JP6112663B2 - In-situ rock test method and test equipment - Google Patents

Description

  The present invention relates to an in-situ rock test method and test apparatus, and more specifically, the deformation characteristics and strength characteristics of an anisotropic rock can be investigated or specified by an in-situ loading test in a simple shear mode. The present invention relates to an in-situ rock mass test method and test apparatus that can be used.

  As a test method to examine the mechanical properties of rock mass by in-situ test, rock shear test (rock shear test and block shear test (JGS3511-2004 standard) that applies external force or load such as shear force to the outcrop portion of the specimen) ), Plate loading test (Geotechnical Society standard: JGS3521-2004), in-situ rock triaxial test (Patent No. 4043568 (Patent Document 1), rock torsional shear test (ISRM, 1974 (Non-Patent Document 1)) In addition, as this type of in-situ test, a hole bottom triaxial test (Patent No. 4043568 (Patent Document 1)) that applies an external force to the test body in the bore hole, or pressure Meter tests (geological engineering society standard: JGS 3531-2004) etc. are known.

  Further, as a test for applying a tensile load to a test body and examining deformation characteristics and strength characteristics (tensile strength) at the time of tensile loading, an in-situ tensile test similar to the in-situ rock triaxial test is disclosed in JP2011-107049A. No. 2 (Patent Document 2).

  Regarding the dynamic characteristics (deformation characteristics and strength characteristics) of rock mass considering repeated loading during an earthquake, the shear mode specified according to the test method is examined by repeated loading in the above-mentioned in-situ rock mass test. It may be possible. However, this is not a simple shear mode in situ rock test.

  On the other hand, a simple shear mode test is known in a laboratory dynamic test in which a rock sample sampled from a rock is used as a specimen. As the indoor mechanical tests in the simple shear mode, for example, the simple shear test (Geotechnical Society, 2009), the hollow torsional shear test (Geotechnical Society standards: JGS 0543-2009, 0551-2009 (non-patent document 2)), Multistage ring shear test (Ishikawa et al., 2011 (non-patent document 3): Tanaka et al., 2001 (non-patent document 4)). An anisotropy evaluation method for evaluating the anisotropy of deformation characteristics assuming an in-plane isotropic elastic body is also known by a triaxial test on a single cylindrical specimen (Gonzaga et al., 2008 (Non-Patent Document 5)). However, in the indoor mechanics test, there is a disturbance of the collected sample, the influence of the size effect, etc., so it is difficult to appropriately evaluate the mechanical properties of the rock constituting the ground by the indoor mechanics test. That is, the in-situ rock test that directly performs a mechanical test on the rock constituting the ground and the indoor mechanical test using the rock sample after sampling are different tests.

Japanese Patent No. 4043568 JP 2011-107049 A

ISRM: Suggested method for in situ determination of shear strength using a torsional shear test, 1974 Geotechnical Society: Geotechnical material testing method and explanation, pp.797-798, 2009 Ishikawa, T., Sekine, E. and Miura, S .: Cyclic deformation of granular material subjected to moving-wheel loads, Can. Geotech. J., Vol. 48, No. 5, pp. 691-703, 2011 Kenta Tanaka, Naoto Suemasa, Toshiyuki Katada: Liquefaction test of clay-mixed sand using a multi-stage ring type testing machine, 36th Geotechnical Research Conference, pp.407-408, 2001 Gonzaga, GG, Leite, MH and Corthesy, R .: Determination of anisotropic deformability parameters from a single standard rock specimen, Int. J. of Rock Mech. And Min. Sci., Vol. 45, No. 8, pp. 1420 -1438, 2008

  As described above, the conventional in-situ rock test method was unable to investigate the dynamic characteristics of the rock in the simple shear mode, nor could it identify the deformation and strength characteristics of the anisotropic rock. . Hereinafter, this point will be further described.

(1) Simple shear mode

  The mechanical properties of the ground material depend on the deformation (or strain) and how to apply the load (or stress), that is, the shear mode.

  A simple shear mode, which is a type of direct shear mode, is a mode in which an element is shear-deformed in a certain direction and a uniform shear deformation is generated in the element. The single shear mode is a shear mode that causes a uniform shear deformation within the element, whereas the box shear mode shears on one fixed surface.

  The simple shear mode at the time of repeated loading is considered to be the closest to the state of the ground element at the time of earthquake, that is, the state in which repeated shear stress acts on the horizontal plane due to the S wave propagating vertically upward under a constant upper loading pressure. It is done. For this reason, the deformation characteristics of the ground (such as the shear rigidity G and the relationship between the damping constant h and the shear strain γ) are very important for evaluating the deformation and stability of the ground during an earthquake.

  However, there is no simple shear mode test in the conventional in situ rock test. That is, the rock shear test (rock shear test and block shear test) and the rock torsional shear test are single-sided shear modes, and the in-situ rock triaxial test, in-situ tensile test and hole bottom triaxial test are the principal stress axes. This is an axially symmetric triaxial mode in which is fixed. In addition, the flat plate loading test and pressure meter test are not elemental tests, but only a rigid plate loading mode on a semi-infinite horizontal ground and an axial object condition, or a circular hole expansion mode under an axially symmetric plane strain condition. .

  In the laboratory dynamics test, simple shear mode tests (simple shear test, hollow torsional shear test, multi-stage ring shear test) are carried out, but not only there is a problem of sample disturbance due to sampling, Since the specimen size is limited to relatively small dimensions, there is a problem of dimensional effects. For this reason, for rock masses that need to take into account the effects of inhomogeneities and discontinuities, the mechanical properties are appropriate. Cannot be evaluated. Further, in the multi-stage ring shear test, discontinuity occurs at the boundary position of the ring, and there is a problem that the continuity of the deformation of the specimen cannot be obtained in the height direction and the shear stress acts on the side surface.

(2) About the absence of a simple and inexpensive method for examining anisotropy in the past

  In the conventional in-situ rock test, the mechanical characteristics in the principal stress direction (or principal strain direction) determined according to the test method (the shape of the specimen and the loading method) by a single test on a single specimen. Can only be evaluated. For this reason, in order to investigate the anisotropy related to the dynamic characteristics of the rock mass, it is necessary to change the direction and perform the same test method a plurality of times. For example, in the rock shear test (rock shear test and block shear test), flat plate loading test, in-situ rock triaxial test, in-situ tensile test, and rock torsional shear test, multiple specimens with different directions are prepared. Similar tests need to be repeated.

  In addition, in order to investigate the anisotropy related to the dynamic characteristics of rock mass by the hole bottom triaxial test or the pressure meter test, it is necessary to repeat the test in a plurality of boreholes drilled in different directions. On the other hand, in the hydrostatic pressure test using a hollow cylindrical specimen, if the strain of the number of measurement points sufficient to calculate the six components of the strain tensor is measured, the rigidity anisotropy may be specified. Since it is a test under isotropic stress, the strength anisotropy cannot be specified.

  Furthermore, in conventional rock shear tests (rock shear test and block shear test), in-situ rock triaxial test, in-situ tensile test, and rock torsional shear test, excessive bending stress and Performing an in-situ test using a specimen whose central axis is greatly deviated from the vertical direction (for example, a specimen whose central axis is tilted by 20 degrees or more with respect to the vertical direction) due to the shear stress acting. It is extremely difficult.

