JPS62290B2 - - Google Patents

Description

[Detailed Description of the Invention] This invention aims to improve the shear characteristics of the ground, that is, the values of the internal friction angle φ and the adhesive force C, which are necessary for the design and turning of civil engineering works, or for disaster prevention measures such as landslides and slope failures. This relates to a test method for directly determining the amount of water under natural conditions in a borehole.

Traditionally, civil engineering work has been carried out, especially foundation ground for buildings, bridges, dams, etc., support ground for port facilities, immersed tunnels, pipelines, and other reclaimed land and sea areas.
In the investigation, design, and construction of buried pipes for roads, railways, water and sewage systems, embankments, and other supporting ground for structures in soft soil areas, it is important to consider the mechanical properties of the target ground, especially the shear characteristics of φ and C. Understanding the value is considered the most important thing,
Furthermore, when considering the stability of landslides and slope failures, it is essential to know the values of φ and C. However, at present, there is a method to determine the C value using various vane tests for very soft clay, but it is possible to accurately calculate the values of φ and C in the original ground under the natural conditions of general soil types and weathered rocks. There is no established test method for measuring it. Therefore, indoor soil and rock tests are being conducted on samples collected using samplers. This includes one-plane shear test (φ, C measurement), two-plane shear test (C measurement),
Triaxial compression tests (φ, C measurements) are available, but it is difficult to collect undisturbed samples in their natural state from sand layers, gravel layers, clayey soils with gravel, weathered rocks, etc., and it is not sufficient in practice. I can't do a proper test.

In addition, the values of φ and C can be calculated using various experimental formulas based on the correlation experimental formula with the N value of the standard penetration test and in-situ sounding tests such as pull sounding by Iskime, helical sounding, or cone penetrometer. Although determined presumptively, these are primarily indirect test methods;
The disadvantage is that there are many variations and poor reliability.

In addition, a hydraulic packer was inserted into the borehole to compress the hole wall, and the shear resistance force, that is, the shear fracture strength when the packer was pulled upward along the hole axis, was measured at each pressurization stage. A test method has been developed to measure φ and C from the relationship between applied force and shear fracture strength, but with this method, the position of Patsucar crimping gradually moves upward due to pull-out, making it impossible to measure at the same point. The stress distribution that occurs in the upper part changes in a complicated manner depending on the stratification state and the difference in the compression force of the packing car, resulting in large variations in the measured values, as well as consolidation due to disturbance of the hole wall and pressurization, and deformation due to pressure on the upper part. Therefore, there are drawbacks such as an abnormal reaction force being generated at the upper end of the packer, and the reaction force for pulling out at the hole ground surface being difficult to absorb, resulting in an increase in the size of the device.

In addition, there are drawbacks such as the inability to measure the residual shear strength after shear failure, which is important in the analysis of large displacements and landslides, and the values of φ and C in such cases. The results are hard to expect.

The present invention was developed in order to solve the drawbacks and problems of the various test methods mentioned above, and its feature is that it can be applied to the ground in its natural state even if a sample is not collected or cannot be collected. direct testing is possible.

Tests can be performed at the same point for each pressurization stage, and there is no change in the pressurized cross section during the test.

By attaching holding packers above and below the test packer, it is possible to hold the hole wall, prevent consolidation displacement and abnormal distribution of pressurized stress that occurs in the ground, and average it out, so highly reliable results can be expected. .

It is possible to measure the maximum shear strength and the residual shear strength, and the respective values of φ and C are determined.

In addition to simplifying the test equipment and making it easier to operate, there is no need for reaction equipment on the ground surface of the hole.

By replacing the test packer part, it can be applied to anything from soft ground to weathered rock with developed cracks.

Examples include.

The principle of the present invention, the configuration and operation example of the test equipment, and the analysis of test results will be described below.

