Frost Heaving Characteristics And Warning Analysis Of Subgrade In Seasonally Frozen Regions

With the rapid economic development in our country and the proposition of “One Belt and One Road” strategy,it is particularly essential to construct and perfect the high-grade highway network.In addition,roads built in early days have come into the maintenance period one after another,and the maintenance and disaster prevention have also been promoted to an unprecedented important position.As a key part of the roadways,the subgrade and pavement bear the traffic together.And the road performance is directly affected by the subgrade’s strength and stability.However,the subgrade frost heaving due to the distinctive climate conditions in seasonally frozen regions,i.e.,cold winters while hot summers and the large temperature difference through a year,will undoubtedly pose a huge threat to the safe operation of the road.In this thesis,typical roads located in seasonally frozen regions in Heilongjiang Province were taken as examples.Clay,silty clay and medium sand were selected as the research objects.Based on the multivariate linear regression and analytic hierarchy process,a prediction model for frost heaving which considered the moisture content,temperature,soil conditions and the compactness was developed.The weight of each factors on the frost heaving was analyzed,and Arc GIS was employed for the design of a frost heaving warning system to warn and display the subgrade frost heaving.The main research work are as follows:(1)In current specifications about subgrade frost heaving,only the water content and soil conditions were considered,the limitations were analyzed and stated briefly.The moisture content,temperature,soil conditions and the compactness were determined as main factors for frost heaving.Based on the regression analysis to the existing experimental data,a model for calculating the subgrade frost heaving rate in seasonally frozen regions was developed,and the four factors mentioned above were included in this model.(2)The analytic hierarchy process was applied for determining the weights of soil conditions,moisture content,temperature and compaction on subgrade frost heaving.The method improves the defect that it is difficult to determine the weight of each factors on frost heaving due to their different dimensions,and this facilitates its practical application.(3)Based on the measured data provided by Heilongjiang Highway Survey and Design Institute and Heilongjiang Geographic Information Surveying and Mapping Bureau,Arc GIS was employed to establish the precipitation database,subgrade soil temperature database,soil conditions and subgrade compaction database in Heilongjiang Province.The risk of frost heaving disasters in designated sections of Beifu Expressway,Hei Da Expressway and Suibei Expressway were studied,respectively.The frost heaving during the frozen period from November to next February at a depth of 0.75 m and 1.0 m in subgrade were analyzed,and maps for predicting the frost heaving were depicted.