Finite Element Solutions for Geotechnical Engineering

Transcription

1 Release Notes Release Date: January, 2016 Product Ver.: GTSNX 2016 (v1.1) Integrated Solver Optimized for the next generation 64-bit platform Finite Element Solutions for Geotechnical Engineering

2 Enhancements 1. Pre Processing 1.1 Improvement in Check Mesh Topology 1.2 Volume Data Export 1.3 Boundary Table Import / Export 1.4 Improvement in Dynamic Nodal Load 3. Post Processing 3.1 Relative Shear Stress 2.1 CWFS (Cohesion Weakening and Frictional Strengthening) model 2.2 Generalized S-CLAY1S model 2.3 Improvement in Geogrid element 2.4 Improvement in Point Spring element 2.5 Soil Test Wizard Integrated Solver Optimized for the next generation 64-bit platform Finite Element Solutions for Geotechnical Engineering

3 1. Pre Processing 1.1 Improvement in Check Mesh Topology (Mesh > Tools > Check Mesh Topology) The Show Bounding Faces option is to show/hide the boundary faces among free faces. It is useful to check free faces located inside in case of 3D complex model. [Model] [Check on the option] [Check off the option] 3 / 14

4 1. Pre Processing 1.2 Volume Data Export (Static/Slope Analysis, Seepage/Consolidation Analysis > Construction Stage > Volume Data Export) The volume data of 1D/2D/3D elements defined to the construction stage is exported to excel file. This shows the length/area/volume of activated/deactivated set for stages. This doesn t apply for the other element types (point spring, matrix spring, free field, interface, shell interface, pile tip, elastic link, rigid link, user supplied behavior for shell interface, mass). [Volume Data Export] 4 / 14

5 1. Pre Processing 1.3 Boundary Table Import / Export (Static/Slope Analysis, Seepage/Consolidation Analysis, Dynamic Analysis > Boundary > Boundary Table Import / Export) Import the information of boundary conditions from excel file or export them to excel. The sample of table for boundary conditions (BoundaryTable Sample.xlsx) can be found in the installation folder. (ex. C:\Program Files\MIDAS\GTS NX\Sample) Import / Export [Boundary Table Import / Export] 5 / 14

6 1. Pre Processing 1.4 Improvement in Dynamic Nodal Load (Dynamic Analysis > Load > Dynamic Nodal Load) The Velocity and Displacement type for Time History Load Function are added in the Dynamic Nodal Load. [Time History Load Function] 6 / 14

7 2.1 CWFS (Cohesion Weakening and Frictional Strengthening) model (Mesh > Prop./Csys./Func. > Material (Isotropic) > CWFS) When a tunnel or an underground structure is excavated in deep geological environments, the failure process is affected and eventually dominated by stress-induced fractures growing preferentially parallel to the excavation boundary. This fracturing is generally referred to as brittle failure by spalling and slabbing. Continuum models with traditional failure criteria such as Hoek-Brown or Mohr-Coulomb model have not been successful in prediction of the extent and depth of brittle failure. The cohesion weakening and frictional strengthening (CWFS) model is known to predict brittle failure well. [Mobilisation of the strength components in the CWFS model (after Hajiabdolmajid, et al., 2002)] 7 / 14

8 2.1 CWFS (Cohesion Weakening and Frictional Strengthening) model (Mesh > Prop./Csys./Func. > Material (Isotropic) > CWFS) The general conditions (General, Porous and Time Dependent) are same with Mohr-Coulomb model, but the hardening/softening behavior with table using Mohr-Coulomb yield surface can be considered in the nonlinear parameters. [Input parameters of CWFS model] 8 / 14

9 2.2 Generalized S-CLAY1S model (Mesh > Prop./Csys./Func. > Material (Isotropic) > Generalized S-CLAY1S) The Generalized S-CLAY1S model is a development of the earlier S-CLAY1 model and is a rotational hardening elasto-plastic model incorporating the influence of bonding and destructuration. The S-CLAY1 model assumes the triaxial stress state whereas the Generalized S-CLAY1S model considers to the general stress state as well. The Generalized S-CLAY1S model has the complex yield surface and needs additional constitutive parameters for anisotropy and destructuration. [Input parameters of the Generalized SCLAY1S model] [S-CLAY1S yield surfaces in triaxial stress space] 9 / 14

