JPH09229783A - Stress measuring apparatus for shotcrete - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make it possible to improve the measuring accuracy by providing a plurality of strain gages mutually deviatedly in the depth directions on the inner surface of a measuring hole opened along the radial direction of an excavated hole in a shotcrete completed in the execution, and displaying them in a strain meter. SOLUTION: The measuring hole 8 of a circular section is opened along the radial direction of an excavated hole 2 in shotcrete completed in the execution in the inner surface 2 of the hole 2, and a plurality of strain gages 9 are provided mutually deviatedly in the depth directions on the inner surface of the hole 8. A cable 10 and a switch box 11 are connected to the gages 9, and a strain meter 12 displays numeric values corresponding to the outputs of the gages 9. The gages 9 do not disturb at the time of executing the shotcrete 4 to obtain the concrete 4 without failure. Accordingly, the measuring accuracy of the gage 9 is improved, and the execution efficiency of the shotcrete 4 is improved as well.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a stress measuring device for shotcrete, and more particularly to a stress measuring device for shotcrete that measures the stress acting on the shotcrete applied to the inner wall surface of a tunnel.

[0002]

2. Description of the Related Art For example, the NATM method (New Austrian Tunneling Metho), which is often used for construction of mountain tunnels, is used.
For tunnels constructed in d), etc., as shown in Fig. 5,
The sprayed concrete C is applied to the inner wall surface 6 of the excavation pit 2 formed by excavating the natural ground 1 to construct the primary lining. The NATM
In the construction method, conventionally, an internal stress meter K (concrete effective stress meter) is buried during construction of the sprayed concrete C, and the stress acting on the sprayed concrete C in the circumferential direction of the tunnel is measured.

[0003]

By the way, in the case of the internal stress meter K for spraying as described above, after the internal stress meter K for spraying is fixed to a reinforcing bar pile (not shown) arranged in the vicinity of the inner wall surface 6 of the excavation hole. Since the sprayed concrete stress meter K is embedded so that the sprayed concrete C is installed, the sprayed internal stress meter K and the reinforcing bar pile form a blind spot for spraying the sprayed concrete C, and the stress measurement accuracy is reduced. Was causing problems. That is, if the in-spray stress meter K and the reinforced pile interfere with the spraying of the sprayed concrete C, the rebound of the sprayed concrete C increases, and the sprayed in-stress meter K and the reinforced pile installed behind and around the reinforced pile. There may be a case where the density of C becomes lower than that of other portions, and as a result, it may not be possible to expect sufficient measurement accuracy of the internal stress meter K for spraying. Also, the problem is NA
It is not peculiar to the sprayed concrete C for tunnels constructed by the TM method, and may occur in sprayed concrete for various tunnels.

The present invention has been made in view of the above-mentioned problems, and by improving the accuracy of measuring the stress of shotcrete, a stress measuring apparatus for shotcrete that can efficiently construct a tunnel of higher strength. It is intended to provide.

[0005]

The present invention has the following features to attain the object mentioned above. That is, in the stress measuring device for sprayed concrete according to claim 1, the stress measuring device for spraying concrete measures stress acting on the sprayed concrete that is placed on the inner wall surface side of the excavation pit formed by excavating the ground. , A plurality of strain gauges attached to the inner surface of the measurement hole drilled along the radial direction perpendicular to the axial direction of the excavated mine on the shotcrete that has been completed and displaced in the depth direction of the measurement hole, and the strain gauge And a strain meter for displaying the strain corresponding to the output signal based on the above output signal.

