Study On The Differential Settlement Characteristic And Controlling Measure Of Expressway In Mountain Area

During the process of highway construction in mountainous areas, the subgrade is vulnerable to differential settlement after completion of the project, because of the rugged ground, complicated geological structure and high embankment. Excessive differential settlement of the subgrade makes the pavement accrue cracking damage, it impacts on the use of pavement and highway durability. Therefore, it is necessary to study on characteristics and control measure of differential settlement in highway subgrade. The content of this paper are as follows:(1) Settlement pattern and the characteristic analysis of highway subgrade in mountainous areaThe subgrade settlement mechanism and pattern were analysised on the basis of investigating and studing in the domestic and foreign highway project differential settlement disease. A finite element analysis model was established to comput differential settlement under each kind of condition,then the influence to subgrade settlement of many factors was analysised,such as the ground properties of soil, the ground compression module, the depth and nature of fill, the pavement structure and construction time,finaly its sensitivity were analyzed.(2) Study of differential settlement control indicator and standard based on the structure and functionA pavement structure finite element model was established to analyze the additional stress of pavement structure. Highway differential settlement control standard based on the structure and function was proposed by considering anti-pulls the destruction performance, the anti-fatigue failure performance, requests of pavement roughness and draining water.The subgrade differential settlement were classified into many level, it is advantageous for taking the reasonable processing measure to the different rank subsidence, achieves the goal of initiative control to the differential settlement.(3) Differential settlement treatment measures and effect analysis of highway subgrade in mountainous areas.According to the specific engineering, on the basis of differential settlement classification we proposed dynamic measures and geogrid measures to control the differential settlement. For every level of differential settlement we presented corresponding treatment program, and analyzed the effect of various plans in reducing the differential settlement.(4) Experimental study of subgrade differential settlement treatment by geogrid and optimization of settlement treatment programe.Taking depends on the project as a foundation, selected experimented the road section, used many kinds of geogrid plan to carry on settlement processing, embedded settlement observation instrument, unified the theoretical analysis, the field test and the observation, studied differential settlement reducing technology and the effect; Simultaneously unified the different plan of experimental road, used gentrifugalism model experiment to carry on the observation and the contrast analysis of the reinforcement plan using earthwork composition material; and carried on many kinds of plans compared to propose the reasonable technical plan.(5) Test Road Paving and Settlement ObservationAccording to the analysis results of differential settlement treatment, we selected the appropriate section to pave test road and layed a settlement observation plan during construction period and after completion of the project, in order to observe highway settlement changes and the effect of treatment measures, it can provide a basis to promote the application.The study of highway subgrade differential settlement characteristic and control measure in the mountainous area will provide valuable technical reference and basis to scientific research, project design, construction and standard establishment, it has certain economic efficiency and the social significance.