JP2003129458A - Method and device for testing liquefaction and dynamic property of ground in situ by utilizing borehole - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method and a device for testing the liquefaction and dynamic properties of ground in situ by utilizing a borehole, which can provide dynamic deformation properties with respect to a repeated load on a soil layer in an arbitrary position in the ground by using the simple method. SOLUTION: The repeated load is imposed on a test object soil layer of a hole wall of the borehole 100 which is provided in the ground, so that displacement of the hole wall can be measured. In particular, this method and this device are characterized in that the repeated load is imposed alternately on a plurality of areas J1 and J3 in the direction of a hole axis, so that a shear force in a direction crossing the hole axis can be made to act on an intermediate soil layer J2 in an alternately repeated manner. Additionally, a static load is imposed on the soil layer J2 in which a repeat test is performed, so that strength can be measured.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to liquefaction and dynamics of a ground using a boring hole for inspecting the in-situ characteristics of the ground when a repeated load such as an earthquake load, a traffic load and a mechanical load is applied. The present invention relates to a characteristic (strength, deformation characteristic) test method and a test device.

[0002]

2. Description of the Related Art In the conventional ground inspection, a boring is carried out to a predetermined depth, a detection sonde as a measuring cell is lowered in the boring hole, the detection sonde is inflated, and a horizontal load is applied to the hole wall. It was designed to detect the static strength and deformation characteristics of the ground from the displacement of the wall.

[0003]

However, in the conventional ground inspection, only static characteristics are detected, and the strength and deformation characteristics of the ground against repeated loads such as earthquake load, traffic load, mechanical load, etc. It was not possible to evaluate the dynamic properties. In the event of an earthquake, even if the force applied to the ground does not cause static damage, it is considered that the strain gradually or suddenly increases, leading to damage.
It is very important to investigate the characteristics of the ground against cyclic loading. At the time of an earthquake, it is considered that complicated forces act in the ground horizontally, vertically and in the torsional direction.
Although it is extremely important to know the in-situ dynamic characteristics of the ground when such complex forces act, it has heretofore been established to measure and evaluate in-situ ground. Not not.

As a conventional liquefaction determination method, for example, a method of determining the characteristic tendency of the whole ground (Japanese Patent Laid-Open No. 7-3
No. 760), a device that detects liquefaction when an earthquake occurs (see Japanese Patent Laid-Open No. 7-109725), but none of them directly tests the dynamic characteristics of the soil layer itself in the ground. It was

As a method of knowing the dynamic characteristics of the soil layer itself against repeated loading, at present, a soil sample is sampled in an undisturbed state by boring, and this is brought into a test room for soil testing. Looking for. However, not only is it very difficult to collect the sample without disturbing it (as it is naturally deposited), but the sample is not under the pressure of the underground. It is impossible to obtain the characteristics of the natural state of. In addition, it is not possible to sample in an undisturbed state in the case of an extremely tight sand layer or a soil layer mixed with gravel, a soil layer with a large particle size such as gravel, or weathered rock or soft rock. Soil tests are not possible. From the above, under the present circumstances, it is the actual situation that only the characteristics under very limited conditions can be directly obtained.

The present invention has been made in view of the importance of directly knowing the dynamic deformation characteristics of the ground with respect to the repeated load, and the purpose thereof is to require a soil sample in an undisturbed state. Providing in-situ ground liquefaction and dynamic property test method and test equipment that uses boring holes that can obtain in-situ dynamic strength and deformation characteristics in a simple method without performing To do.

[0007]

In order to achieve the above object, the method for in-situ liquefaction and dynamic characteristic test of the ground using the boring hole according to the present invention is a hole wall of the boring hole provided in the ground. It is characterized in that the soil dynamics of the ground are determined by repeatedly applying a load to the soil layer under test and measuring the displacement of the hole wall. In particular, you can learn about liquefaction of the ground. Here, the term “repeated load” means to include the entire load that fluctuates periodically, and includes a fluctuating load (vibration) having a relatively high frequency to a slowly fluctuating load that can be manually operated. The dynamic characteristic is the relationship between the load and the displacement when a repeated load is applied. For example, the deformation characteristics are grasped from the relationship between the magnitude of the repeated load, the number of repetitions and the displacement, and the strength such as the yield load and the fracture load. The dynamic characteristics of the soil layer can be evaluated by calculating the deformation coefficient and the systematic analysis of these results.

