基于反演参数的多年冻土路基长期温度场预测

利用青藏铁路清水河试验段路基3 a的现场温度场及沉降监测数据,采用模拟退火算法改进的BP神经网络算法反演了冻土路基的热力学参数,并在反演参数的基础上应用有限元法模拟预测了冻土路基在不同保温处理方案下的长期温度场变化情况.结果表明:保温材料路基阴阳坡地的温度场差异小于素填土路基,多年冻土季节性活动层厚度也远低于素填土路基;保温材料路基施工后3 a内仍将发生冻融变形,形成路基病害,但破坏程度低于素填土路基;50 a后,保温材料路基将与青藏高原气候环境达到新的热平衡状态,施工对多年冻土造成的破坏可得到修复,路基稳定性良好,但素填土路基仍存在较厚的季节性活动层,这将会使路基发生严重的变形破坏;保温处理方案可较为有效地减少冻土路基的不均匀沉降.

Long-term temperature field prediction for railway subgrade in permafrost soil zone based on parameter back analysis

Based on 3-year temperature field and settlement monitoring data of the subgrade in Qingshuihe test section on Qinghai-Tibet Railway,the thermodynamic parameters for the subgrade in permafrost soil zone were back analyzed by use of BP neural network improved by annealing simulation method,and the long-term variation of the temperature field in the railway subgrade under different heat insulation schemes was predicted by use of FEM.Some conclusions are drawn as follows: both the thickness of seasonal active layer and the temperature difference between the slope exposed to the sun and the one back faced to the sun of the heat-proof railway subgrade are smaller than those of the plain-filled subgrade; the freeze-thaw deformation of heat-proof subgrade will occur in 3 years after construction,which will lead to the damage to the subgrade,but the damage degree is lower than that of the plain-filled subgrade.Since a new thermal balance will reach between the heat-proof railway subgrade and the climate circumstance of Qinghai-Tibet plateau after 50 years,the damage to permafrost soil zone caused by construction could be recovered,and good stability of the railway subgrade could be realized,but this circumstance doesn't occur in plain-filled railway subgrade,and the thick seasonal active layer will lead to serious deformation of such type of subgrade.Furthermore,the heat-insulation scheme can effectively decrease the non-uniform settlement of the subgrade in permafrost soil zone.