JP2003227781A - Testing apparatus of load in hole for measuring underground stress - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent an area near both the ends from projecting locally and at the same time to reliably prevent pressurized oil from leaking to the outside when an elastic tube is expanded by the introduction of pressure for loading to a hole wall. <P>SOLUTION: Pressurized oil passes through a portion where a central hole 32a of a porous shaft 32 and an LVDT sensor 31 are installed from the side of an end face cap 40 and enters the inside of an elastic tube 33. Then, the elastic tube 33 increases the diameter along with a friction shell 37 that is bonded in one piece with the elastic tube 33. In this case, both the ends of the elastic tube 33 are carried to the outer periphery of the porous shaft 32 by an end cap 34 and have sealing properties and are bonded so that oil does not leak to the outside of the elastic tube 33. Output corresponding to the diameter of the elastic tube 33 is obtained by an LVDT sensor 31 that is inserted between a pair of plugs 43 and 43 screwed to a pair of sockets 42 and 42 that are provided in the elastic tube 33. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an in-hole load testing device for measuring stress or physical properties in the ground individually or simultaneously.

[0002]

2. Description of the Related Art Recently, numerical analysis technology has enabled advanced design and analysis of large-scale civil engineering structures such as tunnels, underground mines, deep underground caverns, dams, etc. In order to do so, it is necessary to secure the stress and physical properties of underground rocks including structures as input data for computer programs. This new method of measuring stress and physical properties is disclosed in Japanese Patent No. 2875204 (hereinafter referred to as "Prior Art Publication"). FIG. 6 shows the main part of the hole loading tester described in this prior art publication. The hole loading tester shown in FIG. 6 is installed, for example, at an arbitrary measurement point of a test hole excavated in the natural ground. The in-hole loading tester (hereinafter referred to as "probe") 1 includes a loading section 2 and an electric equipment section 3, which are connected by a connector. Although not shown, hydraulic control, power supply, and external operation functions such as a computer are connected to the probe 1 by a hydraulic pipe and an electric wire.

A mechanism is shown in which the loading section 2 is connected to the electric equipment section 3 by a partition side end cap 5 having a cavity 4. The loading section 2 is coupled to the electric device section 3 by screwing a female screw 6 formed at the tip of the end cap 5 with a male screw 7 a formed on the partition wall 7. The loading portion 2 of the probe 1 is integrated by screwing the three parts of the mandrel 8, the elastic tube 9 and the end seal 11 of the cushioning material with the female screw 5a formed on the end cap 5 and the male screw 8a formed on the mandrel 8. ing. The high-pressure oil introduced into the shaft center space 12 of the mandrel 8 is sealed by the O-ring 14 mounted on the tip steel pipe 13 of the elastic tube 9. The elastic tube 9 is fitted around the mandrel 8, and the high-pressure oil is elastically connected to the mandrel 8 through the oil circulation holes 8b that are radially formed in the middle portion of the mandrel 8 from the axial center space 12 of the mandrel 8. When it is introduced into the space between the tube 9 and the tube 9, its diameter increases in a bulging manner.

The elastic tube 9 is made of flexible synthetic rubber, and the end seal 11 is made of hard synthetic rubber.
As a cushioning material between the steel end cap 5 and the soft elastic tube 9, a high-pressure oil sealing function is fulfilled. The end seal 11 prevents the soft elastic tube 9 from being crushed by the high pressure oil. The friction cylinder 10 that controls the loading function of the elastic tube 9 is composed of an elastic inner layer having high tensile strength made of high-strength artificial fiber and a friction outer skin that wraps the outer surface thereof, and the fibers of the inner layer are arranged tangentially. It covers the periphery of the elastic tube 9. The friction cylinder 10 is divided into two opposing semi-cylinders by a surface defined by the axis and the diameter. Since this semi-cylindrical shell is made of steel wire mesh arranged in the axial direction, the elastic tube 9 is allowed to expand in the diametrical direction.
Axial deformation is controlled.

Due to the bulging of the elastic tube 9, all the tensile stress in the tangential direction is concentrated along the cut surface of the joint portion of the semi-cylindrical portion, and the hole wall is cracked. 2 pieces for loading section 2
A pair of anchor pins 15 are provided perpendicular to the axial direction of the friction cylinder 10 consisting of two semi-cylinders, whereby the elastic tube 9 is fixed to the mandrel 8, and the elastic tube 9
It prevents rotation and displacement in the axial direction. The displacement of the hole wall 16 in the diametrical direction due to loading is caused by a plurality of LVDTs (Linears) arranged in the elastic tube 9 in the diametrical direction.
Variable Difference Tran
sducer) sensor 17. This L
The coil and the core constituting the VDT sensor 17 are sealed in a pair of sockets 18 set in the elastic tube 9, as shown in detail in FIG. 7. That is, one socket 18 (upper side in FIG. 7) has a core 2 at the inner bottom.
A plug 19 to which a rod 22 connected to 0 is fixed is screwed by screw connection, and the other socket 18 (lower side in FIG. 7) has a solenoid coil 21 at the inner bottom.
The plug 23 to which is fixed is screwed by screwing. The LVDT sensor 17 having such a configuration is
By inserting it into a hole 24 diametrically drilled in the mandrel 8, it is possible to measure the diametrical deformation of the hole wall 16 due to the expansion of the elastic tube 9 perpendicular to its fracture surface.