  That is, in the conventional in-situ rock mass test, it is necessary to perform the test several times or many times in order to investigate the anisotropy related to the dynamic characteristics of the rock mass. There is a problem that the cost is increased and the test itself is difficult depending on the test method.

  The present invention has been made in view of such circumstances, and the object of the present invention is to make it easy to determine the deformation characteristics and strength characteristics of an anisotropic rock mass by an in-situ loading test in a simple shear mode. An object of the present invention is to provide an in-situ rock test method and test apparatus that can be investigated or specified in a short time.

In order to achieve the above object, the present invention excavates or drills a rock head outcrop or a bottom portion of a borehole to form a hollow cylindrical specimen in its original position, and loads the specimen on the load. In-situ rock test method to examine or specify the deformation characteristics and strength characteristics of the test body,
A cap or lid having a measuring means for measuring a direct stress and a shear stress is disposed on the top or upper end of the test body,
By simultaneously loading an axial load in the direction of the central axis of the specimen and a moment about the central axis of the specimen on the cap or the lid, the axial load and the moment act on the specimen via the cap. Cough,
By detecting the direct stress and shear stress acting on the boundary between the cap or lid and the top surface or the upper surface of the test body by the measuring means, and obtaining the circumferential distribution of the direct stress and the shear stress, In-situ rock mass testing method characterized by examining or identifying the deformation characteristics and strength characteristics of rock mass.

  According to the above configuration of the present invention, the direct stress and the shear stress acting on the boundary between the bottom surface of the cap or the lid and the top surface or the top surface of the test body are detected by the measuring means, and the direct stress and the shear stress circle are detected. Circumferential distribution is obtained. As a result, the anisotropy of the rock mass can be obtained, and the deformation characteristics and strength characteristics of the anisotropic rock mass can be obtained.

The present invention also provides a loading device for loading a hollow cylindrical test body formed in situ by excavating or drilling a rocky outcrop or a hole bottom portion of a borehole, and deformation characteristics of the test body and In-situ rock test apparatus having a measuring means for detecting stress acting on the test body in order to examine or specify strength characteristics,
A cap or lid having measuring means for measuring direct stress and shear stress is disposed on the top or upper end of the test body,
The aforementioned loading device is configured to simultaneously load an axial load and a moment on the test body via the cap or the lid,
The measuring means has a plurality of measuring units or measuring devices for detecting a direct stress or axial load and a shear stress or a shear load acting on a boundary between the cap or lid and the top surface or the upper surface of the test body. ,
The measuring unit or measuring instrument is arranged in the circumferential direction on the top surface or the upper surface of the test body.

  According to the above configuration of the present invention, the direct stress (or axial load) and the shear stress (or shear load) acting on the boundary between the bottom surface of the cap or the lid and the top surface or the top surface of the test body are a plurality of measurements. It is detected by a part or a measuring instrument. Based on the detection results of the measuring unit or measuring instrument, the circumferential distribution of direct stress and shear stress is obtained, thereby obtaining the anisotropy of the rock mass and the deformation characteristics and strength characteristics of the rock mass having anisotropy. be able to.

  Preferably, the cap or the bottom surface of the lid contacting the top surface of the test body is equally divided into a plurality of sections in the circumferential direction. The measuring unit or measuring instrument includes a load cell for detecting a direct stress or axial load acting on each section and detecting a torsional direction shear stress or shear load acting on each section. The output of the load cell is input to a control device or control system such as a control unit or PC constituting the recording means, and the circumferential distribution of the direct stress acting on the upper surface of the specimen and the circle of the shear stress in the torsional direction. A circumferential distribution is required. The anisotropic mechanical properties of the rock mass are evaluated based on the stress distribution thus obtained. In the evaluation of the mechanical characteristics, a constitutive model that appropriately considers anisotropy is assumed from the circumferential distribution of the obtained stress, and ground parameters describing the constitutive model are obtained by inverse analysis. Examples of constitutive models include, but are not limited to, in-plane isotropic (traverse isotropy).

  The division number n of the bottom surface of the cap or the lid can be preferably set to a division number of at least 6 divisions, preferably 8 divisions or more. Thereby, the shape of the stress distribution can be specified with high accuracy, and the anisotropy of the dynamic characteristics of the rock can be accurately evaluated.

  If desired, an inner cell and an outer cell are formed on the radially inner side and the radially outer side of the specimen. Each cell is defined by a rubber film, and fluid pressure acts on a region in each cell. The axial load and moment act on the test body in a state where the direct stress due to fluid pressure acts on the test body, and the axial displacement and the torsional displacement in the circumferential direction act on the test body. Preferably, the direct stress acting on the inner surface and the outer surface of the test body is set to an equal pressure value. The loading may be a displacement control (or strain control) method or a load control (or stress control) method. Moreover, loading can be performed not only as monotonous loading but also as repeated loading.

Preferably, since it is assumed that the deformation mode of the specimen is the simple shear mode, the inner diameter / outer diameter ratio (d _in / d _out ) of the specimen is 1.0> d _in / d _out ≧ 0.6 Is set within the range. When such an inner diameter / outer diameter ratio is adopted, it is possible to analyze the test results on the assumption that the radial distribution of shear stress and shear strain acting on the upper surface of the test body is uniform in the section. .

More preferably, the height / outer diameter ratio (h _s / d _out ) of the specimen is set to a value of 0.5 or more. In the above in-situ test, the surrounding rock mass continues to the lower end of the test body. By adopting such a height / outer diameter ratio, the influence of the surrounding rock mass on the test result can be reduced.

The size of the test specimen should be the size that can represent the heterogeneity and discontinuity of the rock mass, and the size that can reduce the curvature of the cylindrical cross section. The outer diameter d _out is set to at least 100 mm, and preferably set to a dimension in the range of 200 to 600 mm.

  Preferably, the load loading apparatus includes an axial load loading apparatus for loading an axial load on the test body and a moment loading apparatus for loading a moment on the test body. The axial load loading device and the moment loading device output the axial load and moment to the cap or the lid, and the cap or lid transmits the axial load and the moment to the upper end of the test body via the measuring unit or the measuring instrument. .

  According to the in-situ rock mass testing method and test apparatus of the present invention, it is possible to investigate or specify the deformation characteristics and strength characteristics of anisotropic rock mass relatively easily and in a short time by an in-situ loading test in a simple shear mode. it can.

