Pre-Reinforcement Mechanism and Effect Analysis of Surface Infiltration Grouting in Shallow Buried Section of Long-Span Tunnel

In order to solve the problem that hole-forming rate of boreholes is low and it difficult reach designed length when supporting a long pipe shed in loose stratum shallow buried section long-span tunnel, necessary pre-reinforce improve strength integrity surrounding rock. Relying on grouting project at exit Botanggou assumed material Newtonian fluid steel floral tube shows cylindrical infiltration diffusion. Through analysis structural characteristics injected stratum, conceptual model established. Twelve groups test slurry were prepared with ordinary Portland cement ultra-fine cement, through parameters each group, was selected water–cement ratio 1:1 plus 3% water glass strengthen gravel layer, 0.3% polycarboxylate superplasticizer fully strongly weathered porphyritic granite layer. on-site single-hole combining empirical formula, maximum diffusion radius calculated, sliding width sidewall deduced using Terzaghi theory. To ensure effect, 5 m expansion excavation profile taken as range. Grouting construction adopts overall periphery then interior, three-sequence opening are adopted same row holes, which can effectively prevent running grouting. For strata treated by surface grouting, smooth reaches length, there no large deformation rock excavated CD method. The treatment effect analyzed P-Q-t control method, observation monitoring results show infiltrated gelled, forms an obvious stone body, obviously improved, convergence values tunnel surface, vault subsidence, clearance do not exceed alarm value 60 mm. research provide some awareness understanding pre-reinforcement future.