[0006]

According to the hole loading tester (probe) disclosed in the prior art publications shown in FIGS. 6 and 7 and configured as described above, the elastic tube 9 and the end cap 5 are provided. The end seal 11 existing between the two ends is made of hard urethane rubber and is located between the soft elastic tube 9 and the steel end cap 5 to fulfill its cushioning function. The end seal 11 projects into the hole wall 16 because the function of preventing it from being pushed out from between the hole walls 16 is insufficient. Further, when the end seal 11 projects, the friction cylinder 10 opens and pierces the hole wall 11, and when the pressure is reduced after the measurement is completed and the hole loading tester 1 is to be pulled out, the end seal 11 and the friction cylinder 10 are closed. It pierces the wall 16 and does not return to its original position, so
It has a drawback that it becomes impossible to pull out the in-hole load testing machine 1 or it becomes extremely difficult.

Further, the conventional hole loading tester 1 shown in FIG.
The LVDT sensor 17 in FIG. 2 has no problem when the pair of elastic tubes 9 arranged so as to face each other are expanded and displaced while maintaining an ideal parallel state during expansion, but the friction cylinder 10 covering the outer circumference of the elastic tube 9 has no problem. Hole wall 16 with uneven hardness
The friction cylinder 10 and the elastic tube 9 do not move in parallel when pressed against each other, and often cause an inclination. In this way, when the elastic tube 9 is tilted, the pair of plugs 19 and 23
Since the axes of the rods are not on a straight line and intersect with each other, the rod 22 bends and the core 20 is strongly pressed against the inner wall of the solenoid coil 21 to prevent movement, as shown in FIG. There is a problem that it becomes unresponsive to displacement.

The present invention has been made in view of the above-mentioned circumstances, and a first object thereof is that when the elastic tube is expanded by the introduction of pressure, the vicinity of both ends thereof locally projects into the expansion hole. It is an object of the present invention to provide an in-hole load testing device that can effectively prevent the above. A second object of the present invention is to provide an in-hole loading test device that can appropriately prevent the oil filled inside the elastic tube from leaking outside from the joint. A third object of the present invention is to prevent cracks due to repeated shearing forces applied between the fixed portions at both ends of the elastic tube and the movable portion near both ends, and thus to prevent oil leakage to the outside of the elastic tube due to the cracks. An object of the present invention is to provide an in-hole loading test device capable of preventing the above. A fourth object of the present invention is, from the inside of the hole where the elastic tube returns to its original position and can be smoothly pulled out from the inside of the hole when the pressurization of the elastic tube is changed to the depressurized state after the completion of the hole loading test. An in-hole loading test device that can be pulled out can be provided. A fifth object of the present invention is to expand and contract the elastic tube, thereby causing a complicated deformation of a site where the LVDT sensor is installed, and even when the axis of the LVDT sensor core and the solenoid coil are deviated from each other, the elastic tube It is an object of the present invention to provide an in-hole loading test device in which the LVDT sensor can faithfully detect a displacement corresponding to the diameter of the.

[0009]

In order to achieve the first and second objects, the invention according to claim 1 presents a cylindrical type in a hole loading test device for measuring stress in the ground. A perforated mandrel having an oil passage hole formed in an intermediate portion, and elasticity that is fitted to the outer periphery of the perforated mandrel and expands by a hydraulic pressure introduced through the hollow portion of the perforated mandrel and the oil passage hole. A tube, an LVDT sensor for detecting the displacement of the elastic tube in the diametrical direction, two rigid large friction shells formed in a semi-cylindrical shape surrounding and surrounding the outer peripheral surface of the elastic tube, and the perforated mandrel. Fixed near both ends,
A pair of end caps that allow the friction shell to move in the radial direction, prevent the friction shell from moving in the axial direction, and seal the gap with the elastic tube to prevent oil from leaking to the outer periphery of the elastic tube; It is characterized by including.

