It is a challenge to deal with karst in the construction of large cross-section tunnel. Under the background of Shuangbei Highway Tunnel, a new kind of grouting technology is introduced. According to hydrogeology, field tests are carried out to select grouting materials and proportion of mixture. Combined with the project practice, grouting construction technology is discussed such as grouting equipments, grouting parameters, operation technique, grouting ending standards. It has been proved that the technology is effective in tunnel construction.

Tongluoshan expressway tunnel passes through coal mined out area. It is an extra-long expressway tunnel with high-gas, so construction ventilation is the key in this project. Combined with the theoretical calculation and the actual situation of Tongluoshan Tunnel, the forced ventilation is taken as the major way of construction ventilation. Based on the calculation of required airflow, gas distribution in work area and calculation of air duct resistance and tunnel resistance, the configuration of fans is optimized, thus the construction ventilation of each section have been determined.

Tianpingzhai Tunnel on Dazhou-Wanzhou Expressway passes through the mined-out area, the spatial position of the goaf changes constantly comparing to the tunnel during excavation, and broken rock mass of the caving zone is most likely to collapse, which affects construction safety in return. Two dimensional computation models were built by using finite differential software FLAC to simulate excavation process when the coal-mined area is right above or below the tunnel. In 2D models, goaf strata were regarded as horizontal, and buried depth and coal thickness were limited to 300 meters and 0.5 meter respectively. The displacement around the tunnel, forces of primary lining, axial force of bolts and plastic zone of surrounding rock have been analyzed under these circumstances that the distances between tunnel and goaf are 1m, 6m and 12m. According to the results, when the distance between goaf and tunnel is less than 12 meters,underlying goaf has greater impact on the displacement around the tunnel and average axial force of bolts than overlying goaf, as well as the size of plastic zone of surrounding rock. Its strongly suggested to avoid underlying goaf if the tunnel have to pass through the mined-out area.

Water rush and mud rush are two major problems during the process of tunnel construction, which can lead to big troubles. Advanced geological prediction should be carried out to prevent the emergency of water rush and mud rush during the construction in the karst and water-rich areas. Infrared detection technology is a way to detect the hidden water. In this paper, basic principles of model HY-304 infrared detection meter are described, and it is applied in Shuangbei Tunnel. By analyzing the predicted results and comparing it with the situation of excavation, the instrument is feasible as to water rush in karst areas and infrared detection technology has a great opportunity to be applied in the tunnel engineering under complex geological conditions.

Guandoushan tunnel in the Yibin - Luzhou expressway passes through fault fracture zone at the entrance. Structure internal force are complex during or after the construction. It challenges the safety during construction and operation. Plane finite element model was used to calculate internal force of primary support in the cases of different buried depths and three dimensional finite element model was applied to calculate stress distribution of primary support and secondary lining of the tunnel through fault fracture zone. The results indicate: with the increasing of buried depth, the loads acting on the structure will increase. It leads to uneven stress distribution in longitudinal direction, especially in the border of fault zone. It is suggested to increase the longitudinal reinforcement to improve overall longitudinal shearing resistance capacity and set deformation joint in the intersection to strengthen the longitudinal deformation ability of structure.