# FISH function for elastic modulus increment with depth **URL:** \ **Category:** FLAC\ **Tags:** fish\ **Created:** [January 25, 2025, 3:12am UTC](https://forum.itascainternational.com/t/fish-function-for-elastic-modulus-increment-with-depth/1915 "2025-01-25T03:12:21Z")\ **Posts on this page:** 5\ **Page:** 1
**Author:** ![agapanto](https://avatars.discourse-cdn.com/v4/letter/a/f4b2a3/32.png) [@agapanto](https://forum.itascainternational.com/u/agapanto)\ **Post date:** [January 25, 2025, 3:12am UTC](https://forum.itascainternational.com/t/fish-function-for-elastic-modulus-increment-with-depth/1915/1 "2025-01-25T03:12:21Z")
Hi all, I’d like to initialize a non linear distribution of elastic moduli in my FLAC slope model. In particular, I would like to vary the moduli according to the depth from the ground level considering a the top left-hand grid point (i.e., y(1,jgp)) as a reference point. I’m therefore trying to write a fish function called “linear\_mod” but I cannot understand why it’s not working. It seems that the script does not produce any variation of the modules within the group in which I would like this variation to take place. Here is the script: ```auto ;--------------------------------------------------------------------- config creep thermal extra 5 ;------------------------DOMAIN WITH UNIFORM MESH (5x5m) ; I'm generating a domain with negative coordinates because part of the slope ; is below sea level grid 430 106 gen 0 -300 0 230 2150 230 2150 -300 mod el ;------------TOPOGRAPHY gen line 0 230 1330 102 gen line 1330 102 1335 65 gen line 1335 65 2150 0 gen line 0 190 1335 65 ini x 1329.7183 y 102.10892 i 267 j 81 model null region 399,90 ;------------STRATIGRAPHY group sands region 3,101 group clays region 3,95 mod el group sands prop den 2400 bulk = 1000 shear = 500 group sands mod el group clays prop den 2050 bulk = 2000 shear = 100 group clays ;---------------------------------------------------------- def linear_mod loop i (1,izones) loop j (1,jzones) if z_group(i,j) = 'clays' then yc = (y(i,j)+y(i+1,j)+y(i,j+1)+y(i+1,j+1))/4.0 ; Centroid of each zone zc = y(1,jgp) - yc ; Depth of any zone centroid below the surface xc = zc * Gn * K bulk_mod(i,j) = Km * xc - Kq ; Bulk modulus shear_mod(i,j) = Gm * xc - Gq ; Shear modulus endif endloop endloop end set Gn = 2050 K = 0.5 Km = 30 Kq = 50 Gm = 20 Gq = 40 linear_mod ``` I’m using FLAC v.8. Can anyone tell me where I am wrong? Thanks a lot in advance. ---
**Author:** ![jwang](https://avatars.discourse-cdn.com/v4/letter/j/b782af/32.png) [@jwang](https://forum.itascainternational.com/u/jwang)\ **Post date:** [January 27, 2025, 3:16pm UTC](https://forum.itascainternational.com/t/fish-function-for-elastic-modulus-increment-with-depth/1915/2 "2025-01-27T15:16:08Z")
Try using K0=0.5 instead of K=0.5. By default K takes integer number, if a float number is assigned, it will cause truncation of the result.(for example, K=0.5 produces the result K=0) ---
**Author:** ![agapanto](https://avatars.discourse-cdn.com/v4/letter/a/f4b2a3/32.png) [@agapanto](https://forum.itascainternational.com/u/agapanto)\ **Post date:** [January 27, 2025, 5:23pm UTC](https://forum.itascainternational.com/t/fish-function-for-elastic-modulus-increment-with-depth/1915/3 "2025-01-27T17:23:29Z")
Thank you jwang! I had already tried this way but nothing changes. Even if I assign a different name to the variable K (i.e., ‘K0’ or ‘Var’) or a different integer value (i.e., 1 or 2) I always get the same result. What can it depend on? ---
**Author:** ![jwang](https://avatars.discourse-cdn.com/v4/letter/j/b782af/32.png) [@jwang](https://forum.itascainternational.com/u/jwang)\ **Post date:** [January 27, 2025, 5:46pm UTC](https://forum.itascainternational.com/t/fish-function-for-elastic-modulus-increment-with-depth/1915/4 "2025-01-27T17:46:13Z")
There might be some other fish variables in your code that have conflict with other FLAC command/fish names, i suggest add underscore ‘\_’ for each fish variable to avoid any conflict. See the updated code below: ;------------------------DOMAIN WITH UNIFORM MESH (5x5m) ; I’m generating a domain with negative coordinates because part of the slope ; is below sea level config dynamic grid 430 106 gen 0 -300 0 230 2150 230 2150 -300 mod el ;------------TOPOGRAPHY gen line 0 230 1330 102 gen line 1330 102 1335 65 gen line 1335 65 2150 0 gen line 0 190 1335 65 ini x 1329.7183 y 102.10892 i 267 j 81 model null region 399,90 ;------------STRATIGRAPHY group sands region 3,101 group clays region 3,95 mod el group ‘sands’ prop den 2400 bulk = 1000 shear = 500 group ‘sands’ mod el group ‘clays’ prop den 2050 bulk = 2000 shear = 100 group ‘clays’ ;---------------------------------------------------------- def linear\_mod loop i (1,izones) loop j (1,jzones) if z\_group(i,j) = ‘clays’ then \_yc = (y(i,j)+y(i+1,j)+y(i,j+1)+y(i+1,j+1))/4.0 ; Centroid of each zone \_zc = 230 - \_yc ; Depth of any zone centroid below the surface \_xc = \_zc \* \_Gn \* \_K0 bulk\_mod(i,j) = \_Km \* \_xc - \_Kq ; Bulk modulus shear\_mod(i,j) = \_Gm \* \_xc - \_Gq ; Shear modulus endif endloop endloop end set \_Gn = 2050 \_K0 = 0.5 \_Km = 30 \_Kq = 50 \_Gm = 20 \_Gq = 40 linear\_mod ---
**Author:** ![agapanto](https://avatars.discourse-cdn.com/v4/letter/a/f4b2a3/32.png) [@agapanto](https://forum.itascainternational.com/u/agapanto)\ **Post date:** [January 27, 2025, 8:27pm UTC](https://forum.itascainternational.com/t/fish-function-for-elastic-modulus-increment-with-depth/1915/5 "2025-01-27T20:27:15Z")
Thank you so much jwang!!