In order to achieve the above first and second objects, the end cap in the invention described in claim 2 has a sealing fin that axially enters in the middle of the elastic tube in the thickness direction. It is characterized by. In order to achieve the first and second objects, the invention according to claim 3 is made of the same material as the elastic tube between the sealing fin of the end cap and the friction shell, It is characterized in that an elastic cap is provided in which an inclined surface portion that comes into contact with an inclined surface having a smaller diameter is formed as it approaches the end surface formed on the elastic tube. In order to achieve the above first, second and third objects, the invention according to claim 4 provides an adhesive agent between the elastic tube and the elastic cap that abut against the sealing fin of the end cap. The elastic tube and the inclined surface of the elastic cap are configured so that they can slide with each other when the elastic tube expands and contracts. It is what In order to achieve the first, second, third and fourth objects, the invention according to claim 5 is fixed to both end portions of the perforated mandrel, and the elastic tube is provided on the outer circumference of the friction shell. Is provided with a pair of end face caps with a gap for restricting a movable range at the time of expansion, and a restoring spring for biasing the pair of elastic shells toward the center is provided between the friction shell and the end face caps. It is characterized by being inserted.

In order to achieve the fifth object, the invention according to claim 6 is an in-hole loading test device for measuring stress in the ground, which has a cylindrical shape, and the LVDT insertion hole is oriented in the diameter direction. A perforated mandrel that has been bored, and a plug mounting hole that is fitted to the outer periphery of the perforated mandrel and that is diametrically oriented at a position corresponding to the LVDT insertion hole, and that has a hollow portion of the perforated mandrel. An elastic tube that expands by the hydraulic pressure introduced through the LVDT insertion hole, a pair of rigid friction shells formed in a semi-cylindrical shape so as to surround and surround the outer peripheral surface of the elastic tube, and the elastic tube A pair of plugs each having a concave spherical surface or an aspherical surface with a predetermined curvature, the inner end surface of which is attached to the plug mounting hole formed in the socket directly or in the middle, and each of which has a bottomed cylinder. In front of A guide case and a holding cap, each bottom of which has a convex surface formed on a convex spherical surface or a convex aspherical surface having a curvature larger than that of the concave surface of the plug respectively comes into point contact with the concave surfaces of the inner ends of the pair of plugs, and the guide. An LVDT sensor interposed between a case and the holding cap, a core of the LVDT sensor, and a spring for urging the solenoid so as to constantly press the holding case against the holding cap. Even if the shaft centers of the pair of plugs do not match during expansion and contraction, the LVDT sensor is configured to obtain an output according to the displacement in the diameter direction of the elastic tube.

In order to achieve the fifth object, the guide case in the invention described in claim 7 has an elongated bottomed cylindrical shape, and is directly connected to the core of the LVDT sensor on the central axis on the inner bottom surface side. The fixed cap holds and holds the solenoid coil of the LVDT sensor, and the solenoid coil of the guide case is slidably fitted into the cylindrical inner peripheral surface of the guide case. The spring is inserted between the solenoid and the solenoid.

[0013]

Function: An elastic tube that expands by hydraulic pressure is fitted on the outer circumference of a perforated mandrel, and two rigid large friction shells formed in a semi-cylindrical shape so as to contact the outer peripheral surface of the elastic tube are surrounded by the friction shell. Of the perforated mandrel with a pair of end caps that allow the radial movement of the rod, prevent the axial movement of the rod and seal the gap between the elastic tube and the oil to the outer circumference of the elastic tube. Fix near both ends. Due to the pressurized oil filling between the elastic tube sealed at both ends and the perforated mandrel, the elastic tube gradually swells, which causes the friction shell to push the hole wall 180 ° in opposite directions. , Generate artificial one-sided crushing. With this structure, the elastic tube is surrounded by the friction shell including both ends thereof, so that the vicinity of both ends does not bulge locally and is prevented from protruding into the hole. The diameter of the elastic tube at the time of pressure expansion is detected by the LVDT sensor.

Further, in the hole loading test device for measuring the stress in the ground, a cylindrical perforated mandrel having an LVDT insertion hole bored in the diameter direction is fitted to the outer periphery of the perforated mandrel. Then, a plug attachment hole is bored in a diametrical direction at a position corresponding to the LVDT insertion hole, and a hollow portion of the perforated mandrel and an elastic tube which is inflated by hydraulic pressure introduced through the LVDT insertion hole, A pair of large-rigidity friction shells formed in a semi-cylindrical shape so as to surround and surround the outer peripheral surface of the elastic tube, and a socket directly or in the middle of the plug mounting hole formed in the elastic tube. A pair of plugs that are mounted and have a concave surface with a predetermined curvature formed into a concave spherical surface or an aspherical surface, and a pair of plugs each having a bottomed cylindrical shape and having a curvature larger than the curvature of the concave surface of the plug. A guide case and a holding cap, each bottom of which has a convex surface formed in an aspherical surface, respectively makes point contact with the concave surfaces of the inner ends of the pair of plugs, and an LVDT inserted between the guide case and the holding cap. A spring for urging the sensor, the core of the LVDT sensor, and the solenoid to constantly press the holding case and the holding cap, and the shaft centers of the pair of plugs do not match when the elastic tube expands or contracts. Even so, since the output according to the displacement of the elastic tube in the diameter direction is obtained by the LVDT sensor, the portion where the LVDT sensor is installed is deformed in a complicated manner, and the core of the LVDT sensor and the solenoid coil are Even if the axis is displaced, it is possible to faithfully detect the displacement corresponding to the diameter of the elastic tube.

