Can Soil Arching Be Insensitive to ϕ?

Arching is a common phenomenon that is encountered in backfilling behind retaining walls, trenches, or underground voids in the mine. Marston’s equation has been widely used and modified for computing stresses within backfills, duly accounting for the reduction in stresses due to arching. A critical appraisal of Marston’s equation and its improved forms reveal that the average vertical stress within the soil backfill at any depth is governed by the product of earth pressure coefficient K and wall-backfill frictional coefficient μ, which does not vary significantly with variation in friction angle ϕ of the granular soil backfill. The average normal stress depends on the value assumed for δ/ϕ and whether the lateral earth pressure coefficient has been assumed as Ka, K0, or KKrynine. Therefore, it is not necessary to direct any effort toward determining the friction angle of the backfill precisely. Rather, attention should be paid to the value of δ/ϕ and the appropriate expression for K. Thus, it can be stated that soil arching is almost insensitive to the friction angle ϕ of the backfill.