Detection of voids in the annular gap using ground penetrating radar and determination of the in-situ deformation properties of pea gravel

Michael R. Henzinger, Michael Willmes, Manuel Lagger, Andreas F. Kathage, Bernd A. Moritz, Wulf Schubert

Research output: Contribution to journalArticleResearchpeer-review

Abstract

When using shield machines, the excavation support is established using prefabricated concrete segments. The structurally required cavity between the built ring and the rock mass is usually filled with pea gravel in hard rock conditions. The backfilled material ensures the necessary bedding and evenly distributes the rock loads. To evaluate the in-situ deformation behaviour of pea gravel, a testing device was developed that measures the reaction of the backfill under load increase and load decrease on the basis of the static load plate test. The test is carried out via the opening for pea gravel injection. The results have shown that the elasticity of pea gravel is predominantly influenced by the load level and the type of loading. Subsequently, the detectability of possible voids in the annular gap was evaluated by means of ground penetration radar. For this purpose, the feasibility of the measurements was confirmed by a numerical study. Furthermore, the boundary conditions and the propagation behaviour of the electromagnetic waves could be demonstrated. With calibration measurements, the electromagnetic properties of all components involved in the system segmental lining and annular gap were determined. An extensive series of analogue model tests confirmed the detectability of the transitions from dry, wet and water-saturated pea gravel to water- and air-filled voids. In the final series of experiments, the transition between pea gravel and hollow space in the annular gap was successfully detected at on-site installed lining segments.

LanguageEnglish
Pages236-250
Number of pages15
JournalGeomechanics and Tunnelling = Geomechanik und Tunnelbau
Volume11
Issue number3
DOIs
StatusPublished - 1 Jun 2018

Fingerprint

Gravel
ground penetrating radar
void
gravel
Radar
Rocks
Linings
analog model
Precast concrete
electromagnetic wave
backfill
hard rock
Excavation
model test
Electromagnetic waves
rock
elasticity
detection
in situ
Water

Keywords

    ASJC Scopus subject areas

    • Civil and Structural Engineering
    • Geotechnical Engineering and Engineering Geology

    Cite this

    Detection of voids in the annular gap using ground penetrating radar and determination of the in-situ deformation properties of pea gravel. / Henzinger, Michael R.; Willmes, Michael; Lagger, Manuel; Kathage, Andreas F.; Moritz, Bernd A.; Schubert, Wulf.

    In: Geomechanics and Tunnelling = Geomechanik und Tunnelbau, Vol. 11, No. 3, 01.06.2018, p. 236-250.

    Research output: Contribution to journalArticleResearchpeer-review

    Henzinger, Michael R. ; Willmes, Michael ; Lagger, Manuel ; Kathage, Andreas F. ; Moritz, Bernd A. ; Schubert, Wulf. / Detection of voids in the annular gap using ground penetrating radar and determination of the in-situ deformation properties of pea gravel. In: Geomechanics and Tunnelling = Geomechanik und Tunnelbau. 2018 ; Vol. 11, No. 3. pp. 236-250.
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