JP5337004B2 - In-situ rock tension test method and test apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To apply a tensile load which is straight in a radial direction and free of disturbances such as vibration and deviation so as to create an ideal destruction state to a test body and pulling the test body straight in the radial direction. <P>SOLUTION: An apparatus includes a center guide 2c inserted into a center hole 11a of a test body 11 and provided with an anchor block 2d at a lower end thereof which is fixed to the bottom of the center hole 11a; a pressure plate 4 penetrated by the center guide 2c to be placed on an upper surface of the test body 11 and with a lower surface thereof adhered to the upper surface of the test body 11; a load measuring means 3 mounted to an upper surface of the pressure plate 4; a tensile load application means 2 disposed above the load measuring means 3 and fixedly mounted to a position close to an upper end of the center guide 2c; and a guide mechanism 7A interposed between and among the center guide 2c and a piston 2b of the tensile load application means 2, the load measuring means 3, and the pressure plate 4. <P>COPYRIGHT: (C)2011,JPO&amp;INPIT

Description

  The present invention relates to an in-situ rock tension test method and test apparatus. More specifically, the present invention relates to a method and apparatus for uniaxial and triaxial tensile tests performed by applying a tensile load to a rock in situ. This test method is a technique suitable for evaluating strength characteristics such as tensile strength and shear strength that can be exerted by rock mass in uniaxial tension and triaxial tensile stress conditions, and deformation characteristics such as rigidity and Poisson's ratio. It is.

  As a method for testing the tensile strength of the rock mass, the “crush test” in which a linear load is loaded on the side surface of a cylindrical specimen has been standardized by the Geotechnical Society of Japan. Specifically, for example, a cylindrical specimen is formed from a sample obtained by, for example, boring, the fracture load is measured while applying a compressive load to the cylindrical specimen, and the tensile strength is calculated using the measured value. (Non-Patent Document 1).

  In addition, research on "uniaxial and triaxial tensile tests" in which end members are fixed to both ends in the axial direction of a cylindrical specimen with an adhesive, and the end members are pulled through a ball joint for homogeneous rocks has been conducted. (Non-Patent Document 2).

Geotechnical Society Standards (JGS 2551-2002): Test method for tensile strength of rock by crushing, Geotechnical Society of Japan, 2002

Tani Kazuo: Fracture mechanism under low confining pressure of homogeneous soft rock by triaxial tensile test, 27th Symposium on Rock Mechanics, pp.226-230, Japan Society of Civil Engineers, 1996

  However, since rocks and rock masses are often inhomogeneous or have cracks, the method of calculating the tensile strength by applying a compressive load as in the “cracking test” of Non-Patent Document 1 Since an ideal (that is, linear elastic theory) stress state cannot be created, it is extremely difficult to obtain an accurate tensile strength. For this reason, it is difficult to say that the method of Non-Patent Document 1 is highly reliable. Even small specimens (generally φ = 50 [mm] in laboratory tests) are often inhomogeneous or contain cracks, and specimens with a large in-situ test level (diameter φ = 300). [Mm] or more), it is almost impossible to avoid including inhomogeneities and cracks. In the crush test, the line load cannot be ideally loaded, the load width is not zero, and the belt load is finite, and it is ideally not a linear elastic body, so the reliability is high. It's hard to say.

  Moreover, in the case of the “crush test” of Non-Patent Document 1, by applying a compressive load to the specimen, a substantially flat fracture surface passing through the tangent line between the upper and lower pressure plates and the specimen is generated on the specimen. In an ideal state of destruction, if the outer shell of the specimen is soft due to weathering, for example, when a compressive load is applied to the specimen, the soft part will collapse and create an ideal stress state. Or if the specimen contains hard gravel, the tensile crack will bend to avoid the gravel and the ideal tensile crack will not occur. The strength cannot be obtained, and from this point, it is difficult to say that the method of Non-Patent Document 1 is highly reliable.

  In the “uniaxial and triaxial tensile tests”, it is ideal that a tensile load is applied to the specimen and pulled straight in the axial direction, causing a flat fracture surface perpendicular to the axial direction to occur in the specimen and causing the specimen to break. In the case of the technique of Non-Patent Document 2, the end member attached to the both axial end surfaces of the specimen with an adhesive is pulled through the ball joint. There is a possibility that the end member may rotate or shift its axis due to uniform deformation, and the bending moment may act on the specimen due to the deviation or inclination of the central axis of the specimen, and the tensile strength may be underestimated. That is, the specimen cannot be pulled straight in the axial direction, and therefore it is extremely difficult to obtain an accurate tensile strength. From this point, it is difficult to say that the method of Non-Patent Document 2 is highly reliable. .

