富水砂卵石地层全方位高压喷射工法+盆形垂直冻结温度场分析

Analysis of the Omni-directional High Pressure Jet+Basin Shaped Vertical Freezing Temperature Field in Water Rich Sandy Pebble Stratum

为研究全方位高压喷射(Metro Jet System,MJS)工法+盆型垂直冻结加固砂卵石地层温度场的发展规律,运用有限元软件建立加固区温度场模型,分析不同季节和MJS水化热对局部冻结区(盆底)及全长冻结区(盆壁)温度发展的影响。结果表明,加固区内土体纵向冻结交圈时间早于横向;距冻结管越近,土体相变时间越早,冻结结束时温度越低,受MJS加固区水化热影响大的土体温度会出现先升后降趋势;全长冻结区受季节影响较大,端部交圈时间夏季比冬季多6~10 d,冻结壁厚度为0.98 m,需采取保温绝热措施;MJS加固区影响下初始地温每升高5.9℃,局部冻结区中心处交圈时间延长1 d,在实际工程中需合理选择冻结开机时间,保证积极冻结期冻结帷幕形成所需厚度。所得结果可指导实际工程施工。

In order to study the development law of temperature field of sand pebble stratum strengthened by omni-directional high pressure jet(Metro Jet System,MJS)+basin vertical freezing,the temperature field model of reinforcement area is established by using finite element software,and the influence of different seasons and MJS hydration heat on the temperature development of local freezing area(basin bottom) and full-length freezing area(basin wall) are analyzed.The results show that the longitudinal freezing intersection time of soil in the reinforcement area is earlier than that in the transverse direction.The closer it is to the freezing pipe,the earlier the phase change time of soil and lower the temperature at the end of freezing,the temperature of soil greatly affected by hydration heat in MJS reinforcement area will rise first and then fall.The full-length freezing area is greatly affected by seasons,the end circle time is 6-10 days more in summer than in winter,and the thickness of the frozen wall is 0.98 m,so thermal insulation measures should be taken.When the initial ground temperature rises by 5.9 ℃ under the influence of MJS reinforcement area,the circle time at the center of local freezing area is extended by 1 day.In practical engineering,the freezing start-up time must be reasonably selected to ensure the thickness required for the formation of freezing period.The results obtained can guide the actual engineering construction.