Abstract: A new type of lightweight slurry for secondary shield grouting is developed to inhibit the floating of shield segments during tunneling in waterrich hardrock sections. The slurry is suspended above the segment, and it can rapidly solidify. According to comparison and selection, the hydrophobic expanded perlite, high belite sulfur aluminate cement, flocculant UWB Ⅱ and UWB Ⅲ, and polycarboxylic superplasticizer BSH200 can be employed as test raw materials. The effect of various factors on the properties of the slurry, including bulk density, compressive strength, and dispersion resistance, is investigated using the orthogonal test method. Finally, the optimal mix ratio for the slurry is obtained and verified via field test. The results show that the lightweight slurry has an inhibiting effect on the floating of segments.

Key words: shield grouting, lightweight slurry, mix ratio, orthogonal test