Three-dimensional induced polarization method advanced forecast system carried by earth pressure balance shield, and detection method

Abstract

The invention discloses a three-dimensional induced polarization method advanced forecast system carried by an earth pressure balance shield, and a detection method. The system penetrates a needle-like electrode into soil for power supply and acquisition by use of a push electrode system carried by a cutter head and overcomes the difficulty of zero detection space in a conventional earth pressure balance shield. Detection currents are enabled to be distributed forwards by use of a shielding electrode, and a guniting device on the cutter head injects a high-resistance grouting material towards soil around the cutter head and the shield, and the difficulties of electromagnetic interference and conduction of currents by taking the shield as a good conductor are overcome. By use of automatic control in a whole process, multipath parallel acquisition and a rapid inversion means, the difficulty of small detection time is overcome. The method provided by the invention realizes detection of spherical weathering bodies, soft and hard layered strata, front full-section hard rocks, pebble layers and muddy layers by use of resistivity differences among geologic bodies; and detection of water containing condition of a water-rich layer by use of excitation polarization half failure is realized.

Description

technical field [0001] The invention relates to a three-dimensional IP method advanced forecasting system and detection method carried by an earth pressure balance shield. Background technique [0002] The soil pressure balance shield is cut by the cutter head rotating the soil, and the cut soil enters the sealed soil cabin. While the mud-water pressure in the sealed soil cabin is balanced with the soil pressure on the excavation surface, the shield is continuously unearthed by the screw conveyor. structure. The construction technology of earth pressure balance shield tunneling has been matured in a large number of engineering practices in recent years, and it has been widely used and gradually become the main development direction of urban tunnel construction. [0003] However, the occasional geological disasters in front of the tunnel seriously restrict the development of shield tunneling engineering. The common sources of disasters during the construction of earth press...

AI Technical Summary

Problems solved by technology

When there are obvious soft and hard layers on the top and bottom of the excavation strata, it is difficult for the shield to control the excavation direction and self-balance;

[0009] 6. Unknown buried objects, unknown underground pipelines, toxic gas-bearing layers, etc.

[0011] For a long time, the majority of scientific researchers and engineers have made many attempts to apply the advanced prediction method of geological disasters in the construction of earth pressure balance shield: it is difficult to reflect the comprehensive geological conditions in front of the tunnel face by using advanced drilling rigs for horizontal drilling, and it is very easy to cause missed reports , misreporting, and misreporting will cause potential safety hazards and high costs; the seismic source generation method required by the seismic method is difficult to effectively apply to the lining of shield tunnel segments; due to the narrow construction space of shield tunnels and strong electromagnetic interference, transient electromagnetic and The detection accuracy of geological radar is difficult to guarantee. The attempt to install the geological radar antenna on the cutter head of the shield machine has encountered great difficulties in the modification of the cutter head and antenna protection; Some results have been achieved in advance forecasting, but it is only effective in the detection of boulders in front of the tunnel face, and frequent advance drilling in actual engineering has brought huge economic costs and time costs; foreign countries are more commonly used BEAM (Bore-Tunneling Electrical Ahead Monitoring) system, a one-dimensional focused IP method advanced forecasting system, cannot obtain three-dimensional information of the geological conditions in front of the tunnel face and cannot solve the problem of shield metal conduction, the detection distance is short, and the use is time-consuming and complicated , failed to be effectively promoted in shield tunneling projects in China

[0012] Therefore, there is currently no advanced forecasting method that can quickly and reliably realize the adverse geological disaster forecasting function in the construction of earth pressure balance shield tunnels.

This is because the advance detection environment of earth pressure balance shield tunnel construction is extremely harsh, and there are unavoidable difficulties in the advance detection process:

[0013] 1. In terms of space, the cutter head of the earth pressure balance shield is always in close contact with the soil on the tunnel surface and the cutter head cannot be retracted. Poor full-face tunnel boring machine (TBM) can achieve a narrow detection space of about 20cm between the cutter head and the tunnel face, and the earth pressure balance shield can be said to have no detection space at all;

[0014] 2. The shield itself has the same strong electromagnetic interference as the TBM

For the application of electromagnetic detection methods in the construction of earth pressure balance shields, the more difficult problem is that the shield cutterhead and the shield, as good conductors, are closely coupled with the face of the tunnel and the soil in the soil bin, which makes the electrical exploration difficult. It is difficult for the supplied current to flow into the front of the face, which seriously affects the detection;

[0015] 3. In terms of the structure of the earth pressure balance shield itself, since the cutter head and the front shield soil bin constitute a closed metal box, it is difficult for various geophysical signals in front of the tunnel face to break through the strong shield and transmit wirelessly to the outside. For wired transmission, due to the shield The cutter head rotates continuously during the excavation process, while the shield, the front shield soil bin, and the pressure plate are fixed, which makes it difficult to arrange the cables between the detection electrodes and the measuring host

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