In particular, it is effective to repeatedly and repeatedly apply a compressive load to a plurality of regions in the hole axial direction of the hole wall of the ball ring hole. By doing so, it becomes possible to alternately apply sway and shearing force in the direction intersecting the hole axis to the intermediate soil layer in the area where the load is applied, and to apply the same force to the soil layer as when an earthquake occurred. Can be added. The intermediate soil layer that has been repeatedly tested is the most damaged part, and if you apply a static compressive load to this part and measure the static strength, you can see how much damage has been received. be able to. In addition, vibration or repeated load is alternately applied to one area of the hole wall of the boring hole,
It is also possible to know the dynamic characteristics of the ground from the relationship between the magnitude of cyclic loading, vibration or the number of cycles and displacement. Repeated loads are three loads: a compressive load loaded in the direction orthogonal to the hole axis, a torsional shear load loaded in the rotational direction around the hole axis, and a shear load loaded in the direction parallel to the hole axis. One of the above, or a combined load in which at least two types of loads are combined.

The in-situ liquefaction and dynamic characteristic testing device using the boring hole of the present invention is a device for inserting into the boring hole provided in the ground and pressing the hole wall by the pressure of the pressure medium. Cell, a pressure adjusting means capable of periodically varying the pressure of the pressure medium in the measuring cell, and a displacement detecting means for detecting the displacement of the hole wall. Characterize. The measuring cell has a plurality of pressurizing portions that press the hole wall along the hole axial direction of the boring hole, and the pressure adjusting means alternately and repeatedly applies pressure to the plurality of pressurizing portions. The measurement cell is divided into a plurality of chambers to form a pressurizing unit, and the pressure adjusting outlet applies pressure repeatedly to the pressure medium in the plurality of chambers alternately. The pressure adjusting means alternately applies pressure to the upper and lower chambers with the intermediate chamber separated,
Static pressure is applied to the intermediate chamber. Torque generating means for repeatedly applying a load to the measuring cell around the hole axis in a state where the measuring cell is in close contact with the hole wall, and displacement detecting means for detecting a rotational displacement of the hole wall due to the repeated load applied by the torque generating means. And are provided. Shear load generating means for repeatedly applying a load to the measuring cell in the direction parallel to the hole axis in a state where the measuring cell is in close contact with the hole wall, and displacement detecting means for detecting the axial displacement of the hole wall due to the shear load, It is characterized by having.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described below based on the illustrated embodiments. Embodiment 1 FIG. 1 (A) is a schematic diagram of a ground liquefaction and dynamic characteristic test device according to Embodiment 1 of the present invention. This liquefaction and dynamic characteristic test device for ground is inserted into a boring hole 100 provided in the ground, and water 3 as a pressure medium is used.
A rubber sonde 1 as a measuring cell filled with a liquid such as the above, a pressure control valve 5 as a pressure adjusting means for periodically varying the pressure of the water 3 in the rubber sonde 1, and a rubber sonde 1
And a displacement sensor 8 as a displacement detecting means for detecting the displacement of the hole wall due to the pressure from.

In the illustrated example, the water 3 is stored in the water tank 2 on the ground, and the head space in the water tank 2 is supplied with high-pressure gas from the pressure supply unit 4 to pressurize the water 3 in the water tank 2. The pressure control valve 5 controls the pressure of this high-pressure gas. In some cases, instead of controlling the high-pressure gas, the water pressure may be directly adjusted. Further, the water tank 2 and the rubber sonde 1 are connected by a connecting pipe 6, and the displacement sensor 8 detects the liquid level of the water tank 2 and the displacement of the hole wall is obtained from the liquid level height. The displacement detecting means is not limited to the displacement sensor 8 and may be visually measured by a scale provided on the water tank.

The rubber sonde 1 is fixed in the vertical direction and expands and contracts only in the horizontal direction.
It is provided with a hollow flexible member such as a rubber tube that comes into close contact with the hole wall of No. 0. The pressure supply unit 4 includes, for example, a pressure source such as high-pressure nitrogen gas, and a regulator valve that keeps the gas pressure supplied from the pressure source constant. A compressor or the like can be used as the pressure source instead of the high pressure gas.

A servo valve is used as the pressure control valve 5, and as shown in FIG. 1 (B), the pressure can be controlled according to a command signal, and as shown in FIG. The valve drive unit 51 of the pressure control valve 5 is controlled on the basis of a control signal from the computer 7 programmed so that the pressure fluctuates in a cycle of, and the output pressure is cyclically changed by changing the opening of the valve, for example. Change. The output pressure is detected by the pressure sensor 52, fed back to the servo amplifier 53, and controlled so as to accurately follow the command signal.

Next, a test procedure by the above test device will be described. In principle, the expected yield load or non-liquefaction limit load (Pl) is loaded in several stages, and a repeated load of plus α is repeated for each load to measure the amount of ground displacement. Hereinafter, similarly, the load is increased and the test is continued until the ground is destroyed, and the dynamic characteristics are obtained from the relationship between the magnitude of the repeated load and the displacement amount. In the example shown,
The repeated load is a sine wave, but the waveform is not limited, and an impact load may be applied. The vibration of the repeated load or the number of repetitions is set considering the vibration of the earthquake or the number of repetitions.
It is suitable to set to about 5 [Hz], preferably about 1 to 2 [Hz]. In the second embodiment, the yield load Py, the breaking load Pl, and the deformation coefficient are obtained as dynamic characteristic indexes.