(1) Principle of the present invention Figure 1 schematically shows the principle of the present invention. In this figure, 1 is a pressure packer with a pressure plate 2 attached to the surface, and 3 is a torsion rod.
This is inserted into a predetermined test position in the borehole, and when the pressure packer is expanded at a pressure of Pn using water pressure (or gas pressure, hydraulic pressure), etc., and the pressure plate is crimped to the hole wall, the crimping of the hole wall ground The radial stress generated near the surface is σn=Pn+Po−Pgn where σn: Radial stress in the ground around the hole wall (Kg/
cm ² ) Pn: Pressure supplied to pressurized packer (Kg/cm ² ) Po: Hydrostatic pressure considering groundwater level (Kg/cm ² ) Psn: Reaction force per unit area of Packer rubber (Kg/cm ² ) . Now, if we apply a rotational moment Mn to this pressure packer through a torsion rod,
A shearing strain is generated in the ground on the hole wall surface in contact with the pressure plate, and the total moment with respect to the center balances the above-mentioned rotational moment. In other words, the shear strain generated per unit area of the hole wall is τn=C+σn・tanφ where τn: Shear strain per unit area in the ground along the hole wall (Kg/cm ² ) C: Unit in the ground along the hole wall Adhesive force per area (Kg/cm ² ) φ: internal friction angle (degrees) of the ground around the hole wall, where the expansion radius of the pressure plate's outer periphery is γn and the length is Mn = ∫ ² 〓 ₀ τn... The following relationship holds: γn·dθ =2π·γn··τn =2π·γn··(C+σn·tanφ). Therefore, when the torque that provides the rotational moment is gradually increased by strain control or stress control, the ground around the hole wall surface is shear-ruptured by a shear strain force that exceeds the elastic limit. in this case,
The pressure of the pressure car is increased step by step while shifting the test position within the same stratum, and the pressure plate is crimped.
The shear fracture strength (maximum shear strain force) when a rotational moment is applied to cause shear fracture is τ
₁ , τ ₂ , ...τ _o , rotational moment M ₁ , M ₂ ...
... _Mo , the expansion radius of the pressure plate outer periphery at that time is γ ₁ , γ
₂ ...If γ _o , then M ₁ =2πγ ₁ ...τ ₁ =2πγ ₁ ...(C+σ ₁・tanφ) M ₂ =2πγ ₂・・τ ₂ =2πγ ₂・・(C+σ ₂・tanφ) 〓 M _o The following relational expression is obtained: =2πγ _o ··τ _o =2πγ _o ··(C+σ _o ·tanφ). That is, τ _o =C+σ _o ·tanφ=M _o /2π·γ _o · [n=1, 2...]. In this equation, M _o is a quantity known from the torque (external force x radius of rotation), and γ _o is a quantity known from the measurement of the outer circumferential radius of the pressurizing plate of the pressurizing packer. Therefore, τ _o
The relationship between and σ _o can be easily determined from the test results. This relational expression between τ _o and σ _o is based on σ _o on the horizontal axis, and τ _o
It represents a linear equation when the vertical axis is = M _o /2π・γ _o・, and from the slope of the straight line, tan
The values of φ and C can be determined from σ _o =0, that is, the intersection of the vertical axis τ _o and the straight line [FIG. 2].

Also, if the rotational displacement of the pressure plate due to the rotation of the pressure packer is δ _o , then τ with δ _o as a parameter
In the relationship curve between _o and δ _o (in the actual test, Pn is constant at each pressure stage, so σ _o is constant), the maximum value of τ _o is the maximum shear fracture strength τ _{o naX}
The shear strength of the part that becomes almost constant after shear failure occurs gives the residual shear strength τ _{o res} [Figure 3].

As described above, the principle of the present invention is to press the pressurized pressure plate to the hole wall, apply a rotational moment to it, and twist it to measure the maximum shear fracture strength and residual shear strength of the hole wall ground. teφ and C
The purpose is to find the value of .

(2) Test equipment configuration and operation example Figure 4 shows the pressurizing rotary packer section which is the main subject of the present invention. Further, FIGS. 5 and 6 schematically show examples of various parts and devices when this pressurizing rotary packer is set in the test hole, and explain the test method.

The names and operating conditions of each part constituting the pressurizing rotary packer section shown in FIG. 4 are as follows.

1 is a pressurizing/rotating packer, and a rubber sleeve 4 and a pressure plate 5 are attached to the outer periphery. The pressure plate 5 is divided into six plates, and the surface thereof has six uneven grooves.

