JP6449075B2 - Sounding test method and sounding test apparatus - Google Patents

Description

  The present invention relates to a sounding test apparatus and a sounding test method for obtaining characteristic values for obtaining the liquefaction strength, dynamic deformation coefficient, etc. of the ground.

  The most reliable and popular liquefaction strength test method is that a sample that is not disturbed is collected from the site and a specimen is created, and a restraint pressure close to the ground stress of the original ground is applied to this, A repeated loading test is performed, and the loading stress at which the compression and extension strain of the specimen reaches DA = 5% after 20 repeated loadings is defined as the liquefaction strength. This test is a non-drainage repeated test in which the void of the specimen is completely saturated and the pore water pressure does not escape during the loading test. Such a test provides highly reliable ground information, but it is expensive, has a high level of testing technology, and cannot be used for irregular natural ground. It is desirable to improve the overall survey accuracy by using it together with sounding to obtain values.

  The most popular sounding in Japan is the Standard Penetration Test (SPT), which usually determines the number of hits N required to penetrate a standardized tube at a depth of 1 m 30 cm from the bottom of the borehole. The most popular method in the world is the cone penetration test (CPT), which measures the penetration resistance of a pointed cone. The Swedish sounding (SWS), which is often used recently in small-scale surveys in Japan, is a method in which a weight is placed on a rod with a resistor that twists a quadrangular pyramid and penetrates. is there. These investigation methods are merely methods for obtaining penetration resistance, and SPT is time consuming and not a simple investigation method. In addition to this, in soft viscous soils, etc., pressure is a vane shear static test (V) in which a cross vane is attached to the tip of the rod and penetrates into the ground to determine the rotational resistance, and a stress-controlled loading test using a boring hole. There is a meter test (PMT). The above survey methods are standardized.

  In addition to the above, there is a method in which a blade is attached to the outer side of the tip shoe portion of the SPT penetrating pipe and rotated to simultaneously obtain the N value and the shear strength (Patent Document 1). For shallow ground, a simple test method is proposed to determine the adhesive strength c and the internal friction angle φ from the load and torque by attaching four vertical blades to the cone and rotating it while pushing the cone with a rod. (Patent Document 2). These are simple methods but not dynamic physical property surveys.

  In addition, the vane mounted on the inverted truncated cone is rotated while penetrating a gentle gradient inverted truncated cone of 5 degrees or less and performing a displacement controlled lateral loading test. From the torque under the loaded condition, or the inverted truncated cone A method for obtaining a deformation coefficient E in addition to the strength constant cφ by shearing the ground with the surface while penetrating the surface with a rough finish (Patent Document 3). A method has also been proposed in which wings are attached to the outer periphery of the PMT sonde, the torque is measured by rotating in a pressurized state, and cφ is obtained (Patent Document 4). These survey methods are not repeated loading but also monotonic loading / shear test methods.

  In addition, a method (Patent Document 5) has been developed in which a shear plate with slits on the rough surface is attached to the outside of the PMT, and the cφ and the ground deformation coefficient E are obtained by lifting upward while shearing the ground while applying lateral pressure. Although it has been put to practical use, this is also a static strength / deformation test. On the other hand, as a method for obtaining dynamic ground information from the PMT, a dynamic pressurizing device for a borehole wall has been developed (Patent Document 6). In addition, vibration cones (Patent Document 7 and Patent Document 8) for obtaining the liquefaction strength by CPT have been developed. As described above, all of them require advanced equipment and technology, and have not yet been put into practical use.

  In addition, step blade static earth pressure measurement method (SBT) with thicker intrusion blades and earth pressure gauges attached to each step, and tapered blade method to measure earth pressure by penetrating blades with a thicker top part with a gentle gradient. (TBT) has also been proposed, and a dilatometer (Patent Document 9) in which a soil pressure gauge that is inflated with air pressure is installed at the center of the blade has been devised (Patent Document 10).

