Abstract: During construction of Hepingdong Bridge – Sun Palace thermal power pipeline in Northern third loop road of Beijing City, the pipeline tunnel would go through beneath a couple of single-floor houses, whose area is 23.4 m×24.5 m. Due to the shallow overburden and the saturated microfine sandy clay, which is plastic and soft plastic, the strata is very weak in resisting interruption. The traditional dewatering is limited to improve the nature of the strata. Based on calculation, it is believed that the common construction method would necessarily cause much settlement and endanger the houses. Meanwhile, as the strata are hard to stand up, safety problems may be triggered in construction. In view of these, the level long steel pipes are adopted to support soil mass and grouting in the upper half face of the tunnel is operated to prevent ground water and strengthen soil without dewatering. These two methods effectively control the settlement of ground surface and ensure the perforation of the tunnel in time and running of the houses in security.

Key words: security, thermal power tunnel, going through, long steel pipe, grouting