A specific test procedure will be described below. Test settings Lower the rubber sonde 1 to the soil layer to be tested in the boring hole 100, and inflate the rubber sonde 1 with static pressure (pressure without disturbing elements) until the rubber sonde 1 comes into close contact with the hole wall and the displacement stabilizes. The initial pressure P0 is the pressure at which the displacement becomes stable. The expected breaking load or non-liquefaction limit load Pl is set, the differential pressure from the initial pressure P0 is divided into N stages, the load increment (ΔP) = (Pl-P0) / N is determined, and at each load stage, The test is repeated by applying a load n times or for a fixed time Tn. The expected breaking load or non-liquefaction limit load may be set high or low depending on the purpose of the test, and is set arbitrarily as needed. For example, in the case of an important ground test, the cost should be estimated high. The non-liquefaction limit load means a load that is expected not to be liquefied even if a further load is applied, and is judged according to the ground. It is possible to set variously the number of times and the time for loading the repeated load.
It is decided by considering the shaking time during an earthquake.
In this example, the load stage is 10 and the repeated load is 2
Tested 0 times or 20 seconds as a limit. This is because the shaking during an earthquake is about 20 seconds, and if it is about this, the characteristics of the ground at the time of the earthquake can be grasped, and if it is more than that, the test time becomes too long.

First load stage First, the repeated load (P0 to P0 + α) stage is loaded 20 times or 20 seconds, and the displacement amount of each is read. It is preferable that α of the repeated load is in a range not exceeding ΔP, and it is preferable that α is substantially equal to ΔP.

After the k-th load stage, the load is increased stepwise and the test is repeated. For example, in the case of the kth load stage, the load (Pk) is increased to (P0 + (k-1) * ΔP), and the repeated load (Pk + α) is applied 20 times or 20 seconds to measure the displacement. The data measured in this way is shown in FIG.
It is graphed as shown as a model in (B). This graph shows the final displacements r1, r2, r3 ... At each load stage. In the case of the present embodiment, the data read by the pressure sensor is read by the computer, the data is automatically processed, and the yield load Py and the breaking load Pl are set.
And the deformation coefficient is calculated. When viewed in a graph, the deformation coefficient is the gradient of the straight line portion up to the yield load Py.

The displacement amount r increases as the number of repetitions n increases, and the strength and dynamic deformation characteristics of the ground can be known by systematically analyzing these results. That is,
It is possible to judge whether or not liquefaction is likely to occur while comparing the test results of various soil types. In the case of sandy ground, it is presumed that it will be rapidly destroyed and that the relationship between load and displacement will suddenly fall to the extreme state. The degree of liquefaction can be judged by observing the degree of this rapid change. In addition, in the case of clayey ground, it is expected that the process of falling into the extreme state will take place rather slowly. By observing this tendency, it is possible to judge the degree of dynamic characteristics. In addition, the limit state appears earlier in soil that has a property of rapidly lowering its strength when subjected to a dynamic repetitive load, and it becomes possible to determine the degree of strength reduction.

Attention is always paid to the change in the displacement of the point of interest during the measurement, and the time when the change suddenly starts to be recorded from the proportional change. The measurement is ended with the yield state when the displacement changes abruptly, or the breaking load is confirmed and ended. After returning the pressure of the rubber sonde 1 to P0 or less, pull up the rubber sonde 1. Pay attention to the resistance when pulling up. If it is difficult to pull out, there is a possibility that the holes have collapsed due to liquefaction. In the above embodiment, the relationship between the load and the displacement is plotted as a graph.
As shown in (A) to (D), it is also possible to evaluate the characteristics with respect to vibration or the number of repetitions by graphing the relationship between the number of repetitions n and the displacement r at each load stage. This graph is a plot of the peak value of displacement (corresponding to each peak value of repeated load) with respect to repeated load at each load stage. Each time a repeated load is applied, strain is gradually accumulated in the soil layer and the displacement increases. Figure 7
The degrees of displacement increase (gradients in the graph) of the first, second, and third stages of (A) to (C) are equal, and the displacement gradients become large in the yield stage (FIG. 7D). At the stage when the soil layer is destroyed, the displacement changes rapidly as shown in FIG. By taking such data, it is possible to know the strength and dynamic deformation characteristics of each soil layer under repeated load. Further, the relationship between the time to apply the load and the displacement may be graphed to evaluate the characteristics, and various characteristics can be obtained as necessary.

