Experimental and numerical study on the earth pressure coefficient in a vertical backfilled opening

Determining lateral earth pressure coefficient (EPC) K is a classic problem in geotechnical engineering. It is a key parameter for estimating the stresses in backfilled openings. For backfilled openings with rigid and immobile walls, some suggested using the Jaky’s at-rest earth pressure coefficient K0 while other suggested taking the Rankine’s active earth pressure coefficient Ka. A single value was proposed for the entire backfilled opening. To better understand the distributions of stresses and K in a backfilled opening, a series of laboratory tests have been conducted. The horizontal and vertical normal stresses at the center and near the wall of the opening were measured. The values of K at the center and near the wall were then calculated with the measured horizontal and vertical normal stresses. The results show that the values of K are close to Ka at the center and close to K0 near the wall. Furthermore, the experimental results show that the horizontal stress is almost the same at the center and near the wall, indicating a uniform distribution from the center to the wall. It can be estimated by analytical solutions using either Ka or K0. The vertical stress is higher near the center than near the wall. Its analytical estimation can only be done by using Ka at the center and K0 near the wall. Finally, the test results were used to calibrate a numerical model of FLAC2D, which was then used to analyze the influence of column size on the stresses and K in the backfilled opening.

Uncontrolled Keywords

• backfill
• laboratory tests
• simultaneous measurement of vertical and horizontal stresses
• earth pressure coefficient
• arching