The present invention relates to the use of foaming additives in liquid, paste or powder form, to condition soil excavated with a tunnel boring machine. Said additives can be classified as readily biodegradable and are characterised by a lower ecotoxicological impact than commercial products.

The present invention relates to the use of foaming additives in liquid, paste or powder form, to condition soil excavated with a tunnel boring machine. Said additives can be classified as readily biodegradable and are characterised by a lower ecotoxicological impact than commercial products.

Disclosed is a liquid foaming additive for use in mechanised excavation by a tunnel boring machine, containing 5-40% by weight of one or more surfactants, 0.01-5% by weight of one or more biopolymers, and 55-94.99% by weight of water.

Disclosed is a liquid foaming additive for use in mechanised excavation by a tunnel boring machine, containing 5-40% by weight of one or more surfactants, 0.01-5% by weight of one or more biopolymers, and 55-94.99% by weight of water.

The invention relates to a foam generator (14) for an earth-pressure-balance-shield tunnel-boring machine comprising: a mixing chamber, which has a first inlet opening (22) for a foamable liquid and a second inlet opening (23) for a gas and a foam outlet opening (24); a liquid-feeding device connected to the first inlet opening (22); and a gas-feeding device connected to the second inlet opening (23). The mixing chamber contains a tubular flow chamber (28) having the first inlet opening (22) at one end and the foam outlet opening (24) at the other end. A segment of the flow chamber (28) is designed as a gassing section having a gas-permeable porous wall (26) and adjoins a pressure chamber (29) having the second inlet opening (23) in such a way that the gas fed through the second inlet opening (23) under a pressure enters the flow chamber (28) through the porous wall (26) and, in the flow chamber, mixes with the liquid in such a way that foam is formed. The gas-feeding device and the liquid-feeding device are designed in such a way that the pressure of the fed gas can be set in such a way that the pressure of the fed gas is greater than the pressure exerted on the porous wall (26) by the liquid and that a desired ratio of fed gas to fed liquid is achieved. In a method for conditioning removed soil material as a supporting medium for an earth-pressure balance shield, removed soil is fed to an excavation chamber. Depending on the soil quality, foam is provided in that a foam generator having a gassing section of a specified length, of a specified flow cross-section, and of a specified pore size and pore density is provided and the ratio of fed gas to fed liquid is set in such a way that a desired structure and size of the foam bubbles result. The exiting foam is fed to the excavation chamber and mixed with removed soil.

A shield cutterhead for cutting a diaphragm wall with steel I-beam comprises a cutterhead body, a plurality of main cutter beams, an auxiliary cutter beam, a central double-disc roller cutter, and a tool group. The central double-disc roller cutter is arranged at a center of a working face of the cutterhead body and connected to the plurality of main cutter beams. The plurality of main cutter beams are arranged radially along the cutterhead body. The auxiliary cutter beam is arranged between adjacent main cutter beams. The tool group is mounted on the plurality of main cutter beams and the auxiliary cutter beam. Each of the central double-disc roller cutter, the plurality of main cutter beams, and the auxiliary cutter beam are arranged in six different tiers from a center to an edge of the cutterhead body based on heights of the central double-disc roller cutter and the tool group.