JP2014037738A - Load experimental device for test piece of shield tunnel - Google Patents

Abstract

PROBLEM TO BE SOLVED: To load a test piece of a shield tunnel uniformly with a load.SOLUTION: An inventive load experimental device for a test piece 4 of a shield tunnel includes: a pressure device 5 for applying a load to the test piece 4; and a uniform distribution loading plate 1 installed between the pressure device 5 and the test piece 4 and having a contact face with the test piece 4 which has a shape corresponding to the arc of a side face of the test piece 4.

Description

  The present invention relates to a loading test apparatus for loading a load on a test body of a shield tunnel in order to measure how the load is deformed when the load is loaded on a shield tunnel.

  The behavior when a load is loaded on the shield tunnel can be confirmed by structural analysis calculations and experiments that simulate an environment close to a real tunnel. In a conventional experiment, a load cell is used to measure the load applied to the tunnel model. In order to reproduce the peripheral restraint and load loading in the tunnel in the soil, restraint by a tension bar or load loading by a hydraulic jack is performed. And a method of laying a roller to reduce friction between the tunnel and the floor (Non-Patent Document 1).

Murakami Hirotomo and Koizumi Satoshi, “Behavior of the second-lined houndstooth segment”, JSCE Proceedings No.430, pp135-142

  Shield tunnels buried underground cause deformation of the shield tunnel body by receiving external forces from various directions due to pressure from the surrounding ground and load from the road surface. If the surrounding soil is corrosive, such as acidic soil, the strength of the shield tunnel itself will decrease due to the deterioration of the shield tunnel material itself and the decrease in material thickness, and there is a possibility that the shield tunnel will collapse in the future. Since it is assumed that it will increase, it is important to examine the proof stress by reproducing the load and material state on the shield tunnel in advance by experiments.

  However, when a hydraulic jack is used as a method to reproduce the pressure from the surrounding ground, the shield tunnel specimen is circular, so the contact point between the hydraulic jack loading point and the shield tunnel specimen is a single point at the beginning of loading. Since the test specimen of the shield tunnel is flattened as the load is applied, the contact area between the loading point of the hydraulic jack and the test specimen of the shield tunnel increases, resulting in an evenly distributed load such as in the soil. Is difficult to load evenly.

  Also, load cell measurement is used to measure that the load loaded by the hydraulic jack is accurately transmitted to the shield tunnel specimen, and to measure the load received by the shield tunnel specimen from the surrounding restraint simulating the soil. If a load is used that exceeds the allowable load cell capacity during the experiment, or if a load exceeding the proof strength of the shield tunnel specimen is loaded, the shield tunnel specimen will be destroyed. It is assumed that the load cell measuring instrument itself fails. The unit price per load cell measuring instrument is high, and it is difficult to install in a place where destruction is expected. Therefore, where damage is expected, it is possible to use a measurement device that can measure a measurement level equivalent to that of a load cell, although it is possible to use a very low-cost loss even if it is damaged.

In addition, when the main materials of the shield tunnel specimen are steel and concrete, the unit volume weight of steel is 7.8 t / m ³ and the unit volume weight of concrete is 2.3 t / m ^3. Therefore, the total weight becomes several tons. When a shield tunnel specimen is installed and loaded with a hydraulic jack from the side, in order to accurately measure the behavior of the shield tunnel specimen due to the loaded load, the shield tunnel specimen and the floor of the test bench are used. It is important to reduce friction. In the conventional method, there is a method to reduce the friction by installing a roller on the floor and rolling the shield tunnel specimen on the test table, but in this case, it follows the movement in a fixed direction. It is difficult to reduce friction in all directions.

  Accordingly, an object of the present invention made in view of such a point is to provide a loading test apparatus for a shield tunnel specimen capable of evenly loading a shield tunnel specimen.

  In order to solve the above-described problems, a test apparatus for loading a test specimen of a shield tunnel according to the present invention includes a pressurizing apparatus that applies a load to the test specimen, and the pressurizing apparatus and the test specimen. And a uniformly distributed loading plate having a shape corresponding to an arc of a side surface of the test body.

  In addition, a load measuring instrument that supports the uniformly distributed loading plate is provided at a tip of the pressurizing device, and the load measuring instrument includes a steel bar and a strain gauge attached to the steel bar, and the strain gauge It is desirable to measure the load based on the strain amount.

  Moreover, it is desirable to provide a friction reducing plate laid between the test body and the test stand, and the friction reducing plate is a fluororesin processed plate.

  According to the test apparatus for loading a test specimen of a shield tunnel according to the present invention, a load can be evenly loaded on the test specimen of the shield tunnel.

