PROTECTION OF SHIELD STARTING HOLE

PURPOSE:To protect the shield starting hole by in advance forming a ground foundation improvement body in the ground at the back of a starting wall face drilling a plurality of anchor bolts reaching the ground foundation improvement body through the starting wall face to connect the starting wall face to the ground improvement body. CONSTITUTION:A starting hole 3 consists of a starting wall face 4 which is a thin part of a side wall 1, a mine support 5 which is a removable H-shaped steel reinforcing this starting wall face 4 from the inside thereof, and a ground improving body 6 which is located at the back side of the starting wall face 4 and is larger than said face 4. The ground improvement body 6 is prepared as a columnar compact body from mixture of both lean-mix mortar and ground sediment, for example as the body 6 is located in contact with the back face of the starting wallface 4. A plurality of anchor bolts 7 are driven at the starting hole 3 of a mold excavator 2 from the clearance of the mine support 5, passes through the starting wall face 4 and reaches the ground improvement body 6. The opposing ends of each of the anchor bolts 7 are fixed to the starting wall face 4 and the ground improvement body 6, respectively.