The Optimization of Shed-Tunnel Structure in the Confined Environment

Table 1

Different calculation methods and formulas.

Calculation method	Calculation formula
Subgrade code method	, where
Tunnel manual method
Yang Qixin method
Xiang Xin method [10]	, , ,

Note. In the formula of the existing calculation method, denotes the impact force of falling rock, (kN); (Z) denotes the unit resistance of rockfall impact on the buffer layer (kPa); VR denotes the impact velocity (m/s) when rockfall contacts the buffer soil layer; Φ denotes the density of the layer (kN/m³); g denotes the acceleration of gravity (m/s²); and F denotes the cross-sectional area of the equivalent sphere of rockfall (m²).