A Review of Experimental and Theoretical Studies on the Slump of Conditioned Spoils of Earth Pressure Balance Shields

During the tunnelling of earth pressure balance shields, it is often necessary to evaluate the physical and mechanical properties of the conditioned spoil so that the parameters can be adjusted in real-time to optimize the shield tunneling parameters and ensure safe and efficient construction. Due to different advantages, such as simple equipment, convenient operation and intuitive results, slump test has been widely used in the field to measure and determine the plastic fluidity of conditioned spoil. In terms of tests on the slump of conditioned spoil of earth pressure balance shields, this paper offers a detailed analysis of domestic and foreign test techniques for slumps and developments in theory and numerical calculation, from the following four perspectives: the suitable slump state indicators for conditioned spoil, influence factors and mechanism of conditioned spoil slump, rheological theory and numerical simulation of slump tests, This paper also summarizes gaps in existing researches, and puts forward a proposal for future research direction: to propose new evaluation indicators for spoil conditioning state based on the whole process of slump development; to investigate the impact laws of foam decay, chemical properties and mineral composition of the spoils on the slump and the inherent mechanisms; to improve the rheological theoretical model for describing the slumping behavior of conditioned spoil, and construct the mapping relationship between the slump and the rheological parameters; to investigate the relationship between the slump of conditioned spoil and flow behavior and rheological parameters under pressure.