FIG. 1 is a longitudinal sectional view and a transverse sectional view showing an outline of an in-situ rock torsional shear test according to the present invention. FIG. 2 is a longitudinal sectional view and a transverse sectional view showing the outline of the in-situ rock torsional shear test according to the present invention, as in FIG. FIG. 3 (A) is a longitudinal sectional view schematically showing the structure of the in-situ rock test apparatus, and FIGS. 3 (B) to 3 (D) are plan views schematically showing the structure of the load cell unit, It is a bottom view and a side view. FIG. 4 is a longitudinal sectional view showing an embodiment in which a test is carried out at the hole bottom using the test apparatus of the system shown in FIG. FIG. 5 is a diagram illustrating changes in pressure and load during an isotropic consolidation process and a torsional shear process during a loading test. FIG. 6 is a longitudinal sectional view schematically showing an aspect in which the specimen is separated and collected after the end of the loading test. FIG. 7A is a plan view showing the arrangement of the load cells, and FIG. 7B is a longitudinal sectional view showing the positional relationship between the load cells and the test body, and FIG. 7C and FIG. ) Is a diagram illustrating the distribution of axial load and moment detected by each load cell. FIG. 8 is a plan view and a development view illustrating the arrangement of strain gauges. FIG. 9 is a flowchart showing a procedure for obtaining the deformation anisotropy of the rock mass assuming in-plane isotropicity. FIG. 10 is a conceptual diagram showing anisotropic directions (x ′, y ′, z ′) with respect to the EWSN orientation system. FIG. 11 is a diagram showing how the orthogonal coordinate system (X, Y, Z) is set. FIG. 12 is a diagram showing the relationship between the specimen and the coordinate axes. FIG. 13 is a diagram illustrating a method for setting the direction of anisotropy. FIG. 14 is a diagram illustrating the distribution of the measured direct stress.

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

  FIG. 1 is a longitudinal sectional view and a transverse sectional view showing an outline of an in-situ rock torsional shear test according to the present invention, and a process for producing a specimen is schematically shown in FIG.

  FIG. 1 (A) shows the outcrop of the rock M to be subjected to the in-situ test. The ground surface Ma is smoothly shaped using excavation / drilling means such as a disk-type bit. The ground surface Ma after shaping constitutes the upper surface of the hollow cylindrical specimen SP shown in FIGS. 1 (D) and 1 (E). The ground surface Ma of the rock mass M may be the bottom Md (FIG. 4) of the excavation hole drilled by the boring operation.

  In FIG. 1 (A), a center hole 2 having a circular cross section to be drilled in the rock mass M is indicated by a broken line. The center hole 2 is drilled perpendicularly to the ground surface Ma as shown in FIG. 1B by a drilling means such as a core barrel 5 provided with a disk-type bit 4. The center hole 2 has a true circular cross section with a predetermined diameter centered on the vertical center axis C.

  In FIG. 1 (B) and FIG. 1 (C), the outer peripheral groove 3 to be drilled in the rock mass M is indicated by a broken line. The outer peripheral groove 3 is drilled in the rock mass M concentrically with the center hole 2 by a drilling means such as a core barrel 7 provided with a disk-type bit 6. The outer peripheral groove 3 is also drilled perpendicularly to the ground surface Ma after shaping, and the inner peripheral surface and the outer peripheral surface of the outer peripheral groove 3 have a true circular cross section with a predetermined diameter centered on the central axis C.

By drilling the coaxial central hole 2 and the outer peripheral groove 3, a hollow cylindrical specimen SP whose bottom is continuous with the rock mass M is obtained as shown in FIGS. 1 (D) and 1 (E). Molded in-situ. The test body SP has a top surface Sa, an inner surface Sb, and an outer surface Sc that are smoothly finished. The upper surface Sa is a horizontal plane orthogonal to the central axis C, the inner surface Sb is a true circular inner peripheral wall surface having a diameter d _in with the central axis C as the center, and the outer surface Sc is centered on the central axis C. It is a true circular outer peripheral wall surface with a diameter d _out . In the present embodiment, the specimen SP has a cylindrical contour centered on the vertical center axis C, but the center axis C can be inclined. The inclination of the central axis C is desirably set to an angle within a range in which excessive bending stress or shear stress does not act on the specimen due to the influence of its own weight. The inclination of the central axis C can be preferably set to an angle in which the inclination angle of the central axis C with respect to the vertical direction is less than 20 degrees, but the inclination angle of the central axis C is set to an angle of 20 degrees or more as desired. It is also possible.

In order to assume that the deformation mode of the specimen SP is the simple shear mode in the loading test described later, it is desirable to reduce the difference in curvature between the inner surface Sb and the outer surface Sc to make the shear stress distribution uniform. In this embodiment, the inner diameter / outer diameter ratio (d _in / d _out ) is set to a value of 0.6 or more (1.0> d _in / d _out ≧ 0.6). However, if an analysis method that does not make such an assumption is used, the inner diameter / outer diameter ratio (d _in / d _out ) can be set to a value of 0.6 or less. As an extreme condition, when the inner diameter d _in is zero (d _in / d _out = 0), the specimen SP is a solid cylinder, and therefore the center hole 2 and the inner cell 20 (FIG. 2) can be omitted. Therefore, the structure of the test apparatus 1 and the test procedure (workability) can be simplified. However, the value of the shear stress acting on the upper surface Sa of the specimen and the shear strain in the torsional direction is substantially zero at the central axis C. Therefore, the radial distribution of the shear stress and the shear strain is , Not uniform. For this reason, in such a case, it is considered necessary to employ an analysis method that appropriately considers the influence of non-uniformity of shear stress and shear strain.

In consideration of the dimensional effect of the dynamic characteristics of the rock mass, it is desirable to set the outer diameter d _out of the specimen SP to 100 mm or more, and considering the economic rationality of the test, the outer diameter d _out is 200 mm. It is desirable to set the dimensions to about 600 mm. However, from the viewpoint other than the economic rationality, it is possible to set the outer shape d _out > 600 mm.

In view of the dimensional balance in the height direction and the radial direction of the test body SP, in order to assume that the test body SP is deformed in a substantially uniform simple shear mode, the test body SP has a cylindrical body from the upper end of the cylindrical body. It is desirable that the height dimension h _s of the lower end section is 0.4 times or more of the outer diameter d _out . Preferably, the height / outer diameter ratio (h _s / d _out ) of the test specimen SP is 0.5 or more (1) in consideration of the effect of the lower end of the test specimen SP continuing to the surrounding rock mass M. 0.0> h _s / d _out ≧ 0.5).

  FIG. 2 is a longitudinal sectional view and a transverse sectional view showing an outline of the in-situ rock torsional shear test according to the present invention, as in FIG. FIG. 2 schematically shows a state in which the apparatus 1 ”is installed on the specimen SP.

  As shown in FIG. 2, the test apparatus 1 according to the present embodiment includes a cap or lid 10 (hereinafter referred to as “cap 10”) installed on the upper surface of the test specimen SP and an interior installed in the center hole 2. The cell 20 and the outer cell 30 installed in the outer peripheral groove 3 are included.

  The inner cell 20 is formed by an annular rubber film 21 that is inserted into the center hole 2 and covers the inner side surface Sb of the specimen SP. The outer cell 30 includes an annular rubber film 31 that is inserted into the outer circumferential groove 3 and covers the outer surface Sc of the specimen SP, and an annular rubber film 32 that is inserted into the outer circumferential groove 3 and covers the inner circumferential wall surface Mb of the rock M. Formed by. End fixing means (not shown) for fixing both ends of the rubber films 21, 31, 32 do not restrain the axial displacement (compression / extension) and torsional displacement of the test specimen SP, and the displacement of the test specimen SP. It has a structure that can follow. Since the test apparatus 1 has a structure in which the inner peripheral wall surface Mb is covered with the rubber film 32, the reaction force of the rock mass M is used to reduce the rigidity and strength of the test specimen SP, and the test specimen SP is thin and light. Can be. The cap 10 has sealing means (not shown) for sealing the fluid of the inner cell 20 and the outer cell 30 in the cell.

