Portal Design and Construction Plan of Highway Tunnel in Mountain Area Based on New Concept of Environmental Protection

Under the complicated condition of topography and geology in the mountain area,to choose the tunnel portal position and portal type proposal feasibly is the important factors to the environmental protection,smooth implementation of construction,safety operation and engineering cost saving.Each portal type proposal shall highlight safety,and give consideration of environmental protection.Large-scale artificial slit in tunnel portal construction should be avoid,the early entrance shall be adopted once the tunneled condition is ready in order to effectively avoid portal engineering geology diseases,and to protect the natural environment of the tunnel site area.