In the first embodiment, the repetitive load is a compressive load applied to the hole wall in a direction (horizontal direction) orthogonal to the hole axis, but the repetitive load is the hole axis to the hole wall. It may be a torsional shear load that is applied in the rotational direction around the center, or a shear load that is applied to the hole wall in a direction parallel to the hole axis. For example,
When performing the torsional shear vibration test, as shown in FIG. 1, basically, the measurement cell 1 of the above-described embodiment is repeatedly loaded around the hole axis in the state in which the measurement cell 1 is brought into close contact with the hole wall. Torque generating device 9 for applying
The displacement detector 10 as a displacement detector that detects the rotational displacement of the hole wall due to the repeated load applied by

When performing a shear vibration test, a shear load generator for applying a shear load to the measurement cell 1 in the direction parallel to the hole axis while the measurement cell 1 is in close contact with the hole wall. 11 and a displacement detecting section 1 as a displacement detecting means for detecting the axial displacement of the hole wall due to the shear load.
2 may be provided. Although various configurations are possible for the torque generator 9 and the shear load generator 11, a device using fluid pressure such as hydraulic pressure or pneumatic pressure is preferable, and an actuator using hydraulic pressure or pneumatic pressure, a servo valve, etc. Hydraulic pressure or pneumatic control valve.

Second Embodiment Next, a second embodiment of the present invention will be described. FIG. 3 shows a schematic configuration of a test apparatus to which the in-situ ground liquefaction and dynamic characteristic test method using the boring hole of the present invention is applied. In the first embodiment, the rubber sonde was used to repeat the test on one soil layer, but in the second embodiment, upper and lower soil layers J1 and J3 are used.
Is alternately and repeatedly applied to apply a shearing force above and below the immovable intermediate soil layer J2. That is, a plurality of pressurizing parts inserted into the boring hole 100 and divided into three chambers of first, second and third chambers 111, 112 and 113 in the axial direction of the hole and filled with a liquid such as water as a pressure medium. A rubber probe 110 as a measuring cell equipped with
The first chamber 111 that constitutes the pressurizing unit of the rubber sonde 110
And the pressure in the water in the third chamber 113 is alternately applied to expand the water.
It is provided with first and third pressure adjusting parts 121 and 123 for contracting, and a pressure adjusting part 122 for adjusting the water pressure in the second chamber 112.

As shown in FIGS. 4 and 5, the rubber sonde 110 has a cylindrical main body 114 and a tubular rubber member 11 which is a flexible member attached to the outer periphery of the main body 114.
It is composed of 5 and. The rubber member 115 is
The entire length of the second and third chambers 111, 112, 113 is covered, and the boundary portion between the first chamber 111 and the second chamber 112 and the boundary portion between the second chamber 112 and the third chamber 113 are tightened with the tightening member 116 to form three chambers. The first, second and third chambers 111,
The chambers 112 and 113 may be attached to each chamber, or various structures can be selected. Hereinafter, the rubber member corresponding to the first chamber 111 is 115A, the rubber member corresponding to the second chamber 112 is 115B, and the rubber member corresponding to the third chamber 113 is 115C. These rubber members 115A, 115B,
115C and the first chamber, the second chamber 112, the third chamber 111, 11
The pressure unit is constituted by 3. The length L2 of the intermediate second chamber 112 (rubber member 115B) is substantially equal to the rubber sonde 110.
It is preferable to set the diameter to about D. Second room 1
This is because if the length L2 of the 12 (rubber member 115B) is too narrow, the breakage will start from an early stage, and if it is too wide, the effect will be less likely to occur. Further, the lengths L1 and L3 of the first and third chambers 111 and 113 (rubber members 115A and 115C) are preferably 1.5 to 2.5 times D, and optimally about 2 times. Further, D is preferably set to about 5 cm to 20 cm. Of course, the size is not limited to this size. With this size, the rubber member 1
The rubber members 115A and 115C corresponding to 111 and 113 in the first and third chambers 15 swell in a spherical shape, and a force is applied to the intermediate soil layer J2 in a direction of vertically compressing.

