关键词: 水平定向钻;扩孔施工;地表变形;强度理论效应;

Abstract: The buried depth of pipelines in some urban underground projects is shallow(belonging to semi-infinite space soil),and the overlying soil pressure is small.Therefore, the horizontal directional drilling used in reaming construction is often in an over-pressure state, and can easily lead to surface uplift deformation and ground slurry.Based on the theory of circular cavity expansion and the mirror method, the analytical solution of surface displacement during the construction of horizontal directional drilling in semi-infinite space soil was derived, and a crossing project of Xi′an Metro Line 10 was taken as an example for verification calculation.The results showed that the measured values were consistent with the theoretical values, and the average error was only 7%.Increasing the number of reaming stages, cohesion and internal friction angle could reduce surface deformation.The effect of strength theory cannot be ignored, appropriate strength criterion should be selected according to the soil, and the D-P1 and D-P3 criteria should be avoided.The analysis results can provide some theoretical support and technical reference for the engineering application of horizontal directional drilling technology.

Key words: horizontal directional drilling; reaming construction; ground deformation; strength theory effect;