Crossing the river Amu Darya along 1,800 metres with a 56" high-pressure gas pipeline using the HDD method

More and more frequently, gas transmission pipelines crossing rivers and natural obstacles are installed using the trenchless HDD technique (Horizontal Directional Drilling). Nowadays, the state-of-the-art HDD technique permits to install pipelines over distances longer than 1,800 m. However, this has not yet been implemented for pipelines with an outside diameter of more than 56''. The project of a river crossing near the Turkmen city of Karabekaul (trenchless laying of a 56'' gas pipeline towards China underneath the Amu Darya river) offered exactly such a challenge. Besides the drilling execution, the project planning and preparation were the special technical challenges. Prior to this extraordinary project, extensive examinations and plannings led to unusual measures for site facilities, execution and equipment to be applied. Among other things, special solutions regarding risk assessment during pipe insertion, drilling plant configuration and overbend construction were found and successfully implemented. In addition to the technical and local conditions, the tight schedule affected the planning and the choice of the equipment. The engineering, production and mobilization of the equipment preceded the technical implementation during a 2.5-month planning phase. The technical execution of the project (installing of the 56'' carrier pipe and the conduits running parallel) took 6 months and was finished successfully in February 2010. The successful HDD execution has a sustainable impact on the boundaries of the applied laying technique regarding feasible pipeline size and crossing section. More precisely, the experiences made during the project implementation enable a differentiated assessment of future large-scale projects regarding trenchless pipe laying.