Dear NRAM,

Normally Site will perform the cutting and installation work during day time. For underground analysis, if I were you my analysis will be as below:

Amb. Temp: 55 DegC
T1: 35 DegC
T2: 33 DegC (to simulate Maximum Average Soil Temperature effect on pipe)
T3: -3 DegC (to simulate the Minimum Absolute Ambient Temperature

T3 will give the most conservative value for thermal expansion. You can also design your thrust block base on this temperature thus giving you the conservative value of Axial Force.