Problem with HDPE again. This time undeground.

HDPE line is running u/g as shown in attached sketch and there are valve pits locateed aprox every 300 m . The spec brk is provided just before and after the valve pit. the connection between HDPE and Ductile iron is unresrained.

Should I give thrust blk at pt 1,2,3,4,5 and so on after and before each unrestrained joint or the soil around the pipe will take care of this unrestraied joints as force will act only at point 6 ,that is at change in direction. In that case is thrust blk at only pt 6 sufficient?
or No blk is required? beacuse I think when fluid hit the pt 6 at that time it will try to open the unrestraied joint. But Isn't this force get absorbed in soil while travelling from pt 6 to pt 5.

-krish