soil　freezing.　(C)　2016　Elsevier　B.V.　All　rights　reserved.