# Trying to understand tunnel convergence differences **URL:** \ **Category:** FLAC3D\ **Created:** [April 3, 2023, 3:19pm UTC](https://forum.itascainternational.com/t/trying-to-understand-tunnel-convergence-differences/985 "2023-04-03T15:19:22Z")\ **Posts on this page:** 11\ **Page:** 1
**Author:** ![Carlos\_Mora](https://avatars.discourse-cdn.com/v4/letter/c/3e96dc/32.png) [@Carlos\_Mora](https://forum.itascainternational.com/u/Carlos_Mora)\ **Post date:** [April 3, 2023, 3:19pm UTC](https://forum.itascainternational.com/t/trying-to-understand-tunnel-convergence-differences/985/1 "2023-04-03T15:19:22Z")
Hello, we are trying to understand ground behavior in a tunnel excavation. We have run two models, the only difference is that the first one has soft soil from excavation axe to the surface, below axe is rock mass; the second one everything is soft rock. There is a face and lateral pressure applying on excavation surface. Unexpected, we get more convergences and totally different contour in the model with rock mass. Attached you can find outputs from FLAC3D. ![EffectiveStress_allmat](https://canada1.discourse-cdn.com/flex031/uploads/itasca/original/1X/436af37a5a5036de2a771bf14ab0ce700712a643.jpeg) ![EffectiveStress_only_shoft_soil](https://canada1.discourse-cdn.com/flex031/uploads/itasca/original/1X/4273cf317139d4600190b479438cca16505c2854.jpeg) ![Only_shoft_soil](https://canada1.discourse-cdn.com/flex031/uploads/itasca/original/1X/0c88169960ad223be3e05e0205dfdeeff62cd8f4.png) ![all_materials](https://canada1.discourse-cdn.com/flex031/uploads/itasca/original/1X/eb35d7c312221ef2be5f7740d5a19d26a38500d8.png) Could you help us with the interpretation of this? I can send you the codes if required. Thank you. ---
**Author:** ![msepu](https://avatars.discourse-cdn.com/v4/letter/m/b9e5f3/32.png) [@msepu](https://forum.itascainternational.com/u/msepu)\ **Post date:** [April 4, 2023, 6:42pm UTC](https://forum.itascainternational.com/t/trying-to-understand-tunnel-convergence-differences/985/2 "2023-04-04T18:42:33Z")
Hi Carlos, without looking at your code, i suggest to you check 2 things: 1. Check the density you are using in the material called “Fha-Rellenos\_cohesivos” 2. Run the model without the material called “Fha-Rellenos\_cohesivos” tell me what results from it, Regards ---
**Author:** ![Carlos\_Mora](https://avatars.discourse-cdn.com/v4/letter/c/3e96dc/32.png) [@Carlos\_Mora](https://forum.itascainternational.com/u/Carlos_Mora)\ **Post date:** [April 12, 2023, 12:07pm UTC](https://forum.itascainternational.com/t/trying-to-understand-tunnel-convergence-differences/985/3 "2023-04-12T12:07:32Z")
Thank you for your comments. I´ve changed material from “Fha-Rellenos\_cohesivos” to “Qmk-Lama\_del\_Pacifico” but I still have the same problem. ![image](https://canada1.discourse-cdn.com/flex031/uploads/itasca/original/1X/3f49741953b953c22be0699fa5a419ba5166a620.png) ---
**Author:** ![msepu](https://avatars.discourse-cdn.com/v4/letter/m/b9e5f3/32.png) [@msepu](https://forum.itascainternational.com/u/msepu)\ **Post date:** [April 12, 2023, 6:25pm UTC](https://forum.itascainternational.com/t/trying-to-understand-tunnel-convergence-differences/985/4 "2023-04-12T18:25:03Z")
Wow, that is interesting… what if you take out the forces? just to understand the “pure” response of soil and rock? ---
**Author:** ![msepu](https://avatars.discourse-cdn.com/v4/letter/m/b9e5f3/32.png) [@msepu](https://forum.itascainternational.com/u/msepu)\ **Post date:** [April 12, 2023, 6:30pm UTC](https://forum.itascainternational.com/t/trying-to-understand-tunnel-convergence-differences/985/5 "2023-04-12T18:30:03Z")
and what if you change OV-2-suelo\_residual for QMK - lama del pacifico? ---
