 Register   #### TEST CASE 13.1 CALCULATION OF PORE PRESSURE AND PHREATIC SURFACE IN AN EARTH DAM

Reference:

Abaqus 6.11 Benchmarks Manual. – USA, Providence, RI., 2011, – 1731 p. – example 10.1.2. Calculation of phreatic surface in an earth dam.

Problem description:

Using the finite element method, establish the phreatic surface of the homogeneous earth dam, shown in figure below. The upstream face of the dam (surface S1) is exposed to water in the reservoir behind the dam. The foundation soil is impervious, a 1.03-m-wide drainage blanket (surface S2) is used to control seepage through the dam. Find the height of the phreatic surface at the centre of dam (distance between points A and B) and pore pressure p0 at the bottom centre of a dam (at point A).

Problem sketch: Type of created problem:

Spatial design (X, Y, Z, UX, UY, UZ).

Material properties:

Coefficient of permeability: Kf = 0.2117 · 10−3 m/sec;

Specific weight of the water: R0 = 10 kN/m3.

Boundary conditions:

X = Y = Z = UX = UY = UZ = 0 at bottom line of dam. Drainage-only boundary condition were modelled via bar elements of filtration shielding layer (FE type is 178).

The initial hydrostatic pore pressures vary between zero at the water level and a maximum value of 12.19 kN/m2 at the base of the dam.

Model description:

The system is modeled via 456 Physically nonlinear FE of plane strain “soil” (FE type is 284) and via 20 bar elements of filtration shielding layer (FE type is 178). A stage of nonlinear loading with filtration calculation is performed.

Calculation results:

 Target value Abaqus solution LIRA 10 Deviation, % AB, m 0.81 0.83 2.5 p0, Pa 7735.18 8111.5 4.8 Pore pressure distribution (Abaqus), Pa Pore pressure distribution (LIRA 10), Pa