The inner cell 20 and the outer cell 30 are connected to a fluid pressure supply source (not shown) of the cell pressure supply device via the fluid line 8. A pressure gauge 9 is interposed in the fluid conduit 8. The fluid as the pressure supply medium may be a hydraulic fluid that supplies hydraulic pressure such as hydraulic pressure or compressed air that supplies pneumatic pressure. However, in consideration of controllability and safety, the fluid depends on the hydraulic fluid. A pressure supply system can be preferably employed. Fluid pressure source is a fluid pressure is supplied to the inner cell 20 and an outer cell 30, lateral pressure (normal stress) and lateral pressure (normal stress) caused to act on P _in the inner surface Sb of the specimen SP P _out the specimen SP The side pressure loading means or the restraining pressure loading means that is applied to the outer side surface Sc is configured. In the present embodiment, a water pressure source and a water pressure are used as the fluid pressure source and the fluid pressure.

In the case of the simple shear mode test, the pressure P _in of the inner cell 20 and the pressure P _out of the outer cell 30 are set to the same value (P _in = P _out ), so that a single cell pressure supply device ( The inner cell 20 and the outer cell 30 can be pressurized by a not shown). However, when examining the influence of the intermediate principal stress, it is desirable that both can be controlled independently (P _in ≠ P _out ).

  FIG. 3A is a longitudinal sectional view schematically showing the structure of the test apparatus 1, and FIG. 4 is a test conducted at the hole bottom using a test apparatus 1 ′ equivalent to the test apparatus 1 shown in FIG. It is a longitudinal cross-sectional view which shows the mode to do.

FIG. 3A shows a test apparatus 1 having a structure suitable for performing a test on the outcrop of the rock mass M or the shallow part of the bottom surface of the survey mine. The test using the test apparatus 1 is generally limited to tests with a depth of 2 m or less, but not only a medium-scale test (200 mm ≦ d _out <400 mm) but also a relatively large-scale test (400 mm ≦ d _out ). It is also possible to implement. According to such a medium-scale or large-scale test, the representativeness or reliability of the test results relating to the physical properties of the rock mass M can be improved. In such a shallow depth test, the design of the test apparatus 1, the construction of the measurement system, the test procedure (production of the test specimen SP, various operations such as setting of the test apparatus 1), etc. Compared to tests performed at the bottom, the test can be performed quickly and easily.

  The test device 1 includes an axial load loading device 11 and a moment loading device 12. The axial load loading device 11 loads a load in the axial direction (compression / extension direction) on the upper surface Sa of the test specimen SP via the cap 10, and the moment loading device 12 has a torsional moment (torque) around the central axis C. ) Is loaded. The loading devices 11 and 12 have a function capable of controlling the loading load or moment at a constant loading rate (or stress rate) and displacement rate (or strain rate), and a function of performing not only monotonous loading but also repeated loading and the like. It is desirable to have As a power source for the loading devices 11 and 12, a fluid pressure such as hydraulic pressure or pneumatic pressure, or a mechanical drive source such as an electric motor can be preferably used, but a predetermined torsional moment (torque) can be secured. For example, it is possible to use a manual loading mechanism. In the present embodiment, the fluid pressure of the fluid pressure actuated cylinder devices 13 and 14 is employed as a drive source for the loading devices 11 and 12. In addition, although the maximum fluid pressure of the loading apparatuses 11 and 12 is determined by the test conditions, the general pressure of the rock mass M constituting the specimen SP may be taken into consideration, and the pressure may be set to about several MPa to 20 MPa. it is conceivable that.

  The reaction force of the axial load can be secured by the outcrop of the rock mass M or the top or side of the survey mine. In the test apparatus 1 shown in FIG. 3A, a temporary structure such as a test pile pile or a temporary mount located above the test apparatus 1 is used as an axial load support means for securing a reaction force of a vertical load (axial load). Alternatively, a reaction body N made of a boring machine or a vehicle body can be used. Further, in the test apparatus 1 shown in FIG. 3A, a mooring hole Mc into which the column 51 can be inserted is drilled in the rock mass M as a moment support means for ensuring a reaction force of the moment (torque). The support column 51 is inserted into the mooring hole Mc, and the mooring material 52 for mooring such as grout material is filled into the mooring hole Mc. Thereby, the support column 51 is firmly supported by the rock mass M. The end portion of the loading frame 50 is fixed to the upper end portion of the support column 51, and the loading frame 50 is installed in the upper area of the ground surface Ma. It is possible to share the same reaction force body as the axial load support means and the moment support means.

  The axial load loading device 11 has a fluid pressure actuated cylinder device 13 connected to a working fluid source (not shown) via a fluid pressure control circuit (not shown). The cylinder housing of the cylinder device 13 is integrally supported by the reaction force body N. The cylinder device 13 includes a piston rod 15 that is aligned on the central axis C. The moment loading device 12 has a fluid pressure operated cylinder device 14 connected to a working fluid source (not shown) via a fluid pressure control circuit (not shown). The cylinder housing of the cylinder device 14 is integrally supported by the loading frame 50. The cylinder device 14 includes a horizontal piston rod 16 connected to the rotating body 17. The central axis of the piston rod 16 is connected to the rotating body 17 at a position eccentric with respect to the rotation center (central axis C) of the rotating body 17.

  The piston rod 15 of the cylinder device 13 extends vertically downward through the rotating body 17, and the lower end portion of the piston rod 15 is connected to the center portion of the cap 10. The piston rod 15 is fixed, engaged or fitted to the rotating body 17 so that torque can be transmitted. The piston rod 15 rotates integrally with the rotating body 17 in accordance with the rotation of the rotating body 17.

  The cylinder device 13 of the axial load loading device 11 loads the axial load Q onto the cap 10 by the expansion and contraction of the piston rod 15, and the axial load Q is transmitted to the specimen SP via the cap 10. The axial load Q is a concept including both a compression load and an extension (tensile) load, and the cylinder device 13 can output both the compression load and the extension (tensile) load to the cap 10. In FIG. 3, the axial load Q acting on the test specimen SP as a compressive load is indicated by an arrow.

  The cylinder device 13 of the moment loading device 12 outputs a moment (torque) T around the central axis C to the rotating body 17 by the expansion and contraction of the piston rod 16, and the rotating body 17 transmits the input moment T to the piston rod 15. To do. The piston rod 15 transmits the moment T to the cap 10. The moment T is controlled in both the clockwise and counterclockwise directions. In FIG. 3A, the counterclockwise moment T acting on the rotating body 17 is indicated by an arrow.

  FIGS. 3B to 3D are a plan view, a bottom view, and a side view schematically showing the structure of the load cell unit LU constituting the cap 10. The portion of the cap 10 that does not substantially participate in load transmission is indicated by a broken line in FIG.