  Therefore, in order to create an ideal fracture state, the present invention applies a tensile load that is a straight tensile load in the axial direction and has no disturbance such as vibration and vibration to the test specimen to straighten the test specimen in the axial direction. It is an object of the present invention to provide an in-situ rock tension test method and test apparatus that can be pulled and accurately measure the tensile strength in which the characteristics of the rock in the original position are reflected as they are.

  In order to achieve this object, the in-situ rock tension test method according to claim 1 is a cylindrical shape in which a cylindrical slit is formed in the rock, an outer peripheral surface is formed by the slit, and a bottom surface is continuous with the rock. Forming a test body by forming a center hole at the axial position of the portion, inserting a rod-shaped center guide into the center hole and fixing the anchor block at the lower end of the center guide to the bottom of the center hole, A step of installing a pressure plate that is placed on the upper surface of the test body through the portion near the upper end of the center guide protruding from the ground surface of the test body, and the lower surface is bonded to the upper surface of the test body; and above the pressure plate A process for applying a tensile load in the axial direction to the specimen through a pressure plate using a tensile load applying means that is provided and fixedly attached at a position near the upper end of the center guide. And a step of measuring the breaking load when the test specimen is tensile fractured, and controlling the reaction force exerted on the tensile load applying means when applying the tensile load to the bedrock by the center guide, The center plate and the guide mechanism interposed between the pressure plate and the center guide suppress the vibration and vibration, and the pressure plate moves along the center guide so that it is straight and free of turbulence. A tensile load is applied to the specimen.

  In addition, the in-situ rock tension test device according to claim 5 is formed by separating a rock from a rock by a cylindrical slit to form an outer peripheral surface, and a center hole is formed at the axial center position of a cylinder whose bottom is continuous with the rock. A center guide with an anchor block that is inserted into the center hole of the test specimen and is fixed to the bottom of the center hole, and a portion near the top end of the center guide protruding from the ground surface of the rock A pressure plate that is placed on the upper surface of the test body and whose lower surface is bonded to the upper surface of the test body, load measuring means attached to the upper surface of the pressure plate, and a center guide provided above the load measuring means. A tensile load applying means fixedly attached at a position near the upper end of the guide, and a guide mechanism interposed between the center guide and at least the pressure plate, The reaction force exerted on the tensile load applying means when the tensile load is applied in the axial direction to the test body via the pressure plate is controlled by the center guide and is controlled by the center guide and at least the pressure plate. When the pressure plate moves along the center guide in a state where vibration and vibration are suppressed by the action of the guide mechanism interposed between the center guide and the tensile load straight in the axial direction and without disturbance, It is trying to grant.

  The in-situ rock mass tensile testing apparatus according to claim 6 is formed by separating the rock mass from the rock mass by a cylindrical slit to form an outer peripheral surface and forming a center hole at the axial center position of a cylinder whose bottom surface is continuous with the rock mass. A center guide with an anchor block that is inserted into the center hole of the test specimen and is fixed to the bottom of the center hole, and a portion near the top end of the center guide protruding from the ground surface of the rock A pressure plate that is placed on the upper surface of the test body and whose lower surface is bonded to the upper surface of the test body, a tensile load applying means that is fixedly attached to a position near the upper end of the center guide, and an upper end portion that applies the tensile load. A frame which straddles or covers the means and whose lower end surface is attached to the upper surface of the pressure plate, a load measuring means interposed between the tensile load applying means and the frame, And a guide mechanism interposed between at least the pressure plate and exerted on the tensile load applying means when the tensile load is applied to the test body in the axial direction through the pressure plate by the tensile load applying means. The reaction force is transmitted and controlled by the center guide to the rock, and applied along the center guide in a state in which vibration and vibration are suppressed by the center guide and at least the guide mechanism interposed between the pressure plate and the center guide. By moving the pressure plate, a tensile load that is straight in the axial direction and has no turbulence is applied to the specimen.

  Thus, according to these in-situ rock tension test methods and test equipment, a center guide is provided that is fixed at the axial center position of the specimen cut from the in-situ rock, and functions between the center guide and the pressure plate. Since the pressure mechanism moves along the center guide, a straight and stable (in other words, no turbulence) tensile load is applied to the specimen. Also, unlike the conventional method, the specimen is broken by applying a compressive load, and the tensile strength is not calculated on the premise of an ideal (ie, linear elastic theory) stress state. Since the tensile load is applied by pulling the bedrock specimen and the fracture load when the specimen is subject to tensile failure is measured directly, the test results may have erroneous effects due to the characteristics of the specimen. The tensile strength that reflects the characteristics of the rock in the original position without being reflected is measured at the original position.

  In the present invention, the load that is straight in the axial direction and has no turbulence means that the load axis and the test body axis are parallel to each other without any eccentricity, and that acceleration or inertial force is applied. A load that satisfies the two conditions of no vibration and no vibration. However, it may be static repetition or alternating loading.