[0015]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to FIG.
~ It demonstrates in detail using FIG. First, the configuration will be described with reference to FIGS. FIG. 1 is a sectional view taken along line AA ′ of FIG. 4 showing a configuration of a first embodiment of an in-hole loading test apparatus for measuring underground stress or physical properties according to the present invention, 2 shows up and down two embodiments of the hole loading test device with a center line as a boundary, and the lower half part of the center line shows a part of the first embodiment, The upper half of the center line is a partial cross-sectional view showing a part of the configuration of the second embodiment, and FIG. 3 shows a mounting portion of the LVDT sensor used in the first embodiment of the present invention. FIG. 4 is a sectional view, and FIG.
It is a cross-sectional view taken along line 1/4. In FIG. 1 to FIG. 4, reference numeral 30 is an in-hole loading test device, and an oil flow hole is provided at the center thereof to allow the LVDT sensors 31 and 31 to penetrate therethrough with a margin and to allow pressurized oil to flow. A hollow perforated mandrel 32 is arranged. This perforated mandrel 3
The reference numeral 2 has a center hole 32a penetrating the center thereof, and a copper pipe is used as the material thereof, but a steel pipe may be used.

An elastic tube 33 made of plastic or rubber is fitted around the outer circumference of the perforated mandrel 32. Both ends of the elastic tube 33 are formed in a taper shape whose diameter gradually decreases toward the ends, and fixed length portions at both ends are formed as thin portions to serve as fastening portions 33a. The fixing portion 33a of the elastic tube 33 is
It is fastened by the sealing fins 34a of the end cap 34, and the inner surface of the fastened portion 33a has a perforated mandrel 32.
The outer surface is bonded to the inner surface of the sealing fin 34a of the end cap 34. The end cap 34 is fixed to the perforated mandrel 32 by a set screw 35, and a convex guide portion 34b is formed on the outer periphery of the end cap 34. Further, the end cap 34 is axially inserted at the middle of the elastic tube 33 in the thickness direction. A sealing fin 34a is provided, and two O-rings 36 are provided on the outer periphery of the end.
Is formed with a concave groove for fitting.

On the outer peripheral surface of the elastic tube 33, for example,
Two friction shells 37, which are made of steel and are formed in a large semi-cylindrical shape, are joined so as to surround each other, and are firmly bonded using an adhesive. The friction shell 37 has a small diameter portion 37a formed by reducing the diameters of both ends of the friction shell 37 with respect to the intermediate portion, and a convex guide portion of the end cap 34 is formed at a boundary step portion 37b between the small diameter portion 37a and the large diameter portion. 34b slidably abuts, thereby allowing the friction shell 37 to move in the radial direction and preventing the friction shell 37 from moving in the axial direction. On the outer peripheral surface of the middle portion (large diameter portion) of the friction shell 37,
A large number of linear recessed grooves or protrusions are formed in the axial direction, so that when the elastic tube 33 expands, the recessed grooves or protrusions often bite into the hole wall 16 and the semi-cylindrical contact surface is used. The tensile force is concentrated on a specific plane in the axial direction to be created, and effectively acts to cause the one-sided fracture of the hole wall.

End cap 34 and elastic tube 33
And a portion having a substantially trapezoidal cross section surrounded by the inner peripheral surface of the friction shell 37 is made of the same material as the elastic tube 33,
An elastic cap 38 having an inclined surface portion 38a that comes into contact with an inclined surface whose diameter becomes smaller toward the end surface formed on the elastic tube 33 is provided. The slant surface 38a of the elastic cap 38 and the slant surface of the elastic tube 33 are not adhered to each other so that the elastic tube 33 can relatively slide when the elastic tube 33 expands and contracts. On the slope of the elastic tube 33,
Since the contact pressure increases as the oil pressure increases by pressing the inclined surface portion 38a of the elastic cap 38, the inclined surface portion 3
Oil leakage from 8a is reliably prevented. The outer peripheral surface of the elastic cap 38 is adhered to the inner peripheral surface of the friction shell 37, and the inner peripheral surface thereof is the fin 3 for sealing of the end cap 34.
It is bonded to 4a. Female threads formed on the two end surface caps 39, 40 are screwed into male threads formed on both ends of the perforated mandrel 32, and both are coupled. Two O-rings 36 for sealing are inserted between the inner circumferences of the end face caps 39 and 40 and the outer circumference of the perforated mandrel 32.

