Study On Humidity Of Subgrade And Its Impact On Resilient Modulus In Xinjiang

Xinjiang is located in the northwest of China, which is belongs to arid and semi-arid climatic zones, the annual evaporation is much more than the precipitation, temperature is different between day and night, so special weather conditions led to the existence of complex humidity change of highway in the region, morever, moisture affect the condition of the mechanical properties of roadbed. so it is necessary to expand and deepen research on subgrade's humidity, and its impact on the mechanical properties of roadbed,which to provide theoretical support for highway construction.In this paper, the " humidity (moisture) - matrix suction - resilient modulus" acted as the main line , the specific aspects of research was following:(1) Through a large number of Subgrade humidity investigation in scene and documentation research, analysised of the nature of humidity conditions, more reasonable classification methods of humidity and the range of equilibrium moisture content of Xinjiang highway's roadbed was Proposed ;(2) Based on unsaturated soil mechanics theory, analysised the relevance between matrix suction and the factors, used TMI Index and matrix suction measured at the scene with tonometer to establish matrix suction forecast model affected by climatic factors in arid/semi-arid areas ,get the model parameters;(3) For typical slit-clay subgrade soil, used filter paper method to measure matrix suction, adopted Fredlund and Xing (1994) regression model to derivate soil - water characteristic curve (SWCC) and the model parameters of unsaturated silt-clay soil in Xinjiang region. for sand and gravel soil, drawing on the model parameters calibration method, get its parameters. upon soil - water characteristic curve and the estimated matrix suction model, equilibrium moisture content was forecast .(4) Analysised of resilient modulus of subgrade soil changes with the humidity. One,according to the range of equilibrium moisture content by survey in scene and the forecast model of subgrade humidity, static load bearing plate of resilient modulus was carried, analysised influence of water content and degree of compaction on rebound modulus. another, establised experienced model of static resilient modulus,which is suitable for subgrade soil in Xinjiang region . such as E 0 = K1 W C K2KK3,it is for slit-clay third,adopted adjustment coefficient Fs in NCHRP1-37A report as parameters to characterise the changes of resilient modulus with humidity and temperature , humidity adjustment coefficient Fs of resilient modulus for typical roadbed soil in Xinjiang was brought up.These conclusions may be useful to the further study of the resilient modulus of unsaturated subgrade soils.