Abstract
Due to climate warming and large-scale engineering activities, the embankment engineering risk in the permafrost and seasonally frozen regions caused by water content change in the soil has become more and more serious. To study the moisture migration law in the embankment under the vehicle load action and periodic variation of temperature, a series of temperature-controlled model tests under the dynamic load condition were carried out, the dynamic load was imposed by an air hammer connecting a vibration plate, which was installed on the top surface of the soil, and the variation law of the temperature and moisture fields in the model was analyzed. The test results show that the moisture field in the soil sample changes obviously with the increasing freeze-thaw cycles under the no-load condition, especially after nine freeze-thaw cycles, two moisture accumulation areas appear in the range of 8–15 cm from the soil surface; the dynamic load has an inhibitory effect on the moisture migration within 5 cm below the vibration plate and has a promoting effect on the range of 10–30 cm below the vibration plate. With the increase in the number of freeze-thaw cycles, three high-water content areas are gradually formed and approximately uniformly distributed within the 10–25 cm depth range of the soil, which has an important impact on the stability of the soil. The water content of the moisture accumulation areas during freezing is greater than that during thawing under the no-load condition, while the water content of the moisture accumulation areas during freezing is less than that during thawing under dynamic load. The research results can provide references for the embankment design and disease treatment in cold regions.
Highlights
In cold regions, the land surface will undergo repeated freezing and thawing due to periodic fluctuations in surface temperature [1]
Soil Moisture sensor Thermal sensor seen that the maximum temperature in the soil sample is about 16°C, which occurs at the upper surface of the soil sample and a location of 10 cm from the upper surface of the soil during the freeze-thaw process, and the maximum depth of frost penetration is about 6.2 cm during the 1st freezethaw cycle and about 8 cm after nine freeze-thaw cycles. is indicates that the cold capacity gradually accumulates in the soil sample
At the moment of the highest ambient temperature during freeze-thaw cycles, in the range of 0–20 cm from the soil surface, the temperature of the soil sample under the vibration base plate is greater than that on both sides of the plate at the same depth, which is caused by the larger thermal conductivity of the vibration plate, and the temperature gap gradually increases with the increase in the number of freeze-thaw cycles (Figure 9). e reasons are that, on the one hand, the dynamic load accelerates the migration of moisture which further affects the distribution of the temperature field; on the other hand, the thermal conductivity of the vibration base plate is larger than soil and affects the heat transfer and accumulation of the soil sample
Summary
The land surface will undergo repeated freezing and thawing due to periodic fluctuations in surface temperature [1]. E results showed that the moisture migration in frozen soil is related to the soil-water potential gradient, which is influenced by many parameters, such as physical and mechanical properties of the soil, test boundary conditions, freezing speed, temperature gradient, and other parameters. E results show that the external load has a great influence on the driving force of moisture migration, which causes changes in the amount of moisture migration, migration rate, and frost heaving ratio. E results showed that different freezing and thawing temperatures significantly affect the moisture migration in the soil samples, and the higher the freezing temperature of the top board of the test cases, the more the water content accumulation at the water accumulation layer. The current research on moisture migration is mainly focused on model tests and small soil sample tests under unloaded conditions and few reports studies have been reported the influence of dynamic loads and freeze-thaw cycles on soil moisture migration based on large model tests. erefore, this article carries out model tests under dynamic load and freeze-thaw cycles, measures the temperature and moisture in the soil during the tests, and analyses the moisture migration mechanism under dynamic loads. e research results can provide a scientific basis for the design, construction, and disease treatment of the embankment projects in seasonally frozen regions
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