Model test study of frost heaving pressures in tunnels excavated in fractured rock mass in cold regions

Based on the similarity theory, taking the horseshoe, city-gate and round linings as examples, the value and distribution regularities of normal frost heaving pressures （hereinafter as frost heaving pressures） in tunnels excavated in fractured rock mass in cold regions under different constraints and freezing depths were studied by a test model. It was found that the larger the frozen depth, the larger the frost heaving pressure, and the stronger the top constraint, the larger the frost heaving pressure. For the horseshoe lining and city-gate lining, the top constraint has a greater effect on the frost heaving pressures on the arch and the inverted arch. For the round lining, the influences of the top constraint on the frost heaving pressure in all linings are almost the same. The frost heaving pressure is maximum on the city-gate lining and minimal on the round lining. The largest frost heaving pressure all occur near the foot of the inverted arch for the three kinds of lining. Thus, the test data basically coincide with the observed in situ data.

The effect of confining boundary on soil deformation in one dimensional frost heave tests and the theoretical volume correction

Frost heave is one of the major complications in highway construction in cold regions. Laboratory experiments are im- portant in the study frost heave behavior of soils, and one-dimensional frost heave experiments are the easiest way to evaluate the soil frost heave potential. In a one dimensional frost heave test, the deformation in axial direction is non-uniform because of the confining effect of the cutting ring＇s sidewall. If the effect of confining boundary on soil de- formation is ignored, the deformation will be over-estimated. In this paper, the effect of confining boundary on soil de- formation is theoretically studied and a volume correction method is developed and applied to the frost heave test of a sulfite saline soil. Test results demonstrate that the sulfite saline soil will expand to a loose, low-density state after several freezing-thawing cycles under the condition of zero axial stress.

Macroscopic Frost Heave Model Based on Segregation Potential Theory

A macroscopic frost heave model with more clear parameters was established. Based on a porosity rate frost heave model and segregation potential theory, a porosity rate function was deduced and introduced into the stress-strain relationship. Numerical simulation was conducted and verified by frost heave tests. Results show that the porosity rate within the frozen fringe is proportional to the square of temperature gradient and current porosity, and is also proportional to the exponential function of applied pressure. The relative errors between the calculated and measured results of frost depth and frost heave are within 3% and 15% respectively, demonstrating that the temperature gradient, applied pressure and current porosity are the main influencing factors, while temperature is just the constraint of frozen fringe. The improved model have meaningful and accessible parameters, which can be used in engineering with good accuracy.