The operation of the invention described in each claim will be described below. In the invention according to claim 1, after the construction of the shotcrete is completed, the measurement holes are bored in the shotcrete to attach the strain gauges. Concrete is obtained. Therefore, the accuracy of measuring the strain of the shotcrete with the strain gauge is improved, and the shotcrete can be efficiently constructed. In addition, the strain measurement accuracy can be improved by appropriately changing the shape of the measurement hole and the like.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION An embodiment of a stress measuring device for shotcrete according to the present invention will be described below with reference to FIGS. 1 to 4. In the figure, the same components as those in FIG. 5 are denoted by the same reference numerals, and the description will be simplified. In FIG.
Reference numeral 5 is a stress measuring device for sprayed concrete of the present embodiment (hereinafter referred to as “stress measuring device”). Stress measuring device 5
As shown in FIG. 1 and FIG. 2, the measurement hole 8 is formed on the inner wall surface 6 of the excavation hole in the sprayed concrete 4 along the radial direction of the excavation hole 2 on the inner surface of the measurement hole 8 having a circular cross section. 8, a plurality of strain gauges 9 which are attached to each other in the depth direction and are attached to each other, and a cable 1 connected to the strain gauges 9
0 and a switch box 11, and a strain meter 12 that displays a numerical value corresponding to the output signal of the strain gauge 9 based on the output signal. The measurement hole 8 is
As shown in FIG. 4, it is formed at a position avoiding the supporting steel material 13 embedded in the shotcrete 4. Since the supporting steel materials 13 are continuously provided at a plurality of locations in the axial direction of the excavation pit, the measurement holes 8 are formed in the sprayed concrete 4 between the supporting steel materials 13. The strain gauge 9 is shown in FIGS.
As shown in FIG. 2, a total of two rows of measurement holes 8 arranged in a row in the depth direction of the measurement holes 8 are formed at positions facing each other in the cross-sectional diameter direction of the measurement holes 8.

The operation and effect of this embodiment will be described below. To assemble the stress measuring device 5, first,
The sprayed concrete 4 is sprayed on the inner wall surface 6 of the excavation mine 2 formed by excavating the natural ground 1. At this time, since the strain gauge 9 is not installed, the interference of the spraying of the sprayed concrete 4 is reduced and the construction can be carried out efficiently. next,
A measurement hole 8 is drilled along the cross-sectional radial direction of the excavation pit 2 on the sprayed concrete 4 that has been sprayed using a drilling machine, and a plurality of strain gauges 9 are attached to the inner surface of the measurement hole 8. At this time, the strain gauges 9 are attached so as to form two rows facing each other in the cross-sectional diametrical direction of the measurement holes 8. Also,
As shown in FIG. 1, a cable 10 is attached to each strain gauge 9.
Is attached, and the end of the cable 10 is connected to the strain meter 12 via the switch box 11. The measurement holes 8 can be drilled by a method other than the drilling.

The strain value read from the strain meter 12 is multiplied by 1/3 and used to convert the stress of the shotcrete 4. By doing so, the processing according to the elastic theory solution corresponding to the stress concentration rate (= 3) when the shotcrete 4 having one measurement hole 8 in the middle receives a tensile force or a compressive force that acts uniformly in the circumferential direction. Has been done,
The sensitivity and accuracy of stress measurement can be improved. However, this numerical processing is performed on the assumption that the cross-sectional shape of the sprayed concrete 4 perpendicular to the axial direction is annular, and may be processed in more detail according to the actual cross-sectional shape of the sprayed concrete 4. It is possible. Moreover, the stress in the axial direction of the shotcrete 4 can be ignored.

When the measured stress is expected to exceed the allowable range of the shotcrete 4, as shown in FIG. 3, for example, a shape obtained by line drilling and expanding while shifting the axis in the circumferential direction of the tunnel 1 is used. By forming the measurement hole 8 of, the stress concentration rate is reduced. The stress concentration rate can be easily obtained by a numerical analysis (boundary element method, finite element method, etc.) that models the actual shape of the measurement hole 8, so the inclination angle and shape of the measurement hole 8 should be easily determined. You can

When the stress acting on the sprayed concrete 4 is found, the sprayed concrete 4 and the like are adjusted based on the data so that the stresses acting on the sprayed concrete 4 are balanced as a whole, and the supporting steel material 13 and the sprayed concrete 4 are The primary lining consisting of and is completed. After the primary lining is completed, a cast-in-place concrete (not shown) is placed on the inner surface 14 side of the shotcrete 4 to complete the secondary lining.

