Abstract:

A new stress testing method for tunnel foot locking bolts, electric measuring method by externally bonded strain gauge, is adopted so as to study the stress characteristics of foot locking bolts under vertical load at bolt end. The stress testing design scheme of foot locking bolt, including strain test along axial line of foot locking bolt and bending moment test, is systematically introduced by taking widely used hotrolling seamless tube of 3.5 m in length, 42 mm in diameter and 4 mm in thickness for example. The design and technologies for stress testing device of foot locking bolts, including manufacturing of dynamometry bolt and temperature compensation strip, are presented. In addition, the abovementioned method is applied by field test method at a soil slope. The testing results show that: 1) The monitoring points are all effective after installation of stress testing device. 2) The final deformation of foot locking bolt coincides with testing results under vertical loading at foot locking bolt end. 3) The abovementioned method is reliable.

Key words: tunnel, foot locking bolt, mechanical characteristic, testing method, externally bonded strain gauge