Model tests and numerical simulations of earth pressure for unloading structures of high fill open cut tunnel

The influence laws of earth pressure and soil displacement for different unloading structures of high fill loess open cut tunnel with the increase of filling height are studied through the model tests. The results show that the friction resistance of slope, the soil arch effect of low compacted soil and the geogrid effect can reduce the earth pressure of the open cut tunnel, and the unloading rate of low compacted soil and geogrid is the largest. Under different unloading structures, the distribution law of earth pressure on the top of the open cut tunnel is also different. Within the scope of 1 times the width, the earth pressures of SY0 and SY1 are approximately in trapezoidal distribution. Within the scope of over 1 times the width, the earth pressures keep unchanged, and are approximately in uniform distribution. The earth pressures are basically consistent in the scope of the central axis to 0.75 times the width, and they increase at first and decrease later within the scope of over 0.75 times the width. Based on the numerical simulation analysis, the test and numerical results are basically identical. Finally, the formation mechanism of soil arch effect is discussed so as to provide a scientific evidence for further researches on the unloading technology of the earth pressure of the high fill open cut tunnel.