**Author:** ![cbarra](https://avatars.discourse-cdn.com/v4/letter/c/f19dbf/32.png) [@cbarra](https://forum.itascainternational.com/u/cbarra)\ **Post date:** [April 12, 2023, 7:43pm UTC](https://forum.itascainternational.com/t/trying-to-understand-tunnel-convergence-differences/985/6 "2023-04-12T19:43:14Z")
could you send your code? ---
**Author:** ![Carlos\_Mora](https://avatars.discourse-cdn.com/v4/letter/c/3e96dc/32.png) [@Carlos\_Mora](https://forum.itascainternational.com/u/Carlos_Mora)\ **Post date:** [April 13, 2023, 11:44am UTC](https://forum.itascainternational.com/t/trying-to-understand-tunnel-convergence-differences/985/7 "2023-04-13T11:44:28Z")
If forces are taken out, high deformation occurs and calculation stops (large strain on). Here are the codes I am using, they are the same except for ground assignment. [Effective\_all\_materials.dat](https://forum.itascainternational.com/uploads/short-url/avYDnbGAXtzbR8IeUVZUiBLt0ei.dat) (8.9 KB) [Effective\_only\_Lama.dat](https://forum.itascainternational.com/uploads/short-url/uCiicx3T2vY3Q1GWpDgEAihTAXb.dat) (6.4 KB) Many thanks. ---
**Author:** ![Carlos\_Mora](https://avatars.discourse-cdn.com/v4/letter/c/3e96dc/32.png) [@Carlos\_Mora](https://forum.itascainternational.com/u/Carlos_Mora)\ **Post date:** [April 13, 2023, 3:10pm UTC](https://forum.itascainternational.com/t/trying-to-understand-tunnel-convergence-differences/985/8 "2023-04-13T15:10:58Z")
Changing OV-2-suelo\_residual for QMK - lama del pacifico, we get same results, there are much more convergences in tunnel crown when part of the model is rock mass as seen in next plots. ![ov2_por_Lama_allmat](https://canada1.discourse-cdn.com/flex031/uploads/itasca/original/1X/2801404eba3e19a0a3e7c59e084f06690ff84434.jpeg) ![ov2_por_Lama_onlyov2](https://canada1.discourse-cdn.com/flex031/uploads/itasca/original/1X/3117519b3c576da256c368fccc595685a2390fda.jpeg) Thank you. ---
**Author:** ![msepu](https://avatars.discourse-cdn.com/v4/letter/m/b9e5f3/32.png) [@msepu](https://forum.itascainternational.com/u/msepu)\ **Post date:** [April 13, 2023, 4:06pm UTC](https://forum.itascainternational.com/t/trying-to-understand-tunnel-convergence-differences/985/9 "2023-04-13T16:06:26Z")
Carlos, i can see less convergence in these new plots… you are having -1.69e-2 maximum displacement (vertical), while in the first ones you got 2.8e-1 (total)… can you unify the color scale? ---
**Author:** ![msepu](https://avatars.discourse-cdn.com/v4/letter/m/b9e5f3/32.png) [@msepu](https://forum.itascainternational.com/u/msepu)\ **Post date:** [April 13, 2023, 4:08pm UTC](https://forum.itascainternational.com/t/trying-to-understand-tunnel-convergence-differences/985/10 "2023-04-13T16:08:30Z")
also, i were looking at your code, and i saw that when you apply multiple materials, you also apply different stress field wich has a direct influence in the deformation process ---
**Author:** ![Carlos\_Mora](https://avatars.discourse-cdn.com/v4/letter/c/3e96dc/32.png) [@Carlos\_Mora](https://forum.itascainternational.com/u/Carlos_Mora)\ **Post date:** [April 13, 2023, 4:14pm UTC](https://forum.itascainternational.com/t/trying-to-understand-tunnel-convergence-differences/985/11 "2023-04-13T16:14:56Z")
Thanks Matias. Sorry for changing plots to Z disp, here you can see plots with the same color scale in total displacements. ![ov2_por_Lama_allmat2](https://canada1.discourse-cdn.com/flex031/uploads/itasca/original/1X/5ee2b8225268de2742a272e8987a60db28442ef4.jpeg) ![ov2_por_Lama_onlyov2](https://canada1.discourse-cdn.com/flex031/uploads/itasca/original/1X/4ea33edeb0a9824fc934134271f30a66225625bb.jpeg)