  According to a second aspect of the present invention, in the in-situ rock tension test method of the first aspect, in addition to the functions of the center guide and the guide mechanism, a side guide and a pressure plate provided to cover the outer peripheral surface of the pressure plate; By the action of the side guide mechanism interposed between the side guide and the side guide mechanism, the pressure plate moves from both sides of the inner peripheral surface and the outer peripheral surface in a state in which vibration and vibration are suppressed.

  The invention according to claim 7 is the in-situ rock tension test device according to claim 5 or 6, wherein the side guide provided to cover the outer peripheral surface of the pressure plate is interposed between the pressure plate and the side guide. And a side guide mechanism.

  In these cases, since a mechanism for suppressing vibration and shaking from both the inner and outer peripheral surfaces of the pressure plate is provided, a tensile load in a certain direction and more stable (in other words, no disturbance). Is applied to the specimen.

  The invention described in claim 3 is the in-situ rock mass tensile test method according to claim 1 or 2, further applying a lateral pressure as a restraining pressure to the outer peripheral surface of the test body and the peripheral surface of the center hole. A tensile test is performed.

  The invention according to claim 8 is the in-situ rock mass tensile test device according to any one of claims 5 to 7, wherein the lateral pressure as a restraining pressure is applied to the outer peripheral surface of the test body, which is disposed in the slit. And a packer for applying a lateral pressure as a restraining pressure to the peripheral surface of the center hole.

  In these cases, a state in which restraint pressure is applied to the side peripheral surface of the test body is achieved, and a triaxial tensile test is performed.

  According to a fourth aspect of the present invention, in the in-situ rock tension test method according to any one of the first to third aspects, the axial center direction and the radial direction or the circumferential direction displacement are measured on the outer peripheral surface of the test body. Measurements are taken to determine the deformation characteristics of the specimen. In this case, in addition to obtaining the tensile strength of the specimen, it is possible to obtain and evaluate deformation characteristics under a uniaxial tensile stress state and a triaxial tensile stress state.

  According to the in-situ rock tension test method and test apparatus of the present invention, the test plate is provided with a tensile load that is straight and undisturbed in the axial direction by moving the pressure plate along the center guide. Since it is pulled straight in the axial direction, it is possible to create an ideal fracture state and measure an accurate tensile strength, thereby improving measurement reliability. In addition, the test results do not reflect erroneous effects due to the characteristics of the specimen, and the tensile strength that directly reflects the characteristics of the rock in the original position is measured at the original position. As a result, the reliability of measurement can be improved.

  Furthermore, when a mechanism for suppressing vibration and shaking from both the inner and outer peripheral surfaces of the pressure plate is provided, a tensile load in a certain direction and more stable (in other words, no disturbance) is applied to the test specimen. Therefore, the measurement reliability can be further improved.

  Furthermore, when a lateral pressure as a restraining pressure is further applied to the outer peripheral surface of the test body and the peripheral surface of the center hole, a state in which the restraining pressure is applied to the side peripheral surface of the test body is achieved. Since the axial tension test can be performed, the versatility of the present invention can be improved.

It is a figure explaining the outline of the apparatus structure of an example of embodiment of the in-situ rock tension test apparatus of this invention. It is a flowchart explaining an example of embodiment of the in-situ rock tension test method of this invention. It is the schematic explaining the in-situ rock tension test method of embodiment. (A) is the schematic explaining the procedure which forms a slit in a bedrock. (B) is the schematic explaining the procedure which forms a center hole. It is the schematic explaining the in-situ rock tension test method of embodiment. (A) is the schematic explaining the state by which the test body which was cut out from the bedrock and which has a center hole was formed. (B) is the schematic explaining the procedure which fixes an anchor block to the bottom part of a center hole. It is the schematic explaining the procedure of the in-situ rock tension test method of embodiment. (A) is the schematic explaining the state which installed the test apparatus on the upper surface of the test body. (B) is the schematic explaining the state which the test body carried out the tensile fracture by giving a tensile load. It is a figure explaining the outline of the apparatus structure of an example of other embodiment of the in-situ rock tension test apparatus of this invention. It is a figure explaining the outline in the case of giving a side pressure as a restraint pressure in this invention.

  Hereinafter, the configuration of the present invention will be described in detail based on an example of an embodiment shown in the drawings.