  As described above, since the engineering characteristics of the ground vary widely depending on the sedimentary environment, it is desired that the ground survey be performed almost continuously in the depth direction at a number of points by a simple and speedy survey method. In addition, the ground is not a simple elastic body, but its physical properties depend on particle size, particle shape, delicate contact state of soil particles, density, hardness, caking degree, strain level, number of repeated loadings, strain rate, deposition age, restraint stress, etc. The value changes. In particular, the liquefaction strength is a physical property value that is most greatly affected. Therefore, in order to obtain dynamic physical properties for examination such as liquefaction, it is necessary to measure the behavior when repeated loading / deformation is repeated many times without disturbing the original ground as much as possible.

  However, the penetration tests (SPT, CPT, WSW, etc.) that are often used are not true ground values other than the penetration resistance because the surrounding ground is disturbed at the time of penetration. Therefore, in order to obtain the ground physical properties other than the penetration resistance by penetrating the resistor, care must be taken so that the ground of the measurement surface is not disturbed as much as possible. However, it has not been put into practical use as a research survey because of its complicated mechanism as opposed to simple sounding. The above-mentioned MST is a displacement control type and a simple investigation method, but does not satisfy the multi-cycle repeated loading condition.

JP 2001-020268 A JP 2003-227786 A JP 2007-239444 A JP2013-144922A JP 2001-32252 A Japanese Utility Model Publication No. 51-153701 Japanese Patent Laid-Open No. 58-5655 JP 2004-347490 A Japanese Patent Laid-Open No. 3-189537 JP 2014-190041 A

  In view of the above-mentioned conventional drawbacks, the present invention performs sounding in which a characteristic value for determining the liquefaction strength, dynamic deformation coefficient, etc. of the ground is simply and quickly obtained by performing repeated lateral loading tests in-situ. An object is to provide a test apparatus and a sounding test method.

  In other words, simple and speedy investigation and repeated loading with as little disturbance as possible. In an actual liquefied ground, the entire ground is repeatedly subjected to shear deformation by earthquake motion during an earthquake, and the skeletal volume of soil particles contracts in the liquefied ground. In such a state over a wide area, the groundwater cannot move (drain) in a short time, so the pore water pressure rises, and the contact pressure of the soil particles falls and liquefies.

Therefore, as described above, the indoor liquefaction strength test is a non-drainage repeated loading test, but since the sounding is a local repeated loading, the undrained condition is not satisfied.
However, since the surrounding soil particle skeleton of the sounding resistor contracts, the earth pressure acting on the resistor decreases, and the stress acting between the soil particles decreases, so the strength of the sand ground decreases. .

  Therefore, if the change characteristics such as the rotational resistance torque and earth pressure due to repeated loading are measured, the liquefaction strength can be easily estimated with higher accuracy than the conventional sounding technique.

In order to achieve the above object, according to the present invention, a hollow resistor having a cutting shoe is connected to the tip of a rod, and this is penetrated into the ground to measure the resistance at a measurement depth, thereby deepening the properties of the soil layer. A sounding test method for examining in a lateral direction, wherein the hollow resistor has a major axis whose section taken along the horizontal plane of the upper end is larger than the diameter of the cutting shoe and a minor axis that is equal to or smaller than the diameter of the cutting shoe. It has an elliptical shape with a diameter and a loading unit with an inclination in the penetration direction connecting the vertices of the major axis of 5 degrees or less, and rotates while penetrating the hollow resistor into the ground or penetrating it. The lateral repeated loading test is performed by either of the above, and the rotational resistance torque generated in the loading unit described above is measured to determine the dynamic characteristic value of the ground.

In addition, the present invention is a sounding test in which a hollow resistor provided with a cutting shoe is connected to the tip of the rod, and this is penetrated into the ground to measure the resistance at the measurement depth to examine the properties of the soil layer in the depth direction. The hollow resistor is composed of a load transmission tube that transmits the innermost load, and a loading unit that is provided on the outer periphery of the load transmission tube via a torque transmission plate, The loading unit has an elliptical shape in which a cross-sectional shape cut by a horizontal plane at the upper end portion has a major axis diameter larger than that of the cutting shoe and a minor axis diameter equal to or smaller than the diameter of the cutting shoe, and the apex of the major axis is It is characterized in that the tangential penetration gradient is 5 degrees or less.

