Abstract: In this study, drainage-induced displacement grouting technology is proposed to address directional-induced grouting in saturated confined water sand layers. Based on Darcy′s law and the law of conservation of mass, the spatial distribution equation of the seepage pressure gradient under drainage-induced displacement grouting is deduced. The saturated sand directional-induced grouting experiment is used to analyze and verify the results. The results show the following. (1) Because the grouting and drainage pressures imultaneously act on the seepage field, the seepage pressure gradient′s space distribution curve shows a law of decreasing first, then increasing. The directionalinduced seepage grouting can be realized when the lowest point of the seepage pressure gradient′s spatial distribution curve is greater than the starting gradient. (2) The theoretical derivation formula can reflect the seepage pressure gradient distribution under drainage-induced displacement grouting to a certain extent. The theoretical formula calculation results agree well with the model experimental results. (3) After the seepage pressure gradient becomes stable, the error between theoretical and experimental values is between 4.4% and 29.0%. The theoretical calculation data are all small, and the error is acceptable. (4) The drainage-induced displacement grouting can induce the directional diffusion of grout to a certain extent, forming the expected directional reinforcement area in the saturated confined water sand layer. According to existing grouting construction experiences and experimental research, the maximum spacing of drainage-induced displacement grouting should be controlled between 50 and 90 cm.

Key words: drainage-induced displacement grouting; saturated confined water sand layer, directional grouting, Darcy′s law, law of conservation of mass, spatial distribution equation of seepage pressure gradient