Abstract:The complex construction procedure of twin-arc highway tunnels often leads to repeated rock disturbances. Unfavorable geological conditions and improper working procedures may also cause cracking in tunnel linings,thus create difficulties for groundwater inflow prevention and stability. The Sangongqing tunnel on the Yuanjiang—Mohe highway in Yunnan province is taken as a typical example and analyzed for the main factors of cracking of tunnel lining based on the observed monitoring data. It is found that the concrete temperature,non-uniform settlement of the tunnel floor,uneven pressure,and improper construction sequence,are the main causes for the cracks of twin-arc tunnel. Among them,the non-uniform subsidence of the tunnel floor,the uneven pressure,and the improper construction sequence,are the main factors influencing the stability of the twin-arc tunnels. For treatment of cracks of the twin-arc tunnels,according to their different causes,different measures can be adopted:(1) more strict control on the mix proportion of concrete;(2) improved quivering and cure of concrete;(3) using artificially installed deformation joints in the linings;(4) reinforcing the tunnel floor;(5) improved support of connection passes in the separation pillar;(6) supporting the deforming slopes of tunnels to eliminate uneven pressures;(7) grouting (from ground surface or in tunnel) to reinforce the weak surrounding rock.