As is clear from the above description, the present invention has the following effects.
(1) In the first aspect of the invention, it is possible to start a load test repeatedly in the transverse direction assuming an earthquake external force from a state in which the ground disturbance is suppressed, and to continuously and speedily investigate in the depth direction with a simple device. And dynamic ground property values can be obtained.
(2) The invention of claim 2 can also obtain the same effect as the above (1), and after inserting the resistor without rotating to obtain the static physical property value of the ground, the dynamic physical property value by rotating And the survey can be conducted more quickly.
(3) The invention of claim 3 can obtain the same effects as the above (1) and (2), and not only dynamic physical properties such as liquefaction but also static mechanical constants are obtained by one investigation. .
(4) According to the invention of claim 4, the same effect as the above (1) can be obtained.
(5) The invention of claim 5 can achieve the same effect as the above (1).
(6) The invention of claim 6 can obtain the same effect as the above (1), and since it has a flat portion, it is not affected by through-input, so that the characteristic value can be measured with higher accuracy.
(7) The invention of claim 7 can obtain the same effect as the above (1), can be performed more speedily, and can be measured even if some gravel is mixed.
(8) The invention according to claim 8 can achieve the same effects as the above (1) to (3).

BRIEF DESCRIPTION OF THE DRAWINGS Schematic explanatory drawing of the 1st form for implementing this invention. The front view of the resistor of the 1st form for carrying out the present invention. The longitudinal cross-sectional view of the 1st form for implementing this invention. FIG. 4 is a sectional view taken along line 4-4 of FIG. FIG. 5 is a sectional view taken along line 5-5 of FIG. Schematic explanatory drawing of the 2nd form for implementing this invention. The front view of the resistor of the 2nd form for carrying out the present invention. The longitudinal cross-sectional view of the 2nd form for implementing this invention. Schematic explanatory drawing of the 3rd form for implementing this invention. The front view of the resistor of the 3rd form for carrying out the present invention. The top view of the resistor of the 3rd form for carrying out the present invention. Schematic explanatory drawing of the 4th form for implementing this invention. The front view of the resistor of the 4th form for carrying out the present invention. FIG. 14 is a sectional view taken along line 14-14 of FIG.

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

  In the first embodiment for carrying out the present invention shown in FIGS. 1 to 5, reference numeral 1 denotes a sounding test method for obtaining characteristic values for obtaining the liquefaction strength, dynamic deformation coefficient, etc. of the ground. Reference numeral 1 denotes a resistor 2 having a cylindrical cutting shoe 5 connected to the tip of a rod 2, and this is penetrated into the ground 4 to measure the resistance at a measurement depth to examine the properties of the soil layer in the depth direction. In the sounding test method 1, the hollow resistor 3 at the lower end has a cross section having a major axis diameter larger than the diameter of the cutting shoe 5 and a minor axis diameter equal to or smaller than the diameter of the cutting shoe 5. The hollow resistor 3 is provided with a plurality of loading units 6 each having an elliptical elliptical truncated cone having a gentle gradient ridge line with an inclination of 5 degrees or less, which has an elliptical shape and connects the vertices of the major axis. The And while penetrating, or subjected to lateral cyclic loading test is rotated from by penetration, rotational resistance torque generated in each loading unit 6 measures seeking dynamic characteristic values of the ground during.

  The sounding test apparatus 7 used in the sounding test method 1 is such that a resistor 3 having a cutting shoe 5 is connected to the tip of the rod 2, and the resistor 3 is the innermost load. A load transmission tube 8 that transmits (penetration input and rotational force), and a long axis diameter that is provided on the outer periphery of the load transmission tube 8 via a torque transmission plate 9 and whose upper end is larger than the diameter of the cutting shoe 5. And an elliptical elliptical truncated cone having a gentle gradient ridge line with a gradient in the penetrating direction connecting the vertices of the major axis and having a slope of 5 degrees or less. It is composed of a loading unit 6.