  The cap 10 has a load cell unit LU made of a generally rigid disk or cylinder. The load cell unit LU constitutes a measuring unit that measures the direct stress and the shear stress. The load cell unit LU includes an upper rigid disc LA integrally connected to the lower end portion of the piston rod 15, a lower annular band LB divided into a number of rigid sectors Lb, a disc La and each rigid sector. It is composed of a number of load cells LC interposed between Lb. Between adjacent rigid sectors Lb, a gap Lg having a predetermined size for avoiding interference between the rigid sectors Lb is formed. The dimension of the gap Lg is set to about 1 mm. The load cell LC constitutes a measurement unit or a measurement device that detects direct stress and shear stress.

  The bottom surface of each rigid sector Lb is in close contact with the upper surface Sa of the specimen SP. The axial load and shear load output from the loading devices 11 and 12 are transmitted to the upper surface Sa via the rigid disk LA, the load cell LC, and the rigid sector Lb. Each load cell LC includes a two-way load cell that detects a direct stress and a shear stress acting on the upper surface Sa. The load cell LC and the rigid sector Lb divide the boundary surface of the cap 10 in contact with the upper surface Sa into a plurality of sections in the circumferential direction, and each load cell LC detects a direct stress and a shear stress acting on each section. Therefore, the stress distribution of the direct stress and the shear stress acting on the upper surface Sa can be detected by the group of load cells LC.

  Preferably, the axial load (or direct stress) and the shear load (or shear stress) are reliably transmitted from the bottom surface of the cap 10 to the upper surface Sa, and the boundary surface between the specimen SP and the rigid sector Lb, and the specimen SP In order to prevent destruction in the vicinity of the upper surface Sa, a contrivance or unevenness is formed on the bottom surface of the rigid sector Lb, or a device for increasing the roughness of the bottom surface of the rigid sector Lb is devised. If desired, measures or improvements such as bonding the boundary surface between the rigid sector Lb and the specimen SP, reinforcing the vicinity of the upper surface of the specimen SP, or embedding anchor bolts or the like in the upper surface Sa of the specimen SP are taken. Also good. When the axial load (or direct stress) is a tensile load (tensile stress), it is necessary to employ means for preventing separation between the bottom surface of the rigid sector Lb and the top surface Sa of the specimen SP.

  The control system of the test apparatus 1 includes a control unit CU connected to each load cell LC via a control signal line indicated by a two-dot chain line in FIG. The control unit CU has a function of storing or recording the detection result of each load cell LC. Control units or drive units 13a and 14a of a fluid pressure control circuit (not shown) for controlling the operation of the cylinder devices 13 and 14 are connected to the control unit CU via a control signal line. A load meter LD for measuring all axial loads and all moments acting on the entire upper surface Sa of the test body SP is disposed on the top of the cap 10, and the load meter LD is also connected to the control unit CU via the control signal line. Connected to. The measurement result of the load cell LD can be used for confirming the measurement result as the resultant force of the distributed load measured by each load cell LC.

Strain gauges 41 and 42 for measuring strain (displacement) of the test specimen SP are attached to the inner surface Sb and the outer surface Sc of the test specimen SP. The outputs of the strain gauges 41 and 42 are input to the control unit CU via a control signal line (not shown). Further, the pressure gauge 9 in the fluid conduit 8 measures the pressures P _in and P _out of the inner cell 20 and the outer cell 30. The output of the pressure gauge 9 is also input to the control unit CU. In addition, the test apparatus 1 includes a rotation angle meter or the like (not shown) as measurement equipment, and outputs from these measurement equipment are also input to the control unit CU. If desired, the control system of the test apparatus 1 includes measurement means for measuring the pore water pressure of the test specimen SP.

  FIG. 4 shows an embodiment in which a test is performed at the hole bottom using a test apparatus 1 ′ equivalent to the test apparatus 1 shown in FIG. The test apparatus 1 ′ has a structure suitable for performing a test at the bottom of the bore hole B.

When the test body SP is prepared on the bottom surface (hole bottom) of the boring hole B and the test is performed, the test can be performed in a depth range of 2 m or more. In such a depth region test, a test using a small-scale specimen SP (100 mm ≦ d _out <200 mm) is generally performed. In such a deep depth test, compared to the test performed on the outcrop of the rock mass M (FIG. 3A), the design of the test apparatus 1 ′, the construction of the measurement system, the test procedure (of the specimen SP) In general, it is difficult to perform such operations as manufacturing and setting of the test apparatus 1 ′. In addition, as described above, since the test is limited to those using a relatively small specimen SP, the representativeness or reliability of the test results relating to the physical properties of the rock mass M is outcrop considering the size effect. It may be slightly inferior to the test in the section (FIG. 3A).

  As shown in FIG. 4, the loading devices 11 and 12 are disposed in the bored hole B. The loading frame 50 that supports the moment loading device 12 is frictionally supported, fixed, or moored on the hole wall Ba of the hole B, whereby a reaction force of the moment (torque) T is obtained. The cylinder device 13 of the axial load loading device 11 has a plurality of substrates 18 that are frictionally supported, fixed, or moored to the hole wall Ba, and the tip of a support arm 19 that integrally extends in the radial direction of the hole B from each substrate 18. The part is integrally connected to the cylinder housing of the cylinder device 13, whereby a reaction force of the axial load Q is obtained. In the present embodiment, the support arm 19 has a biasing means that presses the substrate 18 against the hole wall Ba, and the substrate 18 frictionally engages the hole wall Ba and is frictionally supported by the hole wall Ba. Since the other configuration of the test apparatus 1 ′ shown in FIG. 4 is substantially the same as that of the test apparatus 1 shown in FIG. 3A, further detailed description regarding the test apparatus 1 ′ is omitted.

The loading test is performed by torsional shearing the test specimen SP in a state where the test specimen SP is isotropically consolidated or anisotropically consolidated. In addition to monotonous loading, it is also possible to carry out a test that combines repeated loading, creep loading, and the like. Basically, the test is carried _{out under the} condition (P _in = P _out ) where the side pressure P _in acting on the inner surface Sb of the specimen SP and the side pressure P _out acting on the outer side Sc of the specimen SP are equal. However, when the influence of the intermediate principal stress is examined, it is also possible to control both of them independently and adopt a condition (P _in ≠ P _out ) in which the side pressure P _in and the side pressure P _out are different. In principle, loading is performed until the specimen SP undergoes shear failure, compression failure, or tensile failure. Although the maximum load is determined by the purpose of the test, the size of the test specimen SP, the mechanical characteristics, and the like, the loading devices 11 and 12 have sufficient ability to break the test specimen SP.

  FIG. 5 is a diagram showing changes in the moment T and the axial load Q in the isotropic consolidation process and the torsional shear process during the loading test.