It is a figure which shows an example of the loading experiment apparatus which concerns on one Embodiment of this invention. It is a figure which shows the structure of an equally distributed loading board. It is a figure which shows the structure of a load measuring device. It is a figure which shows the structure of a friction reduction board.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

  FIG. 1 is a diagram illustrating an example of a loading test apparatus according to an embodiment of the present invention. In FIG. 1, the top view which shows the structure of a loading experiment apparatus, and sectional drawing along each of the aa line and bb line are shown. The loading test apparatus supports the evenly distributed loading plate 1 that carries out an evenly distributed loading on the test specimen 4 of the shield tunnel, and the equally distributed loading plate 1 at the tip of the pressurizing device 5. And a friction reducing plate 3 that is laid on the test stand 6 and reduces the friction between the test body 4 and the floor surface. The loading test apparatus shown in FIG. 1 can load a load from four directions by means of four equally distributed loading plates 1 installed in the vertical and horizontal directions with respect to the test specimen 4 of the shield tunnel. However, for convenience of explanation, only the pressure device 5 on the left side of the test body 4 is illustrated. The pressurizing device 5 is, for example, a hydraulic jack, and loads a load on the side surface of the test body 4.

  FIG. 2 is a diagram illustrating a configuration of the equally distributed loading plate 1. The contact surface of the uniformly distributed loading plate 1 with the test body 4 has a shape corresponding to the arc of the side surface of the test body 4. The equally distributed loading plate 1 is installed between the pressurizing device 5 and the test body 4, and in particular, supported by the load measuring instrument 2 at the tip of the pressurizing device 5. For example, the equally distributed loading plate 1 is supported at the tip of the pressurizing device 5 by eight load measuring devices 2. When the pressurizing device 5 applies a load to the side surface of the test body 4, it becomes possible to load the test body 4 evenly by the evenly distributed loading plate 1. For this reason, the problem of the one point concentrated load when the load of the pressurizing device 5 that is a conventional problem is directly loaded does not occur, and a uniform load that is closer to the actual environment than the image of the soil is added to the specimen 4. Is possible.

  FIG. 3 is a diagram showing the configuration of the load measuring device 2. The load measuring instrument 2 is obtained by attaching a strain gauge 21 to a steel bar 20, and the strain gauge 21 is connected to a measuring unit 23. For example, as shown in FIG. 2, both end portions of the load measuring device 2 are embedded in the pressurizing device 5 and the equally distributed loading plate 1, respectively. The load measuring instrument 2 is provided with a notch 22 for facilitating tightening with a wrench or the like. The steel rod 20 is made of, for example, SCM435 or an equivalent material. The measurement unit 23 is, for example, a computing device including a processor and a memory, and stores the relationship between the strain amount of the strain gauge 21 measured in advance and the loaded load, and the strain gauge 21 actually measured is measured. The applied load transmitted from the pressurizing device 5 to the equally distributed loading plate 1 is measured from the strain amount. Here, the number of strain gauges 21 attached to the steel rod 20 is not limited to one, and a plurality of strain gauges 21 can be attached to the steel rod 20. For example, when a plurality of strain gauges 21 are attached to the steel rod 20, the measurement unit 23 measures the applied load transmitted from the pressurizer 5 to the equally distributed loading plate 1 from the average value of the strain amount of each strain gauge 21. be able to. By using the load measuring device 2 in which the strain gauge 21 is attached to the steel bar 20, the cost of the measuring device can be greatly reduced as compared with load measurement using a conventional commercially available load cell. In particular, as a measuring instrument, it is possible to reduce damage loss due to a sudden load from a jack during measurement while ensuring sufficient measurement accuracy.

  FIG. 4 is a diagram showing the configuration of the friction reducing plate 3. The friction reducing plate 3 is a fluororesin processed plate and is laid between the test body 4 and the test table 6. The fluororesin is superior in heat resistance, chemical resistance and weather resistance as compared with other polymer materials, and further has properties such as non-adhesiveness and low friction. The friction reduction plate 3 is, for example, a Teflon (registered trademark) sheet, and a plurality of Teflon (registered trademark) sheets can be used in an overlapping manner. By laying the friction reducing plate 3 between the test body 4 and the test table 6, the friction between the test body 4 and the floor surface is reduced, and extra force other than the load applied to the test body 4 during the experiment is reduced. Therefore, it is possible to improve the measurement accuracy of the loaded load.

  Although the present invention has been described based on the drawings and examples, it should be noted that those skilled in the art can easily make various modifications and corrections based on the present disclosure. Therefore, it should be noted that these variations and modifications are included in the scope of the present invention. For example, the functions included in each component can be rearranged so as not to be logically contradictory, and a plurality of components can be combined into one or divided.

DESCRIPTION OF SYMBOLS 1 Uniform load board 2 Load measuring device 20 Steel bar 21 Strain gauge 22 Notch part 23 Measuring part 3 Friction reduction board 4 Test body 5 Pressurizer 6 Test stand

Claims (3)

A test equipment for loading a shield tunnel specimen,
A pressure device for applying a load to the specimen;
A loading experiment apparatus comprising: an evenly distributed loading plate which is installed between the pressurizing device and the test body and whose contact surface with the test body has a shape corresponding to an arc of a side surface of the test body. A load measuring instrument that supports the equally distributed loading plate at the tip of the pressurizing device;
The loading test apparatus according to claim 1, wherein the load measuring instrument includes a steel bar and a strain gauge attached to the steel bar, and measures the load based on a strain amount of the strain gauge. Comprising a friction reducing plate laid between the test body and the test bench;
The loading test apparatus according to claim 1, wherein the friction reduction plate is a fluororesin processed plate.

Images