  In the present invention, the gradient in the penetration direction refers to a gradient in a case where the major axis top portion from the upper end portion of the loading unit to the lower end portion is connected by a straight line. Further, the tip end of the rod 2 refers to the lower end in FIG. 1, that is, the portion connected to the hollow resistor 3, and the upper end of the loading unit 6 is the upper end in FIG. The part refers to the lower end in FIG.

The load unit 6 described above includes a plurality of load units 6a, 6b, 6c, and 6d that are divided in a penetration direction and a vertical direction (horizontal direction), and a torque transmission plate is arranged on the outer periphery of the load transmission tube 8 via a torque transmission plate 9. It is fixed to the load transmission tube 8 with a fixing screw 10 and a torque transmission plate anchor 11. The elastic packing 12 is sandwiched between the loading units 6a, 6b, 6c, and 6d, and when the four sets of loading units 6a, 6b, 6c, and 6d are set in the cable path 13 and set, the protection unit 14 is provided. The load transmission pipe 8 is connected, and a load transmission gate type column 15 for soil removal and load transmission is set on the head. Further, a ground pressure gauge 17 and a pore water pressure gauge 18 are embedded along a gradient (ridge line 16) in the penetration direction connecting the tops of the major axes of the loading unit 6.
The minor axis diameter of the ellipse is the same as the outer diameter of the cutting shoe 5 from the lower end to the upper end. Therefore, the lateral stress of the ground at the time of intrusion is set as the lower limit, and the elliptical shape is deformed laterally by the increment of the major axis diameter, and the load test is repeated twice per rotation. This is a controlled cyclic loading test.

  The resistance 3 penetrates into the ground with the resistance 3 penetrated as much as possible while digging inside, and the resistance 3 penetrates into the ground and rotates repeatedly to carry out repeated loading tests. Ask for. Using these data, the ratio Tr of the first torque corresponding to Nc = 20, 40, 80 times is obtained from the relationship between the number of repetitions Nc and the torque, and a relational expression with the conventional liquefaction strength by the laboratory test or the like is derived. The estimated liquefaction strength in the depth direction of the ground to be measured is obtained.

  The cutting shoe 5 is connected to the lower end portion of the load transmission tube 8 that transmits the innermost load (through force and rotational force) of the resistor 3.

  If the cutting shoe 5 having a smooth surface is attached to the lower end portion of the resistor 3 and it penetrates while discharging the earth and sand inside, the disturbance of the measurement ground due to the penetration can be suppressed. Between the circular shape at the lower end and the elliptical shape at the upper end, the length of the resistor is a gentle gradient of 5 degrees or less parallel to the penetration axis, and the elliptical inverted frustum rotation resistor with a smooth finish that is linearly changed between them. By doing so, it is possible to carry out lateral loading twice for each rotation from a slight strain to a continuously large strain.

  By the rotation of the resistor 3, it is possible to perform a repeated loading test for displacement control with the horizontal stress of the natural ground acting on the peripheral surface of the cutting shoe 5 as a lower limit or a neutral stress axis. The resistor 3 is changed from a circular shape at the lower end to an elliptical shape at the upper end in the axial direction, and loaded laterally by rotation of a loading unit 6 in which the resistor 3 is divided into three or more parts. In addition to the torque generated in the test, it is possible to measure the contact pressure with the ground at the top of the major axis diameter, pore water pressure, and the like.

  The test penetrates the inside of the resistor while excavating it, and when the resistor 3 reaches the measurement depth, it rotates without penetrating. The liquefaction strength is determined from the correlation between the liquefaction strength and the liquefaction strength obtained by indoor undrained repeated tests.