In the isotropic consolidation process, the axial load Q is loaded on the upper surface Sa of the test specimen SP with the direct stresses P _in and P _out acting on the inner surface Sb and the outer surface Sc of the test specimen SP, and the test specimen SP is deformed. Is left to converge. The most common stress state is the isotropic consolidated state (P _in = P _out = σ _Z ), but the anisotropic consolidated state (K _o consolidated state) (P _in = P _out ≠ σ _Z , static earth pressure coefficient K _o = P _in / σ _Z = P _out / σ _Z ) It is also possible to carry out a loading test. Further, in principle, the direct stresses P _in and P _out acting on the inner side surface Sb and the outer side surface Sc are equal (P _in = P _out ), but the conditions that the direct stresses P _in and P _out are different should be adopted. Is also possible (P _in ≠ P _out ). In this case, the influence of the intermediate principal stress (the influence of the intermediate principal stress coefficient b) can be examined. Furthermore, it is possible to initially load a moment T (torque due to a shear load in the twisting direction) on the upper surface Sa of the test specimen SP and set a state in which the initial shear is applied to the test specimen SP.

In the torsional shearing process, a moment T (torque due to the shearing load in the torsional direction) around the central axis C is loaded in an appropriate pattern on the upper surface Sa of the specimen SP. The most common pattern is monotonic loading, where the moment T is loaded at a constant loading speed, but it can be twisted in the opposite direction to study the dependence of the shear direction (this is a kind of anisotropy) Is a study of). In addition, it is possible to examine the case where there is no influence of the initial shear by making the swing, and further, it is possible to investigate the influence of the initial shear by shifting the vibration center (giving the initial shear). Furthermore, depending on the purpose of the test, a pattern in which repeated loading, minute unloading / reloading, creep loading, stress relaxation, etc. are combined as shown in FIG. 5 is adopted, or the loading speed is adjusted during monotonous loading. It is also possible to adopt a pattern to be changed. Further, according to the purpose of the test, a multi-stage loading type _{in which} the direct stresses P _in and P _out acting on the inner surface Sb and the outer surface Sc of the specimen SP are arbitrarily changed, or the consolidation process and the shearing process are repeated. It is also possible to carry out a test.

  FIG. 6 is a longitudinal sectional view schematically showing an aspect in which the specimen SP is collected after the loading test is completed and the test apparatus 1 is disassembled and removed.

  As shown in FIG. 6, the cap 10, the inner cell 20, the outer cell 30, the axial load loading device 11, the moment loading device 12, and the like constituting the test device 1 are disassembled and removed after the loading test is completed, and thereafter The specimen SP is separated from the rock mass M by the specimen collection jig 40 and collected for observing the deformation form, the destruction characteristics, and the like.

  FIG. 7A is a plan view showing the arrangement of a large number of load cells LC built in the cap 10, and FIG. 7B is a longitudinal sectional view showing the positional relationship between each load cell LC and the specimen SP. is there. FIG. 7C and FIG. 7D are diagrams illustrating the distribution of the axial load Q and the moment T detected by each load cell LC.

The test according to the present invention is to obtain a distribution of stress acting on the upper surface Sa of the specimen SP and to evaluate the anisotropic mechanical characteristics of the rock mass M based on the distribution of stress. For this reason, the bottom surface of the cap 10 (the contact surface with the upper surface Sa of the specimen SP) is equally divided into a plurality of sections in the circumferential direction, and an axis that acts on each section (section i = 1 to 8 (n)). A load cell LC for measuring the load Q _i and the moment T _i (torque due to the shear load in the torsional direction) is disposed in each section (load cell numbers (1) to (8)). The detection result of each load cell LC is output to the control unit CU (FIG. 3A) that records the detection result of the test apparatus 1. The distribution of the axial load Q _i and the moment T _i detected by each load cell LC is illustrated in FIGS. 7C and 7D.

  Next, analysis of test results will be described.

  In the following description, the displacement or strain is measured by measuring the axial displacement (compression amount / extension amount), torsional displacement (or rotation angle) around the central axis C, radial displacement (or inner diameter). And an outer diameter change amount or an inner circumference length and an outer circumference change amount), and a distortion in a predetermined position and direction of the outer surface Sc of the specimen SP. The strain on the outer surface Sc of the test body SP is measured by the strain gauge 42 (FIG. 2). If desired, the average distortion in the measurement range may be obtained by measuring the amount of compression / expansion in a certain measurement range.

  FIG. 8 is a plan view and a development view showing the arrangement of the strain gauges 42.

The strain gauge 42 is a specimen SP for the EWSN orientation system after measuring the strike α and the slope ξ of the discontinuous surface such as the deposition surface in the east-west-north-west orientation (EWSN orientation system) at the site where the test is performed. The outer surface Sc is disposed as shown in FIG. Each strain gauge 42 is bonded to an arbitrary position on the outer surface Sc of the test body SP with an adhesive or the like. It is desirable to stop the plate surface of each strain gauge 42 with paraffin or silicon rubber. With respect to the strain gauges 42 of numbers 1 to 6 shown in FIG. 8, assuming that the strain measured by the i-th strain gauge 42 is x _i , the strain tensor component of the EWSN orientation system can be calculated by the following Equation 1.

In addition, γ _ij is the engineering _{strain, γ ij = ε ij (i} ≠ j) between the _{ε ij (i, j = S} , E, V) relationship of. The torsional displacement (rotation angle) may be obtained by measuring the amount of rotation around the central axis C (V axis), or by measuring the displacement in the rotational direction at a certain distance from the central axis C (V axis). Is also possible.

By the above test method, the shear stress σ _ZΘ acting on the upper surface Sa of the specimen SP and the shear strain γ _ZΘ acting in the torsional direction in a state where a certain direct stress σ _Z is applied to the upper surface Sa of the specimen SP. Is measured. From this measurement result, the shear rigidity G (= σ _ZΘ / γ _ZΘ ) which is a deformation characteristic, the relationship between the damping constant h and the shear strain γ _ZΘ , and the maximum shear stress (shear strength) σ _ZΘ, which is a strength characteristic _{, max} and the like are obtained in the same manner as in the hollow torsional shear test which is a laboratory mechanical test.

Moreover, according to the said test method, the anisotropy of the dynamic characteristic of a rock mass can be investigated by one test using the single test body SP. That is, in the isotropic material, the stress and strain in the specimen SP are uniformly distributed during torsional shear and respond as elements, whereas in the anisotropic rock, in the circumferential direction. Since the direction of torsional shear is different, the stress and strain inside the specimen SP are unevenly distributed in the circumferential direction and distributed non-uniformly. By measuring and analyzing this on the upper surface Sa of the specimen SP, the rigidity and strength anisotropy of the rock mass M can be specified. In this test method, the distribution in the circumferential direction of the direct stress σ _Z and the shear stress σ _ZΘ (twisting direction) acting on the upper surface Sa of the specimen SP is measured, and anisotropy of rigidity and strength is assumed. By evaluating the test result using the relationship, the mechanical anisotropy of the specimen SP can be specified. For example, assuming a transversely isotropic elasticity suitable for describing the anisotropic stiffness of sedimentary rocks with stratigraphy, igneous rocks with set joints and metamorphic rocks, anisotropic stiffness is It is specified by the following method.

