This thirty-third manual in the GEO5 engineering series provides a detailed guide to performing a transient (time-dependent) flow analysis of an earth dam using the Finite Element Method (FEM) in GEO5. The manual focuses on analyzing the evolution of the phreatic line, pore pressures, and water flow velocities over time, following a sudden increase in the water table. Available for download, this manual is essential for geotechnical engineers involved in the analysis and design of earth dams and water-retaining structures where time-dependent seepage is a concern.

Learning Objective:

The goal of this manual is to teach users how to conduct a transient flow analysis using the GEO5 FEM Water Flow program. Users will learn how to set up the initial conditions, apply time-dependent boundary conditions, and analyze the evolution of the phreatic line and related hydraulic variables over time, ensuring that the dam’s design meets safety and performance criteria.

Assignment Description:

In this assignment, users are tasked with analyzing the transient flow through a homogeneous earth dam following a sudden increase in the water table from 2 m to 9 m above the terrain surface. The analysis involves determining the location and shape of the phreatic line at various time intervals: 1 hour, 1 day, 7 days, 3 months, and 1 year after the water table increase. The manual provides step-by-step instructions for setting up the problem, performing the transient analysis, and interpreting the results to determine when steady-state conditions are reached.

Outcome:

Upon completing this assignment, users will be able to accurately model and analyze transient flow through earth dams using GEO5 FEM software. They will gain practical experience in handling time-dependent boundary conditions, evaluating the evolution of hydraulic variables, and ensuring that the dam design accounts for the effects of transient seepage.

Conclusions:

The manual concludes that steady-state conditions are reached approximately 90 days after the sudden increase in the water table. From a practical perspective, steady conditions are nearly achieved after 28 days, as the phreatic line’s location and shape change only marginally beyond this point. These results emphasize the importance of considering transient seepage in the design and safety assessment of earth dams.

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