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Abstract In order to investigate the mechanism of grouting strengthening the fault gouge of Yonglian tunnel，a test system including a module of grouting technology，a module of injection medium and a module of information collection was designed. The orthogonal uniaxial compression tests，tests for the typical characteristics of pulp-rock interfaces and the scanning electrum micrographs(SEM) tests for fault gouge were carried out. The uniaxial compressive strength of the fault gouge was increased by 181%–2 535% after grouting. The strengthened mass was damaged through the process of the cracking of pulp veins，the breaking of the pulp-rock interfaces and the failure of the soil grout composite. The fault gouge was strengthened by the skeleton strengthening mode，and the key factor for raising the grouting effect was the grouting pressure. The cohesion of the pulp-rock interfaces was increased by 93%–274% after grouting. The influences on the strength of pulp-rock interfaced under the different grouting pressures，materials and initial dry densities were analyzed. When the cement slurry was used，the cohesion was increased by 125%–148%. The fault gouge was transformed from the floc structure into the overall densified structure after grouting. The pulp-rock interface was composed of the cementation plane，the transition area of permeability and the transitional area with micro factures. The direct and indirect strengthening modes of the pulp-rock interface are defined.
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2015, Vol. 34 
