Study On Freezing And Thawing Stability And Influencing Factors Of Highway Slopes In Permafrost Regions Of Naqu,Tibet

Freezing-thawing instability and damage is a common disease of highway slopes in permafrost regions of the plateau.Under the action of long-term reciprocating freezing-thawing cycles,the strength of the slope soil shear parameters decreases and its stability also deteriorates In a century-long highway project,the long-term stability of the highway slope is an important factor to ensure its normal service.This article is based on the first-class highways in the Naqu region of Tibet,and the research results can provide a certain engineering reference and reference significance for the maintenance work of highways in permafrost regions in the later period.In this paper,by simulating the temperature field of highway slope in permafrost region,the thawing depth is obtained during the thawing period.Based on this,the safety coefficient of highway slope under the freezing-thawing cycle is studied.The long-term freezing-thawing cycle of the highway slope safety factor changes was studied,and the stability of the highway slope after 50 years was predicted.The influence of moisture content,roadbed height and other factors on the stability of highway slope during the thawing period was studied,and the corresponding influence law was obtained.The main research contents and results are as follows:1.Use FLAC3D software to simulate the temperature field of the highway slope during the thawing period and freezing period,and obtain the thawing depth in each month of the thawing period.Based on the obtained thawing depth,a model was established to calculate the melting and freezing areas of the slope in sections,and the law of the change of the safety factor of slope stability within a freezing-thawing cycle was obtained,and the most unfavorable month of slope stability was determined.2.The effect of long-term freezing-thawing cycles on the safety factor of slope stability is studied.Based on previous scholars’ research on the influence of shear strength parameters on the slope soil in permafrost regions under long-term freezing-thawing cycles,combined with the actual working conditions in this paper,the road slope under long-term freezing-thawing cycles was modeled and calculated Change in safety factor.The MATLAB software was used to fit the empirical formula of the slope safety factor with the number of freezing-thawing cycles,and the slope stability safety factor of the highway after 50 years was predicted.The results show that the safety factor of highway slopes decreases under the action of long-term freezing-thawing cycles,and there is a possibility of instability and destruction.3.During the thawing process,the influence of the initial moisture content of the roadbed filling and the roadbed height on the stability of the highway slope in permafrost areas was studied.Study the influence of the initial moisture content of subgrade fill on the shear strength parameters of the soil,and calculate the safety factor of the highway slope under different initial moisture contents;by calculating the temperature field of the slope under different subgrade heights,the corresponding melting depth is obtained,and then Calculate the safety factor of the slope under each subgrade height.The relationship between the initial moisture content of the roadbed filling,the roadbed height and the slope safety factor is obtained.The results show that the roadbed height has the greatest impact on the slope safety factor.During the maintenance process,emphasis should be placed on the treatment of the higher roadbed height.