The first and third pressure adjusting portions 121 and 123 are
It is provided with a high-pressure gas cylinder 120A as a pressure source, a gas tank 120B that stores a constant amount of gas supplied from the gas cylinder 120A, and hydraulic cylinders 121C and 123C that operate at the pressure from the gas tank 120B. Gas tank 120B and hydraulic cylinder 121
Valves 121E, 1 for releasing pressure between C, 123C
23E and valves 121D and 123D for supplying pressure are provided, and these valves 121D, 121E;
By adjusting D and 123E, the pressure is repeatedly applied to the first and third chambers 111 and 113 of the rubber sonde 110. For example, when the valves 121D and 123D are pressure control valves, and the valves 121E and 123E are closed, the gas pressures supplied to the hydraulic cylinders 121C and 123C are controlled by the valves 121D and 123D, and the pressure cylinders 121C and 123C are used. First and third chamber 11
The load may be alternately applied to 1,113. In FIG. 6, the valves 121D and 123D are described as symbols of manual valves, but various valves such as a pressure control valve electrically controlled are applicable. After the test, the valve 121E,
Open 123E to release the gas pressure from the hydraulic cylinders 121C and 123C. In this example, the pressure medium is water,
The rubber members 115A and 115C expand and contract due to water pressure.

The second pressure adjusting section 122 does not have a hydraulic cylinder, but stores the water 3 in a water tank 122C on the ground,
Gas cylinder 12 in the head space in the water tank 122C
The high-pressure gas is supplied from 2A to pressurize the water in the water tank 122C, and the pressure control valve 122D controls the pressure of the high-pressure gas. However, the first and third pressure adjusting units 1
A hydraulic cylinder may be used as in the case of 21 and 123. The hydraulic cylinder 121C and the first chamber 111 of the rubber sonde 110
Is a first passage 131, and the water tank 120C and the second chamber 112 are a second passage 132.
C and the third chamber 113 are communicated with each other by a third passage 133. These first, second and third passages 131, 132, 1
33 is provided on the boring rod 140 to which the rubber sonde 110 is attached.

Further, the first chamber 111 of the rubber sonde 110,
As displacement detection means for detecting the displacement of the upper soil layer J1 and the lower soil layer J3 compressed by the third chamber 113, the hydraulic cylinders 121C, 123D are provided with displacement sensors 151, 152 for detecting the displacement of the piston. . From the displacement of this piston, the rubber member 115A of the rubber sonde 110,
The displacement amount of 115C, that is, the displacement of the hole wall is measured.
Further, as a displacement detecting means for detecting the displacement of the intermediate soil layer J2 compressed by the second chamber 112 of the rubber sonde 110, the displacement sensor 15 detects the change of the water level in the water tank 122C.
3 is provided. From the displacement of this water level, the second chamber 11
The displacement amount of the second rubber member 115B, that is, the displacement of the hole wall is measured. Further, a pore water pressure gauge 150 for verifying the occurrence of liquefaction is provided at the lower end of the rubber sonde 110. The pore water pressure gauge 150 may be provided on the side surface of the cell, but since the water pressure may not be measured due to the clay film on the hole wall, the lower end 110 as shown in FIG. 3 (B).
It is preferable to provide it on the C surface side. In addition, the lower end surface 110
Since the rubber sonde 110 may be scraped by the sonde 110 and adhere to the soil while the rubber sonde 110 is being lowered into the boring hole 100, it is desirable to attach the rubber sonde 110 to the inner part of the recess 110D on the lower end surface.

Next, a test method for the second embodiment will be described with reference to FIG. In the test, load is alternately applied to the upper and lower soil layers J1 and J3, the displacement is measured in real time, and then the static load test of the intermediate soil layer J2 is performed to measure the static strength. The loading test itself of the repeated load on the soil layers J1 and J3 of the upper and lower stages is exactly the same as that of the first embodiment, and the expected yield load or non-liquefaction limit load (Pl) is divided into N stages and loaded. Then, for each load, plus α repeated load n times or for a predetermined time T
The displacement amount r of the ground is measured over n, and the static strength of the intermediate soil layer J2 is measured for each cyclic load loading at each stage.

The specific test procedure will be described below. The boring hole 100 is excavated to the depth of the formation to be inspected, the rubber sonde 110 is inserted by the boring rod 140 to a predetermined depth position in the boring hole 100, and the test is performed in the following procedure. Test Settings Pressure is supplied to the second chamber 112 of the rubber sonde 110, a static compressive load is applied to the intermediate soil layer J2, and the initial strength of the intermediate soil layer J2 is measured. Specifically, the "load P-displacement r curve" in a static state is obtained. At this point, rubber sonde 1
The initial pressure P0 is calculated so that is closely attached to the hole wall and the displacement is stable. Pl for the expected breaking load or non-liquefaction limit load
Then, the differential pressure from the initial pressure P0 is divided into N stages, the load increment (ΔP) = (Pl−P0) / N is determined, and the rubber sonde 11
A test is repeatedly applied to the first chamber 111 and the third chamber 113 of 0 times at each load stage n times or alternately for a predetermined time Tn. Before the repeated test, the first chamber 1 of the rubber sonde 110
11. The initial pressure P0 is applied to the third chamber 113 in advance.