The stress measuring device 5 of this embodiment uses a plurality of strain gauges attached along the radial direction of the cross section of the sprayed concrete 4 using the measurement holes 8 drilled in the sprayed concrete 4 that has been completed. Since strain is displayed on the strain meter 12 based on the output signal from 9, the measurement accuracy can be improved and the stress distribution in the radial cross section of the shotcrete 4 can be analyzed. Further, since the accuracy and sensitivity of the measurement can be adjusted by the shape of the measurement hole 8, if the shape is changed according to the shape of the primary lining and the nature of the natural ground 1, it is possible to perform high-precision measurement at all times. is there. Therefore, according to the stress measuring device 5, the accuracy of measuring the stress acting on the shotcrete 4 can be significantly improved. The measurement hole 8 can also be used for checking and observing the occurrence of cracks in the shotcrete 4.

Further, since the strain gauge 9 is attached after the sprayed concrete 4 is completed, a dead zone for spraying the sprayed concrete 4 is not created, so that the sprayed concrete 4 can be installed without causing any trouble. By the way, in most cases, the deformation of the tunnel first occurs in the shotcrete 4, so if the shotcrete 4 can be constructed as planned, the stress acting on the shotcrete 4 will be measured to affect the entire primary lining. The stress can be measured with high accuracy.
Therefore, in the stress measuring device 5 of the present invention, by improving the reliability of the measurement of the sprayed concrete 4, the stress of the entire primary lining can be measured with high accuracy, and a tunnel with higher strength can be efficiently constructed. can do.

The stress measuring device 5 can be applied to sprayed concrete for various tunnels constructed by a method other than the NATM method.

[0015]

As described above, according to the stress measuring device for sprayed concrete of the present invention, the spraying for measuring the stress acting on the sprayed concrete placed on the inner wall surface of the digging pit formed by excavating the natural ground. A stress measuring device for concrete, wherein a plurality of sprayed concrete, which has been completed along the radial direction perpendicular to the axial direction of the digging hole, is attached to the inner surface of the measuring hole while being offset from each other in the depth direction of the measuring hole. Since the strain gauge and the strain meter that displays the strain corresponding to the output signal of the strain gauge according to the output signal of the strain gauge are provided, (1) the measurement accuracy of the stress acting on the shotcrete can be improved. Yes, (2) the stress distribution in the cross-sectional radial direction of shotcrete can be analyzed, and (3) the accuracy and sensitivity of measurement can be adjusted by the shape of the measurement hole, By changing the shape of the measurement hole to correspond to the properties of the shape and the natural ground of the next lining, an excellent effect such it is possible to perform the measurement at all times precision.

[Brief description of drawings]

FIG. 1 is a front sectional view showing a tunnel to which a stress measuring device for shotcrete according to the present invention is applied.

FIG. 2 is a side sectional view of FIG.

FIG. 3 is a front cross-sectional view showing an example of forming a measurement hole.

FIG. 4 is a side sectional view showing a tunnel to which the stress measuring device for shotcrete of the present invention is applied.

FIG. 5 is a front sectional view showing a tunnel to which a conventional stress meter in spraying is applied.

[Explanation of symbols]

 1 rock mass, 2 excavation pits, 4 sprayed concrete, 5 stress measuring device for sprayed concrete, 6 inner wall surface, 8 measuring holes, 9 strain gauge, 12 strain meter.

Claims (1)

[Claims] 1. A spray concrete stress measuring device for measuring a stress acting on a sprayed concrete placed on the inner wall surface side of a drilling pit formed by excavating a rock mass, wherein the drilled pit is formed on the sprayed concrete which has been completed. On the inner surface of the measurement hole drilled along the radial direction perpendicular to the axial direction of the plurality of strain gauges attached to each other in the depth direction of the measurement hole, and to the output signal based on the output signal of the strain gauge A stress measuring device for shotcrete, comprising: a strain meter for correspondingly displaying strain.