Further, in order to prevent these pressure plates from shifting laterally due to rotation, a circular rod 7 is inserted into the hole 9 in the shape of a piston. The circular rod 7 passes through the rubber sleeve 4 via a seat plate 8 and is fixed to the pressure plate 5.

The pressurizing/rotating packer 1 is screwed to rotate together with a rotary rod 11 and a rotary joint 12 which also serve as water guides.

Reference numeral 2 designates an upper pressurizing fixed packer, which is separated from the water guiding/rotating rod 11 by a thrust bearing 22 and is free. 24 is a rubber sleeve attached to this police car.

3 is a lower pressurizing/fixing packer, and 11 is free and separated from the water guiding/rotating rod (lower extension rod) by a ball bearing 25.

27 is a rubber sleeve attached to this packer, and 36 is a protective cap for the lower end of the packer.

19 is a non-rotating outer pipe (casing pipe),
It is screwed and fixed to the pressurizing/fixing packer 2 at the lower end.

17 is a vertically movable inner tube (rod) connected to the vertically movable rod 14 by a rod coupling 16.

The vertically movable rod 14 is attached with a ball bearing 18 that contacts a rotation inhibiting plate 20 attached to an outer tube 19, and can freely move vertically with low friction, but its rotation is inhibited. Further, the lower part of the rotary joint 12 is inserted into the rotary joint 12, and a ball bearing 15 is attached thereto, which is protruded into an oblique groove 15 cut out in the rotary joint 12. Therefore, when the vertically movable rod 14 moves upward, the rotation joint 12 and the pressure/rotation packer 1 connected and fixed thereto will rotate to the right.

28 is a nylon tube, through which pressurized water (can be changed to gas or oil) sent from a surface pump is passed, and one side is connected to 2 by a branch pipe 29.
2 through the groove 23 of the upper pressurized/fixed packer.
The rubber sleeve No. 4 is inflated and crimped and fixed to the hole wall. At the same time, the other water is introduced into the rotary rod 11 through the nylon tube 30, which has a spiral slack for rotation, and the rubber sleeve 4 is passed through the water introduction hole 19 and piston hole 9 drilled in the pressure/rotation packer 1. The pressure plate 5 is inflated and pressed against the hole wall, and the groove 26 in the three lower pressurizing/fixing packers is inserted through the central water guide nylon tube 31 of the closing screw 21 at the lower end of the water guide rotary rod.
Through this, the rubber sleeve 27 is expanded and fixed to the hole wall by pressure.

32 is a displacement transducer (eg, sliding resistance type, differential transformer type, etc.) for measuring the expansion of the pressurizing/rotating packer and therefore the outer diameter of the pressurizing plate.
This lead wire (cable) is connected via an underwater socket 34 to a cable 35 to the surface.

Reference numeral 37 denotes a pore water pressure transducer, which is integrated with a semiconductor pressure transducer and a bola stone and is attached to the pressure plate 5 together with a surface protection wire mesh 38 by passing through a rubber sleeve with a mounting bracket 39.

This lead wire is connected to a cable 35 to the earth's surface via a temperature compensation circuit section 33 inserted into the rotating rod and waterproofed with silicone resin, and then via an underwater socket 34.

The measurement of pore water pressure is to observe the static water pressure before applying pressure to the pack, and to observe the change in excess pore water pressure during the pressurizing stage.

FIG. 5 shows that the pressurizing/rotating packer section is inserted into the borehole, and the hydraulic water pump 51 sends pressurized water through the nylon tube 28 to the branch pipe 29. ,3
The rubber sleeve is inflated, the pressure plate and the rubber sleeve are crimped and fixed to the ground of the hole wall, and in this state, the inner pipe (rod) 17 is pulled upward, thereby rotating the rotating joint 12, which also serves as a water guide and rotates. This figure shows an example of a surface device for applying rotational moment to a pressurizing/rotating packer that is integrated with a rod 11 and screwed together.

41 is a drive pipe inserted near the mouth of the borehole, and 42 is a rod holder.

43 is a hydraulic center hole jack, 44
indicates a gear type hydraulic pump. Note that these can be replaced with screw jacks or the like depending on the load condition.

