Abstract
The deformation characteristics of the rock mass in the intersection between the Muzhailing highway tunnel and the inclined shaft is a complicated three-dimensional problem. Under the influence of high geostress, large deformation hazards may occur in the surrounding rock. Taking this as the research background, this paper analyzes the deformation mechanism of surrounding rock before and after prestressed anchor cable support through numerical simulation. Then, through theoretical analysis, a new tunnel support method using high prestressed constant resistance and large deformation anchor cable was proposed. The field monitoring results show that the constant resistance and large deformation anchor cable support can well control the deformation of surrounding rock, and the maximum deformation is within 300 mm. At the same time, the constant resistance anchor cable can always maintain a high prestress, which makes the stress of the surrounding rock uniform, and reduces the risk of damage to the steel arch due to local pressure. Moreover, the support method limits the expansion of the plastic zone and improves the overall stability of the surrounding rock.
Highlights
Researchers have done a lot of research on tunnel surrounding rock deformation and support methods
Hoek et al [1] studied the tunnel deformation characteristics under different buried depths. ey considered that rock mass strength and ground stress are the key factors affecting the stability of tunnel surrounding rock
Liu et al [6] considered that the rock mass behavior at the intersection of the adit and the main tunnel is a complex threedimensional problem, and the increase of support load and tunnel deformation may endanger the stability of the tunnel during the construction process
Summary
Muzhailing tunnel is located in the south of Gansu Province, China (Figure 1). It is a part of the Lanzhou–Haikou Expressway. Erefore, large deformation disasters of surrounding rock may occur during tunnel construction. E original tunnel support method was “grouting bolt + steel arch (Figure 4).”. Erefore, the intersection of inclined shaft 3# and the major tunnel was prone to large soft rock deformation disasters. The intersection of the inclined shaft 3# and the major tunnel with the intersecting angle of 90° is selected as the research object to study the control measures of large deformation of surrounding rock at tunnel intersection
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