Further, large diameter holes 39a and 40a are formed in the end surface caps 39 and 40.
Although a predetermined gap is provided between a and 40a and the small diameter portion 37a of the friction shell 37 in a state where the elastic tube 33 is contracted (applied hydraulic pressure is substantially zero), the elastic tube 33 has a predetermined gap. When expanded by the pressurized oil, this gap becomes zero, and the movable range of the elastic tube 33 during expansion is restricted. Further, between the large diameter holes 39a and 40a of the end caps 39 and 40,
A restoring spring 29 including a leaf spring and a coil spring is inserted, and the reaction of the restoring spring 29 causes the friction shell 37 to be constantly urged in the direction in which the diameter thereof is minimized. The friction shell 37 does not have a perfect cylindrical shape, but has a semi-cylindrical shape obtained by dividing the cylinder into two parts. Therefore, when the elastic tube 33 expands, the joining surface of the two semi-cylinders gradually expands and the gap becomes large. Therefore, there is a possibility that a part of the soft elastic tube 33 protrudes to the outside from that portion. Therefore, in this embodiment, the side bar 41 has a width larger than the above-mentioned gap so that the side bar 41 is arranged as shown in FIGS. As shown, the elastic tube 33 is interposed between the elastic tube 33 and the two friction shells 37.
3 and 3 are bonded by an adhesive.

Next, with reference to FIG. 1 and FIG. 3, the structure of the LVDT and the mounting structure thereof, which is the main part of the present invention, will be described. In the first embodiment, the LVDT sensor 31
Are arranged in the middle part so as to penetrate the elastic tube 33 and the perforated mandrel 32, but may be one,
You may provide three or more pieces. Since the sectional view of FIG. 1 is a sectional view taken along the line AA ′ in FIG. 4, only the upper half of the LVDT sensor 31 is shown, but the overall configuration is as shown in FIG. Elastic tube 33 and perforated mandrel 32
The sensor installation holes 33b and 32b in the diametrical direction (the direction orthogonal to the central axis) are formed in the sensor installation hole 3b.
A socket 42 is press-fitted into 3b, and a female screw formed on the inner surface of this socket 42 is screwed with a male screw formed on the outer periphery of a plug 43, whereby the plug 43 is water-tightly coupled to the socket 42. It is like this.

On the opposing surfaces of the two plugs 43 thus mounted, a concave surface 43 having a constant spherical surface or aspherical surface is formed.
a is formed. Of these two concave surfaces 43a,
One of the concave surfaces has a cylindrical shape, and the concave surface 43 of the plug 43 is
A guide case 44 is provided in which a convex surface 44a formed on a convex spherical surface or a convex aspherical surface having a curvature larger than a (in other words, a small radius) is in point contact. The other concave surface 43a has a short cylindrical shape, and the concave surface 4 of the plug 43 is
A holding cap 4 formed by point-contacting a convex surface 45a formed on a convex spherical surface or a convex aspheric surface having a curvature larger than that of 3a.
5 are provided. A rod 46 is fixed to the inner bottom of the guide case 44 in a planted state, and a core 47 is integrally connected to the tip of the rod 46. The solenoid coil 48 has a tip end side slidably fitted in the inner circumference of the guide case 44 and a base end side integrally fixed to the inner circumference surface of the holding cap 45. In this case, a spring 49, which is a coil spring, is inserted between the inner bottom surface of the guide case 44 and the solenoid coil 48, and the convex surface 44a of the guide case 44 and the convex surface 45a of the holding cap 45 are inserted by this spring 49.
However, the concave surface 43a of the plug 43 and the concave surface 4 of the other plug 43
3a is configured to be biased by a spring so that it is always in pressure contact with 3a.

In the first embodiment thus constructed, the oil pressurized by the pump (not shown) is
When the oil is introduced into the central hole 32a of the perforated mandrel 32 from the end face cap 40 side, the oil flows from the portion where the LVDT sensor 31 is installed to the outer peripheral surface of the perforated mandrel 32 and the elastic tube 33.
Enters the inner circumference of the elastic tube 33 and the elastic tube 33 swells,
A friction shell 37 glued together increases its diameter. At this time, both ends of the elastic tube 33 are carried on the outer periphery of the perforated mandrel 32 by the end caps 34, and are sealed and bonded, so that oil does not leak to the outside of the elastic tube 33. At both ends of the friction shell 37, the boundary step portion 37b is restricted from moving in the axial direction by the convex guide portion 34b of the end cap 34, so that the friction shell 37 is moved substantially in parallel.
The diameter thereof is increased, and the linear groove formed on the outer peripheral surface thereof digs into the hole wall 16 in the ground to concentrate the tangential tensile force along the opposing surfaces of the two opposing semi-cylindrical cylinders, and finally to the semi-cylindrical cylinder. Separation is made in two directions with the original joint surface of as a boundary.

