Permeability and strength characteristics of silty sands grouted with cement and polymer

Hydrophilic polymer grouting with a particular water-to-binder ratio could block soil pores in a short time to prevent the loss of cement slurries in sandy strata in water-rich areas. Meanwhile, when combined with cement, the setting time and permeability of sandy soils could be minimized significantly. In this study, a series of indoor permeability tests, unconfined compression tests, and field grouting tests were conducted to investigate the influence of the ratio of polymer to water, the ratio of water to cement, polymer and cement content on the solidification time, setting time, impermeability effect, and compression resistance of silty sands and summarize the recommended grouting parameters of cement and polymer for the water-rich sandy stratum. The results illustrated that the recommended ratio of the primary and auxiliary agents in the polymer was 2:1. If the solidification time was required to be earlier than the initial hydration time of cement as the standard, the ratio of polymer to water should be higher than 1:3. The setting time of cement- and polymer-stabilized silty sands decreased with curing temperature and polymer content. The permeability coefficient of cement- and polymer-stabilized silty sands decreased nonlinearly with the increase in polymer and cement contents. Their permeability coefficients were basically within the range of 10−6 cm/s. The compressive strength of cement- and polymer-stabilized silty sands decreased with polymer dosage but increased linearly with cement content. The compressive strength and permeability coefficient of the field grouted samples showed that the cement and polymer grouted silty sand had better impermeability than that grouted with the mixture of cement and metakaolin and the mixture of cement, red mud, and phosphogypsum. The permeability coefficient of cement and polymer grouted silty sand after 28 days could reach 0.89 × 10−7 cm/s, while the improvement of their compressive strength was relatively low, with an average value of 2.46 MPa. The failure of cement- and polymer-stabilized silty sands showed typical plastic shear characteristics rather than brittle and splitting characteristics that appeared in the failure of silty sand grouted by cement and metakaolin, or the mixture of cement, red mud, and phosphogypsum. The results of this study can provide a reference for the construction of low-permeability barriers at sandy strata in water-rich areas.