| The frost heaving of subgrade soil is the main culprit that affects the stability and durability of road engineering in the seasonal frozen soil areas widely distributed in China.In order to prevent the frost heaving disease from the root,it is necessary to study the frost heaving mechanism and development law of subgrade soil.The moisture in the subgrade freezes and migrates under the negative temperature action,which causes the vertical deformation of the soil mass,i.e.frost heaving.This is a coupling process of multiple physical fields,including temperature,moisture and stress,and is affected by external factors,such as the stress state,temperature condition and hydration condition of the soil mass.Therefore,when studying the frost heaving of subgrade soil,it is necessary to pay close attention to the internal temperature distribution,water migration and deformation development law of soil during the freezing process,and explore the relationship between them under the premise of in-depth consideration of the influencing factors such as temperature,stress and hydration conditions.Indoor soil frost heave test is to study the law of soil frost heave a effective means,but so far has been carried out for applying the temperature of the soil frost heave test-stress are simple,how to in-depth research on complex temperature stress under the action of soil frost heave test rule-is yet to be resolved.So by independent development of the soil frost heave test system,carry out the thinking of the cold end temperature and the deviatoric stress and minimum principal stress,filling water conditions,such as four factors affecting soil frost heave test,analyzes the temperature distributions in the process of soil freezing,moisture migration patterns and deformation law of development,and further studied the mechanism of soil frost heave and the law of development.The main achievements are as follows :(1)through data collection,field test,numerical simulation and other technical means,the temperature,humidity and moisture conditions of subgrade in seasonal frozen area are analyzed and summarized.(2)A set of indoor soil frost heaving test system was independently developed,which has the functions of temperature control,axial pressure and confining pressure,water replenishment without pressure and real-time monitoring and collection of temperature,pressure and displacement data,etc.,and the corresponding frost heaving test method was proposed for this system.(3)An indoor soil frost heaving test was carried out considering four influencing factors: cold end temperature,deviant stress,minimum principal stress and water replenishment conditions,and the temperature distribution rule,water migration rule and frost heaving rate development rule of normal frozen soil were analyzed.Found stress state for freezing process of moisture migration and frost heave rate had a great effect on law of development,but for the temperature distribution of almost no effect,and end face temperature and filling water conditions for temperature distribution,moisture migration and development of frost heave effect is significant.(4)By freezing speed and soil frost heave rate to reflect the occurrence mechanism,found that both have good positive correlation and temperature gradient,and are influenced by soil mass stress state and end face temperature;By means of mathematical regression,proposed a saturation is frozen soil frost heave rate forecast formula. |
