Simulation test for permeation grouting reinforcement effect of sand layer

Permeation grouting method is effectively used in sand layer which usually exposed by mine shaft to shutoff water and reinforce strata. To study the permeation grouting reinforcement effect of sand layer,a simulation test device was developed for testing permeation grouting,which can grout several samples simultaneously and measure permeabil- ity coefficient without mold stripping. Compressive strength, deformation modulus and permeability coefficient were used as the evaluation index of grouting reinforcement effect. With four influencing factors,including sand layer grada- tion,cohesive soil content,water cement ratio and grouting pressure,the or-thogonal test of permeation grouting rein- forcement effect was implemented. Ultimately,the main controlling factor of grouting reinforcement effect was obtained,and the deformation and failure characteristics of grouted sand samples under different conditions were revealed. Re- sults show that:sand layer obtains better performances after grouting,three day compressive strength reaches 0． 5-8． 5 MPa,three day deformation modulus reaches 35 -750 MPa,and one day permeability coefficient reaches 10-6 ~ 10-7 cm / s. Water cement ratio of slurry is the main con-trolling factor of permeation grouting reinforcement effect of sand layer. When water cement ratio grows,the compressive strength,deformation modulus and anti-permeability of sand layer will decrease significantly. De-formation and failure mode of grouted sand is affected by water cement ratio markedly. Low water cement ratio (W / C = 0． 8) will lead to global failure mode. High water cement ratio (W / C = 1． 6) will result in local deformation and failure mode,and the bleeding water effect of cement will affect the failure process of grouted sand. First selection of cement grout with low water cement ratio is suggested in the permeation grouting pro- jects of sand layer.