渗流作用下砂层冻结模型试验研究

Model Test Study on Freezing of Sand Layer under Seepage Condition

在地下水渗流地层进行冻结法施工时极易发生工程事故,为评估冻结效果,确保施工安全,应对冻结壁发展规律及其厚度计算进行深入研究。基于相似准则,通过室内模型试验,研究静水和不同渗流速度下饱和砂层冻结温度场分布规律,同时基于巴霍尔金温度场解析解,提出适用于渗流条件下冻结壁厚度的计算方法。研究表明:静水冻结时,饱和砂层冻结温度场呈对称分布,冻结壁交圈后温度场和巴霍尔金温度场解析解基本一致;渗流冻结时,冻结壁交圈时间变长,交圈位置偏向下游,上下游温度场差异性明显,渗流速度介于2.3~2.5 m/d时,冻结壁难以交圈;所提出的渗流条件下冻结壁厚度公式计算结果和模型试验实测值较为吻合。研究结果对渗流地层冻结规律认识及冻结效果评估具有指导意义。

Engineering accidents are likely to occur during freezing construction in groundwater seepage formations.To evaluate freezing effect and ensure construction safety,the development law of frozen wall and its thickness calculation should be studied deeply.In this paper,the distribution of freezing temperature field in saturated sand layer subjected to static water and different seepage velocity is studied by model test based on similarity criterion.Meanwhile,a formula for calculating the thickness of the frozen wall under seepage condition is proposed based on Bakholdin’s analytic solution of temperature field.The results show that under static water condition,the freezing temperature field of the saturated sand layer develops symmetrically,the frozen wall intersects at the intersection of the axial plane and the interface,and the freezing temperature field are basically same as Bakholdin’s analytic solution of temperature field.Under seepage freezing condition,intersection time of the frozen wall becomes longer,the intersection position is biased to downstream,and the upstream freezing temperature field is obviously different from the downstream freezing temperature field;the frozen wall is difficult to intersect when the seepage velocity is 2.3~2.5 m/d.The results of the calculation formula for freezing wall thickness under seepage flow condition are in good agreement with the measured values of the model test.The research results have guiding significance to understand the seepage formation freezing law and evaluate the freezing effect.