  An in-plane isotropic elastic body is an elastic body in which the elastic constant of an isotropic surface is different from the elastic constant in the direction of the elastic main axis (direction orthogonal to the isotropic surface). Used as an equivalent continuum equivalent to typical behavior (Goodman RE: Introduction to Rock Mechanics. J. Wiley, New York, 1989) and examples used as constitutive relations of sedimentary rocks (Oka F., Kimoto S Kobayashi H., Adachi T .: Anisotropic behavior of soft sedimentary rock. Soils and Foundations, Vol.42, No.5, pp.59-70, 2002) Examples (Akai K., Yamamoto K., Arioka M .: Experimental research on the structural anisotropy of crystalline schist. J. JSCE, Vol. 170, pp. 23-36, 1969) are known.

  FIG. 9 is a flowchart showing a procedure for obtaining the deformation anisotropy of the rock mass assuming in-plane isotropicity. FIG. 10 is a concept showing the slope (ξ, ζ) and the anisotropic direction (x ′, y ′, z ′) of a plane (ie, discontinuous plane) whose rigidity with respect to the EWSN orientation system is estimated to be isotropic. FIG. 11 is a diagram showing how the orthogonal coordinate system (X, Y, Z) is set. Further, FIG. 12 is a diagram showing the relationship between a test specimen prepared from a rock mass assuming an in-plane isotropic elastic body and coordinate axes, and FIG. 13 is a diagram illustrating a method for setting the direction of anisotropy. FIG. 14 is a diagram illustrating the stress distribution of the measured shear stress.

  As shown in FIG. 9, as a test preparation, a hollow cylindrical specimen SP is excavated and fabricated in the rock mass M (Step 1), and the direction of the surface whose rigidity is estimated to be isotropic by visual observation of the specimen SP. α and inclination ξ are estimated (Step 2). At this time, the positional relationship between the orientation of the East, West, North and South (EWSN) and the surface of the specimen SP and the positional relationship of the surface where the rigidity is estimated to be isotropic are confirmed. Thereafter, the inner cell 20, the outer cell 30, and the loading devices 11, Are installed on the specimen SP, and measuring instruments such as the strain gauge 42 are installed (Step 3). As described above, the strain gauge 42 is arranged as shown in FIG. 8 with respect to the EWSN orientation.

Next, isotropic pressure loading (Step 4), triaxial loading (Step 5) and torsional loading (Step 6) are performed, and the stress and strain of the specimen SP are measured. Preferably, in order of loading, in consideration of plastic deformation due to shear, isotropic pressure loading is performed first, then triaxial loading is performed in an elastic region of a strain level of 10 ^-4 or lower, and finally torsional loading is performed. Is set to perform. It is also possible to determine the presence or absence of plastic deformation by raising or lowering the stress applied in stages with each loading, or to measure the change in rigidity accompanying plastic deformation.

Next, using the measured values of strain at the isotropic pressure loading, the inclination angles (ξ, ζ) of the anisotropic directions (x ′, y ′, z ′) from the EWSN orientation system shown in FIG. The coordinate axis is specified (Step 7). The strain increment tensor Δε ′ at the isotropic pressure loading in the EWSN orientation is expressed by the following formula 2. Based on Δε ′ obtained by Equation 2, the main strain is obtained by Equation 3 below.

In diagonalizing the distortion tensor of Equation 3, the Jacobi method or the like is used, and the unit direction vector e of the main strain expressed by Equation 4 below is obtained. During isotropic pressure loading, since the anisotropic direction (x ', y', z ') and the principal strain direction (1, 2, 3) are co-axial, the inclination angle from the EWSN orientation (ξ, ζ) constitutes a vector e. For example, ξ and ζ are specified on the basis of the following formula 5, but ζ may be obtained from the vector e ₁₂ and ξ may be obtained from the vector e ₂₃ . In order to evaluate variation, a plurality of obtained values of ξ and ζ may be averaged.

Here, using the value of ζ, as shown in FIG. 11, the orthogonal coordinate system (X, Y, Z) is set so that the Y axis is positioned at an angle ζ from the S axis. By this operation, the X axis and the x ′ axis become coaxial. Further, when a cylindrical coordinate system (R, Θ, Z) is set so as to conform to this coordinate system (X, Y, Z) coordinate system and the measurement result of the angle ξ is combined, a test body as shown in FIG. The relationship between SP and coordinate axes is obtained. The surface orientation α (= π / 2 + ζ) and inclination ξ of which the rigidity obtained in the visual observation (Step 2 in FIG. 9) is estimated to be isotropic, and the direction of anisotropy from the EWSN orientation system (x The alignment with the slopes (ξ, ζ) of ', y', z ') can be confirmed at this point. At this time, assuming the in-plane isotropic elastic body, the Young's modulus, Poisson's ratio and shear rigidity in the x'y 'plane and z' direction are (E _{x '} , ν _x' , G _{x '} = E _x' / 2 (1 + ν _{x ′} )) and (E _{z ′} , ν _{z ′} , G _{z ′} ). Further, in order to organize the test results to be described later, the distortion tensor of the EWSN orientation system of Equation 2 is transformed into an orthogonal coordinate system (X, Y, Z) by Equation 6 below.

As described above, theoretically, when [the rigidity of the x′y ′ plane <the rigidity of the z ′ plane], 1-2 plane = x′y ′ plane, 3 directions = z ′ direction, ε ₁ = Ε ₂ , and if [z 'surface rigidity <x'y' surface rigidity], 2-3 surface = x'y 'surface, 1 direction = z' direction, and ε ₂ = ε ₃ However, if ε ₁ ≠ ε ₂ ≠ ε ₃ , the anisotropy direction is set as shown in FIG.

Next, an elastic constant is determined based on the measured stress and strain (Steps 4, 5, and 6 in FIG. 9) (Step 8 in FIG. 9). The theoretical solution of the direct stress and the shear stress at the time of torsional loading based on the elasticity theory is expressed by the following Equation 7. D _ijkl , (i, j, k, l = 1, 2, 3) is a stiffness tensor, and the components of the stiffness tensor of the in-plane isotropic elastic body are (D ₁₁₁₁ , D ₁₁₃₃ , D ₃₃₃₃ , D ₁₂₁₂ and D ₂₃₂₃ ). The relationship between the stiffness tensor component and the elastic constant will be described later. Δσ _Z and Δσ _ZΘ are the direct stress increment and the shear stress increment, and Δε _ZΘ is the shear strain increment.

From Equation 7, Θ = 0 ° at the time of twisting loading, the theoretical solution in the position of 90 ^o, is expressed by Equation 8 below. Equation 8 shows that the ratio of the direct stress increment and the shear strain increment at Θ = 0 ^o is Δσ _Zat0 / Δε _ZΘ , (= k ₁ ), and the shear stress increment and the shear strain increment at Θ = 0 ^o and Θ = 90 ^o The ratio of Δσ _Zθat0 / Δε _ZΘ , (= k ₂ ) and Δσ _ZΘat90 / Δε _ZΘ , (= k ₃ ). The stress used here is obtained by fitting the stress distribution measured by the divided load cell as shown in FIG. 14 by the least square method or the like and using the stress at the position on the circumference. The shear strain increment Δε _Zθ is calculated from Equation 9 below using the rotation angle ΔΘ measured at an arbitrary position. D _out and d _in are the outer diameter and inner diameter of the specimen, and h _s is the height dimension of the specimen SP.

