Because the earth pressure above tunnel crown was assumed uniform and the effect of
particle flow of sand and ground loss were not considered, Terzaghi method generally
produces discrepancies from model tests and field observations. To overcome this
deficiency, the flow of sand particles above a tunnel was investigated firstly to define the
shape and size of loosening zone by following the gravity flow principles. Then, by assuming
non-uniform distribution of earth pressure and incorporating the factor of ground loss, a …