Abstract：
Consｉdering differences and complexity of composite stratum, cutter may be worn quickly and mud may be left on cutter head if the soil in soil chamber is not successfully modified during shield construction on composite stratum. Therefore, application of soil modifier is a key technique for shield construction on composite stratum and four different additives, including bentonite, heavy polymer, foam and dispersant, etc., shall be added in different strata. Additive application in composite stratum shield excavation project on Ｎo.3 plot of Guangzhou subway line 6 is taken as an example herein to discuss the structure of shield machine additive injection system, characteristics of different additives and injection parameters for different segments, as well as effect of additive.
