Although the term trenchless technology is relatively new, its principles are so. In fact, the application of trenchless construction method started at the end of 19th century, such as the early pipe jacking method and horizontal drilling method; the mortar spraying lining method used for anti-corrosion treatment of water pipeline is another "trenchless" construction method with a long history, which is still widely used at present. It was just that there was no scale at that time, and the term "trenchless technology" had not yet been adopted.
At the beginning, some people gave the definition of trenchless rehabilitation technology: trenchless rehabilitation technology refers to the construction technology of laying, repairing and replacing underground pipelines without digging trenches on the surface by means of rock and soil drilling. With the continuous improvement of understanding, it was later pointed out that trenchless rehabilitation technology referred to a kind of high-tech practical technology of laying, repairing or replacing various underground pipelines and cables by using the technical means of geological engineering without excavating the surface.
However, two key problems in the definition of trenchless rehabilitation technology do not state clearly, which make people easily misunderstand trenchless rehabilitation technology. One is "no excavation or trenching on the surface". In fact, many trenchless construction methods must excavate the working pit before the construction. The other is the rock and soil drilling means or geological engineering technology means. In fact, the current trenchless repair and replacement of underground pipelines / lines has gone far beyond the scope of rock and soil drilling enineering or geological engineering. If the trenchless rehabilitation technology is continued to be restricted by means of rock and soil drilling or geotechnical engineering, the definition of trenchless rehabilitation technology is bound to be biased. For example, many people simply equate trenchless engineering with the most widely used fixed / guided drilling technology. However, it is completely wrong.
The International Association for Trenchless Technology (ISTT) defines trenchless rehabilitation technology as a science of laying, repairing or replacing underground pipelines, pipelines and underground cables by micro excavation or trenchless technology.
The definition of trenchless rehabilitation technology by International Association of Trenchless Technology is very accurate both in connotation and extension. At the same time, it also defines trenchless rehabilitation technology as a science, which shows that trenchless rehabilitation technology is not only a simple construction technology. After nearly a hundred years of historical accumulation, trenchless rehabilitation technology has developed into a new interdisciplinary branch, which can be named as "trenchless Engineering". In fact, trenchless engineering should also include the theories, technical methods, equipment and engineering practice of pipelines inspection and detection as well as underground pipelines without excavating the surface.