Cone Formation at Crown to SPL of a Tunnel (9-10m Depth)

When rock bolts or SFRC are not possible due to machine limitations, alternative measures include:

• Sequential excavation with shorter advances to minimize ground relaxation.

• Forepoling or pipe roofing: To stabilize the crown.

• Grouting: Cement or chemical grouting above the crown to strengthen the ground.

• Use of a thicker primary lining or ribs with lagging to control deformation.

Thanks for the answer.