**How to implement new soil models in CRISP using the Material Models Interface**

The Material Models Interface (MMI) was originally developed by Dr Andrew Chan (Birmingham University) to help add new soil models into CRISP more easily.

There are four important stages in CRISP which call the MMI. These are

A. Reading in the material properties (subroutine MSUB1)

B. Initialising in-situ stresses, yield surface and other initial parameters (subroutine MSINSIT)

C. Assembling the stiffness (subroutine FRONTZ for symmetric stiffness or FRONTU for unsymmetric stiffness)

D. Evaluating the stresses and updating various parameters (subroutine UPOUT)

Stages C and D are passed through within an incremental/iterative solution, while stages A and B are called only at the start of the program run.

The MMI is represented by subroutine CRSM2D and is called through each of the stages above with a flag which indicates at which stage the program is.

The flags are as follows:

ISWDP=1 Program is reading properties (stage A above)

ISWDP=5 Program is initialising stresses (stage B above)

ISWDP=3 or 4 Program is assembling stiffness (stage C above).

ISWDP=2 Program is evaluating stresses (stage D above)

ISWD=3 is for symmetric stiffness, ISWD=4 is for unsymmetric stiffness which would require the special Frontal solver in CRISP for unsymmetric stiffness

To implement a new model, you would need to write your code using an IF condition which uses the switches above. You would need to chose a model ID for your new model. A list of existing model IDs is shown below. You would need to avoid using existing model IDs.

For example you would have the following statement added in subroutine CRSM2D:

if(model.eq.159) call mymodel(propd,lprpd,ISWDP,dstre,dstan,dmatx,gausm

,gausm(nstre+1),lpara,ielemu,igaus,nstre,iplstk,km,model)

Then create a separate file which includes your model as follows

Subroutine mymodel(propd,lprpd,iswdp,dstre,dstan,dmatx,ester

,param,lpara,ielemu,ip,nstre,iplstk,km,model)

. COMMON /DEVICE/IWMPO,IWPPS,IWMAS,IWMPE,IWSCRN,IWSMY,IPAUSE

COMMON /FF/AR(40), NCARD, NERR, JERR, IRMPD

!.... input/output variables:

dimension propd(lprpd),estre(nstre),param(lpara)

!.... output variables:

dimension dstre(nstre),dmatx(nstre,nstre)

!.some more dimension statements here for local arrays

.

.

if(ISWD.eq.1) then

.

! Read your material properties here. These would be read from record D in MPD file

.

elseif(ISWD.eq.5) then

.

.initialise your in-situ stress parameters (such as size of yield stress, etc)

.

elseif(ISWD.eq.3) then

.

.

assemble your stiffness (ie D matrix) here

.

.

elseif(ISWD.eq.4) then

.

.evaluate your stresses, check for yield, etc

.

.

endif

The two common blocks above are important as they contain the channel number for reading from the MPD where you would have your material properties (in Record D of the MPD file) as well as other information needed for reading input.

The array *ester* contains the stresses Sigma_x, Sigma_y, Sigma_z, Tau_xy, Tau_yz, Tau_zx

The array *param* contains the pore water pressure in the first component (ie param(1)). Subsequent component contain other stress related parameters such as Yield locus and voids ratio in the case of cam-clay models. The arrays ester and param cover all the integration Gauss points of all the elements. Both of these arrays are equivalent to the old VARINT array in CRISP

Current models in CRISP are:

Model ID | Model Name | |

101 | Elastic Isotropic | |

102 | Elastic, linear variation with depth | |

103 | Elastic Anisotropic | |

121 | Duncan and Chang Hyperbolic model | |

122 | Spare (for Lade model) | |

123 | Gunn small strain model for undrained problems | |

124 | New small strain model for consolidation analysis | |

141 | von Mises | |

142 | Tresca | |

143 | Drucker Prager | |

144 | Mohr Coulomb | |

145 | Mohr Coulomb elastic-rigid plastic with non-associated flow | |

155 | Advanced Mohr Coulomb hardening model with non-associated flow | |

157 | spare | |

161 | Original Cam Clay | |

162 | Modified Cam Clay | |

163 | Schofield Cam Clay | |

164 | Three Surface Kinematic Hardening model (3-SKH) | |

165 | New 3-SKH | |

166 | MIT-E3 (incomplete) | |

181 | Structural model - Bar | |

182 | Structural model - Beam | |

191 | Structural model - Slip |

If you require further assitance please contact Amir