Reference numeral 45 denotes a stopper for the inner tube (rod), which is installed on the center hole jack and fixed to the inner tube with a chuck screw 46.

47 is a hydraulic pressure measuring transducer of the center hole jack, which is a semiconductor pressure transducer that extracts pressure changes as an electrical signal.

48 is a displacement measurement arm fixed to the inner tube with screws, which transmits the amount of vertical movement of the inner tube to the dial gauge 49, and generates an electric signal by a displacement transducer (differential transformer, etc.) built into the dial gauge. Externally as a

Reference numeral 50 denotes a stand installed at the upper end of the outer tube, which measures the center hole jack 43.

The water pressure water pump 51 sends pressure water to the pressurizing/rotating pumper section, and is equipped with a cylinder 52 with feed/drainage scales, a receiver 53, and a water pressure gauge 54. Note that this pump can also be replaced with a gas cylinder equipped with a pressure reducing device.

Reference numeral 55 denotes an amplifier for directly reading and measuring the amount of displacement and pressure, which protects the respective detection circuits, and is also connected to a recorder (such as a dot type) 56 to record the values.

The operations for constructing the above test equipment are as follows.

The pressurizing/rotating packer parts 1, 2, and 3 are attached to the outer tube 19.
After connecting with the outer tube and inserting it into a predetermined position in the borehole, it is held with a rod holder, and the inner tube 17 is added and screwed into the rod coupling 16 and fixed.

Place the frame 50 on the upper end of the outer tube, place the center hole jack 43, and fasten the inner tube with the metal fitting 4.
5, and dial gauge 49,
Attach the hydraulic pressure measurement transducer 47 and the hoses of the hydraulic pump 44.

Connect the Patsuka water supply nylon tube to the water pressure water pump.

Amplifier 55 and recorder 56 are connected, and a dial gauge 49 (for measuring the amount of movement of the inner tube and the rotational displacement δ of the pressurizing/rotating packer) and a transducer 49 for measuring oil pressure (for measuring the inner tube lifting pressure) (For measuring shear force γ of rotary pack car), pressurizing,
Expansion/contraction displacement transducer 3 of rotary pack car
The cable terminals of the pore water pressure transducer 2 (for measuring the outer diameter d of the pressure plate) and the pore water pressure transducer 37 (for measuring the pore water pressure U) are connected to the amplifier 55, respectively.

Each part's electrical circuit and dial gauge will be verified and measurements will begin.

The water pressure pump 51 is operated to inflate the pressurizing/rotating packer 1 and the pressurizing/fixed packers 2 and 3 so that a predetermined water pressure is achieved, and the ground is pressed by the pressurizing plate. At this time, the pointer of the water pressure gauge 54 is read, and at the same time, changes in the pressure plate outer diameter d value and the pore water pressure U value are recorded for a certain period of time. Note that the pressurization/fixation packers 2 and 3 press the hole walls to maintain a uniform stress distribution in the periphery of the pressurization/rotation packer 1.

Next, the hydraulic pump 44 is operated, and the center hole jack 43 moves the inner pipe upward by approximately 1
It is hoisted while controlling strain by moving the dial gauge 49 so as to maintain a speed of mm/min. At this time, the pressure plate attached to the pressure/rotation packer 1 is rotated due to the rotational moment applied to the right by the diagonal groove 13 while it is pressed against the ground. When this displacement exceeds a certain limit, a cylindrical shear failure region occurs in the ground in the vicinity of the pressure plate.

The transition state of ground reaction force, rotational displacement, and excess pore water pressure in the process leading up to such shear failure and after that is determined by the electric signal e〓 of the hydraulic pressure measurement transducer 47 attached to the center hole jack, and the dial gauge. 49 and the pore water pressure transducer 37, and are captured and recorded as electric signals e〓, _eU, respectively.

When the above measurement operation is completed, the pressurizing/rotating packer section is moved to the upper position and fixed, and the pressurizing force of the packer is increased to the next level of water pressure and the same measurement is performed.