Similarly, the theoretical solution of the direct stress and the shear stress at the time of triaxial loading obtained by the elasticity theory is expressed by the following formula 10. In triaxial loading, the stress measured by the split load cell is constant, so the measured stress at any position on the circumference may be used for the calculation, or measured by multiple load cells LC. You may use the average value of stress for calculation. The axial strain increment Δε _a is equal to the direct strain increment Δε _Z in the Z direction obtained by Equation 6. Symbols are set as Δσ _Z / Δε _a , (= k ₄ ), Δσ _Zθ / Δε _a , (= k ₅ ).

Similarly, the theoretical solution at the time of isotropic pressure loading is expressed by the following mathematical formula 11. Even at the isotropic pressure loading, the stress measured by the split load cell becomes a constant value. Since the direct strain increment Δε _c at the time of isotropic pressure loading is equal to the direct strain in an arbitrary direction, either one of (Δε _X , Δε _Y , Δε _Z ) of Equation 6 is used, or these three An average value of direct distortion may be used. Symbols are set as Δσ _Z / Δε _c , (= k ₆ ), Δσ _ZΘ / Δε _c , (= k ₇ ).

Next, the elastic constant is specified from the measured stress data using the least square method represented by the following Expression 12.

Symbols k and A are the measurement value matrix calculated from Equations 8, 10, and 11 and a coefficient matrix representing the direction of anisotropy, and symbol D is a component of the stiffness matrix of the in-plane isotropic elastic body. , Represented by the following Equation 13.

The elastic constant of the rock mass assuming the in-plane isotropic elastic body is determined as follows using the stiffness tensor component according to the following mathematical formula 14 using D obtained by the mathematical formula 12.

  The preferred embodiments of the present invention have been described in detail above. However, the present invention is not limited to the above-described embodiments, and various modifications or changes can be made within the scope of the present invention described in the claims. Is possible.

  For example, in the above embodiment, the test method uses an inner cell and an outer cell on which fluid pressure acts, but when the rock mass strength that maintains the structural stability during loading is obtained, the lateral pressure by the inner cell and the outer cell is obtained. It is also possible to omit the addition of.

  Further, the number of divisions on the bottom surface of the cap, the inner diameter / outer diameter ratio of the test body, the height / outer diameter ratio of the test body, and the like can be appropriately set and changed according to the purpose of the test.

  The present invention is preferably applied to an in-situ rock test method and test apparatus for examining or specifying the deformation characteristics and strength characteristics of a rock having mechanical anisotropy. Specifically, the test method and the test method of the present invention can be preferably used for ground investigation for construction of a rock structure or the like. Examples of bedrock structures include dams located on the bedrock, long bridges, foundations of large structures such as nuclear power plants, and bedrock slopes or surrounding bedrock such as underground cavities located in the bedrock.

  According to the test method and test apparatus of the present invention, a simple shear mode test similar to the hollow torsional shear test (geological engineering standards: JGS 10543-2009, 0551-2009) in the laboratory mechanical test is performed in-situ. However, since the mechanical properties of the rock mass can be evaluated by an in-situ test in the simple shear mode, its practical value is remarkable.

1, 1 'In-situ rock torsion test equipment 2 Central hole
3 outer peripheral groove 10 cap or lid
11 Axial load loading device 12 Moment loading device 20 Inner cell 30 Outer cell M Rock mass Ma Ground surface SP Specimen LC Load cell (measuring unit or measuring instrument)
LU load cell unit (measurement means)
CU Control unit Q Axial load T Moment

Claims (9)

Drilling or drilling the rock head outcrop or the bottom of the borehole to form a hollow cylindrical specimen in its original position, and applying the load to the specimen to examine the deformation characteristics and strength characteristics of the specimen Or in the in-situ rock test method
A cap or lid having a measuring means for measuring a direct stress and a shear stress is disposed on the top or upper end of the test body,
By simultaneously loading an axial load in the direction of the central axis of the specimen and a moment about the central axis of the specimen on the cap or the lid, the axial load and the moment act on the specimen via the cap. Cough,
By detecting the direct stress and shear stress acting on the boundary between the cap or lid and the top surface or the upper surface of the test body by the measuring means, and obtaining the circumferential distribution of the direct stress and the shear stress, An in-situ rock mass test method characterized by examining or specifying the deformation characteristics and strength characteristics of a rock mass.   The bottom surface of the cap or lid contacting the top surface of the test body is divided into a plurality of sections in the circumferential direction, and the measuring unit or measuring instrument detects the direct stress or axial load acting on each section, and The in-situ rock test method according to claim 1, wherein a shear stress or a shear load in a torsional direction acting on the section is detected.   The in-situ bedrock test method according to claim 1 or 2, wherein the bottom surface of the cap or lid is equally divided into six or more sections. The inner diameter / outer diameter ratio (d _in / d _out ) of the test specimen is set to a value within a range of 1.0> d _in / d _out ≧ 0.6. The in-situ rock mass test method according to claim 1. The in-situ rock mass testing method according to any one of claims 1 to 4, wherein the height / outer diameter ratio (h _s / d _out ) of the test specimen is set to a value of 0.5 or more. . Investigate the deformation characteristics and strength characteristics of the loading device, which loads a load on a hollow cylindrical specimen formed in situ by excavating or drilling the outcrop of the bedrock or the bottom of the borehole, or In-situ rock test apparatus having a measuring means for detecting stress acting on the specimen to identify
A cap or lid having measuring means for measuring direct stress and shear stress is disposed on the top or upper end of the test body,
The aforementioned loading device is configured to simultaneously load an axial load and a moment on the test body via the cap or the lid,
The measuring means has a plurality of measuring units or measuring devices for detecting a direct stress or axial load and a shear stress or a shear load acting on a boundary between the cap or lid and the top surface or the upper surface of the test body. ,
The in-situ bedrock testing apparatus, wherein the measuring unit or measuring instrument is arranged in a circumferential direction on a top surface or an upper surface of the test body.   The bottom surface of the cap or lid contacting the upper surface of the test body is divided into a plurality of sections in the circumferential direction, and the measuring unit or measuring instrument detects and twists the direct stress or axial load acting on each section. The in-situ rock test apparatus according to claim 6, further comprising a load cell that detects a shear stress or a shear load in a vertical direction. The bottom surface of the cap or lid is equally divided into six or more sections, and the inner diameter / outer diameter ratio (d _in / d _out ) of the test body is 1.0> d _in / d _out ≧ 0.6 The height / outer diameter ratio (h _s / d _out ) of the test specimen is set to a value of 0.5 or more. In-situ rock testing equipment.   The loading device described above includes an axial load loading device for loading an axial load on the test body, and a moment loading device for loading a moment on the test body, and the axial load loading device and the moment loading device are: Axial load and moment are output to the cap or lid, and the cap or lid transmits the axial load and moment to the upper end of the test body via the measuring unit or measuring instrument. The in-situ rock mass testing apparatus according to any one of Items 6 to 8.

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