Does the surrounding rock of tunnel V first load I-beam or first lead bolt?
In the actual construction, it is difficult to construct the I-shaped steel frame first, and then the construction of the leading small pipe is difficult, which leads to the increase of the outer inclined angle of the leading small pipe, and can not meet the requirements of the external inclination angle in the design or technical guidelines. The problem belongs to design defects and is difficult to solve.
In the individual construction, in order to ensure the external inclination of the small catheter, the drill is drilled at the waist of the I-beam, and the small catheter is passed through the waist of the I-beam, which greatly reduces the function of the i-beam. This method of construction is not allowed by the design. Therefore, the best solution should be to design and replace large numbers of I-beam and allow drilling in the middle of I-beam (after drilling, the I-beam can meet the requirements of design support).
In the technical guidelines for the construction of railway tunnels, article 12.3.1 stipulates that: the initial support shall be applied in time after excavation so as to control the deformation of surrounding rock and prevent collapse.The I-beam steel frame belongs to the initial support range, so the I-beam support should be built first.
