Study On The Variation Law And Influence Of Ground Temperature In Frozen Soil Cutting Construction Of G332 Line

Permafrost is an unstable geological carrier,and its temperature sensitivity makes engineering construction in permafrost areas face huge problems.However,in the engineering construction of island permafrost in high latitude forest area,the characteristics of poor continuity,small volume and fast degradation of permafrost will aggravate the damage degree of highways in this area.The cutting temperature field research was carried out on the first level highway project of Aku section of G332 National Highway.The K105+560 section was selected for analysis in the study,and the design scheme was a cutting section form of partially excavated permafrost for replacement.In order to reduce the impact of cutting construction on the use of permafrost roadbed,the temperature field of cutting construction process in this section was analyzed.Through the analysis of cutting in the process of excavation and fill in the distribution and evolution law of soil temperature field around,study and grasp changes in the environment may induce range and position of the engineering diseases,and gives reasonable Suggestions,to weaken the cutting on the influence of original ground temperature field of permafrost in the construction process,to improve the use performance of high latitudes forest region of permafrost subgrade has the vital significance.The main research contents of this paper include:(1)According to the geological conditions near the cross section of the island frozen soil,the field temperature monitoring was carried out and the monitoring data collected were analyzed.It was found that the ground temperature distribution along the depth of the natural soil body presented the law of sine(or cosine)roughly,and the ground temperature amplitude of the soil body attenured with the increase of the depth of the soil layer.The annual active layer depth of subgrade is about 2.0m.(2)The numerical model of temperature field calculation was established in the finite element software ABAQUS,and the calculation results were compared with the ground temperature monitoring data to verify the reasonable reliability of the model.(3)By simulating the construction process of permafrost cutting in summer and autumn,the characteristics and trends of temperature field change during the excavation and filling of unprotected permafrost and within 10 years after the completion of filling are analyzed respectively.The simulation results show that:In the process of construction,reasonable working procedure can be adopted to reduce the influence of cutting frozen soil temperature.In the process of analysis,the influencing factors of how to weaken the temperature field are found and the corresponding research is made.(4)The results of autumn construction simulation show that it is best to excavate in autumn and backfill before spring thawing.In this working condition,to protect the temperature field of frozen soil cutting,a 10 cm thick insulation board can be laid on the top of the roadbed,and a15 cm thick insulation board can be laid on the slope of the cutting edge and 3.0m thick non-frost heaving coarse grain soil can be replaced and filled,which can achieve good results.(5)The simulation results of summer construction show that:On the one hand,sunshade,should be taken to control packing temperature below 5 ℃ and speed up the construction progress to prevent too much heat into the frozen soil body,on the other hand on top of the subgrade laid 10 cm thick insulation board,laid on surface of the appraise of slope of 15 cm thick insulation board and 3.0 m thick piece of gravel or frost heaving in coarse particle soil temperature field of frozen soil roadbed filling,The permafrost can enter a new thermal equilibrium state as soon as possible.If possible,the pavement can be carried out after the bottom of the subgrade is stable in the second year to ensure the stability of the subgrade.