Hydroshield drive with a diameter of 13 m in the Lower Inn Valley – Project design and experience from construction of contract H3‐4 / Hydroschildvortrieb mit 13 m Durchmesser im Unterinntal – Projektplanung und Erfahrungen im Baulos H3‐4

Klitzen, Jens; Herdina, Johann

doi:10.1002/geot.201600036

Cited by 4 publications

(1 citation statement)

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“…The increased pore water pressure measured in front of the tunnel face outside of slurry penetrated zone during excavation in finer sandy soils [9,10]. Several authors in various projects later con firmed these measurements [11][12][13][14]. The occurrence of in creased pore water pressures is nowadays a wellknown issue in the scientific community.…”

Section: Topicsmentioning

confidence: 99%

Influence of stagnation gradient for face support calculation in Slurry Shield Tunnelling

Zizka

Kube

Schößer

et al. 2020

Geomechanics and Tunnelling

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In slurry shield tunnelling, a reliable face support is presumed if a sufficient support pressure is transferred and the slurry excess pressure provides efficient support pressure on the soil skeleton. The required support pressure is calculated in reference to the groundwater pressure and the earth pressure. In this paper, the sliding wedge mechanism is applied. To ensure face stability, the support pressure transfer needs to be provided within the theoretical sliding wedge at the tunnel face. Therefore, the penetration depth of the bentonite suspension as a support medium has to be kept within limits. Research shows that certain penetration is required.The stagnation gradient defines the relation of the support pressure and the penetration depth of the suspension. The gradient has a described minimum, but also an undefined but existing maximum. The German standard DIN 4126 describes two cases for the minimum at each trench depth: Either the pressure losses due to the pressure acting outside the sliding wedge are less than 5 % or the stagnation gradient is at least 200 kN/m3. If the supporting pressure gradient is below 200 kN/m3, DIN 4126 defines rough reduction factors. For a more precise observation of the stagnation gradient, this paper presents a detailed supplement to the DIN 4126 approach taking the tunnel diameter and the angle of the sliding wedge into account. The aim is to determine the minimum recommended stagnation gradient for which no increase of the slurry excess pressure is necessary due to too deep penetration.

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Section: Topicsmentioning

confidence: 99%