  FIG. 1 shows an example of an embodiment of the in-situ rock tension test apparatus of the present invention. In this in-situ rock tension test apparatus 1, a center hole 11a is formed at the axial center position of a cylinder that is separated from the rock 10 by a cylindrical slit 10a to form an outer peripheral surface and the bottom is continuous with the rock 10. A center guide 2c having an anchor block 2d which is inserted into the center hole 11a of the test body 11 and fixed to the bottom of the center hole 11a at the lower end, and a center guide 2c protruding from the ground surface of the rock 10 A pressure plate 4 that is placed on the upper surface of the test body 11 through a portion close to the upper end and whose lower surface is bonded to the upper surface of the test body 11; load measuring means 3 that is attached to the upper surface of the pressure plate 4; A tensile load applying means 2 provided above the load measuring means 3 and fixedly attached at a position near the upper end of the center guide 2c, and the center guide 2c It has a guide mechanism 7A interposed between the piston 2b of the tensile load applying means 2 and the load measuring means 3 and the pressure plate 4. The tensile load applying means 2 applies a tensile load to the specimen 11 via the pressure plate 4. The reaction force exerted on the tensile load applying means 2 during application is controlled by being transmitted to the rock 10 by the center guide 2c, and the center guide 2c, the piston 2b, the load measuring means 3, the pressure plate 4, and the center guide 2c. When the pressure plate 4 moves along the center guide 2c in a state where vibration and vibration are suppressed by the action of the guide mechanism 7A interposed therebetween, a tensile load straight in the axial direction and without any disturbance is applied to the test body 11. It is given.

  Here, the axial direction of the center hole 11a is defined as the axial direction in the following description. Further, as shown in FIG. 1, the vertical position and the vertical direction are defined on the basis of the posture in which the in-situ rock tension test device 1 is installed on the ground surface of the rock 10 and performs the test. In the present invention, the axial direction of the center hole 11a is not limited to the vertical direction (that is, there may be a direction inclined from the vertical direction), and the axial direction of the center guide 2c is limited to the vertical direction. I can't.

  As the tensile load applying means 2 of the present invention, for example, a hydraulic or mechanical center hole jack is used. Since the center hole jack itself is a well-known technique, the details are omitted here, but the tensile load applying means 2 of the present embodiment is a hollow cylindrical cylinder as in the general structure of a general center hole jack. 2a, a cylindrical piston 2b provided in the hollow portion of the cylinder 2a and having an axial through hole, a center guide 2c provided through the axial through hole of the piston 2b, and the center guide 2c The anchor block 2d is attached to the lower end portion of the cylinder 2a, and the clamp 2e is fixedly attached to the upper end portion of the hollow portion of the cylinder 2a and fixes the upper end portion of the center guide 2c.

  The anchor block 2d is for fixing the lower end portion of the center guide 2c to the bedrock 10. The center guide 2c is fixed in position with respect to the rock mass 10 by the anchor block 2d at the lower end.

  The load measuring means 3 and the pressure plate 4 form a disk shape having a through hole in the center. Then, in a state where the position of the axial through hole of the piston 2b of the tensile load applying unit 2 and the position of the through hole of the load measuring unit 3 and the pressure plate 4 coincide with each other, the load measuring unit 3 is provided on the lower end surface of the piston 2b. The pressure plate 4 is attached to the lower surface of the load measuring means 3.

  For example, a center hole type load cell is used as the load measuring means 3 of the present invention.

  The pressure plate 4 is formed using a material having rigidity such as steel. Further, the pressure plate 4 is prepared as having the same outer diameter as the outer diameter of the test body 11.

  The lower surface of the pressure plate 4 is bonded to the upper surface of the test body 11 cut from the bedrock 10 by the slit 10 a by the adhesive member 6.

  As the adhesive member 6, for example, an adhesive is used, and specifically, a material that can fill the gap between the lower surface of the pressure plate 4 and the upper surface of the test body 11 and can firmly bond the both is used. The adhesive member 6 is not limited to an adhesive as long as the pressure plate 4 and the test body 11 can be firmly bonded and integrated.

  The in-situ rock tension test apparatus 1 of the present embodiment includes a guide mechanism 7A interposed between the center guide 2c of the tensile load applying means 2, the piston 2b, the load measuring means 3, and the pressure plate 4.

  When the load measuring means 3 and the pressure plate 4 are moved in the axial direction of the center guide 2c by operating the piston 2b, the guide mechanism 7A has the center guide 2c, the piston 2b, the load measuring means 3, the pressure plate 4 and the like. In addition, the piston 2b, the load measuring means 3, and the pressure plate 4 are operated straight along the center guide 2c without vibrating or shaking. Therefore, as the guide mechanism 7A, one that can smoothly slide the peripheral surfaces facing each other with little or no friction is used. Specifically, for example, a ball bearing or a bushing is used as the guide mechanism 7A.

  In the present embodiment, the guide mechanism 7A is provided across the piston 2b, the load measuring means 3, and the pressure plate 4. However, in the present invention, the pressure plate 4 is straight along the center guide 2c. Therefore, it is important that the guide mechanism 7A is provided between the center guide 2c and at least the pressure plate 4 (in this case, the center guide 2c and the guide guide 7c). The piston 2b and the load measuring means 3 are configured not to contact each other). The guide mechanism 7A may be attached to the outer peripheral surface of the center guide 2c, or may be attached to the inner peripheral surface of the piston 2b, the load measuring means 3, and the pressure plate 4.

