Study On Temperature Field Evolution Law Of Artificial Frozen Sand Layer Under Groundwater Seepage

With the wide application of artificial freezing method in coastal urban tunnels,well construction in water-rich and weak strata and subway excavation,engineering problems caused by excessive groundwater seepage occur frequently,which seriously threatens the construction safety of freezing method.At this time,it is very important to study the development law of freezing temperature field under the action of groundwater seepage.Therefore,in this paper,the evolution law of the temperature field of the double-tube freezing under the action of groundwater seepage is studied through the model test.Based on the test results,the theoretical analysis is carried out,and the analytical solution of the steady-state temperature field of the double-tube freezing under the action of groundwater seepage is derived.The correctness of the hydrothermal coupling model is verified by numerical simulation,and the model is further used to optimize the design of the single-coil freezing scheme under the action of groundwater seepage.Based on the similarity criterion,the relevant test parameters are obtained,and the model test of double-tube freezing temperature field considering groundwater seepage is established to explore the temporal and spatial development law of double-tube freezing temperature field under different seepage velocities.The results show that when the seepage velocity is 3m/d,the shapes of the upstream and downstream freezing fronts are different in the steady state,and the downstream freezing front forms a bulge along the flow direction.When the seepage velocity was 6m/d and 9m/d,the downstream bulge was more obvious,and the temperature in the downstream freezing area was significantly lower than that in the upstream freezing area.The expansion rates of the freezing fronts on both sides,downstream and upstream decreased by 49.62%,56.25%,44.64%and 57.4%,65.18%,58.93%,respectively,compared with those without flow velocity.The shape of the freezing front of the upstream and downstream and the middle part is simplified by the piecewise equivalent method,and the analytical solution of the steady-state temperature field of the double-tube freezing under the action of groundwater seepage is derived.Then,the rationality is verified by comparing with the experimental results,and the distribution law of the steady-state temperature field of the double-tube freezing under different seepage velocities is calculated.The accuracy of the mathematical model of hydrothermal coupling is verified by model test.Based on the original single-circle freezing scheme of Libi Mine,a single-circle freezing optimization scheme of "grouting+enhanced freezing" was proposed using COMSOL numerical simulation,and the influence of the grouting area and the arrangement angle of the strengthened freezing pipe on the development of the freezing temperature field was explored.The results show that when the arrangement angle of the grouting area is 30° and the arrangement angle of the reinforced freezing pipe is 15°,the maximum velocity of the loop of the "grouting+reinforced freezing"optimization scheme is 16m/d,which is 45%higher than before optimization;groundwater When the flow velocity is 6m/d?9m/d,the grouting area and the reinforced freezing pipe should be arranged at 20°;when the groundwater velocity is 10 m/d and above,the grouting area should be arranged at 60°,and the reinforced freezing pipe should be selected.20° layout.Figure[35]table[11]reference[80]...