Abstract: It is urgent to solve the problems, i.e. damage of support structure, large deformation of surrounding rock etc.〖ＫＧ－３〗, in the construction of highground stress soft rock tunnels. Relying on Muzhailing extralong highway tunnel project which is located in carbonaceous slate stratum with the characteristics of complex geological structure, fault developed, large burial depth, and extremely high ground stress,a support scheme for large deformation of surrounding rock is studied. Firstly, the failure mechanism is analyzed by insitu test, site survey and indoor test. Then, the selfdeveloped highprestressed NPR anchor cable material is used, and a new comprehensive control system for largescale deformation disasters in the surrounding rock of highway tunnels is proposed. Finally, the control system is used to conduct industrial tests on site, and through realtime monitoring of the deformation of surrounding rock, steel arch stress and NPR anchor cable stress, the control mechanism of the NPR anchor cable is revealed. The results show that the large deformation problem can be effectively controlled by the comprehensive control system of "asymmetrical arrangement and combination of long and short anchor cables" with NPR anchor cable. The maximum deformation decreases from 2 936 to less than 240 mm and damages of primary support, i.e. invasion, cracking, etc,. are eliminated.

Key words: soft rock tunnel, support design；anchor cable with negative poisson′s ratio(NPR anchor cable); surrounding rock deformation mechanism, high ground stress, carbonaceous slate