Study on the Influence of Mix Proportioning on Cemented Mortar Engineering Properties for Tail Void Grouting of Shield Tunnel: Fid-Bau Portal

Study on the Influence of Mix Proportioning on Cemented Mortar Engineering Properties for Tail Void Grouting of Shield Tunnel

Han, Yuewang / Zhu, Wei / Liu, Quanwei / Zhong, Xiaochun

Abstract

The application of cemented mortar in tail void grouting of shield tunnel construction is becoming increasingly popular. However, the effect of mix ratios on cemented mortar performance is not well understood, and grout engineering properties cannot meet the demand of shield tunnel construction. Pumping difficulty and pipe blockage were occurred during backfill grouting process, and large stratum settlement was induced while shield passed. Determination method of mix proportioning for desired grout engineering properties is unreasonable, mix proportioning cannot be adjusted quickly with shield construction conditions change. Orthogonal experimental design method is used to study on grout engineering properties. The qualitative and quantitative relationships between mix ratios and grout engineering properties were obtained by variance analysis and regression analysis of experimental results respectively. Finally, mix ratios were calculated for desired grout engineering properties by goal programming method, and the rationality of goal programming results was examined by trial. Experimental analysis results show that the influence of water-binder ratio on all grout engineering properties is mostly obvious, and water-binder ratio is key impact factor. Bleeding rate and segregation degree reduce with the increasing of bentonite-water ratio, so bentonite is beneficial to increase the physical stability of cemented mortar. Grout volume shrinkage is mainly induced by drainage consolidation, so grout shrinkage rate decrease with the enhancing of mortar water retention ability and the decreasing of binder-sand ratio. Cemented hydration products were dispersed by the deflocculating action of water-reducing retarder to prolong the setting time of mortar and decrease the early age strength of mortar. It was illustrated that combination of orthogonal experimental design, regression analysis and goal programming is an effective method to determine mix proportioning quickly that is suitable to shield construction environments.