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 S_{1}) is exposed to water in the reservoir behind the dam. The foundation soil is impervious, a 1.03-m-wide drainage blanket (surface S_{2}) 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 p_{0} 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: K_{f} = 0.2117 · 10^{−3} m/sec;
Specific weight of the water: R_{0} = 10 kN/m^{3}.
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).
Loads:
The initial hydrostatic pore pressures vary between zero at the water level and a maximum value of 12.19 kN/m^{2} 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 |
p_{0}, Pa |
7735.18 |
8111.5 |
4.8 |
Pore pressure distribution (Abaqus), Pa
Pore pressure distribution (LIRA 10), Pa