First Loading Stage In the first loading stage, the first chamber 111 and the third chamber 113 are
Repeated loads of P0 to P0 + α are alternately loaded n times, the displacements of the upper soil layer J1 and the lower soil layer J3 corresponding to the first chamber 111 and the third chamber 113 are measured, and the same as in the first embodiment. The relationship between load and displacement is monitored in real time and the data is stored in a computer and graphed. Also in this case, the load stage is 10 stages, and the repeated load is limited to 20 times or 20 seconds. The loading load in this case is
It is assumed that the shock load has a sharp rise as shown in FIG. After the shock load rises rapidly, the t0 load is maintained for a certain period of time to reliably compress the soil layer, and then the load decreases. The loads are alternately applied so that when one of the first chamber 111 and the third chamber 113 is loaded, the other is not loaded. Although the load start time is before the load rises to the other chamber, it may be at the same time as the load rise to the other chamber as described by the dotted line.
A shearing force acts on the upper and lower end portions of the upper soil layer J1 and the upper and lower end portions of the lower soil layer J3 together with compression, and particularly, the intermediate soil layer J
For No. 2, since the upper and lower soil layers J1 and J3 are alternately compressed, shearing force acts while shaking (Fig. 3
(X) in (A) to (C)), damage similar to that during an earthquake is applied to the soil layer. The shape of the rubber probe 110 is the second chamber 1
Since the length L2 of 12 is about the diameter D of the rubber sonde 110, the phenomenon leading to the destruction can be appropriately captured, and the lengths L1 and L3 of the first and third chambers 111 and 113 are D.
It is about twice as large as the rubber member 115A, 11A.
Since 5C expands in a spherical shape, the displacement becomes large, and the component force of the compressive force directly acts on the intermediate soil layer J2, so that the influence of the load on the soil layer can be increased. After the repeated load test, the pressure is supplied to the second chamber J2 again to apply a static compressive load to the intermediate soil layer J2,
The intensity measurement of 2 is performed to obtain data on how much the initial intensity is decreased. This cycle is set as one cycle, and the load is sequentially increased for each ΔP, and the test is repeated, basically until the soil layer is destroyed. FIG. 8 shows a test result model of the static strength test of the intermediate soil layer J2. 8A is a graph in which the vertical axis represents the static load P applied to the intermediate soil layer J2 and the horizontal axis represents time. FIG. 8B shows the displacement of the intermediate soil layer J2 in which the vertical axis is loaded. 6 is a graph in which r is the time and the horizontal axis is time. 8C to 8F are graphs showing the relationship between the load and displacement of the intermediate soil layer J2 at each stage shown in FIGS. 8A and 8B. FIG. 8 (A),
As shown in (B), first, the initial strength of the intermediate soil layer before the repeated test is measured. Second of rubber sonde 110
Until the rubber member 115B of the chamber 112 comes into close contact with the hole wall of the boring hole 100, the pressure does not rise and only the displacement increases. When the rubber member 115B comes into close contact with the hole wall, the pressure sharply increases, and conversely, the change in the displacement becomes small and becomes small. The pressure reaches P0, and the change in displacement with respect to the load stabilizes. The load is P0 in this stable area.
The displacement is detected by increasing to + δ, and as shown in FIG. 8C, a load-displacement curve (horizontal axis is load, vertical axis is displacement) of the intermediate soil layer at the initial stage is created. The gradient of this load-displacement curve is used as the deformation coefficient. After the measurement, the load is returned to P0 (0). Even if the load is returned to P0, the permanent strain remains in the intermediate soil layer J2, so the displacement does not return to the original. The magnitude of the pressure increment δ is set to about a fraction of the amplitude of the repeated load applied to the upper and lower soil layers J1 and J3, as long as the relationship between the load and the displacement can be understood. Next, after performing the first repeated test on the upper and lower soil layers J1 and J3, the static strength test of the intermediate soil layer J1 is performed. Even if pressure is applied, the load P0 does not increase until the rubber member 115B of the rubber sonde expands by the amount of the permanent strain at the time of measuring the initial pressure, and only the displacement increases.
When the permanent strain is absorbed, the pressure sharply increases, conversely the change in displacement becomes small and reaches the test start load P0 (1), and in this stable region the load is increased to P0 (1) + δ Is detected, a load-displacement curve of the intermediate soil layer after the first repeated test is created (see FIG. 8D), and the gradient of the graph is used as the deformation coefficient. After the measurement, the load is returned to the test start load P0 (1). Even if the load is returned to P0 (1),
Since the permanent strain remains in the intermediate soil layer J2, the displacement does not return to the displacement at the start of the test. Below, similarly, upper and lower soil layers J1, J
After the repeated test of 3, the static strength test of the intermediate soil layer J2 is performed. In the elastic region, the deformation coefficients obtained from the load-displacement curve are almost equal. When the intermediate soil layer J2 is in a yield state after a number of repeated tests (k times), first, the test start load (P0 (k)) is reached, and then (P0
It takes time for the load to increase up to (k) + δ), and the load does not increase so much and the displacement increases greatly.
The load-displacement curve at this time has a steep slope (Fig. 8 (E)).
reference). Furthermore, when the intermediate soil layer J2 is destroyed (m-th time, it is described as the next stage of the yield stage in the figure), the load decreases with the breaking load Pl as the peak and drops to a certain pressure such as groundwater pressure. It will be constant at that point. The displacement increases rapidly near the breaking load (Fig. 8 (B)), and the load-
As shown in FIG. 8F, the displacement curve has a graph shape in which the displacement further increases even when the pressure decreases.