As a result, regardless of the complexity of the physical properties of the ground including the latent or actual cracks around the hole wall 16, the direction of the crack surface generated by loading always coincides with the fracture surface that is set arbitrarily. This one-sided crushing control method enables practical measurement of stress and physical properties in complex ground. Next, the operation of the LVDT sensor 31 will be described with reference to FIGS. 1, 3 and 5. As described above, the hole wall 16 is also expanded by the pair of semi-cylindrical friction shells 37 as the elastic tube 33 increases in diameter direction by the high pressure hydraulic pressure introduced from the central hole 32a of the perforated mandrel 32. At this time, an output corresponding to the diameter of the elastic tube 33 is obtained by the LVDT sensor 31 inserted between the pair of plugs 43, 43 screwed into the pair of sockets 42, 42 provided in the elastic tube 33. To be

Here, the solenoid coil 48 and the core 4
The LVDT sensor 31 composed of 7 includes a guide case 44 having a convex surface 44a whose bottom surface is a convex spherical surface or a convex aspherical surface.
And a holding cap 45 having a convex surface 45a composed of a convex spherical surface or a convex aspherical surface. Therefore, when the elastic tube 33 is not displaced in parallel, that is, when the elastic tube 33 is displaced in a tilted manner as shown in FIG. 5, the guide case 44 holding the core 47 and the holding cap 45 holding the solenoid coil 48 are also tilted. Since a pressure-expansion elastic force is constantly applied between the two, and the convex surfaces 44a and the convex surfaces 45a thereof are in point contact with the concave surface 43a having a larger curvature, the solenoid coil 48 and the core 47 (rod 46) are
Since the central axes of both are substantially on the same straight line, the core 47 is
Since the solenoid coil 48 moves smoothly and faithfully to the displacement, the displacement corresponding to the diameter change of the elastic tube 33 can be always measured by the LVDT sensor 31.

It should be noted that the present invention can be variously modified and implemented without departing from the spirit of the present invention regardless of the above-described and illustrated embodiments. For example, according to the first embodiment of the present invention, an example in which the elastic cap 38 is provided as shown in the lower half of FIG. 2 is shown, but as shown in the upper half of FIG. Instead of providing the cap 38, the friction tube 33 may be extended and integrated. However, in the case of such a configuration, the sealing fins 34a of the end cap 34, which functions as a hinge when the elastic tube 33 expands / contracts, of the elastic tube 33.
Since a large shear strain is generated at the tip portion 34c of the above, the tip portion 34c may be cracked during a long period of time.

There is no problem if the cracks generated at this time stay inside the elastic tube 33, but if they reach the outer peripheral portion, oil leakage occurs, which causes a problem. Therefore, it is desirable that the first embodiment, that is, the lower half of FIG. What happens is Figure 2
If the elastic tube 33 is configured as in the lower half of the elastic tube 33, for example, when the elastic tube 33 is expanded, the slope of the elastic tube 33 is displaced along the slope 38a of the elastic cap 38 while causing a slip, and therefore, for sealing. No large shear strain is generated in the elastic tube 33 near the fins 34a, and cracks are less likely to occur even after long-term use. Further, by configuring as in the lower half of FIG. 2, when the elastic tube 33 is expanded, the slope of the end of the elastic tube 33 has a slope 38 a of the elastic cap 38.
The oil leaks from the contact part as
Certainly blocked. However, the oil that has entered between the outer circumference of the perforated mandrel 32 and the elastic tube 33 has entered the sealing fin 34a of the end cap 34 along the axial center and up to the middle portion in the thickness direction of the elastic tube 33. In addition to the elastic tube 33 being adhered to the sealing fins 34a with an adhesive, the higher the applied pressure of oil, the more the fastening portion 33a of the elastic tube 33.
Is strongly pressed against the sealing fin 34a, so that oil leakage from this portion can be reliably prevented.

[0027]

As is clear from the above description, according to the invention described in claim 1, in the hole loading test apparatus for measuring the stress in the ground, a cylindrical type is used and the oil flow in the middle portion A perforated mandrel having a hole formed therein, an elastic tube fitted to the outer periphery of the perforated mandrel, and expanded by a hydraulic pressure introduced through the hollow portion of the perforated mandrel and the oil flow hole, and the elasticity. Two semi-cylindrical friction shells, which are formed in a semi-cylindrical shape and are in contact with the outer peripheral surface of the tube, and are fixed in the vicinity of both ends of the perforated mandrel, respectively, to allow the friction shell to move in the radial direction, Since a pair of end caps that prevent movement in the direction and seal between the elastic tube and prevent oil from leaking to the outer circumference of the elastic tube are provided, the elastic tube is pressurized. Guided oil When expanded by, the vicinity of both ends can be prevented from protruding locally within bulged hole wall,
It is possible to provide an in-hole loading test device that can appropriately prevent the oil filling the inside of the elastic tube from leaking from the joint.

