TRENCHLESS CONSTRUCTION

Trenchless Construction



Trenchless Construction

Introduction

Trenchless technology includes all methods of underground utility construction and renewal with minimum surface disruptions. It is divided into two main areas of trenchless construction: installation of new utilities, and pipeline renewal for renewing old and deteriorated utility systems. This article evaluates some project parameters that need to be carefully planned and properly dealt with during field operations for trenchless construction methods. Field problems might occur even with experienced machine operators. Therefore, in addition to machine operation skills, a good operator's skills should include safety, project planning, and familiarity with technical and legal aspects of underground construction.

Discussion

Trenchless construction is the process of installing or replacing underground utility systems without open-cut excavation. In the past several years, the use of trenchless construction methods has significantly increased. This includes the use of pipe jacking, micro tunneling, and horizontal directional drilling, and guided boring systems. The increase in use of trenchless construction is driven by the need to replace an aging urban utility infrastructure system and install new facilities, while minimizing disruption to traffic, communities and business, reducing environmental impact and lowering the high costs of pavement removal and site restoration. A critical area of application for trenchless construction is the crossing of conduits beneath highways, streets, railroads, and other transportation arteries. These conduit installations need to be implemented without disruption to vehicular traffic and with minimal effects on the long term integrity of the overlying roads or structures. Earlier studies have indicated that open cut patches may decrease the life of a roadway by up to 30%. Many users are not taking full advantage of trenchless methods because they lack an understanding of which methods to utilize and how properly to design with these methods. It is not beneficial simply to superimpose a trenchless design over a conventional open-cut approach. While the technology has moved forward, there exists limited technical data and knowledge of the relationships among the soil characteristics, cutting mechanisms, soil loads, and conduit materials and dimensions. The effects of trenchless methods on the overlying roadways must be considered in design. A quantification of soil loading mechanisms would provide a rational basis for pipe and conduit design. A better understanding of the soil/pipe/machine interrelationship would permit improvements in the design and performance of trenchless equipment and installed pipes. Project planning involves thorough considerations of the project parameters such as safety, soil conditions, productivity, surface access, spoil disposal, available surface area, and so on. The trenchless contractor should also be creative for any feasible approaches to enhance the project efficiency. For example, "Is it possible to start more than one bore from the same jacking pit?"

Site Investigation and Information Required on Soil Conditions

When designing, planning, and cost-estimating a trenchless operation, it is advisable that a full site investigation be conducted to determine the characteristics of the on-line soil as well as the surface conditions within the working area, and to assess the level of difficulty of the ...