Abstract:In the construction of long tunnel in the rock with the saturated compression strength below 5 MPa,one of the pivotal questions is to ensure the stability of the surrounding rock and safe construction. In the construction of tunnel in soft rock in both domestic and overseas engineering,the frequent collapses of rock often cause the loss of lives and equipments,the delay of time limit of the project and the increase of engineering investment. While in the successful construction of the 15 km long Dingshan tunnel in soft rock,with the use of informative design and construction technique,the safety of construction is ensured,six months of the time limit and the investment of construction are saved,and the eminent construction quality is achieved.