Hydraulic and earth engineering – Underground passageway – e.g. – tunnel – Boring
Patent
1991-11-06
1993-04-06
Taylor, Dennis L.
Hydraulic and earth engineering
Underground passageway, e.g., tunnel
Boring
405141, 405272, E02D 500, E21D 900
Patent
active
051998181
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The present invention relates to a method and an apparatus for detecting a collapse of natural ground in a shield driving method and, more particularly, to a method and an apparatus for detecting a collapse of natural ground in a shield driving method that is suitable for detecting the thickness of a sludge layer existing between the shield machine and the natural ground, thereby detecting a collapse condition of the natural ground.
BACKGROUND ART
In general, in a shield driving method, any collapsed condition of the natural ground on the outer surface of the shield machine is detected from the viewpoint of, for instance, controlling the charge amount of a back filling. A resistivity method has been known as a method for such detection. For instance, Japanese Utility Model Laid-Open No. 1-131186 discloses a method in which a row of Wenner electrodes are provided on an outer surface of the shield machine, resistivities differing between various strata are detected, and the thickness of a sludge layer forming the first stratum is calculated on the basis of changes in the resistivities, thereby detecting a collapsed condition of the natural ground.
With this method, however, since the values of the measured resistivities are directly used, the characteristics of the electrodes influence the calculated thickness of the sludge layer even when the characteristics of the electrodes have deteriorated with the passage of time. Thus, it has been impossible to detect the thickness of a stratum with a high level of precision. In addition, with the method (described in the above-identified publication) in which a row of Wenner electrodes are employed, resistivity measurement is possible only at a point at a certain depth basically determined by the distance between the electrodes. When multi-point measurement is to be performed, a large number of electrodes must be used. However, when a large number of electrodes are used, it is necessary that the position of the electrode on the side of the power supply source be successively changed. Thus, operational efficiency is greatly deteriorated In addition, the fact that the current supplied to the stratum cannot be easily stabilized further deteriorates efficiency. For these reasons, the disclosed method has too many problems to be applied to a shield driving method which requires such a measurement operation to be performed within a short period.
Furthermore, it is very difficult to determine the configuration of a collapse with the above method.
SUMMARY OF THE INVENTION
The present invention has been accomplished in view of these problems An object of the present invention is to provide a method and an apparatus for detecting a collapse of natural ground in a shield driving method that is capable of precisely measuring resistivities, accurately determining the configuration of the collapse, and performing measurement within a short period of time.
In order to achieve the above object, a method for detecting a collapse of natural ground in a shield driving method according to the present invention primarily comprises: using a measurement electrode row of dipole electrodes and a reference electrode row of Wenner electrodes, which rows are provided on an outer surface of a shield machine; obtaining a measurement resistivity map from combinations of electrodes in the measurement electrode row and also obtaining a reference resistivity map corresponding to the measurement resistivity map by calculating, from the reference electrode row, certain resistivities of the natural ground and the thickness of a strata boundary; and obtaining a variation ratio map by calculating the ratios of measured values of the measurement resistivity map with respect to calculated values of the reference resistivity map, thereby detecting a collapsed condition of the natural ground.
An apparatus for detecting a collapse of natural ground in a shield driving method according to the present invention comprises: a measurement electrode row of dipole electrodes and a refere
REFERENCES:
patent: 4384807 (1983-05-01), Yamazaki
patent: 4482270 (1984-11-01), Unger et al.
patent: 4516878 (1985-05-01), Rebhan
patent: 4854776 (1989-08-01), Hentschel et al.
Abe Tomoyuki
Ichimura Yasuhiko
Kanemitsu Yasuo
Sakanishi Shoichi
Shibatani Kanji
Kabushiki Kaisha Komatsu Seisakusho
McBee J. Russell
Taylor Dennis L.
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