This packer pressurization step is performed at 3 to 5 different pressures for the same stratum in the ground. Note that measurements are also made at the same time when the pressing force is set to zero, and the relationship between τ _p to δ _o due to the weight of each part of the device and the frictional force is determined, and the above measured values are corrected.

FIG. 6 shows an example of a simplified ground test device for relatively shallow geological formations.

That is, in this example, the pressurizing/rotating packer is twisted by the ground handle directly through the inner tube. 1
Reference numeral 7 denotes an inner tube, to which a fixed ring 59 having two arms 60 and 62 is screwed and fixed by a chuck 56. A torsion handle rod 57 that rotates freely by a ball bearing 58 is placed on top of this, and a proving ring is installed between the handle rod and the arm 60 of the fixed ring. This allows the rotational force caused by this to be transmitted to the inner tube. In this case, the rotation joint shown in FIG. 5 is not necessary and is replaced with a rod coupling 40. Reference numeral 62 denotes a fixed ring arm for measuring rotational displacement, which is brought into contact with a dial gauge 63 attached to the support rod 64 of the pedestal 50 to measure the rotational displacement of the inner tube and the rotational displacement of the pressurizing/rotating packer pressurizing plate. Measure. In addition, the force meter 61 and the displacement dial gauge 63 each use a transducer to extract the amount of change as an electric signal,
It is possible to amplify the electrical signals of the pressure plate outer diameter and pore water pressure and record them on the recorder.

In addition, when using this test device, the operation is the same as in the previous example, in which the pressurizing force of the packer is changed stepwise, and the test position is shifted each time for measurement.

(3) Analysis of test results From the measurement results from the test operation of the test equipment configuration described in the previous section 2, the radial force due to the crimping of the hole wall ground δ _o , the maximum shear failure strength in the ground τ _{o nax} , and the residual shear strength τ _{o res} and the process leading to shear failure and the subsequent hole wall ground displacement δ _o can be determined, and the dynamics of the pore water pressure U can also be known at the same time. Therefore, the analysis method described in Section 1 of the principle of the present invention, that is, the relationship between σ _o and τ o in Figure 2, and _{the relationship between σ o in} Figure 3
From the relationship between δ _o and τ _o with δ o to τ o as parameters, the internal friction angle φ and adhesive force C of the ground for the maximum shear failure strength τ _{o nax} , and φ' and C' for the residual shear strength τ _{o res} are determined, respectively. Note that φ, C and φ′C′ in this case are compared with the values determined by the [CU] test of the indoor triaxial compression test.

In addition, the dynamics of pore water pressure can be used as reference material when analyzing effective pressure.

[Brief explanation of the drawing]

Figure 1 is a diagram of the principle of the test method of the present invention, Figure 2.
Fig. 3 is an explanatory diagram of analysis of the test results, Fig. 4 shows the pressurizing/rotating packer section which is the main body of the present invention, and Fig. 5/
FIG. 6 shows the configuration and operation example of the test device.

Claims (1)

[Scope of Claims] 1. An arc-shaped pressure plate having uneven grooves divided into several parts on the outer surface of a rubber sleeve-type packer that freely expands and contracts in the radial direction by fluid pressure such as gas pressure, water pressure, or hydraulic pressure. are arranged in a cylindrical shape, and this pressure plate is fixed with a mounting screw in such a way that the Paccar rubber sleeve is embedded in the same number of piston-shaped cylinders as the pressure plates that can expand and contract radially inside the Paccar rubber sleeve, and the entire As a result, a rubber sleeve-type packer and a piston-type packer are integrated to form a pressurized rotary packer. This pressurized rotary packer is inserted into a borehole at a predetermined depth, and the pressure plate is pressed against the hole wall ground with a specific pressure, and then a rotational moment is applied to the pressurized rotary packer part, and therefore the pressure plate, so that it rotates in the circumferential direction. A cylindrical shear fracture is generated in the ground in contact with the torsion and pressure plate, and the maximum shear strength and residual shear strength with respect to rotational displacement in this case are measured. Similar operations are carried out under stepwise radial pressing forces to determine the relationship between the pressing force and shear strength, and from this the values of the internal friction angle φ and cohesive force C of the ground under natural conditions are determined. Test method to determine.