Undrained behaviour of granular soils conditioned for EPB tunnelling – A new experimental procedure

Abstract

This paper presents a characterisation campaign carried out on granular soils conditioned for EPB tunnelling using a modified direct shear box. The main objective of soil conditioning is the reduction of its shear strength to control the counterpressure inside the bulk chamber. In order to preserve the pseudo-fluid characteristics of the conditioned soil mass, the main concerning parameters are their undrained properties. To characterise the undrained behaviour an adopted watertight direct shear apparatus was used. The purpose of this research is to define a simplified testing procedure for conditioned soil, analysing its feasibility and reliability with resources that can be found at any laboratory or job site. A comparison between the results obtained under dry and conditioned conditions is presented for three different cohesionless soils. The choice of the materials studied has been made in order to cover a wide range within sands grain size. Undräniertes Verhalten von grobkörnigen Böden für Vortriebe mit EPB-Schilden -Ein neues experimentellesVerfahren. Dieser Beitrag stellt Untersuchungen an grobkörnigen konditionierten Böden, wie sie bei Vortrieben mit EPB-Schilden vorkommen, mittels eines modifizierten Rahmenschergeräts vor. Das Hauptziel der Bodenkonditionierung ist die Reduzierung der Scherfestigkeit, um den Stützdruck in der Abbaukammer zu steuern. Um das undränierte Verhalten zu untersuchen, wurde ein wasserdichtes Rahmenschergerät entwickelt. Ziel der Entwicklung ist die Definition sowie die Überprüfung der Durchführbarkeit und der Zuverlässigkeit eines vereinfachten Prüfverfahrens für konditionierte Böden mit Mitteln, die in jedem Labor oder auf jeder Baustelle gefunden werden können. Abschließend werden die Ergebnisse von Untersuchungen an drei verschiedenen nichtbindigen Böden unter trockenen und konditionierten Bedingungen vorgestellt. Die untersuchten Böden decken ein breites Spektrum der Korngrößenverteilungen für Sande ab.

Soil conditioning in EPB shield tunnelling – An overview of laboratory tests

“…obtained results consistent with those of [34]. Recently, Carigi et al [35] studied the flow of a conditioned soil with cobbles using the test device of Figure 5 and developed assessment indexes.…”

“…The shear and rheological behaviour of the conditioned soil influence the extraction process. To evaluate these parameters both vane test [29] [30] [31] [32] [33] and direct shear tests [9] [34] have been performed. Martinelli et al [34] used a modified undrained direct shear box and demonstrated that a good conditioning reduces the shear strength of the mix.…”

“…To evaluate these parameters both vane test [29] [30] [31] [32] [33] and direct shear tests [9] [34] have been performed. Martinelli et al [34] used a modified undrained direct shear box and demonstrated that a good conditioning reduces the shear strength of the mix. Galli and Thewes [11] studied the rhe ology of the mix using a rotational rheometer device and…”

Shear Strength and Compression Coefficient for Conditioned Sand Subjected to Earth Chamber Stress Levels

“…Compression testing and vane shear testing were combined to show the effect of the void ratio on the compressibility and shear strength of foam-conditioned soil. Martinelli et al [23] used a watertight direct shear apparatus to characterize undrained behavior in order to preserve the pseudofluid characteristics of the conditioned soil. Overall, the applicability of the vane shear test is valid.…”

A new test device for the study of metal wear in conditioned granular soil used in EPB shield tunneling

“…For an optimal management and preliminary design of a tunnel it is necessary to have laboratory devices and procedures that can smoothly compare the positive effects on the soil conditioning on all these parameters. There is extensive research about the soil conditioning tests; the main informations can be found in Maidl (1995), Quebaud et al (1998), Jancsecz et al (1999), Milligan (2000), Psomas (2001), Bezuijen and Schaminée (2001), Peña (2003), Merritt and Mair (2008), Rivas et al (2009), Vinai et al (2008), Peila et al (2007Peila et al ( , 2009, Thewes and Budach (2010), Borio and Peila (2011), Thewes et al (2012), Hollmann and Thewes (2013), Todaro (2016), Peila (2014), Martinelli et al (2017).…”