冷媒温度和渗流速度对富水砂层冻结温度场的影响规律研究

Law research on the effect of cold media tempreture and seepage velocity on the frozen tempreture field of the water-rich sand strata

摘要:

针对天津地区地铁隧道施工中存在富水砂层等复杂水文地质条件下的冻结问题，通过室内模型试验和数值模拟的结合，研究了冷媒温度和渗流速度对砂土冻结温度场、交圈时间和冻结壁发展的影响。研究结果表明：随着冷媒温度降低，冻结管附近的温度梯度越陡，冻结壁也变得更厚。渗流存在时，渗流水将冷量从上游带到下游，阻碍了冻结壁在上游方向的发展，同时在一定程度上推动了冻结壁在下游方向的发展，导致冻结壁厚度不均匀。最终，冻结壁的形状从静水时的圆形发展为心形。在实际工程中，采用注浆等手段减缓渗流速度，并降低冷媒温度，可缩短交圈时间，确保冻结进程顺利进行。

关键词:冻结法;冻结温度场;冻结壁;冷媒温度;渗流速度;模型试验;数值模拟;富水砂层

Abstract:

In response to the frozen issues in subway tunnel constuction in Tianjin area where complex hydrogeological conditions exist such as water-rich sand strata， the laboratory model experiments and numerical simulations was combined to investigate the effects of cold media tempreture and seepage velocity on the frozen temperature field， closure time， and growth of frozen walls in sandy soil. The research findings indicate that as the cold media tempreture decreases， the temperature gradient near the frozen pipe becomes steeper， and the frozen wall becomes thicker. In the presence of seepage， the seepage water transports cold energy from the upstream to the downstream， which impedes the development of the frozen wall to the upstream direction while promotes it to some extent to the downstream direction， which leads to the uneven thickness of the frozen wall. Ultimately， the shape of the frozen wall changes from circular in still water to heart-shape. In practical engineering， measures such as grouting to reduce the seepage velocity and lower cold media temperature can be used to cut the clolure time and finally ensure a smooth frozen process.

Key words:Freezing method; Freeze temperature field; Frozen wall; Model testing; numerical simulation