Sputnik Iran did not report this. Why thye report on their Turkish version and not in Persian?

But why? Is it known?

I think it is NATM gone wrong.

Hi

In tunnel excavation, the most important danger is the fall of a wedge in the upstream of the excavated area.
Most transformation in the tunnel occur in the early hours and days after drilling (excavation)
Probably too much, combin li-sh & sh-cal together Q (
Exposed to air) Their common features are low stability، High water absorption and low resistance to erosion and weathering on the one hand
On the other hand، The above factors along with two faults and lack of wedge removal and failure to strengthen the tunnel portal by using one or more layers of shotcrete (depending on the need) along with wire and even using rock bolt and slurry injection have caused unavoidable fall during tunnel excavation.
In large sections and in drilling method (NATM), the use of forepoling method as an umbrella with an angle of about 10 degrees is a popular and very suitable method in tunneling.
This is my personal opinion.
In the end, i excuse me and apologize for having poor English.