  The in-situ rock tension test apparatus 1 of the present embodiment includes an annular side guide 5 provided so as to cover the outer peripheral surface of the pressure plate 4. The side guide 5 is formed using a material having rigidity such as steel, for example, and is fixed to the ground surface of the rock mass 10 by an anchor (not shown) attached to the lower surface.

  A side guide mechanism 7 </ b> B interposed between the pressure plate 4 and the side guide 5 is provided.

  The side guide 5 and the side guide mechanism 7B are configured so that the piston 2b operates and the center guide does not vibrate or shake when the pressure plate 4 operates in the axial direction of the center guide 2c via the load measuring means 3. The pressure plate 4 is moved straight along 2c. Therefore, as the side guide mechanism 7B, one that can smoothly slide the peripheral surfaces facing each other with little or no friction is used. The side guide mechanism 7 </ b> B may be attached to the outer peripheral surface of the pressure plate 4 or may be attached to the inner peripheral surface of the side guide 5.

  Specifically, for example, a ball bearing is used as the side guide mechanism 7B. And when using a ball bearing, you may make it use what is arrange | positioned in the circumferential direction on the side peripheral surface of the pressurizing plate 4. FIG. In this case, a circular ring in the circumferential direction may be used, a plurality of fan-shaped arcs may be arranged in the circumferential direction at intervals, or one stage (in other words, one round) may be used. A plurality of stages (a plurality of circumferences) may be used in the vertical direction. Moreover, you may make it arrange | position the thing of an axial direction at intervals in the side peripheral surface of the pressurization board 4. FIG. In this case, when the balls are arranged at equal intervals in the circumferential direction, at least three ball bearings in the vertical direction are arranged.

  Further, a mechanism may be further provided between the pressure plate 4 and the side guide 5 so that the pressure plate 4 is movable only in the axial direction relative to the side guide 5 fixed to the ground surface of the rock 10. . For example, a male guide (for example, a convex portion) is provided on the outer peripheral surface of the pressure plate 4, and an axial center direction that meshes with the inner peripheral surface of the side guide 5 so as to be smoothly slidable with the male guide. A female guide slide (for example, a concave groove) may be provided. In this case, the axial rotation of the pressure plate 4 can be more reliably prevented, and a straight tensile load can be applied to the test body 11 in the axial direction without twisting.

  With the above configuration, according to the in-situ rock tension test apparatus 1 of the present invention, the piston 2b of the tensile load applying means 2 faces upward while the center guide 2c is fixed in position with respect to the rock 10 and the test body 11. By operating, a tensile load in the axial direction is applied to the test body 11 via the load cell 3, the pressure plate 4, and the adhesive member 6. At this time, the pressure plate 4 operates in a straight and stable manner in the axial direction of the specimen without being vibrated or shaken by the center guide 2c, the guide mechanism 7A, and the side guide 5 and the side guide mechanism 7B. A tensile load that is straight and not disturbed is applied to the test body 11.

  Here, when viewed from the center of the tensile load applying means 2, when the piston 2b tries to move upward, a downward load is exerted on the tensile load applying means 2 as a reaction force of the operation, and the downward load is applied via the clamp 2e. Thus, the center guide 2c to which the cylinder 2a is fixed and attached is transmitted to the bedrock 10 on the bottom surface of the center hole 11a (and below the test body 11), and is received and controlled. A tensile load is applied to the test body 11 by the operation of the piston 2b in a state where the position is fixed.

  Next, the in-situ rock tension test method of the present invention will be described with reference to FIGS.

  In the in-situ rock tension test method of this embodiment, as shown in FIG. 2, a cylindrical slit 10 a is formed in the rock 10, an outer peripheral surface is formed by the slit 10 a, and a bottom surface is continuous with the rock 10. Forming the center hole 11a at the axial center position of the cylindrical portion to form the test body 11 (S1), inserting the rod-shaped center guide 2c into the center hole 11a, and anchor block 2d at the lower end of the center guide 2c Is fixed to the bottom of the center hole 11a (S2), and a portion near the upper end of the center guide 2c protruding from the ground surface of the bedrock 10 is placed on the upper surface of the test body 11, and the lower surface is the test body A step (S3) of installing the pressure plate 4 to be bonded to the upper surface of the head 11, and a pressure plate 4 provided above the pressure plate 4 and fixed at a position near the upper end of the center guide 2c. A step of applying a tensile load to the specimen 11 via the pressure plate 4 using the attached tensile load applying means 2 (S4), and a step of measuring a breaking load when the specimen 11 undergoes a tensile failure (S5). And a step (S6) of observing the fracture surface of the specimen 11 and controlling the reaction force exerted on the tensile load applying means 2 when the tensile load is applied to the bedrock 10 by the center guide 2c. Along with the center guide 2c and the guide mechanism 7A interposed between the pressure plate 4 and the center guide 2c, the pressure plate 4 moves along the center guide 2c in a state in which vibration and vibration are suppressed. A tensile load that is straight in the direction and free of turbulence is applied to the test body 11.