10 2.2 Generalized S-CLAY1S model (Mesh > Prop./Csys./Func. > Material (Isotropic) > Generalized S-CLAY1S) The additional constitutive parameters for anisotropy and destructuration for the S-CLAY1S model cannot all be determined directly from standard laboratory tests. Some parameters have no real physical meaning and can only be obtained by estimation via other soil parameters. Parameter Description Reference value (kn, m) OCR / Pc Over Consolidation Ratio / Pre-overburden pressure When entering both parameters, Pc has the priority of usage POP Pre-Overburden Pressure - λ Compression index Cc / 2.303(1 + e) κ Swelling index Cs / 2.303(1 + e) (Cc / 5 for a rough estimation) M Stress ratio at critical state Triaxial test K0nc K0 for normal consolidation 1-sinφ (< 1) α Initial inclination of the yield curve Anisotropy (estimated via φ ) μ Absolute effectiveness of rotational hardening Anisotropy (typical values: 10/λ ~ 20/λ) β Relative effectiveness of rotational hardening Anisotropy (estimated via φ ) x Initial bonding effect Destructuration a Absolute effectiveness of destructurational hardening Destructuration (typical values: 8~11) b Relative effectiveness of destructurational hardening Destructuration (typical values: 0.2~0.3) [Additional model parameters for the S-CLAY1S model] 10 / 14

11 2.3 Improvement in Geogrid element (Mesh > Prop./Csys./Func. > Material (Orthotropic) > Geogrid) The Geogrid model is an orthotropic material which has tension only behavior and can be only assigned to 1D/2D Geogrid property. 1-direction and 2-direction behave independently each other. It shows tension only nonlinear elastic behavior without the Tensile Strength option, and it shows plastic behavior under load conditions that exceed the tensile strength if this option is selected. In case of 1D Geogrid element, E2, G12 and Tensile Strength 2 are not considered. [Input parameters of the Geogrid model] 11 / 14

12 2.4 Improvement in Point Spring element (Mesh > Prop./Csys./Func. > Property (Other) > Point Spring) The rotation degree of freedom (Krx, Kry, Krz) are added in the nonlinear elastic type. [Input parameters of the Point Spring of Nonlinear Elastic type] 12 / 14

13 2.5 Soil Test Wizard (Static/Slope Analysis > Wizard > Soil Test) In order to perform the best calculation, soil parameters have to be translated into input parameters for the constitutive model used, taking into account the possibilities and limitations of the constitutive model. Most parameters for the constitutive models can be determined directly from standard laboratory tests such as triaxial test and oedometer test. However, due to the complexity of the models, it is recommended to not simply accept the parameters determined from those tests, but to actually model the tests and see if the parameters found actually give a proper representation of the real laboratory test results within the limits of the constitutive models. For this purpose, the Soil Test wizard is available with which in a simple manner laboratory tests can be simulated without the need for making a finite element model. [Triaxial] [Oedometer] [CRS] [DSS] [General] [Soil Test Wizard and test type] 13 / 14

14 3. Post Processing 3.1 Relative Shear Stress (Analysis > Analysis Case > General > Output Control > Output Option) With the Safety Result (Mohr-Coulomb) option, the ratio of the generated stress to the stress at failure for each element can be calculated by Factor of Safety based on the Mohr- Coulomb failure criteria. The Relative Shear Stress (τrel) is calculated by the ratio of the maximum value of shear stress (the Mobilized Shear Strength, τmob) to the maximum value of shear stress for the case where the Mohr s circle is expanded to the failure envelope (τmax). τ τ max τ mob d r σ max σ c σ min σ [Relative Shear Stress] 14 / 14