  In order to test more speedily, if a repeated loading test is performed 20 times at 10 rotations while penetrating at a constant speed for the length of the resistor, repeated loading is performed continuously from a slight strain level to a large strain at each measurement depth. By setting the wave to 20 waves at the time of maximum displacement loading, it is possible to obtain the liquefaction strength equivalent value. This is a test method that linearly approximates a displacement amplitude curve in which a strain reaches 5% after 20 loadings in an indoor undrained repeated test. However, since the strain level in the repeated rotation loading test of the ellipsoid corresponding to 5% strain in the laboratory test is not the same, it will wait for measurement results for various grounds in the future.

There are a method of temporarily storing the measurement data in a memory unit provided at the lower end of the rod 2 for penetration rotation (not shown) and a method of wirelessly transmitting a cable through the rod 2 on the ground. The intermediate moat of the resistor 3 is formed by an already-known muddy water jet or the like using a ground device (not shown), and the rotation penetration can be performed by an automated SWS device that has already been put into practical use.
In the present embodiment, the elliptical minor axis diameter of the loading unit 6 is formed to be the same as the outer diameter of the cutting shoe 5 from the lower end to the upper end. However, the present invention is not limited to this, and the minor axis The diameter may be smaller than the outer diameter of the cutting shoe.

[Different forms for carrying out the invention]
Next, different modes for carrying out the present invention shown in FIGS. 6 to 14 will be described. In the description of the different embodiments for carrying out the present invention, the same components as those in the first embodiment for carrying out the present invention are denoted by the same reference numerals, and redundant description is omitted.

  The second embodiment for carrying out the present invention shown in FIGS. 6 to 8 is mainly different from the first embodiment for carrying out the present invention in that each is parallel (perpendicular) to the penetration direction. Inclination of the loading unit in which the flat surface 19 and the inclined surface 20 are formed below the flat portion 19 and the long radius of the flat portion 19 of the loading unit connected to the lower side via the elastic packing 12 is connected upward. Sounding test using a resistor 3A provided with a loading unit 6A formed so as to be substantially the same as the long radius of the lower end portion of the surface 20 and having a gradient in the penetration direction of 5 ° or less as a whole of the plurality of loading units 6A. Even in such a configuration, the same effect as that of the first embodiment for carrying out the present invention can be obtained in that the device 7A and the sounding test method 1A using the sounding test device 7A are used. Together are, therefore not affected by the penetration force for having a flat portion 19, it is possible to measure the characteristic values with higher accuracy.

  In the third embodiment for carrying out the present invention shown in FIGS. 9 to 11, the main difference from the first embodiment for carrying out the present invention is that the gradient in the penetration direction is not divided in the horizontal direction. Is a sounding test apparatus 7B using a resistor 3B having a loading unit 6B formed in a spiral shape (spiral shape) so that the angle is 5 degrees or less, and a sounding test method 1B using the sounding test apparatus 7B. Even with such a configuration, the same effect as the first embodiment for carrying out the present invention can be obtained, and the same shape as that obtained by spirally grooving the elliptical inverted truncated cone rotating body can be obtained. By attaching a cutting blade to the tip, it is possible to easily perform excavation penetration by rotation.

  For this reason, the earth is removed and penetrated at the same time simply by rotating it, the measuring instrument is eliminated from the rotating resistor, and the torque ratio is measured with a ground input meter, depth meter and torque meter (not shown). The relational expression for estimating the liquefaction strength and the like from the correlation with Tr can be derived to obtain the estimated liquefaction strength in the depth direction of the measurement target ground.

  The fourth embodiment for carrying out the present invention shown in FIGS. 12 to 14 is mainly different from the first embodiment for carrying out the present invention in that an elliptical load having a different short radius is used. The sounding test apparatus 7C using the resistor 3C including the unit 6C and the sounding test method 1C using the sounding test apparatus 7C are used, and the first embodiment for carrying out the present invention is also provided with such a configuration. The effect similar to that of the above embodiment can be obtained, and a repeated loading test with both amplitude displacement control can be performed.

  In the present invention, it is important to obtain ground information necessary for the design of earth structures, earth and sand slopes, various foundations, etc. at the time of an earthquake, in particular, ground property values for external forces that repeatedly act such as earthquakes. The ground is deposited or created in various environments and lacks uniformity. For this reason, it is desired to conduct surveys at as many points as possible in a continuous and depth direction using a simple and speedy method. The present invention is not a high-precision survey at a small number of points but a response to such social demands, and is used in industries that perform sounding tests.