  Specifically, in performing the in-situ rock tension test method of the present invention, first, a test body is formed at the in-situ (S1).

  For forming the test body 11, first, excavation is performed on the bedrock 10 using a cylindrical large-bore bore 20 (FIG. 3A), and a cylindrical slit 10a is formed (FIG. 3B). )). Thereby, the outer peripheral surface of the cylindrical test body 11 is formed by being cut from the bedrock 10.

  Next, excavation is performed using the small-bore boring 21 (FIG. 3B), and the axial center hole 11a is located at the axial center position of the cylindrical specimen 11 cut from the rock mass 10 by the above processing. Is formed. The center hole 11a is formed to be deeper than the slit 10a.

  As described above, the cylindrical test body 11 having the outer peripheral surface formed by being separated from the rock 10 by the slit 10a and having the bottom surface continuous with the rock 10 and having the axial center hole 11a at the axial center position. Molded (FIG. 4A).

  Next, a center guide is inserted and fixed in the center hole of the specimen (S2).

  The center guide 2c is inserted into the center hole 11a in a state where the axial center direction of the center hole 11a is aligned with the axial center direction of the center guide 2c. Furthermore, it is desirable that the center guide 2c is inserted into the center hole 11a in a state where the axial center position of the center hole 11a and the axial center position of the center guide 2c are matched. In addition, the axial center position and direction of the center hole 11a and the axial center position and direction of the center guide 2c are made to correspond by using the boring machine used when forming the center hole 11a by excavation using the small bore boring 21. In this state, the center guide 2c can be inserted into the center hole 11a.

  Then, with the anchor block 2d at the lower end of the center guide 2c placed on the bottom of the center hole 11a, for example, a fixing material 8 such as mortar or adhesive is poured to securely fix the anchor block 2d to the bottom of the center hole 11a. (FIG. 4B). Thereby, the center guide 2c is fixed and installed in the center hole 11a of the test body 11.

  Next, an in-situ rock tension test device is installed on the upper surface of the test body (S3).

  Specifically, a tensile load is applied by penetrating the pressure plate 4 and the central through hole of the load measuring means 3 and the axial through hole of the piston 2b from the upper end side of the center guide 2c protruding from the ground surface of the rock 10. The means 2 (cylinder 2a, piston 2b, clamp 2e), the load measuring means 3 and the pressure plate 4 are installed on the upper surface of the test body 11 (FIG. 5A).

  At this time, the lower surface of the pressure plate 4 is bonded to the upper surface of the test body 11 by the adhesive member 6.

  Next, a tensile load is applied to the test body in the axial direction (S4).

  Specifically, the piston 2b of the in-situ rock tension test apparatus 1 installed on the upper surface of the test body 11 is moved upward and stored in the cylinder 2a by the process of S3. At this time, as described above, the reaction force exerted on the tensile load applying means 2 in accordance with the operation of the piston 2b is transmitted by the center guide 2c and controlled by the rock 10 so that the position of the tensile load applying means 2 is fixed. In this state, a tensile load is applied to the test body 11 through the load cell 3, the pressure plate 4, and the adhesive member 6 by the operation of the piston 2b.

  And if the test body 11 carries out the tensile fracture (FIG. 5 (B)), the magnitude | size of the load at that time (namely, fracture load) will be measured by the load measurement means 3 (S5). Further, the shape and properties such as the angle of the fracture surface of the specimen are observed (S6). The observation result of the shape and properties of the fracture surface confirms that the specimen 11 has definitely broken in the tensile fracture mode and is used for interpretation of the test result. However, the process of S6 is not an essential process for the present invention. And the in-situ rock tension test about the said test body 11 is complete | finished (END).

  According to the in-situ rock tension test method and test apparatus of the present invention configured as described above, the center guide 2c fixed to the axial center position of the test body 11 cut from the in-situ rock 10 is provided. Since the guide mechanism 7A that functions between the center guide 2c and the pressure plate 4 is provided, the pressure plate 4 moves along the center guide 2c so that the center hole is in the axial direction of the center guide 2c. A straight and stable (in other words, no disturbance) tensile load in the axial direction of 11a is applied to the test body 11, and the axial direction of the center guide 2c and the axial direction of the center hole 11a are tested. The test body 11 can be pulled straight in the axial direction of the body 11. In the present invention, at least the cylinder 2a is fixed and attached via the clamp 2e to the upper end of the center guide 2c whose lower end is fixed to the rock mass 10 via the anchor block 2d. The prevented tensile load is applied to the specimen 11.