By combining the displacement data of the upper and lower soil layers J1 and J3 with respect to the repeated load and the displacement data of the intermediate soil layer J2 with respect to the static load, the dynamic deformation characteristics against the repeated load are determined and the yield point is determined. Calculate the strength of the break point. Further, liquefaction of the soil layer is assumed to occur in the intermediate soil layer J2 in which shearing force acts from above and below. When liquefaction occurs, the displacement of the measurement data shown in FIG. I understand that Further, the liquefaction can be verified by the constant pore water pressure measured by the pore water pressure gauge 150, and whether or not the liquefaction has occurred can be double verified. As described above, according to the second embodiment, the shearing force is not changed by the simple alternating load of the compressive load on the upper and lower soil layers without performing the torsional shear test and the axial shear test as in the first embodiment. Can be added to the intermediate soil layer, and the dynamic characteristic test of the soil layer can be performed with a simple structure, reliably, in a short time, at low cost, and with high accuracy.

In the second embodiment, the rubber sonde is provided with the immovable portion for loading a static load. However, the immobility portion is not provided and only the upper and lower repetitive load loading portions are provided, and only the upper and lower soil layers are deformed. You may pay attention. This is because a shearing force acts on the boundary between the upper and lower soil layers, and if liquefaction occurs, it will spread to the upper and lower soil layers. Further, although the repeated load is set to the upper and lower two steps, it may be set to the upper and lower three steps or more, and in that case, the immovable portion may be provided in the middle of each repeated load loading section.

The repetitive load includes a compressive load applied in the direction orthogonal to the hole axis, a torsional shear load applied in the rotational direction about the hole axis, and a shear load applied in the direction parallel to the hole axis. Each of the three loads can be loaded individually, or a combination of at least two types of loads can be loaded.

In the first and second embodiments, the case where the boring hole 100 is dug vertically has been described as an example, but the present invention is also applicable to the case where the boring hole 100 is dug horizontally or diagonally. Further, as the measuring cell, a piston jack or the like which presses a metal loading plate by hydraulic pressure or the like may be used instead of the rubber sonde 110, 1, and an appropriate measuring cell is selected according to the soil layer. .

[0034]

As described above, according to the present invention,
Since in-situ tests can be performed without taking out underground samples, strength and deformation characteristics of soil layers under natural conditions under repeated loading can be obtained. In particular, it is possible to measure very loose sand layers or soil layers that cannot be sampled due to mixing of gravel, etc., soil layers with large grain size such as gravel layers, weathered rocks, soft rocks, etc. In addition, it is economical because the test can be performed in a short time as compared with the conventional sample test.

Particularly, by repeatedly and repeatedly applying a compressive load to a plurality of regions in the hole axial direction of the hole wall of the ball ring hole, repeated shearing of a shape similar to the actual rolling of the earthquake is carried out at the boundary part of the loading region. A force can be applied, and the property against shearing force can be tested as well as the property against repeated compressive load. Liquefaction is likely to occur due to shearing force, which is effective in determining liquefaction.
When the boundary portion collapses, the liquefaction spreads also in the compressive load loading region, and the displacement changes greatly, so liquefaction can be determined. Further, even when a load is repeatedly applied to one region of the hole wall of the ball ring hole, various ground characteristics can be examined by the data analysis method. In this case, there are three types of compression load, that is, a compressive load that is applied in a direction orthogonal to the hole axis, a torsional shear load that is applied in a rotational direction around the hole axis, and a shear load that is applied in a direction parallel to the hole axis. One of the loads, or a combined load that combines at least two types of loads is loaded and tested to perform an actual repeated load test in which a compression or shear load acts while being twisted. You can

[Brief description of drawings]

FIG. 1 (A) is a diagram showing a schematic configuration of an in-situ liquefaction of ground and a dynamic characteristic testing device using a boring hole according to a first embodiment of the present invention, FIG. 1 (B). FIG. 3 is a diagram showing a control configuration of a pressure control valve.