According to the second aspect of the present invention, since the end cap has a sealing fin that axially extends in the middle of the elastic tube in the thickness direction, the elastic tube seals when pressurized. It is possible to provide an in-hole load testing device that can be pressed against the fins to further increase the sealing effect. Further, according to the invention as set forth in claim 3, between the sealing fin of the end cap and the friction shell, it is made of the same material as the elastic tube, and approaches the end surface formed on the elastic tube. Along with this, since an elastic cap having a slanted portion that comes into contact with a slanted surface having a small diameter is formed, the repeated shearing force at the end of the elastic tube is reduced while improving the sealing effect and the occurrence of cracks. Therefore, it is possible to provide an in-hole loading test device capable of suppressing oil leakage and preventing oil leakage to the outside of the elastic tube due to cracking.

According to the invention as set forth in claim 4, a seal is provided between the elastic tube and the elastic cap, which are in contact with the sealing fin of the end cap, with an adhesive, and the elastic tube is sealed. Since the slant surface and the slant surface portion of the elastic cap are configured to be able to slide with each other when the elastic tube expands and contracts, the effect of the invention according to claim 3 is further exerted. It is possible to provide an in-hole load testing device to be obtained. According to the invention of claim 5, a pair of end faces is fixed to both end portions of the perforated mandrel, respectively, and there is a gap on the outer periphery of the friction shell for restricting a movable range of the elastic tube at the time of expansion. Since a cap is provided and a restoring spring that biases the pair of elastic shells in the center direction is interposed between the friction shell and the end face cap, after completion of the hole loading test,
When the pressure applied to the elastic tube is changed to the pressure reduced,
Since the friction shell and the elastic tube are forcibly displaced in the center direction, that is, in the original position direction by the restoring spring, it is possible to provide an in-hole load testing device that can easily pull out the entire in-hole load testing device from the inside of the hole.

According to the invention described in claim 6, in the hole loading test device for measuring the stress in the ground, a cylindrical perforated mandrel having LVDT insertion holes bored in the diameter direction, The plug fitting hole is fitted in the outer periphery of the perforated mandrel, and a plug mounting hole is diametrically formed at a position corresponding to the LVDT insertion hole, and is introduced through the hollow portion of the perforated mandrel and the LVDT insertion hole. Elastic tube that expands due to hydraulic pressure,
A pair of semi-cylindrical friction shells formed in a semi-cylindrical shape so as to surround and surround the outer peripheral surface of the elastic tube, and a socket directly or in the middle of the plug mounting hole formed in the elastic tube. And a pair of plugs each having an inner end surface formed into a concave spherical surface or a convex aspherical surface having a predetermined curvature, each having a bottomed cylindrical shape, and having a curvature larger than the curvature of the concave surface of the plug. Each bottom portion having a spherical or aspherical convex surface is inserted between the guide case and the holding cap, which make point contact with the concave surfaces of the inner ends of the pair of plugs, respectively. The LVDT sensor, the core of the LVDT sensor, and a spring for urging the solenoid to constantly press the holding case against the guide case, and the elastic tube expands. Since also the axis of the pair of the plug during storage is not matched an output corresponding to the displacement in the diameter direction of the elastic tube is constructed as obtained by the LVDT sensor, the expansion of the elastic tube, along with the shrinkage LV
Even if the part where the DT sensor is installed is complicatedly deformed, it automatically acts to match the center lines, and the axis of the LVDT sensor core and the solenoid coil do not shift, so it corresponds to the diameter of the elastic tube. It is possible to provide an in-hole loading test device in which the LVDT sensor can faithfully detect the displacement.

According to the invention of claim 7, the guide case has an elongated bottomed cylindrical shape, and a rod directly connected to the core of the LVDT sensor is fixedly held on the central axis on the inner bottom surface side. The holding cap firmly holds and holds the solenoid coil of the LVDT sensor, and the solenoid is slidably fitted on the inner peripheral surface of the cylinder of the guide case, and the solenoid coil is provided between the inner bottom surface of the guide case and the solenoid coil. Since the spring is inserted, it is possible to provide an in-hole loading test device capable of exerting the effect of the invention according to claim 6 further.

[Brief description of drawings]

FIG. 1 is a cross-sectional view taken along line AA ′ of FIG. 4 showing the configuration of a first embodiment of an in-hole loading test apparatus for measuring underground stress or physical properties according to the present invention. .

FIG. 2 shows two embodiments of an in-hole load testing device above and below with a center line as a boundary, and a lower half part of the center line shows a part of the first embodiment. The upper half of the center line is a partial cross-sectional view showing the configuration of part of the second embodiment.

FIG. 3 shows L used in the first embodiment of the present invention.
It is sectional drawing which shows the mounting part of a VDT sensor.

4 is a transverse cross-sectional view taken along line BB ′ of the hole loading test device shown in FIG.

