Potential Risks Of HDD Project And Its Countermeasures

Horizontal directional drilling technology a non-excavation technology. As a way to present the technology in installation of water pipes, drain pipes, oil and gas pipelines, telecommunications, pipelines, city gas pipelines, urban central heating pipes, power pipes, and cable networks in a wide range of applications. However, due to HDD an underground pipe installation technology with unknown, potential security risks. Therefore, this paper pipe installation on the horizontal directional drilling construction of potential safety hazards are analyzed, and the proposed elimination of the program. The main contents and conclusions are as follows:(1) In the horizontal directional drilling pipe installation and construction process, the shop makes the drill pipe drilling excavation stress field surrounding soil redistribution effects of stress, and thus disturbed the surrounding soil. Pipe installation on the surrounding facilities, the impact of drilling, including:the impact of surface heave, the construction of the ground tilt, ground curvature of the building, the ground level of deformation. Through the Rankine earth pressure and pore wall elastic-plastic mechanics theory of the formation of the mechanism.(2) In the horizontal directional drilling pipe installation and construction completed, the residue formed by reaming holes. The remaining holes will be in the long-term impact after construction, mainly:long-term impact of Settlement and by the groundwater. Long-term settlement also includes a stress redistribution caused by settlement and consolidation settlement; affected mainly by ground water piping and land subsidence. Residual-cavity in the safety of the surrounding facilities are:the impact of facilities on the surrounding piping; capacity impact of changes on the surrounding facilities; capacity impact of changes on the surrounding facilities.(3) The use of simulation software FLAC3D to simulate different bore diameters, different installation depths and different angles of internal friction of the dense sand. Simulation of the plastic zone occurs through the termination conditions, under different conditions the maximum allowable radial mud pressure value. In the same formula using the Delft radial mud on the maximum allowable pressure value was calculated and the results obtained with the FLAC3D compared. Delft maximum allowable radial mud pressure predicted value than the value of FLAC3D larger, two theories of the calculation error between the two assumed mainly by the stress field is different from the model boundaries, the different nature of the soil caused.(4) The impact of the residual holes, need to be eliminated. In this paper, grouting of the occasion required, appropriate grouting material is discussed. And expected the shrink rate after grouting cement slurry less than 7%, after grouting the settlement of the surrounding soil can be reduced to one-tenth of the settlement before grouting.