| Daga Expressway is a newly built expressway from Dakaimen to Gasa in Xinping County,Yunnan.A wide range of water-sensitive soft rocks such as mudstone and shale with strong disintegration,easy to soften in water and unstable engineering performance are widely distributed along the line.Due to the mountainous and scarce land in Yunnan,the excavation of cuttings occupies the cultivated land or the instability of the valley fill caused problems for the project.To improve the performance of water-sensitive soft rock,make full use of the high fill road foundation section,not only balance fill and excavation,eliminate abandoned,but also to protect the cultivated land and the environment.This will bring huge economic benefits to the project,and it is also fully in line with the concept of sustainable development and environmental protection.Based on the basic performance and road usability of the water-sensitive soft rock,this paper comprehensively and systematically studied the physical,hydraulic and mechanical properties of the water-sensitive soft rock through field investigation and laboratory experiments;Comparative testing and analysis of road performance of the road;established a numerical calculation model of roadbed settlement based on improved soil properties,and analyzed settlement deformation under vehicle load conditions;using a variety of indicators for water-sensitive soft rock and improved filler The road performance was evaluated,and construction measures for water-sensitive soft rock highfill roadbed were proposed.The main results and conclusions are obtained through research:(1)Through experimental research,it was found that the water-sensitive soft rock filler has the typical characteristics of good physical properties and easy softening in water.Based on the actual working conditions of the high-fill road section,the basic properties such as mineral composition,limit water content,particle grading,uniaxial compressive strength characteristics,disintegration characteristics and swelling force characteristics of the water-sensitive soft rock are studied,and accordingly It is proposed to use lime for improvement.(2)The pavement usability of the water-sensitive soft rock ash improved filler was studied,and it was concluded that the water-sensitive soft rock plain soil filler and limeimproved filler have embankment and road bed respectively by controlling the water content and compaction of the filling Build feasibility.Through the experiments of improving the strength characteristics and expansion-shrinkage characteristics of fillers with different lime mixing ratios and water-sensitive soft rocks,it is concluded that the improvement effect of lime on the pavement usability is significant,the best lime mixing ratio is 7%,and the best curing time is 7d.(3)Based on the improved soil properties,a numerical calculation model of roadbed settlement was established,which revealed the settlement law of the high-filled roadbed under the load of vehicles with different ash mixing rates after filling the roadbed.The results show that the settlement of the improved subgrade is significantly reduced compared with the unmodified subgrade,and the settlement is minimized when the ash mixing rate is 7%.The addition of lime can effectively reduce the water sensitivity of the soft rock and improve the stability of the subgrade.(4)Based on the results of tests and numerical simulations,the pavement performance indexes such as water sensitivity,strength characteristics,and expansion and contraction characteristics of water-sensitive soft rock fillers and improved soils are evaluated,and the requirements for the filling of different parts of the roadbed are proposed.The evaluation index system of water-sensitive soft rock and improved fillers proposes the construction measures related to the high-fill subgrade of water-sensitive soft rock,which provides a reference basis for practical engineering. |
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