Research On Development Mechanism And Control Technique Of Highway Tympanites

Based on research of frozen soil status in quo and analysis of earlier results of highway tympanites nation and abroad, taking advantage of the project"The tympanites mechanism and control technique of highway in YiLi"from the YiLi highway bureau, aiming at large areas of tympanites pingoes on G313 and G218 asphalt highway in YiLi, the thesis makes a thorough study on development mechanism and control technique of highway tympanites from soil features of highway tympanites, tympanites mechanism, material and structure of resisting tympanites by investigation in situ, test and analysis. Main points are as follows:①Research on soil features of highway tympanitesIt is identified that local soil resulting in highway tympanites includes much clay and humus through on-the-spot investigation and test in laboratory. Natural unit weight of the soil is 17～20KN/m3 or so and water content is 18～30%. According to the results of the experiment, the soil becomes saturated when water content is about 25%. The soil strength is determined by density, pore ratio, saturated degree, mineral component, stress history and strain velocity etc. The results show that, with the increasing of water content of soil, the value of cohesion ascends at first and then descends appearing to be a non-linear peak value conic which is connected with existence of matrix suction in unsaturated soil, while the value of angle of internal friction descends and shows non-linear trend towards the steady value gradually.②Research on mechanism of highway tympanitesThe occurrence of highway tympanites is the result of several factors. By studying on the highway tympanites from three aspects : non-linear decay of soil strength by absorbing water, seepage and spread of groundwater and temperature conduction in roadbed, and by using theories of unsaturated soil mechanics, the thesis constructs the decay model of soil strength parameters and the fitting formulas of angle of internal friction and cohesion with water content of soil. Through constructing the physical model of temperature conduction in roadbed of ideal three-phase saturated frozen soil, it studies the directions of temperature conduction in different season and concludes two-dimensional differential equation of unstable heat conducts.The analysis of crack status in quo on tympanites roadbed indicates that development mechanism of highway tympanites includes three aspects: the development mechanism of asphalt pavement cracks, climate tympanites and dynamic tympanites. Because of the influence of temperature and automobile dynamic load, in winter clay lens volume in roadbed expands to the top floor as water is frozen and then makes the pavement ascends, thus in spring soil strength descends as solid state water begins to melt and then the pavement subsides. On the cycle function, it develops into highway tympanites. At the same time, carrying through numerical simulation on temperature field under three kinds of cases by ADINA-T in ADINA software, it makes a sensitive analysis to key points in tympanites roadbed and makes a conclusion that the side close to river valley is easier to produce highway tympanites than the side close to another. This conforms to on-the-spot result.③Research on control technique of highway tympanitesOn the basis of mechanism of highway tympanites and research of model test, the paper constructs the function of highway tympanites, studies the control technique of highway tympanites from two aspects, i.e. material of resisting thick liquid and the structure measure of resisting thick liquid. So long as make clay and particle isolates from water and control water flowing between basic roadbed layer and tympanites layer, the possibility of highway tympanites can be reduced. Therefore draining off water from roadbed effectively is the fundamental goal of controlling highway tympanites. The method of adopting barrel-drain, capillary gravel and streamer fabric together is effective and economic to control highway tympanites. The paper emphasizes that further research is needed constructing test-road to observe on-the-spot to improve design details.