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Performance Monitoring of Trenchless Construction Projects

Description:

Trenchless technologies involve methods of pipe or conduit installation with negligible surface disruption. Most commonly used methods include microtunneling, jack and bore, and horizontal directional drilling. The use of trenchless technologies on state highway agency right of way has been increasing rapidly in recent years, particularly near major metropolitan centers where traditional open cut excavation is simply not practical. Trenchless construction lends itself to many infrastructure applications, including water, gas, sewer, power, and communication lines. These projects are typically carried out by pre-qualified specialty contractors. Construction is frequently performed directly under a busy highway, often at relatively shallow depths. For the most part, projects are completed successfully, as the technology is fairly mature, but sometimes failures occur. Failure is usually manifested by excessive roadway deformation, sometimes resulting in a collapse. Since the construction typically takes place without diverting traffic, any sudden and substantial surface displacement of the overlying roadway has the potential for catastrophic consequences. From a state highway agency perspective, the paramount issue is safety of the traveling public and the potential legal liability. It is important to recognize that voids created at some depth may result in surface settlement after a considerable period of time following construction, due to low shear strength of soils relative to the rigidity of the pavement structure. Also, a heave of the roadway surface may result from applying excessive fluid pressure during directional drilling.

Objective:

The main objective of this study is to reduce the risks to the traveling public associated with trenchless technologies, by providing state highway agencies with the instrumentation tools on which to base a decision support system for managing trenchless projects in a safe and effective manner.

Benefits:

The potential payoff for implementing the results of this study is significant. Early warning system can prevent accidents caused by excessive roadway distress. Trenchless project monitoring is a critical safety issue that should be addressed.

Related Research:

An extensive body of literature is available on this subject, but not in an organized manner. There are also relatively new technologies for remote monitoring of deformations (e.g., LIDAR, radar, structure-from-motion photogrammetry). Generally, state highway agencies do not specify acceptable limits for surface deformation. Typical trenchless specification stipulates that no surface heave or settlement above the installation is permitted.

Tasks:

The following tasks are proposed:

Task 1. Assess the applicability of various trenchless methods and the selection criteria. Identify the risk of excessive surface displacement associated with each method. Examine current practices in trenchless project oversight by state highway agencies.

Task 2. Develop recommended criteria for threshold heave and settlement magnitudes during and after construction, considering local infrastructure conditions. Provide recommendations for the course of action by state highway agency when these limits are reached and exceeded.

Task 3. Identify current best practices for real time or near real time heave and settlement monitoring during and after construction. Examine potential surface and subsurface displacement monitoring instrumentation systems.

Task 4. Identify current best practices (including instrumentation systems) for detecting subsurface voids that may be caused by trenchless construction.

Task 5. Identify potential research needs for new instrumentation technologies that can be developed to increase the safety and reliability of trenchless construction projects.

Implementation:

State DOTs and local counties will readily embrace this research product and ensure successful deployment of this research because public safety is one of their key responsibilities.

Relevance:

State DOTs and local counties in the USA and possibly all over the world will benefit from this research

Sponsoring Committee:AKG60, Geotechnical Instrumentation and Modeling
Research Period:Longer than 36 months
Research Priority:High
RNS Developer:Edward Hoppe, Ph.D., P.E., Research Scientist, Virginia Center for Transportation Innovation and Research, 530 Edgemont Rd., Charlottesville, VA 22903 (434) 293-1960 edward.hoppe@vdot.virginia.gov
Date Posted:04/10/2014
Date Modified:01/29/2019
Index Terms:Construction projects, Performance monitoring, Trenchless technology, Shear strength, Right of way (Land), Collapse, Horizontal directional drilling, Decision support systems, State departments of transportation, Geotechnical engineering,
Cosponsoring Committees: 
Subjects    
Highways
Construction
Geotechnology

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