Property and applicability of shield grouting material: State of the art and perspectives

Synchronous grouting is one of the most important methods to prevent surface settlement and water seepage accidents in shield tunnel construction. Various compositions and properties of shield grouting materials are required for different adverse geological conditions. This study provides an overview of composition, typical engineering performance, influence factors of shield grouting materials based on the grouting treatment requirements of disadvantageous geological conditions. The shield synchronous cementitious grouting slurry is classified into two categories i.e., single liquid slurry, double liquid slurry. The former is suitable for relatively stable formations with low requirements for setting time and early strength, whereas the latter finds application in water-rich strata due to its rapid setting time and superior early strength. The fundamental characteristic requirements of shield grout include working properties, mechanical properties, mineral composition and micro-structure characteristics, etc. Water-binder, binder-sand and bentonite-water ratios are the direct factors of slurry performance. Properties of slurry are controlled by adjusting the contents of cement, lime, fly ash, sand, bentonite and admixture. How to inject shield grouting material behind wall is an important research issue. The construction technologies including synchronous grouting, secondary grouting, etc, were summarized. In addition, two suggestions are put forward for the future research directions of shield tunnel grouting. One is to select suitable grout type and ratio for different grouting environments and requirements, the other is to improve the existing grouting materials with more superior performance and better economic benefits.