1 Numerical simulation software LinkFEA Iris Summer Academy 2011 Mengxi WU Institue of Mechanics,CAS 04\09\2011 (WP4)

Numerical simulation software LinkFEA content  What do we want to do  Function of LinkFEA  development of methods  Application  Conclusion and Expectation

1 What do we want to do  Design optimization and safety assessment of reservoir dams, tailing dams  Safety assessment risk management of dike against piping  slope sliding safety analysis under complicated situations Main focus: numerical simulation method research and software developing

4 Dam  Seepage, deformation and stability analysis  Water caused fracture at the first fill of a reservoir

5 Dike Dike and piping Piping mouth

6 Slide range of a slope Slope stability Complicated Seepage situation (rain, water level rise and down of water reservoir ) Slope Cut for construction

2 Function of LinkFEA Finite element method software + safety assessment tool  Focus  field simulation: seepage, stress and deformation, separately or coupled  safety assessment: structure, slope slide  field: hydraulic structure, tailing dam, slope  Function: Pro-processor, simulation, and post-processor

Main Menu Tree-shaped Menu Draw Area Geometry Toolbar View Toolbar Message Box 2.1 Main Interface

2.2 Pro-processor Prepare for the FEM calculation  Geometry, material parameter, calculation type and steps, load and boundary condition  Mesh  Output contents  Independent Pro-processor function for 2-D  Communication with CAD, pro-processor software both for 2-D and 3-D

2.3 Computational modules  Seepage analysis  variably saturated flow (including rain infiltration, evaporation)  Stress-deformation analysis  geo-material and concrete structure  coupled analysis  seepage and effective stress-deformation  consolidation  water caused structure fracture

2.4 post-processor  Visualization of results  Field equal-contour lines and cloud map  Variable vs. time  Structure strength safety  slope slide safety  based on the FEM field effective stresses  Find a critical surface with the minimum safety by optimization techniques

3 development of methods  Innovative simulation method of variably saturated flow through porous media  Method of slope stability analysis

Seepage field can be get through the solution of Richards equation 1. Relation of saturation and pore pressure （ VG equation ）： 2. Relation of relative seepage coefficient and saturation (Mualem equation) Equation of underground flow （1）（1） （2）（2） （3）（3）

 A function  is adopted here to ensure the average value of be the chord value over the unsaturated pressure head domain or, which ensure the whole calculation of the mass matrix be limited to within the un- saturation range, rather than involving saturation area both in temporal and spatial domain Innovative mass balance iteration technique  Piccard iteration method can be used directly

 FEM equation with innovative iteration technique

seepage analysis Measured and Simulated water table positions at different time. 2D rainfall infiltration Transient seepage flow 2D transient drainage test  Mengxi Wu. “A finite-element algorithm for modeling variably saturated flows”. Journal of hydrology.2010

Inner seepage face simulation Procedure Schematic map of the Procedure While unconfined water flow from a fine-grained soils to a coarser soil, A zero pressure face (EO) may appear at the interface of the soils with water flows out of the saturated left side and goes to the unsaturated right side. EO is an inner seepage. The position should be determined and the flux should add to downstream nodes to keep mass balance.

Water table in Classic analysis saturated-only analysisvaried saturated analysis water table isnot accurate in classic saturated-only analysis Convergent problem exists in classic variably saturated analysis

Validity and efficiency of the procedure Pressure head contour Iteration efficiency or zero pressure line

Inner seepage face widely exists in zoned sections Water table of a zoned earth dam Good iteration efficiency Application: 3-d seepage analysis of water power stations. Paper: has sent to Journal of Hydrology for review

Under consideration: different constitutive model of materials complicated seepage case, Consolidation soil strength reduction while saturation rise coupled dynamic affect can be included 3.2 Slope stability analysis Finite element stress-based method Limit equilibrium method

(2) Search for the critical slip surface Factor of safety function Circular sliding surface Any shape sliding surface Optimization techniques steepest descent method, simplex method,… Critical slip surface (1) Calculate a safety factor for a specified slip surface Enumeration method Finite element stress-based method Optimization method

4 Applications  Seepage, stress and deformation of several dams  water caused fracture of dams in the first fill of a reservoir  Slope slide analysis, not yet

24 Seepage analysis of a hydropower station with a 320m high dam Hinge dispose of Shuang-jiang-kou hydropower station

25 Simulated water table of the powerstation (A seepage filler formed at the workshop) reservoir Underground workshop downstream 合作 Some details

26 pore water pressure around the workshop The caves are seepage fillers

Stress-deformation analysis 2-D and 3-D stress-deformation coupled and uncoupled soil-structure interaction concrete cut-off wall contact element Changhe dam (240m high; in Sichuan prov. China)

Settlement displacements (m) Major principal stress (MPa)

Seepage-Stress Coupled analysis Comparison between uncoupled and coupled solution Pore water pressureExcess pore water pressure

Conclusion and Expectation  New methods in variably saturated flow are developed  Software for field simulation of seepage, stress and deformation works well in our practice.  A friendly interfaces is still under developing.  Function of slope stability analysis will be finished in a month  Fully coupled dynamic function capable of both pore water pressure accumulation and dissipation effect will be developed, and safety under dynamic condition will be obtained. Thank you for your attention !