Thermal analysis in UDEC to observe induced stress

Hello everyone,
I am new to Thermal Analysis at UDEC. I want to achieve thermal-induced stresses due to changes in temperature of a voronoi model.
This is the following code I used:

block config thermal
block tolerance corner-round-length 1E-2
block tolerance minimum-edge-length 2E-2
block create polygon 0,0 0,10 10,10 10,0
block cut vor edge-maximum 1.0 round 0.01
block joint-delete
block zone gen edge 1.0
group zone ‘User:ID109’
block zone cmodel assign elastic density 500 bulk = 1E6 shear = 2E6 cond 20 specheat 0.2 range group ‘User:ID109’
block contact group ‘Rock:Sandstone’
block contact cmodel assign area stiffness-shear 1E9 stiffness-normal 1E10 friction 30 cohesion 1E5 dilation 5 range group ‘Rock:Sandstone’
; new contact default
set jcondf joint model area stiffness-shear=1E9 stiffness-normal=1E10 friction=30 cohesion=1E5 dilation=5

block gridpoint init temperature 30.0
block gridpoint thermal-apply temperature 100.0 range pos-x 9.9398,10.1562 pos-y -0.2963,10.1562
block thermal cycle
block thermal cycle age 5.0

This is the error I get:
failure in coef2

Can somebody please convey the correct procedure to perform this thermal analysis?

Thanking You

The thermal logic works by transferring heat between blocks at the contacts. This only works at edge to corner or edge to edge contacts. For corner to corner contacts, UDEC cannot calculate a thermal conductivity coefficient because there is no surface area associated with the contact. UDEC will issue a message when this occurs. A little annoying.
I suspect that the thermal logic will not work well for a granular model. The shapes and zoning of the grains dictate the thermal transfer locations and those will be very irregular.
Also, there is no heat transfer across gaps. So it the model is loaded such that cracking occurs and contacts are lost, there will be no heat transferred at those points.

Thank you for the reply
Please have a look at these links once:

The above papers constitute a voronoi model and performed thermal analysis on them and have generated thermal cracks. I actually want a similar kind of results in my analysis.