  In addition, according to the in-situ rock tension test method and test apparatus of the present invention, as in the conventional crush test, a compressive load is applied to break the specimen and an ideal (ie, linear elastic) stress state. The tensile strength is not calculated on the assumption that the specimen 11 is pulled in place, and the tensile load is applied by pulling the rock specimen 11 cut in the original position, so that the fracture load when the specimen 11 undergoes tensile fracture is directly measured. Therefore, an erroneous influence due to the characteristics of the specimen is not reflected in the test result, and the tensile strength in which the characteristics of the rock mass 10 in the original position are reflected as they are can be measured in the original position. .

  Further, according to the in-situ rock tension test method and test apparatus of the present invention, by having a mechanism for suppressing vibration and shaking from both the inner and outer peripheral surfaces of the pressure plate 4, It is possible to apply a more stable tensile force (in other words, no disturbance) to the test body 11 and pull the test body straight in the axial direction.

  In addition, although the above-mentioned form is an example of the suitable form of this invention, it is not limited to this, A various deformation | transformation implementation is possible in the range which does not deviate from the summary of this invention. For example, in the present embodiment, the side guide 5 and the side guide mechanism 7B are provided, but these are not indispensable components for establishing the present invention, and are based on, for example, the expected strength of the rock mass 10 or the like. In other words, if the pressure plate 4 can be moved straight and not vibrated or shaken along the center guide 2c without these, a configuration without these may be used.

  Further, the configuration for pulling the pressure plate 4 by the tensile load applying means 2 and measuring the load at the time of pulling is not limited to the configuration in the present embodiment, and can exert upward force as shown in FIG. The jack with the piston facing upward is attached to the upper end of the center guide 2c via the clamp 2e as the tensile load applying means 2, and the load measuring means 3 is attached to the front end surface of the piston 2b of the jack 2, and the upper end portion May be attached to the upper surface of the load measuring means 3 and a frame 12 whose lower end surface is attached to the upper end surface of the pressure plate 4 may be provided. Other configurations are the same as those in the above-described embodiment. Also in this case, the load measuring means 3, the frame 12, and the pressure plate 4 are operated by the upward movement of the piston 2 b of the tensile load applying means 2 while the center guide 2 c is fixed in position with respect to the rock 10 and the test body 11. A tensile load in the axial direction is applied to the test body 11 via the adhesive member 6. At this time, the pressure plate 4 operates in a straight and stable manner in the axial direction of the specimen without being vibrated or shaken by the center guide 2c, the guide mechanism 7A, and the side guide 5 and the side guide mechanism 7B. A tensile load that is straight and not disturbed is applied to the test body 11. The frame 12 is not limited to a specific shape as long as it transmits the upward force of the piston 2b to the pressure plate 4 via the load measuring means 3, and has a U-shape with the opening facing downward. It may be a cylindrical shape whose upper end surface is closed (that is, a cup shape with the opening facing downward).

  Moreover, in this embodiment, it demonstrated on the assumption that the case where a tension test is performed in a state where the side surface is freely restrained without applying a side pressure to the outer peripheral surface and the center hole peripheral surface of the test body 11, that is, a case where a uniaxial tensile test is performed. However, a triaxial tensile test may be performed in a state in which a lateral pressure of the same magnitude is applied to the outer peripheral surface of the test body 11 and the peripheral surface of the center hole as a constraining pressure to constrain the lateral displacement. For example, as shown in FIG. 7, the test body 11 is provided with a cylindrical packer 9a and a packer 9b, which have been used in the conventional in-situ test, in the slit 10a and the center hole 11a, respectively. It is conceivable to apply a lateral pressure by adjusting the expansion and contraction of these packers 9a and 9b.

  Furthermore, according to the in-situ rock tension test apparatus of the present invention, the axial state and the radial or circumferential displacement are measured on the outer peripheral surface of the test body 11 to thereby determine the uniaxial tensile stress state (ie, the axial center. Deformation such as Young's modulus and Poisson's ratio under σa <0 = σr) or triaxial tensile stress state (ie, σa <0 <σr) where σa is the directional stress and σr is the radial / circumferential stress. Characteristics can also be obtained. When such deformation characteristics are also required, a displacement meter conventionally used for measuring the displacement of the test specimen is appropriately attached to the outer peripheral surface of the test specimen 11 in the same manner as the conventional measurement method, and the axial direction and radius are determined. What is necessary is just to measure the displacement of a direction or a circumferential direction.