2 (A) is a diagram showing an output example by the pressure control valve of FIG. 1, and FIG. 2 (B) is a graph showing a model of the test result of FIG. 1.

3 (A) to 3 (E) are explanatory views showing a method for in-situ liquefaction of ground and a dynamic characteristic test method using a boring hole according to a second embodiment of the present invention.

FIG. 4 is a functional explanatory diagram of the rubber probe of FIG. 3.

5 is a schematic configuration diagram of the rubber probe of FIG.

FIG. 6 is an explanatory diagram showing a configuration example of an in-situ liquefaction of ground and a dynamic characteristic testing device using a boring hole according to a second embodiment of the present invention.

FIG. 7 is another graph of the test result model of FIG.

8 (A) to (F) are graphs showing test result models of a static strength test of an intermediate soil layer.

[Explanation of symbols]

1 rubber sonde (measuring cell), 2 water tank (liquid tank), 3 water (liquid), 4 pressure supply unit, 5 pressure control valve, 6 connecting pipe, 7 computer, 9 torque generator, 10 displacement detection unit, 11 Shear load generator, 12 Displacement detecting section 100 Boring hole 110 Rubber sondes 111, 112, 113 First, second and third chambers 121, 122, 123 First, second and third pressure adjusting section 114 Main body section, 115 Rubber Member, 116 Tightening member 120A Gas cylinder, 120B Gas tank 121C, 123C Hydraulic cylinder 121D, 123D Valve 121E, 123E Valve 122C Water tank 122C, 122D Pressure control valve J1 Upper soil layer, J2 Intermediate soil layer, J3 Lower soil layer 150 Pore pressure gauge

Claims (10)

[Claims] 1. A boring hole characterized in that the dynamic characteristics of the ground are obtained by repeatedly applying a load to the soil layer to be tested on the hole wall of the boring hole provided in the ground and measuring the displacement of the hole wall. In-situ ground liquefaction and dynamic property test method. 2. A shear force in a direction intersecting with the hole axis is alternately applied to an intermediate soil layer in the load-loaded area by alternately and repeatedly applying a load to a plurality of areas in the hole axis direction of the hole wall of the boring hole. 2. It is made to act repeatedly, Claim 1 characterized by the above-mentioned.
In-situ liquefaction and dynamic property test method using in-situ boring holes. 3. A method for in-situ liquefaction and dynamic property test of an in-situ ground using a boring hole according to claim 2, wherein a static load is applied to the intermediate soil layer subjected to the repeated test to measure the strength. . 4. A dynamic characteristic of the ground is known from a relation of magnitude of repeated load, vibration or number of repetitions and displacement by alternately applying vibration or repeated load to one region of the hole wall of the boring hole. In-situ liquefaction and dynamic property testing method using in-situ drilling according to 1. 5. The repetitive load includes a compressive load applied in a direction orthogonal to the hole axis, a torsional shear load applied in a rotation direction about the hole axis, and a shear load applied in a direction parallel to the hole axis. Liquefaction and dynamic characteristic test of in-situ ground using a boring hole according to claim 1 or 4, which is one of three loads or a combined load in which at least two types of loads are combined. Method. 6. A measuring cell that is inserted into a boring hole provided in the ground and presses the hole wall by the pressure of the pressure medium, and the pressure of the pressure medium in the measuring cell can be periodically changed. Liquefaction and dynamic characteristic testing device for in-situ ground utilizing a boring hole, which is equipped with a possible pressure adjusting means and a displacement detecting means for detecting the displacement of the hole wall. . 7. The measuring cell is divided into a plurality of chambers that press the hole wall along the hole axis direction of the boring hole, and the pressure adjusting stage applies repeated pressure to the pressure medium in the plurality of chambers alternately. An in-situ liquefaction and dynamic property testing device using the boring hole according to item 6. 8. The original position using a boring hole according to claim 7, wherein the pressure adjusting means alternately and repeatedly applies pressure to the upper and lower chambers with a space between the intermediate chambers and static pressure to the intermediate chambers. Liquefaction and dynamic property test equipment for ground at the ground. 9. A torque generating means for applying a repeated load to the measuring cell around the hole axis in a state where the measuring cell is in close contact with the hole wall, and a rotational displacement of the hole wall due to the repeated load applied by the torque generating means. The in-situ liquefaction and dynamic characteristic testing device using the boring hole according to claim 6, further comprising: a displacement detecting unit that detects the displacement. 10. A shear load generating means for repeatedly applying a load to the measuring cell in a direction parallel to the hole axis in a state where the measuring cell is in close contact with the hole wall, and a displacement for detecting an axial displacement of the hole wall due to the shear load. A liquefaction and dynamic characteristic testing device for in-situ ground utilizing a boring hole according to claim 6 or 9, further comprising: detection means.