Standard Design and Construction Guidelines for Microtunneling
|Publication Date:||1 January 2015|
This standard guideline covers planning, design, pipe materials, and construction of microtunneling. The term microtunneling is defined as a trenchless construction method for installing pipelines. The North American definition of microtunneling describes a method but does not impose size limitations on that method; therefore, a tunnel may be considered a microtunnel if all of the following are used during construction:
Remote control: The microtunneling boring machine (MTBM) is operated from a control panel, normally located on the surface. The system simultaneously installs pipe as the ground is excavated and removed. Personnel entry is not required for routine operation.
Guidance: The guidance system usually consists of a laser beam projected onto a target in the MTBM. With this system, the MTBM is capable of installing gravity sewers or other types of pipelines to the required tolerance for line and grade.
Pipe jacking: A pipeline is constructed by consecutively pushing pipes and the MTBM through the ground, using a jacking system for thrust.
Continuous support: Continuous pressure is provided to the face of the excavation to balance groundwater and earth pressures.
Part II of this standard guideline presents planning aspects of microtunneling.
Part III of this standard guideline presents design aspects of microtunneling.
Part IV of this standard guideline presents pipe material aspects of microtunneling.
Part V of this standard guideline presents construction aspects of microtunneling.
This standard guideline may be used as a reference by owners, engineers, contractors, and construction managers. This document is to be used as a guideline only for development of the trenchless project, including engineering, drawings, specifications, submittal requirements, and work plans. Each project has its own set of unique challenges and conditions. All sections of this guideline may not be applicable to all projects. The engineer should use a standard of care and good judgment in selecting which items are appropriate and relevant to the specific project after a thorough review of the project site conditions. In no case should this document be used as the project specification.
The guidelines in this document are intended for use by owners, engineers, and contractors familiar with the installation and pipe characteristics that affect the structural behavior of pipe for jacking installations and the significance of the installation requirements associated with the construction method. Before applying the guidelines given in Parts II, III, IV, and V, the user should review the guidance and requirements given in this standard practice and the commentary.
The values of dimensions and quantities are expressed in SI (metric) units, which are to be regarded as standard. SI unit values are converted to English unit values, which are presented in parentheses following the SI units. The use of SI units is in accordance with ASTM Practice E380. English units expressed in parentheses are supplied for information only and are not a part of this standard practice.
Some of the applicable standards referenced may have a double designation (Axxx/AxxxM) or separate inchpound (English) and SI (metric) units.
The commentary in the applicable sections of this guideline is provided for background and clarification.
Microtunneling is a highly specialized and technical form of construction. The engineer and the contractor should have experience that covers the size, length, ground conditions, complexities, and risks of a particular project. Qualifications of the engineer designing the microtunnel, the engineering firm responsible for the design, and key personnel should be checked and verified before the design and implementation of the project to ensure a proper microtunnel design and to ensure that performance and project goals are met. Engineering firms without the requisite microtunneling qualifications should hire qualified staff or a microtunneling subconsultant knowledgeable in the field. The contractor and its key personnel should be prequalified before bidding or before award of the microtunneling project. More details on suggested contractor qualifications are discussed in Sections 15.4 and 21.2.