Interface parameters of composite sprayed concrete linings in soft ground with spray-applied waterproofing

Abstract

Abstract:The presence of a spray-applied waterproofing membrane between the primary and secondary lining layers is important to the behaviour of a composite sprayed concrete lined (SCL) tunnel in soft ground.In order to confirm the feasibility of the composite shell lining concept, the structural adequacy of the concrete-membrane interfaces under the effects experienced in a typical tunnel needs to be investigated. This paper presents a series of laboratory tests on samples cut from composite sprayed concrete panels, to which uniaxial compression, direct tension and direct shear loadings are applied over both shortand long-term timeframes under conditions of ambient atmospheric humidity. Test results show that the interfaces are capable of resisting significant compression, tension and shear in both short-and long-term. Failures under these actions should not occur in a typical shallow SCL tunnel, and a degree of composite action between primary and secondary layers should be expected. Influence of substrate roughness and membrane thickness on the measured interface properties has been quantified. Overall, this investigation confirms the existence of composite action for composite sprayed concrete linings in soft ground, and provides parameters based on test results for further research and design.

Simulating composite behaviour in SCL tunnels with sprayed waterproofing membrane interface: A state-of-the-art review

“…(2) Tensile failure due to cohesion break within the membrane (3) Shear failure due to adhesion break between concrete and membrane (4) Shear failure due to cohesion break within the membrane These failure modes were reported in Su and Bloodworth [15] and Lee et al [16]. It was also reported that tensile and shear failures in the concrete itself do not generally occur, mostly due to higher tensile and shear strength of the concrete than the interface and the membrane.…”

“…By the time of this project, research had given understanding that the sprayed membrane interface is expected to exhibit bond and shear strength under "dry" conditions [15], but that there is the possibility of reduced strength under "wet" conditions [39][40], leading to debonding in service. Therefore, a lower bound assumption for the membrane capability (intuitively thought to be conservative) was made, neglecting both tension and shear at the interface, so the system became "unbonded double shell", similar to Crossrail.…”

“…Su and Bloodworth [18] carried out a programme of laboratory tests on beam samples cut from the same batch of composite shell test panels described in Su and Bloodworth [15] and subjected to fourpoint bending under immediate short-term loading. Partial composite structural action was proved, a range of membrane thicknesses and substrate roughness were compared, and composite action quantification methods developed.…”

Ameliorating Precast Concrete Curbs Using Rubber and Nano Material

“…Previous studies have used surface coating materials to improve permeability of concrete [21][22][23]. The aim of this study is to ameliorate the properties of rubber concrete such as penetration resistance.…”

Research on the Earth Pressure and Internal Force of a High-Fill Open-Cut Tunnel Using a Bilayer Lining Design: A Field Test Using an FBG Automatic Data Acquisition System

“…Their results revealed that a spray-applied waterproofing membrane was able to transfer stresses between both concrete linings but could not transfer any shear stress. Su and Bloodworth [3] presented laboratory tests on beam samples cut from bilayer linings. They compared the influence of different membrane thicknesses and substrate roughness and provided parameters based on test results for further research and design.…”