1, 1A, 1B, 1C: Sounding test method,
2: Rod, 3, 3A, 3B, 3C: Resistor,
4: Ground, 5: Cutting shoe,
6, 6A, 6B, 6C: loading unit,
7, 7A, 7B, 7C: Sounding test apparatus,
8: Load transmission tube, 9: Torque transmission plate,
10: Torque transmission plate fixing screw, 11: Torque transmission plate fixing anchor,
12: Elastic packing, 13: Cable path,
14: protection unit, 15: load transmission gate-type support,
16: Ridge line, 17: Ground pressure gauge,
18: Pore water pressure gauge, 19: Flat part,
20: Inclined surface.

Claims (8)

It is a sounding test method in which a hollow resistor provided with a cutting shoe is connected to the tip of the rod, and this is penetrated into the ground to measure the resistance at a measurement depth to examine the properties of the soil layer in the depth direction. The hollow resistor has an elliptical shape in which a cross-sectional shape cut by a horizontal plane at an upper end has a major axis diameter larger than the cutting shoe diameter and a minor axis diameter equal to or smaller than the cutting shoe diameter, and a major axis A loading unit with a slope of 5 degrees or less that connects the tops of the top and the horizontal resistance loading test is performed by either rotating the hollow resistor while penetrating into the ground or rotating after penetrating. A sounding test method for determining the dynamic characteristic value of the ground by measuring the rotational resistance torque generated in the load unit described above. In addition to the rotational resistance generated in the loading unit provided in the hollow resistor, the ground contact pressure, pore water pressure and shear stress at the top of the elliptical long axis are measured to determine the dynamic characteristic value of the ground. Item 2. The sounding test method according to Item 1. The lower end of the short axis diameter of the hollow resistor has the same diameter as the cutting shoe, the upper part has a gentle gradient of 1 to 2 degrees outward, and the long axis diameter has a steeper slope than this. Rotate after measuring the static strength and deformation coefficient of the ground by non-rotating penetration of a hollow resistor with a ground pressure gauge, pore water pressure gauge and shear stress gauge attached to the loading unit on the short axis diameter surface. The sounding test method according to claim 1, wherein a lateral loading test is performed. It is a sounding test device that connects a hollow resistor with a cutting shoe to the tip of the rod, penetrates it into the ground, measures the resistance at the measurement depth, and examines the properties of the soil layer in the depth direction, The hollow resistor is composed of a load transmission tube that transmits the innermost load, and a loading unit that is provided on the outer periphery of the load transmission tube via a torque transmission plate. The cross-sectional shape cut at the horizontal plane of the part is an ellipse having a major axis diameter larger than the cutting shoe diameter and a minor axis diameter equal to or smaller than the cutting shoe diameter, and in the penetration direction connecting the vertices of the major axes. A sounding test apparatus having a gradient of 5 degrees or less. The sounding test apparatus according to claim 4, wherein the load unit includes a plurality of load units divided in a direction perpendicular to the penetration direction. Each of the plurality of loading units has a flat portion parallel to the penetration direction and a gradient portion provided at a lower portion of the flat portion, and the gradient of the penetration direction as a whole of the plurality of loading units is 5 degrees or less. The sounding test apparatus according to claim 5, wherein The sounding test apparatus according to claim 4, wherein the load unit is formed in a spiral shape so that a gradient in an intrusion direction is 5 degrees or less. The lower end surface of the short axis diameter of the load unit described above is the same diameter as the cutting shoe, the upper part has a gentle gradient of 1 to 2 degrees on the outside, the long axis diameter forms a steeper slope than this, and the elliptical inverted frustum The sounding test apparatus according to any one of claims 4 to 7, wherein a ground pressure gauge, a pore water pressure gauge, and a shear stress gauge are mounted on the short axis diameter surface.

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