| Gongha-Yushu Expressway,referred to as Gongyu Expressway,is an important section of the highway network and the first high-grade highway in permafrost region in China.However,since the trial operation of the project in recent years,the roadbed has been frozen and thawed repeatedly due to the disturbance of solar radiation and long-term load.As a result,the subgrade in the local high temperature unstable permafrost section has been unevenly settled and deformed,which has seriously affected the use of the road.Therefore,we must carry on the detailed investigation and so on to the permafrost road section disease,and through to the own achievement extraction and the summary appraisal,proposed suits the common jade Treatment of highway roadbed deformation in Expressway permafrost region.Firstly,through consulting a large number of documents,this paper comprehensively grasps the influence and general law of roadbed freezing injury.Secondly,the natural geographical characteristics,the characteristics of permafrost temperature,the upper limit of permafrost in Gongyu Expressway permafrost region are found and analyzed.Permafrost thawed intercalation(thawed core)and permafrost characteristics and distribution;Third,starting from the field investigation of roadbed freezing injury and the freezing characteristics of soil,through sorting out the investigation data and its achievements,and synthetically summarizing the disease types of roadbed in Gongyu Expressway permafrost region,Relationship between subgrade Disease and characteristics of Frozen soil,and the influence of roadbed height on the main roadbed diseases in permafrost region;Fourthly,the formation mechanism of roadbed disease,the main influencing factors of roadbed stability in frozen soil area,and the regularity of roadbed disease are analyzed.At the same time,on the basis of mastering the existing main construction technology of old road in Gongyu Expressway permafrost region,The causes of roadbed diseases in permafrost section along Gongyu Expressway are analyzed.Finally,on the basis of the previous analysis,combined with the hot bar method and its technology in permafrost region,the original pavement structure,different types of subgrade subsidence,different types of culvert abutment back subsidence,etc.This paper puts forward some measures and measures to deal with the diseases of Gongyu Expressway roadbed.Policy.The details are as follows:(1)Consulting and referring to a large number of documents,respectively from the frozen soil engineering research,frozen soil frozen rise and thawing research,frozen soil mechanics research,The research on the cooling effect of rock subgrade and the research of roadbed disease and disposal countermeasure in permafrost region have grasped the relevant problems of frozen soil engineering and its disease and disposal countermeasures at home and abroad.The results show that the problem of frozen soil engineering,its disease and prevention has been paid more and more attention in developed and developing countries,especially in our country,and some research and practice results have been obtained.(2)Based on the historical data and investigation data of the relevant areas along the Gongyu Expressway,this paper summarizes the natural geographical situation of Gongyu Expressway permafrost region from three aspects:geographical location,geological and climatic characteristics,etc.The permafrost characteristics of Gongyu Expressway research section are analyzed.The results show that:① Gongyu passes through the permafrost region in the eastern edge of the Qinghai-Tibet Plateau at high speed,the air is thin,the climate is cold,there are more thawing areas along the route,and the permafrost in the transitional zone between thawing area and permafrost region has poor thermal stability and low ability to resist heat disturbance;② The distribution of geotemperature curve of transition type and that of exothermic type along Gongyu expressway is very little,which indicates that the stability of roadbed in Gongyu Expressway permafrost region is poor;③ After the construction of Gongyu Expressway,the upper limit of permafrost is further reduced,and with the increase of permafrost temperature,the upper limit decreases.(3)This paper investigates the diseases of Gongyu expressway permafrost section,and analyzes the main types of roadbed diseases and their relationship with the characteristics of permafrost and the height of roadbed.The results show that:① The disease types of Gongyu Expressway subgrade mainly include subgrade subsidence and culvert abutment back subsidence;② With the decrease of the annual mean ground temperature of permafrost,the rate of subgrade subsidence disease increases first and then decreases,and the rate of subgrade subsidence disease is smaller;③ With the increase of frozen soil ice content,the rate of roadbed subsidence disease increased first and then decreased,and the rate of subsidence disease in multi-ice frozen soil region was the lowest;④ On the contrary,the longitudinal crack disease in low-temperature and sub-stable permafrost regions is higher than that in high-temperature permafrost regions,and the rate of longitudinal cracks in low-ice permafrost regions is almost zero;⑤ Increasing the height of subgrade is beneficial to reduce the subgrade subsidence disease,but it also increases the incidence of longitudinal crack disease and so on.(4)Through analyzing the formation mechanism of roadbed disease in permafrost region and the main influencing factors of roadbed stability in permafrost region,combined with the existing main construction technology of old road in Gongyu Expressway permafrost region,The causes of roadbed disease in TGongyu Expressway permafrost region are discussed.The results show that:① Moisture,temperature of frozen soil,ice content,height of roadbed and non-standard construction are the main causes of roadbed disease in Gongyu Expressway permafrost region;② Direct solar radiation,rainfall and surface water are the main factors affecting roadbed disease;③ The settlement of Gongyu Expressway is mainly caused by the influence of permafrost on the settlement of foundation,which leads to the settlement of subgrade and pavement;④ The causes of subgrade subsidence and cracks in Gongyu Expressway permafrost region can be divided into six categories altogether,such as the change of the cross section of the two ends of the surface pit in the original route direction,the change of the thickness of the block stone,and the uneven thickness of the block rock.This will lead to uneven compaction,differential settlement of subgrade,etc.,as shown in Table 4.1;⑤ The causes of culvert abutment back subsidence are divided into three categories,such as insufficient compaction of culvert abutment back subgrade,post-construction settlement,compaction of roadbed under repeated heavy load during operation,resulting in subgrade subsidence,etc.,see Table 4.2.(5)Based on the above research,combined with the geological conditions of Gongyu Expressway engineering and other related conditions,the treatment methods and countermeasures of roadbed diseases in permafrost region are put forward.The state plans to build the GongHe-Jiegu section into a highway with Qinghai characteristics.However,as a "lifeline" highway passage leading to Yushu area,the subgrade of the local high temperature unstable permafrost section has been unevenly settled and deformed in the three years’ trial operation.However,through this study,not only the treatment methods and countermeasures of roadbed deformation suitable for Gongyu expressway permafrost region are put forward,but also the technical support is provided for the long-term operation of the highway from Gonghe to Yushu on line 214,at the same time,To a certain extent,it has further promoted the realization of economic and social leapfrog development in Tibetan areas.In addition,Qinghai-Tibet Other similar highways in plateau and some permafrost regions at home and abroad provide some references for the prevention and cure of highway subgrade diseases. |
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