FIG. 5 is a schematic diagram for explaining the action of the LVDT sensor used in the hole loading test device according to the first embodiment.

FIG. 6 is a vertical cross-sectional view showing the configuration of a conventional hole loading tester.

FIG. 7 is an L used in the hole loading tester shown in FIG.
It is sectional drawing which shows the detailed structure of a VDT sensor.

FIG. 8 is a schematic diagram illustrating the operation of the LVDT sensor shown in FIG.

[Explanation of symbols]

16 hole wall 29 Restoration spring 30 Hole loading test device 31 LVDT sensor 32 Perforated mandrel 32a central hole 32b, 33b Sensor installation hole 33 Elastic tube 33a Fastening part 34 End Cap 34a Seal fin 34b Convex guide part 34c tip 35 setscrew 36 O-ring 37 Friction shell 37a Small diameter part 37b Boundary step 38 Elastic Cap 38a slope part 39a, 40a Large diameter hole 39,40 End cap 41 Sidebar 42 socket 43 plugs 43a concave 44 Information case 44a, 45a convex surface 45 retention cap 46 rod 47 core 48 solenoid coil 49 springs

Claims (7)

[Claims] 1. An in-hole load testing device for measuring stress in the ground, which fits on a perforated mandrel having a cylindrical shape and an oil passage hole formed in an intermediate portion, and an outer circumference of the perforated mandrel, An elastic tube that expands due to the hydraulic pressure introduced through the hollow portion of the perforated mandrel and the oil circulation hole, an LVDT sensor that detects a displacement in the diameter direction of the elastic tube, and an outer peripheral surface of the elastic tube that is in contact with the elastic tube. The two semi-cylindrical surrounding friction shells having large rigidity and fixed near both ends of the perforated mandrel, respectively, allow the friction shell to move in the radial direction and prevent the friction shell from moving in the axial direction. And a pair of end caps that seal between the elastic tube and prevent oil from leaking to the outer circumference of the elastic tube. 2. The hole loading test apparatus according to claim 1, wherein the end cap has a sealing fin that axially extends in a middle of a thickness direction of the elastic tube. 3. The same material as that of the elastic tube is provided between the sealing fin of the end cap and the friction shell, and the diameter becomes smaller toward the end surface formed on the elastic tube. The hole loading test apparatus according to claim 1, further comprising: an elastic cap having an inclined surface portion that is in contact with the inclined surface. 4. An adhesive is used to seal between the elastic tube and the elastic cap that come into contact with the sealing fin of the end cap, and the inclined surface of the elastic tube and the inclined surface portion of the elastic cap. The hole loading test device according to claim 3, wherein the elastic tube and the elastic tube are configured so as to be able to slide with each other when the elastic tube expands and contracts. 5. A pair of end face caps fixed to both ends of the perforated mandrel and provided on the outer circumference of the friction shell with a gap for restricting a movable range of the elastic tube at the time of expansion, and The hole loading test apparatus according to claim 1, wherein a restoring spring that urges the pair of elastic shells toward the center is interposed between the friction shell and the end cap. 6. An in-hole load testing device for measuring stress in the ground, and a cylindrical perforated mandrel having an LVDT insertion hole bored in a diameter direction, and an outer periphery of the perforated mandrel. Then, a plug attachment hole is bored in a diametrical direction at a position corresponding to the LVDT insertion hole, and a hollow portion of the perforated mandrel and an elastic tube which is inflated by hydraulic pressure introduced through the LVDT insertion hole, A pair of semi-cylindrical friction shells formed in a semi-cylindrical shape so as to surround and surround the outer peripheral surface of the elastic tube, and a socket directly or in the middle of the plug mounting hole formed in the elastic tube. And a pair of plugs each having an inner end surface having a concave spherical surface having a predetermined curvature or a concave surface formed into a concave aspherical surface, and each having a bottomed cylindrical shape, and having a curvature larger than the curvature of the concave surface of the plug. Or A guide case and a holding cap, each of which has a convex surface formed in an aspherical surface, is in point contact with the concave surfaces of the inner ends of the pair of plugs, and an LVDT interposed between the guide case and the holding cap. A spring for urging the sensor, the core of the LVDT sensor, and the solenoid to press the guide case and the holding cap at all times, and the axial centers of the pair of plugs do not match when the elastic tube expands or contracts. In particular, the hole loading test device is characterized in that the LVDT sensor is configured to obtain an output corresponding to a displacement in the diameter direction of the elastic tube. 7. The guide case has an elongated bottomed cylindrical shape, and fixedly holds a rod directly connected to the core of the LVDT sensor on the central axis on the inner bottom surface side, and the holding cap of the LVDT sensor. A solenoid coil is fixedly held, the solenoid is slidably fitted into a cylindrical inner peripheral surface of the guide case, and the spring is interposed between the inner bottom surface of the guide case and the solenoid coil. The in-hole load testing device according to claim 6.