Experimental study and field validation on soil clogging of EPB shields in completely decomposed granite

Abstract

Clogging may occur inside the shield machine during earth pressure balance (EPB) tunnelling in cohesive soils. Soil conditioning can be used to reduce clogging potential and ensure the efficiency of the shield tunnelling. The current methods used to assess the clogging potential mainly focus on pure clayey soils or artificial mixed soils, the clogging in natural weathered soils is less studied. This paper studied the clogging when tunnelling in completely decomposed granite by laboratory tests, followed by field validation. In the laboratory tests, the torque and excavation speed were recorded and the soil distribution on the cutting device were analyzed. It appeared that when clogging happens, the excavation speed drops and the fluctuation in speed increases, while the torque rises as well as the fluctuations in the torque. Clogging first covers the cutters, then fill in the intervals between cutters, and finally blocked the openings on the cutting device. The opening at the central part of cutting device is of vital importance to prevent clogging. The process of clogging can be divided into three stages, the initial stage, the stabilized stage and the clogging stage. In-situ data from Guangzhou Metro Line 21 showed that clogging on cutterhead was effectively avoided when using the recommended soil conditioning scheme. Furthermore, the clogging evaluation method and process of clogging proposed are consistent with field validation and with current major clogging assessment method.

Effects of changing water content of clay-content rocks on field cutter consumption rate of roadheaders: a case study of porous ignimbrites

“…Hassanpour et al (2010) analyzed the performance of a double shield TBM in pyroclastic rocks, noting that water indirectly affects machine performance due to its effect on the strength and alteration of the rock mass. Increasing water content causes problems, especially in excavating clay-rich and fine-grained soil and rock formations, and many researchers investigated these problems, especially clogging, for TBM excavations (Thewes and Burger 2005;Hollmann and Thewes 2013;Chen et al 2022). Chen et al (2022) emphasized that clogging will reduce the penetration rate of cutters, resulting in excessive wear.…”

“…Increasing water content causes problems, especially in excavating clay-rich and fine-grained soil and rock formations, and many researchers investigated these problems, especially clogging, for TBM excavations (Thewes and Burger 2005;Hollmann and Thewes 2013;Chen et al 2022). Chen et al (2022) emphasized that clogging will reduce the penetration rate of cutters, resulting in excessive wear. In addition, many studies showed similar results for TBMs' disc cutters (Peila et al 2019;Avunduk and Copur 2019).…”

Impact of anti-sticking coating technology on shear strength at the clay-metal interface in cohesive strata

“…Based on current engineering experience, both slurry pressure balance (SPB) and Earth pressure balance (EPB) shields can face clogging issues in clayey strata (Chen et al, 2022;. To mitigate shield clogging during EPB tunneling, soil conditioning chemicals are frequently injected ahead of the cutter head (Martinelli et al, 2015;Zumsteg and Langmaack, 2017;Liu et al, 2018;Wang et al, 2021).…”

Research and Experimental Application of New Slurry Proportioning for Slag Improvement of EPB Shield Crossing Sand and Gravel Layer

“…With the rapid development of urban rail transit construction, subway shield construction has been widely used with its unique advantages [1]. The EPB shield tunneling in Beijing is often carried out in sandy gravel soil [2][3][4], and the excavated soil mass in the natural state cannot meet the requirements of plastic fluidization of soil mass [5][6][7]. Therefore, this can easily lead to the instability of the excavation surface [8][9][10][11][12], and cause the closure of the pressure chamber [13][14][15], the caking of the pressure chamber [16], gushing [17,18], and other technical problems often encountered in the construction of soil layers.…”