DESCRIPTION OF SYMBOLS 1 In-situ rock tension test device 2 Tensile load giving means 2a Cylinder 2b Piston 2c Center guide 2d Anchor block 2e Clamp 3 Load measuring means 4 Pressure plate 5 Side guide 6 Adhesive member 7A Guide mechanism 7B Side guide mechanism 8 Fixing material 10 Rock 10a Slit 11 Specimen 11a Center hole

Claims (8)

  Forming a cylindrical slit in the bedrock and forming a test specimen by forming a center hole at the axial position of a columnar portion where the outer peripheral surface is formed by the slit and the bottom is continuous with the bedrock; A step of inserting a rod-shaped center guide into the center hole and fixing the anchor block at the lower end of the center guide to the bottom of the center hole, and a portion near the upper end of the center guide protruding from the ground surface of the rock A step of installing a pressure plate that is penetrated and placed on the upper surface of the test body and whose lower surface is bonded to the upper surface of the test body; and provided at a position near the upper end of the center guide and provided above the pressure plate. A step of applying a tensile load in the axial direction to the test body via the pressure plate using a tension load applying means fixedly attached; and A step of measuring a breaking load when the tensile load is applied, and the reaction force exerted on the tensile load applying means when the tensile load is applied is transmitted to the rock by the center guide and controlled, and the center guide In addition, when the pressure plate moves along the center guide in a state in which vibration and vibration are suppressed by the action of a guide mechanism interposed between the pressure plate and the center guide, the shaft plate is straight and turbulent. An in-situ rock mass tensile test method, characterized in that a tensile load without any stress is applied to the specimen.   In addition to the functions of the center guide and the guide mechanism, an inner peripheral surface is provided by a side guide provided to cover the outer peripheral surface of the pressure plate and a side guide mechanism interposed between the pressure plate and the side guide. 2. The in-situ rock tension test method according to claim 1, wherein the pressure plate moves from both sides of the outer periphery and the outer peripheral surface in a state where vibration and vibration are suppressed.   The in-situ rock tension test method according to claim 1 or 2, wherein a lateral pressure as a restraining pressure is further applied to the outer peripheral surface of the test body and the peripheral surface of the center hole to perform a triaxial tensile test.   The raw material according to any one of claims 1 to 3, wherein a deformation characteristic of the test body is obtained by measuring axial and radial or circumferential displacements on an outer peripheral surface of the test body. Location rock tension test method.   It is inserted into the center hole of the test body in which the outer peripheral surface is formed by being separated from the rock by a cylindrical slit and the center hole is formed at the axial center position of the cylinder continuous with the rock. Placed on the upper surface of the specimen through a center guide provided at the lower end of an anchor block fixed to the bottom of the center hole and a portion near the upper end of the center guide protruding from the ground surface of the rock A pressure plate whose lower surface is bonded to the upper surface of the test body, a load measuring means attached to the upper surface of the pressure plate, and provided above the load measuring means and fixed at a position near the upper end of the center guide. A tension load applying means attached and a guide mechanism interposed between the center guide and at least the pressure plate. The center guide transmits and controls the reaction force exerted on the tensile load applying means when applying a tensile load in the axial direction to the test body via the pressure plate, and controls the center guide. In addition, the pressure plate moves straight along the center guide in a state in which vibration and vibration are suppressed by the action of the guide mechanism interposed between at least the pressure plate and the center guide. An in-situ rock mass tensile test apparatus characterized by applying a tensile load without any disturbance to the specimen.   It is inserted into the center hole of the test body in which the outer peripheral surface is formed by being separated from the rock by a cylindrical slit and the center hole is formed at the axial center position of the cylinder continuous with the rock. Placed on the upper surface of the specimen through a center guide provided at the lower end of an anchor block fixed to the bottom of the center hole and a portion near the upper end of the center guide protruding from the ground surface of the rock A pressure plate whose lower surface is bonded to the upper surface of the specimen, a tensile load applying means fixedly attached to a position near the upper end of the center guide, and an upper end portion straddling or covering the tensile load applying means. A frame having a lower end surface attached to the upper surface of the pressure plate, a load measuring unit interposed between the tensile load applying unit and the frame, and a front And a guide mechanism interposed between at least the pressure plate and the tensile load applied when the tensile load is applied in the axial direction to the test body via the pressure plate by the tensile load applying means. Reaction force exerted on the applying means is transmitted and controlled by the center guide to the rock mass, and vibration and vibration are caused by the center guide and at least the guide mechanism interposed between the pressure plate and the center guide. An in-situ rock tension test apparatus that applies a tensile load straight and undisturbed in the axial direction to the test body by moving the pressure plate along the center guide in a suppressed state.   The original position according to claim 5 or 6, further comprising: a side guide provided to cover an outer peripheral surface of the pressure plate; and a side guide mechanism interposed between the pressure plate and the side guide. Rock tension test equipment.   A packer for applying a lateral pressure as a restraining pressure to the outer peripheral surface of the test body arranged in the slit and a lateral pressure as a restraining pressure arranged in the center hole for the peripheral surface of the center hole The in-situ rock tension test device according to any one of claims 5 to 7, further comprising a packer.

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