GROUND MOVEMENTS CAUSED BY TRENCHLESS PIPE INSTALLATION TECHNIQUES

The ground movements caused by trenchless pipe installation techniques can have a significant effect on adjacent services and road structures. A fundamental understanding of how these techniques affect the ground is lacking. This can result in the stipulation of an overly conservative distance between trenchless pipelaying and other services, and a concomitant lack of confidence in the techniques. To rectify this, a series of laboratory simulation tests was conducted at Loughborough University of Technology, U.K. These tests simulated pipejacking or microtunneling (convergent) operations using different shield arrangements and pipebursting (expansive) operations, with the aim of determining the patterns and magnitudes of displacements in the surrounding soil. This in turn permits the prediction of movements in adjacent services and structures, as well as the development of techniques for their minimization. The tests were conducted in a rigid, glass-sided tank using semicircular shields and pipes buried in different dry sands. This arrangement allowed direct observation of the sand displacements on the centerline of the simulated operations. For the pipejacking tests, two face-support methods (open and closed faces) were used. The pipebursting operations used different sizes of existing plaster pipe, which was progressively broken out as the burster advanced, to simulate different bursting ratios. Various combinations of sand density and cover depth were used. Selected results from the three test programs are presented in terms of ground movement contour plots and vector displacement diagrams. The results confirmed that soil density strongly influences the magnitude and extent of the ground displacements. The denser soils produce a greater effect in compression situations, and looser soils have a greater effect when the soil is moving into cavities. Increasing cover depth creates a confining effect and restricts the extent of the soil movements. The open shield behaves differently than the closed shield, which displaces more soil and produces broadly similar results to those of the angled pipebursting unit. The results presented herein are essentially visual, thus permitting a full appreciation of the ground movements under various boundary conditions.

Language

  • English

Media Info

  • Features: Figures; References; Tables;
  • Pagination: p. 37-48
  • Monograph Title: Design and performance of underground pipe
  • Serial:

Subject/Index Terms

Filing Info

  • Accession Number: 00715652
  • Record Type: Publication
  • Files: TRIS, TRB
  • Created Date: Jan 25 1996 12:00AM