Construction method for opening of contact channel of existing shield tunnel

The invention discloses a construction method for an opening of a contact channel of an existing shield tunnel. The construction method comprises the following steps: S1, constructing a temporary beam plate between cross beams of a rail top structure; s2, a double-row profile steel stand column supporting system is constructed; s3, systematic grouting is conducted on the opening area and the influence range of the opening area; s4, duct piece three-pilot-tunnel three-step method construction is conducted; s5, dismantling the temporary support system; and S6, constructing the concealed hole of the contact channel. According to the construction method, the outer side soil body constraint is reserved, the shield tunnel is opened from inside to outside, a three-pilot-hole three-step construction method is adopted for duct piece opening, the structural stress of the non-removed part of an existing duct piece is fully considered in the removing process, the duct piece is rapidly converted to the next procedure afte