Investigation of the Vertical Earth Pressure on Projecting Conduit and Underground Chamber under a High Embankment

In our country, the theoretical formulae of U. S. S. R and TJ. S. A to calculate vertical earth pressure on projecting conduit and underground chamber under a high embankment are always used. The formulae are numerous and their results have much difference in calculation. After investigating 303 conduits and chambers with higher embankment, the author has found out that 44.5% of total conduits are cracked on axial direction due to a smaller value of earth pressure from calculation. On the other hand, only a few of them are very expensive due to a bigger value of calculation. By analysing the causes of the damage of conduits and investigating the key problems of the various formulae and according to model test in laboratory, under the consideration of the various influential factors of earth pressure the means of decreasing loads based on the conception of differential settlement δof the top of conduit are suggested. Based on both causes with ±δ whether using the means of decreasing loads, the earth pressure equations are derived. In recent years, site tests proved that the formulae are correct. This paper states mainly the results of model test and the derivation of earth pressure. The other parts are described briefly.